JP2013124427A - Paper for printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide paper for printing, which has high glossiness in a printed part and shows superior printability in both of flexographic printing and gravure printing.SOLUTION: The paper for printing has two layers or more of pulp fiber layers, a surface having a coating liquid applied thereon which contains a sizing agent, and a hydrophilic resin layer that is arranged between a first pulp fiber layer that is located on a surface and a second pulp fiber layer that is stacked in an inner side of the first pulp fiber layer. It is preferable that the hydrophilic resin layer contains starch as a main component. It is also preferable that the first pulp fiber layer has a basis weight of 15 g/mor more and 25 g/mor less.

Description

  The present invention relates to printing paper.

The printing paper is required to have characteristics such as a high ink drying speed, no ink repelling, bleeding, or overflow, a high recording density, and no waviness due to ink absorption. Conventionally, so-called coated paper has been used as printing paper having such characteristics. In this coated paper, an ink receiving layer is applied to the base paper by applying a coating liquid comprising an inorganic pigment and a binder for fixing the pigment to the paper at a coating amount of about 10 to 40 g / m ² (dry weight). To improve printing ink acceptance (see Japanese Patent Application Laid-Open No. 7-229090).

  However, the conventional printing paper as described above has a disadvantage in that when water-based ink is used, the ink receiving layer swells and the glossiness of the printed portion is lower than that of the non-printed portion. .

  In recent years, there has been a demand for printing paper that can handle both flexographic printing and gravure printing. However, since water-based ink is usually used for flexographic printing and oil-based ink is used for gravure printing, it is difficult to develop printing paper that can exhibit excellent printability in both cases. .

Japanese Patent Laid-Open No. 7-229090

  The present invention has been made based on the above-described circumstances, and an object of the present invention is to provide a printing paper having a high glossiness of a printed portion and excellent printability of either flexographic printing or gravure printing.

The invention made to solve the above problems is
A printing paper having two or more pulp fiber layers, the surface of which is coated with a coating liquid containing a sizing agent,
A hydrophilic resin layer is interposed between the first pulp fiber layer located on the surface and the second pulp fiber layer laminated on the inside thereof.

  According to the printing paper, since the hydrophilic resin layer is interposed between the first pulp fiber layer and the second pulp fiber layer, swelling in the vicinity of the surface due to the ink is suppressed, and the gloss of the printed portion is increased. be able to. In addition, according to the printing paper, since the hydrophilic resin layer suppresses the penetration of the sizing agent and the like contained in the coating liquid, the sizing agent can remain in the vicinity of the surface. Thus, according to the printing paper, since a large amount of sizing agent is present near the surface, the penetration of water-based ink can be suppressed. In addition, according to the printing paper, permeation of oil-based ink can be suppressed due to the presence of the hydrophilic resin layer. Therefore, the printing paper can exhibit excellent printability for both flexographic printing and gravure printing.

  The hydrophilic resin layer is preferably composed mainly of starch. As described above, by forming the hydrophilic resin layer from starch, the strength is increased, the swelling by ink and the penetration of the sizing agent are further suppressed, and the ability to improve the glossiness can be further enhanced.

  The starch is preferably an acetate esterified starch. Thus, the said various functions improve more by using acetate esterified starch. Acetic esterified starch is said to have more remarkable diffusion in the MD and CD directions than the penetration of paper in the Z direction. By using acetic esterified starch, coating unevenness on the paper surface is reduced. Thus, it is possible to improve the covering property and prevent the fine fibers present on the paper surface from coming into direct contact with the plate in flexographic printing and gravure printing. If the surface treatment agent has a poor coverage on the fine fibers, the water-based ink added to the paper surface during flexographic printing easily penetrates into the paper layer, and the fine fibers in the paper layer are easily released to the outside. Therefore, it is estimated that fine raw materials that have exuded reduce print gloss and saturation. In particular, when acetate esterified starch is used, the hydrophobicity can be increased due to the presence of acetyl groups. Therefore, even when the paper surface is wet with water-based ink during flexographic printing, the paper surface free energy is reduced, so the paper layer It is difficult to get wet with water and water absorption is suppressed. As a result, it is considered that the fine fibers are not raised due to the water-based ink, the generation of paper dust and the like is reduced or eliminated, and the suitability for gravure printing using the solvent-based ink can be secured.

The basis weight of the first pulp fiber layer is preferably 15 g / m ² or more and 25 g / m ² or less. Thus, since the sizing agent can be fixed near the surface by providing the relatively thin first pulp fiber layer, the glossiness can be increased. Moreover, since the sizing agent and the hydrophilic resin layer are located in the vicinity of the surface, the penetration of the water-based ink and the oil-based ink can be further suppressed.

  The sizing agent may be an anionic styrene resin. Thus, by using an anionic styrene resin as a sizing agent, a coating layer (film) containing this resin is formed in the vicinity of the surface, and the ability to improve the glossiness of the coated paper can be further enhanced. .

  The content of the anionic styrene resin in the solid content in the coating agent is preferably 80% by mass or more. By doing in this way, the said film | membrane mainly contains anionic styrene resin and the said various functions can be improved more.

  The first and second pulp fiber layers preferably contain an internal sizing agent. In addition to the externally added sizing agent, ink penetration can be more effectively suppressed by including the internal sizing agent in the layer on the surface side in this way, so that printability such as glossiness is further improved. be able to.

  As described above, according to the printing paper of the present invention, the gloss of the printed portion is high and excellent printability can be exhibited. Therefore, the printing paper can be suitably used for printing methods such as gravure printing and flexographic printing.

It is a typical sectional view of printing paper concerning one embodiment of the present invention.

  Hereinafter, embodiments of the printing paper of the present invention will be described with reference to the drawings as appropriate.

  The printing paper 10 in FIG. 1 has five pulp fiber layers. Specifically, it has the 1st pulp fiber layer 1, the 2nd pulp fiber layer 2, the 3rd pulp fiber layer 3, the 4th pulp fiber layer 4, and the 5th pulp fiber layer 5 in order from the surface side. A hydrophilic resin layer 6 is interposed between the first pulp fiber layer 1 and the second pulp fiber layer. The surface (the surface of the first pulp fiber layer 1) has a coating layer 7 formed by coating a coating liquid containing a sizing agent.

  According to the printing paper 10, since the hydrophilic resin layer 6 is interposed between the first pulp fiber layer 1 and the second pulp fiber layer 2, swelling in the vicinity of the surface due to ink is suppressed, and Glossiness can be increased. Further, according to the printing paper 10, since the hydrophilic resin layer 6 suppresses the penetration of the sizing agent and the like contained in the coating liquid, the sizing agent can be kept near the surface. According to the printing paper 10, since a large amount of sizing agent is present in the vicinity of the surface in this way, the penetration of water-based ink can be suppressed. Further, according to the printing paper 10, the presence of the hydrophilic resin layer 6 can suppress the penetration of oil-based ink. Therefore, the printing paper 10 can exhibit excellent printability for both flexographic printing and gravure printing.

(Pulp fiber layer)
Each said pulp fiber layer means the layer formed by paper-making the pulp slurry which has a pulp fiber as a main component.

  The pulp is not particularly limited. For example, waste paper pulp (DIP), chemical pulp (for example, hardwood kraft pulp: LBKP, softwood kraft pulp: NBKP, etc.), mechanical pulp (for example, thermomechanical pulp: TMP, pressured kraft) Pulp, PGW, refiner ground pulp: RGP, ground pulp, etc.) and non-wood pulp such as kenaf, bagasse, hemp, and cotton. Among these, it is preferable to use waste paper pulp.

  In the pulp which forms the 1st pulp fiber layer 1, it is preferable that 50 to 80 mass% of used paper pulp is included. In this way, by increasing the content ratio of the used paper pulp in the first pulp fiber layer 1, the components of the coating liquid can be easily penetrated in the first pulp fiber layer 1, and the anchor effect of the coating liquid component is enhanced and strengthened. An appropriate coating layer 7 can be formed.

The first basis weight of the pulp fiber layer 1 (with volume), is not particularly limited, but is preferably 15 g / ^{m 2} or more 25 g / ^{m 2} or less. Since the printing paper 10 has the thin first pulp fiber layer 1 as described above, the coating liquid, particularly the sizing agent contained therein and the aqueous or oil-based ink can be kept near the surface. Therefore, according to the printing paper 10, it is possible to increase the glossiness and to improve the printability in any of flexographic printing and gravure printing.

The basis weight (weight) of the other pulp fiber layers (second pulp fiber layer to fifth pulp fiber layer) is not particularly limited, and any layer is, for example, 20 g / m ² or more and 45 g / m ² or less. can do.

  An internal sizing agent can be internally added to each pulp fiber layer. The internal additive sizing agent is not particularly limited, and examples thereof include rosin sizing agents, alkyl ketene dimers, ASA (alkenyl succinic anhydride) CMC (carboxyl methyl cellulose), PVA (polyvinyl alcohol), and the like. Among these, a rosin sizing agent made of a modified natural resin is preferable. A rosin-based sizing agent composed of a modified natural resin is effective in imparting sizing properties to printing paper made at a relatively low pH (pH 5.0 to 6.5), without causing stains in the paper making system. Ink penetration into the fibers can be effectively suppressed.

  By using a combination of a rosin sizing agent and a sulfuric acid band in the papermaking system, the rosin sizing agent can be efficiently fixed on the fiber in the papermaking system. To that end, first of all, it is important to add sufficient rosin sizing agent to react with the fibers in the slurry. The amount of rosin sizing agent added is 0.4% of the pulp. It is preferably 1.5% or less. Even if 1.5% or more of the rosin sizing agent is added, the size performance is saturated, and if it is added excessively, problems such as “foaming” in the system become remarkable.

  Next, the amount of sulfuric acid band necessary for fixing the rosin-based sizing agent to the fiber and allowing the rosin-based sizing agent to react efficiently on the fiber is necessary. The inventors have found that a size ratio of 1.0 to 3.0 expresses the size property most effectively. When the ratio of the amount of sulfuric acid band to the amount of the rosin-based sizing agent is less than 1, sufficient sizing properties cannot be obtained because a sufficient sulfuric acid band does not exist in the system. Moreover, even if the addition ratio of the sulfuric acid band to the rosin sizing agent exceeds 3.0, the effect of improving the sizing property is saturated, and the sizing property tends to decrease. In addition, the addition of an excessive sulfuric acid band unnecessarily lowers the pH in the system, and provides a solution to the problem of the present invention that obtains a printing paper having high gloss in the printed part and excellent printability for both flexographic and gravure printing. It becomes a factor that inhibits the chemical effect.

  Furthermore, in a system in which a rosin sizing agent and a sulfuric acid band are added so as to satisfy the above-mentioned conditions, the pH of the slurry is made as low as possible when adding the rosin sizing agent, so that the sulfuric acid band is efficiently pulp fiber, rosin type The first pulp layer can ensure the effect of the internally added sizing agent by making the layers of the printing paper in the present invention combine so as to affect the size. For example, the first pulp layer can be secured to the other layers such as the lower layer and the fifth layer. A paper layer can be formed without being adversely affected by the sizing agent contained in the pulp layer.

  It is preferable that an internal additive sizing agent is internally added to the first pulp fiber layer 1 and an internal additive sizing agent is not internally added to the fifth pulp fiber layer 5. Furthermore, an internal sizing agent is added only to the first pulp fiber layer 1 and the second pulp fiber layer 2, and the other third pulp fiber layer 3, fourth pulp fiber layer 4 and fifth pulp fiber layer 5 are added. It is preferable not to internally add an internal sizing agent. Furthermore, it is preferable to make the addition amount of the internal sizing agent in the first pulp fiber layer 1 larger than the addition amount of the internal sizing agent in the second pulp fiber layer.

  In this way, by adding an internal sizing agent to the first pulp fiber layer 1, preferably the first pulp fiber layer 1 and the second pulp fiber layer, the size property on the surface side is improved and the ink penetration is more effective. Therefore, printability such as glossiness can be further enhanced. In particular, by making the content of the sizing agent in the first pulp fiber layer greater than the content of the second pulp fiber layer, the moisture soaked into the first pulp fiber layer can easily move to the second pulp fiber layer side. . Therefore, even when the amount of the sizing agent added to the first pulp fiber layer is increased, it is possible to suppress a decrease in the absorbability of the water-based ink.

  In addition, by not adding an internal sizing agent to the back side layer such as the fifth pulp fiber layer 5, it is possible to improve the bonding property with other paper when using an aqueous paste or the like. it can. Examples of the bonding with the other paper include bonding with a core when the printing paper is used as a liner.

  A paper strength enhancer can be internally added to each pulp fiber layer. The paper strength enhancer is not particularly limited, and examples thereof include vegetable gums, aqueous cellulose derivatives, and polyacrylamides. Among these, cationic polyacrylamide is preferable.

The cationic polyacrylamide used in the present invention is obtained by cationizing an amide group (—CONH ₂ ) using a Mannich reaction or Hoffman reaction from a water-soluble polymer obtained by a usual polymerization method. By forming a cationic polyacrylamide derivative with a copolymer of a cationic monomer having a secondary, tertiary, or quaternary amino group such as ethyl methacrylate and an acrylamide, or by cationizing by a conventionally known method. A cationic polyacrylamide derivative can be obtained. The degree of substitution of the cationic group is preferably 0.01 or more, more preferably 0.03 or more, but a further suitable range is 0.05 to 0.5. The molecular weight of the polyacrylamide derivative is 2 million or less, preferably 1.5 million or less, more preferably about 100,000 or more and 1.3 million or less.

  According to the knowledge of the present inventors, the first pulp fiber layer is required as a quality necessary for obtaining a printing paper having a high glossiness of the printed portion, which is a problem in the present invention, and excellent in both printability of flexographic printing and gravure printing. It is necessary to have sufficient printing resistance on one printing surface, and polyacrylamide can ensure sufficient printing resistance even for flexographic printing and gravure printing. It is possible to reduce the glossiness of the printed part even when printing using conflicting printing inks such as flexographic printing and gravure printing due to the synergistic effect with the hydrophilic resin and sizing agent used together. it can.

  It is preferable that a paper strength enhancer is internally added to the first pulp fiber layer 1 and a paper strength enhancer is not internally added to the fifth pulp fiber layer 5. Furthermore, an internal sizing agent is internally added only to the first pulp fiber layer 1 to the third pulp fiber layer 3, and a paper strength enhancer is added to the other fourth pulp fiber layer 4 and the fifth pulp fiber layer 5. It is preferable not to add internally.

  In this manner, by adding a paper strength enhancer to the surface layer, swelling in the vicinity of the surface due to the ink can be further suppressed, and the glossiness of the printed portion can be increased. In addition, by not adding a paper strength enhancer to the back side layer, it is possible to enhance the bonding property with other paper or the like when aqueous paste or the like is used.

  Each of the pulp fiber layers may contain components other than the pulp fiber, the internal sizing agent, and the paper strength enhancer. Examples of other components include a sulfuric acid band, a dye, a filler, and the like.

(Hydrophilic resin layer)
The hydrophilic resin layer 6 is interposed between the first pulp fiber layer 1 and the second pulp fiber layer 2. According to the printing paper 10, by having the hydrophilic resin layer 6, the strength is increased, the swelling in the vicinity of the surface by the ink is suppressed, and the glossiness of the printed portion can be increased. Further, according to the printing paper 10, since the hydrophilic resin layer 6 suppresses the penetration of the sizing agent and the like contained in the coating liquid, the sizing agent (the coating layer 7) can be kept near the surface. . Therefore, according to the printing paper 10, since a large amount of sizing agent is present in the vicinity of the surface in this way, the penetration of water-based ink can be suppressed. Further, since the hydrophilic resin layer 6 exists in the vicinity of the surface, the permeation of oil-based ink can be suppressed. As a result, according to the printing paper 10, it is possible to increase the glossiness of the printed portion and exhibit excellent printability.

  It does not specifically limit as hydrophilic resin which forms the hydrophilic resin layer 6, For example, starch, gelatin, polyvinyl alcohol, polyethyleneglycol, dextrin, polyvinylpyrrolidone etc. can be mentioned. Among these, starch is preferable from the viewpoints of handleability and strength improvement ability.

  The raw material of the starch is not particularly limited, and various raw and processed starches such as corn starch (corn starch), potato starch, sweet potato starch, tapioca starch, etc. can be used, and tapioca starch is preferred. By using tapioca starch, the interlayer strength is increased, and the ability to improve glossiness and the like can be exhibited more effectively.

  As the starch, oxidized starch, cationized starch, carboxymethylated starch, pregelatinized starch, acetate esterified starch, urea phosphate-modified starch, unmodified starch, etc. can be used. Among these, acetate ester Modified starch is preferred. By using acetate esterified starch, the penetration of the sizing agent and ink can be more effectively suppressed. That is, as the starch, acetate esterified tapioca starch is particularly preferred for the reasons described above.

  Furthermore, in order to enhance the effect of providing the hydrophilic resin layer, it is preferable that a hydrophilic resin layer is also formed between the second pulp fiber layer 2 and the third pulp fiber layer 3. A hydrophilic resin layer can also be provided on the inner side of the third pulp fiber layer and further on the inner fiber layer. However, the formation of an excessive hydrophilic resin layer makes the obtained printing paper hard and hinders box molding. May occur, or impregnation of the paste for bonding into the pulp fiber layer may be suppressed, resulting in poor bonding. Therefore, it is preferable to provide the hydrophilic resin layer only between the first pulp fiber layer and the second pulp fiber layer, or in addition to this, only between the second pulp fiber layer and the third pulp fiber layer.

(Coating layer)
The coating layer 7 is formed by applying a coating liquid containing a sizing agent to the surface.

  The sizing agent is not particularly limited, and known ones can be used, and examples thereof include starch, styrene-based sizing agent, acrylate-based sizing agent, and alkyl ketene dimer. Among these, styrenic sizing agents are preferable from the viewpoint of increasing glossiness.

  It is more preferable to use an anionic styrene resin as the styrenic sizing agent. By using an anionic styrene resin as a sizing agent, a film containing this resin is formed in the vicinity of the surface, and the ability to improve the glossiness of the coated paper can be further enhanced.

  The anionic styrenic resin is not particularly limited as long as it is an anionic resin containing styrene as a monomer, and known ones can be used. Examples of commercially available anionic styrenic resins include Polymeron 351S manufactured by Arakawa Chemical Industries.

  Examples of the anionic styrenic resin include styrene monomers (eg, styrene, α-methylstyrene, chlorostyrene, cyanostyrene, etc.) and anionic monomers (eg, acrylic acid monomers (eg, acrylic acid, methacrylic acid, croton). Acid, isocrotonic acid, 2-ethylacrylic acid, 3-tert-butylacrylic acid, methyl acrylate, ethyl acrylate, iso-butyl acrylate, octenyl acrylate, etc.), maleic acid monomers (for example, maleic acid, methyl And a copolymer of maleic acid, phenylmaleic acid, chloromaleic acid, fumaric acid, itaconic acid, muconic acid, methyl maleate, tert-butyl maleate, diethyl maleate, and the like). For example, styrene / acrylic acid copolymer, styrene / (meth) acrylic acid copolymer (note that (meth) acrylic acid means “acrylic acid and / or methacrylic acid”), styrene / (meth). Acrylic acid / (meth) acrylic acid ester copolymers, styrene / maleic acid copolymers, styrene / maleic acid half ester copolymers, styrene / maleic acid ester copolymers and the like are applicable. This copolymer may be used in the form of sodium salt, potassium salt or ammonium salt. These copolymers are used alone or in combination of two or more.

  In this copolymer, the ratio of the styrenic monomer to the anionic monomer is preferably in the range of 80:20 to 20:80. Note that at least one styrene monomer and an anionic monomer may be used. Further, this copolymer may be copolymerized in a small amount with the above-mentioned styrenic monomer and / or anionic monomer and a polymerizable monomer as long as the present invention is not hindered.

  Examples of the method for producing the copolymer include an aqueous solution polymerization method, a solvent polymerization method, a reverse phase emulsion polymerization method, a precipitation polymerization method, and a suspension polymerization method.

  The copolymer may have a weight average molecular weight of about 10,000 to 1,000,000, and more desirably, a rosin size within a range of 10,000 to 100,000 is preferably included in the first pulp fiber layer. A synergistic effect with an agent and a paper strength enhancer is desirable. When the molecular weight is less than 10,000, this copolymer cannot form a sufficient film, so that the gloss of the printed portion, which is the subject of the present invention, is high, and it is suitable for either flexographic printing or gravure printing. In addition, it is difficult to obtain an excellent printing paper and it is not preferable in terms of the effect of improving the surface strength. On the other hand, when the molecular weight is greater than 1,000,000, there is a risk of causing operational problems due to the high viscosity of the coating liquid.

  The content of the anionic styrene resin in the solid content in the coating agent is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 97% by mass or more. By doing in this way, the coating layer 7 mainly contains anionic styrene resin, and the said function can be improved more.

  The coating agent may contain other components in addition to the sizing agent. Examples of the other components include a paper strength enhancer, a water-soluble polymer, a pigment, and other additives.

Examples of the coating amount of the coating agent is not particularly limited, 0.1 g / ^{m 2} or more 1 g / ^{m 2} or less is preferable in terms of solid content. By setting it as such a coating amount, it can be set as the printing paper corresponding suitably for both gravure printing and flexographic printing. When the coating amount is less than the above lower limit, water-based ink is likely to permeate, and printability such as glossiness during flexographic printing may be reduced. On the contrary, if the coating amount exceeds the above upper limit, the oil-based ink is likely to permeate, and printability such as glossiness during gravure printing may be deteriorated.

(Production method)
The printing paper can be obtained by, for example, a known paper making method. Specifically, for example, using a liner paper machine equipped with a wire part, a press part, a dryer part, a calendar part, a reel part, and a winder part, it can be obtained by papermaking the raw pulp slurry corresponding to each pulp fiber layer. it can. The hydrophilic resin layer can be formed by spraying an aqueous solution containing a hydrophilic resin.

  In the production of the printing paper, it is preferable to perform gloss calendar processing in the calendar part in addition to drying in the dryer part. By performing the gloss calendar in this way, the smoothness and glossiness of the surface can be increased.

  As processing temperature in the case of this gloss calendar, 150 degreeC or more is preferable and 180 degreeC or more and 210 degrees C or less are more preferable. By performing gloss calendering at such a relatively high temperature, it is possible to finish a printing paper that can more suitably cope with both flexographic printing and gravure printing.

The linear pressure during the gloss calendar is preferably 90 kg / cm ² or more and 140 kg / cm ² or less, more preferably 100 kg / cm ² or more and 130 kg / cm ² or less. By performing the gloss calendering with such a linear pressure, it is possible to finish a printing paper that is excellent in smoothness and can more suitably cope with both flexographic printing and gravure printing.

(Quality etc.)
The basis weight of the printing paper is not particularly limited, but is preferably 100 g / m ² or more and 300 g / m ² or less, and more preferably 120 g / m ² or more and 200 g / m ² or less. By setting the basis weight within such a range, the printing paper can exhibit sufficient strength and the like. Here, the basis weight refers to a value measured according to JIS-P8124.

The degree of bump size on the surface side of the printing paper is preferably 25 g / m ² or more and 60 g / m ² or less, more preferably 30 g / m ² or more and 50 g / m ² or less. By setting the surface to such a sizing degree, good printability can be exhibited for both flexographic printing and gravure printing. Here, the degree of bump size refers to a value measured according to JIS-P8140.

The degree of bump size on the back side of the printing paper is preferably 160 g / m ² or more and 200 g / m ² or less. In this way, by increasing the size of the back surface in this way, it is possible to improve the bonding property with other paper using water glue or the like.

  The smoothness on the surface side of the printing paper is preferably 50 seconds or more, and more preferably 55 seconds or more and 80 seconds or less. By having such a high smoothness on the surface side, the glossiness is increased and excellent printability can be exhibited. Here, smoothness refers to a value measured according to JIS-P8119.

  The printing paper of the present invention is not limited to the above embodiment. The printing paper does not need to have a five-layer structure as long as it has two or more pulp fiber layers. Moreover, the coating liquid may be coated on the back surface. In any case, according to the printing paper, when printed on the surface, the printed portion has high glossiness, and can exhibit excellent printability in both gravure printing and flexographic printing. Therefore, the printing paper can be suitably used for various types of printing paper, and in particular, can be suitably used as printing paper for interior boxes.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. In addition, the addition amount of various chemical | medical agents is the value of solid content conversion.

[Example 1]
As the raw pulp for the first pulp fiber layer, pulp containing 80 % by mass of waste paper pulp was used. As pulp other than waste paper pulp, NBKP and LBKP were used in a mass ratio of 3: 7. In this raw material pulp, an internal sizing agent (Harsize NES-680 emulsion rosin internal sizing agent manufactured by Harima Chemicals Co., Ltd.) (4 kg / t), a sulfuric acid band (9 kg / t), a paper strength agent ( Harima Kasei Co., Ltd. Hermide TA-238 (cationic polyacrylamide) was blended (3 kg / t).
As raw material pulp for the second pulp fiber layer, 100% used paper pulp was used. In this raw material pulp, an internally added sizing agent (Harima Kasei Co., Ltd. Hersize NES-680) (3 kg / t), a sulfuric acid band (9 kg / t), a paper strength agent (Harima Kasei Co., Ltd. Hermide TA-238 cation) (4 kg / t) was compounded.
As a raw material pulp for the third pulp fiber layer, the fourth pulp fiber layer, and the fifth pulp fiber layer, 100% waste paper pulp was used. This raw material pulp was mixed with a sulfuric acid band (5 kg / t).
A base paper having a five-layer structure including first to fifth pulp fiber layers was obtained in order from the surface side using each raw material pulp. The basis weight (weight) of the first pulp fiber layer is 21 g / m ² , the basis weight (weight) of the second pulp fiber layer is 31 g / m ² , and the basis weight (weight) of the third pulp fiber layer is 35 g. / ^{m 2,} the basis weight of the fourth pulp fiber layer (labeled amount) is 35 g / ^{m 2,} the basis weight of the fifth pulp fiber layer (labeled amount) was 36 g / ^{m 2.}
Further, a hydrophilic resin is formed between the first pulp fiber layer and the second pulp fiber layer and between the second pulp fiber layer and the third pulp fiber layer by spray application of an aqueous solution containing an esterified tapioca starch. A layer was formed.
As a coating solution, an anionic styrene resin aqueous solution (Polymaron 351S manufactured by Arakawa Chemical Industries, Ltd.), which is a sizing agent, was applied to the surface by 0.3 g / m ^{2 in} terms of solid content.
In addition, the liner paper machine provided with a wire part, a press part, a dryer part, a calendar part, a reel part, and a winder part was used for papermaking. In the calendar part, a gloss calendar process at 195 ° C. was performed. The linear pressure at this time was 110 kg / cm. Thus, the printing paper of Example 1 was obtained.

[Examples 2 to 25 and Comparative Example 1]
Hydrophilic resin used for hydrophilic resin layer, basis weight and sizing amount of first pulp fiber layer, sizing amount of second pulp fiber layer, sizing agent and coating amount contained in coating liquid, and Printing papers of Examples 2 to 25 and Comparative Example 1 were obtained in the same manner as Example 1 except that the temperature of the gloss calendar was changed as shown in Table 1.

In addition, the components described in the table are as follows.
(Hydrophilic resin)
Acetic esterified tapioca starch: Startack 17 (manufactured by GSL Japan)
Amphoteric starch: Cato3210 (NSC Japan)
Ester-modified starch: Corn Pole CP-5 (manufactured by Oji Cornstarch)
Cationic starch: EX-3 (manufactured by Nissho Chemical Co., Ltd.)
・ PVA: PVA110 (manufactured by Kuraray)
(Sizing agent: external additive)
Anionic styrenic resin: manufactured by Arakawa Chemical Industries, Polymeron 351S
Cationic styrenic resin: Polymeron 360 manufactured by Arakawa Chemical Industries
・ PVA: PVA110 (manufactured by Kuraray)
In Example 16, a mixture of 70 parts by mass of an anionic styrenic resin and 30 parts by mass of a cationic styrenic resin was used. Moreover, in Example 17, 70 mass parts of anionic styrene resin and 30 mass parts of PVA were mixed and used.

[Evaluation]
Each printing paper obtained was evaluated by the following method. The evaluation results are shown in Table 1.

[Smoothness (seconds)]
It measured based on JIS-P8119.

[Cobb sizing degree (g / m ² )]
Based on JIS-P8140, the degree of bump size on the surface was measured.
In Example 1 only, the degree of bump sizing on the back surface was measured by the same method as described above. The degree of bump size was 180 g / m ² .
Since the degree of noise seems to be indistinguishable, only Example 1 is measured.

[Print gloss (%)]
The standard tack grade ink used for the IGT print aptitude test machine defined in JIS-P8129 was used, and printing was carried out using a KRK universal print aptitude test machine manufactured by Kumagaya Riki Kogyo Co., Ltd. The gloss after printing was measured based on the 75-degree specular gloss test method defined in JIS-P8142.

[saturation]
Flexographically printed with aqueous red flexographic ink. Also, nitrified cotton type ink (GFP color C180 silver manufactured by Dainichi Seika Kogyo Co., Ltd.) The number of seconds of outflow at 3 was adjusted to be 10 to 20 seconds, and printing was performed by a gravure method. The saturation after each printing was evaluated by (a ² + b ² ) ^1/2 in the L * a * b * color system of JIS-Z8730.

  As shown in Table 1, the printing paper of Examples 1 to 25 is excellent in printing gloss, and can obtain a printed matter with high saturation in both flexographic printing and gravure printing. It was shown to be excellent.

  As described above, the printing paper of the present invention can exhibit excellent printability for both gravure printing and flexographic printing. Therefore, the printing paper can be suitably used for various types of printing paper, and in particular, can be suitably used as printing paper for interior boxes.

DESCRIPTION OF SYMBOLS 10 Printing paper 1 1st pulp fiber layer 2 2nd pulp fiber layer 3 3rd pulp fiber layer 4 4th pulp fiber layer 5 5th pulp fiber layer 6 Hydrophilic resin layer 7 Coating layer

Claims (7)

A printing paper having two or more pulp fiber layers, the surface of which is coated with a coating liquid containing a sizing agent,
A printing paper, wherein a hydrophilic resin layer is interposed between a first pulp fiber layer located on the surface and a second pulp fiber layer laminated on the inside thereof.   The printing paper according to claim 1, wherein the hydrophilic resin layer is mainly composed of starch.   The printing paper according to claim 2, wherein the starch is acetate esterified starch. The printing paper according to claim 1, wherein the basis weight of the first pulp fiber layer is 15 g / m ² or more and 25 g / m ² or less.   The printing paper according to any one of claims 1 to 4, wherein the sizing agent is an anionic styrene resin.   The printing paper according to claim 5, wherein the content of the anionic styrene resin in the solid content of the coating liquid is 80% by mass or more. The printing paper according to any one of claims 1 to 6, wherein the first and second pulp fiber layers contain an internal sizing agent.

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