JPH04119193A - Production of coated paper and production equipment therefor - Google Patents

Abstract

PURPOSE:To obtain the title high-quality paper with improved operability by continuously transferring the water film on the surface of a cooling roll to the back surface of a web after drying to effectively correct the curls involved in the drying. CONSTITUTION:The surface of a traveling web 1 is coated with an aqueous coating liquid followed by drying; concurrently, a water vapor-contg. gas is sprayed on the surface of a cooling roll 2 to form an aqueous film from moisture condensation, and this aqueous film is continuously transferred to the back surface of the web after the drying, thus obtaining the objective coated paper. It is preferable that said water vapor-contg. gas be a mixed gas comprising water vapor and air.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is particularly suitable for effectively performing curl correction in the production of coated paper such as coated paper or art paper that has a coating layer on one side. METHODS AND APPARATUS.

(Prior art) Coated papers such as coated paper and art paper have a coating layer applied on one side by applying a water-based coating liquid, and others have a coating layer on both sides. In the case of coated paper, when it is heated and dried after being coated with an aqueous coating liquid during the manufacturing process, the fibers of the web shrink unevenly on both sides, and the uncoated side on the opposite side is pulled, resulting in a concave side. Generate curls. This phenomenon occurs, for example, when pasting shoji paper, sometimes when spraying
It is synonymous with the fact that the sag is eliminated by the shrinkage of the paper.

However, if the above-mentioned curl occurs, even if the paper is cut into a flat sheet using a cutter or the like in a subsequent process, the curl remains, and the paper curls during handling, causing trouble and significantly reducing its commercial value.

Therefore, in the past, generally, water was applied to the opposite side of the web where no coating layer was provided, and then dried. It is common practice to flatten the web by imparting curling properties and counteracting the curling properties on both sides. Usually, this water is applied using a metering method in which the water is pumped up from the water pan by an applicator roll, the amount is regulated by a metering roll, and then transferred onto the web. A gravure coating method is adopted in which water is pumped up with a gravure roll and rubbed with a doctor blade in the same manner as described above, and then the water in the minute depressions is transferred onto the web.

(Problems to be Solved by the Invention) However, the above-mentioned recoating method, in which water is directly pumped up with a roll and transferred to the web, is suitable for applying large amounts of water, but is not suitable for applying small amounts of water. For example, even if you adjust the rotation speed and clearance of the roll in metering coating, or make the recesses of the roll smaller in gravure coating, the coating amount will still be 3g/r+? It is difficult to do less than that, and it is impossible to apply a small amount of around 1 g/I'rf, which is suitable for curl correction. Therefore, conventionally, as mentioned above, after applying water, another drying process is required, but this drying requires extensive equipment costs and energy costs for the purpose of straightening curls. Not only does this increase the unit price of the product, but it also reduces the workability of the product.Furthermore, going through two wet-dry cycles causes distortion over the entire width of the web, which causes the web to become wavy. There was a problem that occurred.

In view of the above-mentioned circumstances, the present invention makes it possible to apply a small amount of water suitable for curl correction to the opposite side in the production of coated paper having a coating layer on one side, thereby eliminating the need for drying after applying water. The object of the present invention is to provide a method and apparatus that can easily produce high-quality coated paper at low cost.

(Means for Solving the Problems) In order to achieve the above object, the method for producing coated paper according to claim (1) of the present invention includes applying an aqueous coating liquid to the surface side of a running web, While drying, a water vapor-containing gas is sprayed onto the surface of the cooling roll to form a water film of condensed water, and this water film is continuously transferred to the back side of the dried web. It is something to do.

Moreover, the method for producing coated paper according to claim (2) of the present invention employs a configuration in which the water vapor-containing gas in claim (1) is a mixed gas of water vapor and air.

On the other hand, for the same purpose, the method for producing coated paper according to claim (3) of the present invention is such that, for the same purpose, the web is in contact with the running path of the web, which has a coating layer of an aqueous coating liquid on the front side, on the back side. A configuration is adopted in which a cooling roll is installed and a nozzle for spraying water vapor-containing gas onto the front surface of the cooling roll in contact with the web.

Furthermore, the method for manufacturing coated paper according to claim (4) of the present invention employs a configuration in which a heating means is provided for heating both ends of the cooling roll that are not in contact with the web in claim (3) above. It is something.

(Function) The water vapor blown onto the surface of the cooling roll is cooled and condensed on the surface, forming a continuous or discontinuous thin water film on the surface. As the cooling roll rotates at a constant speed, this water film is continuously transferred to the back side of the web running in contact with the cooling roll, which does not have a coating layer.

However, the degree of condensation mentioned above is almost determined by the amount and temperature of the water vapor sprayed, the rotational speed of the cooling roll, and the surface temperature, so by adjusting these conditions, the amount of water in the water film can be freely set to a very small range. can. Therefore, it is possible to reduce the amount of water applied to the back surface of the web to a very small amount around Ig/rd, which is suitable for curl correction, without drying after application.

The water vapor-containing gas that is blown onto the cooling roll surface is
A gas containing 100% water vapor may be used, but a mixed gas of water vapor and air is preferable.In the case of a gas containing 100% water vapor, the amount of normal spraying may result in too much dew condensation on the surface of the cooling roll. If you restrict the amount of gas delivered with a valve, etc. to prevent this, the nozzle blowout pressure will drop and the blowout will vary in the width direction, resulting in a stable water film not being formed on the roll surface and a poor water coating profile on the web. Therefore, there is a possibility that a sufficient curl correction effect may not be achieved.

On the other hand, if water vapor is diluted as the above-mentioned mixed gas, the amount of water vapor discharged can be reduced without lowering the blowing pressure, so that a stable water film can be formed with an appropriate degree of condensation.

The cooling means for the cooling roll is not particularly limited, but it is convenient to make the roll hollow and allow cooling water or cooling air to flow through the roll, and the cooling temperature is preferably in the range of 0 to 30°C. Although the material of the cooling roll is not particularly limited, from the viewpoint of thermal conductivity, it is preferable to use a chrome-plated aluminum roll rather than a chrome-plated steel roll.

In addition, on both sides of the cooling roll that do not come into contact with the web, there is a risk that condensed water may accumulate and grow and cause water to splash onto the web surface, so to prevent this, both sides are heated to evaporate the condensed water. Alternatively, it is desirable to provide a heating means to prevent condensation.As such heating means, in addition to heating both sides of the cooling roll from the outside with electric heat or hot air, heating both sides of the hollow cooling roll with partition walls. It is also possible to adopt a method in which the web is separated from the central side that contacts the web, and a heating medium such as heated air, hot water, or steam is passed through the separated inclined wall to heat it from the inside.

Note that the cooling roll may be rotated in either a forward direction or a reverse direction relative to the running of the web.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In the first embodiment shown in FIG. 1, 1 is a continuous web having a coating layer formed by coating and drying an aqueous coating liquid in the previous step on the front side, and 2 is the back side thereof. 3 is a nozzle box having a slit-shaped outlet 3a along the width direction of the roll 2 facing the front surface of the roll 2 in contact with the web 1; 4 is an air heater 5; A mixing tube 6 mixes the heated compressed air A and steam S and supplies the mixture to the nozzle box 4, and 6 is a heater that heats both sides of the cooling roll 2 from the outside.

As shown in FIG. 2, the cooling roll 2 has a cylindrical shape, and the inside thereof includes a pair of left and right partition walls 7.7, a central cooling zone 2a corresponding to the width of the web 1, and non-cooling zones 2b on both sides.
It is divided into 2b and 2b.

The cooling zone 2a is connected via a pair of left and right pipe-shaped support shafts 9.9 passing through the partition wall 7 and the end plate 8, with one end connected to an external cooling water inlet chamber 10a and the other end connected to an external cooling water inlet chamber 10b. By filling the interior with cooling water W introduced at a constant flow rate from the inlet chamber 10a and discharging it to the outside through the outlet chamber 10b, the roll surface in the range of the zone 2a is kept constant. It is set to maintain a cooling temperature of

Moreover, the heater 6.6 is located in the non-cooling zone 2b on both sides.

2b, and hot air blowing is set to heat the roll surface of each cooling zone 2b by a method or an electric heating method. 11 is a bearing.

In the above configuration, the air outlet 3a of the nozzle box 3
When a mixed gas of water vapor S and heated air A is blown onto the surface of the cooling roll 2, the water vapor S in the mixed gas is
is cooled to below the dew point and condenses on the roll surface to form a water film, and this water film is transferred to the surface of the running web 1 by the rotation of the roll 2, and the web 1 is humidified on the surface side by this transfer. The film is wound up by a winder (not shown) in a state in which curls caused by drying after application of the aqueous coating liquid in the previous step are corrected. In this case, since the above-mentioned mixed gas is used as the water vapor-containing gas, it is possible to maintain the blowing pressure from the blow-off port 3a at a sufficient strength to reduce the amount of water vapor, thereby curling the water film. It can be made stable with a very thin thickness suitable for correction. In addition, on both sides of the cooling roll 2 through which the web 1 does not pass, due to the heating of the heater roller, no dew condensation occurs on the surface, or even if dew condensation does occur, it evaporates and dissipates, thereby avoiding water splashing caused by the accumulation and growth of condensed water. be done.

FIG. 3 shows a second embodiment in which an internal heating method using a heating medium is used as heating means for both sides of the cooling roll 20 in place of the heater 2 of the first embodiment.

In this case, a heating zone 2c is formed between the partition wall 7 and the end plate 8 in the cooling roll 2, and the end plate 8, which is fixed so that its peripheral edge slides in airtight contact with the roll peripheral wall, is heated. By having a medium population 12a and an outlet 12b, and introducing a heating medium H such as heated air, hot water, or steam into the heating zone 2C from the inlet 12a and discharging it from the outlet 12b,
Both sides of the cooling roll 2 are heated from the inside to prevent condensation on the surface or to evaporate condensed water.

Further, FIG. 4 shows a third embodiment in which water coating for curl correction is carried out in two stages. In this case, two cooling rolls 2.
A nozzle box 3 corresponding to each roll 2 is provided, and the same mixed gas as described above is branched and supplied from the mixing tube 4 and is blown onto the surface of the corresponding cooling roll 2 from each nozzle box 3. A water film is formed by condensed water on the roll surface, and water coating is performed by transferring the water film twice on the back side of the web 1 by rotating both rolls 2.2. In this two-step coating, conditions are set so that the total amount of water applied by both cooling rolls 2, 2 is an amount suitable for curl correction without requiring subsequent drying.

The table below shows the water vapor pressure of the mixed gas when an aluminum chrome plated roll is used as the cooling roll 2 in the apparatus configuration of the first embodiment shown in FIGS. A web with a coating layer on the surface side was obtained by applying and drying an aqueous coating liquid under various conditions (base paper basis weight 64 g/I, moisture content 4.8
The results show the results of water coating at a coating speed of 150 m/sin on the back side of 100% solids. Concentration 6
It is coated with a coating liquid having a viscosity of 600 CPS (Brookfield type viscometer) at 0%.

Kaolin (manufactured by EMC, UW-90) 80 parts heavy calcium carbonate (manufactured by Bihoku Funka Kogyo, Softon 2200)
20 parts styrene-butadiene copolymer latex (manufactured by Sumitomo Nogatatsuta Co., Ltd., 5N-3
07) 10 parts oxidized modified starch (manufactured by Tamago Cornstarch Co., Ltd., Ace A) 5
0.3 parts Sodium polyacrylate 0.3 parts The relationship between the steam pressure and the moisture content of the coiled product is shown in Figure 5.The curl straightening effect in the following table is based on the applied coating cut onto a skewer after being wound. The degree of curlability of the paper was evaluated in the following four stages.

◎... No curling property at all 0... Slight curling property that can be ignored in practical terms Δ...
Curling property that leads to quality deterioration ×...Difficulty in commercialization due to significant curl It can be seen that a sufficient curl straightening effect can be achieved without requiring drying after application.

Furthermore, from FIG. 5, it can be seen that when other conditions are constant, the amount of water applied is approximately proportional to the water vapor pressure, that is, the amount of water vapor sprayed. In addition, the suitable range of winding moisture content is 6.0~?
, 0wt% (corresponding to 3.4 in the table), and 7.0wt%
%, the curl straightening effect is good, but quality deterioration due to excessive humidification becomes a problem.

(Effects of the Invention) According to the method and apparatus of the present invention, in the production of coated paper having a coated layer on one side, curling caused by drying of the coated layer after coating is prevented from occurring on the coated layer side. It can be effectively corrected by applying a small amount of water to the opposite side of the web, and there is no need for drying after applying water as in the past, so equipment costs and energy costs can be significantly reduced.
Operability is improved, the deterioration in quality due to repeated drying as in the conventional method is avoided, and the above-mentioned high-quality coated paper with curling properties can be produced.

Further, according to the method of claim (2) of the present invention, there is an advantage that a thin and stable water film can be formed on the surface of the cooling roll.

Further, according to the apparatus of claim (4) of the present invention, there is an advantage that water splashing due to accumulation and growth of condensed water on both sides of the cooling roll not in contact with the web can be prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing the water coating process in the first embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG.
The figure is a joint sectional view of the cooling roll in the second embodiment, and the fourth
The figure is a schematic side view showing the water coating process in the third embodiment, and FIG. 5 is a correlation characteristic diagram between the water vapor pressure and the winding moisture content when the water coating process of the first embodiment is applied. DESCRIPTION OF SYMBOLS 1... Web, 2... Cooling roll, 3... Nozzle box, 6... Heater (heating means), A... Air, S... Steam.

Claims (4)

[Claims] (1) Apply a water-based coating liquid to the surface side of the running web,
A coated paper characterized in that while drying, a water vapor-containing gas is sprayed onto the surface of a cooling roll to form a water film of condensed water, and this water film is continuously transferred to the back side of the web after drying. manufacturing method. (2) The method for producing coated paper according to claim (1), wherein the water vapor-containing gas is a mixed gas of water vapor and air. (3) A cooling roll is installed on the running path of the web, which has a coating layer of water-based coating liquid on the surface side, and the web contacts the web on the back side, and a cooling roll is installed on the surface of the cooling roll at the front side where the web contacts the web. Coated paper manufacturing equipment equipped with a nozzle that sprays water vapor-containing gas. (4) The coated paper manufacturing apparatus according to claim (3), further comprising heating means for heating both ends of the cooling roll that are not in contact with the web.