JP2002180395A - Multilayer coated paper sheet for offset printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multilayer coated paper sheet for offset printing having excellent blister resistance suitability for forced hot-air drying during printing. SOLUTION: This multilayer coated paper sheet for the offset printing is characterized in that a latex binder having <=65% gel content is contained in a coating layer in the lowermost layer and the internal bond strength in a base paper sheet of the multilayer coated paper sheet for the offset printing measured by interfiber bond tests using an internal bond tester described in the TAPPI practical test method UM403 is >=300 J/m2 in the multilayer coated paper sheet for the offset printing provided with at least tow or more layers of coating layers on one or both surfaces of the base paper sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer coated paper for offset printing, and more particularly to a multilayer coated paper for offset printing which has extremely excellent blister resistance to forced hot air drying during printing.

[0002]

2. Description of the Related Art In recent years, in the field of offset printing and its printed matter, demands for print operability and print quality have become more and more severe. In particular, in a rotary printing press having a forced hot air drying process, the printing speed is increasing year by year with the improvement of the printing equipment, and this is a problem as a problem. The resistance of the paper to blisters and the like is always strongly required to increase the productivity of the printing operation. Also, as for the print quality, a high level of paper quality for obtaining a more aesthetically superior printed matter is required without exhaustion.

As a technique for improving the print quality of coated paper for offset printing, several reports have been made on so-called multilayer coated paper for offset printing, in which at least two or more coating layers are provided on one or both sides of base paper. ing. For example, in Japanese Patent Application Laid-Open No. 9-67796, the gel content of the latex binder contained in the lower layer of the two-layer coated paper for printing is 75 to 90%, and the gel content of the latex binder in the upper layer is 30 to 60%. By stipulating it, we are trying to achieve both coating operability and blister resistance.

However, latex binders having a gel content as high as 75 to 90% are not suitable for sufficiently exhibiting blister resistance even though they are slightly better in terms of mechanical stability. It is obvious and known fact. Therefore, the design of the offset printing paper as described in JP-A-9-67796 is insufficient to exhibit excellent blister resistance.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-layer coated paper for offset printing which has extremely excellent blister resistance to forced hot air drying during printing.

[0006]

Means for Solving the Problems As a result of intensive studies on the above-mentioned problems, the present inventors have found that a specific latex binder is contained in the lowermost coating layer and the internal bond strength is adjusted to an appropriate range. It has been found that by defining this, a multilayer coated paper for offset printing having extremely excellent blister resistance can be obtained.

That is, the multilayer coated paper for offset printing of the present invention is a multilayer coated paper for offset printing having at least two coating layers provided on one or both sides of a base paper. Contains a latex binder having a gel content of 65% or less, and TAPPI practical test method UM40
3. The internal bond strength in the base paper of the multilayer coated paper for printing, measured by a fiber-to-fiber bond test using an internal bond tester described in 3, is 300 J / m ² or more. .

Further, in the present invention, the moisture content of the base paper for coating and the multilayer coated paper for offset printing is not more than 5.0% by weight.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a multilayer coated paper for offset printing of the present invention will be described in detail. The present invention is a multilayer coated paper for offset printing provided with at least two or more coating layers on one or both sides of a base paper, wherein the lowermost coating layer contains a specific latex binder, and By providing the internal bonding strength of the base paper of the multi-layer coated paper, it has very excellent blister resistance.

The resistance to the blister property required for high-speed offset printing paper is largely attributable to the lowermost layer near the base paper. In the forced hot air drying during the printing process, moisture contained in the base paper evaporates and expands rapidly to generate a vapor pressure. At this time, if the undercoat layer has sufficient air permeability, the vaporized water can be quickly released, and the vapor pressure generated inside the high-speed offset printing paper can be reduced. When the air permeability of the coating layer is not sufficient, the strength of the base paper in the z-axis direction, that is, the internal bonding strength is reduced by the vapor pressure, and the base paper is broken, so-called blisters are generated.

An important factor that determines the air permeability of the coating layer is the gel content of the latex binder.

The gel content as used herein indicates the proportion of a portion insoluble in an organic solvent such as toluene or benzene, and indicates the degree of crosslinking of the polymer constituting the latex binder.

When the gel content is reduced, the air permeability of the coating layer is improved and the blister resistance is improved, but properties such as pick strength and print gloss are lowered.

Therefore, what is important for imparting the blister resistance is the internal bonding strength of the base paper of the multilayer coated paper for offset printing.

As mentioned above, blistering is a phenomenon that occurs with the rupture of base paper, but the blister resistance is greatly improved by maintaining the resistance to rupture of the base paper, that is, the internal bonding strength at a certain level. .

The basic design of the multilayer coated paper for offset printing in the present invention is to mix a latex binder having a low gel content with the lowermost layer, which plays a major role in the resistance to blisters, to provide air permeability, and An object of the present invention is to make the internal bonding strength of the base paper a certain level or more.

In the multilayer coated paper for offset printing according to the present invention, the latex binder in the lowermost coating layer has a gel content of 65% or less and the TAPPI practical test method U
The internal bond strength in the base paper of the multilayer coated paper for printing is 300 J / m ² or more, as measured by a fiber-to-fiber bond test using an internal bond tester described in M403.
Develops extremely excellent blister resistance.

Further, when the moisture content of the multilayer coated paper for offset printing having the above-mentioned structure is 5.0% by weight or less, it is possible to impart more excellent blister resistance to the printing paper.

The water content mentioned here is the weight% of water contained in the coated paper.

As described above, rapid evaporation of moisture contained in base paper due to forced hot air drying in the printing process is a factor of blister generation, and the moisture content of the coated paper greatly contributes to blister resistance. . When the moisture content of the base paper for coating and the multilayer coated paper for offset printing exceeds 5.0%, the excellent blister resistance of the multilayer coated paper for printing may not be exhibited.

In the present invention, the method of applying each coating layer including the lowermost layer and the uppermost layer is not particularly limited, and various metalized film transfers such as a size press, a gate roll, and a shim sizer, an air knife , Rods, blades, direct fountains, etc. are used as appropriate.

In the present invention, the pigment used in the coating liquid is not particularly limited. For example, purified natural mineral pigments such as various kinds of kaolin, talc, pulverized calcium carbonate, and composite composites such as satin white and lithophone are used. Examples of the pigment include semi-synthetic pigments such as pigments, titanium oxide, precipitated calcium carbonate, and alumina hydroxide, and synthetic pigments such as plastic pigments.

Examples of the starch used in the coating liquid include ordinary starch, oxidized starch, etherified starch, esterified starch, enzyme-modified starch, and cold water-soluble starch obtained by flash-drying them. Can be

The thickeners used in the coating solution include carboxymethyl cellulose, sodium alginate,
Water-soluble polymers such as methylcellulose, hydroxyethylcellulose, casein, and sodium polyacrylate; synthetic polymers such as polyacrylate and styrene-maleic anhydride copolymer; and inorganic polymers such as silicate.

Examples of the binder other than starch used in the coating solution include various copolymer latexes such as styrene-butadiene, acrylic and vinyl acetate, polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, polyacrylamide, and urea. Or melamine /
Examples include water-soluble compounds such as formalin resin, polyethyleneimine, polyamide polyamine / epichlorohydrin, natural products such as wax, casein and soybean protein, and cationized products thereof.

If necessary, various commonly used auxiliaries such as a dispersant, an antifoaming agent, a waterproofing agent, and a coloring agent, and those obtained by cationizing these various auxiliaries are preferably used. .

The base paper used in the present invention is LBK.
Chemical pulp such as P, NBKP, GP, PGWRMP,
Including mechanical pulp such as TMP, CTMP, CGP and various pulp such as waste paper pulp, various fillers such as light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, etc., sizing agent, fixing agent, retention agent, paper strength Various compounding agents such as an enhancer can be suitably compounded, and the paper can be made in any of acidic, neutral and alkaline conditions.

As the base paper of the present invention, a base paper which has been size-pressed with a no-size press base paper, starch, polyvinyl alcohol or the like can be used. In addition, various types of calendering may be performed to obtain the required density and smoothness of the base paper.

In a series of operations, the coated and dried coated paper is subjected to various calender treatments as necessary.

The coating amount of the lowermost layer is expressed as a weight after drying,
Usually, it is 1 to 20 g / m ² , preferably ² to 15 g / m ² .

The addition amount of the latex binder contained in the lowermost coating layer is usually 1 to 30 parts by weight, preferably 3 to 20 parts by weight, based on the weight of all the pigments.

[0032]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. All parts and percentages in the examples are by weight unless otherwise specified.

<Blend of base paper> LBKP (freeness 330 to 440 mlcsf) 70 parts NBKP (freeness 390 to 490 mlcsf) 30 parts

<Internally added chemicals> Light calcium carbonate (* represented by ash content in base paper) * 8 parts Commercially available cationized starch 1.0 part Commercially available cationic polyacrylamide retention aid 0.03 parts Pulp and internal additives are as described above. Adjusted by blending, basis weight 70g /
the base paper of m ² and papermaking. In order to adjust the internal bond strength of the base paper, the pulp freeness was changed within the above range, and the press pressure of the wet part was also adjusted appropriately.

<Blending of lowermost layer coating liquid> Commercially available primary kaolin clay 50 parts Commercially available heavy calcium carbonate 50 parts Commercially available polyacrylic acid dispersant 0.1 part Latex binder 10 parts Commercially phosphorylated ester starch 10 parts Sodium hydroxide The base paper was adjusted to pH 9.6, and a coating liquid was prepared in the above-described composition, and the coating liquid was applied at a coating speed of 1200 m / min at a coating speed of 1200 m / min. ² was applied and dried.

For the obtained product, a soft calender finishing device (rigid roll: chilled roll having an outer diameter of 500 mm, elastic roll: resin roll having an outer diameter of 500 mm, linear pressure: 180 kg / cm, temperature: 80 ° C.) is applied to the obtained product. Calendering process was performed.

<Blending of Top Layer Coating Solution> Commercially available primary kaolin clay 50 parts Commercially available heavy calcium carbonate 50 parts Commercially available polyacrylic acid dispersant 0.1 part Latex binder 15 parts Commercially phosphorylated starch 3 parts Commercially available carboxymethyl cellulose 0.1 part of system thickener (CMC) adjusted to sodium hydroxide pH 9.6 Furthermore, the coating liquid of the above ratio was prepared, and the coating speed was 1600 m / min using a fountain application / blade type coating machine. At 10 g / m ² on one side and dried to obtain a multilayer coated paper.

The obtained multi-layer coated paper was subjected to an off-line super calendering apparatus (10 steps, rigid roll: chilled roll having an outer diameter of 400 mm, elastic roll: cotton roll having an outer diameter of 400 mm, linear pressure: 220 kg / c
m) was subjected to a calendering treatment to produce a multilayer coated paper for offset printing. Embodiments 1, 4 to 8 satisfy claims 1 and 2, and Embodiments 2 and 3 claim 1.
Only meet.

The multilayer coated papers for offset printing of Examples 1 to 8 and Comparative Examples 1 to 6 were evaluated by the following evaluation methods, and the results are shown in Table 1.

<Evaluation Method> (1) Blister Resistance A coated paper packaged with aluminum was immersed in an oil bath at 150 ° C. to 200 ° C. for a certain period of time, and scored according to the number and size of blisters generated (10 points). Perfect score). ○ The above was the subject of the invention. ◎ (very good): 10 points ○ (good): 7 to 9 points △ (normal): 4 to 6 points × (bad): 5 points or less

(2) Dry pick strength Using a RI printability tester, tack ink (tack value 2)
In the printing of 0), the paper peeling state was visually judged and evaluated (a maximum of 10 points).以上 The above was regarded as good. ◎ (very good): 10 points ○ (good): 7 to 9 points △ (normal): 4 to 6 points × (bad): 5 points or less

[0042]

[Table 1]

In the multilayer coated paper for offset printing obtained in Examples 2 and 3, the internal bond strength of the coated paper using a latex binder having an appropriate gel content in the lowermost layer is within the range of the present invention. With the prescribed design, very good blister resistance and pick strength are developed.
Furthermore, in the multilayer coated paper for offset printing obtained in Example 1 and Examples 4 to 8, by setting the moisture content of the coated paper within the range of the present invention, more excellent blister resistance can be obtained. The multi-layer coated paper for offset printing shown below was produced.

[0044]

According to the present invention, in a multilayer coated paper for offset printing,
In a multilayer coated paper for printing having at least two coating layers provided on one or both sides of the base paper, a base paper containing a latex binder having a gel content of 65% or less in the lowermost coating layer is referred to as a base paper. By defining the internal bond strength in an appropriate range, a multilayer coated paper for offset printing having extremely excellent blister resistance was obtained.

Claims (2)

[Claims] 1. A multilayer coated paper for offset printing having at least two coating layers provided on one or both sides of a base paper, wherein the lowermost coating layer contains a latex binder having a gel content of 65% or less in a lowermost coating layer. And the internal bond strength in the base paper of the multilayer coated paper for printing is 300 J / m ² or more as measured by a fiber-to-fiber bond test using an internal bond tester described in TAPPI practical test method UM403. Multilayer coated paper for offset printing characterized by the following. 2. The multilayer coated paper for offset printing has a moisture content of 5.0% by weight or less.
The multilayer coated paper for offset printing according to the above.