JP2943571B2 - Production method of double-side 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 producing double coated paper by double coating in which an undercoat layer and an overcoat layer are provided on a base paper. More specifically, the present invention provides:
The present invention relates to a method for producing a dull-tone or semi-dull double-sided coated paper having relatively high smoothness, low density, bulkiness, and excellent printability and printing workability without performing surface finishing such as calendering.

[0002]

2. Description of the Related Art With the improvement of cultural standards, there is a strong demand for higher-grade paper products such as catalogs, publications and printed materials, and so-called coated paper obtained by coating a base paper with a pigment has a high degree of whiteness, glossiness and smoothness. Because it is high and the print finish is excellent,
The use of coated paper in various fields is increasing.

[0003] With the expansion of applications, in addition to the glossy coated paper having a high glossiness, which has been the mainstream in the past, a matt coated paper which has a low gloss but gives a moist visual and tactile feel,
Further, dull-tone and semi-dull coated papers, so-called matte coated papers, which are located between the matte tone and the glossy tone, are increasingly used for their elegance and luxury. That is, such matte coated paper, when printing, the text portion is relatively low gloss to make it easy to read, and the image portion becomes a printed matter rich in contrast by making it stand out by gloss,

[0004] However, all of these matte coated papers are generally inferior in smoothness and glossy coating in terms of print finish because they are all designed to maintain low gloss. At present, it is considerably inferior to paper.

As a means for solving these problems, calendering is generally performed using a light machine calendar and / or a soft calender, a super calender, or the like, but this will inevitably increase the density of the coated paper.
As a result, another new problem arises in that properties such as opacity and rigidity (waist or bulkiness) are impaired.

There is also disclosed a method in which a coated paper is pressed between a roughening roll and an elastic roll to pass the paper, and the surface of the coated paper is matted to improve the printing effect (Japanese Patent Laid-Open No. 55-55). 1359
Japanese Unexamined Patent Publication No. Hei. 1-174669, etc.) requires a new installation of equipment provided with a roughening roll.

Further, a method using a matting coating composition comprising calcium carbonate and a kaolinite-based additive (Japanese Patent Laid-Open No. 2-104797), a method of using calcium carbonate to apply heated steam immediately before soft calendering. Methods for specifying the type, particle size, and content of the coating pigment have been proposed, such as a method for producing an erased coated paper (JP-A-4-370298). However, the coated paper obtained by these methods has a low smoothness (the former) and a smoothness of 2 because a large amount of calcium carbonate having a large average particle diameter is used.
In addition to the short time of less than 00 seconds, the method requires a humidifying device and a soft calendering device, which complicates the manufacturing process (the latter).

As described above, with the diversification of market needs, there is an elegance and luxury that are not available in the conventional glossy or matte tone, and the printability (print finish) and printability are excellent. Despite the demand for realizing a semi-dull, high-smoothness, low-density, and bulky coated paper, its production method has not yet been developed.

[0009]

In view of the present situation, the present inventors have made intensive studies to solve the problems of the prior art, and as a result, provided an undercoat layer on both sides of the base paper and further overcoated thereon. In the double coating method of providing a layer, using a base paper having a specific smoothness and providing a coating composition mainly composed of fine kaolin having a specific particle size as an overcoat layer, a major remodeling of the equipment can be achieved. No need to use expensive raw materials and / or chemicals, it was found that a dull or semi-dull coated paper excellent in printability and printability was obtained. Reached.

An object of the present invention is to provide a double-coated paper having a glossiness in the range of 30 to 55% in a dull or semi-dull tone, high smoothness, low density, high bulk, excellent printability and excellent printing workability. It is to provide a manufacturing method of.

[0011]

According to the present invention, a coating composition comprising a pigment and an adhesive as a main component is coated on both sides of a base paper mainly comprising a cellulose pulp as an undercoat layer and an overcoat layer, and dried. In a method for producing a double-side coated paper, a base paper having an Oken type smoothness of 15 to 80 seconds is used, and kaolin having an average particle size of 0.3 to 0.8 μm is used in an amount of 50% by weight based on the weight of all pigments. By applying the coating composition containing the above as an overcoat layer, the glossiness of the coated surface is 30 to 55%
And a method for producing a double-coated paper characterized by a smoothness of 200 to 600 seconds.

The coating composition for the overcoat layer used in the present invention has an average particle size of 0.3 to 0.8 μm, preferably 0.1 to 0.8 μm.
Fine kaolin in the range of 4 to 0.6 μm is contained in 50% of all pigments.
% Or more, preferably 60 to 100%. Kaolin has a plate-like structure and is obtained from kaolin mineral, and is excellent in the effect of expressing the smoothness of the coating film. However, when the average particle size exceeds 0.8 μm, the glossiness of the coated paper is In addition, the printability becomes insufficient due to low smoothness, and if the average particle size is less than 0.3 μm, it is not practical because the slurry viscosity needs to be increased and an adhesive must be added. Further, the mixing ratio of the fine kaolin is 50% by weight based on the weight of all the pigments.
If it is less than 1, there is no effect of improving the glossiness and the smoothness of the obtained coated paper, so that it is not suitable. Incidentally, kaolin used in the present invention,
A commercially available product may be used, or kaolin having a coarse particle size may be pulverized to be fine.

The other pigments in the coating composition for the overcoat layer are not particularly limited, and kaolin, clay, heavy and light calcium carbonate having a large average particle size, satin white, titanium dioxide, aluminum hydroxide, At least one of ordinary pigments for coated paper such as talc and plastic pigment can be appropriately selected and used according to the purpose.

In the coating composition, a styrene / butadiene copolymer, a methyl methacrylate / butadiene copolymer, a (co) polymer of an acrylate and / or a methacrylate, and an ethylene / vinyl acetate copolymer may be used. One or more types of ordinary adhesives for coated paper, such as latexes such as polymers and further water-soluble adhesives such as starch, oxidized starch, phosphated starch, polyvinyl alcohol and carboxymethylcellulose, are appropriately used depending on the application. Used selectively. In addition, the compounding ratio of the adhesive is required to obtain a coated paper excellent in printability by increasing the coating amount in order to obtain high smoothness, and preferably 10 to 20 parts by weight with respect to 100 parts by weight of the pigment. Used.

Further, various additives such as a dispersant, a water-proofing agent, a defoaming agent, a coloring pigment, a dye, a pH adjuster and a viscosity adjuster may be appropriately combined and compounded in the coating composition.
There is no particular limitation on their use. The coating amount of the overcoat layer is usually 6 to 12 g / m ² per one side (12 to ² g / m ^{2 on} both sides).
4 g / m ² ) is preferably used and is coated on both sides.

The coating composition for the undercoat layer used in the present invention can be used without any particular limitation as long as it is generally used for coated paper. That is,
Pigments having an average particle size of usually 1 to 3 μm, such as kaolin, clay, calcium carbonate, talc, aluminum hydroxide, titanium dioxide and plastic pigment, and known dispersants used in the coating composition for the overcoat layer, A coating composition prepared by appropriately selecting and blending an adhesive, a dye, various auxiliaries, and the like may be used. The coating amount of the undercoat layer is preferably in the range of 3 to 8 g / m ² per side (6 to 16 g / m ^{2 on} both sides), and is applied on both sides of the base paper.

The base paper for coating containing cellulose pulp as the main component used in the present invention is manufactured by a paper machine by appropriately mixing various pulp such as bleached kraft pulp (coniferous and hardwood), groundwood pulp, and waste paper pulp. The paper used can be used arbitrarily. In addition, fillers such as talc and calcium carbonate, sizing agents, yield improvers,
Various chemicals used in papermaking such as paper strength enhancers, dyes, sulfuric acid bands, pitch control agents and the like may be contained, and any papermaking such as acidic papermaking, neutral papermaking, alkaline papermaking, etc. It may be manufactured by the method. Further, starch, polyvinyl alcohol, a surface sizing agent and the like may be applied to the surface of paper by various coaters such as a size press and a gate roll coater. In addition, the range of 50-160 g / m < ² > of the rice tsubo of a base paper is used suitably.

The base paper used in the present invention is described in J. Org. TAPP
I No. The Oken type smoothness according to 5 is adjusted in the range of 15 to 80 seconds, preferably 20 to 70 seconds. In order to increase the smoothness of the base paper, the nip pressure of the machine calender is usually increased to adjust.However, when the smoothness of the base paper is less than 15 seconds, the gloss and the smoothness of the coated paper obtained are overcoated. By optimizing the average particle size and compounding ratio of kaolin used in the coating layer, it is possible to maintain the desired level relatively easily, and to obtain a coated paper of low density and excellent quality, but the texture of the printed surface is The quality of coated paper obtained by a known method stays on par with the quality of
Also, when the smoothness of the base paper exceeds 80 seconds, the effect of improving the texture of the printed surface of the coated paper is slowed down, and the density of the coated paper is also increased due to the increase in the density of the base paper, and the rigidity is low. It is not suitable because it loses bulkiness and stiffness.

The coating method for providing the undercoat layer and the overcoat layer on the base paper is not particularly limited, and the blade is a bevel or vent type using an air knife coater, a roll coater, a paddle, or an inverter type blade coater. And other well-known coating devices such as various blade coaters such as a bill blade, a twin blade, a valid well blade, a short dowel blade, a rod blade and a chaplex are appropriately selected and used. Among these coating apparatuses, a blade coater is particularly suitable for producing coated paper in the present invention because a smoother coated surface can be obtained.

The coated paper obtained as described above is not subjected to any surface finishing with a polisher such as a soft calender, a super calender, etc.
142-75% specular gloss of 30-55% and J.I.
TAPPI No. Oken type smoothness by 5-B is 200
Finished in the range of ~ 600 seconds. If the glossiness is less than 30%, a matte tone is obtained, and if the glossiness is higher than 55%, it exceeds the semi-dull range, which is not suitable for the purpose of the present invention.

The glossiness and the Oken type smoothness of the finally obtained coated paper are adjusted by adjusting the smoothness of the base paper, the average particle size of kaolin as a pigment used in the overcoat layer, and the amount thereof. Is done. That is, the higher the smoothness of the base paper,
Also, since the average particle diameter of kaolin is reduced and the gloss ratio and smoothness can be increased as the blending ratio is increased,
The gloss and smoothness of the coated paper are adjusted by these combinations. On the other hand, if the Oken type smoothness of the coated paper is less than 200 seconds, the texture of the printed surface is poor, and if the smoothness is higher than 600 seconds, the smoothness of the base paper is also high, and as described above, the density of the coated paper is high. This is unsuitable because it increases the stiffness, lowers the stiffness and loses the waist.

As described above, the coated paper according to the present invention can easily produce a coated paper having a dull or semi-dal tone, a high smoothness, a low density, a high bulk and excellent printing characteristics.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, of course, are not intended to limit the present invention. It should be noted that all percentages and parts in Examples and Comparative Examples indicate weight percentages and parts by weight in terms of solid content.

The test methods for the pigment, base paper and coated paper used in the present invention are as follows. (1) Average Particle Diameter of Pigment Measured using a SA-CP2 centrifugal particle size analyzer (manufactured by Shimadzu Corporation).

(2) Glossiness According to JIS P 8142 (Test method for 75 ° specular glossiness of paper and paperboard). (3) Smoothness TAPPI No. 5 (Test method for smoothness and air permeability of paper and paperboard using an air micrometer type tester). However, it was measured using (B) Oken type smoothness tester.

(4) Printing Surface Texture Printing is performed using a commercially available test printing ink on a Roland two-color printing press (FRZFO-1 type, manufactured by Roland), and the texture of the printing surface is visually observed and determined. Result 1
The evaluation was made on a scale of 5 to 5, and the average value of the evaluation points of the three persons was displayed in increments of 0.5. The larger the value, the better.

Papermaking of base paper for coating (1) Base paper for coating A Hardwood bleached kraft pulp (LBKP) Light calcium carbonate (manufactured by the company) is added to 100% pulp so that the ash content becomes 4%. A paper strength enhancer (Harima EX360, manufactured by Harima Chemicals), a fixing agent (Kate F, manufactured by Oji Constarch) and the like are added, and the paper is formed by a known paper machine.
After applying 2.0 g / m ² with a size press and drying,
A calender with a nip linear pressure of 40 kg / cm on a machine calender consisting of two metal rolls, and a rice basis weight of 80 g
/ M ² of base paper. The smoothness of the base paper for coating was 25 seconds for the felt (hereinafter, referred to as F) surface and 20 seconds for the wire (hereinafter, referred to as W) surface, and was used for Examples 1 to 5 and Comparative Examples 1 to 3. Was.

(2) Coating base paper B With the same pulp composition as coating base paper A except that the nip pressure of the machine calendar is set to 75 kg / cm and the smoothness of the coating base paper is set to F / W = 45/40 seconds. Similarly, base paper for coating B
Was prepared and subjected to Example 6.

(3) Coating base paper C The same pulp composition as coating base paper A is used except that the nip pressure of the machine calendar is set to 100 kg / cm and the smoothness of the coating base paper is set to F / W = 62/52 seconds. A base paper for coating C was produced in the same manner and provided for Example 7.

Undercoat Coating Composition Sodium polyacrylate (Aron T-4) is used as a dispersant in the following pigment comprising heavy calcium carbonate and kaolin.
0), disperse evenly in water using a dellitter, then add SBR latex and oxidized starch, further add preservatives, dyes and other auxiliaries and water, and finally with aqueous sodium hydroxide Adjust the pH to 9.5,
The mixture was sufficiently mixed and dispersed to prepare an undercoating coating composition having a solid content of 60%, which was used in Examples and Comparative Examples.

Heavy calcium carbonate (average particle size: 1.30 μm, pulverized) 90 parts Kaolin (HT kaolin, manufactured by Engelhard) 10 parts Dispersant (Aron T-40, manufactured by Toa Gosei) 0.03 parts SBR latex (JSR2300) , Nippon Synthetic Rubber) 8 parts Oxidized starch (Oji Ace A, Oji Cornstarch) 3 parts Preservatives, coloring pigments, dyes, etc.

Coating composition for overcoating Example 1 Sodium polyacrylate (Aron T-40) as a dispersant was added to the following kaolin, and the resulting mixture was uniformly dispersed in water using a dellitter to obtain a solid content concentration of 70%. Prepared, then add heavy calcium carbonate, then add SBR latex and oxidized starch, add preservatives, color pigments, dyes and other auxiliaries and water, and finally with aqueous sodium hydroxide The pH was adjusted to 9.5, and the mixture was sufficiently mixed and dispersed to adjust the solid content to 63%.

Kaolin (Kao Fine 90, manufactured by Seal Kaolin, average particle size: 0.41 μm) 30 parts Kaolin (Kao Fine, manufactured by Seal Kaolin, average particle size: 0.59 μm) 30 parts Kaolin (Comalco Kaolin, manufactured by Comalco, average) 20 parts Heavy calcium carbonate (average particle diameter 1.30 μm, pulverized) 20 parts Dispersant (Aron T-40, manufactured by Toagosei Co., Ltd.) 0.05 part SBR latex (JSR2621B, manufactured by Nippon Synthetic Rubber) 14.5 parts Oxidized starch (Oji Ace A, manufactured by Oji Cornstarch) 2 parts Preservatives, coloring pigments, dyes, etc.

Example 2 An overcoat coating composition was prepared in the same manner as in Example 1 except that the pigment of the overcoat coating composition was as follows. Kaolin (Kao Fine 90) 40 parts Kaolin (Kao Fine) 30 parts Kaolin (Comalco Kaolin) 10 parts Heavy calcium carbonate (average particle size 1.30 μm, pulverized) 20 parts

Example 3 An overcoat composition was prepared in the same manner as in Example 1 except that the pigment of the overcoat composition was as follows. Kaolin (Kao Fine 90) 60 parts Kaolin (Kao Fine) 20 parts Kaolin (Comalco Kaolin) 10 parts Heavy calcium carbonate (average particle size 1.30 μm, pulverized) 10 parts

Example 4 Sodium polyacrylate (Aron T-40) was added as a dispersant to the following kaolin, and the mixture was uniformly dispersed in water using a dellitter to prepare a solid content concentration of 70%. Add SBR latex and oxidized starch, further add preservatives, color pigments, dyes and other auxiliaries and water, and finally adjust the pH to 9.5 with aqueous sodium hydroxide, mix well and disperse The concentration was adjusted to 63%. The amounts of sodium polyacrylate, SBR latex and starch added were the same as in Example 1. Kaolin (Kao Fine 90) 90 parts Kaolin (Komarco Kaolin) 10 parts

Examples 5 to 7 Kaolin (Kaofine 9) was used as a pigment in the topcoat coating solution.
An overcoating solution was prepared in the same manner as in Example 4, except that only 100 parts of 0) were used.

Comparative Example 1 An overcoating composition was prepared in the same manner as in Example 1 except that the pigment of the overcoating solution was formulated as follows. Kaolin (α-coat, made by ECC, average particle size 1.30 μm) 55 parts Kaolin (comalco kaolin) 30 parts Heavy calcium carbonate (average particle size 1.30 μm, pulverized) 15 parts

Comparative Example 2 An overcoating composition was prepared in the same manner as in Example 1 except that the pigment of the overcoating solution was prepared as follows. Kaolin (Kao Fine) 40 parts Kaolin (α coat) 40 parts Heavy calcium carbonate (average particle size 1.3 μm, crushed) 20 parts

Comparative Example 3 An overcoating composition was prepared in the same manner as in Example 1 except that the pigment of the overcoating solution was prepared as follows. Kaolin (Kao Fine 90) 45 parts Kaolin (α coat) 35 parts Heavy calcium carbonate (average particle size 1.30 μm, crushed) 20 parts

Coating method on base paper for coating The above-mentioned coating composition for undercoating and topcoating was double-coated on both sides of base paper by a blade method under the following conditions. Coating method: Undercoat ・ ・ ・ Short dowel coater Top coat ・ ・ ・ Valid well coater Coating speed: Undercoat ・ ・ ・ 1000m / min Top coat ・ ・ ・ 1000m / min Coating amount: Undercoat ・ ・ ・ 5g / m ² (both sides 10g /
m ² ) Top coat: 8 g / m ² (16 g / m ^{2 on} both sides) Drying method: For both the undercoat and the top coat, the coated paper is dried by a combination of an air dryer and a cylinder drier. Was adjusted so that the water content of the coated paper was 5%.

The coated paper obtained as described above was evaluated as it was without performing surface finishing such as calendering, and the results are shown in Table 1.

[0043]

[Table 1]

As can be seen from Table 1, both surfaces of the present invention using a fine kaolin having an average particle size in the range of 0.3 to 0.8 μm and a compounding ratio of 50% by weight or more as the pigment in the top coating composition. The coated paper has a density of 1.00 g / cm in a dull tone to a semi-dull tone having a gloss of 30 to 55%.
Maintained at a low level of ³ or less, it is bulky and has excellent surface properties with smoothness of 200 seconds or more (Examples 1 to 3).
7) In particular, when the ratio of fine kaolin is high and the smoothness of the base paper is high, the coated paper can be provided with more excellent surface properties and the printed surface texture is particularly excellent (Example) 6-7). On the other hand, when the ratio of fine kaolin in the overcoat pigment is less than 50% by weight, the glossiness is low, the matte is in the category, and the smoothness is inferior (Comparative Examples 1 to 3).

[0045]

According to the present invention, a double-sided coated paper which is bulky and has a high smoothness in a dull tone to a semi-dull tone, and has excellent printability and printability without the need for extensive remodeling of equipment.
There is an effect that a method that can be manufactured without using expensive raw materials and chemicals can be provided.

Claims (1)

(57) [Claims] 1. A coating composition comprising a pigment and an adhesive as main components is coated on both sides of a base paper comprising cellulose pulp as a main component.
In a method for producing a double-sided coated paper comprising coating and drying as an undercoat layer and an overcoat layer, the Oken type smoothness is 15
Using base paper for ~ 80 seconds, average particle size 0.3 ~ 0.8μm
By applying a coating composition containing at least 50% by weight of kaolin per weight of the total pigment as an overcoat layer, so that the glossiness of the coated surface is 30 to 55% and the Oken type smoothness is 200.
A method for producing a double-sided coated paper, which is performed for about 600 seconds.