JPH0122399B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing coated paper, in which a coating liquid with a high solid content concentration containing specified kaolin and heavy calcium carbonate as pigments,
The present invention relates to a method for producing coated paper, which is characterized by coating by a specific coating method. In the method of manufacturing coated paper, which involves applying a coating liquid containing pigments and adhesives onto a base paper and drying it, a coating liquid with a high solid content concentration of 63 to 80 wt% is used. The blade coating method allows the coating liquid layer to dry quickly, which not only saves equipment, energy, and expenses required for drying, but also allows the coating liquid layer to dry quickly before moving along the uneven surface of the base paper. It has the advantage of imparting excellent gloss and smoothness to coated paper. However, various technical problems associated with coating and defects in the quality of the resulting coated paper have not yet been solved, and coating solutions with such high solids concentrations have not been applied on an industrial scale. The reality is that it is almost never implemented. For example, 63wt% or more, more preferably 65wt%
In order to obtain a coating liquid with a high solid content concentration, conventionally,
Simply increasing the solid content concentration of a coating liquid used for paper coating will result in a coating liquid with increased viscosity, poor high shear fluidity, and reduced water retention.
Therefore, it is easy to cause streak problems such as streaks and stalactite during coating. A method of using heavy calcium carbonate, which has a relatively large average particle size, as a pigment in order to improve coating suitability.
-43244) and a method in which fine grained heavy calcium carbonate with a controlled particle size distribution is used solely as a pigment component (Japanese Unexamined Patent Publication No. 1983-62296), but none of these methods improve coating suitability. An accompanying drawback is that the gloss and smoothness of the coated paper obtained are reduced. Furthermore, in the blade coater commonly used today, in addition to the above-mentioned suitability for coating a coating liquid with a high solid content concentration, the following problems are also involved. In other words, in the case of a trailing blade method that has a flattened nip type roll applicator mechanism or a fountain applicator mechanism, the coating amount is too large, making it difficult to control with the blade's pressure mechanism, and moreover, it is difficult to control the coating uniformly. It is extremely difficult to obtain a sufficient coating amount. If the blade pressure is increased to control the coating amount, the coated surface will become rough and the smoothness will deteriorate. In addition, paper breaks easily occur, and operability deteriorates. After supplying excess coating liquid to the base paper, it takes a long time to scrape off the excess coating liquid (e.g., 0.024 seconds when using a Beloit Co., Ltd. Fradetsu nip coater at a coater speed of 1000 m/min). The penetration of the coating liquid from the coating liquid layer into the base paper progresses, and combined with the high concentration, the water retention capacity of the coating liquid layer decreases due to dehydration, resulting in gelation and leveling of the coating liquid layer. cause defects. This not only makes the coated surface non-uniform, but also tends to cause streak troubles such as streaks and stalactite. In addition, pound-type paddle coaters have a poor self-cleaning effect on the coating liquid scraped off by the blade, so streaks and stalactite are likely to occur, making them unsuitable for coating high solids concentration coating liquids. Moreover, it has the disadvantage of poor operability when running out of paper. In view of the current situation, the present inventors conducted extensive research to eliminate the above-mentioned drawbacks pointed out in high solids concentration coating liquids and coating methods, and as a result, the present inventors developed kaolin and heavy carbonate having a specified particle size. By using calcium as a pigment, the coating suitability of the coating liquid is improved, and the time required to scrape off the excess coating liquid after supplying excess coating liquid to the base paper is shortened. By combining the specific coating methods described above, we have discovered a method for producing coated paper that enables the coating of a coating liquid with a high solid content concentration and that also provides coated paper of high quality. The present invention provides a method for producing coated paper by coating a base paper with a coating liquid containing a pigment and an adhesive and having a high solid content concentration. Kaolin with a content of 50wt% or more is 10-80wt% of the total pigment, and the particle content of 2 μm or less is 70-80wt% of the total pigment.
100wt%, particle content of 1μm or less is 55-95wt%
20~90wt of total pigment is heavy calcium carbonate
% and has a solid content concentration of 63 to 80 wt%, is supplied to the base paper in excess by the application mechanism of the (b) blade coater, and then the excess is removed by the blade mechanism within 0.0005 to 0.015 seconds. This is a method for producing coated paper characterized by scraping off the coating liquid. Kaolin, which is used as a pigment component in the coating liquid used in the present invention, is a component that mainly contributes to the gloss and smoothness of the coated paper, and it contains particles with a particle content of 1 μm or less. Kaolin with a content of 50 wt% or more is used. The amount of kaolin used can range from 10 to 80 wt% of the total pigment. If it is less than 10 wt%, it will not be possible to impart sufficient gloss and smoothness to the coated paper, and if it exceeds 80 wt%, it will not be possible to impart sufficient gloss and smoothness to the coated paper. The coating suitability of the liquid to be applied deteriorates. Heavy calcium carbonate, which is used as a pigment component together with the above-mentioned kaolin, is a component that mainly contributes to the coating suitability of the coating liquid. However, as in the above-mentioned Japanese Patent Publication No. 46-43244, using too coarse heavy calcium carbonate not only tends to cause problems with streaks and scratches during coating, but also reduces the gloss and smoothness of the white paper. Furthermore, since the ink gloss after printing also decreases, the present invention uses 2μ
Particle content below m is 70-100wt%, preferably
80-100wt%, and the particle content of 1μm or less is 55
~95 wt%, preferably 60-95 wt% of finely ground calcium carbonate is used. The amount of heavy calcium carbonate used is in the range of 20 to 90 wt% of the total pigment. If it is less than 20 wt%, the high shear viscosity of the coating liquid will increase and trouble will occur during coating, and if it exceeds 90 wt%, The photoselectivity and smoothness of the coated paper deteriorate, and the gloss of the ink after printing also decreases. The pigment components in the coating liquid used in the present invention are mainly composed of the above-mentioned kaolin and heavy calcium carbonate, but other pigment components may be added as necessary, such as light calcium carbonate, satin white, titanium dioxide, and pyrocarbonate. Fiberite clay, calcium sulfite, calcium sulfate, aluminum hydroxide, zinc oxide, talc, zeolite, barium sulfate, amorphous silica, plastic pigment, and the like can also be blended. However, their blending amount should be limited to 50 wt% or less of the total pigments, and is generally preferably 20 wt% or less. In the coating liquid used in the present invention, adhesive components include styrene-butadiene, styrene-acrylic, vinyl acetate-acrylic, and ethylene-butadiene.
Various copolymers such as vinyl acetate, butadiene-methyl methacrylate, and vinyl acetate-butyl acrylate, and alkali-sensitive or alkali-insensitive adhesives such as polyvinyl acetate, as well as polyvinyl alcohol, maleic anhydride-styrene, etc. Synthetic adhesives such as polymers, isobutene-maleic anhydride copolymers, acrylic acid-methyl methacrylate copolymers, oxidized starches, etherified starches, esterified starches, oxygen-modified starches, and flat-dried them. Generally known adhesives such as natural adhesives such as cold-water soluble starch, casein, and soybean protein can be used, but coating liquids with a high solids concentration of 63 wt% or more and good rheological properties can be used. In order to obtain this, it is preferable to use the copolymer latex alone or in combination with cold water-soluble starch, and it is desirable to keep the total amount of adhesive used within the range of 3 to 20 wt% based on the pigment. It is also preferable to minimize the amount of adhesives that tend to thicken, such as other natural adhesives. In addition, dispersants, thickeners, water retention agents, antifoaming agents, waterproofing agents, lubricants,
Various auxiliary agents such as dyes and PH regulators can be added as appropriate. The coating liquid obtained in this way has a solid content concentration of 63 to 80 wt%, preferably 65 to 80%, by using a specific kaolin and heavy calcium carbonate as pigments.
It can be adjusted to 80wt%, and has low viscosity and good high shear fluidity, making it highly suitable for application with a blade coater. In the method of the present invention, such a specific coating liquid with a high solid content concentration is combined with a specific coating method, and this specific coating method is a combination of coating liquid with a high solids concentration and a specific coating method. 15-30 of the desired coating amount
After supplying excess coating liquid, preferably about 10 to 20 times, the time required to scrape off the excess coating liquid is 0.0005 to 0.015 seconds, more preferably 0.001 to 0.01 seconds.
This is a coating method that is extremely short, taking just seconds. In general, such a coating method requires that the distance from the applicator mechanism that transfers the coating liquid to the base paper to the blade mechanism that scrapes off excess coating liquid range from about 0.5 to 16 cm, preferably from 0.5 to 12 cm, and most preferably from about 0.5 to 12 cm. is 0.5~
This is achieved by adjusting the range to 7 cm. Note that if a high solids concentration coating liquid is scraped off with a blade after 0.015 seconds or more has elapsed, streak problems such as streaks and stalactite are likely to occur. Furthermore, the condition shorter than 0.0005 seconds means that the coater speed is 3000 m/min or more, and stable operation is currently difficult. The coater speed at which a preferable effect can be obtained by applying the method of the present invention is 100 to 2000 m/min, more preferably 100 m/min.
~1500m/min. One type of coating method that can be preferably used in the present invention is described in JP-A-57-84770, in which coating liquids with a solid content concentration of 60 wt% or less are used, which is relatively Only techniques relating to lightweight coatings are disclosed. However, in the method of the present invention, a specific coating liquid having excellent rheological properties as described above is combined with the coating method, thereby achieving a concentration of 63 wt% or more, preferably 65 to 80 wt%. It is possible to stably coat one or both sides of a base paper with a low blade pressure using any blade such as a bevel type or bent type with a coating liquid having a high solid content concentration. Furthermore, the amount of coating per side can be adjusted over a wide range of 3 to 30 g/m ² in terms of dry weight. However, if the coating amount is less than 6g/ ^m2 , the resulting coated paper will have insufficient gloss, smoothness, and ink gloss after printing, while if it exceeds 30g/ ^m2 , streaks such as streaks and scratches will occur. In the present invention, the coating amount is set at 6 to 30%.
g/m ² , preferably within the range of 8 to 20 g/m ² , and not only single coating but also double coating is of course possible. In addition, as the base paper, generally used is a medium-quality base paper for coating made using acidic or neutral paper using high-yield pulp or mechanical pulp, or high-quality base paper for coating using bleached pulp. Thus, according to the method of the present invention, the technical problems observed in the conventional high solids concentration coating liquid coating are effectively improved, and selective absorption of the coating liquid and coating amount unevenness are reduced, and coating is possible. It is easier to adjust the profile of the work load, a uniform coating layer is formed, and the coated paper properties expected by coating with a high solids concentration coating liquid, such as white paper gloss, smoothness, and after printing, are improved. The gloss of the ink is significantly improved. Furthermore, according to the method of the present invention, the water retention property of the coating liquid, which was conventionally required, is not required so much, and the decrease in the water retention property of the coating liquid layer after being coated on the base paper is minimized. Because coating can be performed with low blade pressure without loss of fluidity, streak problems such as streaks, stalactite, and scratches, as well as paper breakage, are reduced, and coating operability is significantly improved. It is something. Of course, the savings in drying equipment and energy costs that can be achieved by coating with a high solid content concentration are a natural effect. The coated paper obtained by the method of the present invention exhibits the excellent characteristics of the present invention significantly when it is made into a product through finishing equipment such as a super calender or a gloss calender. It can also be used as coated matte paper without treatment. Any of offset printing, gravure printing, letterpress printing, and flexo printing can be used as the printing method for coated paper, and either sheet or roll printing can be used. The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples. Note that parts and percentages shown in the examples mean parts by weight and percentages by weight unless otherwise specified. Examples 1 to 8, Comparative Examples 4 to 8 0.3 parts of rosin size and 15 parts of papermaking talc were added to the pulp composition consisting of 20 parts of NBKP and 80 parts of LBKP, and the papermaking pH was adjusted to 4.5 with sulfuric acid band to make fourdrinier paper. Paper is made using a machine, and oxidized modified starch is added to 1.5% on both sides.
Perform size press treatment to adhere to g/ ^m2 ,
A base paper for coated paper having a weight of 55 g/m ² was obtained. Using a Coles disperser, pigments as listed in the table,
Add 0.2 parts of sodium polyacrylate as a dispersant and 0.3 parts of calcium stearate as a lubricant to a coating liquid composition consisting of an adhesive and an auxiliary agent, mix and disperse,
A coating solution was prepared with the properties listed in the table. These coating liquids were applied to the above base paper using a short dwell blade coater in Examples 1 to 7, Comparative Examples 4 to 8 at 15 g/m ² on one side, 30 g/m ² on both sides, and Example 8 on one side. Both sides were coated so that the weight was 8 g/m ² and the weight was 16 g/m ² on both sides. At this time, the coater speed of Example 2 was 300 m/min, Examples 1, 3, 5 to 8,
The coater speed of Comparative Examples 4 to 8 was 900 m/min, and the coater speed of Example 4 was 1400 m/min. The dwell time (described as dwell time in the table) was as described in the table. The obtained coated paper was subjected to super calendering to produce coated processed paper. The coating operability, the blank paper of the coated paper and the quality after printing were as shown in the table. Comparative Examples 1 to 3 Using the same base paper and the same coating preparation method as in Examples 1 to 8 and Comparative Examples 4 to 8, coating liquids having properties as described in the table were obtained. Next, the paper was coated on both sides using a flattened nip blade coater at a coating weight of 15 g/m ² on one side and 30 g/m ² on both sides, and then subjected to super calendering to produce a coated paper. At this time, the coater speed of Comparative Example 1 was 300 m/min.
Further, the coater speed of Comparative Examples 2 and 3 was 900 m/min, and the respective dwell times were as shown in the table. The coating operability, the quality of the coated paper and the quality after printing were as shown in the table. Example 9, Comparative Example 9 Pulp composition from 50 parts of SGP and 50 parts of NBKP,
Add 0.2 parts of rosin size and 20 parts of talc for paper making,
The pH of the paper was adjusted to 4.5 using sulfuric acid band, and paper was made using a Fourdrinier paper machine to obtain base paper for coated processed paper with a weight of 40 g/m ² . Next, coating liquids having the properties shown in the table were obtained by the same coating preparation method as in Examples 1 to 8 and Comparative Examples 1 to 8. These coating liquids were coated on both sides of the above base paper using a short dwell blade coater at a coating density of 15 g/m ² on one side and 30 g/m ² on both sides, followed by super calendering and coating processing. produced paper. The coater speed at this time was 900 m/min.
Dwell time was as listed in the table. The coating operability, the white paper of the coated paper and the quality after gravure printing were as shown in the table. As is clear from the above examples, the method for producing coated paper of the present invention has been improved to fully utilize the advantages of high solids concentration coating, and the rheological properties of the coating liquid and the coating operation The obtained coated processed paper was excellent in white paper gloss and smoothness, and was also excellent in quality after offset printing and gravure printing.

【table】

[Table] Description of coating liquid raw materials used in Examples and Comparative Examples The kaolin used in Examples 1 to 5, 7, and 8 and Comparative Examples 1 to 5, and 7 was manufactured under the trade name Amazon 88 (The
Caulim da Amazonia Ltda.). The kaolin used in Example 6 has the trade name HT.
(Manufactured by EMC). The kaolin used in Example 9 and Comparative Example 9 was under the trade name Ultra White 90 (manufactured by EMC). The kaolin used in Comparative Example 6 is the trade name
Klondyke (manufactured by EMC). Examples 1-6, 8, 9, Comparative Examples 1-6, 8, 9
The heavy calcium carbonate used was the product name Carbital 90 (manufactured by Fuji Kaolin Co., Ltd.). The heavy calcium carbonate used in Example 7 was obtained by slurrying the product name Softon 1800 (manufactured by Bihoku Funka Kogyo Co., Ltd.) using 0.4 parts of sodium polyacrylate as a dispersant, and then milling it in a sand mill manufactured by Dreiswerke, Germany. (Pearl Mill). The heavy calcium carbonate used in Comparative Example 7 had the trade name Softon 1800. Latex A used in Examples 1 to 8 and Comparative Examples 1 to 8 was a styrene-butadiene copolymer latex brand name SN307 (manufactured by Sumitomo Naugatak Co., Ltd.). The latex B used in Example 9 and Comparative Example 9 was an alkali-thickened styrene-butadiene-butyl acrylate-methyl methacrylate copolymer latex trade name L-1953 (manufactured by Asahi Dow Co., Ltd.). Examples 1-4, 6-8, Comparative Examples 1-3, 6-8
The starch A used in is the product name Hi-Coaster PC11.
(manufactured by Sanwa Starch Co., Ltd.). Starch B used in Comparative Example 4 has the trade name Ace A.
(manufactured by Oji Cornstarch Company). Notes in the table Note 1 Particle size distribution: Measured using Sedaygraph Model 5000-01 (manufactured by Shimadzu Corporation) and expressed in percentage (%). Note 2 Type B viscosity: The viscosity value measured at 60 rpm on the No. 1 spindle of a Bruckfield viscometer in centipoise (cps). Note 3 High shear viscosity: Bob E, determined by Hercules high shear viscometer (manufactured by Kumagai Riki Kogyo)
The viscosity value at 8000 rpm, that is, 8.4×10 ⁴ sec ^-1 is expressed in poise (cps). Note 4 Coating operability: streaks, scratches,
The evaluation was based on the streak defects of stalactite and the uniformity of the coated surface. (Good ◎ 〇 △ × (unoperable) Note 5 White paper gloss: measured by on-board gloss meter
The measured value at 75°/75° is shown in %. Note 6 Blank paper smoothness: Visually evaluated. (Good) ◎ 〇 △ × (Poor) Note 7 Print gloss: After printing with 0.3 cc of black ink using an RI type printing tester manufactured by Mei Seisakusho, the measured value of gloss is shown in % as in Note 5. Note 8 Gravure suitability: Halftone dot reproducibility after printing was visually evaluated using a gravure printing tester manufactured by Kumagai Riki Kogyo. (Good) ◎ 〇 △ × (Poor)

Claims (1)

[Claims] 1. In a method of manufacturing coated paper by coating a base paper with a high solids concentration coating liquid containing pigments and adhesives, (a) the content of particles of 1 μm or less as pigments is 50w%; Kaolin is more than 10% of the total pigment
80w%, particle content of 2μm or less is 70-100w%,
A coating liquid containing 20 to 90 w% of the total pigment, with a particle content of 55 to 95 w% of particles of 1 μm or less, and a solid content concentration of 63 to 80 w%, is applied to (b) a blade coater. A method for producing coated paper, which comprises supplying excess coating liquid to the base paper using an applicator mechanism and then scraping off excess coating liquid using a blade mechanism within 0.0005 to 0.015 seconds.