JPH0415316B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing cast coated paper, and particularly to an improvement in the rewet casting method in which the coated surface is brought into pressure contact with a cast drum for a mirror finish. [Prior Art] A cast coating method has been known as a method for producing coated paper with strong gloss for printing, that is, cast coated paper. The cast coating method is a wet coating method in which a wet coating layer mainly composed of mineral pigments and adhesive is bonded to a chrome plating drum with a mirror surface under pressure, and after drying, it is peeled off to transfer the chrome plating mirror surface. The rewet casting method involves once drying the coating layer, and then pressing the plasticized coating layer by rewetting it onto the surface of a cast drum that has a mirror surface and peeling it off after drying.The wet coating layer is made into a gel state and has a mirror surface. A gel cast method in which the material is pressed against the drum surface is known. All of these methods have in common that the coating layer in a plastic state is pressed against the surface of a cast drum having a mirror surface using a press roll, dried, and released from the mold to obtain a mirror finish. However, in the wet casting method, if the temperature of the cast drum surface exceeds 100°C, the coating liquid will boil and the coating layer will be destroyed. Therefore, it is not possible to raise the temperature above 100°C. They are forced to operate. In the gel cast method, the coating layer is in a gel state, so the temperature of the cast drum surface is set to 100℃.
Although it is possible to increase the amount of water above the coating layer, it is necessary to transfer a large amount of water contained in the coating layer into the base paper layer in the nip formed by the cast drum surface and press roll, and the gel in the coating layer must be transferred to the base paper layer. In reality, high-speed finishing is not done very often because it is difficult to control the degree of oxidation. In the rewet cast method, the coating layer is once dried, so the temperature of the cast drum surface is set to 90 to 180.
Although it is possible to raise the temperature to .degree. C., the degree of plasticization is significantly lower than that in the wet cast method or gel cast method because the once dried coating layer is re-wetted. Therefore, when operating at low speeds, a coated paper with a relatively uniform high gloss can be obtained, but as the operating speed increases, the uniformity of the gloss is rapidly lost. This phenomenon occurs as pinhole-like spots and uneven gloss, and is thought to occur because the coating layer is not uniformly adhered to the surface of the cast drum due to insufficient plasticization. From the above, in any of the above cast finishing methods, spots due to uneven adhesion on the surface of the coating layer,
There are still problems in producing high quality cast coated papers at high speeds without the occurrence of uneven gloss. [Problems to be Solved by the Invention] Therefore, the present inventors have intensively studied the problems of producing high-quality cast-coated paper at high speed, and have developed the following methods among the three cast-finishing methods described above.
We focused on the rewetting cast method, which is considered to have the highest possibility of high-speed production due to its properties, and made improvements in particular regarding the rewetting liquid. The present invention aims to improve the quality of cast-coated paper in the production of cast-coated paper, in which a dried coating layer containing pigments and adhesives as main components is re-wetted and pressed against a heated mirror surface for a strong gloss finish. The purpose of this is to improve long-term continuous operation and enable high-speed production without deterioration. [Means for Solving the Problems] The present inventors have conducted extensive research on rewetting liquids in particular, and have found that the above object can be achieved by selectively using a rewetting liquid having a specific composition. As a result, the present invention was completed. That is, the present invention provides a method for producing cast-coated paper in which the re-wetted coated surface is brought into pressure contact with a cast drum to achieve a mirror finish, and includes the steps of: containing at least one compound represented by the following chemical formula in the re-wetting liquid; This is a unique method for producing cast coated paper. In the formula, R: C ₈ to _{C 18} saturated or unsaturated aliphatic hydrocarbon group n: An integer of 4 to 10 m: An integer of 1 to 3 In addition, the present invention is characterized in that the re-wetted coating surface is pressed against a mirror drum. The method for producing cast-coated paper, which is finished to a mirror finish, is characterized by containing at least one compound represented by the following chemical formula in the rewetting liquid. In the formula, R: _C8 to _C18 saturated or unsaturated aliphatic hydrocarbon group n: An integer of 4 to 10 m: An integer of 1 to 3 In addition, as the rewetting liquid for the conventional rewet casting method, water or Water containing a surfactant is generally used. In addition, aqueous solutions or emulsions containing polyethylene emulsion, aliphatic soap, calcium formate, calcium stearate, specific surfactants such as potassium oleate, mold release agents such as funnel oil, microcrystalline wax, and higher alcohols. is also known. Previous proposals include, for example,
No. 32767 discloses a processing agent containing an alkylphenyl sulfoamide carboxylic acid derivative represented by the general formula A-SO ₂ NHR-COOH, and proposes a specific surfactant. Also, JP-A-59-192797
There is a proposal that the rewetting liquid contains an amide compound such as urea, dicyandiamide, or formic acid amide, and Japanese Patent Application Laid-open No. 194295/1989 proposes that the rewetting liquid contains a fat having 6 to 22 carbon atoms. There have been proposals to contain a mold release agent consisting of at least one amine salt of a phosphoric acid ester having a group hydrocarbon group, specifically monostearyl phosphate triethanolamine, dioctyl phosphate monoethanolamine, and trilauryl phosphate. Phosphate ester triethylamine and lecithin are listed. Another known rewetting fluid is the use of ammonia to promote plasticization for hydrophilic adhesives such as casein. Although these rewetting liquids promote plasticization in a short period of time and produce homogeneous and highly glossy cast-coated paper, they also remove the release agent (thin film of fatty acids such as stearic acid) that adheres to the cast drum surface. ) and has the disadvantage that it cannot be operated for a long time. In contrast, the compound of the present invention has a faster plasticizing time for the coating layer than ammonia, etc., and also acts without dissolving the thin film of the release agent attached to the surface of the cast drum. , it is possible to produce homogeneous, uniform, and highly glossy cast-coated paper at high speed. The mechanism of action of the compound used in the present invention is not clear why it is effective, but the aqueous solution of the compound of the present invention has a penetrating effect, which allows it to penetrate into the coated layer to promote plasticization, and has a surfactant effect. This is thought to be due to the fact that the coating layer concentrates on the surface of the coating layer and becomes easier to peel off when it is peeled off from the mirror-surfaced drum. When the compound of the present invention is used as a rewetting solution, the solution concentration is 0.01 to 5% by weight, preferably 0.1%.
A range of 1% by weight is effective. The reason is
If it is less than 0.01% by weight, the plasticizing effect will be small;
This is because if it exceeds the weight percentage, the plasticizing effect is undesirable because it has a negative effect on printability, such as deterioration of the surface properties of finished cast-coated paper and poor ink transferability. Specific examples of compounds to be contained in the rewetting solution of the present invention are as follows. Examples of pigments include clay, kaolin, aluminum hydroxide, calcium carbonate, titanium oxide,
One or more of the usual pigments for coated paper, such as barium sulfate, zinc oxide, satin white, and plastic pigments, can be used. In addition, examples of adhesives include proteins such as casein and soybean protein, starches and their derivatives such as cationized starch, oxidized starch, and phosphate starch, carboxymethyl cellulose,
Cellulose derivatives such as hydroxyethyl cellulose, natural water-soluble polymers such as sodium alginate, PVA, olefin-maleic anhydride resin,
Synthetic resin adhesives such as melamine resin, synthetic water-soluble polymer substances such as polyacrylamide, sodium polyacrylate and their copolymers, conjugation of styrene-butadiene copolymers, methyl methacrylate-butadiene copolymers, etc. Acrylic polymer latex such as diene polymer latex, polymer or copolymer of acrylic acid ester and/or methacrylic acid ester, ethylene/vinyl acetate copolymer latex, or these various polymers containing functional groups such as carboxyl groups. Ordinary adhesives for coated paper, such as alkali-soluble or alkali-insoluble polymer latex modified with monomers and functional groups, may be used alone or in combination of two or more. The amount of adhesive used is generally 100 parts by weight of pigment.
It is adjusted within a range of about 5 to 50 parts by weight, more preferably about 10 to 30 parts by weight. In addition, the coating composition may contain release agents, antifoaming agents, and colorants used in conventional coating paper compositions such as wax, microcrystalline wax, carnauba wax, and metal soap. Various auxiliary agents such as additives and flow modifiers are appropriately blended. The coating composition of the present invention can be applied to coaters such as blade coaters, air knife coaters, roll coaters, brush coaters, curtain coaters, chain coaters, bar coaters, gravure coaters, size press coaters, etc. used in the production of coated paper. The base paper is coated in one layer or in multiple layers by an on-machine or off-machine coater equipped with a coating device. The solid content concentration of the coating composition is generally 40 to 70% by weight, but preferably 45 to 65% by weight in consideration of operability. As the base paper, a general paper with a weightage of about 30 to 450 g/m ² used for general printing coated paper or cast coated paper, paper base paperboard, or board base paper is used. The coating amount of the coating composition on the base paper is generally about 10 to 50 ^gm2 in dry weight, but if the coating amount is small, the thickness of the coating layer plasticized by the mirror roll will be small. Adhesion to the mirror roll becomes poor, making it impossible to obtain a sufficient mirror surface. Also, if the amount of coating is larger than necessary, the mirror effect will be saturated,
In addition, since there is a possibility that the coating layer may crack, etc., it is preferable to adjust the coating amount within a range of about 15 to 35 g/m ² . Drying of the coating composition is carried out using a drying device for coated paper such as a hot air dryer, an air foil dryer, an air cap dryer, a cylinder dryer, an infrared dryer, or the like. The degree of drying of coated paper varies depending on the type of base paper, the type of coating composition, etc., but generally the paper moisture is in the range of about 1 to 10%, and it is possible to dry the coated paper to a range of about 3 to 8%. is desirable. The coated paper after drying can be subjected to a calendering process such as a machine calendering process if necessary, but of course it is necessary to avoid calendering processes that significantly impair the bulk and hardness characteristic of cast coated paper. [Example] The present invention will be described in more detail with reference to Examples below, but the present invention is of course not limited to these. In addition, unless otherwise specified, parts and percentages in examples are as follows.
Parts by weight and weight % are shown, respectively. Example 1 95 parts of kaolin, 5 parts of Sachin White, and 0.5 parts of sodium polyacrylate were dispersed in water using a Coles disperser to prepare a pigment slurry with a solid content of 60%. A 16% aqueous solution of casein dissolved in this, using 0.5 parts of an antifoaming agent, 0.5 parts of calcium stearate as a mold release agent, and ammonia as an adhesive 15
1 part (solid content) and 9 parts (solid content) of styrene-butadiene latex (manufactured by Asahi Kasei Industries, "Product name DL-636") and 9 parts (solid content) to prepare a coating liquid with a solid content concentration of 40%. did. Using the coating liquid thus obtained, rewet casting was performed using the apparatus shown in the figure. That is, the above-mentioned coating liquid was coated on a paperboard base paper 1 with a 230 g/m ² basis weight using an air knife coater 2 so that the dry weight was 25 g/m ² , and the paper moisture was reduced to 6% using a hot air dryer 3. Dry as it should. Then diameter 750mm
Urethane rubber coated press roll 4 and diameter 1220
The paper is passed through a press nip 6 formed by a chromium-plated cast drum 5 of mm, and there the compound of formula (5) (manufactured by Toho Chemical Industry Co., Ltd.
The surface of the coating layer was re-wetted with a re-wetting solution consisting of 0.5 parts of RB410) and 99.5 parts of water, and then cast at a press nip pressure of 100 kg/cm, a drum surface temperature of 110°C, and a rotational speed of 65 m/min. After being pressed against the drum 5 and dried, it was peeled off from the cast drum 5 with a take-off roll 6 to obtain a cast coated paper 9. Example 2 Cast-coated paper was prepared in the same manner as in Example 1, except that a re-wetting liquid containing the compound of formula (3) (RE610 manufactured by Toho Chemical Industry Co., Ltd.) was used as the re-wetting liquid. I got it. Comparative Example 1 Cast coated paper was obtained in exactly the same manner as in Example 1, except that an aqueous solution containing 0.5 parts of potassium oleate dissolved in 99.5 parts of water was used as the rewetting liquid. Comparative Example 2 Cast-coated paper was obtained in exactly the same manner as in Example 1, except that an aqueous solution in which 1 part of calcium formate was dissolved in 99 parts of water was used as the rewetting liquid. The following table shows the results of evaluation and measurement of the continuous operability, adhesion unevenness, and gloss of the cast coated papers obtained in the above Examples and Comparative Examples.

[Table] Looking at the table showing the results of Examples and Comparative Examples, it can be seen that the cast coated paper obtained in the Examples of the present invention was better than that obtained in the Comparative Examples using conventional surfactants and mold release agents. It is clear that this paper is superior to cast-coated paper in terms of continuous operation, uneven adhesion, and white paper gloss. [Effects of the Invention] The method for producing cast-coated paper of the present invention can extremely effectively improve the problem of continuous operation due to the use of rewetting liquid in the conventional rewetting method, and can improve cast coated paper. This enables stable, long-term continuous operation and high-speed production without reducing the quality of coated paper.

[Brief explanation of drawings]

The drawing is a side view showing an outline of a coating device used in the method for manufacturing cast coated paper of the present invention. 1...Base paper, 2...Air knife coater, 3...
... Hot air dryer, 4 ... Press roll, 5 ... Cast drum, 6 ... Press nip, 7 ... Nozzle, 8 ... Take-off roll, 9 ... Cast coated paper.

Claims (1)

[Claims] 1. A method for producing cast coated paper in which the rewetted coated surface is brought into pressure contact with a cast drum to give a mirror finish, wherein the rewetting liquid contains at least one compound represented by the following chemical formula: A method for producing cast coated paper, characterized by: In the formula, R: _C8 to _C18 saturated or unsaturated aliphatic hydrocarbon group n: An integer of 4 to 10 m: An integer of 1 to 3 2 The re-wetted coating surface is brought into pressure contact with a cast drum to achieve a mirror finish. A method for producing cast-coated paper, characterized in that the rewetting liquid contains at least one compound represented by the following chemical formula. In the formula, R: _C8 to _C18 saturated or unsaturated aliphatic hydrocarbon group n: An integer of 4 to 10 m: An integer of 1 to 3