JP3279648B2 - Manufacturing method of cast 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 finishing a cast coated paper, and more particularly to a method for finishing a double-sided cast coated paper having excellent white gloss and surface properties without loss of bulkiness and rigidity and having no difference between front and back. Things.

[0002]

2. Description of the Related Art A high gloss coated paper for printing, which is called a cast coated paper, is provided with a water-based pigment coating mainly composed of a pigment and an adhesive on a surface of a base paper to form a cast coated layer. It is manufactured by pressing and drying a cast coating layer on a heated metal mirror drum.

[0003] As a method of manufacturing this cast coated paper,
Wet cast method in which the wet coating layer is pressed against the heating drum surface to give a gloss finish, gelling casting method in which the wet coating layer is brought into the gel state and pressed against the heating drum surface to give a gloss finish, wet state Is known, such as a method of drying a coating layer once, plasticizing it by rewetting, and pressing it against the surface of a heating drum.

[0004] These casting methods are common in that a coating layer in a plastic state is pressed against a heating drum surface and dried to release the coating layer.

[0005] Most of the cast coated papers produced according to the above-mentioned production method are single-sided casts, and high-quality paper is used on the back surface.

[0006] Cast coated paper has high gloss, smoothness and bulkiness, and the printed matter is characterized by exhibiting a unique beautiful finish. Therefore, there has been a demand for a double-sided cast coated paper that has been mirror-finished on both sides.

In order to manufacture a double-sided cast coated paper, firstly, one side of a base paper is coated with a coating liquid containing a pigment and an adhesive as a main component, and is pressed and dried on a heating drum having a mirror surface to finish gloss. This is wound up once, or continuously coated again with the same coating liquid as above on the opposite surface, pressed against a heating drum and dried to obtain a glossy finish on both sides.

However, when a double-sided cast coated paper is produced by this method, a problem different from that of a single-sided cast coated paper occurs.

That is, in terms of quality, the moisture in the paint on the side to be cast later is suddenly turned into steam in the heating and drying process, and the surface of the base paper layer and the previously cast-finished mirror glossy coated layer are formed. , And evaporates, and the smoothness and gloss of the precast surface formed by the heat and moisture at that time are extremely reduced. For this reason, the difference between the front and back sides is remarkable in blank paper quality, and it is not possible to obtain a good cast paper having no front and back differences.

In order to improve such a problem in the double-sided cast paper, there has been proposed a method of finishing by calendering with, for example, a super calender or a soft calender. However, these methods, on the other hand, detract from the advantages of low density, bulkiness and high rigidity, which are characteristics of cast coated paper.

[0011]

DISCLOSURE OF THE INVENTION The present invention relates to a cast-coated paper which has excellent low-density, high-bulk, and high-rigidity characteristics of cast coated paper without deteriorating the quality and operability of the coated layer surface. It is intended to provide a method for efficiently finishing a double-sided cast paper having no difference.

[0012]

In view of this situation, the present inventors have proposed a method for finishing a double-sided cast coated paper containing a pigment and an adhesive as a main component, by humidification by heating steam, heating and soft calendering. We have found a way to introduce technology. That is, after the coating layer surface after the casting process is humidified and heated by applying a slight heating steam at a low pressure to 100 ° C.
By performing the soft calendering process as described above, it is possible to improve the gloss and gloss uniformity without impairing the bulk and rigidity of the cast coated paper as in the conventional super calendering process or simple soft calendering process, and there is no difference between front and back. It is intended to obtain a surface.

In the heating steam treatment, it is sufficient that the steam is ejected at a fixed angle from a nozzle which is parallel and opposed to the paper to the paper surface, and the steam adheres to the paper surface to appropriately raise and adjust the temperature and moisture of the paper. For example, Japanese Patent Application Nos. 3-356324 and 16907.
8, 166175 can be used. At this time, the heating steam is operated at a pressure of 1 kg / cm ² or less and a steam flow rate of 15 to 80 kg / Hr / m.

In order to carry out the present invention, it is desirable to use a soft calender method having a special resin roll excellent in heat resistance and pressure resistance.

The temperature of the soft calendering treatment is not lower than 100 ° C. If it is lower than 100 ° C., satisfactory surface properties cannot be obtained without impairing bulkiness and rigidity. Further, the temperature is preferably 200 ° C. or less from the viewpoint of the durability of the roll.

By improving the surface properties after casting by calendering under the above conditions, the reduced smoothness and luster of the first cast surface can be improved without significantly impairing the bulkiness and rigidity. Quality can be improved to the same level as gloss.

The method for producing a cast coated paper used in the finishing method of the present invention is not particularly limited, such as a wet casting method, a rewetting casting method, a gelling casting method, and the like. It is not necessary to employ any method such as wet-casting on one side and re-wet-casting on the other side.

As the special resin of the soft calender used in the present invention, urethane resin, polyether resin, ebonite rubber or the like is used, and the surface strength is 60 Shore D hardness.
~ 93 are preferred.

As the coating composition used for forming the coating layer in the method of the present invention, a composition mainly composed of a pigment and an adhesive is used similarly to a conventional composition for cast coated paper.

As the coating pigment, clay, calcium carbonate, satin white, aluminum hydroxide, barium sulfate, etc. may be used alone or in combination of two or more. As the adhesive, latex such as casein, soybean protein, conjugated cyanenes such as styrene / butadiene, acrylics such as acrylates, vinyl-based polymers such as ethylene / vinyl acetate, etc. is 5 to 30 parts by weight based on 100 parts by weight of the pigment. It is used in combination with other parts.

In addition, if necessary, a release agent, an antifoaming agent, and a release agent used in a conventional coating liquid composition for cast coating may be used.
Dispersants and the like can also be used.

The coating composition thus prepared can be used for coating such as a blade coater, an air knife coater, a roll coater, a brush coater, a curtain coater, a bar coater, a gravure coater, a size press coater and the like, which are used in the production of general coated paper. The base paper is coated in one or more layers by an on-machine or off-machine coater provided with a device to be coated. The solid content of the coating composition at that time is generally 40 to 65% by weight, but preferably 45 to 60% by weight in consideration of operability.

As the base paper, a basis weight of 30 to 400 g / m ² used for general printing coated paper or cast coated paper is used.
Paper-based or board-based base paper is used. These are base papers made by acidic or neutral papermaking. Of course, medium base papers containing about 10% by weight or more of high yield pulp can also be used. Also, coated paper in which a general pigment coating layer is provided on the back side of the pre-coating or cast coating layer can be used as the base paper.

The coating composition for the base paper is 1% by dry weight.
Although it is coated at about 0 to 35 g / m ^2, from the viewpoint of the quality of the obtained cast coated paper and the effect of improving the cast coating speed,
Most preferably, it is adjusted in the range of 15 to 25 g / m ² .

[0025]

EXAMPLES Examples of the present invention will be described below, but of course the present invention is not limited to these examples. In addition, parts and% in the examples
Represents parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 100 parts of kaolin, dispersant (sodium polyacrylate)
0.3 parts was dispersed in water using a CORES disperser to prepare a pigment slurry having a solid content of 60%. 0.5 parts of an antifoaming agent (tributyl phosphate), 5 parts of a release agent (ammonium stearate), 10 parts of a casein aqueous solution having a solid concentration of 15% as an adhesive (solid content), and styrene.
15 parts (solid content) of butadiene copolymer latex (SN-307 manufactured by Sumitomo Nogatack Co., Ltd.) were added, and water was further added to prepare a coating liquid having a solid content of 50%. A 5% calcium formate solution containing 0.3% of a release agent (ammonium stearate) was prepared as a gelling solution. Gel casting was performed using the obtained coating liquid. That is, basis weight 70 g /
m ² cast coated base paper with a dry weight of 25
The above coating solution was applied with a roll coater so as to give g / m ^2, and then contacted with a gelling solution to gel the coating layer. Then, it is pressed against a 750 mm diameter rubber-coated press roll and a cast drum having a surface temperature of 90 ° C. and a diameter of 3000 mm, dried, peeled off from the cast drum with a take-off roll to obtain a single-sided cast coated paper, and then the opposite side. The same operation was performed to obtain a double-sided cast coated paper.
Processing was performed at a speed of 50 m / min.

The double-sided cast paper thus obtained is sprayed with steam at a steam pressure of 0.8 kg / cm ² and a steam flow rate of 50 kg / Hr / m, and the surface cast first at a heating temperature of 120 ° C. is made of metal. Soft calender processing was performed so as to be in contact with the roll. The nip linear pressure was set under the condition that the smoothness of the surface (first coated surface) was 4000 to 5000 sec.

Comparative Example 1 A double-sided cast coated paper was surface-finished in the same manner as in Example 1 except that the soft calendering temperature was 80 ° C.

Comparative Example 2 A double-sided cast coated paper was surface-finished in the same manner as in Example 1 except that steam humidification was not performed.

Comparative Example 3 The same as Example 1 except that the surface finishing treatment by the soft calender was not performed.

The quality evaluation results of the cast coated papers obtained in each of the examples and comparative examples are also shown in Table 1 below. Table 1
The white paper gloss, smoothness, stiffness, and visual difference between the front and back sides were determined as follows.

[0032]

[Table 1] Visual front / back difference : White paper was visually observed, and the front / back difference was determined from comprehensive evaluation of surface properties such as gloss and smoothness.

：: There is almost no difference between the front and back of the cast coated surface.

Δ: The difference between the front and back of the cast coated surface is small.

×: The difference between the front and back of the cast coated surface is large.

Blank gloss : 75 ° gloss was measured using a gloss meter manufactured by Murakami Color Research Laboratory.

Smoothness : JAPAN Tappi No.
5 Measured with an Oken-type smoothness tester.

Stiffness: Measured with a Clark stiffness tester according to JIS P8143.

[0039]

As is clear from Table 1, Example 1 has a low density (bulk), a high glossiness, smoothness and rigidity of a white paper, and a small difference between front and back. Comparative Examples 1 to 3 are inferior in density, stiffness, or surface difference between front and back.

Therefore, the double-sided cast coated paper produced by the production method of the present invention has an unprecedented superior quality and its product value is extremely large.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a finishing device used in Examples and Comparative Examples of the present invention. 1: steam humidifier 2: soft calender (1): elastic roll (2): metal roll

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-229293 (JP, A) JP-A-2-26863 (JP, A) JP-A-4-96808 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (1)

(57) [Claims] 1. A method for producing a double-sided cast coated paper having a cast coated layer mainly composed of a pigment and an adhesive on both sides of a base paper, wherein a pressure of 1 kg /
After the steam flow rate in cm ² or less was applied humidified and heated <br/> heating steam 15~80kg / Hr / m width, temperature 100 ° C.
A method for producing a cast coated paper, characterized by performing a soft calender treatment as described above.