JPH06235194A - Production of coated paper for printing - Google Patents

Abstract

PURPOSE:To obtain coated paper having strong stiffness, high gloss and excellent printing workability. CONSTITUTION:Coated paper for printing is produced by coating base paper with a coating composition composed mainly of a pigment and an adhesive, drying the coating layer and subjecting to calender finishing. In the above process, the pigment contains (A) 50-98 pts.wt. kaolin having plate form and having a diameter and an aspect ratio (diameter/thickness ratio) satisfying the following formulas (1) and (2) and (B) 2-30 pts.wt. hollow plastic pigment and the coating composition is incorporated with 10-50wt.% (based on the pigment) water-soluble binder as the adhesive. 12<=(diameter/thickness)<=20...(1), 0.5mum<=(diameter)<=3mum...(2).

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 a coated paper for printing, and more particularly to a method for producing a coated paper for printing which has a high rigidity, so-called stiffness, and a high gloss with excellent printing operability.

[0002]

2. Description of the Related Art In recent years, environmental issues have been emphasized, and weight saving of paper products is an important issue from the standpoint of protecting paper resources. On the other hand, with the trend toward visualization, colorization, and high quality of printed matter, particularly in the case of coated paper for printing, improvement in glossiness and smoothness of the coated surface has been demanded. In order to reduce the weight of the coated paper, it is necessary to reduce the amount of base paper and the amount of coating, and as a result, the gloss and the thickness of the paper are reduced, so that the stiffness of the paper is reduced. This not only lowers the printing workability but also impairs the commercial value of the finished printed matter. It is a current problem to solve the above-mentioned difficulties caused by the weight reduction of coated paper.

[0003]

SUMMARY OF THE INVENTION In view of the above situation, the present invention is to provide a method for producing a coated paper for printing which has a high smoothness and a high gloss and has a strong stiffness.

[0004]

Means for Solving the Problems In a method for producing a coated paper for printing, which comprises coating a base paper with a coating composition containing a pigment and an adhesive as main components and calendering the coated composition, the pigment is used as a pigment.
Kaolin 50 which is plate-shaped and whose diameter-thickness ratio (aspect ratio) and diameter satisfy the following formulas (1) and (2):
% To 98 parts by weight and 2 to 30 parts by weight of hollow plastic pigment, and a water-soluble binder as an adhesive is blended in an amount of 10 to 50% by weight with respect to the pigment. . 12 ≦ diameter / thickness ≦ 20 (1) 0.5 μm ≦ diameter ≦ 3 μm (2)

[0005]

The present inventors have been keen to obtain a more excellent coated paper by suppressing the weight reduction of the coated paper for printing, that is, suppressing the deterioration of gloss and paper stiffness due to the reduction of the base paper and the coating amount. I did a research. As a result, they have found that a desired coated paper for printing can be obtained by blending a specific pigment and an adhesive in the coating composition.

That is, 50 to 98 parts by weight of kaolin having an aspect ratio and a diameter of 12 ≦ aspect ratio ≦ 20, 0.5 μm ≦ diameter ≦ 3 μm, and 10 to 50% by weight of a water-soluble binder with respect to a pigment are applied. By including it in the product, it was possible to obtain a coated paper having a strong stiffness.

Here, the aspect ratio is the ratio of the diameter and the thickness of the plate-like pigment, and is usually expressed as follows. Aspect ratio = diameter / thickness

Kaolin having an aspect ratio of about 10 has been used in a relatively large amount so far, but in the present invention, if the aspect ratio is less than 12, a desired paper texture cannot be obtained. On the other hand, when the ratio exceeds 20, the stiffness of the paper becomes strong, but a coating layer with few voids between pigment particles is formed, which causes ink imperfection due to poor water absorption during printing (offset printing), which is preferable. Absent. Therefore, the aspect ratio is specified as described above.

In general, pigment particles having a relatively large aspect ratio, such as kaolin, are regularly oriented in the horizontal direction in the coating layer provided on the base paper. Further, due to this orientation, resistance to bending stress (paper stiffness) occurs. Incidentally, the larger the aspect ratio, the stronger the stiffness of the paper, although it depends on the diameter.

Even if the aspect ratio satisfies the above definition, if the diameter of kaolin is less than 0.5 μm,
It is not possible to obtain the desired strong stiffness. This is probably because the diameter of the pigment is small, that is, the pigment particles are small, so that the horizontal orientation is unlikely to occur. On the other hand, when the thickness exceeds 3 μm, the paper stiffness becomes strong, but it is difficult to form a smooth surface, and sufficient glossiness and smoothness cannot be obtained.

Further, when the content of kaolin is less than 50 parts by weight, the horizontal orientation of the kaolin particles is hindered by the other pigment particles, and the effect cannot be exhibited as described above.

In the present invention, it is difficult to obtain a desired paper stiffness by only specifying kaolin as described above, especially in the case of thin coated paper. Therefore, as a result of various studies, it was found that by adding a large amount of a water-soluble binder as an adhesive, paper stiffness is enhanced. In the present invention, a water-soluble binder is used in an amount of 10 to 50% by weight based on the pigment.
It is to be compounded. When it is less than 10% by weight, the desired paper stiffness cannot be obtained. On the other hand, when it exceeds 50% by weight, the paper stiffness becomes strong, but most of the voids in the coating layer are filled with the binder. This is not preferable because it causes poor water absorption during printing and induces a decrease in gloss.

As described above, according to the present invention, the desired paper texture can be obtained by specifying the aspect ratio and the diameter of kaolin, the number of parts to be mixed, and the number of parts of the water-soluble binder. On the other hand, although the desired paper stiffness is obtained, due to the influence of the water-soluble binder,
The desired gloss was not obtained. Therefore, as a result of further studies as a measure for improving gloss, as a pigment, by adding 2 to 30 parts by weight of a hollow plastic pigment, a coated paper for printing having a very high gloss without deteriorating the paper stiffness. I was able to get By the way, when the amount of the plastic pigment is less than 2 parts by weight, the desired gloss cannot be obtained, and when it exceeds 30 parts by weight, the viscosity of the coating composition increases and the operability is impaired.

The reason why the plastic pigment contributes to the improvement of gloss is speculated as follows. That is, in general, since the plastic pigment is thermoplastic, it is considered that it has the property of easily exhibiting a high gloss by the calendering treatment as compared with the mineral pigment. Furthermore, the hollow plastic pigment not only has the property of adding high gloss, but also has a high optical refractive index because the particles are hollow, and therefore has the effect of suppressing the decrease in opacity. is there.

As the pigment, in addition to the above specific pigments, ordinary kaolin, acicular light calcium carbonate, cubic light calcium carbonate, amorphous heavy calcium carbonate, titanium dioxide, zinc oxide, aluminum hydroxide. Can be used as appropriate.

As the adhesive agent, a water-soluble binder is used as a main component, which includes oxidized starch, positive starch, esterified starch, starches such as dextrin,
A synthetic resin adhesive such as polyvinyl alcohol, proteins such as casein, soybean protein, and synthetic protein are used. In combination therewith, for example, a conjugated diene-based copolymer latex such as a styrene-butadiene copolymer, an acrylic-based copolymer latex such as a polymer or copolymer of acrylic ester, a vinyl-based such as ethylene vinyl acetate polymer, etc. Polymer latex or various synthetic resin polymers called alkali-soluble, alkali-swellable or alkali-insoluble polymer latex obtained by modifying these polymer latexes with a functional group-containing monomer such as carboxyl group One or more of ordinary adhesives for coated papers such as the above are appropriately selected and used.

If necessary, various auxiliary agents such as defoaming agents, colorants, release agents, and flow-altering agents may be added to the coating composition. The solid content concentration of the coating composition is generally 30 to 7
It is about 5% by weight, but in consideration of operability, 35 to 7
A range of 0% by weight is desirable.

The coating composition thus prepared is applied onto a base paper, but the basis weight of the base paper is not particularly limited, and is generally 30 to 400 g / m ^2.
It can be appropriately selected and used according to the purpose within a range of
In the case of the present invention, it is particularly aimed at reducing the weight of coated paper, and when applied to a material having a weight of about 30 to 80 g / m ² ,
The effect is remarkable.

The paper machine is not particularly limited, and may be a Fourdrinier machine, a twin wire machine, a cylinder machine, or a multilayer cylinder machine. The papermaking method may be any of acid papermaking, neutral papermaking, weak alkaline papermaking, and the like. Needless to say, a neutral base paper containing high-yield pulp, a base paper containing recovered pulp, and the like can also be used. Further, a base paper pre-coated with a paper machine on-machine coater or a size press, or a base paper undercoated with an off coater can be used.

The coating apparatus used in the production of general coated paper is, for example, a blade coater, an air knife coater, a bar coater, a bill blade coater, a curtain coater, a die slot coater, a gravure coater, a chanplex coater, An on-machine or off-machine coater provided with a double-sided or single-sided coating device such as a size press coater is appropriately used. In coating, the coating composition is coated on the base paper in a single layer or multiple layers.

Various methods such as steam heating, hot air heating, gas heater heating, high frequency heating, electric heater heating, infrared heater heating, laser heating, electron beam heating, etc. can be used for drying the wet coating layer. A drying method can be appropriately adopted.

The coated paper thus obtained is subjected to a calendering treatment, but the calendering pressure and the number of nips are not particularly limited, and are appropriately selected depending on the required quality. As the calender in the present invention, various calenders such as a super calender, a gross calender, and a soft compact calender are used in the form of on-machine or off-machine. The on-machine calender referred to here is not limited to a paper machine, but includes an on-machine calender incorporated in a coating machine.

Further, in the calendering process, if the surface temperature of the metal roll is 100 to 250 ° C., the desired glossiness can be maintained even if the nip number and the nip pressure are reduced and the tightness is lowered. At the same time, it is effective for improving the stiffness of the paper and can be a more preferable embodiment.

[0024]

The present invention will be described in more detail with reference to the following examples, but the scope of the invention is not limited thereto.
In addition, unless otherwise indicated, the part and% in an example show a weight part and weight%, respectively.

Example 1 A pigment having an aspect ratio of 18 and a diameter of 1.8.
90 parts of kaolin that is μm, plastic pigment 1
0 parts and 0.2% (solid content) of sodium polyacrylate to the pigment as a dispersant were added and dispersed using a Choles disperser to prepare a pigment slurry having a solid content of 65%. To this slurry, 35 parts of oxidized starch and 5 parts of styrene-butadiene copolymer latex solid content were added as a water-soluble adhesive, and water was further added to obtain a coating liquid having a solid content concentration of 50%. This coating liquid is applied to a high-quality base paper of 50 g / m ² of tsubo (both sides) by a blade coater so that the dry weight per side is 8 g / m ² , and dried with a hot air dryer at 120 ° C. to obtain a water content of 6 % Coated on both sides. The double-sided coated paper thus obtained was passed through a calender composed of a metal roll and an elastic roll at a surface temperature of the metal roll of 70 ° C. to pass the paper and smooth the paper. About the obtained coated paper,
The following quality evaluation was performed, and the results are shown in Table 1.

Example 2 A coated paper was obtained in the same manner as in Example 1, except that the aspect ratio of kaolin was changed to 14. The quality results of the coated papers obtained are shown in Table 1.

Example 3 The procedure of Example 1 was repeated except that the kaolin content was 75 parts and the plastic pigment content was 25 parts.
A coated paper was obtained in the same manner as in Example 1. The quality results of the coated papers obtained are shown in Table 1.

Example 4 A coated paper was obtained in the same manner as in Example 1 except that the mixing ratio of kaolin was 97 parts and the mixing ratio of plastic pigment was 3 parts. The quality results of the coated papers obtained are shown in Table 1.

Example 5 A coated paper was obtained in the same manner as in Example 1, except that the mixing ratio of the oxidized starch was changed to 15 parts. The quality results of the coated papers obtained are shown in Table 1.

Example 6 A coated paper was obtained in the same manner as in Example 1 except that the mixing amount of oxidized starch was changed to 45 parts. The quality results of the coated papers obtained are shown in Table 1.

Example 7 Coating was carried out in the same manner as in Example 1 except that the content of kaolin was 55 parts, the content of calcium carbonate was 35 parts, and the content of plastic pigment was 10 parts. Got the paper. The quality results of the coated papers obtained are shown in Table 1.

Example 8 A coated paper was obtained in the same manner as in Example 1, except that the kaolin had an aspect ratio of 15 and a diameter of 1.0 μm. The quality results of the coated papers obtained are shown in Table 1.

Example 9 A coated paper was obtained in the same manner as in Example 1 except that the kaolin had an aspect ratio of 19 and a diameter of 2.5 μm. The quality results of the coated papers obtained are shown in Table 1.

Example 10 A coated paper was obtained in the same manner as in Example 1 except that the surface temperature of the metal roll of the calender was 120 ° C. The quality results of the coated papers obtained are shown in Table 1.

Comparative Example 1 A coated paper was obtained in the same manner as in Example 1, except that the aspect ratio of kaolin was 10 and the diameter was 1.1 μm. The quality results of the coated papers obtained are shown in Table 1.

Comparative Example 2 A coated paper was obtained in the same manner as in Example 1, except that the kaolin had an aspect ratio of 25 and a diameter of 2.4 μm. The quality results of the coated papers obtained are shown in Table 1.

Comparative Example 3 A coated paper was obtained in the same manner as in Example 1 except that the plastic pigment was not mixed and the kaolin content was 100 parts. The quality results of the coated papers obtained are shown in Table 1.

Comparative Example 4 A coated paper was obtained in the same manner as in Example 1, except that the mixing ratio of the oxidized starch was changed to 5 parts. The quality results of the coated papers obtained are shown in Table 1.

Comparative Example 5 A coated paper was obtained in the same manner as in Example 1 except that the amount of the oxidized starch was changed to 55 parts. The quality results of the coated papers obtained are shown in Table 1.

Comparative Example 6 A coated paper was obtained in the same manner as in Example 1 except that the aspect ratio of kaolin was 13 and the diameter was 0.3 μm. The quality results of the coated papers obtained are shown in Table 1.

Comparative Example 7 A coated paper was obtained in the same manner as in Example 1 except that the diameter of kaolin was changed to 3.4 μm. The quality results of the coated papers obtained are shown in Table 1.

Comparative Example 8 Example 1 was repeated except that the kaolin content was 40 parts and the calcium carbonate content was 50 parts.
A coated paper was obtained in the same manner as. The quality results of the coated papers obtained are shown in Table 1.

Comparative Example 9 A coated paper was prepared in the same manner as in Example 1 except that the kaolin content was 65 parts and the plastic pigment was 35 parts. Since the viscosity was too high, the workability was hindered.

[Measurement Method and Evaluation Method] [Glossiness of blank paper] The glossiness was measured according to JIS-P8142.
The higher the value, the better the gloss. [Clark stiffness] Clark stiffness meter (made by Kumagai Riki Kogyo Co., Ltd.)
Was measured using. The larger the value, the stronger the paper stiffness.

[Water Absorption] Printing was performed using an offset four-color printing machine, and the surface of the obtained printed matter was visually observed and evaluated. ○ ・ ・ ・ Good × ・ ・ ・ Poor [Diameter / Thickness] JEOL electron microscope (JSM-T3
It was calculated by observing the surface at (00) and visually measuring about 1000 particles.

[0046]

[Table 1]

[0047]

As is clear from the results of the examples shown in Table 1, the coated paper for printing obtained by the method of the present invention has strong gloss and paper stiffness, and is excellent in printing workability. It was

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyasu Sasari 4-3-1 Jōkoji, Amagasaki City, Hyogo Prefecture Kanzaki Paper Co., Ltd. Kanzaki Mill

Claims (2)

[Claims] 1. A method for producing a coated paper for printing, which comprises coating a base paper with a coating composition containing a pigment and an adhesive as main components, and calendering the coated paper. The ratio of diameter to thickness (aspect ratio) and diameter are 50 to 98 parts by weight of kaolin and 2 to 30 parts by weight of hollow plastic pigment, which satisfy the following formulas (1) and (2):
A water-soluble binder as an adhesive is added to the pigment in an amount of 10 to 50
A method for producing a coated paper for printing, which comprises being blended in a weight percentage. 12 ≦ diameter / thickness ≦ 20 (1) 0.5 μm ≦ diameter ≦ 3 μm (2) 2. The method for producing coated paper for printing according to claim 1, wherein the surface temperature of the metal roll of the calender during calendering is 100 to 250 ° C.