JP2008274513A - Coated paper for gravure print - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide coated paper for gravure prints, which has reduced speckles, is good in gravure printing suitability, has an action for decomposing injurious substances with light, in excellent operability. <P>SOLUTION: The coated paper for the gravure prints produced by disposing a coated layer containing a pigment and an adhesive on base paper, contains powdery titanium dioxide having a photocatalystic action in the coated layer in an amount of 1-30 pts.wt. per 100 pts.wt. of the pigment, using, as the powdery titanium dioxide, a mixture of the pigment with the powdery titanium dioxide in a preliminary silica sol or alumina sol wherein the total content of both the substances is 45-60 wt.%, and further containing a copolymer latex in an amount of 1-10 pts.wt. per 100 pts.wt. of the pigment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a coated paper for gravure printing having print quality and an excellent air cleaning effect.

With increasing interest in the living environment, the demand for removal of harmful substances such as bad odors in daily life is increasing, and titanium oxide is attracting attention. Titanium oxide has traditionally been used as a pigment with excellent opacity and whiteness for papermaking, but it also uses light energy to cause oxidation-reduction reactions and decompose various harmful substances in the air. In order to take advantage of this phenomenon, development is being carried on paper. For example, a photocatalytic paper in which a water-soluble polymer and a substance having a photocatalytic action such as titanium oxide are internally added to paper is disclosed (see Patent Document 1), but the photocatalytic substance exhibits its catalytic action when exposed to light. For this reason, it is difficult to say that the method having a photocatalytic substance inside the paper layer is efficient and the effect is not sufficient. In addition, the print quality when color printing such as ink fillability, printing glossiness, and sharpness of printed matter is not sufficient.

Also, a coated paper for printing is disclosed in which a fine powder of titanium oxide is coated with silica sol and coated in a paint (see Patent Document 2). This is a photocatalytic effect imparted to offset printing paper used in the texts of folding flyers, magazines, catalogs and the like.
The titanium oxide includes powder and slurry products. Since titanium oxide having photocatalytic performance has a small particle size, the slurry-like product is inferior in fluidity and remarkably inferior in workability when preparing a paint. In order to improve this fluidity, it is necessary to reduce the solid content concentration of the slurry. In this case, however, the solid content of the final paint is lowered, resulting in poor coating suitability and good coated paper for printing. It cannot be manufactured. In addition, powdered products need to be dispersed in water, but when dispersed at a high concentration, a dispersed slurry having poor fluidity is formed, and when dispersed at a low concentration, undispersed titanium oxide This causes a problem that scratches called streaks derived from the aggregated titanium oxide occur during coating, and that the titanium oxide aggregates to reduce the specific surface area and inferior the photocatalytic performance.
In addition, printing methods for printing paper mainly include an offset printing method and a gravure method. Gravure printing is an intaglio printing method in which the ink in the concave portion of the plate is transferred under pressure and has excellent gradation reproducibility. Therefore, gravure printing paper is preferably used for packaging applications compared to offset printing paper. ing. In addition, these packages are often used in an environment where light is more fully exposed, and therefore, a gravure coated paper imparted with a photocatalytic effect has been desired.

However, even if the conventional technique is used, it is difficult to achieve both good gravure printing suitability and an excellent air cleaning effect. When titanium oxide is added to the paint, the smoothness decreases, and the phenomenon that the halftone dots called speckles do not transfer normally increases or the air cleaning effect may not be exhibited. In gravure printing, when the plate is a hard metal roll compared to offset printing and the plate surface does not completely adhere to the paper at the time of printing, speckles are likely to occur. Decrease. In order to suppress the generation of speckles, it is said that gravure paper is more important to smoothness and cushioning of coated paper than offset paper. This is because if the smoothness is high, the contact with the plate becomes dense, and if the cushioning property is high, the paper is deformed by the printing pressure during printing and the adhesion to the plate is increased. However, when photocatalytic titanium oxide was used to suppress the generation of speckles and to improve the gravure printing suitability, the air cleaning effect was reduced. Moreover, when it was made to have a favorable air cleaning effect, it might be inferior to the gravure suitability by the increase in a speckle.

Japanese Patent Laid-Open No. 10-226983 JP 2006-243453 A

In view of such a situation, an object of the present invention is to provide a gravure coated paper having few speckles and good gravure printing suitability and also having an action of decomposing harmful substances when exposed to light. It is to provide with excellent operability.

As a result of diligent research on the above problems, the present inventors, in a gravure coated paper in which a coating layer containing a pigment and an adhesive is provided on a base paper, is a powder having a photocatalytic action in the coating layer 1 to 30 parts by weight of titanium dioxide per 100 parts by weight of pigment, and the powdered titanium oxide was previously mixed with silica sol or alumina sol in a state where the solid content of both substances was 45 to 60% by weight. Used and contains 1-10 parts by weight of copolymer latex with respect to 100 parts by weight of pigment, resulting in less speckle, good gravure printing surface, and noxious substances when exposed to light It was possible to obtain a coated paper for gravure printing having an action of decomposing the resin, and found a production method having excellent operability. In the present invention, in order to further suppress the deterioration of the printing quality due to the degradation of the paper due to the decomposition reaction of the photocatalyst, the decomposition of the ink components, etc. Is preferably 45 to 60% by weight so that the mixing ratio of titanium oxide to silica sol or alumina sol is 2: 1 to 1: 2. In addition, the powdered titanium oxide is preliminarily mixed with silica sol or alumina sol in a state where the solid content of both substances is 45 to 60% by weight, and then the silica sol or alumina sol has a ratio of titanium oxide to silica sol or alumina sol. It is preferable to further add and mix so as to be 2: 1 to 1: 2.

The base paper preferably contains a light calcium carbonate-silica composite and / or an organic compound having an action of inhibiting interfiber bonding between pulps as a filler. About 1 to 7 parts by weight of a copolymer latex having a glass transition temperature of −50 ° C. to 20 ° C. with respect to 100 parts by weight of the pigment, the adhesive in the coating layer is better with less speckles. The photogravure printability and photocatalytic effect are improved. The PPS roughness of the coated paper is preferably 0.1 to 1.5 μm. Moreover, it is preferable that the primary particle diameter of powdered titanium oxide is 5 to 100 nm and the secondary particle diameter is 300 to 2000 nm.

  According to the present invention, a coated paper for gravure printing that has less speckle, has a good gravure printing surface feeling, and also has an action of decomposing harmful substances when exposed to light is obtained with excellent operability. be able to.

In the present invention, powdered titanium oxide having photocatalytic performance may be used at a specific blending ratio as a part of the pigment blended with the coating liquid in order to impart an air cleaning effect to the coated paper for gravure printing. is important. A compounding rate is 1-30 weight part among 100 weight part of pigments, Preferably it is 1-20 weight part, More preferably, it is 2-10 weight part. When the compounding ratio of titanium oxide is less than 1 part by weight, the amount of the photocatalyst is too small to obtain a sufficient air cleaning effect. In the present invention, it is important to use fine titanium oxide having a high photocatalytic effect. However, fine titanium oxide can be slurried compared to clay and calcium carbonate generally used in the field of coated paper. The solid content concentration is low. For this reason, when blended in excess of 30 parts by weight, an air cleaning effect can be obtained, but since the paint concentration is greatly reduced, it becomes difficult to apply a coating amount of a certain value or more. When compared with the coating amount applied with coated paper, the printed surface feel and surface strength are poor. The powdered titanium oxide used in the present invention includes all titanium oxides or hydroxides called titanium dioxide, hydrated titanium oxide, metatitanic acid, orthotitanic acid, hydrous titanium oxide, and titanium hydroxide. Things can be used. The average particle diameter of preferable secondary particles of titanium oxide is 300 to 2000 nm, more preferably 500 to 1500 nm, and still more preferably 700 to 1300 nm. When the average particle diameter of the secondary particles is less than 300 nm, the dispersibility of the titanium oxide slurry and the fluidity of the coating are poor, so that the productivity is lowered, and the printing quality and printing workability due to the lack of titanium oxide are further lowered. On the other hand, when the average particle diameter of the secondary particles exceeds 2000 nm, the smoothness of the coated paper is lowered and the printing quality is lowered. Moreover, the preferable primary particle diameter of a titanium oxide is 5-100 nm, More preferably, it is 10-50 nm, More preferably, it is 10-35 nm. When the primary particle diameter is less than 5 nm, the dispersibility of the titanium oxide slurry and the fluidity of the coating are liable to deteriorate and the operability is poor. Moreover, since surface area will become small when it exceeds 100 nm, there exists a tendency for photocatalytic performance to be insufficient. The specific surface area of titanium oxide is preferably 10 to 350 m ² / g.

  In the present invention, it is important to previously mix powdered titanium oxide with silica sol or alumina sol in order to impart choking resistance. The term “choking resistance” as used herein refers to resistance to powder falling due to degradation and degradation of the coating layer surface and the base paper layer by photocatalytic reaction after light irradiation. In addition, since powdered titanium oxide has a small particle size, it is important to use a specific dispersion method. The dispersion method is to mix titanium oxide and silica sol or alumina sol in a state where the total solid content of both substances is 45 to 60% by weight, preferably 45 to 55% by weight, more preferably 45 to 50% by weight. It is. By mixing both, titanium oxide and silica sol or alumina sol collide with each other, and a good dispersion state is obtained. When the solid content is less than 45% by weight, the concentration of the slurry is too low, and this collision does not sufficiently occur, and a large amount of agglomerated undispersed titanium oxide is generated, which is called a streak derived from the agglomerated titanium oxide during coating. Scratches are likely to occur, and since titanium oxide is agglomerated, the specific surface area is reduced and the photocatalytic performance is inferior. When it exceeds 60% by weight, the viscosity of the slurry becomes high, the handling during the production of the paint is inferior, and the operability is remarkably deteriorated. Moreover, dispersibility and photocatalytic ability are excellent by mixing titanium oxide and silica sol or alumina sol for a certain period of time so that the ratio of titanium oxide to silica sol or alumina sol is 2: 1 to 1: 2. Alternatively, even when the ratio of titanium oxide and silica sol or alumina sol becomes 2: 1 to 1: 2 after mixing for a certain period of time with titanium oxide and silica sol or alumina sol, further silica sol or alumina sol is added and mixed to treat titanium oxide. By making the ratio of silica sol or alumina sol 2: 1 to 1: 2, dispersibility and photocatalytic performance are excellent. The fixed time for the first mixing treatment is preferably 20 minutes or more, more preferably 40 minutes or more. Furthermore, the number of times of mixing treatment and the time may be appropriately determined so that the dispersion state becomes good. As a material to be mixed with titanium oxide, silica sol is preferably used from the viewpoint of light transmittance.

In addition, it is preferable to add other pigments and auxiliaries after mixing for a certain period of time in order to efficiently coat the periphery of the fine titanium oxide when adjusting the coating solution.

The pigment used in the present invention is not particularly limited in addition to the above titanium oxide, and light calcium carbonate, heavy calcium carbonate, clay, kaolin, engineered kaolin, delaminated conventionally used for coated paper. Inorganic pigments such as clay, talc, calcium sulfate, titanium dioxide, barium sulfate, zinc oxide, silicic acid, silicate, and satin white used for normal papermaking, and organic pigments such as plastic pigments can be used. The pigments can be used alone or in combination of two or more as required.

Adhesives used in the present invention are conventionally used for coated paper, such as styrene / butadiene, styrene / acrylic, ethylene / vinyl acetate, butadiene / methyl methacrylate, vinyl acetate / butyl acrylate, etc. It is necessary to contain 1 to 10 parts by weight, preferably 1 to 7 parts by weight, more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the pigment as an organic adhesive. is there. When the amount exceeds 10 parts by weight, the mechanism is not well understood. In particular, when the inorganic adhesive of silica sol or alumina sol described above is present, the adhesive and silica react to harden the coating layer, and the gravure This is not preferable because the cushioning properties required at the time of printing are reduced, and the number of misdots increases and the gravure printing aptitude deteriorates. Moreover, when it is less than 1 part by weight, a sufficient surface strength cannot be obtained, which is not preferable. Furthermore, it is preferable that the number of blended parts of the organic adhesive is small in terms of the air cleaning effect. As the latex, a copolymer latex having a glass transition temperature of −50 to 20 ° C. is used, and a latex having a glass transition temperature of −40 ° C. to 0 ° C. is preferably used. As a result, a coating layer having hardness suitable for calendering and cushioning suitable for gravure printing is obtained. That is, since the coating layer formed using the copolymer latex having a glass transition temperature exceeding 20 ° C. becomes hard, speckles at the time of gravure printing increase and it is not suitable for gravure printing. Moreover, when the glass transition temperature is less than −50 ° C., the operability tends to decrease due to stickiness on the calendar roll. For core-shell type latexes having different glass transition temperatures, the glass transition temperature of the shell layer (surface layer) is preferably within the above temperature range. Other organic adhesives include synthetic adhesives such as polyvinyl alcohol, maleic anhydride copolymer, acrylic acid / methyl methacrylate copolymer, proteins such as casein, soy protein, synthetic protein, oxidized starch, cation It can be used in combination with starches such as modified starch, urea phosphate esterified starch, and hydroxyethyl etherified starch, and water-soluble polymer adhesives such as cellulose derivatives such as carboxymethylcellulose, hydroxymethylcellulose, and hydroxyethylcellulose. It is preferable that the water-soluble polymer adhesive such as 5 parts by weight or less, and most preferable is no compounding.
In the coating liquid of the present invention, various commonly used auxiliaries such as dispersants, thickeners, water retention agents, antifoaming agents, water resistance agents, dyes and fluorescent dyes can be used as auxiliaries.

The base paper in the present invention comprises pulp, fillers and various auxiliaries. As pulp, chemical pulp, mechanical pulp, used paper pulp, etc. can be used. A content of 60% by weight or less of the pulp is preferable. From the viewpoint of light resistance and print quality, 100% of the chemical pulp is most preferable.

In the present invention, the filler used for the base paper includes light calcium carbonate, heavy calcium carbonate, light calcium carbonate-silica composite, talc, kaolin, clay, amorphous silicate, amorphous silica, titanium oxide, synthetic resin filler, etc. One or more known fillers can be used. The compounding quantity of a filler is about 1-30 weight% with respect to a pulp weight, Preferably it is 3-20 weight%. Further, by using the light calcium carbonate-silica composite in whole or in part, the gravure printability is improved and a good air cleaning effect is obtained.
In general, when producing a coated paper for gravure printing, it is produced by carrying out a strong calendar process in order to increase the smoothness of the coated paper. However, in the present invention, particularly in the case of a coating layer in which silica sol or the like is used in combination with titanium oxide having photocatalytic activity, a phenomenon that the coating layer becomes hard and speckle increases is observed. In addition, when the coated paper is subjected to a strong calender treatment, the density of the coated paper increases, and the photocatalytic effect may be insufficient. This is probably because the density of the coated paper increases, the voids decrease, and the particles of odor components, bacteria, and the like cannot be contacted efficiently, and the photocatalytic effect is reduced.

The light calcium carbonate-silica composite used in the present invention is a particle having the characteristics of being excellent in the effect of reducing the density of paper, having a large oil absorption amount and improving the opacity. Moreover, even after performing the calendar process, it is possible to maintain contradictory properties such as maintaining a low density and high smoothness. 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, thereby reducing the density of the coated paper and increasing the voids. It is considered that the photocatalytic effect is improved by the presence of. Also, when the coating layer becomes hard, the coating layer is pushed in by the gaps in the coating base paper, thereby improving the adhesion to the roll surface during gravure printing, reducing speckles and improving gravure printing suitability. It seems to be.
In the present invention, the light calcium carbonate-silica composite is 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. When the filler in the paper is less than 1% by weight, the photocatalytic effect and the gravure printability are not sufficient, and when it exceeds 25% by weight, the strength is not sufficient, and the paper may be cut off during printing. Absent. In addition, a light calcium carbonate-silica composite in which the surface of light calcium carbonate particles is coated with silica is a combination of light calcium carbonate and silica in order to improve the balance of photocatalytic effect, gravure printability, rigidity, and opacity. The solid content weight ratio is preferably light calcium carbonate / silica = 30/70 to 70/30. The light 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 a rosetta-type calcite-type light calcium carbonate is used, a light calcium carbonate-silica composite having a particularly high bulk and high opacity improvement effect can be obtained. The rosetta type refers to a shape in which spindle-shaped light calcium carbonate primary particles are aggregated in a chestnut shape, and is characterized by a higher specific surface area and oil absorption than other light calcium carbonates.
Further, in the base paper of the present invention, by using a bulking agent (a low density agent) such as a surfactant which is an organic compound having an action of inhibiting the interfiber binding of pulp, it has a photocatalytic effect. Speckle is reduced, and gravure printing aptitude is improved. Especially when titanium oxide and silica sol are used in combination, the gravure aptitude is improved.

The reason is considered as follows. The bulking agent or the low-density agent as a binding inhibitor decreases the density of the paper by adding it, but the gravure paper is obtained as a result of supercalendering to obtain high smoothness. Is less likely to be bulky or low density. However, the binding inhibitor compound breaks part of the fiber bond and improves fiber slipping, so that the fiber moves according to the pressure during super calendering, and the coated paper surface becomes the roll surface. As a result, the surface smoothness after the calendar treatment is increased, and the glossiness of the white paper and the suitability for gravure printing are expected to increase. Although printing pressure is also applied during gravure printing, it is presumed that the ink moves on the intaglio and the speckle is improved as a result of the fibers moving in conformity with the pressure and the paper being easily adhered to the plate. In the present invention, when a hard coating layer is provided as a coating layer in which titanium oxide and silica sol are used in combination, speckles are reduced and gravure printing suitability is improved.
An organic compound (hereinafter abbreviated as a binding inhibitor) that has an action of inhibiting the interfiber bonding of pulp contained in the base paper is a compound having a hydrophobic group and a hydrophilic group. Therefore, the density reducing agent (or bulking agent) put on the market for this purpose is suitable as the binding inhibitor of the present invention. For example, WO98 / 03730, JP-A-11-200284, JP-A-11-350380, Examples thereof include compounds disclosed in JP2003-96694A, JP2003-96695A, and the like. Specifically, higher alcohol ethylene and / or propylene oxide adduct, polyhydric alcohol type nonionic surfactant, higher fatty acid ethylene oxide adduct, polyhydric alcohol and fatty acid ester compound, polyhydric alcohol and fatty acid Ethylene oxide adducts of these ester compounds, fatty acid polyamidoamines, fatty acid diamidoamines, fatty acid monoamides, or polyalkylenepolyamine / fatty acid / epichlorohydrin condensates can be used alone or in combination of two or more. can do. Preferred are polyhydric alcohol and fatty acid ester compounds, fatty acid diamide amines, fatty acid monoamides, polyalkylene polyamines / fatty acids / epichlorohydrin condensates and the like. Bulky chemicals on the market include BASF's Sulsol VL, Bayer's Bi-Volume P Liquid, Kao's KB-08T, 08W, KB110, 115, Sanki's React Pake, Nippon PMC ), PT-205, Nippon Oil & Fats Co., Ltd. DZ2220, DU3605, Arakawa Chemical Co., Ltd. R21001, and these may be used alone or in combination of two or more. In order to improve the air permeability of the base paper, the coated paper of the present invention preferably contains 0.1 to 10 parts by weight of pulp interfiber binding inhibitor per 100 parts by weight of pulp, in particular 0.2 to 1. It is preferable to contain 0.0 part by weight. In the present invention, it is also possible to use a pulp interfiber bond inhibitor and a light calcium carbonate-silica composite in combination.

In addition, chemicals normally used in the paper making process, such as a paper strength enhancer, a sizing agent, an antifoaming agent, a coloring agent, a softening agent, etc., as necessary for these paper stocks, do not impair the effects of the present invention. And can be added to make paper.
Further, if necessary, chemicals normally used in the paper making process, for example, paper strength enhancer, sizing agent, antifoaming agent, coloring agent, etc., are added to the paper stock within a range not inhibiting the effect of the present invention. can do.

The paper making method of the base paper is not particularly limited, and the base paper made by acid paper making, neutral paper making, and alkali paper making using a long net machine including a top wire, a round net machine, and a gap former machine. Any of these may be used. In addition, a base paper preliminarily coated with starch, polyvinyl alcohol or the like using a size press, a gate roll coater, a bill blade, or the like can be used. As the coating base paper, those having a basis weight of about 25 to 500 g / m ² used for general coated paper are used, and more preferably 50 to 150 g / m ² .

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. The range of the coating amount of the present invention is about 5 to 30 g / m ² per side of the base paper, and is preferably 7 g / m ² or more and 20 g / m ² or less per side from the viewpoint of gravure printing suitability and photocatalytic effect.

As a method for drying the wet coating layer, for example, usual methods such as a steam heater, a gas heater, an infrared heater, an electric heater, a hot air heater, a microwave, and a cylinder dryer are used.

The coated paper coated and dried as described above can be smoothed with a super calender, a high temperature hot soft nip calender or the like in order to impart smoothness. In the present invention, in order to obtain a gravure coated paper having good gravure suitability and having a photocatalytic effect, the calendering condition is preferably 100 to 400 kg / cm, more preferably 150-300 kg / cm.
In the present invention, it is preferable that the PPS roughness is in the range of 0.1 to 1.5 μm in order to obtain good gravure printing quality and a photocatalytic function. When the PPS roughness exceeds 1.5 μm, the gravure suitability tends to be inferior. On the other hand, when the PPS roughness value is lower than 0.1 μm, the smoothness is high but the coating layer has a dense structure, and the surface area with air is small, so that the photocatalytic effect blended in the coating layer is not sufficient. The PPS roughness can be prepared by calendering conditions, base paper formulation, paint blending, coating amount papermaking method, coating method and the like.

EXAMPLES The present invention will be specifically described below with reference to examples, but of course 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, it tested based on the following evaluation methods about the coating liquid and the obtained coated paper for printing.
(Evaluation methods)
(1) Particle measurement of titanium oxide: calculated from a photograph taken with an electron microscope.
The fine titanium oxide slurry was thinly applied on a data base for an electron microscope and dried with a drier set at 40 ° C. Then, it image | photographed with the imaging magnification of 10000 times of FE-SEM (Field emission scanning electron microscope / JEOL Co., Ltd. product JSM-6700F), and observed and measured particle | grains. About the secondary particle, the average value which measured 100 secondary particle diameters was made into the average particle diameter of a secondary particle.
(2) PPS roughness: measured based on ISO8791 / 4. The backing material was a hard backing material having a hardness of 95 IRHD, and the clamp pressure was measured at 1000 kPa.
(3) Speckle: Monochromatic printing was performed with a gravure printing test machine from the Ministry of Finance, Printing Bureau, and the occurrence of misdots in 40% of the halftone part was visually evaluated.
◎: Excellent, ○: Excellent, △: Slightly problematic, ×: Problem present (4) Photocatalytic effect: Evaluated by photocatalyst performance evaluation test method IIb “Gasbag B method” established by the Photocatalyst Products Council . The acetaldehyde decomposition rate (%) after irradiation with ultraviolet rays for 20 hours at an ultraviolet intensity of 1 mW / cm ² was measured and evaluated in four stages according to the decomposition rate.
A: Extremely excellent (decomposition rate: 99% or more), B: Excellent (same: 99-50%), B: Inferior (same: 49% -10%), X: Very inferior (same: 10% or less)
(5) Operability: The operational problems that occur when producing the coated paper for printing of the present invention were evaluated in four stages. The operational problems referred to here include, for example, clogging of pipes when manufacturing paints and sending paints to the coater, and streaks during coating.
A: Very good, B: Excellent, B: Somewhat problematic, B: Some problem [Example 1]
<Preparation of coating liquid A>
Powdered fine titanium oxide (SSP-25 manufactured by Sakai Chemical Co., Ltd .; primary particle size 20 to 30 nm, average particle size of secondary particles 1200 nm) 10 parts (solid content), colloidal silica (silica doll 30 manufactured by Nippon Chemical Industry Co., Ltd.) 10 The part was stirred with a serie mixer for 1 hour. The total solid content of both substances at this time is 46.2%. After stirring for 1 hour, 6 parts of colloidal silica was further added and stirred. Among them, 22 parts of heavy calcium carbonate (Fmatec FMT-97), 26 parts of fine clay (Amazon Plus, CADAM), 2 parts of secondary clay (ICS, KCS), delamination clay ( Imerys Astra Plate) 27 parts pigment added to the slurry of polyacrylic acid soda as a dispersant (0.2 parts inorganic pigment) and dispersed in a serie mixer to give a pigment with a solid content of 62% The slurry was adjusted. To the pigment slurry thus obtained, 5 parts of non-thickening type styrene / butadiene copolymer latex (glass transition temperature—10 ° C.) is added, and water is further added to form a coating solution having a solid content concentration of 62%. Obtained.
The coated base paper used was a high quality paper having a basis weight of 59.0 g / m ² containing 7% by weight of the light calcium carbonate-silica composite A as a filler and 100% of chemical pulp as paper pulp.
<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 O concentration was 6.1 wt / wt%. After adding 57 parts of sodium silicate solution, water was added to make the total amount 200 parts. The 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 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 70/30.
After coating the above base paper on both sides with a blade coater at a coating speed of 500 m / min so that the coating amount per side is 13 g / m ² , the coating paper has a moisture content of 5 % To dry. Next, a super calender treatment was performed at a roll temperature of 65 ° C., 10 nips, a calendering linear pressure of 200 kg / cm at the bottom, and a paper feeding speed of 700 m / min to obtain a coated paper for gravure printing.
[Example 2]
In Example 1, a gravure coated paper was obtained in the same manner as in Example 1 except that the number of latex blending parts was changed to 7 parts instead of 5 parts of latex in the coating liquid.
[Example 3]
In Example 1, in place of 10 parts of powdered fine titanium oxide, 16 parts of colloidal silica, and 15 parts of secondary clay in the coating solution, 5 parts of powdered fine titanium oxide (SSP-25 manufactured by Sakai Chemical Co., Ltd.) (solid content) ), 5 parts of colloidal silica (Silica Doll 30 manufactured by Nippon Chemical Industry Co., Ltd.) was stirred with a serie mixer for 1 hour. The total solid content of both substances at this time is 46.2%. After stirring for 1 hour, 3 parts of colloidal silica was further added and stirred. Among them, 22 parts of heavy calcium carbonate (Fmatec FMT-97), 26 parts of fine clay (Amazon Plus made by CADAM), 20 parts of secondary clay (KCS made by Imerys), delamination clay (made by Imerys) Astra Plate) Implemented except that 27 parts of pigment was added to 0.2 parts of sodium polyacrylate as a dispersant and the pigment slurry dispersed with a serie mixer was added to a pigment slurry with a solid content concentration of 62%. A gravure coated paper was obtained in the same manner as in Example 1.
[Example 4]
In Example 1, a gravure coated coated paper was obtained in the same manner as in Example 1 except that the number of latex blended parts was changed to 10 parts instead of 5 parts of latex in the coating solution.
[Example 5]
In Example 1, 0.3% of bulking agent (KB-115: Kao Co., Ltd.), which is an organic compound having an action of inhibiting the interfiber bonding of pulp, is used as a base paper for coating. A coated paper for gravure printing was obtained in the same manner as in Example 1 except that high-quality paper having a basis weight of 59.0 g / m ² containing 100% chemical pulp was used.
[Example 6]
In Example 1, powdered fine titanium oxide (SSP-25 manufactured by Sakai Chemical Co., Ltd .; primary particle size 20 to 30 nm, average particle size of secondary particles 1200 nm) 10 parts (solid content), colloidal silica (manufactured by Nippon Chemical Industry Co., Ltd.) Silica Dole 30) is stirred for 1 hour with a serie mixer, and then mixed with powdered fine titanium oxide and colloidal silica in which 6 parts of colloidal silica is added and stirred. Powdered fine titanium oxide (manufactured by Sakai Chemical Co., Ltd.) SSP-25) 10 parts (solid content) and 4.5 parts of colloidal silica (Silica Doll 30 manufactured by Nippon Chemical Industry Co., Ltd.) were stirred with a serie mixer for 1 hour (the total solid content at this time was 58). %) And coated paper for gravure printing was obtained in the same manner as in Example 1 except that 11.5 parts of colloidal silica was added and stirred.
[Example 7]
In Example 1, powdered fine titanium oxide (SSP-25 manufactured by Sakai Chemical Co., Ltd .; primary particle size 20 to 30 nm, average particle size of secondary particles 1200 nm) 10 parts (solid content), colloidal silica (manufactured by Nippon Chemical Industry Co., Ltd.) Silica Dole 30) is stirred for 1 hour with a serie mixer, and then mixed with powdered fine titanium oxide and colloidal silica in which 6 parts of colloidal silica is further added and stirred. Powdered fine titanium oxide (manufactured by Sakai Chemical Co., Ltd.) SSP-25: 10 parts (solid content) of primary particle diameter 20-30 nm, average particle diameter of secondary particles 1200 parts, and 10 parts of colloidal silica (silica doll 30 manufactured by Nippon Chemical Industry Co., Ltd.) were stirred for 1 hour with a serie mixer ( At this time, a gravure coated paper was obtained in the same manner as in Example 1 except that the total solid content of both substances was changed to only 46.2%). It was.
[Comparative Example 1]
In Example 1, in place of 10 parts of powdered fine titanium oxide, 16 parts of colloidal silica, and 15 parts of secondary clay in the coating solution, no powdered fine titanium oxide, no colloidal silica, and 25 parts of secondary clay Except for the change, a gravure-coated paper was obtained in the same manner as in Example 1.
[Comparative Example 2]
In Example 1, instead of 10 parts of powdered fine titanium oxide, 16 parts of colloidal silica, 15 parts of secondary clay, and 22 parts of heavy calcium carbonate in the coating liquid, 40 parts of powdered fine titanium oxide, 64 parts of colloidal silica Changed to 7 parts heavy calcium carbonate. At this time, the solid content concentration of the topcoat coating solution was 48%, and the coating speed was set to 400 m / min in order to make the moisture of the coated paper 5%. For other conditions, a gravure coated paper was obtained in the same manner as in Example 1.
[Comparative Example 3]
In Example 1, a gravure coated coated paper was obtained in the same manner as in Example 1 except that the number of latex blended parts was changed to 15 parts instead of 5 parts of latex in the coating solution.
[Comparative Example 4]
<Preparation of coating liquid B>
Fine titanium oxide slurry (CSB-M manufactured by Sakai Chemical Co., Ltd .; primary particle diameter 20-30 nm, average particle diameter of secondary particles 1000 nm) 10 parts (solid content), colloidal silica (silica doll 30 manufactured by Nippon Chemical Industry Co., Ltd.) 16 parts Was stirred with a serie mixer for 1 hour. Among them, as a pigment, 22 parts of heavy calcium carbonate (Fimatech FMT-97), 26 parts of fine-grained clay (Amazon Plus made by CADAM), 2nd grade clay (Imerys KCS) 15 parts, delamination clay ( Imerys Astra Plate) 27 parts pigment added to the slurry of polyacrylic acid soda as a dispersant (0.2 parts inorganic pigment) and dispersed in a serie mixer to give a pigment with a solid content of 62% The slurry was adjusted. To the pigment slurry thus obtained, 5 parts of non-thickening type styrene / butadiene copolymer latex (glass transition temperature—10 ° C.) is added, and water is further added to form a coating solution having a solid content concentration of 62%. Obtained. When manufacturing the coating liquid B, the fluidity of the fine titanium oxide slurry was poor, and time was spent when preparing the paint.
The coated base paper used was a high quality paper having a basis weight of 59.0 g / m ² containing 7% by weight of the light calcium carbonate-silica composite A as a filler and 100% of chemical pulp as paper pulp.
After coating the above base paper on both sides with a blade coater at a coating speed of 500 m / min so that the coating amount per side is 13 g / m ² , the coating paper has a moisture content of 5 % To dry. Next, a super calender treatment was performed at a roll temperature of 65 ° C., 10 nips, a calendering linear pressure of 200 kg / cm at the bottom, and a paper feeding speed of 700 m / min to obtain a coated paper for gravure printing.
[Comparative Example 5]
<Preparation of coating liquid C>
Powdered fine titanium oxide (SSP-25 manufactured by Sakai Chemical Co., Ltd .; primary particle diameter 20-30 nm, secondary particle average particle diameter 1200 nm) 10 parts, colloidal silica (Nippon Chemical Industry Co., Ltd. Silica Doll 30) 3 parts serie mixer For 1 hour. The total solid content of both substances at this time is 65%. After stirring for 3 hours, 13 parts of colloidal silica was further added and stirred. Among them, 22 parts of heavy calcium carbonate (Fmatec FMT-97), 26 parts of fine clay (Amazon Plus, CADAM), 2 parts of secondary clay (ICS, KCS), delamination clay ( Imerys Astra Plate) 27 parts pigment added to the slurry of polyacrylic acid soda as a dispersant (0.2 parts inorganic pigment) and dispersed in a serie mixer to give a pigment with a solid content of 62% The slurry was adjusted. To the pigment slurry thus obtained, 5 parts of non-thickening type styrene / butadiene copolymer latex (glass transition temperature—10 ° C.) is added, and water is further added to form a coating solution having a solid content concentration of 62%. Obtained. Coating liquid C had high viscosity when titanium oxide was dispersed, and was poor in fluidity, and spent time for dispersion.
The coated base paper used was a high quality paper having a basis weight of 59.0 g / m ² containing 7% by weight of the light calcium carbonate-silica composite A as a filler and 100% of chemical pulp as paper pulp.
After coating the above base paper on both sides with a blade coater at a coating speed of 500 m / min so that the coating amount per side is 13 g / m ² , the coating paper has a moisture content of 5 % To dry. Next, a super calender treatment was performed at a roll temperature of 65 ° C., 10 nips, a calendering linear pressure of 200 kg / cm at the lowest stage, and a paper feeding speed of 700 m / min to obtain a coated paper for gravure printing.
[Comparative Example 6]
<Preparation of coating liquid D>
Powdered fine titanium oxide (SSP-25 manufactured by Sakai Chemical Co., Ltd .; primary particle size 20-30 nm, average particle size of secondary particles 1200 nm) 10 parts (solid content), colloidal silica (silica doll 30 manufactured by Nippon Chemical Industry Co., Ltd.) 16 The part was stirred with a serie mixer for 1 hour. The total solid content of both substances at this time is 41%. After stirring for 1 hour, 6 parts of colloidal silica was further added and stirred. Among them, 22 parts of heavy calcium carbonate (Fmatec FMT-97), 26 parts of fine clay (Amazon Plus, CADAM), 2 parts of secondary clay (ICS, KCS), delamination clay ( Imerys Astra Plate) 27 parts pigment added to the slurry of polyacrylic acid soda as a dispersant (0.2 parts inorganic pigment) and dispersed in a serie mixer to give a pigment with a solid content of 62% The slurry was adjusted. To the pigment slurry thus obtained, 5 parts of non-thickening type styrene / butadiene copolymer latex (glass transition temperature—10 ° C.) is added, and water is further added to form a coating solution having a solid content concentration of 62%. Obtained.
The coated base paper used was a high quality paper having a basis weight of 59.0 g / m ² containing 7% by weight of the light calcium carbonate-silica composite A as a filler and 100% of chemical pulp as paper pulp.
After coating the above base paper on both sides with a blade coater at a coating speed of 500 m / min so that the coating amount per side is 13 g / m ² , the coating paper has a moisture content of 5 % To dry. Next, a super calender treatment was performed at a roll temperature of 65 ° C., 10 nips, a calendering linear pressure of 200 kg / cm at the bottom, and a paper feeding speed of 700 m / min to obtain a coated paper for gravure printing. When applying the coating liquid D, many streak-like scratches derived from undispersed titanium oxide aggregates were observed.
The above results are shown in Table 1. :

Claims (7)

In a coated paper for gravure printing in which a coating layer containing a pigment and an adhesive is provided on a base paper, 1 to 30 parts by weight of powdered titanium oxide having a photocatalytic action in the coating layer per 100 parts by weight of the pigment The powdered titanium oxide is a silica sol or alumina sol previously mixed in a state where the solid content of both substances is 45 to 60% by weight, and is a copolymer for 100 parts of pigment. A coated paper for gravure printing, comprising 1 to 10 parts by weight of latex. The powdered titanium oxide is such that the ratio of titanium oxide to silica sol or alumina sol is 2: 1 to 1: 2 in a state where the solid content obtained by previously adding both substances in silica sol or alumina sol is 45 to 60% by weight. 2. The coated paper for gravure printing according to claim 1, wherein a mixing process is performed. The powdered titanium oxide is preliminarily mixed with silica sol or alumina sol in a state where the solid content of both substances is 45 to 60% by weight, and then the silica sol or alumina sol has a ratio of titanium oxide to silica sol or alumina sol of 2: The coated paper for gravure printing according to claim 1, wherein the mixture is further added and mixed so as to have a ratio of 1 to 1: 2. The coated paper for gravure printing according to any one of claims 1 to 3, wherein the base paper contains a light calcium carbonate-silica composite or an organic compound having an action of inhibiting interfiber bonding between pulps. The coating layer contains 1 to 7 parts by weight of a copolymer latex having a glass transition temperature of -50 ° C to 20 ° C with respect to 100 parts by weight of the pigment. Coated paper for gravure printing. The coated paper for gravure printing according to any one of claims 1 to 5, wherein the PPS roughness of the coated paper is 0.1 to 1.5 µm. The primary particle diameter of the said titanium oxide is 5-100 nm, and a secondary particle diameter is 300-2000 nm, The coated paper for gravure printing in any one of Claims 1-6 characterized by the above-mentioned.