JPH0625992A - Production of base paper for printing coated paper - Google Patents

Abstract

PURPOSE:To obtain base paper for printing coated paper free from unevenness of density and excellent in smoothness and cushion property in the thickness direction. CONSTITUTION:The objective base paper for printing coated paper is obtained by subjecting base paper having 5-8wt.% water content to surface treatment with a calender device consisting of a metallic roll and an elastic roll having 65-98 Shore hardness. Thereby, coated paper excellent in both of inking properties of gravure printing ink and acceptability of offset printing ink is provided.

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 base paper for a coated paper for printing, and more specifically, it produces a coated paper for printing excellent in printability in offset printing and ink receptivity in gravure printing. The present invention relates to a method for manufacturing a base paper for manufacturing.

[0002]

2. Description of the Related Art In recent years, the importance of printed matter has been re-recognized as a medium for publishing, advertising, publicity, etc.
Colorization and high quality are being promoted, and along with this, coated paper, for example coated paper (single-sided coating amount: 10 to 20 g / m
^2), art paper (single-sided coating amount 20-25 g / m ^2), a cast coated paper (single-sided coating amount 25 g / m ² or more), medium-quality paper, Binurikoshi (single-sided coating amount 15 g / m ² The following) and other pigment-coated papers are in great demand, and their applications are widespread.

[0003] Recent publications are often subjected to offset printing or gravure printing, which has an excellent printing effect such as multicolor printing. Offset printing does not print directly on the paper from the plate,
Once transferred to a rubber surface called a blanket, printed from blanket on paper, and then dried at high temperature to produce printing paper, but ink adheres to the image area and wets (squeezes) and water on other areas. Adhesion is a major feature.

In the offset printing, ink and dampening water are sequentially printed on the coated paper surface according to the color of the image area. At this time, if there is uneven ink absorption on the coated paper surface, printing unevenness, that is, "mottling" occurs. It is known to significantly reduce the value of printed paper.

The methods generally used for improving the mottling of coated papers are a method for improving the texture of the coated paper and a method for increasing the coating amount. In addition, various printability-improving agents for various coated papers are used. Method used (Japanese Patent Laid-Open No. 61-123633)
JP-A-60-185892, JP-A-61
-55286, Japanese Patent Application Laid-Open No. 3-199492), and a method for specifying a pigment constituting a coating liquid (Japanese Patent Application Laid-Open No. 3-1993).
-197318) is disclosed.

The texture of coated papers can be improved to some extent by selecting operating conditions in the papermaking process, especially in the wet part, and by the use of texture improvers (pulp dispersants), but not at a satisfactory texture level. Is the actual situation.

Although the method of increasing the coating amount of the coated paper has a great effect of improving the Mott rig, it is hard to say that it is a preferable method because the cost for producing the coated paper increases. Further, the method of adding a chemical to the coating liquid and the method of identifying the pigment constituting the coating liquid in order to improve the printability of the coated paper are not unavoidable to cause a cost increase to some extent. It is difficult to obtain a product that can fully satisfy the high-level requirements for coated paper quality in recent years.

On the other hand, gravure printing is a photomechanical process in which a recess is directly formed on the plate cylinder to apply ink to the entire plate, and then a doctor is used to scrape off the ink other than the image areas, and the ink in the recess is smoothly and Transfer evenly. Therefore, it is necessary that the surface of the paper is smooth, and if there is unevenness on the entire paper and there are places that come into contact with the ink, and there are places that do not come into contact with it, beautiful gravure printing cannot be performed. Therefore, of the qualities required for gravure printing paper, smoothness is the most important.

Further, smoothness is required from another point of view. That is, since gravure printing is performed under strong printing pressure as compared with other printing, smoothness in a compressed state is important. When the paper surface receives uniform pressure in the thickness direction, it does not dent uniformly, and if unevenness occurs, beautiful gravure printing cannot be performed.

Therefore, in order to improve the cushioning property in the thickness direction, use of high ash content base paper in the coated paper for gravure printing,
Method using high-yield pulp (Japanese Patent Laid-Open No. 63-2748)
No. 0), reduction of latex and natural polymer binder, reduction of Tg of latex to cope with blending, and soft calendering of coated paper (Japanese Patent Laid-Open No. HEI 3)
No. 234895), a base paper is provided with an undercoating pigment coating layer, and then a soft calendering treatment is carried out (Japanese Patent Laid-Open No. Hei 2
No. 234998) has been proposed, but it is difficult to say that any of them is a method for producing a coated paper having satisfactory gravure printing suitability.

[0011]

DISCLOSURE OF THE INVENTION According to the present invention, by subjecting a coated base paper to a surface treatment with a soft calender, the density unevenness is smaller than ever before, the paper has excellent cushioning properties in the thickness direction, and printing is excellent in smoothness. It is an object of the present invention to provide a method for producing a base paper for coated paper for use in the production.

[0012]

In view of the above-mentioned present situation, the present inventors have conducted a study in which the type and composition of the pigment adhesive and the printability improving agent that make up the coating liquid are changed, and the coated paper As a result of studying the printability in offset printing and gravure printing by changing the physical properties of the coated paper, in order to improve the Mott rig while maintaining the various qualities required for the coated paper for offset printing, it is necessary to use a small plane direction of the coated base paper. In order to reduce the density unevenness of the coated paper and to smooth the coated paper while maintaining the cushioning property in the thickness direction, which has the greatest effect on the ink receptivity of the coated paper for gravure printing, one coated base paper is used. It was found that it is indispensable to carry out the surface treatment with a calendering device composed of the metal roll of the above and one elastic roll, and the present invention has been completed.

The present invention provides a printing coated paper obtained by coating a coating base paper with a coating liquid containing a pigment and an adhesive as main components.
Book metal roll and Shore D hardness (ASTM standard D22
40) is a calender device consisting of one elastic roll in the range of 65 to 98 degrees, characterized in that the base paper of the printing coated paper, the moisture content of which is adjusted to 5 to 8% by weight, is surface-treated. The present invention relates to a method for producing a base paper for coated paper for printing.

It is already well known that the printability including the smoothness is the most important quality of the coated paper for printing.
The higher the smoothness of the coated base paper is, the higher the smoothness of the coated paper is. Therefore, the coated base paper is surface-treated to such an extent that the deterioration of the quality due to the decrease of the opacity does not occur and the smoothness is improved.

A commonly used smoothing device is a machine calendar. The machine calendar consists of multiple mirror-finished metal rolls with a linear pressure of 1-50.
Normal smoothing conditions are kg / cm and a roll surface temperature of 40 to 90 ° C. Such a machine calender device has been described in detail in many documents, and is described in detail, for example, in the Paper and Pulp Technology Association, published on March 25, 1991, "Papermaking", pages 376-427. ing. It is known that the paper surface-treated with a machine calender generally has a relatively high smoothness, but the paper tends to be compressed in the thickness direction and crushed to lower the opacity.

The present inventor has found that any coated base paper has small irregularities having a period of about 0.5 mm, large wavy irregularities having a period of about 5 mm, and, in some cases, wavy irregularities having a period of several cm. Discover what is happening. When such a coated base paper is smoothed by a machine calender, the density (g / cc) of the concave portions does not change significantly, but the density of the convex portions becomes extremely high, and the density unevenness in the plane direction of the paper increases. A coated paper produced from such a coated base paper is inferior in printability and is likely to cause mottling. Further, since the cushioning property varies in the thickness direction, the ink receptivity of the gravure printing ink deteriorates.

The soft calender is a device which combines a metal roll and an elastic roll and pressurizes the paper surface with a small nip number of 1 or more. Not only is the paper crushed less but the smoothness is easily improved.

In the present invention, the coating amount is 5 to 20 g / m per one side.
Effective in improving the mottling of coated paper in the range of ² (absolute dryness) and gravure printing ink inking. Coating amount is one side 2
When it exceeds 0 g / m ² , the thickness of the coating layer increases, so that the occurrence of mottling is extremely reduced and the ink receptivity of gravure printing is improved, and it is not necessary to use the technique of the present invention. Further, a coated paper having a coating amount of less than 5 g / m ^{2 on} one side is not only difficult to coat with a general coater because the coating amount is too small, but is out of the category of coated paper. Out of the spirit. The coating amount per one side in the present invention is preferably 6 to 18 g / m ² .

Depending on the quality design of the coated paper, the coated base paper is treated with a soft calender to adjust to an arbitrary smoothness (J.TAPPI No. 5) in the range of 10 to 120 seconds. 10
If it is less than a second, not only can it be achieved by smoothing the coated base paper using a machine calender, but the smoothness of the coated paper will not be sufficiently increased, causing deterioration in quality. If it exceeds 120 seconds, the crushing of the coated base paper in the thickness direction becomes large, so it is more preferably adjusted within the range of 15 to 110 seconds.

The smoothness of the coated base paper when smoothed by a machine calendar is at most about 45 seconds,
If the ratio of deinked waste paper pulp or high-yield pulp to the pulp that constitutes the coated base paper is large, it will only rise to about 30 seconds.

The water content before the coated base paper is treated with the soft calender is 5 to 8% by weight. If the content is less than 5% by weight, the coated base paper is less crushed in the thickness direction and less in the opacity, but the smoothness is low. It is not preferable because it is difficult to increase and the desired level is not reached. If it exceeds 8% by weight, the smoothness tends to increase, but the opacity of the coated base paper is greatly reduced and the quality of the coated paper is deteriorated. 5.2-
7.8 wt% is preferred.

The water content of the coated base paper is adjusted by combining a method of adjusting the degree of drying of the coated base paper after papermaking and a method of spraying steam on the coated base paper.

The elastic roll constituting the soft calender of the present invention has a Shore D hardness of 65 to 98 degrees. Elastic rolls of less than 65 degrees require excessive linear pressure to obtain sufficient smoothness, which may significantly shorten the life of the elastic body during operation, and elastic rolls of more than 98 degrees cause large crushing of the coated base paper. Since the decrease in opacity becomes large and the smoothness becomes difficult to increase, it is preferably 70 to 97.
It is a soft calender made of elastic rolls. The elastic roll is arbitrarily selected according to the quality design of the coated paper.

A chilled roll, an alloy chilled roll, a steel roll, and a hard chrome-plated metal roll on the roll surface are preferably used as the metal roll paired with the elastic body of the soft calender.

The pressure conditions for passing the coated base paper through a soft calender consisting of one metal roll and elastic roll are the hardness of the elastic roll used, the type of coated base paper,
It can be adjusted appropriately according to the processing conditions such as the paper passing speed and the number of nips, but it is difficult to obtain the desired effect when the linear pressure is lower than 20 kg / cm, and the heat generation of the elastic roll itself increases when it exceeds 400 kg / cm. Therefore, stable operation becomes difficult, and therefore it is preferable to adjust in the range of 20 to 400 kg / cm.

Further, the higher the surface temperature of the metal roll, the higher the smoothness of the coated base paper, but the opacity remarkably decreases. Therefore, the surface temperature of the metal roll is extremely important for the present invention, and the surface temperature of the metal roll is 90 ° C.
If it is lower, the desired effect is difficult to obtain, and if it exceeds 190 ° C., not only the life of the elastic roll is shortened but also the opacity of the base paper is remarkably reduced, so that the range is 90 to 190 ° C., more preferably 100 to 180 ° C. Is adjusted by.

For heating the metal roll, a method of using a medium such as electricity, steam, water or oil is appropriately selected and used.

When the coated base paper is passed through a soft calendar, the wire side and the felt side of the base paper are each placed on a metal roll.
A method of contacting more than once is preferable, but the number of times of contact is not particularly limited. In addition, the coated base paper for single-sided coated paper may have the coated paper side contacting the metal roll and passed one or more times, and the number of times is not particularly limited.

The on-machine type and the off-machine type can be preferably used as the soft calendar device. In the case of applying the coating solution by soft calendering according to the present invention, it is preferable to apply the coating solution to the surface which is in contact with a metal roll because the smoothness is further improved. In the case of coating both sides of the paper, it is preferable that the smoothness of both sides of the coated paper is further improved by passing the paper twice so that both sides are in contact with the metal roll and calendered.

The coated base paper used in the present invention is a bleached softwood kraft pulp (NBKP) or a bleached hardwood kraft pulp (LBKP) regardless of the type of pulp constituting the base paper.
Base paper, NBKP, LBKP, deinked waste paper pulp,
Any base paper, such as a base paper mixed with any of the high-yield pulps, is also suitable.

The papermaking method of the coated base paper of the present invention is not particularly limited, and a conventionally used papermaking method can be adopted. For example, an acidic papermaking process performed at a papermaking pH of about 4.5 or a so-called neutral papermaking process that includes an alkaline filler such as calcium carbonate as a main component and has a papermaking pH of about 6 to 9 and is weakly acidic to weakly alkaline is adopted. Good.

The coated base paper of the present invention can be made into a paper having a basis weight of about ²⁰ to 400 g / m ² depending on its use and purpose.

Further, in the papermaking of the coated base paper of the present invention, an internally added filler which has been conventionally generally used can be used if necessary. For example, talc, kaolin, clay, calcined kaolin, deramie kaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, aluminum hydroxide, titanium dioxide, magnesium silicate, magnesium sulfate, calcium sulfate, white carbon, aluminosilicate. , Silica, bentonite and other mineral fillers, polystyrene resin fine particles, urea formalin resin fine particles, micro hollow particles and other organic synthetic fillers (plastic pigments), one or more can be appropriately selected and used. Fillers contained in waste paper, plaque, etc. can also be used effectively.

In addition to these, various conventionally used anionic, cationic, nonionic or rigid retention aids, drainage improvers, paper-strengthening aids and other internal additive agents for papermaking. You may add suitably in a pulp slurry as needed. Examples of the internal additive for papermaking include sulfuric acid band, aluminum chloride, sodium aluminate and basic aluminum chloride, basic aluminum compounds such as basic polyaluminum hydroxide, and water-soluble aluminum such as alumina sol easily dispersible in water. Compounds or various starches such as cationized starch, polyacrylamide, polyethyleneimine, polyamine, polyamide / polyamine, polyethylene oxide, vegetable gum, urea formalin resin, melamine formalin resin, polyvinyl alcohol, latex, polyamide resin, hydrophilic crosslinked polymer Examples thereof include particle dispersions and the like, derivatives or modified products thereof, and compounds such as bentonite. Furthermore, a dye, a pH adjuster, a pitch control agent, a slime control agent, an antifoaming agent and the like can be added as necessary.

The coated paper for printing is produced by coating one or both sides of the coated base paper of the present invention with a coating liquid containing a pigment and an adhesive as main components. The coating composition generally has a solid content of 40 to 75% by weight, preferably 45 to 70% by weight.
Adjusted to a range of degrees.

In forming the coating layer by coating the coating liquid on the coating base paper, the coating layer may be formed by coating the coating liquid once, or may be divided into an undercoat layer and an overcoat layer. It may be formed as a multilayer structure. In the case of a multi-layer structure, the undercoat layer and the overcoat layer do not have to have the same coating liquid composition, and the coating liquid composition can be appropriately changed according to the required quality level.

As a method for forming a coating layer, a coating device which has been conventionally used, for example, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a per coater, a curtain coater, a die slot coater, a gravure coater, The coating liquid is applied to the surface of the coated base paper using various coaters such as a Chambrex coater, a brush coater, and a size press coater.
These coating devices may be used in either on-machine or off-machine coater form.

The coating amount of the coating liquid on the coated base paper is usually about ² to 50 g / m ^{2 on a} dry side, but it is 5 when the quality of the obtained coated paper and printability are taken into consideration. ~ 3
It is desirable to adjust in the range of about 0 g / m ² . Also,
The coated paper obtained in this way usually has a water content of 3
After drying so as to be in the range of about 10% by weight, the paper is passed through an on or off super calendar or the like for pressure finishing.

[0039]

EXAMPLES The present invention will be described in more detail below with reference to comparative examples and examples, but the present invention is not of course limited thereto. In the following, parts and% mean parts by weight and% by weight. The coated base paper made by the neutral paper making method in Comparative Examples and Examples has a basis weight of 55.0 g / m ^{2 and} a Steckigt sizing degree (according to JIS P 8122) of 1 to 1.
It was 4 seconds. The types of pulp used for this coated base paper are NBKP 10 parts and LBKP 90 parts.
Has a whiteness of 84.7% (Hunter whiteness, the same applies below) and freeness (CSF has the same meaning below) of 430 ml,
The LBKP had a whiteness of 85.3% and a freeness of 390 ml. Further, 10 parts of light calcium carbonate as a filler was added to 100 parts of pulp, and the following chemicals were further added (absolute dry weight of pulp) to produce a paper stock.

Alkenyl Succinic Anhydride Sizing Agent: 0.02% (Fibraso-81, Oji National Co., Ltd.) Cationized Starch: 0.5% (Kate F, Oji National Co., Ltd.) Acrylamite Yield improver: 0.03% (Himoloc NR11, manufactured by Haiku Co., Ltd.) Sulfuric acid band (homemade): 0.5%

A coated base paper was manufactured by using a fourdrinier multi-cylinder dryer paper machine using this paper material. In each of the examples and the comparative examples, the coating pressure of a super calender obtained by applying a coating solution having the composition shown below to a coated base paper with a blade coater and surface-treating with a super calender was kept constant at 200 kg / cm.

Kaolin average particle size 1.8 μm: 55 parts (HT kaolin, manufactured by Engelhard) Heavy calcium carbonate average particle size 2.3 μm: 45 parts (Escalon-2000, manufactured by Sankyo Milling Co.) Oxidized starch: 2 parts (Pigment) (Oji Ace A, Oji Constarch Co., Ltd.) SBR latex: 10 parts (Pigment) (Latex L-1795, Asahi Kasei Co., Ltd.) Acrylic acid dispersant: 0.1 part (Pigment) (Aron T-40, manufactured by Toagosei Co., Ltd.) The temperature on the surface of the metal roll of the soft calender was adjusted by adjusting the flow rate of steam fed to the metal roll.

Example 1 Water content of coated base paper was adjusted by adjusting papermaking conditions.
The content was adjusted to 1% by weight and passed through a soft calendar for surface treatment. The soft calendar is a metal roll (diameter 800 mm, trade name "Jacket roller", manufactured by Tokuden Co., Ltd.) arranged as a top roll, and a Shore D hardness 96 degree elastic roll (diameter 530 mm, arranged as a bottom roll).
The product name is “Eragrass ZE”, a heat-resistant thermosetting resin elastic film, manufactured by Kinyosha Co., Ltd.). The coated base paper was passed between the rolls of this soft calendar so that the wire surface of the coated base paper was in contact with the metal roll, and the paper was passed once at a passing speed of 400 m / min for surface treatment. The temperature at this time was 181 ° C. on the metal roll surface, and the linear pressure was 250 kg / cm. Under the same conditions, the felt surface of the coated base paper was in contact with the metal roll, and the paper was passed once for surface treatment. The coated base paper after this surface treatment was coated on both sides at 6 g / m ² (absolute dry) on one side.

Example 2 Water content of coated base paper was adjusted by adjusting papermaking conditions.
The content was adjusted to 8% by weight, and immediately before passing through the soft calendar, steam was blown onto the base paper to adjust the water content to 7.8% by weight. As the soft calendar, in Example 1, an elastic roll having a Shore D hardness of 70 degrees (trade name “Elaglas K” urethane rubber elastic film, manufactured by Kinyosha Co., Ltd.) was used, the temperature on the metal surface was 98 ° C., and a wire was used. 220 kg / c
A coated paper was produced in the same manner as in Example 1 except that m was used.

Example 3 A coated paper was prepared in the same manner as in Example 1 except that the coated base paper after the same surface treatment as in Example 1 was coated on both sides at 19 g / m ² (absolutely dry) on each side. Was manufactured.

Example 4 The same surface-treated coated paper as in Example 2 was used, and one side 1
Example 2 except that 9 g / m ² (absolutely dry) was applied on both sides.
A coated paper was manufactured in the same manner as in.

Comparative Example 1 A coated paper was produced in the same manner as in Example 1 except that the papermaking conditions were adjusted to adjust the water content of the coated base paper to 4.5%.

Comparative Example 2 In Example 1, the papermaking conditions were adjusted to adjust the water content of the coated base paper to 6.9%, and immediately before passing through the soft calender, steam was blown to the water content of 8.7% by weight. The coated paper was adjusted and manufactured in the same manner as in Example 1.

Comparative Example 3 A coated paper was produced in the same manner as in Example 2 except that a soft calendar made of an elastic roll having a Shore D hardness of 99 degrees was used.

Comparative Example 4 A coated paper was produced in the same manner as in Example 2 except that a soft calender composed of an elastic roll having a Shore D hardness of 60 degrees was used.

Comparative Example 5 The water content in Example 1 was adjusted to 5.1% by weight with a machine calender consisting of 6-stage metal rolls including steam rolls, chilled rolls, chilled rolls, steam rolls, chilled rolls and crown control rolls from the top. Then
Both sides of the manufactured coated base paper were surface-treated. At this time, the lowermost linear pressure was 50 kg / cm and the steam roll surface temperature was 80 ° C. A base paper surface-treated under such conditions was coated on both sides at 6 g / m ² (absolute dry) on one side to produce coated paper.

Comparative Example 6 A coated paper was produced in the same manner as in Example 3 except that the papermaking conditions were adjusted to adjust the water content of the coated base paper to 4.5%.

Comparative Example 7 In Example 3, the papermaking conditions were adjusted to adjust the water content of the coated base paper to 6.9%, and immediately before passing through the soft calender, steam was blown to the water content of 8.7% by weight. %,
A coated paper was manufactured in the same manner as in Example 3.

Comparative Example 8 A coated paper was produced in the same manner as in Example 4 except that a soft calender composed of an elastic roll having a Shore D hardness of 99 degrees was used.

Comparative Example 9 A coated paper was produced in the same manner as in Example 2 except that a soft calender composed of an elastic roll having a Shore D hardness of 60 degrees was used.

Comparative Example 10 In Comparative Example 5, a base paper surface-treated with a machine calender was coated on both sides at 19 g / m ² (absolute dryness) on each side to produce a coated paper.

Reference Example 1 Coated paper in the same manner as in Comparative Example 5 except that the coated base paper after the same surface treatment as in Comparative Example 5 was applied to both sides at 22 g / m ² (absolute dry) on each side. Was manufactured. The quality of the coated papers produced in Examples 1 to 4, Comparative Examples 1 to 10 and Reference Example 1 was evaluated by the following method.

Evaluation method Tuck No. manufactured by Dainippon Ink and Chemicals, Inc. using a Roland Favorite RZ F01 type printing machine (manufactured by Germany)
90 Offset printing is performed with two red indigo colors and the printability is visually judged. Ink acceptability in offset printing (indicator of occurrence of mottling) ◎: Particularly excellent ○: Excellent △: Normal ×: Slightly inferior × ×: Inferior

Smoothness: Measured based on J Tappi No5.

The ink receptivity was evaluated by visually observing the degree of white spots on the printed matter printed by the gravure printing aptitude test method (printing station type) according to the following 5 grades. ◎: Particularly excellent ○: Excellent △: Normal ×: Slightly inferior × ×: Inferior

Opacity: JIS P 8138
Measured based on.

Examples 1 to 4, Comparative Examples 1 to 10, Reference Example 1
Table 1 shows the quality evaluation results of the coated paper produced in 1. Table 1
As can be seen from the above, the coating amount per one surface of Reference Example 1 was 20.
Those exceeding g / m ² (absolute dryness) are excellent in printability regardless of the present invention. Comparing the coated papers having the same coating amount, it is clear that the Mottling and gravure printing ink receptivity is excellent as compared with Examples 1 and 2 and Examples 3 and 4 based on the present invention. The effect of is obvious.

[0063]

[Table 1]

Claims (1)

[Claims] 1. A metal roll and Shore D hardness (ASTM
A method for producing a base paper for a coated paper for printing, which comprises subjecting a base paper whose moisture content is adjusted to 5 to 8% by weight to a surface treatment with a calendering device comprising an elastic roll having a standard D2240) of 65 to 98 degrees.