JP2930776B2 - Method for producing gravure paper and gravure paper obtained by the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of gravure paper, which is bulky, has high rigidity and high opacity when finished to a predetermined static smoothness, and has the same static smoothness but has a dynamic smoothness. Of gravure paper with excellent miscibility and excellent dot reproducibility due to its excellent reproducibility and its production method
It relates to gravure paper that is.

[0002]

2. Description of the Related Art There is still a stable demand for gravure paper due to enhancement of so-called gravure pages of magazines. A gravure page is indispensable because it can reproduce a vivid color tone and a deep image in fashion, art, cooking pages, and the like. Multicolor gravure is mainly used for publishing, and medium-grade coated paper is mainly used. In recent years, matte coating has become more noticeable even in gravure as the demand for matte coated paper has increased due to its good print finish and gentleness to the eyes.

In general, smoothness is extremely important for producing a gravure printing effect. In the case of paper for normal use,
Medium paper is 30 to 50 seconds (measured by Beck smoothness meter:
In contrast to JIS P8119), gravure paper is super-calendered and is 100 to 300 seconds, which is a considerably high level as uncoated paper. In some cases, super calendar processing is not performed, and the degree of smoothness is increased as much as possible using a machine calendar for gravure. 7 in that case
The smoothness is about 0 to 100 seconds. Such a highly smooth finish is the same in the case of coated paper.

As described above, since it is necessary to increase the smoothness of the gravure paper by the conventional calendering process, the density of the paper is greatly increased, and the characteristics such as opacity and rigidity are greatly reduced. On the other hand, smoothness cannot be reduced to reduce misdots and improve dot reproducibility as gravure printing suitability. In order to solve such problems, it is necessary to produce a highly smooth paper while minimizing the increase in density.

As described above, in the production of gravure paper, calendering using a super calendar or the like is performed, but a significant increase in density cannot be avoided. As a method of improving the smoothness and gloss by suppressing an increase in density by calendering, there is known a method of applying heat to a paper surface or applying heated steam immediately before calendering or calendering using a high-temperature roll.

[0006] It is generally said that humidification is more effective than heating to improve the surface properties of paper (M. Agrout).
s; Tappi J. 66 (10), 96 (1983)). In the case of water application, there is a problem that the average moisture of the paper increases by at least about 1.5% or more at a minimum, the increase in density increases, and there is a large problem of adhesion of the paint to the calender roll.

In view of the above facts, a method of calendering after applying mild heating steam to paper has been developed in recent years, and its effect has been recognized (JP-A-2-160993) .
Report ). However, this method has been applied for coating lightweight printed paper is different to the present invention basically in the following points.

(1) In the present invention, Japanese Patent Application Laid-Open No. 2-160993
In contrast to the method disclosed in
The quality according to the present invention is obtained only by limiting the calendering conditions after the paper moisture increase rate is set to 0.3 to 1.2% and the processing temperature to 100 to 150 ° C as described in the above-mentioned claim 1. It has been recognized that the above effect can be obtained (the same effect cannot be obtained by the method disclosed in Japanese Patent Application Laid-Open No. 2-160993). Further, calendering can be performed under the above-mentioned high temperature conditions only by using a soft calender having a resin roll having high heat resistance.

[0009]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned drawbacks of the gravure paper. As a result, the rate of increase in the paper moisture was previously 0.3 using heated steam.
After humidifying and heating the paper surface to become ~ 1.2% ,
By performing soft calendering at a temperature of 100 to 150 ° C., the suitability for gravure printing (dynamic smoothness, misdots, halftone dot reproducibility, etc.) can be improved without increasing the static smoothness unlike the prior art. Gravure paper with improved bulkiness, opacity, rigidity, and tensile strength, and a method for producing gravure paper having unprecedented superior quality, and a gravure paper obtained by the method. To provide.

[0010]

The present invention SUMMARY OF] is in the manufacturing process of a gravure paper, previously paper moisture increasing rate at low pressure in the calendering immediately before allowed out injection mild heating steam on paper 0.3.
After humidifying and heating the paper surface to 2% , 100%
A method for producing gravure paper, characterized in that soft calendering is performed within a temperature range of 150 to 150 ° C. Further, the present invention is a non-coated paper or a gravure paper having a coating amount of 10 to ²⁰ g / m ^{2 on} one side obtained by the above-mentioned production method.

A feature of the present invention resides in that low-pressure, mild heating steam is adhered to the surface of the gravure paper immediately before calendering, and the gravure paper is processed under a specific temperature condition. The conventional steam humidifier has the following problems when used continuously in an actual machine. That is: (1) The steam drain falls or is blown off on the paper. (2) The vapor scatters around, dew forms on peripheral devices, and dew drops on paper. (3) Steam leaks to the surroundings, deteriorating the working environment. And so on.

[0012] In order to solve the above problems, there has been proposed an apparatus which uses the Coanda effect to flow steam in parallel and opposite to paper. This advantage can be longer contact time between the paper and the steam can be prevented from entering the air coming around and bring the paper is that the running stability of the paper is improved.

The main concept of the method of the present invention is as follows. Thermal energy of the steam is carried by the vapor by the temperature difference between the sheet and the steam to condense a fine to the paper surface. At this time, if air intervenes, the air acts as a heat insulating material, the efficiency of heat transfer is significantly reduced, and condensed water ends up as large particles, and the adhesion of condensed water to paper becomes uneven. After that, the moisture and temperature unevenness increase. Only by solving the operational problems and improving the thermal efficiency in this way, it became possible to use the device in front of the calendar.

The conventional calendering treatment is performed at about 50 to 80 ° C., and the paper is crushed with a considerably high linear pressure in order to obtain a predetermined surface property. In order to obtain the same surface properties at a lower linear pressure, to increase bulkiness and to improve strength characteristics, it is necessary to densify only the surface layer of the paper. As this method, a so-called temperature gradient calendering method has been proposed in which the surface property is developed by crushing only the surface layer of the paper by heating (MFGrattonet, al,; Pulp and Paper Can.,
88 (12), T461 (1987), etc.).

Another method is to crush only the surface layer of paper by humidification. This method differs only in heating or humidification, and its working mechanism is basically the same as that of the temperature gradient calendar method. That is, by calendering immediately after only the surface layer of the paper was plasticized by humidification, a mechanism for transferring the calender roll surface to plasticized paper surface.

The present inventors have conducted intensive studies on the humidifying calendar method. As a result, when the humidification was performed by a water shower, the humidification amount increased (the average moisture content of the paper increased by 1.5% or more). It was recognized that the surface property was greatly improved by the treatment, but at the same time, the width of the decrease in the bulk became large. This is considered to be due to the fact that the moisture permeated not only into the surface layer but also into the middle layer of the paper. In addition, this method has another problem that it is difficult to control the paper profile. Further, in this case, it was also found that water adhering to the paper surface acts in a direction to lower the temperature of the calender roll.

As described above, in order to plasticize the paper surface, it is desirable to treat the calender roll at a higher temperature. However, the humidification method using a water shower has a negative effect because it acts in a direction to lower the calender roll temperature. I'm done.

From the above examination, the present inventors have recognized that the humidification method using steam is the best. Since the steam used in the present invention has a high temperature (100 ° C. or higher), the paper surface is simultaneously humidified and heated to be plasticized. Therefore, when the calendar treatment after the steam humidifier, the surface of the paper in the case of non-coated paper, in the case of coated paper increases observed density of the paper surface portion close to the pigment coating layer and the pigment coating layer surface However, the density of the middle layer of the paper does not increase, the average density of the paper as a whole does not increase so much, a predetermined surface property can be obtained by low linear pressure treatment, the bulkiness is high, the strength is high, A gravure paper excellent in the above is obtained. Also, when the paper is finished to the same density and bulk as in the case of the conventional calendering method, gravure paper having excellent quality as described above can be obtained.

A prior art (Japanese Patent Laid-Open Publication No. Hei.
The present invention is basically different from the invention described in Japanese Patent No. 160993 in the following points. The calendering conditions after such moisture increasing rate of paper by applying steam is from 0.3 to 1.2% in the paper in the present invention, the calendering temperature as described in the claim 1 100-150 It is specified in ° C.

In the above prior art, the calendering treatment by steam humidification makes it possible to improve the Oken type smoothness (static smoothness) while minimizing the increase in the density and the decrease in the bulk of the paper. It is argued that printability can be improved for the first time. However, dynamic smoothness may not change when Oken type smoothness according to the present onset Akira Way Method is to improve, it has become possible to improve the printability.

In the above prior art, the bulk (the reciprocal of the density),
While the stiffness and opacity tended to decrease, it was also recognized that the method of the present invention improved the bulk, opacity and stiffness and further improved the tensile strength. The reason for this is that the mechanism of surface appearance of paper depends on complex factors such as heat and moisture plasticity of paper, thermal conductivity of paper, elastic modulus, paper layer structure, and elasticity of elastic roll. I'm not sure because it's possible, but it's probably because of the following differences:

First, as described above, the calendering temperature is set to 10
When the treatment is performed at a temperature lower than 0 ° C., since the temperature of the calender roll is lower than the temperature of the surface layer of the paper, the temperature of the very surface layer of the paper heated in advance by steam is conversely cooled. This has a negative effect on the effect of plasticizing only the Oken type, and as a result, even if the paper is finished to the same density, the Oken type smoothness does not improve.

Further, when the treatment is carried out at a high temperature exceeding 150 ° C. , the heating and the humidification by steam become excessive, and the surface properties are greatly improved by the synergistic effect, but the density is extremely increased as described above. As a result, the bulk, opacity and rigidity are reduced. According to the method of the present invention,
By obtaining the same Oken-type smoothness (static smoothness) by processing at a high temperature of up to 150 ° C. , the processing can be performed at a lower linear pressure, so that the bulk and opacity are improved. Further, since it is not necessary to give a strong ironing to the paper, the rigidity and the tensile strength are improved (10).
There is no effect below 0 ° C).

[0024] The present invention makes it possible to calender treatment began by using a soft calender comprising a combination of heat, a special resin roll and a metal roll having excellent pressure resistance at high temperatures, such as described above. The reason for this is that in the case of a commonly used super calender, the maximum heating temperature of the roll is generally about 85 ° C. because the internal heat of the cotton roll, which is an elastic roll, is large and the heat resistance and pressure resistance are limited.
This is because it is limited to the following. In the case of a gloss calender generally used in the production of paperboard, the metal roll side is used even at a high temperature of 100 ° C. or higher. However, the elastic roll, a rubber roll, is remarkably inferior in durability, so it is generally used in high-speed paper machines and high-speed coaters. Is not applicable.

Therefore, the use at a high temperature and a high pressure becomes possible only by adopting a soft calender having a special resin roll excellent in heat resistance and pressure resistance. As the device for ejecting the low-pressure, mild heated steam flow to the paper of the present invention, a device for ejecting steam in parallel with the paper, a device for ejecting a fixed angle from the nozzle to the paper surface, and the like, the steam adheres to the paper surface. Any material that can be adjusted to raise the temperature and moisture of the paper appropriately can be used.

When the steam used in the present invention is applied to paper with low pressure and mild heating steam, the steam pressure used is 1 kg / cm.
² or less, the steam flow rate is 15~18kg / Hr / m width Dearuko
And it is necessary to apply steam within a paper moisture increase rate of 0.3 to 1.2%. The reason is that as described above, when the vapor pressure is high and the flow rate is too large, excess moisture permeates into the middle layer of the paper, and the bulk after calendering is greatly reduced. On the other hand, if the amount of steam adhering to the paper is too large, in the case of coated paper, there is a problem that the surface of the coated layer is taken off by a calender roll. Conversely, if the steam flow rate is too small, there is a possibility that the smoothness and gloss unevenness of the paper may occur, and the effects of humidification and heating are reduced, and the effects of improving smoothness and printability are also reduced.

[0027] Therefore in an appropriate moistening conditions, no paper moisture increase rate grant vapor in the range of 0.3 to 1.2%
Must . It is better that the time from the application of the steam to the start of the calender roll nip is as short as possible, from 0.01 to 0.2.
It is desirable to be within 5 seconds. If the time is longer than this, vapor particles penetrate into the middle layer of the paper, and the bulk after calendering treatment is greatly reduced. As a result of this study, it was found that the hardness of the elastic roll used was desirably in the range of Shore D 87-93.

Although the reason is not clear, when the hardness of the elastic roll is lower than Shore D87 , the nip width increases and the surface pressure on the paper increases. In this case, the time required to transfer the surface of the metal roll to the paper surface is longer, and the linear pressure is smaller than the surface pressure, so the glossiness of the paper is higher, but slightly closer to the middle layer than the surface layer of the paper. Oken-type smoothness, which measures smoothness up to, does not appear as a very large improvement.

Conversely, when the elastic roll hardness is higher than that of the Shore D93 , the nip width is narrow and the linear pressure applied to the paper is high, so that it is considered that the improvement in the smoothness of the Oken method is large. However, if the roll hardness is excessively high, the roll is damaged when foreign matter passes and its resilience is inferior, making it impractical. In terms of quality, there is no difference from the calender method using the conventional metal roll / metal roll combination. U. Therefore, it is necessary to use an elastic roll having an appropriate hardness range.

The uncoated paper used in the present invention may be either a medium quality paper or a high quality paper, and has a basis weight in the range of 50 to 180 g / m ² .
Is preferred . The filler added to the base paper may be talc, clay, kaolin, calcium carbonate or any other commonly used filler. Furthermore, the gravure paper of the present invention includes
If necessary, additives usually used in papermaking, such as a dye, a sizing agent, a dry paper strength enhancer, a wet paper strength enhancer, a fixing agent and a retention aid, are included.

The coated paper used in the present invention has a coating amount of 10 to ²⁰ g / m ² on one side, and may be either single-sided or double-sided. Pigments applied to the base paper surface include clay, kaolin, talc, aluminum hydroxide,
Calcium carbonate, titanium oxide, magnesium carbonate, synthetic silica, satin white, alone plastic arsenide segment etc., or may be used in combination several. In addition, as a binder used in the coating liquid , starch, polyvinyl alcohol, latex, etc. are used alone.
Alternatively, several types can be used in combination.

As a coating method, a coating apparatus generally used for producing coated paper, for example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a bar coater, a curtain coater, a die slot coater, a gravure coater or the like is used. It is coated on the base paper in one layer or in multiple layers by on-machine or off-machine.

[0033] While the present inventors have imparted heavy proof results various studies calendar method by heating or humidifying only the surface layer of the paper as a means for plasticizing, mild heating steam at low pressure to the surface of the gravure paper The paper moisture increase rate is 0.3-1.2%
So as to, after heating the paper surface humidification and, 100
By performing soft calendering at a temperature of 150 ° C. , even if static smoothness is not improved as in the related art,
It was recognized that the dynamic smoothness was improved, the number of miss dots was small, and the halftone dot reproducibility could be dramatically improved. Furthermore, it was also recognized that the bulkiness and the strength characteristics such as rigidity and tensile strength were also improved, and that a gravure paper having unprecedented excellent quality was obtained.

[0034]

Examples of the present invention will be described below. For the calendering process, a two-stack soft calender having a two-stage soft nip composed of a combination of a chilled roll and a resin roll having a heating device (made by Minamisenju Seisakusho Co., Ltd., roll surface length)
Before each nip, a humidifier (steam foil of Aikawa Iron Works Co., Ltd.) was installed so that steam would be blown out to the paper surface on the side that hits the chilled roll using 1050 mm, soft roll hardness, and Shore hardness D89). Was performed.

Example 1 A coating liquid prepared by mixing 50 parts by weight of calcium carbonate having an average particle diameter of 0.7 μm with base paper having a basis weight of 62 g / m ² , was coated on one surface 13.
g / m ² , using a coated paper coated on both sides at a steam pressure of 0.8 kg / cm ² and a steam flow rate of 50 kg / Hr / m with a constant width of steam. After a second, the sheet was calendered so as to enter each calendar nip. At that time, the treatment was performed at a calender roll temperature of 120 ° C.

Example 2 Except for using uncoated fine paper having a basis weight of 125 g / m ² ,
Steam was applied to paper under exactly the same conditions as in Example 1 above, and calendered.

Comparative Example 1 A calender treatment was carried out under the same conditions as in Example 1 except that the calender treatment was performed at a calender roll temperature of 70 ° C.

Comparative Example 2 A calender treatment was performed under the same conditions as in Example 1 except that the calender treatment was performed at a calender roll temperature of 70 ° C. without using any steam.

Comparative Example 3 A calender treatment was performed under the same conditions as in Example 2 except that the calender treatment was performed at a calender roll temperature of 70 ° C.

<Quality Evaluation Method> White Paper Gloss: Measured at an angle of 75 degrees according to JIS P-8142. -Static smoothness: JAPAN Tappi No.5 Measured by Oken-type smoothness tester. Dynamic Smoothness: Using a Parka Print Surf Surface Roughness (PPS) meter (Model No. PPS-78, manufactured by Nomura Corporation), the value is displayed as a roughness in μ units. The smaller the value, the higher the dynamic smoothness.

Stiffness: Measured with a Clark stiffness tester according to JIS P-8143. -Tensile strength: Measured with a JIS P-8114 Shopper type tester. -Gravure printing suitability: Using a gravure printing suitability tester manufactured by Kumagai Riki Kogyo Co., Ltd., black ink was solid-printed on a plate having a depth of 35 µm. Evaluation of mistakes dot was evaluated by the number of ink transfer failure portion of ² per the printing sample 1 mm. The evaluation of halftone dot reproducibility was indicated by a five-step relative evaluation as viewed with an optical microscope.

[0042]

[0043]

As is clear from the table, unlike the conventional steam humidifying calendar technology, the steam is applied to the paper to increase the paper moisture increase rate.
Is set to 0.3 to 1.2%, and the calendering temperature is set to 100 to 150 ° C. as described in claim 1 , and the calendering is performed by the method of the present invention for soft calendering. Since the dynamic smoothness is improved even if the target smoothness (Oken-type smoothness) does not change, it is possible to produce gravure paper with less miss dots and excellent dot reproducibility. Further, it is bulky and can improve strength characteristics such as rigidity and tensile strength. Therefore, the gravure paper manufactured by the gravure paper manufacturing method of the present invention has excellent quality characteristics which have not been obtained in the past, and the product value thereof is extremely large.

Continuation of the front page (56) References JP-A-2-160993 (JP, A) JP-A-62-177299 (JP, A) JP-B-47-38882 (JP, B1) WO 90/12920 (WO, A2) (58) Fields investigated (Int. Cl. ⁶ , DB name) D21G 1/00-9/00 D21H 11/00-27/42

Claims (3)

(57) [Claims] In a method for producing a gravure sheet, light heating steam at a low pressure is applied just before calendering the gravure sheet so that the paper moisture increase rate becomes 0.3 to 1.2%, and the surface of the sheet is adjusted. After humidification and heating, the calender roll temperature becomes 1
A method for producing gravure paper, characterized by performing a soft calendering treatment in the range of 00 to 150 ° C. 2. An uncoated gravure paper, wherein the gravure paper produced by the production method according to claim 1 is an uncoated paper. 3. A coated gravure paper produced by the production method according to claim 1, wherein the gravure paper has a coating amount of 10 to ²⁰ g / m ² on one side.