JPH06280196A - Coated paper for web offset printing - Google Patents

Abstract

PURPOSE:To provide a coated paper excellent in smoothness and ink receptivity and exhibiting an excellent blister resistance especially when used for web offset printing. CONSTITUTION:This coated paper for web offset printing has two or more coated layers composed mainly of a pigment and an adhesive. Among these layers, the under layer in contact with the base paper contains inorganic porous spherical particles.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to coated paper. More specifically, the present invention relates to a coated paper having high smoothness, excellent ink acceptability, and excellent blister resistance particularly in offset rotary printing applications.

[0002]

2. Description of the Related Art In recent years, visualization of printed matter has been strongly desired for coated paper for printing. Further, in printing, the speed of printing has been increased, and coated paper capable of withstanding the demand has been required. Rotational offset printing is an excellent printing method from the viewpoint of speeding up, but it is required to have higher performance with excellent wet strength and blister resistance in addition to sheet-fed offset printing suitability.

The difference between sheet-fed printing and rotary printing is that the latter requires instantaneous drying of the printed ink. Paper with poor blister resistance in this high-temperature, high-speed dryer is used as printing paper. Not suitable. The blister phenomenon occurs when the water content of the coated paper instantly becomes steam due to high temperature and internal pressure is generated.

In order to impart this blister resistance, a method of using a specific latex as an undercoat for base paper as described in JP-A-62-162097, JP-A-1-15.
No. 6596, a method of using a specific size press liquid as a base paper undercoat, further improving the internal strength of the paper itself, improving the composition of the paper coating composition and paper coating technology, and improving the adhesive for pigments However, further improvements have been demanded with the recent increase in speed of printing machines.

However, each of the measures has its own problems. In particular, the use of a coating liquid often causes deterioration of liquidity and impairs operability. In terms of visualization of printed matter, it is important to have smoothness and high gloss in addition to opacity. There are several known methods for obtaining smoothness. For example, it is also effective to take measures from the aspect of blending, such as increasing the amount of papermaking filler in the base paper, and to apply an undercoat to the base paper. However, if such measures are taken when actually manufacturing coated paper, the drawbacks associated therewith also appear, and it is difficult to make the desired coated paper a reality. For example, the smoothness, gloss, printability, blister resistance, and coating layer strength of the finally obtained coated paper greatly differ depending on the coating method and liquid composition of the undercoat coating.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above blister problem and to provide a coated paper for offset rotary printing which has high smoothness and excellent ink acceptability.

[0007]

The inventors of the present invention have conducted extensive studies to solve these problems, and as a result, provided a layer which should be called a heat shield layer between the base paper layer and the coating layer. The inventors have found that blistering resistance can be improved by concentrating heat on the coating layer, and completed the present invention.

That is, the present invention has at least two or more coating layers containing a pigment and an adhesive as main components, and the subbing layer in contact with the base paper has a total pore volume of 0.4 ml / g.
The coated paper for offset rotary printing is characterized by containing the spherical porous inorganic particles having the above average surface pore diameter of 0.005 μm or more.

The specific spherical porous inorganic particles of the present invention have a total pore volume of 0.4 ml / g or more and a surface pore average diameter of 0.005 μm or more, and more preferably. In addition to these characteristics, those having an average particle diameter of 3 μm or less and a specific surface area of 400 m ² / g or more can be mentioned. Hollow pigments satisfying the above characteristics are also preferable.

The specific spherical porous inorganic particles of the present invention are obtained by, for example, in an inorganic chemical reaction "A-10B → C-10D" which proceeds in an ordinary aqueous solution, one of the aqueous solutions of the compounds A and B is used as an organic solvent. It is obtained by a method in which the precipitation-forming reaction of A or B is allowed to proceed on the surface of this emulsion by mixing with and emulsifying it to form a water-in-oil emulsion. It also includes the case where it becomes porous when dried. Japanese Patent Laid-Open Nos. 63-229140 and 6
Although the method of JP-A-3-258642 is mentioned as an example, porous inorganic particles which are not hollow can be obtained by the same method.

The shape produced by the above reaction is almost spherical, but more specifically, it is judged by the shape obtained from an electron micrograph, and if it is regarded as an ellipse, the major axis a and the minor axis b are ( a ² -b ^{2) 0.5} / a by eccentricity expressed considers substantially spherical 0.9 or less. Porous means that pores are distributed on the surface and inside of the spherical pigment.

Examples of the inorganic material forming the spherical porous inorganic particles include alkaline earth metal carbonates, alkaline earth metal silicates and metal oxides. Specific examples include calcium carbonate, barium carbonate, calcium silicate, magnesium silicate, silica (anhydrous silicic acid), alumina and zirconia.

These spherical porous inorganic particles can be used in combination of two or more kinds. The amount of the spherical porous inorganic particles in the undercoat layer is 3 to 80% by weight or more, preferably 5 to 60% by weight or more, though the amount used is not necessarily limited depending on the form of use.

The undercoat layer is obtained by dispersing spherical porous inorganic particles in an adhesive and water, applying the dispersion on a base paper, and drying.

Examples of the adhesive that can be used in the undercoat layer in the present invention include gelatin, casein, starch derivatives, polyvinyl alcohol, modified polyvinyl alcohol, hydroxycellulose, methylcellulose, carboxymethylcellulose, polyvinyl acetate, polyurethane, ethylene-acrylic acid alkali. Salt copolymer, ethylene-maleic anhydride alkali salt copolymer, ethylene-vinyl acetate copolymer,
Styrene-maleic acid copolymer, styrene-butadiene copolymer acrylic ester resin, acrylic ester-vinyl acetate copolymer, acrylic acid amide-acrylic ester-methacrylic acid terpolymer such as natural or Examples thereof include synthetic binders and latexes. These adhesives can be used in combination of two or more kinds, if necessary.

The undercoat layer may contain other pigments, dyes, dispersants, thickeners, water retention agents, defoaming agents, and water resistant materials, if necessary, within a range that does not significantly impair the heat insulating property. Various commonly used auxiliaries such as an agent and a pH adjuster can be appropriately used.

In the present invention, the coating amount of the undercoat layer is effective if it is coated at 1 g / m ² or more, but if it is coated too much, the characteristics as coated paper, for example, the thickness of the paper Therefore, if the base paper is thinned and the thickness of the coated paper is made uniform, the strength of the waist will be a problem. Therefore, a coating amount of 3 to 15 g / m ² per side is preferable, and the amount of the fine hollow particles added may be appropriately adjusted within the above range depending on the coating amount.

For the coating layer provided on the undercoat layer, a commonly used paper coating composition is used. That is, in addition to an adhesive that can be used for the undercoat layer, kaolin, mica, barium sulfate, titanium oxide, heavy and light calcium carbonate, clay, mineral pigments such as satin white, talc, permanent white, ocher carbon black, Pigment substances such as aluminum powder, polyethylene, polystyrene,
Acrylic styrene, plastic pigments such as ethylene-vinyl acetate, urea-formaldehyde resin, organic pigments such as binder pigments, water resistance improvers, water resistance reaction accelerators, pigment dispersants, clay modifiers, defoamers, lubricants,
Coloring pigments, fluorescent dyes, pH adjusters and the like can be arbitrarily selected and blended for use. If necessary, spherical porous inorganic particles can be used in the coating layer.

The undercoat layer and the coating layer are provided on the base paper by using a usual coating method. For example, various blade coaters, roll transfer coaters, air knife coaters, bar coaters, rod blade coaters, short dwell coaters, curtain coaters, die coaters and the like can be used to coat the base paper using conventionally known coating methods. Among these, in the present invention, it is preferable to use a coating method suitable for high-speed coating such as an air knife coater, a blade coater, a curtain coater, and a bill blade coater. Particularly for the coating layer, it is desirable to select a coating method suitable for high-speed coating such as an air knife coater and a blade coater and having excellent surface smoothness.

The undercoat layer can be provided on-machine for the papermaking of the base paper by using a so-called "size press" system.

The overcoating is usually carried out after the base paper after the undercoating has been subjected to the drying step, but the basepaper after the undercoating is directly overcoated using the above-mentioned various coating devices without the drying step. It also includes a case of a so-called wet-on-wet coating method of applying a liquid. According to this method, since a drying process is not required for each coating, the process is simplified, and since the coating layer is dried at once, it is possible to further reduce the drying load. It brings great advantages in terms of aspects.

The base paper coated with the undercoat and the overcoat is dried by a method similar to the conventional method, wound, and then calendered to finish. The apparatus for carrying out the calendering process is not particularly limited, and various calendering devices such as a super calender, a gloss calender and a soft calender are used.

[0023]

EXAMPLES The effects of the present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. The various measured values in the examples are obtained by the following methods. 1) Smoothness: Measured with a smoother smoothness tester (manufactured by Toei Denshi Kogyo Co., Ltd., model SM-6A). (Unit: mmHg) 2) White paper glossiness: Measured at an angle of 75 degrees in accordance with JIS P8142. (Unit:%) 3) Glossiness of heavy color printing: Printed on a Roland offset printing machine and left at room temperature for one day
The gloss was measured at an angle of 60 degrees with respect to a solid printed portion of four-color overprinting of magenta, cyan, and yellow. (unit:
%) 4) Ink acceptability: A commercially available offset ink of 0.1 CC was printed on a coated paper test piece with an RI printer, and the transfer state was visually judged from 5 (excellent) to 1 (poor). The higher the value, the better the ink acceptability. 5) Blister resistance: A commercial offset rotary printing ink was printed on both sides of the test piece by an RI printing machine, and the test piece was wrapped with an aluminum foil at a selected temperature (200 to 3).
It was immersed in silicone oil (00 ° C.) and the appearance of the blister was visually judged. ⊚: Almost no blister is generated. ○: Some blister is seen. Δ: Blister is seen. ×: Blister is often generated. In addition, "%" and "part" used in the following examples mean "weight%" and "weight part."

<Composition of Topcoat Coating Liquid> Commercially available secondary kaolin (ultra coat): 70 parts Commercially available wet ground calcium carbonate (carbital 90): 3
0 parts Commercial polyacrylic acid type dispersant (Aron T-40):
0.1 part ・ Commercial phosphate esterified starch (MS-4600): 5 parts ・ Styrene-butadiene latex (gel content: 30
% By weight): 11 parts-Calcium stearate: 0.3 parts-Sodium hydroxide: 0.15 parts-Coating liquid solid content concentration: 63% The above composition was dispersed to prepare a top coating liquid.

Examples 1 and 2 Sintered kaolin (Astrapeque, Georgia Kaolin) and spherical porous silica (Suzuki Yushi Kogyo, E-2)
The ratio of C) was changed as shown in Table 1 and dispersed in an aqueous solution of sodium hexametaphosphate to obtain a 45% slurry. A 20% solution of commercially available phosphorylated esterified starch (MS-46
00) and 15 parts of styrene-butadiene latex (gel content: 25%) were added and sufficiently mixed to obtain an under liquid.

Both sides of a base paper having a basis weight of 60 g / m ² (absolutely dried) were coated with an undercoat liquid so that one side was 5 g / m ² . Both sides were coated with a top coating liquid so that the amount per side was 8 g / m ^2, and dried to obtain coated paper. The obtained coated paper was supercalendered at a linear pressure of 100 kgf / cm. The results are shown in Table 1.

Example 3 Example 3 was repeated except that spherical porous calcium carbonate having a specific surface area of 300 m ² / g (calcium charcoal A) was used in place of the spherical porous inorganic particles of Example 1 and the composition shown in Table 1 was used. A coated paper was obtained in the same manner as in 1. The results are shown in Table 1.

Example 4 Instead of the spherical porous inorganic particles of Example 1, spherical porous hollow silica (B-6C manufactured by Suzuki Yushi-Seiya Kogyo Co., Ltd.) was used.
A coated paper was obtained in the same manner as in Example 1 except that the composition was changed to. The results are shown in Table 1.

Example 5 In Example 1, the coating amount of the under liquid was 10 g / m ^2.
A coated paper was obtained in the same manner as in Example 1 except for the above. The results are shown in Table 1.

Comparative Example 1 For comparison, a coated paper was obtained in the same manner as in Example 1 except that the total amount of the spherical porous silica in the under liquid of Example 1 was replaced with Astrapeque. The results are shown in Table 2.

Comparative Example 2 A coated paper was obtained in the same manner as in Example 1 except that the spherical porous silica in the under liquid of Example 1 was replaced with solid calcium carbonate. The results are shown in Table 2.

Comparative Example 3 A coated paper was prepared in the same manner as in Example 2 except that the spherical porous silica in the under liquid of Example 2 was replaced with borosilicate glass hollow particles (K-330 manufactured by Nippon Silica Industry Co., Ltd.). Obtained. The results are shown in Table 2.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

As is apparent from the above, by incorporating spherical porous inorganic particles in the undercoat layer, it is possible to prevent heat from entering the base paper layer and improve the blister suitability. Furthermore, by preventing heat from penetrating into the base paper layer and concentrating the heat on the upper layer than the undercoat layer, it is possible to enhance the drying efficiency of the offset ink, and it is possible to perform ink drying with smaller energy, reducing the drying load. Can be a substrate.

Claims (3)

[Claims] 1. An underlayer having at least two or more coating layers containing a pigment and an adhesive as a main component, of which the underlayer in contact with the base paper has a total pore volume of 0.4 ml / g or more,
A coated paper for offset rotary printing characterized by containing spherical porous inorganic particles having an average diameter of surface pores of 0.005 μm or more. 2. The spherical porous inorganic particles have an average particle diameter of 3 μm.
The coated paper for offset rotary printing according to claim 1, which has a specific surface area of 400 m ² / g or more. 3. The coated paper for offset rotary printing according to claim 1, wherein the spherical porous inorganic particles are hollow bodies.