JPH06280195A - Coated paper for web offset printing - Google Patents

Abstract

PURPOSE:To produce 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 coating layers composed mainly of a pigment and an adhesive. Among these layers, the under layer in contact with the base paper contains organic porous particles of <=5mum outer diameter.

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. It was found that blistering resistance can be improved by concentrating heat on the coating layer, and the present invention has been completed.

That is, the present invention provides a method for producing a coated paper, which comprises coating a base paper obtained by blending and preparing pulp fibers and then making a paper, with a coating composition containing a pigment and an adhesive as main components. A layer containing at least two layers of a pigment and a binder, and the layer in contact with the base paper is a layer containing organic porous particles having an outer diameter of 5 μm or less (hereinafter referred to as an undercoat layer). Is a coated paper for offset rotary printing.

That is, the organic porous particles are provided as an undercoat layer by simply coating the undercoat with a pigment.
In addition to showing the effect of filling the unevenness of the base paper to make a smoother surface like the paper layer, the heat of high temperature drying during printing will penetrate into the base paper layer due to the heat insulating property of the porous particles. It is considered that it has an effect of improving the blister resistance, and further, due to the elasticity of the porous particle layer, the adhesiveness with the printing roll is improved and excellent printing reproducibility is exhibited. it is conceivable that.

In the present invention, the organic porous particles preferably have an outer diameter of 5 μm or less, preferably 3 μm or less, more preferably 1.5 μm or less. When the particle size is 5 μm or more, the underlayer becomes non-uniform, which affects the mottling. Further, since it is bulky, it causes an inconvenience such as an increase in thickness more than necessary.

Examples of the organic porous particles used here include polystyrene, poly-α-methylstyrene, poly-β-methylstyrene, and other styrene resins, polymethyl methacrylate, polyethyl methacrylate, polymethacrylic acid. Acrylic resins such as isopropyl, polyisobutyl methacrylate, polyacrylonitrile, pyrimethacrylonitrile, polyvinyl chloride, polytetrafluoroethylene, polyvinyl alcohol, poly-o-vinylbenzyl alcohol, poly-m-vinylbenzyl alcohol,
Poly-p-vinylbenzyl alcohol, polyvinyl formal, polyvinyl acetal, polyvinyl propional, polyvinyl butyral, polyvinyl isobutyral, polyvinyl tertiary butyl ether, polyvinyl pyrrolidone, polyvinyl carbazole, cellulose acetate, cellulose triacetate, polycarbonate, and their co-weights. Examples include coalescence. Such porous particles can be obtained by aggregating fine particles in the polymerization process.

The underlayer is obtained by dispersing the porous particles in a binder and water, applying the dispersion on a base paper, and drying.

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

In addition, other pigments, dyes, dispersants, thickeners, water retention agents, antifoaming agents, water resistant agents, etc. may be added to the under layer, 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 amount of the organic porous particles used is preferably 5% by weight to 80% by weight with respect to the under layer. If it is 5% by weight or less, the effect as a heat insulating layer is not obtained, and in such a case, there is no effect on the blister resistance. Also, 80
If the content is more than the weight%, the amount of the adhesive becomes small, which causes a problem in strength.

The coating amount of the under layer in the present invention 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 If the base paper is thinned and the thickness of the coated paper is made uniform due to the increase in thickness, a problem will occur in the strength of the waist. For this reason 3
A coating amount of ~ 15 g / m ² is preferable, and depending on the coating amount,
The amount of the fine hollow particles added may be appropriately adjusted within the above range.

The coating layer provided on top of the under layer is
Commonly used paper coating compositions are used.
That is, other than the adhesive that can be used for the under 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, 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 , An antifoaming agent, a lubricant, a coloring pigment, a fluorescent dye, a pH adjusting agent and the like can be arbitrarily selected and blended. In addition, organic fine hollow particles can be used in the coating layer, if necessary.

The under 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, etc. can be coated on the base paper using conventionally known coating methods. Of 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 under layer can also be provided on-machine for the papermaking of the base paper by using the 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. The case of a so-called wet-on-wet coating method of applying a liquid is also included. 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, the drying load can be further reduced, which is a great advantage in operation. .

The base paper coated with the undercoat and the overcoat is dried by a 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.

[0022]

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."

Example 1 <Composition of top coating liquid> Commercially available secondary kaolin (ultra coat): 70 parts Commercially available wet heavy 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: 55
% By weight): 11 parts-Calcium stearate: 0.3 part-Sodium hydroxide: 0.15 part-Concentration of solid content of coating liquid: 63% The above composition was dispersed to prepare a top coating liquid.

<Under-A liquid> Commercially available porous particles (trade name: XMRP-100, porous particle emulsion consisting of styrene / acrylic copolymer manufactured by Mitsui Toatsu Chemicals, particle diameter about 1.0 μm): 100 parts -Styrene / butadiene copolymer (solid content 50%): 5
0 part-Water: 20 parts The above composition was stirred to prepare <under-A liquid>.

On a base paper having a basis weight of 60 g / m ² (absolutely dry), an under liquid A is applied to both sides using a size press so as to be 5 g / m ² on one side, dried, and then a top coating solution. Was coated on both sides using a blade coater so that one side was 8 g / m ^2, and dried to obtain coated paper. The coated paper obtained is
Super calendar processing was performed at a processing speed of 300 m / min and a linear pressure of 30 kgf / cm. The measurement results are shown in Table 1.

Example 2 In Example 1, the porous particles had a particle size of 0.5 μm.
(Product name: XMRP-140, manufactured by Mitsui Toatsu Chemicals)
A coated paper was obtained in the same manner as in Example 1 except that was used. The measurement results are shown in Table 1.

Example 3 A coated paper was obtained in the same manner as in Example 1 except that the composition of the under liquid was changed as follows.
The measurement results are shown in Table 1. <Under-B liquid> Commercially available porous particles (trade name: XMRP-100, porous particle emulsion consisting of styrene / acrylic copolymer manufactured by Mitsui Toatsu Chemicals, particle diameter about 1.0 μm): 100 parts Vinyl Acetate Copolymer Emulsion (solid concentration 50
%): 30 parts Water: 85 parts The above composition was stirred to prepare <under-B solution>.

Example 4 In Example 3, the porous particles had a particle size of 0.5 μm.
(Product name: XMRP-140, manufactured by Mitsui Toatsu Chemicals)
A coated paper was obtained in the same manner as in Example 3 except that was used. The measurement results are shown in Table 1.

Comparative Examples 1-2 For comparison, non-porous CaCO ₃ and styrene / acrylic particles (particle diameter 1.0 μm) were used in place of the porous particles in the under liquid A of Example 1, and The conditions were the same as in Example 1. The measurement results are shown in Table 1.

[0030]

[Table 1]

[0031]

As is clear from the above, the use of organic porous particles in the under layer prevents heat from entering the base paper layer,
Blister suitability can be improved. Furthermore, since heat is prevented from entering the base paper layer and the heat is concentrated on the upper layer rather than the under layer, the drying efficiency of the offset ink can be improved, and the ink can be dried with smaller energy, reducing the drying load. Can be a substrate.

Claims (1)

[Claims] 1. A method for producing a coated paper comprising applying a coating composition containing a pigment and an adhesive as a main component onto a base paper obtained by blending and preparing pulp fibers and then making a paper. A coated paper for offset rotary printing, characterized in that at least one layer containing a pigment and a binder is provided, and the layer in contact with the base paper contains organic porous particles having an outer diameter of 5 μm or less.