JP2003313796A - Method for producing cast coated paper and cast coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing cast coated paper capable of improving printability and operating speed while sustaining feeling of gloss. <P>SOLUTION: The method for producing the cast coated paper is produced by coating a coating solution C containing pigment and drying it to form a coated layer on one side of a base paper 1 and then rewetting the coated layer by a rewetting solution W, and then subjecting the base paper in the wetted state to a surface gloss finishing step by pressing the layer to a heated mirror face drum 5, wherein the coating solution C contains 5 to 20 wt.% of heavy calcium carbonate per the total pigment and 5 to 25 wt.% of cubic light calcium carbonate with 0.1 to 1.0 μm average particle diameter. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing cast coated paper and cast coated paper.

[0002]

2. Description of the Related Art Cast coated papers are widely used as high-grade printing papers because of their extremely high surface gloss and high smoothness. As typical methods for producing the cast coated paper, there are a wet cast coating method, a gelling cast coating method and a rewet cast coating method. Wet cast coating method, after applying the cast coating liquid on the base paper, while the coating layer is in a wet state,
In this method, the surface gloss treatment is carried out by bringing it into pressure contact with a heated mirror surface drum. In the gel cast coating method, the base paper is coated with the cast coating solution, and then the coating layer is gelled, and the gelled coating layer is pressed against a heated mirror surface drum to give a surface gloss treatment. Is the way to do. The rewet cast coating method is a method of coating a base paper with a cast coating liquid, drying the coating layer once, and then making the coating layer wet with a rewetting liquid, and coating the rewetting state. This is a method in which the layer is pressed against a heated mirror drum to perform surface gloss treatment. Both methods are common in that the wet coating layer is brought into contact with a heated mirror surface drum to dry the water in the coating layer and to develop the gloss of the surface. As described above, in the method for producing cast-coated paper, the water content and rewetting liquid in the coating layer evaporate toward the non-coating layer side when contacting with the mirror surface drum. Therefore, if the drum temperature is raised and the temperature of the coating layer is rapidly increased in order to shorten the drying time, the amount of water that evaporates becomes excessive relative to the amount of water that permeates to the non-coating layer side, and It cannot be transmitted to the non-coating layer side and evaporates to the coating layer side to generate pinholes in the coating layer. Therefore, it is required to operate at a very low speed as compared with other methods for producing printing paper such as art paper or coated paper which is dried from both sides.

Under the present circumstances, among the above methods, the rewet cast coating method temporarily dries the coating layer, so that it is possible to make pressure contact with the mirror surface drum at a relatively high temperature, and an operating speed of about 80 m / min. And the fastest.
Therefore, making the rewet cast coating method possible to operate at higher speed is very significant in the production of cast coated paper.

[0004]

However, even in the rewet cast coating method, since the coating layer is once dried and then rewet, the wet state of the surface may not be uniform, resulting in a portion with excessive water content. In some cases, pinholes may occur in the coating layer.

By the way, the easiness of permeation of water to the non-coating layer side largely depends on the pigment component contained in the coating layer. Conventionally, pigments to be contained in a coating liquid are generally composed mainly of kaolin and light calcium carbonate. Kaolin is a thin-layer substance with a very small particle size, so including it in a coating solution will give cast coated paper with an extremely excellent glossiness, but the coating layer has a moisture permeability. Will be extremely bad. On the other hand, light calcium carbonate has a larger particle size than kaolin, and by using this in combination with kaolin, the water permeability and printability of the coating layer can be improved. However, when light calcium carbonate is contained, it becomes difficult to obtain a glossy feeling. That is, if the content of the light calcium carbonate is increased in order to improve the operation speed and printability, the glossiness is decreased, and if the content of kaolin is increased to increase the glossiness, the operation speed is increased. descend. Therefore, it is extremely difficult for the pigment of the conventional component to further improve the printability and the operating speed while maintaining the glossy feel of the cast coated paper.

[0006] Therefore, the inventors of the present invention have studied and studied the pigment in order to improve the printability and the operation speed without lowering the glossiness of the cast coated paper. As a result, the heavy calcium carbonate and cubic are used as the pigment. The inventors have found that the above problems can be solved by using a light calcium carbonate in the form of a combination thereof, and completed the present invention.

[0007]

[Means for Solving the Problems] That is, claim 1 thereof.
The invention described, on the base paper, a coating liquid containing a pigment is applied and dried to form a coating layer, and the coating layer is brought into a wet state with a rewetting liquid and brought into pressure contact with a heated mirror surface drum. A method for producing cast-coated paper, which comprises surface gloss treatment, comprising 5 to 20% by weight of heavy calcium carbonate and 5 parts of cubic light calcium carbonate having an average particle diameter of 0.1 to 1.0 μm in all pigments.
The method for producing cast-coated paper is characterized in that the content is -25% by weight.

The invention according to claim 2 is the method for producing cast coated paper according to claim 1, wherein the wet coating layer is pressed against a mirror surface drum at a speed of 100 m / min or more to perform surface gloss treatment. Is.

According to a third aspect of the present invention, a coating liquid containing a pigment is applied onto a base paper and dried to form a coating layer, and the coating layer is wetted with a rewetting liquid. A cast-coated paper obtained by press-contacting with a heated mirror surface drum to obtain a surface gloss treatment, wherein 5 wt.
The cast coated paper is characterized by containing 5 to 25% by weight of cubic light calcium carbonate with 20% by weight and an average particle diameter of 0.1 to 1.0 μm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. First, the coating liquid will be described. In the method for producing cast-coated paper of the present invention, heavy calcium carbonate and cubic light calcium carbonate are contained in the pigment constituting the coating liquid. Of course, in addition to the pigment, various adhesives, auxiliaries, and the like are used as needed to generate the coating liquid.

Heavy calcium carbonate has high dispersibility and can increase the printing surface strength, and has an effect of improving printability. Also, since ground calcium carbonate is relatively inexpensive, its use also reduces manufacturing costs. In the present invention, 5 to 20% by weight of heavy calcium carbonate is contained in all the pigments of the coating liquid. If the content is more than 20% by weight, pinholes and uneven gloss are likely to occur, and if it is less than 5% by weight, desired printability cannot be improved.

Here, in the present invention, the particle size of the heavy calcium carbonate is not limited, but is 0.5 to 1.0.
It is preferably in the range of μm. If the particle size of the ground calcium carbonate is less than 0.5 μm, it is difficult to obtain desired printability, and if it exceeds 1.0 μm, pinholes are likely to occur.

On the other hand, when cubic light calcium carbonate is contained in the coating layer due to the characteristics of its shape, the water permeability of the coating layer is remarkably improved. Further, when a large amount is contained in the coating liquid, it becomes difficult to obtain a glossy feeling, but up to a certain amount of content, a glossy feeling comparable to that of kaolin can be maintained. Therefore, cubic light calcium carbonate is very suitable for improving printability and operating speed by suppressing pinholes while maintaining the same glossiness as conventional cast coated paper. In the present invention, the cubic light calcium carbonate in the coating liquid is contained in an amount of 5 to 25% by weight of all pigments. It is preferably contained in an amount of 5 to 20% by weight. When the content is more than 25% by weight, the glossy feeling tends to be deteriorated, and when the content is less than 5% by weight, pinholes are likely to occur and desired printability cannot be improved. In this case, the cubic light calcium carbonate has an average particle diameter of 0.1 to 1.0 μm, particularly preferably 0.15 to 0.8 μm. 0.1
If it is less than μm, the pressure-bonding strength is lowered, so that it is necessary to increase the content of the adhesive. If the amount of the adhesive is increased in this way, the water permeability is lowered and pinholes are likely to occur. On the other hand, when it exceeds 1 μm, the glossiness is significantly reduced.
The average particle size can be measured and calculated by a known Microtrac device.

The cubic light calcium carbonate referred to in the present invention is a light calcium carbonate having a cubic crystal form. Since such a crystalline form of calcium carbonate is usually light calcium carbonate, it may be simply referred to as cubic calcium carbonate. The cubic light calcium carbonate in the present invention does not mean that cubic calcium carbonate is excluded.

Here, in the present invention, in addition to the above-mentioned heavy calcium carbonate and cubic light calcium carbonate,
Kaolin, clay, calcined clay, amorphous silica, zinc oxide, aluminum oxide, aluminum hydroxide, anisotropic light calcium carbonate, satin white, aluminum silicate, magnesium silicate, magnesium carbonate, diatomaceous earth, styrene plastic pigment, urea plastic Pigments, benzoguanamine-based plastic pigments and the like, which are conventionally known, are used in combination within the scope of the present invention, that is, 90 to 60% by weight based on all pigments. Among them, kaolin is conventionally known to be a pigment having particularly excellent glossiness as described above, and it is desirable to use kaolin together. The content of kaolin is preferably 80 to 60% by weight.

As described above, in the present invention, the adhesive is used in the same manner as in the prior art to form the coating liquid, but as the adhesive, the conventionally known adhesive used in the production of cast coat can be used without any problem. be able to. Specific examples thereof include conventionally known alkali-sensitive synthetic resin emulsions, alkali-insensitive synthetic resin emulsions, oxidized starch, esterified starch, oxygen-modified starch, starches such as cationized starch, proteins such as soybean protein, Examples include fibrin derivatives such as carboxyethyl cellulose and hydroxyethyl cellulose, polyvinyl alcohol and the like. These can be used alone or in combination according to the conventionally known techniques.

In addition, in the coating liquid according to the present invention, if necessary, a viscosity adjusting agent, a defoaming agent, a coloring agent, a release agent, a flow modifier, etc. may be added in accordance with conventionally known techniques. Include.

The solid component concentration of the coating liquid according to the present invention is not particularly limited, but in consideration of coatability, it is 2
It is preferably about 0 to 70% by weight.

Next, a specific manufacturing process of the cast coated paper according to the present invention will be described with reference to FIG.
As shown in the figure, the coating liquid C according to the above description is applied onto the base paper 1 with an air knife coater, and the drier 3 is used.
And dried to form a coating layer on the base paper. The coating amount is preferably ²⁰ to 50 g / m ² . In addition to the above air knife coater, various known coaters such as a blade coater, a roll coater, a brush coater, a chanplex coater, a bar coater, and a gravure coater can be used as the coater.

Here, the base paper for forming the coating layer is not particularly limited, but in the cast coating method, since water must evaporate from the back surface of the paper through the paper layer, it is possible to obtain a paper having excellent air permeability. Is preferable. There is no problem as long as it is an acid paper or a neutral paper which is generally used as a coated base paper. Here, the base paper may be a pre-coated coated paper, and the pre-coated layer may be subjected to smoothing treatment such as calendering or brushing.

After the coating layer is formed on the base paper 1, the rewetting liquid W is sprayed on the coating layer using the jet nozzle 4 or the like to rewet and plasticize the coating layer. Try. The rewetting liquid used for rewetting the coating layer is not particularly limited. The rewetting liquid used in the conventionally known method for producing a cast coat can be used.
As a specific example, a liquid obtained by dispersing polyethylene emulsion, a salt of fatty acid or its derivative, microcrystalline wax, funnel oil or the like as water as a release agent can be mentioned. Further, a phosphate such as sodium hexametaphosphate, an organic acid, or a salt of an organic acid can be used in combination for promoting the plasticization of the coating layer after drying again.

After rewetting the coating layer, the heated coating layer is pressed against the mirror-finished drum 5 whose heated surface is mirror-finished to copy the mirror surface of the drum and dry the coating layer.

The temperature of the mirror surface drum is 90 to 110.
C. or higher, preferably 95 to 105.degree. In this case, in the present invention, no pinhole is generated even if the speed at the time of drum pressure contact is as high as 100 to 150 m / min, which has been difficult in the past. Of course, pinholes do not occur even at speeds of 100 m / min or less.

Therefore, in the above-mentioned method for producing cast-coated paper according to the present invention, the operating speed is 100 to 100.
It is desirable to manufacture it at 150 m / min. this is,
Operating speed of conventional rewet cast coating method is 80m
Considering that it was about 1 / minute, it means that the manufacturing can be performed in an extremely short time.

[0025]

EXAMPLES The cast coated paper produced according to the present invention (Example) and the cast coated paper not according to the present invention (Comparative Example) were examined for glossiness and pinhole generation.

(Production of Samples) Heavy calcium carbonate (FMT90: manufactured by Phimatech) and cubic light calcium carbonate (Brilliant S15: manufactured by Shiraishi Industry Co., Ltd./Shiraishi Calcium Co., Ltd.) were used in all pigments. Several kinds of coating liquids were prepared by changing the blending amount and the average particle diameter. The average particle size was prepared by classification. Using these coating solutions, the re-wet cast coating method is applied to the base paper 10
Several kinds of cast coated papers, which are examples of the present invention or comparative examples thereof, were produced by coating at an operating speed of 0 m / min or 80 m / min. In the Examples and Comparative Examples, the specific amounts of the heavy calcium carbonate and the cubic light calcium carbonate, the operating speed (speed during drum pressure welding), and the average particle size were determined along with the results of the glossiness and the degree of pinhole generation. It shows in Table 1.

[0027]

[Table 1]

(Evaluation) Regarding the evaluation in the table,
It is as follows. [Glossiness] JIS P 8142
In accordance with the above, use a gloss meter manufactured by Murakami Color Research Laboratory to measure 75
° Gloss was measured. The evaluations in Table 1 are as follows. ⊚: The glossiness is 91% or more, and the gloss feeling is superior to that of conventional general cast coated paper. ◯: Glossiness is 85-9
It is less than 0 and has a glossy feeling similar to general cast coated paper. Δ: The glossiness is 80 to 85%, and the gloss feeling is inferior to that of general cast coated paper. X: The glossiness is less than 80%, and the gloss feeling is extremely inferior to that of general cast coated paper.

[Pinhole resistance suitability] The number of pinholes in a 1 cm square portion randomly selected from the surface of the cast coated paper was visually counted. The evaluations in the table are as follows. ⊚: The number of pinholes per 1 cm square is less than 5, and the number of pinholes is extremely small compared to general cast coated paper. ◯: The number of pinholes per 1 cm square is 5 to 10, which is the same number of pinholes as general cast-coated paper. X: The number of pinholes per 1 cm square is 10 or more, which is larger than that of general cast coated paper.

(Results) Examples 1 to 6 of the present invention
Is produced at a speed of 100 m / min, which is faster than the conventional operation speed, but the glossiness and the occurrence of pinholes are equal to or higher than those of the conventional cast coated paper, while Comparative Example 1 In any of the evaluations, the results of 5 to 5 are inferior to the general cast coated paper. Particularly, in Comparative Example 3, the glossy feeling was inferior to that of the general cast coated paper even though the operating speed was 80 m / min, which was the same as the conventional operating speed.

[0031]

As described above in detail, according to the present invention, a cast coated paper excellent in gloss feeling and printability is prepared.
It becomes possible to manufacture in a shorter time than before.

[Brief description of drawings]

FIG. 1 is a schematic view showing a method for producing cast coated paper by a rewet cast coating method according to the present invention.

[Explanation of symbols]

1 ... Base paper, 2 ... Air knife coater, 3 ... Dryer, 4
... injection nozzle, 5 ... mirror surface drum, 6 ... cast coated paper, C ... coating liquid, W ... rewetting liquid.

Continued front page    F-term (reference) 4L055 AG11 AG12 AG94 AH02 AJ04                       BE08 EA15 EA16 EA26 EA32                       FA11 FA12 FA15 GA20

Claims (3)

[Claims] 1. A base paper is coated with a coating liquid containing a pigment and dried to form a coating layer, and the coating layer is wetted with a rewetting liquid and brought into pressure contact with a heated mirror surface drum. A method for producing cast coated paper, which is subjected to surface gloss treatment, wherein 5 to 20% by weight of heavy calcium carbonate and cubic light calcium carbonate having an average particle diameter of 0.1 to 1.0 μm are contained in all pigments. A method for producing cast-coated paper, comprising: -25% by weight. 2. The wet coating layer is 100 m /
The method for producing cast-coated paper according to claim 1, wherein the surface gloss treatment is performed by bringing the surface of the mirror drum into pressure contact at a speed of not less than a minute. 3. A base paper is coated with a coating liquid containing a pigment and dried to form a coating layer. The coating layer is wetted with a rewetting liquid, and is pressed against a heated mirror surface drum. It is a cast-coated paper obtained by surface gloss treatment with 5 to 20% by weight of heavy calcium carbonate and cubic light calcium carbonate with an average particle diameter of 0.1 to 1.0 μm in all pigments. A cast coated paper, characterized by containing 5 to 25% by weight.