JPH07100919B2 - Method for producing matte coated paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method for producing a matte coated paper, and in particular, a matte having a low white paper gloss but a high ink gloss after printing and good printability. The present invention relates to a method for manufacturing coated paper.

(B) Prior Art and Problems Conventionally, matte coated paper has a low gloss of white paper and gives an elegant feeling as compared with coated paper having high gloss, and is therefore used in a wide area. However, in order to reduce the white paper gloss, compared to the pigments used for ordinary coated paper, a coating solution containing a large amount of a coarser pigment is applied to the base paper, and since the white paper gloss is kept low, the calender The processing is also light and may not be performed at all. As a result, the coated paper is inferior in ink acceptability and ink gloss after printing.

In general, the surface of the coated paper is smoothed by the calendar treatment, the adhesion to the blanket is increased during offset printing, and the ink transfer property is improved. As a result, a printed matter having no printing unevenness and high printing gloss can be obtained. However, in the case of matte coated paper, the white paper gloss must be suppressed to a low level, so the calendering process must be lightened, and the smoothness decreases. Therefore, uneven printing is likely to occur and the printing gloss is likely to be low.

To solve this problem, when a pigment having a large particle size as described above, particularly calcium carbonate, is used, even if the calendering process is strengthened, the white paper gloss does not increase, but the ink easily sinks and high printing gloss is obtained. Absent. On the other hand, if you use a pigment such as kaolin, which has a high print gloss, you can obtain high print gloss without uneven printing by strengthening the calendar process, but the glossiness of the white paper becomes high, and the matte coated paper Cannot be obtained. It has been difficult to obtain a matte coated paper, especially a matte coated paper for offset printing, by using such conventional means.

Calcium carbonate, which has been widely used for matte coated paper, has less white paper gloss than kaolin.
It also has the property that printing gloss is less likely to appear.

On the other hand, it has long been known that talc can be used as a coating pigment, but since its shape is scale-like, the viscosity of the dispersion liquid is very high, and it is difficult to use high concentration and high compounding. The surface has strong hydrophobicity and air is attached to it, and it becomes bubbles during coating, leaving uncoated spots on the surface of the coated paper.

However, due to its flat shape, it has excellent smoothness, ink gloss after printing, and hiding power.

(C) Object of the Invention In view of the present situation, the present inventors compensate each other for the defects of calcium carbonate and talc to obtain a matte-coated paper having high ink gloss after printing even if white paper gloss is suppressed. For this purpose, we conducted a thorough study and sand-milled a mixed slurry of calcium carbonate and talc to a specific particle size to compensate for the mutual defects of calcium carbonate and talc, and also the glossiness of white paper was high and the ink gloss was high. The inventors have found that a matte coated paper can be obtained and have reached the present invention.

(D) Means for Solving the Problems That is, the present invention relates to a method for producing a matte coated paper in which a coated paper containing at least calcium carbonate and talc is coated on a base paper. Sand mill treatment as a mixed slurry of, the average particle size of the calcium carbonate is 0.
4 μ to 2 μ, talc is in the range of 0.5 μ to 2 μ, and a coating composition containing 20% by weight or more of the calcium carbonate and talc is applied to a base paper, dried, and then white paper gloss (JISP81
42 method) is a smoothing treatment so as to be 40% or less.

It is conventionally known to use calcium carbonate and talc as pigments for coated paper. For example, as disclosed in JP-A-59-106596, relatively coarse talc is blended, and its purpose is to lower the dynamic friction coefficient of coated paper.

In the present invention, the talc used is aimed at the effect of combining fine and narrow particle size range of calcium carbonate with a specific particle size range, which is essentially different from the conventional one.

The present inventor has previously applied for a method of pulverizing talc and calcium carbonate as a mixed slurry (Japanese Patent Publication No. 1-50450).
Issue). The mixed pulverized product obtained by this talc / calcium charcoal mixed pulverization method is applied to matte coated paper.

In the present invention, as mentioned above, a mixture of calcium carbonate having an average particle diameter of 0.4 μ to 2 μ and talc having an average particle diameter of 0.5 μ to 2 μ is used, but the average particle diameter of calcium carbonate is 2 μ. If it exceeds, it is difficult to obtain sufficient ink gloss, hiding power, and smoothness after printing.If it is less than 0.4μ, the coating layer strength decreases significantly, and the white paper gloss increases.
It is not preferable because the glossiness of the heavy color ink is reduced. When the average particle size of talc exceeds 2 μ, the smoothness is poor and the ink gloss is also low. If it is less than 0.5 μ, the coating layer strength is lowered and the gloss of the heavy color ink is lowered.

If the mixing ratio of calcium carbonate and talc having such a specific average particle diameter to the total pigment is less than 20% by weight, the mixing effect of talc and calcium carbonate is insufficient and the white gloss of coated paper becomes high. Moreover, since the gloss of the ink after printing is not improved, it becomes insufficient as a matte coated paper. Therefore, the ratio of calcium carbonate and talc to the total pigment is 20% by weight or more, preferably 30% by weight.
The composition will occupy the above.

Also, from the viewpoint of the effect of mixing talc and calcium carbonate, the content of talc needs to be 5% by weight with respect to calcium carbonate, and the upper limit is 90% when the liquidity of the final coating liquid is taken into consideration. Practically, the amount is not more than 70% by weight, preferably not more than 70% by weight.

Further, as a method for obtaining calcium carbonate and talc having such a specific average particle diameter, a high-concentration mixed slurry can be obtained by mixing talc and calcium carbonate and performing a sand mill treatment. Moreover, it becomes possible to completely remove the air trapped in the talc, which prevents the generation of uncoated spots on the coating machine.

The sand mill treatment of the present invention means stirring with a stirring blade such as a disc, a bar and a screw in a container filled with natural and synthetic mineral fine sand, hard glass fine particles, metal fine particles having an average particle diameter of about 1 to 3 mmφ. To crush the object to be treated, and those devices are, for example, those processed by a device (product) such as a sand glider, a super mill, or a dyno mill. A desired particle size can be obtained by appropriately combining the filling rate, the slurry flow rate, the slurry concentration, the rotation speed, the processing time, the mixing ratio of the raw material calcium carbonate and talc, and the particle size of the raw material calcium carbonate and talc.

In particular, the ratio of the particle size of the raw material calcium carbonate and the raw material talc has a great influence, and the average particle size of the raw material calcium carbonate is 55 to
By using talc as a raw material having an average particle diameter of 10%, it becomes easy to obtain a mixed slurry of calcium carbonate and talc having such a specific average particle diameter. This is because in wet mixing and pulverization, talc is exfoliated and the particle size is difficult to decrease, whereas calcium carbonate is an amorphous particle and the particle size is easily decreased.

Pigments for coated paper other than calcium carbonate and talc used in the present invention include kaolin, clay, satin white,
Examples thereof include titanium oxide, aluminum hydroxide, zinc oxide, barium sulfate, calcium sulfate, silica, activated clay, silicon earth, lake, and plastic pigment.

Examples of the adhesive used in the present invention include various copolymers such as styrene / butadiene, styrene / acrylic, vinyl acetate / acrylic, ethylene / vinyl acetate, butadiene / methylmethacrylic, vinyl acetate / butyl acrylate, and the like. Synthetic adhesives such as polyvinyl alcohol, maleic anhydride / styrene copolymer, isobutene / maleic anhydride copolymer, acrylic acid / methylmethacrylate copolymer, oxidized starch, etherified starch, esterified starch, enzyme modified Commonly known adhesives such as starch and cold water-soluble starch obtained by flash-drying them, natural adhesives such as casein, soybean protein and the like can be mentioned. Further, if necessary, various auxiliaries compounded with usual pigments for coated paper such as a dispersant, a thickener, a water retention agent, a defoaming agent, a water resistance agent, and a coloring agent can be appropriately used.

The method of applying the coating composition according to the present invention to a base paper is not particularly limited, and various ordinary coating devices such as an air knife coater, a roll coater, various blade coaters and a short dwell coater can be used.

Thus, the coated paper which has been coated with the coating composition and dried can be finished through a finishing device such as a super calender and a gloss calender, but the white paper gloss (JISP8142 method) is 40%.
It is finished under mild processing conditions as follows.

The matte coated paper of the present invention thus obtained can provide a printed matter having good smoothness, low white paper gloss, an elegant appearance, and excellent ink gloss.

(E) Action The fine calcium carbonate used in the present invention alone tends to produce white paper gloss and lowers the heavy ink gloss, as compared with calcium carbonate conventionally used for matte coated paper. It has the advantage that it is easy to obtain smoothness.
Further, the fine talc used in the present invention alone has a low white paper gloss, is likely to have smoothness, and has a good ink gloss, but the viscosity of the dispersion liquid is very high, and it is very high concentration and a high blending ratio. It has the drawback of being difficult. For the above reasons, fine calcium carbonate and talc as in the present invention have not been used in matte coated paper.

However, by using a mixed slurry of fine calcium carbonate and talc, which are the subject matter of the present invention, and by sand-milling each to a specific particle size, the use of the calcium carbonate produces a white paper gloss, which is a drawback for matte coated paper. The ease and difficulty in producing a heavy-colored ink gloss are canceled by the fine talc, and the difficulty of making the concentration of the coating liquid high and blending which is the drawback of the fine talc is due to the shape of calcium carbonate and the sand mill treatment. This is solved by wet mixing and pulverization, and a good matte coated paper can be obtained.

(F) Examples The effects of the present invention will be described below with reference to Examples, but the present invention is not limited thereto.

In addition, "part" and "%" in an Example show "weight part" and "weight%", respectively.

Examples 1 to 3, Comparative Examples 1 to 5 25 parts of talc having an average particle size of 10 μ, 75 parts of heavy calcium carbonate having an average particle size of 15 μ, 0.6 part of sodium polyacrylate, and a slurry having a solid content concentration of 70% were prepared, Using a sand mill with a vessel capacity of 120 l, bead particle size: 1 to 1.25 mmφ, bead filling rate: 7
It was passed under the conditions of 9%, slurry flow rate: 6 l / min, rotation speed 1400 rpm, and some control was performed by load current (rotation speed) to obtain a mixed pulverized slurry having the following average particle diameter.

Mixed slurry name A Average particle size of calcium carbonate after grinding 0.8μ Average particle size of talc after grinding 0.9μ Also 40 parts of talc with average particle size of 10μ, 60 parts of heavy calcium carbonate with average particle size of 15μ, 0.6 parts of sodium polyacrylate Adjust the slurry with a solid content of 68% and use a sand mill with a vessel capacity of 120 l to pass beads under the conditions of bead particle size: 1 to 1.25 mmφ, bead filling rate: 79%, slurry flow rate: 6 l / min, and rotation speed 1400 rpm. Some control was performed by the load current (rotation speed) to obtain a mixed pulverized slurry having the following average particle diameter.

Mixed slurry name B Average particle size of calcium carbonate after crushing 0.9μ Average particle size of talc after crushing 1.6μ The average particle size of other pigments used is as follows.

Heavy calcium carbonate Average particle size C 0.8μ D 2.8μ Talc E 2.5μ As the other pigment, kaolin of 2nd grade (HT clay manufactured by EMC) was used. The above pigments were blended in the proportions shown in Table 1, and were dispersed in water so as to have a solid content concentration of 70% by using 0.2 parts of sodium polyacrylate as a dispersant, and further styrene butadiene latex and phosphate ester. Table 1 shows modified starch
The mixture was stirred and mixed at a ratio as shown in to obtain a 61% coating liquid.

Both sides of this coating liquid composition were coated on a base paper for 60 g / m ² coated paper so that the coating amount was 13 g / m ² on one side in terms of solid content, and after dry conditioning, super calendering treatment was performed. The quality of each coated paper was compared and the results are shown in Table 1. The measurement conditions are as follows.

(1) Smoothness: Smoother smoothness tester (Toei Denshi KK
Made by). (MmHg) (2) White paper glossiness: Measured at an angle of 75 ° according to JIS P8142. (%) (3) Print glossiness: printed by a Roland offset printing machine, and magenta single color and magenta, cyan, yellow,
The print gloss of the three-color overlapping portion was measured at an angle of 60 degrees. (%) (4) Coating layer strength: The surface strength of the coated paper was determined using an RI printability tester (Ming Seisakusho). A value of 5 is a good condition, and a value of 3 or less causes a problem.

As shown in Table 1, in the examples of the present invention, even if the surface treatment is performed under the condition that the glossiness of the blank sheet is 40% or less, the smoothness of the blank sheet is good, the ink gloss after printing is high, and the elegant printing is good. I got a print.

(G) Effect of the Invention The present invention provides a white paper with less glossiness and smoothness by applying a coating solution containing 20% or more of talc having a specific average particle diameter and calcium carbonate as a pigment component of coated paper. It provides a matte-coated paper which has a good ink gloss.

Claims (1)

[Claims] 1. A pigment component for coated paper, containing 20% by weight or more of a mixed slurry of calcium carbonate and talc that satisfies the following conditions by a sand mill treatment, and the mixing ratio of calcium carbonate and talc is calcium carbonate. On the other hand, a base paper is coated with a coating composition having a talc content of 5 to 90% by weight,
A method for producing a matte-coated paper, which comprises drying and smoothing so that the white paper gloss (JISP8142 method) is 40% or less. Calcium carbonate 0.4μ ≤ average particle size ≤ 2μ Talc 0.5μ ≤ average particle size ≤ 2μ