JPH11279987A - Production of cast coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing cast coated paper, having good mold release characteristics to cast drum and capable of stably carrying out continuous operation for a long period without lowering gloss of while paper. SOLUTION: In this method for producing cast coated paper by applying a coating solution having pigment and an adhesive to raw paper and pressing the coated layer kept in wet state to planished drum to carry out planishing, a saturated fatty acid and/or its metal salt is directly applied to the surface of planished drum and then, scraped out with a blade to form a thin film of the saturated fatty acid and/or its metal salt.

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 a cast-coated paper, and more particularly to a method for producing a high-quality product continuously and extremely efficiently.

[0002]

2. Description of the Related Art Conventionally, cast coated paper having a high glossiness like a mirror surface has been used for publishing, commercial printing, adhesive label paper, packaging, and packaging. In publishing applications, it is used for covers such as magazines, weekly magazines, comic magazines, and the like. In recent years, comic magazine applications have been increasing. In the commercial printing field, it is used for posters, catalogs, calendars, pamphlets, and the like, and recently the demand has been increasing especially for mail order catalog covers. Demand for adhesive label paper and packaging / packaging is stable in food, light electrical goods, and luxury goods packaging.

In the production of cast coated paper, a base paper surface is coated with an aqueous pigment coating liquid containing a pigment and an adhesive as a main component to form a cast coated layer, and then the cast coated layer is heated. It is manufactured by pressing and drying on a metal mirror drum.

[0004] A typical method for producing this cast coated paper is a wet casting method in which the wet coating layer is directly pressed against the surface of the heating drum as it is. There is known a re-wet casting method in which the coating layer is plasticized by pressure and is pressed against the heating drum surface, and a gel casting method in which a wet coating layer is solidified with a gelling liquid and then pressed against the heating drum surface. In each of these methods, the coating layer in a plastic state is peeled off from the drum surface while being pressed against the drum surface while being pressed against the drum surface.However, obtaining stable release properties under long-term continuous operation increases productivity. It is an important issue for improvement.

Conventional methods for improving the releasability include (1) a method of applying a release agent to a drum surface, (2) a method of adding a release agent to a coating liquid, and (3) a rewetting liquid or gelling. A method of adding a release agent to the liquid has been adopted.

The release agent used in the above method (1) includes synthetic resins such as polyethylene, metal salts of fatty acids or higher fatty acids, fatty acid amides, higher alcohols, tributyl phosphoric acid, paraffin wax and the like. The mold is applied intermittently to the drum. Examples of the release agent used in the method (2) or (3) include a polyethylene emulsion, an alkyl ketene dimer, a nonionic surfactant and the like in addition to the release agent described above.

[0007] However, even when these release agents are used, peeling failure occurs after about 5 hours of operation, and a part of the coating layer starts to adhere to the drum surface (hereinafter referred to as a drum pick). In some cases, the entire paper was stuck to the drum surface and could not be peeled off.

The cause of such a problem is as follows.
It is considered that the release agent interposed between the heating drum and the coating layer is successively carried away by the coating layer during operation, so that the amount of the intervening release agent becomes insufficient, so that a drum pick is likely to occur. Can be It is conceivable to increase the amount of the release agent used in order to improve the releasability, but in this case, new problems such as poor fixing of the ink and poor drying properties occur. Therefore, after stopping the operation about two or three times a day, it is necessary to perform a supply process of applying a release agent to the drum surface.
The current situation is that the production efficiency is greatly reduced because the operation must be stopped for about an hour. Therefore, in the casting method, it is particularly important to improve the releasability so that continuous operation can be performed stably for a long time.

A prior art document, Japanese Patent Application Laid-Open No. H3-111309
In Japanese Patent Publication No. 0, polyoxyethylene alkyl ether is contained in a gelling solution or a rewet solution, and a releasing agent (saturated fatty acid and / or a metal salt thereof) is intermittently applied to the surface of a mirror drum. It was recognized that long-term stable operation would be possible. However, this method is a conventional method, that is, if the amount of the release agent remaining on the drum after a certain period of operation is reduced, the operation is stopped once and the release agent is applied to the drum surface again. Even with this method, the number of times the mold release agent is applied per fixed time is reduced (approximately once every 15 to 20 hours), and a drum pick occurs if the operation is continued for a long time. There is no change, and there has been a demand for a method capable of operating continuously for a longer time in operation.

[0010]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide a cast coating method that can stably cast for a long time without deteriorating the quality such as the glossiness of blank paper in the casting method. An object of the present invention is to provide a manufacturing method capable of manufacturing a paper.

[0011]

Means for Solving the Problems The present inventors have made intensive studies on the above-mentioned problems, and as a result, after coating a base paper with a coating liquid having a pigment and an adhesive, the coating layer is in a wet state. In a method for producing a cast-coated paper in which the surface of the mirror-finished drum is pressed against a mirror-surface drum to obtain a mirror-finished surface, the surface of the mirror-surface drum is directly coated with a saturated fatty acid and / or a metal salt thereof, and then scraped off with a blade using a trailing blade system. The present invention was accomplished by forming a thin film of a saturated fatty acid and / or a metal salt thereof on the mirror surface drum surface by continuously performing the above operations.

The details of the present invention will be described below.

[0013] A problem in continuous operation is the occurrence of drum picks, in which the release agent interposed between the heating drum and the coating layer is successively carried away by the coating layer during operation, and the release of the release agent occurs. It is presumed to occur due to lack of quantity,
If the release agent thin film on the surface of the mirror drum is kept uniform for a long period of time, it is considered that continuous operation is possible.

In view of the above, the present inventors have conducted intensive studies on a method for keeping the release agent uniform on the apparatus for a long period of time. As a result, the saturated fatty acid and / or its metal salt was continuously and directly deposited on the mirror drum surface. It was found that a so-called trailing blade method in which a blade provided at the bottom of the coating liquid tank was pressed against the drum surface at a constant pressure and scraped off after coating with a release agent consisting of As other methods, when a bar coater method using a wire bar or a plain bar or a roll coater method was used, it was recognized that a thin film of the release agent could not be uniformly formed on the drum surface for a long time.

In the present invention, the blade used in the trailing blade system is a metal blade made of stainless steel, bronze, carbon steel, or the like, or a glass fiber blade used for ordinary pigment coating. In such cases, the chrome-plated drum surface is easily damaged during continuous operation, so it is relatively flexible and has excellent heat resistance and chemical resistance, such as silicone rubber or plastic (phenol resin, epoxy resin, etc.). ) And a blade formed from a cotton substrate.
The pressure and angle of the blade pressed against the drum are appropriately adjusted together with the amount of the release agent applied.

Further, as the saturated fatty acid or the metal salt thereof of the present invention, acids such as stearic acid, myristic acid and parathymic acid, and calcium, zinc, barium, potassium and sodium thereof can be used.

According to the method of the present invention, continuous operation is possible in principle, and it is considered that there is no need to stop the operation for drum picking. Because it may bite aggregates,
Actually, it is desirable to stop the operation for about 30 to 40 hours.

Although the apparatus used in the present invention is not particularly limited except for the above, FIG. 1 shows an example of the apparatus.

[0019]

DETAILED DESCRIPTION OF THE INVENTION As the pigment used in the cast coating solution used in the present invention, at least one kind of kaolin, clay, calcium carbonate, zinc oxide, satin white, plastic pigment and the like generally used for papermaking is used. Is done.

In the present invention, as the adhesive to be used, very commonly used latex (styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer or a modified product thereof), casein, soybean protein, synthetic Use of one or more proteins, polyvinyl alcohol, oxidized starch, esterified or etherified starch, enzyme-modified starch, starches such as cold water-soluble starch obtained by flash-drying them, and cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose Is done. These adhesives are used at a ratio of about 10 to 30 parts by weight based on 100 parts by weight of the pigment.

In the coating liquid, a dispersant, a thickener, a water retention agent,
You may use various auxiliary agents mix | blended with the pigment for normal coated papers, such as an antifoaming agent, a waterproofing agent, and a release agent. As the base paper, a basis weight of 3 used for general printing coated paper and cast coated paper is used.
It is base paper of 0 to 400 g / m ² , and high quality paper and medium quality paper are selected and used according to the purpose. In addition, those base papers coated with an undercoat having a pigment and an adhesive, and coated papers coated with a coating liquid on the back surface can also be used.

The method of coating the base paper with the coating liquid is a method using a known coating machine such as a blade coater, an air knife coater, a roll coater, a comma coater, a brush coater, a kiss coater, a curtain coater, and a bar coater. It can be appropriately selected from among them. The amount of the coating liquid applied to the base paper is 15 solids per side of the base paper.
Preferably coated in the range of ~35g / m ^2.

The cast coating method is a method in which a base paper is coated with a coating liquid and then pressed onto a heated cast drum to finish the coating. In the case of the present invention, a coagulation method and a rewet method are preferable in order to improve productivity. Further, an auxiliary agent such as a release agent may be added to the coagulating liquid or the rewetting liquid.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited by these examples. In the examples, parts and% indicate parts by weight and% by weight, respectively.

<Quality Evaluation Method> (1) Glossiness of blank paper: The glossiness at 20 degrees after continuous operation for 20 hours was measured. As the release agent on the drum surface decreases, the releasability of the paper from the drum decreases and the glossiness of white paper decreases.

(2) Continuous operability: The following relative evaluation was performed. ◎: Can be operated continuously for more than 40 hours ○: Can be operated continuously for more than 30 hours △: Can be operated continuously for more than 15 hours ×: Operated continuously for more than 8 hours Can

Example 1 For 100 parts of kaolin,
0.2 parts of a sodium polyacrylate dispersant was added and dispersed in water using a Cowles disperser to prepare a pigment slurry having a solid content of 60%. 0.2 parts of tributyl phosphate as an antifoaming agent, 7 parts of an aqueous casein solution (concentration: 18%) dissolved using ammonia as an adhesive, and 16 parts of a styrene-butadiene copolymer latex were added thereto, and calcium stearate was used as a releasing agent. Was mixed with 0.6 part of a nonionic emulsifier, and finally, water and ammonia were added to adjust the solid content to 48% and the PH to 10.0.

A 10% calcium formate solution was prepared as a coagulating liquid, and 0.3 parts of a polyethylene wax emulsion and 0.3 parts of a polyoxyethylene alkyl ether (carbon number: 16) were added as a releasing agent.

Using the coating liquid prepared by the above method,
A coating solution is applied to a base paper containing only bleached hardwood having a basis weight of 110 g / m ² and kraft pulp alone using a roll coater so that the dry coating amount is 21 g / m ^2, and then a coagulation solution to which a release agent is added To solidify the coating layer.

On the other hand, using a trailing blade device,
After directly applying stearic acid as a release agent to the cast mirror drum, it was scraped off with a silicone rubber blade, and the mirror drum was rotated so that a uniform thin film of the release agent was always formed on the drum surface.

The coated paper obtained by solidifying the coated layer as described above is
The coated paper was pressed with a press roll of 750 mm in diameter and the above-mentioned mirror drum having a surface temperature of 105 ° C. and a diameter of 3000 mm at a press pressure of 130 kg / cm, dried and then peeled off from the mirror drum with a take-off roll to produce a cast coated paper. Speed is 4
Processed at 0 m / min.

Example 2 A coated paper was manufactured in the same manner as in Example 1 except that a metal blade made of stainless steel was used as the blade.

Example 3 A coating liquid containing no calcium stearate and nonionic emulsifier was used as a releasing agent, and a polyethylene wax emulsion and polyoxyethylene alkyl ether (having 1 carbon atom) were used as a releasing agent.
Example 1 except that a coagulation liquid to which no 6) was added was used.
A coated paper was produced in the same manner as described above.

Comparative Example 1 A coated paper was produced in the same manner as in Example 1 except that stearic acid was not continuously applied to the mirror drum.

Comparative Example 2 Example 1 was repeated except that a rotary plain bar made of stainless steel was used instead of the blade.
A coated paper was produced in the same manner as described above.

Comparative Example 3 A coated paper was manufactured in the same manner as in Example 1 except that a comber bar was used instead of the blade, and lecithin as a phospholipid was continuously applied as a release agent.

Comparative Example 4 A coated paper was manufactured in the same manner as in Example 1 except that a roll coater was used instead of the blade.

The above results are shown in Table 1.

[0039]

[Table 1]

As is apparent from Table 1, Examples 1 to 3 were used.
Has excellent white paper gloss and excellent continuous operation. In particular, in Example 3, even when the coating liquid and the coagulating liquid had no release agent, sufficient release properties were exhibited, and the continuous operability was equivalent to that of Example 1. On the other hand, in Comparative Examples 1 and 3, since the amount of the release agent on the mirror surface drum surface decreases and the releasability decreases as the operation is performed for a long time, the glossiness of the white paper gradually decreases. , A drum pick occurs and the paper runs out in 5 to 7 hours. In Comparative Examples 2 and 4, it is difficult to form a thin film of the release agent uniformly on the drum surface for a long period of time, and the glossiness and the drying property of the ink fluctuate.

[0041]

The cast coated paper produced by the method of the present invention has good releasability, and can be stably operated continuously for a long time without deteriorating the quality.

[Brief description of the drawings]

FIG. 1 is a schematic view of a trailing blade type continuous release agent coating apparatus of the present invention.

Claims (2)

[Claims] 1. A method for producing a cast coated paper in which a base paper is coated with a coating liquid having a pigment and an adhesive, and then a wet coating layer is pressed against a mirror drum to perform mirror finishing.
After the saturated fatty acid and / or its metal salt is directly coated on the mirror drum surface, it is continuously scraped with a blade using a trailing blade system, and the saturated fatty acid and / or its metal salt is continuously coated on the mirror drum surface. A method for producing a cast-coated paper, characterized by forming a thin film of: 2. The method for producing a cast coated paper according to claim 1, wherein said blade is formed of a synthetic polymer or a plastic and cotton base material.