JP3246619B2 - How to dry coated paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drying coated paper for printing, and more particularly to a method for drying a coated paper for printing with excellent printing strength and printing mottling.

[0002]

2. Description of the Related Art In recent years, visualization, colorization, and sophistication of printed matter, as well as the speeding up of printing with the progress of printing technology, have resulted in high quality printing coated paper with high printing strength and excellent mottling. High printability is required. For this reason, various proposals have been made for a method for producing a coated paper for printing, and improvement of a method for drying the coated paper is one of them.

Conventionally, a method of drying a wet coated paper obtained by applying a coating liquid containing a pigment and an adhesive as a main component to a base paper includes a method using a hot air dryer, a gas IR dryer, an electric IR dryer, a cylinder dryer, or the like. The drying and the moisture control of the coated paper are performed according to the amount and temperature of the hot air in the hot air dryer, the gas flow rate in the gas IR dryer, the electric output in the electric IR dryer, and the steam amount in the cylinder dryer.

For example, a method for controlling the moisture content of a coated paper in a drying process (Japanese Patent Publication No. 59-12949, Japanese Patent Application Laid-Open No. 3-269192, etc.)
However, all of these methods detect the moisture content of the paper after passing through the hot air dryer, and detect the hot air temperature, the amount of hot air, the distance between the hot air blowing portion of the dryer and the coated paper based on the detected moisture content. Is a method of controlling moisture by adjusting the water content, so that the amount of defective paper can be reduced by stabilizing the moisture content, but the steam of hot air from the hot air dryer related to the film forming strength of the adhesive in the coating liquid The partial pressure changes, and sometimes defects such as reduced print strength and print mottling occur.
There is still room for improvement.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a drying method for stably producing a coated paper having high printing strength and free from mottling during printing.

[0006] In the conventional drying method in the drying step, the quality of the coated paper after drying varies, and in some cases, picking or mottling occurs during printing. Causes such as quality variations and occurrence of mottling during printing are presumed as follows. That is, the coated paper has thickness unevenness in the coating layer due to the formation unevenness inherent in the base paper, and the tendency increases as the speed of the paper machine or the coating machine increases.
Variations in the base paper moisture, coating liquid concentration, coating amount, hot air temperature, outside air temperature, etc., or changes in the coating (drying) speed, etc., cause drying unevenness and binder migration based on the thickness unevenness of the coating layer, resulting in mottling. Outbreaks are being promoted. On the other hand, the picking that occurs at the time of printing is almost caused by the amount of the adhesive in the components of the coating liquid and the adhesive strength at the time of forming the film, and particularly, the synthetic method typically used in the adhesive. It is necessary to dry the resin latex film at a temperature of Tg or higher, and the drying temperature affects the adhesive strength, that is, the printing strength.

In the method of drying coated paper by hot air, the present inventors pay particular attention to the dew point temperature of hot air and the temperature of hot air, and determine appropriate drying conditions for stably obtaining high quality coated paper. As a result of diligent research on the present invention, extremely remarkable effects were obtained within a certain range of the hot air dew point temperature and the hot air temperature, leading to the present invention.

[0008]

According to the present invention, there is provided a method of applying a coating liquid containing a pigment and an adhesive as a main component to a base paper and performing drying in a drying step with hot air, wherein a dew point of hot air in a hot air dryer is used. Temperature 45-55 ℃ and hot air temperature 100-180 ℃
Input from the dew point detector and temperature detector installed in each hot air dryer unit, the amount of steam blown into each hot air circulation system, the amount of fresh air introduced, heat exchange for hot air temperature adjustment A method for drying coated paper, comprising a control device for controlling the steam amount of the vessel and controlling the dew point temperature of hot air and the hot air temperature.

[0009] The hot air dew point temperature of the present invention must be 45-55 ° C. If the dew point temperature is out of this range, mottling during printing of the coated paper occurs due to drying unevenness and migration of the binder. If this temperature is lower than 45 ° C., the printing strength of the coated paper will decrease.

Further, the hot air temperature must be 100 to 180 ° C. If the temperature is lower than 100 ° C., the printing strength of the coated paper and the mottling at the time of printing are inferior, and if it exceeds 180 ° C., the mottling at the time of printing becomes poor.

According to such a drying method, the printing strength becomes I
With a high intensity of 140 cm / s or more by the method according to JISP8129 using a GT printability tester, and the standard deviation of absorbance after two-color printing measured using a two-wavelength chromatograph scanner CS-9000 is 0.035 or less. Excellent coated paper with very little unevenness in ink density can be stably obtained.

[0012] The coating liquid composition in the method of the present invention comprises:
Similar to the conventional coating liquid composition, it is mainly composed of a pigment and an adhesive. As the pigment, for example, one or more kinds of ordinary coated paper pigments such as clay, kaolin, calcium carbonate, titanium dioxide, aluminum hydroxide, barium sulfate, zinc oxide, satin white, calcium sulfate, talc, and plastic pigment are appropriately selected. Used as

Examples of the adhesive include proteins such as casein, soybean protein, and synthetic protein; starches such as phosphorylated ester, oxidized starch and enzyme-modified starch; styrene-butadiene copolymer, styrene-butadiene-acrylic ester Copolymer, conjugated diene polymer latex such as methyl methacrylate / butadiene copolymer, acrylic polymer latex such as acrylate and / or methacrylate polymer or copolymer, ethylene / vinyl acetate copolymer Vinyl-based polymer latex such as coalesce, or a functional group-modified latex such as carboxyl group and hydroxyl group of these various polymers, polyvinyl alcohol, olefin dicarboxylic acid resin, synthetic resin adhesive such as melamine resin; carboxymethyl cellulose, Cells such as hydroxyethyl cellulose Over scan normal one or more coated paper for adhesive such derivative is appropriately selected and used.

These adhesives are generally used in an amount of 5 to 50 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the pigment. In addition, various auxiliaries such as an antifoaming agent, a colorant, and a fluidity improver are appropriately used as needed.

The base paper used in the present invention is 30 to 20
Fine and medium papers with a typical neutral or acidic size of 0 g / m ² can be used. Roll coaters such as gate roll coaters, blade coaters, air knife coaters,
Base paper pre-coated by an on-machine or off-machine coater provided with a coating device such as a rod coater, a short dowel coater, a reverse roll coater, a size press coater, or a gravure coater can also be used.

The coating liquid composition may be used in the production of general coated paper, for example, a roll coater such as a gate roll coater, a blade coater, an air knife coater, a rod coater, a short dowel coater, a reverse roll coater, a size press coater, It is coated on the base paper in one or more layers by an on-machine or off-machine coater provided with a coating device such as a gravure coater, and the coating (drying) speed is generally from a low speed to a high speed coater of 1500 m / min. Used for coaters. The solid content concentration of the coating liquid composition at that time is generally 40 to 75% by weight, but preferably in the range of 45 to 70% by weight in consideration of the operability of an actual machine.

Conventionally, a method of drying a wet coated paper obtained by applying a coating liquid containing a pigment and an adhesive as a main component to a base paper is as follows.
Hot air dryer, gas IR dryer, electric IR dryer,
There is a cylinder dryer and the like, and the method of adjusting the moisture of the coated paper is generally a method of controlling the amount of hot air and the temperature of the hot air dryer.

According to the method of the present invention, a signal is inputted from a dew point detecting device provided in each hot air dryer unit, and the amount of steam blown into each hot air circulation system and the amount of fresh air introduced are adjusted to obtain the hot air. Control the dew point temperature in the dryer to an appropriate range. In addition, a signal is input from a temperature detection device provided in each hot air dryer unit, the steam amount of the heat exchanger for adjusting hot air temperature is adjusted, and the hot air temperature is also controlled to an appropriate range. This is a method for drying paper.

[0019]

[Function] In the drying with the hot air dryer, when the moisture management of the coated paper is performed by adjusting the hot air temperature and the air volume by a conventional method, the change in the evaporation amount of the moisture changes the steam partial pressure of the hot air. The dew point temperature in the hot air dryer changes,
The temperature at which the moisture in the coating layer evaporates varies, and the film formation state of latex or the like as an adhesive changes, often affecting print strength and print mottling.

According to the method of the present invention, by controlling the dew point temperature and the hot air temperature in appropriate ranges, the adhesive is dried at a high film forming temperature, so that the film forming property is stabilized and the printing strength is increased. Guessed. The effect of reducing the occurrence of print mottling is presumed as follows. Due to the formation unevenness inherent in the base paper, the coated paper has a thickness unevenness in the coating layer, and the tendency increases as the speed of the paper machine or the coating machine increases. Drying unevenness and binder migration based on unevenness in thickness of the coating layer caused by fluctuations in the base paper moisture, coating liquid concentration, coating amount, hot air temperature, outside air temperature, etc., or changes in coating (drying) speed, are appropriate. It is alleviated under the environment of the dew point temperature, and the occurrence of printing mottling is suppressed.

[0021] The method of the present invention may be applied to lightly coated paper, medium coated paper,
Gloss type of lightweight coated paper, high quality coated paper, art paper, etc.
The present invention provides a drying method which is effective for a method for drying a mat-type or dull-type printing coated paper and can stably obtain a coated paper which has high printing strength and does not cause mottling during printing.

The method for evaluating print quality in the present invention is as follows.

Print strength: The RI print strength was visually evaluated after printing the TV-24 ink with an RI-II type printability tester (manufactured by Akira Seisakusho). IGT strength is IG according to JIS P8129 method.
Evaluation using a T printability tester.

Printing mottling: The mottling is a visual evaluation of ink density unevenness after two-color printing using an RI-II type printing suitability tester (manufactured by Meiji Seisakusho). The standard deviation of the ink density is the standard deviation of the absorbance (measurement wavelength: 570 nm) measured by a two-wavelength chromato-scanner CS-9000 (Shimadzu Corporation) after two-color printing with an RI-II type printability tester (manufactured by Mei Seisakusho).
Measurement area 2cm ²・ Number of measurement points 500 ・ Absorbance 0.6 ~ 0.8
Measure printed paper in the range. The absorbance is adjusted at the ink amount or at the printing interval of the first color printing and the second color printing).

[0025]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the scope of these examples.

The dew point control method, which is one of the features of the present invention, will be described with reference to the coating apparatus shown in FIG. 1. A base paper (1) supplied from a paper feeding section A is composed of a fountain (2) and a backing roll (3). In a coating apparatus in which a coating liquid is applied in a coating section B composed of a hot air dryer section C and a reel D, the wet coated paper is dried in a hot air dryer section C and wound in a coating section B. The hot air of the hot air dryer that dries the coated paper uses the dew point detected by the dew point temperature detecting device (5) provided in the hot air dryer, and the steam opening degree adjuster (for hot air) (6) and the fresh air adjuster (7) is adjusted to adjust the dew point temperature of the hot air supplied from the hot air fan (8). At the same time, the steam opening controller (for heat exchanger) (10) is adjusted by the hot air temperature detected by the temperature detecting device (9) provided in the hot air dryer to reduce the amount of steam entering the heat exchanger (11). Decide and adjust the hot air temperature. In order to adjust the evaporation rate of the moisture to an appropriate value, the moisture control is performed by adjusting the rotation speed of the air supply damper opening degree adjusting device (12) or the hot air fan (8) to change the wind speed of the hot air. Further, the method of drying the coating apparatus is not limited to drying using only a hot-air dryer, and an effect can be obtained by a combination selected from a hot-air dryer, a cylinder dryer, an electric IR dryer, a gas IR dryer, and the like. Regarding the drying method in the examples and comparative examples, the results of the case of using only the hot air dryer and the results of the combination of the hot air dryer and the cylinder dryer are described.

(Example 1) The coating liquid composition was as follows: 60 parts of kaolin (trade name: manufactured by Premier Kaolin ECC), 40 parts of calcium carbonate (trade name: Carbital 90, manufactured by Fuji Kaolin Co.), and a pigment dispersant ( Product Name: Aron T-40
0.4 parts of Toa Gosei Chemical Industry Co., Ltd., and styrene / butadiene copolymer latex (trade name: JSR0625)
13 parts by Nippon Synthetic Rubber Co., Ltd., oxidized starch (trade name: MS46)
00 Nippon Shokuhin Co., Ltd.), an appropriate amount of an antifoaming agent and a fluidity improver were blended, and a coating liquid having a solid content of 62% was used.
The coating (drying) speed was 5 m / min, the coating amount was 15 g / m ² , and drying conditions were hot air temperature of 140 ° C., dew point temperature of 45 ° C., and hot air dryer. Perform super calendar treatment on the obtained coated paper under certain conditions,
Table 1 shows the results obtained by the evaluation method described above.

Example 2 A coated paper for printing was obtained in the same manner as in Example 1 except that the drying conditions were changed to a dew point of 55 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 A coated paper for printing was obtained in the same manner as in Example 1, except that the drying conditions were changed to a dew point of 40 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

(Comparative Example 2) A coated paper for printing was obtained in the same manner as in Example 1, except that the drying conditions were changed to a dew point temperature of 60 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 A coated paper for printing was obtained in the same manner as in Example 1 except that the drying conditions were changed to a hot air temperature of 180 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 A coated paper for printing was obtained in the same manner as in Example 3, except that the drying conditions were changed to a dew point of 50 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 3 A coated paper for printing was obtained in the same manner as in Example 3, except that the drying conditions were changed to a dew point of 40 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 4 A coated paper for printing was obtained in the same manner as in Example 3, except that the drying conditions were changed to a dew point of 57 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0035]

[Table 1]

The evaluation criteria are as follows. ◎: extremely good, ○: good, Δ: slightly bad, ×: bad

Example 5 A coated paper for printing was obtained in the same manner as in Example 1 except that the coating (drying) speed was 150 m / min and the drying conditions were a hot air temperature of 100 ° C. and a dew point temperature of 50 ° C. .
The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Example 6 A coated paper for printing was obtained in the same manner as in Example 5, except that the drying conditions were a hot air temperature of 120 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Example 7 A coated paper for printing was obtained in the same manner as in Example 5, except that the drying condition was a hot air temperature of 160 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 5 A coated paper for printing was obtained in the same manner as in Example 5, except that the drying conditions were a hot air temperature of 80 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 6 A coated paper for printing was obtained in the same manner as in Example 5, except that the drying conditions were a hot air temperature of 200 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

[0042]

[Table 2]

The evaluation criteria are as follows. ◎: extremely good, ○: good, Δ: slightly bad, ×: bad

Example 8 The procedure of Example 1 was repeated except that the coating (drying) speed was 900 m / min, the drying conditions were a hot air temperature of 160 ° C., a dew point temperature of 45 ° C., and drying using a hot air dryer and a cylinder dryer. A coated paper for printing was obtained. The obtained coated paper was evaluated in the same manner as in Example 1,
The results are shown in Table 3.

Example 9 A coated paper for printing was obtained in the same manner as in Example 8, except that the drying conditions were a dew point of 55 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 3.

Comparative Example 7 A coated paper for printing was obtained in the same manner as in Example 8, except that the drying conditions were changed to a dew point of 40 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 3.

(Comparative Example 8) A coated paper for printing was obtained in the same manner as in Example 8, except that the drying conditions were a dew point temperature of 60 ° C. The obtained coated paper was evaluated in the same manner as in Example 1, and the results are shown in Table 3.

[0048]

[Table 3]

The evaluation criteria are as follows. ◎: extremely good, ○: good, Δ: slightly bad, ×: bad

As can be seen from the above results, all of Examples 1 to 9 of the present invention have high printing strength and excellent mottling. In contrast, Comparative Examples 1 to 8 are inferior in either or both of the printing strength and the mottling property.

[Brief description of the drawings]

FIG. 1 is a schematic view of a coating apparatus used in Examples and Comparative Examples of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base paper 2 Fountain 3 Backing roll 4 Blade 5 Dew point temperature detector 6 Steam opening controller (for hot air) 7 Fresh air controller 8 Hot air fan 9 Temperature detector 10 Steam opening controller (for heat exchanger) 11 Heat exchange 12 Air supply damper opening adjustment device

Continuation of front page (56) References JP-A-3-269192 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 23/00 F26B 21/10

Claims (3)

(57) [Claims] 1. A method for drying a coated paper in which a coating liquid containing a pigment and an adhesive as a main component is applied to base paper and drying in a drying step is performed by hot air, wherein a dew point temperature of hot air and a hot air temperature are determined by a hot air dryer. By inputting signals from the detectors in the unit and adjusting the amount of steam blown into each hot air circulation system, the amount of fresh air introduced, and the amount of steam in the heat exchanger for hot air temperature adjustment, the dew point temperature of hot air can be adjusted to 45 to A method of drying coated paper for printing having good printing strength and printing mottling, wherein the temperature is 55 ° C. and the temperature of hot air is 100 to 180 ° C. 2. The printing strength of the printing coated paper is JIS P8.
129 method using IGT printability tester 1
The method for drying a coated paper for printing according to claim 1, which is at least 40 cm / s. 3. The method for drying coated paper for printing according to claim 1, wherein the standard deviation of the ink density of the coated paper for printing after printing is 0.035 or less.