JP3126191B2 - Matting method of coated paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for matting coated paper which is excellent in coatability, smoothness and printability and does not require any special equipment.

[0002]

2. Description of the Related Art A so-called matte coated paper in which the glossiness of a coated paper is suppressed, that is, a matte coated paper is used for a calendar, an advertisement, a poster, and the like as a coated paper capable of giving a high-grade appearance due to its calm appearance. Such matte-coated paper is a mat-mat-like coated paper in which the printing gloss is suppressed by the gloss of the printing surface, and a mat-gloss-tone in which the printing gloss is enhanced to emphasize the difference from the blank gloss. Can be roughly classified into two types. In particular, the latter matte-gloss matte coated paper
It is often used because it gives a more luxurious feeling due to the difference between the glossiness of blank paper and the glossiness of printing.

Conventionally, the following methods have been known as matting methods for coated paper. (1) A method of using an inorganic pigment having a coarser size than the usual one. (2) A method of finishing by passing through a roughening roll after coating (Japanese Patent Publication No. 59-53956). This matting method reduces the smoothness of the coated surface. However, such a method has poor printability compared to ordinary coated paper due to low smoothness. The point reproducibility is extremely poor and satisfactory matte coated papers cannot be obtained. In order to improve the smoothness, a method of increasing the nip pressure at the time of the calendering process may be considered. However, in such a method, improvement in printability cannot be expected because the bulk of the coating layer is extremely reduced. It is also difficult to do this in a realistic manner. further,
In the method (1), the viscosity under high shearing force is remarkably increased due to the use of the coarse inorganic pigment, which is a serious problem in the coating workability.

Japanese Patent Application Laid-Open No. 2-234993 discloses a method for improving the above-mentioned problem by passing a predetermined smoothness by calendering treatment and then passing the paper through a roughening roll having a specified surface roughness. It has been disclosed. However, even with this method, sufficient smoothness cannot be obtained, and there are problems such as very strict adjustments required when industrially implemented, and the above problem has not been solved. . JP 1-11
No. 8695 and Japanese Patent Application Laid-Open No. 3-40897 disclose a method of using a specific pigment for matte coated paper for gravure printing, but it still does not solve the above problem. . Here, as a method for improving the above-mentioned smoothness, conventionally, it is widely known that polystyrene emulsion particles having a particle diameter of about 200 to 600 nm are added to a paint as so-called plastic pigments. However, the main feature of the plastic pigment is to improve the gloss of the coated paper, that is, to give a gloss, which is contrary to the purpose of obtaining the above matte coated paper.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for matting coated paper which has good coatability, excellent smoothness, and excellent printability.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, emulsion particles smaller than a specific particle size and smaller than the above-mentioned conventional plastic pigments should be added to the paint. Has found a completely new fact that it has a matting effect contrary to a polishing effect. By utilizing the above action, the present inventors,
The present invention has been completed in that a matte coated paper having both high smoothness and good printability is obtained very easily without using any special equipment. That is, the present invention is characterized by adding 0.5 to 200 parts by weight of emulsion particles having a particle diameter of 100 nm or less to 100 parts by weight of the inorganic pigment contained in the coating composition for coated paper. This is a method for matting coated paper. Here, the emulsion particles to be added need only satisfy the above-mentioned conditions of the particle size, and the preparation method is not particularly limited. For example, it can be easily prepared in the usual emulsion polymerization of a vinyl monomer,
JP-A-1-182313, JP-A-2-77402, JP-A
It can also be prepared using a method disclosed in, for example, JP-A No. 3-20365.

In the above preparation, a surfactant to be used,
The initiator, the vinyl monomer, and the like are not particularly limited. Here, the particle size of the prepared emulsion particles is 100 nm or less, preferably 80 nm or less.
is there. When the particle size of the emulsion particles exceeds 100 nm , the effect of improving the gloss is obtained as a plastic pigment, which is contrary to the object of the present invention. In the present invention, the paper coating composition to which emulsion particles having a particle size of 100 nm or less are added is not particularly limited as long as it is a commonly used composition comprising an inorganic pigment, a binder and the like. Generally, as an inorganic pigment, kaolin clay, calcium carbonate, talc, satin white, titanium dioxide, etc., and as a binder, styrene butadiene latex, acrylic emulsion, acrylic-styrene emulsion, vinyl acetate emulsion And a water-dispersible binder such as starch, modified starch, casein, polyvinyl alcohol, etc., alone or in combination. In addition, an antifoaming agent, a release agent, a dispersant, a viscosity modifier, a bluing agent, and the like may be added to the coating composition as needed.

[0008] Here, the particle size of the coating composition for paper coating is 1
The emulsion particles having a size of 00 nm or less are added, and the amount of the emulsion particles is 0.5 to 200 parts by weight, preferably 1 to 100 parts by weight, based on 100 parts by weight of the inorganic pigment contained in the coating composition for paper coating. 100 parts by weight, more preferably 2 parts
５０50 parts by weight. The amount of emulsion particles added is
If less than 0.5 parts by weight, the matting effect is not recognized,
On the other hand, if it exceeds 200 parts by weight, blocking on the calender roll is likely to occur, and the opacity of the coated paper is reduced. 8 to 50 g of the coating composition thus prepared is applied on one or both sides of the base paper by dry weight.
/ M ² . As a coating method, a normal blade coater, roll coater, air knife coater,
A bar coater or the like is used, and there is no particular limitation. The coated paper that has been coated and dried in this way is subjected to a calendering process at the end, but a super calender, a gloss calender, a mat calender, etc. are used according to the purpose. Is done. Matte coated paper of the present invention obtained by a very simple method as described above,
Not only low white paper gloss but also high surface smoothness and excellent printability.

[0009]

EXAMPLES The present invention will be described in detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. In the following, all parts and percentages are by weight.

[I] Preparation of Emulsion Particles Emulsion particles were prepared as follows based on a usual emulsion polymerization method. Polymerization Example 1 A separable flask equipped with a stirrer, thermometer and reflux condenser was charged with 700 parts of water and 4 parts of sodium lauryl sulfate, and heated to 80 ° C. while stirring and replacing with nitrogen. The internal temperature was maintained at 80 ° C., and 3.2 parts of potassium persulfate was added as a polymerization initiator to completely dissolve the mixture.
Parts, Latemul S-180 (Kao) 8 parts, styrene 69
6 parts, 80 parts of acrylonitrile and 24 parts of methacrylic acid were added under stirring, and 5% of the total amount of the emulsion prepared was charged in a separable flask, and polymerization was performed for 30 minutes.
The remaining emulsion was added and polymerized over about 2 hours, and the whole amount was added, followed by aging for another 2 hours. After completion, the pH was adjusted to 8 with an aqueous sodium hydroxide solution, and the solid content was adjusted to 40.
%, Emulsion particles having a particle diameter of 63 nm were obtained.

Polymerization Examples 2 and 3 Polymerization Example 2 (particle diameter 71 nm) was prepared in the same manner as in Polymerization Example 1 except that the composition of the vinyl monomer was 776 parts of styrene and 24 parts of methacrylic acid. Styrene 8
Emulsion particles were prepared as Polymerization Example 3 (particle size: 57 nm) in which 0 part, 584 parts of methyl methacrylate, 120 parts of acrylonitrile, and 16 parts of methacrylic acid were prepared.

Polymerization Example 4 700 parts of water was charged into the same separable flask as in Example 1, and the temperature was raised to 80 ° C. while purging with nitrogen while stirring.
The internal temperature was maintained at 80 ° C., and 3.2 parts of potassium persulfate was added as a polymerization initiator to completely dissolve the mixture.
Parts, Latemul S-180 (Kao) 8 parts, styrene 69
6 parts, 80 parts of acrylonitrile and 24 parts of methacrylic acid were added with stirring to make up 0.5% of the total amount of the emulsion prepared.
Was charged in a separable flask, polymerization was carried out for 30 minutes, the remaining emulsion was added over about 3 hours, polymerization was carried out, and after the entire amount was added, aging was carried out for another 2 hours. After completion, the pH was adjusted to 8 with an aqueous sodium hydroxide solution to obtain emulsion particles having a solid content of 40% and a particle diameter of 230 nm.

[II] Preparation of coated paper Examples of the present invention in which the emulsion particles obtained as described above are added to a general paper coating composition are shown below. Example 1 As shown in Table 2, as a dispersant, sodium polycarboxylate (Aron T-40; manufactured by Toa Gosei Chemical Industry) 0.0
Kaolin prepared using 9 parts (UW-90; EMC)
40 parts, light calcium carbonate (TP-222HS;
Phosphated starch (MS-4600; manufactured by Nippon Shokuhin Kogyo) 4
Parts, SBR latex (Polylac 780; manufactured by Mitsui Toatsu Chemicals), 12 parts (solid content), and 10 parts (solid content) of the emulsion particles prepared in the above polymerization example to a paper coating composition prepared. This was added to prepare a coating solution having a solid content of 60%. The above coating liquid is applied on a high-quality paper with an applicator so as to have a dry weight of 25 g / m ^2.
After drying in seconds, calender roll roll temperature 60
The coated paper was passed twice under the conditions of ° C, a linear pressure of 70 kg / cm, and a speed of 10 m / sec to obtain a coated paper. The evaluation method of the coated paper is shown below. High shear color viscosity: Measured at 8,800 rpm with a Hercules high shear viscometer. Blank gloss: The reflectance at 75 ° was measured according to JIS P-8142. Printing gloss: Printed with a RI printing tester using 0.4 cc of New Bright Indigo made by Toyo Ink, dried, and measured for 60 ° reflectance according to JIS P-8142. Smoothness: Measured using Oken type smoothness meter. Halftone dot reproducibility: Printed using a gravure printing tester (manufactured by Kumagai Riki Kogyo Co., Ltd.): A dot missing portion in a 20% gradation portion was measured and displayed as a missing dot ratio (%).

Examples 2 to 5 In Example 1, the type of emulsion particles to be added,
Table 1 shows the results when the amount and the pigment content were changed. Comparative Example 1 In Example 1, the emulsion particles to be added were polymerized.
Comparative Example 1 The results when varying the as prepared in 4,
The results are shown in Table 1. Comparative Example 2 In Example 1, the addition amount of the emulsion particles was 300
Table 1 shows the result when the number of parts was changed to Comparative Example 2 as Comparative Example 2. Comparative Example 3 Table 1 shows the results of Example 5 when no emulsion particles were added. Comparative Example 4 Table 1 shows the results obtained in Example 1 except that 20 parts of heavy calcium carbonate (Super # 2000; manufactured by Maruo Calcium) was added without adding the emulsion particles. Table-
As shown in the results described in 1, the method of adding the emulsion particles having a particle diameter of 100 nm or less to the coating composition for paper coating of the present invention lowers the high shear viscosity and improves coating workability. Further, coated paper obtained from the paint,
The white paper gloss is greatly reduced, and a remarkable matting effect is observed. Furthermore, improvement in smoothness and printability (improvement in printing gloss, reduction in the missing dot rate during gravure printing) has been recognized, and it has been difficult to obtain good matte-coated paper using conventional techniques. It can be obtained easily.

[0015]

[Table 1]

[0016]

The coating composition for coated paper of the present invention has a particle diameter of
By the method of adding emulsion particles of 100 nm or less, coating suitability and smoothness are very good, printability,
Further, matte coated paper having a low missing dot ratio during gravure printing can be easily obtained.

Continuation of the front page (72) Inventor Tsuyoshi Yanagihara 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Examiner in Mitsui Toatsu Chemicals Co., Ltd. Field surveyed (Int. Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (1)

(57) [Claims] 1. A coating method comprising adding 0.5 to 200 parts by weight of emulsion particles having a particle diameter of 100 nm or less to 100 parts by weight of an inorganic pigment contained in a coating composition for coated paper. How to matte paper.