JPH11279990A - Coated paper for gravure printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low density coated paper for gravure printing, excellent in gravure printability, especially hardly causing dotting miss and excellent in ink-receivability. SOLUTION: This coated paper for gravure printing is characterized by forming a coated layer containing 3-15 wt.% hollow polymer particles, 0.3-1.5 wt.% starch esterified with phosphoric acid, and a non-alkali-thickening type styrene-butadiene latex. The percentage of hollowness of the hollow polymer particles are preferably >=40%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-density coated paper for gravure printing, which is suitable for gravure printing, in particular, has few misdots, is excellent in ink receptivity, and has excellent printing gloss.

[0002]

2. Description of the Related Art In recent years, visualization of printed matter has progressed, and quality requirements for coated paper for printing have been more and more strong. Especially,
Gravure printing is becoming more and more popular with the progress of color printing of magazines and the like. Although gravure printing is insufficient in gradation, a large amount of ink can be transferred, a high print density is obtained, and image reproducibility is excellent, so that a voluminous printed matter is obtained.

However, in order to obtain gravure printing aptitude, a surface having a high smoothness is formed, so that the density becomes high.
The weight of the print is too heavy. Further, since the thickness is difficult to obtain, there is a problem that the stiffness is lost and the publication is difficult to handle, and a low-density coated paper for gravure printing is required.

[0004] Since gravure printing is a system in which ink is transferred directly from the concave surface of a metal roll to the paper surface, the occurrence of misdots and poor reproducibility of halftone dots are liable to occur, which impairs gravure printing suitability, that is, impairs the appearance of printed matter. It is a major defect.

Misdots are phenomena in which the ink in the intaglio does not transfer to the paper surface. The main cause is that the paper surface does not have sufficient smoothness under the pressure between the plate cylinder and the impression cylinder.

[0006] In order to prevent phenomena that impair the aesthetic appearance of gravure printing and misdots, the purpose is to improve the surface smoothness of the paper to be printed, the cushioning property for enhancing the surface smoothness under pressure, and the ink absorption. 2. Description of the Related Art Conventionally, improvement of pigments and binders in base paper for coating and coated paper compositions, supercalender conditions, and the like have been studied.

In order to obtain a high cushioning property under pressure, the base paper for coating is examined by increasing the ratio of the pigment to be filled in the pulp, or processing the base paper by a size press or the like. As a study of a coated paper composition, blending of delaminated clay and talc as a pigment, blending of a soft styrene-butadiene copolymer as a binder, and the like are performed (for example, see JP-A-60-2).
No. 24895), and the like, for example, blending of calcium carbonate has been studied for the purpose of enhancing ink absorbency. In particular, many contrivances have been made on binders.

[0008] In particular, in order to easily crush the coating layer with a super calender and to easily obtain smoothness, the amount of the binder is reduced.
Use a soft styrene-butadiene latex with a low glass transition temperature (Tg) and avoid adding a water-soluble binder such as starch that forms a hard film after drying. To improve streak and bleeding, and to improve blade coater operability. For this reason, carboxymethylated cellulose, sodium alginate, alkali-dissolved acrylic emulsion, etc. may be used, but it is easy to produce a hard film when dried,
It is difficult to use a large amount because misdots are easily deteriorated. Generally, an alkali-thickened styrene-butadiene latex is often used. The alkali-thickened styrene-butadiene latex can improve water retention and avoid streaks without deteriorating misdots.

However, all of these measures increase the flexibility of the base paper and the coating layer, and as a result, the density of the coated paper increases during the supercalendering process. For this reason, in order to reduce the density of the coated paper for gravure printing, measures such as increasing the blending amount of ground wood pulp (GP) in the base paper and increasing the smoothness without increasing the density with a heat calender have been adopted. However, satisfactory results cannot be obtained because the whiteness is remarkably reduced, a satisfactory level of smoothness cannot be obtained, and the like.

As one method, Japanese Patent Application Laid-Open No. 1-24986
No. 1, JP-A-2-140271, JP-A-2-1402
No. 72, JP-A-3-33296 and JP-A-5-1
No. 25695, etc., it has been proposed to reduce the weight of coated paper for gravure printing while maintaining gravure printing suitability by blending hollow polymer particles in a coating layer. By blending hollow polymer particles, during calendering, promote the rearrangement of other pigments, especially kaolin,
It is thought that high smoothness is obtained, and since the hollow polymer particles have a hollow inside, the cushioning property is improved,
It is thought to contribute to the improvement of gravure printing suitability.

However, the viscosity of the coating liquid using the hollow polymer particles, particularly the high shear viscosity, tends to increase, and particularly when used in combination with an alkali thickening latex, the viscosity increases significantly and streaks easily occur with a blade coater. It is not possible to produce coated paper for gravure printing which has no problem in the surface of the paper.

[0012]

From the above, it can be seen that the gravure printing coating has a sufficiently low density and has excellent suitability for gravure printing, particularly a low incidence of misdots, and has excellent ink acceptability and coated paper surface properties. At present, it is difficult to produce coated paper with high productivity, and realization thereof is a major problem for those who produce coated paper.

[0013]

In view of this situation, the present inventors have developed a gravure printing coated paper having excellent unprecedented gravure printing suitability, ink acceptability, and coated paper surface with high productivity. As a result of intensive studies for the purpose of manufacturing, the present invention has been completed.

According to the present invention, three hollow polymer particles are formed on a base paper.
To 15% by weight of a non-alkali thickened styrene-butadiene latex,
A coated paper for gravure printing, characterized by providing a coating layer containing not more than 0.3% by weight and not more than 0.3% by weight.

The hollow ratio of the hollow polymer particles is 40%.
Based on the above, better results can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The coated paper for gravure printing of the present invention will be described in detail below. The hollow polymer particles used in the present invention are spherical organic polymer particles having an outer diameter of 0.4 to 2.0 μm and an outer shell thickness of 0.05 to 0.2 μm and having a hollow inside. The material is not particularly limited,
Styrene, styrene-acrylic copolymers and the like are common.

When the hollow polymer particles are incorporated into the coating layer,
Since the hollow polymer particles themselves have a lower density than other pigments, the density of the entire coating layer is reduced, and the density of the coated paper can be reduced. For example, kaolin has a density of 2.6 g /
cm ³ , whereas the hollow polymer particles have a diameter of 0.1 cm ³ .
A material around 6 g / cm ³ is obtained. In addition, by blending the hollow polymer particles, during calendering, it is considered that the rearrangement of other pigments, particularly kaolin, is promoted, and high smoothness is obtained, and the hollow polymer particles have a hollow interior. Therefore, it is considered that the cushioning property is improved and contributes to the improvement of the gravure printing suitability.

However, when the hollow polymer particles are used, the viscosity of the coating solution, particularly the high shear viscosity, tends to increase. Particularly, when the hollow polymer particles are used in combination with the alkali thickening type styrene-butadiene latex, the viscosity increases significantly and the streak is increased by the blade coater. And gravure printing coated paper having no problem in the coated paper surface shape can be produced.

When the pH is adjusted to 8 or more with an alkali agent such as sodium hydroxide or aqueous ammonia, a polymer chain containing a large number of carboxylic acid groups swells or partially dissolves, and the viscosity of the emulsion is reduced. It has the property of increasing at least twice the value at pH 6 or less, and maintains high water retention.

Although this mechanism has not been completely elucidated,
In the emulsion state, the hollow polymer particles are filled with an aqueous system in the emulsion state, and after application, the aqueous phase in the hollow section penetrates and dries to the outside in the drying process and becomes hollow, so the density is low even in the emulsion state. It is presumed that a highly carboxylated polymer as a by-product of the process penetrates into the external aqueous phase from the hollow part, interacts with other pigments and binders, and tends to cause soft agglomeration in the coating liquid. .

As a result, the high shear viscosity of the coating liquid increases, and coating defects such as streaks occur in the blade coater, resulting in deterioration of the coated paper surface.

In particular, the alkali-thickened styrene-butadiene latex generally used in the coating liquid of gravure-coated paper contains a large number of functional groups of sodium carboxylate such as sodium acrylate, so that it may be used in the aqueous phase. It is considered that soft aggregation easily occurs with the hollow polymer particle emulsion due to the influence of polyvalent metal ions and the like.

For this reason, by using a non-alkali thickening type styrene butadiene latex for the latex, the high shear viscosity is reduced and the suitability for the blade coater is improved but is insufficient. Thereby, satisfactory blade coater suitability can be obtained.

Although the mechanism is not clear, it is considered that the hollow polymer particles are easily separated due to a large difference in specific gravity from other pigments. It is considered that the esterified starch shows not only a protective colloid effect but also a dispersant effect.

When the amount of the phosphorylated ester exceeds 1.5% by weight, the high shear viscosity is rather increased and the suitability for the blade coater is deteriorated. If the content is less than 0.3% by weight, the effect of improving the suitability of the blade coater cannot be obtained.

When the amount of the hollow polymer particles is less than 3% by weight, the effect of improving the gravure printing suitability cannot be obtained, and when the amount exceeds 15% by weight, the high shear viscosity increases and the suitability for the blade coater deteriorates.

The higher the hollow ratio of the hollow polymer particles is, the more the cushioning property is improved and the suitability for gravure printing is improved. The upper limit of the hollow ratio is restricted by the method of producing the hollow polymer particles. At present, the upper limit of the hollow ratio is about 60% in commercially available hollow polymer particles that can be practically used.

In the coating liquid used for the coated paper for gravure printing of the present invention, a raw material for paper processing can be generally used in addition to the raw material constituting the present invention.

Examples of the pigment include heavy calcium carbonate, light calcium carbonate, satin white, talc, titanium oxide, aluminum hydroxide, zinc oxide, zeolite, barium sulfate, amorphous silica, plastic pigment and the like.

In these coating liquids, various commonly used auxiliaries such as a dispersant, a thickener, a water retention agent, a defoaming agent, a waterproofing agent, and a coloring agent can be used as needed. .

In the present invention, as a device for applying a coating liquid, a flooded nip type, a jet fountain type,
One- or two- or three-layer coating with various coating equipment such as short dwell type blade coater, rod blade coater, roll coater, air knife coater, bar coater, die coater, curtain coater, etc. The coated paper is dried for each layer coating, and in some cases, coated with an on-machine coater installed on a paper machine for forming a base paper.

The rough surface roll treatment of the present invention is installed immediately after leaving the dryer in the coating apparatus, and may be subjected to treatment immediately after drying. Further, prior to or during the rough surface roll treatment of the present invention, a treatment of spraying steam or fine water droplets on the coated paper may be performed.

The base paper used for the coated paper for gravure printing of the present invention is a chemical pulp such as LBKP, NBKP, or the like.
Including various pulp such as mechanical pulp such as P, PGW, TMP, CTMP, CMP and CGP, waste paper pulp such as DIP, various fillers such as light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, etc., sizing agent, It contains various additives such as fixing agent, retention agent, cationizing agent, paper strength agent, etc., and can be used for acidic, neutral and alkaline papermaking medium paper, high quality base paper, recycled paper base paper, etc. No.

As the base paper of the present invention, a base paper which is size-pressed with no-size press base paper, starch, polyvinyl alcohol, or the like, or coated with an undercoat pigment using a gate roll coater, various blade coaters, or the like can be used.

[0035]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but of course, the present invention is not limited to these Examples. In the examples, parts and% mean parts by weight and% by weight, respectively. The various measured values in the examples and comparative examples were obtained by the following methods.

<High shear viscosity> Measured with a cone plate type high shear viscosity meter manufactured by Rheology Japan. 100
0 rpm. Measured apparent viscosity (Pa seconds) at 100P
If the time is longer than a second, the operability of the blade coater is significantly deteriorated.

<Suitability of blade coater> The streak frequency and the bleeding state were evaluated visually with a five-point scale. Below level 2, no marketable product is obtained.

<Smoother smoothness> The smoother smoothness (kPa) of the base paper and the matte-coated paper was measured using a smoother smoothness tester manufactured by Toei Denshi.

<Blank gloss level> Blank gloss level (%) is determined by JI
Measured at an angle of 75 ° according to SP8142.

<Miss dot ratio> The misdot ratio was measured using a printing station type gravure printing suitability tester manufactured by Toyo Ink Industry Co., Ltd.
G91 (ink) ink with toluene in Zahn Cup # 3 1
The printing speed was 60 m / min. With a plate having a dot area ratio of 150% of 10 lines according to the viscosity of 5 seconds. Printed at a linear pressure of 15 kg / cm. Evaluation was made on a five-point scale based on visual perception. If the level is less than 3, the image quality is unacceptable to the user as a gravure print.

Example 1 [Preparation of base paper] Light calcium carbonate 5 was added to a pulp composed of 50 parts of LBKP, 20 parts of NBKP and 30 parts of GP.
Parts, commercially available alkyl ketene dimer-based internal sizing agent 0.1
Parts, a commercial cationized starch 0.2 part, a commercial cationic polyacrylamide part A pulp slurry to which a retention improver 0.03 part was added was made into a paper so as to have a basis weight of 70 g / m ² , and the starch was subjected to size press. the aqueous solution was two-sided per 2g / m ² coated with, is smoother smoothness on-machine calender 8
The base paper was manufactured by adjusting the linear pressure so as to be 2 kPa and performing a calendar process.

[Preparation of coating liquid]
A coating solution having a solid content of 60% was prepared. (Composition of coating liquid) Commercially available second-class kaolin (Ultracoat, manufactured by Enkelhard Company) Average particle size: 2.9 μm 90 parts Commercially available hollow polymer particles (HP1055, manufactured by Rohm Ant Haas) 10 parts Commercially available polyacrylic acid-based dispersant (Toa Gosei) Alon T-40 manufactured by Kagaku Co., Ltd. 0.1 part Commercially available non-alkali thickened styrene-phthalic acid-based latex (L1301 manufactured by Asahi Kasei Corporation) 9 parts Commercially available phosphorylated starch (MS4600 manufactured by Nippon Shokuhin Kako Co., Ltd.) 1.0 part Calcium stearate 0.4 part Calcium hydroxide: adjusted to pH 9.5

[Production of Coated Paper] The above coating liquid was applied to the above-mentioned base paper for coating by using a flooded nip type blade coater (manufactured by Mitsubishi Heavy Industries, Ltd.) at a coating speed of 80 using a bevel blade method.
0 m / min. The coating was performed so that the coating amount on one side was 14 g / m ² , and the coating was dried to prepare a coated paper.

[Super processing of coated paper] The coated paper was processed by a super calender under the following conditions. <Super calendar condition>-Number of stages: 12-Rigid roll: chilled roll, outer diameter 400 mm-Filling roll: cotton roll, outer diameter 420 mm-Processing speed: 400 m / min.・ Line pressure: 200kg / cm

After the super-processed product was super-moistened at 20 ° C. and 65% relative humidity, the suitability for gravure printing and the physical properties of paper were measured. The composition and quality are shown in Table 1 below. The non-alkali thickened styrene-butadiene latex is an SB latex in the table.

Examples 2 to 6 The same formulation as in Example 1 except that the formulation of the coating liquid was described in Table 1,
Manufactured under manufacturing conditions.

Comparative Examples 1 to 3 Except for the composition of the coating liquid described in Table 2 below, production was carried out under the same conditions as in Example 1 to obtain coated paper for gravure printing.

Comparative Example 4 A coated paper for gravure printing was obtained in the same manner as in Comparative Example 3 except that a coating solution not containing the hollow polymer particles described in Table 2 was used.

[0049]

[Table 1]

[0050]

[Table 2]

From the results shown in Tables 1 and 2, Example 1 was obtained.
In Nos. To 9, a matte gravure coated paper having excellent gravure suitability could be obtained. On the other hand, in Comparative Examples 1 to 3, the operability of the blade coater was low, and the coated paper was not successfully formed. In Comparative Example 4, when the hollow polymer particles were not blended, there was no problem in blade coater operability and gravure printing suitability (misdot), but the density could not be reduced to 1.32.

[0052]

As apparent from the above, according to the present invention, it is possible to obtain a coated paper for gravure printing having a sufficiently low density and excellent gravure printing suitability with few miss dots.

Claims (2)

[Claims] 1. A method in which three to one hollow polymer particles are provided on a base paper.
A gravure printing method comprising providing a coating layer containing 5% by weight, a non-alkali thickened styrene butadiene latex, and 1.5% by weight or less and 0.3% by weight or more of a phosphorylated starch. Coated paper. 2. The coated paper for gravure printing according to claim 1, wherein the hollow ratio of the hollow polymer particles is 40% or more.