JPH06313296A - Production of cast coated paper - Google Patents

Abstract

(57) [Summary] [Purpose] Excellent quality cast coated paper that retains the high gloss and high smoothness characteristic of cast coated paper, and is free from defects such as uneven gloss, mottle, pinholes and drum picks. The present invention provides a manufacturing method capable of increasing the coating speed and the operation efficiency and improving the productivity. [Structure] A cast coating layer containing a pigment and an adhesive as a main component is provided on the base paper, and while the cast coating layer is in a wet plastic state, the cast coating layer is heated, and the cast coating layer and the press roll are provided. A method for producing cast coated paper, which comprises sandwiching an endless strip-shaped elastic body, pressing a cast coating layer through the endless strip-shaped elastic body to dry it, and releasing the die after drying.

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 cast coated paper, and more particularly to a method for producing cast coated paper, which retains the high quality characteristic of cast coated paper and enhances the coating speed and operating efficiency of cast coating. is there.

[0002]

2. Description of the Related Art Wet casting method, re-wet casting method and gelling casting method are three typical methods for producing coated paper called cast coated paper. There is a method of using an endless base material or a winding base material. In the wet casting method, a base paper is coated with a pigment and an adhesive, a wet plastic coating layer is pressed against a cast drum having a heated mirror surface, dried, and then released, and the mirror surface of the drum is coated. Transfer to. Then, in the rewet casting method, the coating layer is once dried and then rewet with a wetting liquid to bring the coating layer into a wet plastic state. Further, in the gelling cast method, the wet coating layer is gelled to form a wet plastic coating layer.

The surface of the cast drum has a highly smooth finished surface, and is usually a mirror-finished drum which is plated with chrome or the like. This cast drum has a diameter of about 1 to 4 m. The heating means is generally steam heating in the drum, and dielectric heating from the outside, infrared heating, and hot air drying are also used.

In any of the above methods, the wet plastic coating layer is pressed against the heated cast drum surface to bring the coating layer into close contact with the drum surface and is dried in a state in which shrinkage is suppressed. It is common for the coating layer to form an accurate replica of the cast surface along the surface shape of the drum, and then to release the mirror surface to copy the mirror surface.

In such a cast coating method,
The close contact between the coating layer and the drum surface is important, and a press roll coated with rubber or synthetic resin is generally used as the means for pressure contact. The press roll is pressed against the surface of the casting drum with a hydraulic cylinder or the like, and the linear pressure at this time is determined according to the requirements of each casting method.

In these methods, since the surface of the coating layer is dried by contact with the surface of the heating drum, all the water in the coating layer passes through the paper layer, passes through to the opposite side, and evaporates to dry. Therefore, cast coated paper is forced to operate at a lower speed than general art paper coated paper, and it is an important technical issue to further increase the coating speed to improve productivity. Has become.

Although evaporative drying requires a drying time for evaporating moisture, since it dries in a state of being in close contact with the cast drum surface, the drying time becomes the contact distance time of the drum surface, and the paper is held around the drum surface circumference. In addition to maximizing the contact ratio between the position, that is, the drum surface and the paper, the drum diameter must be increased to allow the drying time. However, increasing the diameter of the cast drum is technically and economically problematic.

As a means for increasing the coating speed in the cast coating method, reducing the evaporated water content is a fundamental problem. However, in the wet casting method and gelling casting method, the coating suitability such as fluidity of the coating material is also limited, and it is difficult to prepare or coat the coating material with higher concentration. Even with the rewet method, which allows a relatively small amount of water, a large amount of water is still required in order to enable deformation with respect to the press pressure and to bring the coating layer into a wet plastic state so that it adheres to the cast drum surface. I am trying.

The most important factor for reducing the water content in evaporative drying is the coating amount of the cast coating layer, and it is desired to obtain the highest quality with the minimum coating amount. Therefore, many innovations such as base paper, undercoating, smoothing, and coating suitability have been made. However, in order to obtain high quality, a coating amount corresponding to that is still required. Reducing the amount of coating and increasing the coating speed has already reached the limit at present in the case of producing high quality cast coated paper.

Various attempts have been made to accelerate evaporation and drying by raising the heating temperature of the cast drum. However, as described above, in cast coating, if the temperature of the drum surface is the temperature of water evaporation, the water in the wet plastic coating layer will start to evaporate rapidly at the moment of contact with the drum surface. Since the adhesion between the layer and the drum surface is hindered, it is generally necessary to limit the temperature of the drum surface to 100 ° C. or less.

Further, as a method of operating by raising the heating temperature of the cast drum, Japanese Patent Publication No. 39-20352 discloses that the water in the coating layer does not boil rapidly while being in contact with the heating cast drum. As described above, there has been proposed a method of pressurizing a felt that absorbs vapor from the back surface of the paper using a pressure belt. However, in this method, when a relatively high pressing pressure is required as in the rewet casting method, it is difficult to adhere to the casting drum at a uniform high pressure because pressing is performed through the felt, and as a result, the casting is performed. There is a drawback that uneven surface gloss of coated paper occurs. Although it has been reported that the rewet casting method and the gelling casting method can achieve a high temperature of 120 to 130 ° C., in these examples, a sufficiently satisfactory high quality cast coated paper has not been obtained yet.

In the case of the rewet cast method,
Generally, in order to bring the wet coating state of the cast coating layer into close contact with the drum surface to an insufficient degree, means for increasing the press pressure is also an important issue for the purpose of improving quality and coating speed. However, the elastic roll of the press roll coated with rubber or synthetic resin has a limit for high temperature and high pressure. Since the surface of the cast drum is heated, the temperature of the press roll gradually rises during operation, and the elasticity, that is, the hardness, changes with the temperature change. Further, in the case of the coated elastic roll, the peeling trouble between the iron core portion and the coating layer becomes a problem against temperature and pressure.

Further, as a method of lengthening the pressing time to the cast drum by means of widening the nip width, for example, Japanese Patent Laid-Open No. 59-82498 discloses that an endless belt has the same or similar curvature as the cast drum. A method of pressurizing with a pressure shoe has been proposed. However, in this case, it is necessary to use a lubricant between the endless belt and the pressure shoe, and this lubricant may wrap around the surface and mix into the paper or paint. Particularly, in the rewet casting method in which a nip dam is formed in the press section and the rewet rewetting agent is supplied, mixing of the lubricant is a problem.

[0014]

SUMMARY OF THE INVENTION The object of the present invention is to maintain the high quality such as high gloss and high smoothness, which are the characteristics of cast coated paper, and also to prevent uneven gloss, mottle, pinholes,
An object of the present invention is to provide a method for producing an excellent cast-coated paper that does not have the drawbacks of drum picks, by increasing the coating speed and operation efficiency and improving the productivity.

[0015]

DISCLOSURE OF THE INVENTION The present invention provides a cast coating layer containing a pigment and an adhesive as a main component on a base paper, and a cast drum heated while the cast coating layer is in a wet plastic state. A method for producing a cast-coated paper, which comprises pressing an endless elastic member between a cast drum and a press roll to bring the cast-coated paper into a finished state.

[0016]

According to the method for producing cast coated paper of the present invention, for example, the thermoelastic change of the elastic body can be obtained by combining the material, hardness and thickness of the endless belt-shaped elastic body and the material, hardness, roll diameter and number of press rolls. Can be made constant, and the nip line pressure can be increased or the nip width can be increased without causing peeling trouble of the elastic body. Therefore, by sufficiently adhering the cast coating layer and the surface of the cast drum to each other and drying, it becomes possible to form an excellent cast surface of the coating layer. As a result, high quality can be maintained and the coating speed can be increased. In addition, by gently pressurizing and depressurizing the pressure applied, it is possible to prevent the occurrence of defects such as uneven gloss, mottle, pinholes, and drum picks, and to produce high-quality cast coated paper without defects with high productivity. be able to.

Further, there is no defect such as peeling trouble between the iron core portion of the coating roll and the coating layer, and it is possible to endure stable operation at high temperature and high pressure for a long time. By keeping the temperature constant, at the same time, the temperature of the press roll is also kept constant, and the operating efficiency can be enhanced under the optimum pressure contact state.

The production method of the present invention can be applied to any of the wet casting method, the rewetting casting method and the gelling casting method, but is particularly high in the case of the rewetting casting method which requires a high pressing pressure. The effect is remarkable because stable operation can be performed by using a linear pressure and a wide nip width.

The method for producing cast coated paper according to the present invention will be described with reference to FIG. FIG. 1 is a schematic side view illustrating an embodiment of the manufacturing method of the present invention.

An endless belt-shaped elastic body 3 is sandwiched between the cast drum 1 and the press roll 2, and the endless belt-shaped elastic body is supported by a plurality of guide rolls 4 and runs at the speed of the cast drum and the press roll. To do. Then, a cast coating layer containing a pigment and an adhesive as a main component is provided on the base paper, and the pre-cast coated paper 5 in which the cast coating layer is in a wet plastic state is formed from a paper roll 6 to a cast drum and an endless belt. Paper is passed between the elastic bodies, and the cast coating layer is brought into close contact with the surface of the cast drum via the endless belt-shaped elastic body by pressing pressure of the press roll. The adhered cast coating layer is dried by a heated cast drum, and after the drying, the mold is released to produce a cast coated paper.

According to the manufacturing method of bringing the coating layer into close contact with the cast drum via the endless belt-like elastic body of the present invention, the pressure is increased by increasing the nip width as compared with the case of pressing with only the press roll. As a result, the cast coating layer can be more evenly adhered to the cast drum. This area effect promotes the orientation of the pigment in the coating layer by allowing the coating layer temperature to rise under pressure. Therefore, the coating speed can be increased beyond the coating speed limit in the case where poor adhesion results in poor adhesion. In addition, while maintaining or improving the quality of the cast coated paper sufficiently, when the drying capacity is at the coating speed limit, the wet plasticizing water content of the cast coating layer is reduced to reduce the coating water content by reducing the dry water content. Can be increased.

The tension of the endless belt-shaped elastic body causes a pressure contact force to be applied before and after pressing.
This action gradually pressurizes the pressure and gradually reduces the pressure.Therefore, the mottling and partial destruction of the coating layer that cause uneven gloss when the base paper and coating layer are suddenly pressed. The problems of pinholes and drum picks are remedied very effectively by preventing such troubles as well as preventing the suction force caused by sudden decompression. Therefore, by this action, the temperature of the cast drum can be raised and the drying ability can be enhanced.

Further, the endless belt-shaped elastic body is made of a heat-resistant and pressure-resistant material, and the press roll is, for example, a metal roll so that the paper is heated from the back side of the pre-cast coated paper, and the paper is heated by heating. The drying efficiency can also be increased. The endless belt-like elastic body is a method of processing a heat-resistant synthetic resin on a heat-resistant endless belt-like base material, and for example, one that can be stably operated for a long time even at a high temperature of 100 ° C. or higher or a high pressure of several hundred kg / cm Therefore, the press roll having a metal core coated with rubber or synthetic resin cannot withstand high temperature and high pressure due to a defect such as delamination, and can be used at high temperature and high pressure to exert its effect. Since the elastic hardness of the endless belt-like elastic body softens at the operating temperature to give an appropriate nip width, even when the hardness at room temperature is the control standard, the hardness and pressure deformability are designed or selected in consideration of temperature characteristics. It is necessary to have

On the other hand, when the endless belt-like elastic body is heated unnecessarily due to heat from the cast drum or the like, which causes unstable operation, the endless belt-like elastic body is cooled at a position away from the press section to keep a constant temperature. Can be Cooling does not require a special device when natural heat dissipation during traveling is sufficient, but a cooling device is used when particularly positive cooling is required. As the cooling device, for example, a normal means such as a means for passing a cooling medium through a press roll or a guide roll or using cooled air may be used. If the life of the elastic body is shortened by continuing the operation at a high temperature, it is preferable to operate the endless belt-shaped elastic body and the coated press roll at a relatively low temperature. Since the hardness of the synthetic resin endless belt-like elastic body or coated press roll decreases substantially when the temperature rises, it is important to keep the temperature of the elastic body constant in order to maintain a constant pressure contact. Is.

The endless belt-like elastic body which is an important constitution of the present invention is, for example, a heat resistant synthetic fiber or synthetic rubber adhered or coated on one or both sides of a base cloth of heat resistant fiber, and has a pressure resistant compression. It has elasticity. The material used is not particularly limited,
Those used for ordinary endless belt-shaped elastic bodies and coated rolls are used, and examples thereof include epoxy, polyurethane, polyamide, various vulcanized rubbers, etc., or silicon, phenol, polyarylate, vinylidene fluoride and the like. Of course, it is also possible to use a synthetic resin having no base cloth, or instead of the base cloth, a synthetic resin or synthetic rubber processed with rubber or metal. Also, those having different materials and hardnesses on the front surface and the back surface can be selected and used according to the purpose.

The elasticity of the endless belt-like elastic body, that is, the hardness, is based on the hardness of JIS K6301 rubber.
The A hardness is preferably 30 degrees or more. This hardness is used by setting an optimum range according to each cast coating method, press linear pressure, drum temperature, coating speed, target quality, base paper, coating paint formulation, coating amount, and the like. If the hardness of the endless belt-like elastic body is high, the linear pressure works effectively, and if the hardness is low, the cushioning effect such as the thickness, density and smoothness of the paper and the coating layer and the wide nip contact area result in casting. The contact time under pressure acts on the adhesion between the coating layer and the cast drum surface.

It is preferable that both surfaces have a smooth finish of about 1 to 20 μm. If the surface roughness exceeds 20 μm and is rough, the adhesion of the cast coating layer to the cast drum surface may become uneven. In particular, when the texture of the base cloth is coarse, the pattern of the texture is likely to be a close contact pattern, so it is important to finish the surface smoothly. But,
It is not necessary to finish extremely smooth to less than 1 μm.

The thickness is preferably in the range of about 1 to 10 mm. If it is less than 1 mm, it is difficult to obtain the pressure deformation effect as an elastic body. On the other hand, if the thickness is more than about 10 mm, the range of application of pressure deformation is wide, but it is not necessary to deform that much, and if the thickness is thicker than necessary, the running property becomes difficult. In addition, if economically possible, it is preferable that the thickness is not as thick as necessary.

The length of the endless belt-shaped elastic body must be such that it can run over the circumference of the press roll by the guide rolls, and in particular, for example, as described above, due to the necessity of cooling or at a distance from the nip. It is preferable that the surface is washed during traveling so as to have a length such that the purpose of preventing trouble caused by dirt can be achieved. By keeping the temperature of the endless belt-like elastic body constant and maintaining it, the life of the endless belt-like elastic body can be kept long and at the same time the life of the press roll can be extended. This has the effect of increasing the coating speed and the effect of improving the operating efficiency.

The driving means for running the endless belt-like elastic body may be driven by a nip instead of the rotary driving of the cast drum, but a rotary driving device is attached to the press roll and the guide roll to adjust the running speed of each. Preferably. In particular, it is important not to apply unnecessary load to the endless belt-shaped elastic body at the time of starting and stopping.

The cast drum used in the production method of the present invention is not particularly limited, and the one used for ordinary cast coating can be used as it is. Also, the temperature of the cast drum is not particularly limited, and the optimum temperature is selected during the operation depending on each casting method and its conditions.

The press roll of the present invention is preferably a metal roll in some cases, but may be an ordinary rubber or synthetic resin coating roll. Further, although FIG. 1 of the present invention illustrates a single press roll having a cast drum having a diameter of 8: 3 press roll, the present invention is not limited to this.
For example, it is possible to widen the contact width by increasing the diameter of the press roll to further increase the nip width, or by installing a plurality of press rolls having a small diameter and installing a backup press roll. Therefore, the nip width of the present invention can be selected in a wide range such as 10 to 500 mm. However, although the wider the nip width in cast coating is, the better the adhesion effect is, the coating layer that comes into contact with the cast drum is heated immediately, so that the timing at which water in the coating layer evaporates and it is absorbed. The range is important, and the nip width must be adapted to your operating conditions.

Further, although FIG. 1 of the present invention shows the press roll disposed at a position usually used for the rewet casting method, the present invention is not limited to this, and the wet casting method or the gelling casting method can be used. Can also be applied.

The base paper and coating material used in the manufacturing method of the present invention are not particularly limited. The base paper is used in a wide range of tsubo from thin paper to paperboard, and may be, for example, undercoated, pre-smoothed with a super calender, or matte finished. The formulation of the coating material forming the coating layer and the coating amount are variously devised, and there are many techniques, and it can be applied to any of these.

[0035]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Unless otherwise specified, parts and% in the examples mean parts by weight and% by weight, respectively.

Example 1 As a coating liquid for casting, 20 parts of light calcium carbonate, 80 parts of kaolin, and 0.5 parts of sodium polyacrylate were dispersed in water using a Choles disperser to obtain a pigment having a solid content of 65%. It was made into a slurry. In this slurry, 0.5 part of anti-foaming agent tributyl phosphate, 1.0 part of release agent ammonium stearate, 10 parts of 15% aqueous casein solution (as solid content) dissolved with ammonia as an adhesive agent, and styrene-butadiene were used. 16 parts of copolymer latex (as solid content), 2 parts of ZnSO ₄ and water were further added to prepare a cast coating solution having a solid content concentration of 45%.

This cast coating solution was coated on a 100 g / m ² base paper for casting with an air knife coater so that the dry weight was 20 g / m ^2, and dried with an air floating dryer.

Next, paper was passed through a press nip formed by the press roll, the endless belt-shaped elastic body and the cast drum shown in FIG. 1 for cast coating. At this time, the press roll used was a urethane resin coating having a surface hardness of 97 degrees, and the endless belt-shaped elastic body used was a heat resistant fiber base cloth having urethane resin adhered to both sides and a hardness of 95 degrees and a thickness of 5 mm. .

The coated paper for casting, in which the coating layer was wet-plasticized with a 0.5% rewetting liquid consisting of a polyethylene emulsion supplied from the nozzle before the nip, was heated to a mirror surface cast drum with a surface temperature of 105 ° C. To
After being pressed and dried at a press linear pressure of 250 kg / cm, it was peeled off from the cast drum surface by a take-off roll to produce cast coated paper.

Example 2 The press pressure for press contact with the cast drum was 300 kg / cm.
Cast coated paper was manufactured in the same manner as in Example 1 except that

Example 3 Example 1 was repeated except that an endless belt-shaped elastic body having a hardness of 92 degrees was used.
A cast coated paper was produced in the same manner as in.

Example 4 An endless belt-like elastic body having a hardness of 92 degrees was used, and a pressing pressure was 300.
A cast coated paper was produced in the same manner as in Example 1 except that the weight was changed to kg / cm.

Example 5 The endless belt-shaped elastic body was the same as that of Example 1 except that a urethane resin was adhered to the surface of the base fabric of the heat resistant fiber and the resin layer having a hardness of 92 degrees and a thickness of 3.5 mm was used. To produce cast coated paper.

Example 6 A cast coated paper was produced in the same manner as in Example 5 except that the pressing pressure was changed to 300 kg / cm.

Comparative Example 1 Casting was carried out in the same manner as in Example 1 except that the coated paper for casting was passed through a press nip formed by a press roll having a hardness of 97 degrees and an iron core coated with urethane resin and a cast drum. A coated finish was applied to produce cast coated paper.

Comparative Example 2 A cast coated paper was produced in the same manner as in Comparative Example 1 except that the pressing pressure was changed to 300 kg / cm.

Comparative Example 3 A cast coated paper was manufactured in the same manner as in Comparative Example 1 except that the hardness of the press roll was changed to 92 degrees.

Comparative Example 4 The hardness of the press roll was set to 92 degrees, and the pressing pressure was 300 k.
A cast coated paper was produced in the same manner as in Comparative Example 1 except that g / cm was changed.

The cast coated papers of Examples and Comparative Examples obtained as described above were evaluated for white paper glossiness, maximum coating speed during cast operation, and continuous operability. In addition, each evaluation method is as follows. [White paper glossiness] Measured according to JIS P8142. [Maximum coating speed during cast operation] When manufacturing cast coated paper, cast coated paper does not stick to the cast drum surface, drum pick does not occur, and high quality cast coated paper with no gloss unevenness The maximum coating speed that could be stably produced was shown. [Continuous operability] ○: There is no abnormality in the press roll or the endless belt-shaped elastic body, and continuous operability for 3 days or more is possible. Δ: Abnormalities such as peeling and cracks occur on the press roll or the endless belt-shaped elastic body to some extent, but continuous operation is possible for up to 3 days. X: Abnormalities such as peeling and cracks occurred on the press roll or the endless belt-shaped elastic body, and continuous operation for one day or more was impossible.

[0050]

[Table 1]

[0051]

As is clear from the results shown in Table 1, the method for producing cast coated paper according to the present invention has high gloss, smoothness, and uneven gloss, mottle, pinholes, and drums of cast coated paper. There are no pick defects,
Excellent quality can be maintained, coating speed and operation efficiency can be increased, and productivity can be improved.

[Brief description of drawings]

FIG. 1 is a schematic side view illustrating an embodiment of a manufacturing method of the present invention.

[Explanation of symbols]

 1 cast drum 2 press roll 3 endless elastic body 4 guide roll 5 coated paper for casting 6 paper roll

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Miyake 4-3-1, Jokoji Temple, Amagasaki City, Hyogo Prefecture Kanzaki Paper Manufacturing Co., Ltd. Kanzaki Mill

Claims (2)

[Claims] 1. A cast-coated paper comprising a base paper and a cast coating layer comprising a pigment and an adhesive as main components, which is pressed and heated to a heated cast drum while the cast coating layer is in a wet plastic state. In the manufacturing method, an endless belt-shaped elastic body is sandwiched between a cast drum and a press roll and pressure-welded to each other. 2. The endless belt-shaped elastic body has a hardness of JIS A (JI
The method for producing cast coated paper according to claim 1, wherein the SK6301) has a thickness of 30 degrees or more and a thickness of 1 to 10 mm.