JP3538837B2 - Coated paper for offset printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper for offset printing obtained by mixing light calcium carbonate having a specific shape which has been subjected to wet pulverization.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for coated paper for printing to reduce the weight of coated paper and visualize printed matter.
In printing, coated paper is required to be able to withstand higher speeds. In order to speed up printing, excellent printing surface strength is required for both rotary offset printing and sheet-fed offset printing, but further excellent blister resistance is required for rotary offset printing.

The difference between sheet-fed printing and rotary printing is that the latter requires instantaneous drying of the printed ink, and paper with poor blister resistance during high temperature and high speed drying is unsuitable as printing paper. It is. The blister phenomenon occurs when the moisture contained in the coated paper instantaneously turns into water vapor due to high temperature, thereby generating internal pressure. As measures against this, it is conceivable to increase the internal bond strength of the base paper, to improve the porosity of the coating layer, and the like. However, each of these measures has its own problems. In particular, the use of a coating liquid often causes deterioration in the fluidity of the coating liquid and impairs operability.

[0004] From the standpoint of productivity of coated paper, how to increase the production efficiency has become the most important issue as compared to before. Under these circumstances, the weight of coated paper has been reduced, but the quality to be especially noted is opacity. There are several known techniques for obtaining high opacity. For example, mechanical pulp has been selected as a pulp to be used, but a decrease in whiteness and smoothness of the obtained coated paper is inevitable. In addition, although measures have been taken from the viewpoint of compounding, such as incorporation of a pigment having a high refractive index, such as titanium dioxide, into the base paper as a filler, the use of the base paper is extremely expensive and its use is restricted.

[0005] From the viewpoint of visualization of printed matter, it is important to have high blank glossiness in addition to opacity. In order to achieve high blank glossiness, a means for strengthening the calendar can be considered. However, while strong calendering is suitable for obtaining a good blank gloss, it poses another problem. That is, the opacity is reduced, and this tendency is more prominent in low basis weight paper. As described above, if such measures are taken when actually producing a coated paper, the accompanying drawbacks appear at the same time, and it is difficult to make the target coated paper a reality.

[0006] In view of the above situation, it is necessary to obtain a coated paper for offset printing which has good blister resistance, excellent opacity, excellent white paper gloss, and good operability, especially for lightweight offset coated paper. It was not possible at the moment.

[0007]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a coated paper for offset printing which is excellent in blank gloss, opacity, printing surface strength and blister resistance. It is.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that, in a coated paper for offset printing having a coating layer mainly composed of a pigment and an adhesive on a base paper, By containing 50% by weight or more of the light calcium carbonate having an average particle diameter of 0.25 to 0.90 μm in all the pigments in the coating layer after wet pulverization of the lightly-calculated light calcium carbonate, the glossiness of the white paper is improved. A coated paper for offset printing excellent in opacity, printing surface strength and blister resistance was obtained, and the present invention was completed.

The details of the present invention will be described below.

The present inventors have conducted intensive studies to obtain coated paper for offset printing which is excellent in glossiness, opacity, printing surface strength and blister resistance for white paper. By applying a coating liquid containing a specific amount of light calcium carbonate having a specific shape obtained by pulverization, a roto-offset having high white paper glossiness, high opacity, excellent printing surface strength and excellent blister resistance It was found that printing paper for printing was obtained.
Light calcium carbonate having a specific shape is, when wet scouring the scaly light calcium carbonate, a needle-like or columnar light calcium carbonate formed by breaking the tip of a needle radially protruding from the scaly light calcium carbonate. This is a mixture of aggregates of needle-like or columnar light calcium carbonate having a relatively spherical shape remaining after the tip is broken.

The average particle size of the light calcium carbonate after wet grinding used in the present invention is 0.25 to 0.9.
It needs to be 0 μm. Average particle size 0.25
If it is less than μm, the blister resistance and the printing surface strength are poor. When the average particle size exceeds 0.90 μm, the glossiness and opacity of white paper are inferior. In addition, because the aggregated particles remain due to insufficient pulverization, if there is such a large particle diameter near the surface of the coating layer, it appears as a large pigment pick at the time of printing, printing The surface strength may decrease. The amount of light calcium carbonate after the wet pulverization needs to be 50% by weight or more, and preferably 50 to 90% by weight. When the content of light calcium carbonate is less than 50% by weight, the opacity, the glossiness of white paper, and the suitability for blister resistance decrease. If the light calcium carbonate content exceeds 90% by weight, the printing surface strength tends to decrease.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The scaly light calcium carbonate used in the present invention can be produced by a carbon dioxide gas method (produced by blowing carbon dioxide gas into slaked lime slurry) or a causticizing method (a pulp production process by a sulfate method or a soda method). Manufactured in the causticizing process)
It is used by crushing what is manufactured in, but its shape is
The minor axis is 0.2 to 0.4 μm, and the major axis is 1.5 to 4.0 μm
Of primary particles having an average particle size of 2.5
It is preferably about 12.0 μm.

In the case of using a caustic light calcium carbonate in the form of a scallops, it can be obtained at low cost according to the following production method. (1) Using quicklime introduced from outside the causticizing process, (2) The molar ratio of quicklime and water at the time of slaked lime generation is quicklime: water = 1: 1 to 1: 5, and as a basis for the weight of slaked lime. To the slaked lime containing 0.05 to 8% by weight of calcium carbonate, white liquor is added so that the slaked lime concentration becomes 10 to 60% by weight, and the mixture is slaked with stirring or mixing, and lime milk and / or A predetermined amount of green liquor generated in the causticizing step and required for producing white liquor is added to the lime milk and / or lime mud in the first step for producing lime mud and then the lime milk and / or lime mud. It is manufactured by successively adding lime mud at a specific addition rate in a specific range and performing a causticization reaction at a reaction temperature of 25 to 75 ° C.

The scaly light calcium carbonate of the present invention is used after being appropriately wet-pulverized by a pulverizer such as a bead mill. The pulverizer used in the present invention is very suitable for wet pulverization of papermaking pigments. Commonly used attritors, vibrating mills, ball mills, vertical sand mills, horizontal sand mills, jet mills and the like can be used. Further, as the grinding media, spherical balls made of hard raw materials such as glass, ceramic, alumina, and zirconia,
The particle diameter is preferably from 0.1 to 10 mm. In consideration of the crushing efficiency, it is preferable that the filling rate of the medium is as high as possible.However, if the filling rate is too high, the movement of the medium in the crushing chamber is restricted, and conversely, the crushing efficiency may be reduced, so that it is used. Adjust appropriately according to the crusher.

The pigments used in the present invention include, in addition to the light calcium carbonate defined above, commonly used heavy calcium carbonate, light calcium carbonate, kaolin, clay, delaminated clay, talc, satin One or more of white, silica, plastic pigment, titanium dioxide and the like may be used in combination.

The adhesive used in the present invention is a styrene / butadiene copolymer, a styrene / butadiene / acrylic copolymer or a modified product thereof. The monomers of these polymers include styrene, butadiene and the like. ,
Other vinyl compounds such as methyl methacrylate and other vinyl unsaturated carboxylic acid ester compounds and acrylonitrile,
Alternatively, it is desirable to use vinyl unsaturated carboxylic acids such as acrylic acid and maleic acid. Also, oxidized starch,
Starches such as phosphorylated esterified starch, etherified starch, enzyme-modified starch and cold water-soluble starch can be used in combination. The amount of the adhesive used is preferably 5 to 30 parts by weight based on 100 parts by weight of the pigment. Further, by adding the anionic polyacrylamide-based paper strength enhancer together with the adhesive in an amount of 1.0 to 3.0% based on all the pigments in the coating layer, the printing surface strength and the blister resistance can be further improved. it can.

In the present invention, a dispersant, a thickener, a water retention agent, an antifoaming agent,
The coating liquid can be prepared by using various auxiliaries blended with ordinary pigments for coated paper such as a water-proofing agent, and the concentration of the coating liquid is preferably 40 to 68% by weight. The coating solution thus prepared is applied to base paper, but the coating method is not particularly limited, and various blade coaters, roll coaters,
Various coating apparatuses such as an air knife coater, a bar coater, a rod blade coater, and a short dwell coater are coated on a base paper in a single layer or a multilayer by an on-machine or an off-machine. In the present invention, when two layers are coated, either the overcoat layer and the undercoat layer, or one of the overcoat layer and the undercoat layer has the coating layer of the present invention. In particular, when the coating layer of the present invention is used as an undercoat layer, the effects of the present invention become more remarkable. The coating amount is adjusted in the range of 5 to 50 g / m ^{2 on} both sides.

The base paper used in the present invention includes:
A mixture of mechanical pulp, chemical pulp, waste paper recovery pulp, etc. is used in any ratio, and if necessary, a normal papermaking filler, a paper strength enhancer, a retention aid, a sizing agent, etc. are added to a single papermaking raw material. It is made by a normal paper machine having wires or twin wires,
It is preferred basis weight is 30 to 100 g / ^{m 2.}

The coated paper obtained by coating the coating composition of the present invention can be coated with a printing paper using a surface finishing device such as a super calender, a gloss calender, or a soft calender. It is also possible to perform a finishing treatment or obtain a matte printing coated paper with low gloss without any treatment.
Further, the coated printing paper of the present invention can perform offset printing either on a sheet-by-sheet basis or on a roll. In the present invention, the basis weight is 100 g / m ² or less, preferably 80 g / m ^2.
The following coated paper for offset printing has particularly excellent effects.

[0020]

The present invention will be described in more detail with reference to the following examples, but it should be understood that the present invention is by no means restricted to such specific ranges. In the examples, parts and% indicate parts by weight and% by weight, respectively, unless otherwise specified. <Quality evaluation method> (1) 50% of the cumulative weight distribution was measured using a centrifugal sedimentation type particle size distribution analyzer (Micron Photosizer, manufactured by Seishin Enterprise).
The points were measured as the average particle size. (2) Blank glossiness Measured at an angle of 75 degrees according to JIS P-8142. (3) Opacity Opacity was measured using a digital hunter whiteness meter (manufactured by Toyo Seiki Seisaku-sho, Ltd.) according to JIS P-8138, Method A. (4) Using a dry strength RI-I type printer (manufactured by Mei Seisakusho), using Toyo Ink TV-24, printing at a constant ink amount of 0.35 ml, and visually evaluating the degree of picking on the printed surface by relative evaluation. did. ＝= Not generated at all, ○ = Almost not generated, Δ = Produced, × = Remarkably generated (5) Blister resistance Using a RI-I type printing machine (Meiji Seisakusho), manufactured by Toyo Ink (TK Mark V617) Use, ink amount 0.8cc
After constant printing on both sides and humidity control for one day and night, the test piece was immersed in a constant temperature oil bath set at a temperature of 140 ° C., and the occurrence of blisters was visually determined. ＝= Not generated at all, ＝= Not generated at all, Δ = Produced, X = Remarkable generation [Example 1] Average consisting of primary particles having a minor axis of 0.3 μm and a major axis of 1.6 μm produced by the causticizing method. Particle size 3.4 μm
A 70% -concentrated coarse slurry obtained by adding 0.3 part of sodium polyacrylate-based dispersant to 100 parts of scaly light calcium carbonate was mixed with glass beads having a bead diameter of 1.5 to 2.0 mm ( 20 kg of Toshiba Barotini)
Grinding was carried out using a filled 8-gallon sand mill (manufactured by Imex). The average particle size after pulverization was 0.50 μm.

To 85 parts of the thus-crushed light calcium carbonate thus obtained, 5 parts of heavy calcium carbonate, 10 parts of kaolin, and 10 parts of a styrene / butadiene copolymer latex with respect to all pigments as an adhesive were used. , 4.0 parts of a phosphate esterified starch, and 2.0 parts of an anionic polyacrylamide-based paper strength enhancer (Hamacoat P-Z300, manufactured by Misawa Ceramic Chemicals) based on all the pigments, and a solid content concentration of 65 parts was added. % Of coating liquid A was prepared. Next, 20 parts of heavy calcium carbonate, 20 parts of kaolin, and 11 parts of a styrene-butadiene copolymer latex as an adhesive were added to 60 parts of amorphous light calcium carbonate.
Parts, 3.5 parts phosphate esterified starch, and an anionic polyacrylamide paper strength agent (Hamacoat P
-Z300, manufactured by Misawa Ceramic Chemicals) was added to all the pigments in an amount of 1.5 parts to prepare a coating solution B having a solid content of 65%. The coating solution A thus prepared was weighed to 45 g.
/ M ² of base paper using a blade coater at a coating speed of 1000 m / min and a coating amount of 6.0 g per side.
/ M ^2, and then undercoat coating B was applied under the same conditions so that the coating amount was 7.0 g / m ² per one side. Further, using a two-stack soft calendar, the number of nips is twice, and the processing speed is 1000 m /
The surface treatment was performed under the conditions of a treatment temperature of 130 ° C. and a treatment linear pressure of 200 kgf / cm to obtain a coated paper for printing. [Example 2] In the coating liquid A, the average particle diameter of the pulverized light calcium carbonate was 0.35 µm instead of 0.5 µm.
A coated paper for printing was obtained in exactly the same manner as in Example 1, except that m was used. [Example 3] In coating liquid A, the average particle size of the light calcium carbonate after pulverization was 0.85 µm instead of 0.5 µm.
A coated paper for printing was obtained in exactly the same manner as in Example 1, except that m was used. [Example 4] In coating liquid A, 85 parts of light calcium carbonate after grinding, 5 parts of heavy calcium carbonate, and kaolin 1
Instead of 0 parts, 50 parts of light calcium carbonate after grinding,
Coated paper for printing was obtained in exactly the same manner as in Example 1, except that 40 parts of heavy calcium carbonate and 10 parts of kaolin were blended. [Example 5] The coating amount of only coating liquid A was 13.0 per one side.
A coated paper for printing was obtained in exactly the same manner as in Example 1 except that the coating was performed in a single layer to give g / m2. [Comparative Example 1] In coating liquid A, the average particle size of the light calcium carbonate after pulverization was 0.20 μm instead of 0.5 μm.
A coated paper for printing was obtained in exactly the same manner as in Example 1, except that m was used. [Comparative Example 2] In coating liquid A, the average particle size of light calcium carbonate after pulverization was 1.1 μm instead of 0.5 μm.
A coated paper for printing was obtained in exactly the same manner as in Example 1 except that the above conditions were satisfied. [Comparative Example 3] In coating liquid A, 85 parts of light calcium carbonate after pulverization, 5 parts of heavy calcium carbonate, and kaolin 1
Instead of 0 parts, 40 parts of light calcium carbonate after grinding,
Coated paper for printing was obtained in exactly the same manner as in Example 1 except that 50 parts of heavy calcium carbonate and 10 parts of kaolin were blended. [Comparative Example 4] Coating paper for printing was prepared in exactly the same manner as in Example 1 except that in the coating liquid A, the light calcium carbonate after pulverization was used in place of the pulverized light calcium carbonate without pulverization. Obtained. [Comparative Example 5] Comparative Example 4 was repeated except that in the coating liquid A, needle-like light calcium carbonate having a short diameter of 0.3 µm and a long diameter of 1.5 µm was used in place of the pulverized light calcium carbonate without pulverization. Coated paper for printing was obtained in exactly the same manner.

The above evaluation results are shown in Table 1.

[0023]

[Table 1] As is clear from the results in Table 1, Examples 1 to 5 have high white paper glossiness, high opacity, and excellent printing surface strength and blister resistance. On the other hand, Comparative Example 1 is inferior in printing surface strength and blister resistance. In Comparative Example 2, the glossiness and opacity of the white paper were low, and the printing surface strength was poor. In Comparative Example 3, the glossiness and opacity of the white paper were low, and the blister resistance was poor. Comparative Example 4 has a low blank gloss level. Comparative Example 5 is inferior in blister resistance. Accordingly, the coated paper for printing obtained by the present invention provides an unprecedented excellent coated paper quality, and its effect is extremely large.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katsunori Semi 2-81-1, Iida-cho, Iwakuni-shi, Yamaguchi Japan Nihon Paper Industries Co., Ltd. Iwakuni Technical Research Institute (72) Inventor Yasunori Minamisato 2 Iida-cho, Iwakuni-shi, Yamaguchi JP-A-59-232916 (JP, A) JP-A-2-104797 (JP, A) JP-A-63-211394 (JP, A) A) JP-A-1-221282 (JP, A) JP-A-6-227114 (JP, A) JP-A-2000-264629 (JP, A) JP-A-2000-136496 (JP, A) JP-A-10-245799 (JP, A) JP-A-11-314915 (JP, A) JP-A-11-20301 (JP, A) JP-B-57-30815 (JP, B1) JP-B 1-222400 (JP, B2) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) D21H 11/00-27/42 C01F 1/00- 17/00

Claims (3)

(57) [Claims] 1. A coated paper for offset printing having a coating layer containing a pigment and an adhesive as main components on a base paper, wherein an average particle diameter of the pigmentary light calcium carbonate after wet grinding is 0.25. Coated paper for offset printing, characterized by containing 50% by weight or more of light calcium carbonate of up to 0.90 µm in all pigments. 2. A pigment having an average particle size of 0.25 to 0.9 after wet-grinding of scaly light calcium carbonate as a pigment.
2. The coated paper for offset printing according to claim 1, wherein a coating layer containing 0% by weight or more of light calcium carbonate in all pigments in an amount of 50% by weight or more is provided on the undercoat layer, and then the overcoat layer is provided. 3. The scaly light calcium carbonate is an aggregate of primary particles having a minor axis of 0.2 to 0.4 μm and a major axis of 1.5 to 4.0 μm, and the aggregate has an average particle diameter of 2.5 to 2.5 μm. ~ 1
3. The device according to claim 1, wherein the thickness is 2.0 μm.
Coated paper for offset printing as described.