JPS61245398A - Production of cast coating paper - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing cast coated paper, and in particular, to effectively improve drum picks that occur at both ends of coated paper during high-temperature casting. It concerns a method for efficiently producing high quality cast coated paper.

``Prior art'' The method for producing highly glossy coated paper called cast coated paper is to press a wet coating layer mainly composed of mineral pigments and adhesives onto a heat-finished surface with a mirror surface to achieve a glossy finish. Wet casting method, after drying the wet coating layer,
Known methods include a rewet casting method in which the wet coated layer is plasticized by rewetting and pressed against a heated finished surface having a mirror surface, and a gel casting method in which the wet coating layer is made into a gel state and pressed against a heated finished surface having a mirror surface.

All of these methods have in common that the coating layer, which is plasticized by water, is pressed against a heated, mirror-finished surface using a press roll, dried, and released from the mold to give it a strong glossy finish. However, the rewet casting method and gelling casting method
Because the coating layer is once dried or gelled before it is pressed against the mirror-surfaced drum, even if it is pressed against a drum at a temperature of 90°C or higher under high pressure, a large amount of moisture will not evaporate rapidly like in the wet casting method. The cast coated paper can be finished at high speed with sufficient adhesion to the drum surface without causing damage to the coated layer or paper breakage.

However, these high-temperature, high-pressure cast and cast methods tend to cause a defect called drum pick, in which a part of the coating layer peels off and adheres to the drum surface, especially at both edges of cast coated paper. There is a strong tendency.

Streaks may also occur in the center, which is a major problem that impairs the quality of cast coated paper and also impairs stable operation. This tendency for drum picks to occur becomes stronger as the speed or drum temperature increases, so even in high-temperature, high-pressure casting methods, it is desirable to operate at a higher drum temperature in order to maintain other cast quality. This may be a fatal flaw in the Ruri wet casting method.

``Problems to be Solved by the Invention'' The purpose of the present invention is to effectively eliminate drum picks that occur especially in high-temperature casting methods, and to efficiently produce cast-coated paper with uniform high quality over the entire width direction. The purpose is to provide a method that can be manufactured well.

"Means for Solving the Problem" In view of the current situation as described above, the present inventors have conducted extensive research based on their many years of experience in manufacturing cast coated paper, particularly regarding the improvement of drum picks that occur during high-temperature casting. It was concluded that one of the main causes of drum pink occurring at both ends of cast coated paper is the non-uniformity of the temperature profile of the cast drum.

In other words, the drum temperature in the outer part from both edges of the cast coated paper is higher than that in the center because the drum temperature is not affected by the cooling effect that accompanies the drying of the coating layer. It is presumed that when the material is pressed against the cast drum, the water rapidly expands due to the rise in temperature, causing intralayer separation and being peeled off on the surface of the cast drum, forming a drum pick.

Mata, the streaky drum pick that occurs in the center of the drum,
It is presumed that drying becomes uneven due to the unevenness of the coating amount of the wet coating layer, resulting in the same condition as when the drum temperature is uneven, and drum pick occurs.

Based on this estimation, the present inventors conducted further studies to develop a method that could make the temperature profile of the cast drum more uniform and effectively eliminate the occurrence of drum picks. This paper found that the occurrence of drum pink can be extremely effectively suppressed by applying water to the back side of the coated paper, which corresponds to the area where drum picks are observed, at or before the press nip area where the press nip contacts the surface. The invention was completed.

That is, the present invention is a cast-coated paper in which a coating layer mainly composed of pigments and adhesives is gelled or dried and then re-wetted, and then pressed against a heated drum surface having a mirror surface to achieve a strong gloss finish. In the manufacturing method, the cast coating is characterized in that water is applied to the back surface of the coated paper corresponding to the portion where drum picks are observed to occur at or before the press nip portion where the coating layer is pressed against the drum surface. This is a method of manufacturing a paper cover. .

"Function" In the method of the present invention, the coating composition used to form the coating layer is a composition containing pigments and adhesives as main components, similar to conventional cast coated paper compositions. is used.

Examples of pigments include clay, kaolin, aluminum hydroxide, calcium carbonate, titanium oxide, barium sulfate,
One or more of the usual coated paper pigments such as zinc oxide, satin white, plastic pigments, etc. are used.

Adhesives include proteins such as casein, soy protein, and synthetic proteins, conjugated diene polymer latex such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, and acrylic ester and/or methacrylic ester. Acrylic polymer latex such as polymer or copolymer, vinyl polymer latex such as ethylene/vinyl acetate copolymer, or various polymers thereof are functionally modified with a monomer containing a functional group such as a carboxyl group. alkali-soluble or alkali-insoluble polymer latex, polyvinyl alcohol, olefin/maleic anhydride resin, synthetic resin adhesives such as melamine resin, starches such as positive starch and oxidized starch, carboxymethyl cellulose,
Cellulose derivatives such as hydroxyethylcellulose, etc.
One or more of the conventional coated paper adhesives may be used. The ratio of adhesive used is generally 5 to 5 parts by weight per 100 parts by weight of pigment.
It is adjusted within a range of about 0 parts by weight, more preferably about 10 to 30 parts by weight.

In addition, various auxiliary agents such as an antifoaming agent, a coloring agent, a mold release agent, and a flow modifier are suitably blended into the coating composition as required.

The coating composition thus prepared can be coated using a blade coater, an air knife coater, or an air knife coater commonly used for producing coated paper.
Roll coater, brush coater, curtain coater,
The base paper is coated in one layer or in multiple layers using an on-machine or off-machine coater equipped with a coating device such as a chamber coater, bar coater, gravure coater, or size press coater. The solid content concentration of the coating composition at that time is generally 40 to 70% by weight,
In consideration of operability, the content is preferably in the range of 45 to 65% by weight.

As the base paper, a paper-based or board-based base paper with a weight of about 30 to 400 g/-, which is used for general printing coated paper or cast coated paper, is used. These are made by acid paper making or alkaline paper making, but of course neutral base paper containing about 10% by weight or more of high-yield valves can also be used. Further, pre-coated paper or coated paper with a general pigment coating on the back side of the cast coating layer can also be used as the base paper.

The coating amount of the coating composition on the base paper is generally 10% by dry weight.
~50 g/rrl, but it is 15% in terms of improving the quality of the resulting cast coated paper and the cast coating speed.
It is preferable to adjust it within a range of about 35 g/cd.

The coating layer thus formed on the base paper is gelled by acid, salt, heat, etc., as in the conventional method, and is further re-wetted as necessary, or once dried (including a semi-dry state). It is then re-wetted and pressed against a heated mirrored drum surface.

As a rewetting liquid, water or a polyethylene emulsion,
An aqueous solution, emulsion, or the like containing about 0.01 to 3% by weight of a release agent such as fatty acid-based carbon, calcium stearate, microcrystalline wax, surfactant, and funnel oil is preferably used.

In the method of the present invention, as described above, water is applied to the back surface of the coated paper corresponding to the area where drum shock is observed during casting finishing, at or before the press nip where the wet coating layer is pressed against the drum surface. It has an extremely important feature in its action.

Conventionally, a method has been proposed in which water is applied uniformly to the entire back surface of the coated paper in order to adjust the curl of the finished cast coated paper. In this method, water is applied intensively to the back surface of the coated paper, which corresponds to the area to be coated. Therefore, the desired effects of the present invention cannot be expected simply by increasing the amount of water applied to the entire back surface.

Incidentally, in order to reduce the occurrence of drum picks without applying special water to areas where drum picks occur, it is necessary to apply an excessive amount of water to the entire back side of the coated paper. Even if the occurrence of picks is improved, there are accompanying defects such as a significant decrease in casting speed, an increased tendency for paper breakage to occur, and worsening of curling, making stable operation impossible.

The method of applying water to the back side of the coated paper is to spray water on the press roll corresponding to the area where drum pink is observed and transfer it to the back side of the coated paper at the nip part, or to apply water to the back side of the coated paper. Methods include, but are not limited to, methods such as directly spraying water on the back surface of the coated paper immediately before entering the nip, or using a water coating roll or the like to apply water. Moreover, these methods can also be used in combination.

Confirmation of the location where a drum pick occurs can be done by visual judgment by the worker, but a defect detection device such as a spot detector is installed on the cast drum, etc. to confirm the location where a drum pick has occurred and take appropriate measures to address that area. A water supply device can also be linked. According to such a method, the occurrence of drum picks is automatically eliminated and extremely efficient operation becomes possible.

The water supplied to the back side of the coated paper contains starch, proteins, waxes, sizing agents, synthetic resins,
Dyes, surfactants, pigments, etc. may be added, and the same aqueous solution as the rewetting solution for the coated layer may be used. Further, the amount of water supplied is appropriately adjusted depending on the drum temperature, paper weight, casting speed, etc.

In the present invention, water is applied intensively to the back surface of the coated paper, which corresponds to the area where drum picks are particularly observed, but water is applied to the entire back surface of the coated paper, which is conventionally done to prevent curling. It is also possible to use water treatment in combination. However, the amount of water to be treated is desirably adjusted appropriately depending on the drum temperature, paper weight, casting speed, etc., so as not to cause a significant decrease in casting speed or paper breakage.

To briefly explain the heating drum used in the present invention, its diameter is generally about 1,000 to 5,000 mm, but a drum with a diameter of about 1,200 to 3,600 mm is preferable from the viewpoint of operation, and the drum surface temperature is generally 90°C.
It is used in the above, but considering low quality, operability, etc.
The temperature is preferably in the range of 00 to 160°C, and the press roll for pressing the coated paper onto the drum has a roll diameter of 200 to 150 Qmm, more preferably 300 to 90°C.
It is desirable to use a rubber-coated roll of about 0■■, and the press roll pressure when pressing the coated paper is about 30 to 350 kg /
cs, more preferably about 80 to 25 Qkg/cs+.

Furthermore, in order to control and humidify the cast coated paper after finishing, we have installed a water coating device using a roll, an electrostatic humidifier, a steam humidifier, etc., and various types of equipment that are conventionally known in the field of coated paper manufacturing. It is of course possible to use appropriate combinations of techniques.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these.

Further, unless otherwise specified, parts and % in the examples indicate parts by weight and % by weight, respectively.

Examples 1 to 3, Comparative Examples 1 to 3 70 parts of kaolin, 30 parts of light calcium carbonate, and 0.5 parts of sodium polyacrylate were dispersed in water using a Coles disperser to make a pigment slurry with a solid content concentration of 60%. was prepared.

To this was added 0.5 parts of tributyl phosphate as an antifoaming agent, 1.0 part of ammonium stearate as a mold release agent, 8 parts of an aqueous casein solution (concentration 18%) dissolved in ammonia as an adhesive, and acrylic acid/butadiene. Add 18 parts (solid content) of methyl methacrylate (2.33.65%) copolymer latex, and then add zinc sulfate aqueous solution (
After adding 3 parts of 15%) and stirring thoroughly, the pH was adjusted to 9.0 using aqueous ammonia to prepare a coating liquid with a solid content concentration of 46%.

Using the coating liquid thus obtained, a rewetting process was carried out using an apparatus as shown in FIG.

That is, a base paper (1) of 100 g/cd was coated with the above coating liquid using an air knife coater (2) so that the dry coating amount was 22 g/rd, and then dried using an air foil dryer (3).
The paper was dried to a moisture content of 6%.

The paper is then passed through a press nip (6) formed by a rubber-coated press roll (4) with a diameter of 750 g*m and a chrome-plated cast drum (5) with a diameter of 1220 m.
0 of calcium stearate supplied from the nozzle (η
．． The coated layer was rewetted with a rewetting solution consisting of a 5% aqueous solution and pressed onto a cast drum (5) heated to 125° C. under a press nip pressure of 150 kg/am. After drying, it was peeled off from the drum using a take-off roll (8) and wound up as a cast coated paper (9).

In Example 1, before the coated paper enters the press nip (6), water is edge-showered by spraying (a) on both edges of the back side of the coated paper, and in Example 2, the coating of the press roll (4) is Water was sprayed onto the areas corresponding to both ears of the paper using a sprayer. Further, in Example 3, water was applied to both edges of the back surface of the coated paper using a combination of spray (a) and spray crest).

In Comparative Example 1, no water was applied to the back surface of the coated paper, and in Comparative Example 2, water was applied to the entire back surface of the coated paper by spraying (C) in the press nip (6). In Comparative Example 3, after the coated paper passed through the press nip (6), water was edge-showered by spraying (dl) on both sides of the back side of the coated paper. Table 1 shows the occurrence of drum picks in the department.

Table 1 (Note) Drum picks are shown by the number of drum picks generated at both ends of the obtained cast coated paper (width 203 m, length 10 m).

As is clear from the results in Table 1, the method of each example of the present invention does not produce drum picks at both edges of the cast-coated paper, and is capable of producing high speed It was possible to stably obtain high quality cast coated paper.The cast surface gloss of the cast coated papers obtained was 90 parts 2% (JISP-8142 method) in all cases.

Example 4, Comparative Example 4 75 parts of kaolin, 5 parts of aluminum hydroxide, particle size 2μ
20 parts (solid content) of a heavy calcium carbonate dispersion having the following particle content of 95% was used as a dispersant: 0.5 part (solid content) of sodium polyacrylate, 0.5 part of sodium birophosphate.
A pigment slurry with a concentration of 70% was prepared using 5 parts of the pigment slurry.

To this, 13 parts of a 20% concentration casein aqueous solution and 17 parts (solid content) of styrene-butadiene copolymer latex were added and mixed as an adhesive, and 0% ammonium oleate was added.
．． 5 parts were added to obtain a 53% coating solution. The viscosity of the coating liquid is 1500 cps (Brookfield viscometer,
(60 rpm, 20°C) and the pH was 9.0.

Using this coating liquid, gel casting was performed using an apparatus as shown in FIG. That is, base paper αυ of 90 g/cd
The above coating liquid was coated on the roll coater side so that the dry weight was 25 g/rd, and 0.5% formic acid aqueous solution (25 g/rd) was applied.
) to gel the coating layer. Diameter 800IllI
The paper is passed through a press nip (II) formed by a press roll αO of 100
kg/am, and after drying take-off roll (1
1 and rolled up as a cast coated paper.

Immediately before the press nip αe, water was sprayed onto both sides of the coated back surface using spray (e). The cast-coated paper obtained had almost no drum picks at both edges and no variation in gloss in the width direction. Comparative example 4
In this case, when water was not sprayed using the above-mentioned spray (el), a large number of drum picks occurred on both sides of the cast coated paper.

"Effects" According to the method of the present invention, drum picks that occur at both edges of coated paper during high-temperature casting are extremely efficiently eliminated, and high-quality cast coated paper can be produced stably at high speed. It is something.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are schematic cross-sectional views of cast finishing equipment used in Examples and Comparative Examples of the present invention.

Claims (2)

[Claims] (1) A method for manufacturing cast-coated paper, in which a coating layer containing pigment and adhesive as main components is gelled or dried, then re-wetted, and then pressed against a heated drum surface with a mirror surface to give it a high-gloss finish. Cast coated paper, characterized in that water is applied to the back side of the coated paper corresponding to the area where drum picks are observed at or before the press nip where the coating layer is pressed against the drum surface. manufacturing method. (2) The manufacturing method according to claim (1), wherein the temperature of the drum surface having a mirror surface is 90° C. or higher.