JP4030259B2 - Multilayer coated paper for offset printing - Google Patents

Description

【００４５】
【表２】

【００４６】
実施例１〜４では、適切なゲル含有量と平均粒子径のラテックスバインダーと上記数式１〜３を満たした適切な粒度分布および配合量の顔料を最下層に用いることで、良好な耐ブリスター性とピック強度を発現している。さらに、実施例５〜７では、上記数式４〜６を満たした適切な粒度分布および配合量の顔料を最上層に用いることで、優れた白紙光沢と印刷光沢を示すオフセット印刷用多層塗工紙を製造できた。
【００４７】
【発明の効果】
オフセット印刷用多層塗工紙において、最下層に含まれるラテックスバインダーのゲル含有量と平均粒子径、加えて最下層および最上層の塗工層に含まれる粒度分布と配合量を同時に規定することで最下層が担うブリスター性の耐性と最上層の担う白紙光沢および印刷光沢の発現を往来にない非常に高い次元において両立し発揮することができる。[0001]
BACKGROUND 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 that has good blister resistance to forced hot air drying during printing, and has excellent white paper gloss and printability.
[0002]
[Prior art]
In recent years, in the field of offset printing and its printed matter, demands for printing operability and printing quality have become increasingly severe. In particular, in a rotary printing press having a forced hot air drying process, as the printing equipment is improved, the printing speed increases every year. The resistance of paper to wisteria and blisters is always strongly required to increase the productivity of printing operations. In addition, regarding the print quality, a high level of paper quality is required to obtain a printed material that is more aesthetically pleasing.
[0003]
As a technique for improving the printing quality of the coated paper for printing, several so-called offset printing multilayer coated papers in which at least two coating layers are provided on one side or both sides of the base paper are disclosed. For example, JP-A-9-67796 defines the gel content of the latex binder contained in the lower layer of the two-layer coated paper for printing as 75 to 90% and the gel content of the upper layer latex binder as 30 to 60%. By doing so, we are trying to achieve both coating operability and blister resistance.
[0004]
However, it is clear that latex binders with a high gel content of 75 to 90% are inappropriate for sufficiently exhibiting blister resistance, even if they are slightly better in terms of mechanical stability. It is a known fact. Therefore, the design of the offset printing paper as described in JP-A-9-67796 is insufficient for exhibiting excellent blister resistance.
[0005]
[Problems to be solved by the invention]
An object of the present invention relates to a multilayer coated paper for offset printing, and in particular, a multilayer coated paper for offset printing which has good blister resistance against forced hot air drying during printing and has excellent picking strength, blank paper gloss and printing gloss. It is to provide.
[0006]
[Means for Solving the Problems]
As a result of intensive studies on the above problems, the present inventors have invented the multilayer coated paper for offset printing of the present invention.
[0007]
That is, the multilayer coated paper for offset printing of the present invention is a multilayer coated paper for offset printing in which at least two coating layers are provided on one side or both sides of the base paper, and the lowermost coating layer contains a gel. A latex binder having an amount of 65% or less and an average particle diameter of 130 to 250 nm, the composition ratio of the pigment constituting the lowermost coating layer satisfies the following formulas 1 to 3, and the uppermost coating layer The composition ratio of the pigment that constitutes satisfies the following mathematical formulas 4 to 6.
[Expression 7]
40 ≦ A + B ≦ 100 (Formula 1)
[Equation 8]
0 ≦ A ≦ 100 (Formula 2)
[Equation 9]
0 ≦ B ≦ 100 (Formula 3)
[Expression 10]
40 ≦ C + D ≦ 100 (Formula 4)
## EQU11 ##
0 ≦ C ≦ 100 (Formula 5)
[Expression 12]
0 ≦ D ≦ 100 (Formula 6)
A: The content ratio (% by weight) of kaolin with respect to all pigments, and 88% by weight or less having a particle diameter of 2 μm or less.
B: The content ratio (% by weight) of heavy calcium carbonate with respect to all pigments, and 83% by weight or less of particles having a particle diameter of 2 μm or less.
C: The content ratio (% by weight) of kaolin with respect to the total pigment, and 95 % by weight or more containing particles having a particle size of 2 μm or less.
D: The content ratio (% by weight) of heavy calcium carbonate with respect to the total pigment, and 87% by weight or more containing particles having a particle diameter of 2 μm or less.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the 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 in which at least two or more coating layers are provided on one side or both sides of a base paper, and the gel content of a latex binder contained in the lowermost layer and the uppermost coating layer And the particle size distribution and blending ratio of the pigment are specified.
[0009]
The basic design of the present invention is to clarify the division of roles between the lowermost layer and the uppermost layer, and to balance properties such as blister resistance, picking strength, blank paper gloss, and print gloss at a higher level than ever before. .
[0010]
The resistance to blistering necessary for coated paper for high-speed offset printing is largely due to the lowest layer existing in the vicinity of the base paper. In forced hot air drying during the printing process, moisture contained in the base paper is rapidly evaporated and expanded to generate 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 coated paper for printing can be reduced. When the air permeability of the coating layer is not sufficient, the strength in the z-axis direction of the base paper, that is, the internal bond strength is lost to the vapor pressure, the base paper is torn and so-called blisters are generated.
[0011]
An important factor that determines the air permeability of the coating layer is the gel content of the latex binder.
[0012]
The gel content mentioned here 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.
[0013]
If the gel content is lowered, the air permeability of the coating layer is improved and the blister resistance is improved, but the properties such as pick strength and printing gloss are lowered.
[0014]
The average particle size of the latex binder as well as the gel content is a factor that greatly affects the blister resistance and printing gloss.
[0015]
The average particle size of the latex binder referred to here is obtained by observing the Brownian motion of the latex binder in water by a dynamic laser light scattering method and analyzing the value by a photon correlation method such as a time interval method. (Unit: nm)
[0016]
When the average particle size of the latex binder contained in the coating layer is small, the picking strength of the coated paper for offset printing is improved and the blister resistance is lowered. On the other hand, when this is large, the reverse behavior is exhibited.
[0017]
Furthermore, the particle size distribution of the pigment also has a great influence on the blister resistance.
[0018]
The particle size distribution of the pigment referred to here is typified by a weight ratio in which a pigment having a particle diameter of 2 μm or less is included, and satisfies the above formulas 1 to 3.
[0019]
That is, in the multi-layer coated paper for offset printing of the present invention, the multi-layer coated paper for offset printing has a blister resistance due to increased air permeability by blending a certain amount or more of kaolin or calcium bicarbonate having an appropriate coarse particle size. It is possible to simultaneously improve quality such as white paper gloss and printing gloss by improving the surface property, improving the pick strength by increasing the undercoat layer strength, and increasing the smoothness of the uppermost layer by improving the undercoat layer covering. When the value of Formula 1 is less than 40, such characteristics may not be sufficiently exhibited.
[0020]
Furthermore, the composition ratio of the pigment constituting the uppermost layer of the multilayer coated paper for offset printing having the lowermost layer of the design as described above satisfies the above mathematical formulas 4 to 6, and the white paper gloss and the print gloss are further It will be very good. Fine kaolin or calcium bicarbonate expresses good printing quality due to its excellent smoothness, but with a single layer, it tends to lack rigidity and blister resistance, which is one of the important paper qualities. Yes, by combining relatively coarse pigments in the lowermost layer, these physical properties can be achieved at a high level. When the value of Formula 4 is less than 40, such characteristics may not be sufficiently exhibited.
[0021]
In the present invention, the method of coating each coating layer including the lowermost layer and the uppermost layer is not particularly limited, and various kinds of metadrum transfer such as size press, gate roll, shim sizer, air knife, rod Each method such as blade and direct fountain can be used as appropriate.
[0022]
In the present invention, the pigment used in the coating liquid is not particularly limited, for example, various natural mineral pigments such as various kaolins, talc and pulverized calcium carbonate, composite synthetic pigments such as satin white and lithon, oxidation Examples thereof include semi-synthetic pigments such as titanium, precipitated calcium carbonate, and alumina hydroxide, and synthetic pigments such as plastic pigments.
[0023]
Examples of the starch used in the coating solution include ordinary starch, oxidized starch, etherified starch, esterified starch, enzyme-modified starch, and cold water-soluble starch obtained by flash drying them.
[0024]
Further, as a thickener used in the coating solution, water-soluble polymers such as carboxymethylcellulose, sodium alginate, methylcellulose, hydroxyethylcellulose, casein, sodium polyacrylate, polyacrylate, styrene maleic anhydride copolymer And synthetic polymers such as silicates and inorganic polymers such as silicates.
[0025]
As binders other than starch used in the coating solution, various copolymer latexes such as styrene-butadiene, acrylic, and vinyl acetate, polyvinyl alcohol, sodium polyacrylate, polyethylene oxide, polyacrylamide, urea, melamine / Examples thereof include water-soluble synthetic compounds such as formalin resin, polyethyleneimine, polyamide polyamine / epichlorohydrin, natural products such as wax, casein, soybean protein, and those obtained by cationizing these.
[0026]
In addition, various auxiliary agents that are usually used such as a dispersant, an antifoaming agent, a water-proofing agent, and a coloring agent, and those obtained by cationizing these auxiliary agents are suitably used as necessary.
[0027]
The base paper used in the present invention includes chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, PGWRMP, TMP, CTMP, and CGP, and various pulps such as waste paper pulp, light calcium carbonate, heavy calcium carbonate, Various fillers such as talc, clay and kaolin, sizing agents, fixing agents, retention agents, paper strength enhancers and the like are suitably blended, and any of acidic, neutral and alkaline papers can be produced. In the base paper of the present invention, no-size press base paper, base paper size-pressed with starch, polyvinyl alcohol, or the like can be used. Further, various calendar processes may be performed to obtain the required density and smoothness of the base paper.
[0028]
The coated paper that has been coated and dried in a series of operations is subjected to various calendar treatments as necessary.
[0029]
The coating amount of the bottom layer, as a weight after drying is usually from 1 to 20 g / m ^2, preferably from 2 to 15 g / m ^2.
[0030]
Further, coating amount of the top layer, as the weight after drying, usually 4~20g / m ^2, preferably from 5 to 15 g / m ^2.
[0031]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In the examples, all parts and percentages are by weight unless otherwise specified.
[0032]
<Base paper formulation>
LBKP (freeness 440 mlcsf) 70 parts NBKP (freeness 490 mlcsf) 30 parts
<Internal medicine>
Light calcium carbonate (* expressed as ash content in base paper) * 8 parts commercial cationized starch 1.0 parts commercial cationic polyacrylamide yield improver 0.03 parts Pulp, internal chemicals adjusted with the above formulation, basis weight 70 g Paper of / m ² was made.
[0034]
< Lower layer coating liquid formulation>
Commercially available kaolin clay See Tables 1 and 2 Commercially available calcium carbonate See Tables 1 and 2 Commercially available polyacrylic acid dispersant 0.1 part Latex binder (gel content 20%, average particle size 150 nm 10 parts Commercially available phosphate ester starch 10 parts Hydroxide Sodium adjusted to pH 9.6
For this base paper, a coating solution is prepared with the above-mentioned composition, and a coating solution of 5 g / m ² on one side is applied at a coating speed of 1200 m / min using a rod-methade film press type coating machine. , Dried. In addition, Tables 1 and 2 show the number of blended commercial kaolin clay and commercial calcium carbonate in the undercoat coating solution.
[0036]
For the obtained one, 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 used on-line. A rendering process was applied.
[0037]
< Top layer coating composition>
Commercial grade primary kaolin clay See Tables 1 and 2 Commercial heavy calcium carbonate See Tables 1 and 2 Commercial polyacrylic acid dispersant 0.1 part Latex binder 15 parts Commercial phosphate ester starch 3 parts Commercial carboxymethylcellulose thickener (CMC) Prepared to 0.1 parts sodium hydroxide pH 9.6
Furthermore, a coating liquid having the above ratio is prepared, and the coating liquid is applied at 10 g / m ² on one side at a coating speed of 1600 m / min using a fountain application / blade type coating machine, and dried to form a multilayer coating. Obtained paper. In addition, Tables 1 and 2 show the blended parts of the commercial kaolin clay and the commercial calcium carbonate of the top layer coating solution.
[0039]
For the selected multi-layer coated paper, an off-line super calendar finishing device (number of stages: 10 stages, rigid roll: chilled roll with an outer diameter of 400 mm, elastic roll: cotton roll with an outer diameter of 400 mm, linear pressure: 220 kg / cm) Using this, a calendering process was performed to produce a multi-layer coated paper for offset printing.
[0040]
The multilayer coated papers for offset printing obtained in Examples 1 to 8 and Comparative Examples 1 to 6 were evaluated by the following evaluation methods, and the results are shown in Tables 1 and 2.
[0041]
<Evaluation method>
(1) Glossy printing After using the RI printing aptitude tester, indigo, red, yellow (ink amount 0.2cc each) heavy color solid printing, then gloss is reflected 60 ° -60 ° with a gloss meter. The rate was evaluated. The evaluation criteria are shown below. However, in the present invention, when satisfying the above formulas 1 to 3, the object of the invention is ◯ or more, and when satisfying the expressions 4 to 6 is also the object of ◎ or more.
◎ (very good): printing gloss is 70% or more ○ (good): printing gloss is 65% or more and less than 70% △ (normal): printing gloss is 55% or more and less than 65% x (defect): printing gloss Is less than 55% [0042]
(2) Blister resistance Coated paper wrapped with aluminum in an oil bath at 150 ° C. to 200 ° C. was dipped for a certain period of time, and was scored based on the number and size of the blisters generated (maximum 10 points). ○ The above is the subject of the invention.
◎ (very good): 10 points ○ (good): 7-9 points Δ (normal): 4-6 points × (defect): 5 points or less
(3) Using a dry pick strength RI printing aptitude tester, the paper peeling state was visually determined by printing with tack ink (tack value 20) and evaluated (up to 10 points). ○ It was considered good with the above.
◎ (very good): 10 points ○ (good): 7-9 points Δ (normal): 4-6 points × (defect): 5 points or less
[Table 1]

[0045]
[Table 2]

[0046]
In Example 1-4, by using the pigment of the appropriate particle size distribution and the amount of filled latex binder and the above equation 1-3 having an average particle size of the appropriate gel content in the lowermost layer, good blister resistance And expresses pick strength. Furthermore, embodiments in Examples 5-7, the pigment of the appropriate particle size distribution and the amount that satisfies the above equation 4-6 by using the top layer, excellent white paper gloss and offset printing multilayer coated paper showing the print gloss Could be manufactured.
[0047]
【The invention's effect】
In multilayer coated paper for offset printing, by simultaneously specifying the gel content and average particle size of the latex binder contained in the lowermost layer, in addition to the particle size distribution and blending amount contained in the lowermost and uppermost coated layers It is possible to exhibit both the blister resistance of the lowermost layer and the white paper gloss and printing gloss of the uppermost layer in a very high dimension that is not common.

Claims (1)

Latex which has a gel content of 65% or less and an average particle size of 130 to 250 nm in the lowermost coating layer in a multilayer coated paper for offset printing in which at least two coating layers are provided on one or both sides of the base paper The composition ratio of the pigment containing the binder and constituting the lowermost coating layer satisfies the following formulas 1 to 3, and the composition ratio of the pigment constituting the uppermost coating layer is the following formula 4 to features and to Luo offset printing multilayer coated paper that meets the 6.

A: The content ratio (% by weight) of kaolin with respect to all pigments, and 88% by weight or less having a particle diameter of 2 μm or less.
B: The content ratio (% by weight) of heavy calcium carbonate with respect to all pigments, and 83% by weight or less of particles having a particle diameter of 2 μm or less.
C: The content ratio (% by weight) of kaolin with respect to the total pigment, and 95 % by weight or more containing particles having a particle size of 2 μm or less.
D: The content ratio (% by weight) of heavy calcium carbonate with respect to the total pigment, and 87% by weight or more containing particles having a particle diameter of 2 μm or less.