JP3328554B2 - Method for producing coated paper for offset printing - 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 producing a coated paper for coating a base paper with a coating liquid having a pigment and an adhesive, by applying the coating liquid by a gate roll system to reduce the cost. The present invention relates to a method for producing a coated paper for offset printing which can be produced by the method described in (1).

[0002]

2. Description of the Related Art In recent years, demand for printing paper in the field of commercial printing for advertising and promotion such as flyers, catalogs, brochures, and direct mail has been growing. Although these commercial prints have low commercial value themselves, it is important that the purpose be achieved as an advertising medium, and therefore, low-cost, high-quality prints have been demanded. Accordingly, the cost reduction of paper users is becoming stronger, and the paper used is also becoming lower grade, thinner and lighter.

In order to respond to such a vigorous demand, paper manufacturers have been increasing the width and speed of coating apparatuses in order to produce products more efficiently and reduce costs, while maintaining high quality. Improving productivity is an important issue. Therefore, in recent years, on-machine coating methods in which papermaking and coating are simultaneously performed by one machine tend to be often used as production equipment. In addition, the base paper is coated with an undercoat coating liquid containing an inexpensive pigment on-machine and then coated with a top coat coating liquid, thereby improving the coatability of the base paper by the undercoat coating in terms of quality. Since the shape and the printing quality are improved, the multilayer coating tends to be advanced even in the production of lightweight coated paper.
For this reason, there is a demand for an even faster on-machine coating apparatus.

[0004] A gate roll coater is known as an on-machine coating method suitable for high-speed coating. This gate roll coater is generally used for coating a coating liquid containing no pigment, such as a coating for a sizing agent.
High-speed coating exceeding 00 m / min can be performed. However, when the coating liquid for producing coated paper containing pigment is coated on the base paper using this coater, the following problems occur.

(A) Peeling pattern (a phenomenon in which the paper separation at the exit of the application roll nip is not stable, and a uniform pattern surface unevenness occurs on the paper surface, (b) gum-up (between rolls having different roll diameters and peripheral speeds) Phenomenon in which the coating liquid solidifies due to the shearing force applied to it and adheres to the roll surface, (c)
Mist (The phenomenon that the coating liquid becomes mist at the exit of the application roll nip and scatters, and (d) Boiling (the coating liquid pond at the nip entrance between the outer gate roll and the inner gate roll that supplies the coating liquid) This is a phenomenon in which the coating liquid is seen to boil in the air, and when the boiling becomes severe, the coating liquid scatters around and significantly contaminates peripheral devices and machines, which hinders the operation.) Becomes noticeable when the coating speed exceeds 1000 m / min, and becomes remarkable when the coating speed exceeds 1100 m / min.
It is difficult to apply a coating liquid containing a pigment in excess of 1100 m / min.

On the other hand, in terms of quality, on-machine coated paper using base paper that has not been subjected to surface sizing in advance with starch is:
After sizing the starch on the base paper using a conventional two-roll press, the surface is coated on a single-layer coated paper containing a pigment and an adhesive, or the starch is applied to the base paper using a two-roll press. There is an inherent problem that dry strength (print surface strength of a solid printing surface) is inferior to a multi-layer coated paper in which a coating liquid containing a pigment and an adhesive is applied twice after off-machine after sizing. In addition, on the printing side, the on-press tackiness of ink has been increased along with the speeding up of offset printing, and the problem of vessel opening (vessel picking) unique to hardwood has been increasing. Therefore, in order to improve these problems of dry strength and vessel picking, in recent years, there has been a tendency to mix starch or a derivative thereof as much as possible as an adhesive component in a coating liquid. However, in general, as the amount of starch or a derivative thereof is increased, the viscosity of the coating liquid increases, and the above-mentioned peeling pattern frequently occurs.

[0007]

In view of the above situation, an object of the present invention is a problem in a manufacturing process in which a gate roll coater is used and coating is performed at a high coating speed of 1100 m / min or more. No peeling pattern, no boiling
An object of the present invention is to provide a coated paper for offset printing which is excellent in surface condition and dry strength after coating.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies on the above problems and as a result, have found that a method for producing a coated paper for offset printing in which a base paper is coated with a coating liquid having a pigment and an adhesive. Using a gate roll coater having an applicator roll having a diameter of 1400 mm or more, comprising a coating liquid prepared by mixing 15 to 35 parts by weight of starch or a derivative thereof as an adhesive component with respect to 100 parts of a pigment; The present invention has been accomplished by coating the base paper with a peripheral speed ratio of the inner and outer gate rolls of 50 to 80% to the base paper. Furthermore, even if the top coat was applied on the coated paper, a multilayer coated paper of good quality could be obtained.

The details of the present invention will be described below.

In order to prevent the coated paper coated with a coating liquid having a pigment and an adhesive by a gate roll coater from causing the problems of dry strength and vessel pickling, the present inventors have proposed that starch or its adhesive be used as an adhesive. Derivative to pigment 100
It was recognized that it was necessary to distribute at least 15 parts by weight or more per part. However, the type and particle size of the pigment used,
Although it depends on the shape and the like, the higher the speed, the more the release pattern is likely to occur, and the surface of the coated paper tends to be inferior.
It was recognized that this tendency was remarkable above minutes. These problems can be solved, for example, by lowering the coating liquid concentration and lowering the coating liquid viscosity, but in addition to increasing the drying load,
Since the coating liquid seeps into the base paper more frequently, and the base paper coatability is inferior, the gloss unevenness after coating increases, and the surface state deteriorates. As another means, there has been proposed a method of lowering the viscosity of a coating solution by changing a formulation such as using a pigment having a large average particle diameter, a latex, or a starch having a low molecular weight or a low viscosity or a derivative thereof.

The present inventors have conducted intensive studies to solve these problems from the viewpoint of equipment, and found that it is effective to apply the coating liquid to the base paper using an applicator roll having a diameter of 1400 mm or more. Admitted. At the same coating speed, as the diameter of the applicator roll is smaller, the coating liquid film on the applicator roll nip is transferred to the base paper, and the coating film splits at the nip exit on the applicator roll side and the base paper side, and the base paper is Since the peeling angle and the peeling speed at the time of peeling from the applicator roll become large, many peeling patterns are generated. Therefore, when applying a coating liquid containing 15 parts by weight or more of starch or a derivative thereof to 100 parts of pigment, in order to suppress the occurrence of a peeling pattern that becomes more remarkable as the operation is performed at a higher speed, the diameter of the applicator roll must be reduced. Found that a size of 1400 mm or more was necessary. The larger the diameter is, the better, but if the diameter is too large, the roll's own weight will be too heavy, causing problems with deflection and width profile, and problems such as space and roll changeability. Is not separately solved, the upper limit of the diameter is about 2000 mm.

However, when a coating liquid containing starch or a derivative thereof in an amount of more than 35 parts by weight per 100 parts of pigment is applied, the viscosity of the coating liquid becomes too high, and it is difficult to increase the diameter of the applicator roll alone. However, the problem of the peeling pattern cannot be solved.

Further, the present inventors have studied the remedies for the problem of boiling, and as a result, by reducing the peripheral speed ratio of the inner and outer gate rolls to the applicator roll to 80% or less, the occurrence of boiling is minimized. Admitted that it can be kept to a minimum. Although the reason for this is not clear, it is considered that the peripheral speeds of the inner gate roll and the outer gate roll themselves are reduced, and the number of roll rotations is reduced, so that it is difficult to hold bubbles. However, the peripheral speed ratio is 50%
If the diameter is smaller, the abrasion of each roll becomes severe due to the shearing force between the rolls, causing a problem that the life of the roll is shortened.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, pigments used in coating liquids are mainly heavy calcium carbonate, light calcium carbonate, kaolin, clay, delaminated clay, talc, satin white, silica, barium sulfate. And inorganic pigments such as calcium sulfate, zinc oxide, and titanium dioxide; and organic pigments such as plastic pigments. These pigments can be used alone or as a mixture of two or more as needed.

[0015] Among the adhesives used in the coating liquid, the starch derivative is obtained by subjecting starch to physical, chemical or biological manipulation as required, regardless of the type of starch raw material. Commonly used esterified starch such as oxidized starch, phosphated starch, etherified starch such as hydroxyethyl etherified starch, enzyme-modified starch, cold water soluble starch and the like are used.

It is preferable to use a latex in combination with starch or a derivative thereof alone. The composition of the latex is a styrene / butadiene copolymer, a styrene / butadiene / acrylic copolymer, or a modified product thereof, which is generally used, and the monomers are styrene, butadiene, methyl methacrylate, etc. Vinyl-based unsaturated carboxylic acid ester compounds,
Other vinyl compounds such as acrylonitrile, and vinyl unsaturated acids such as acrylic acid and fumaric acid.

Other aqueous adhesives include cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, proteins such as casein, soybean protein and synthetic protein, and adhesives such as polyvinyl alcohol, polyvinylpyrrolidone, and olefin / maleic anhydride resins. You can do it.

The above-mentioned pigments and adhesives are also used for the top coating liquid and the undercoat liquid.

In the coating liquid of the present invention, various auxiliaries, such as a dispersant, a thickener, a water retention agent, a defoaming agent, and a water-proofing agent, which are blended in a general pigment for coated paper may be used.

The base paper is a base paper having a basis weight of 30 to 100 g / m ² used for general coated paper for printing. Fine paper and medium paper are selected and used depending on the purpose.

The coating is performed on both sides using a six-roll gate roll coater in which one side of the base paper is coated with three rolls of an applicator roll, an inner gate roll, and an outer gate roll. Is preferred. The diameter of the inner and outer gate rolls is smaller than the applicator roll, and preferably ranges from 860 to 1450 mm.

Further, when overcoating the coated paper obtained by the method of the present invention, a roll application type or a fountain nozzle type blade coater is mainly used, and one or more coating layers are used. May be provided.

The concentration of the coating solution for the gate roll coating is in the range of 30 to 45%, and the coating amount is in the range of ² to 8 g / m ^{2 in} solid content per one side of the base paper. Is preferred. This is because when the amount of coating is less than 2 g / m ^{2, the} concentration of the coating liquid must be greatly reduced due to limitations in the apparatus, and as a result, the coating properties of the base paper and the surface condition are liable to be reduced. When applying more than 8 g / m ² , it is necessary to increase the coating solution concentration,
In this case, it is difficult to control the amount of coating on the apparatus, and at the same time, a matte surface roughness and a roll pattern easily occur on the paper surface. Further, the concentration of the coating liquid at the time of overcoating is preferably from 60 to 68%, and the coating amount is usually preferably from 6 to 14 g / m ^{2 as a} solid content per one surface. The coated paper is
After the coating liquid is coated and dried on the base paper, it is manufactured as it is or through a finishing process such as a super calender or a soft calender.In the present invention, when the finishing process of the calender treatment is used, there is no unevenness in glossiness of white paper. The effect of obtaining a good surface condition is great.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited by these examples. In the examples, parts and% indicate parts by weight and% by weight, respectively.

<Quality evaluation method> (1) Pigment average particle diameter: The average particle diameter was measured as the average particle diameter at the 50% point of the weight cumulative distribution using a SHIN5000 light-transmitting particle size distribution analyzer manufactured by Seishin Enterprise. (2) Blank glossiness: Specular glossiness at an angle of 75 degrees was measured according to JIS P-8142. (3) Release pattern: The occurrence of the release pattern on the paper surface after the undercoating was visually determined. ＝= Not generated at all, ほ と ん ど = Not generated at all △ = Produced, × = Remarkable generation (4) Boiling: The occurrence of boiling at the time of undercoating was relatively visually evaluated. ＝= Not generated at all, ＝= Not generated at all △ = Produced, × = Remarkably generated (5) Surface condition: Unevenness in glossiness of white paper after overcoating was relatively evaluated by visual observation. ＝= No unevenness, ＝= Almost no unevenness, △ = Some unevenness, × = Notable unevenness (6) Dry strength: Using a RI-I type printing machine (manufactured by Mei Seisakusho), TV-24 manufactured by Toyo Ink Using the ink amount 0.3
Printing was carried out at a constant volume of 5 ml, and the degree of picking on the printing surface was visually evaluated. ○ = no picking, △ = picking, × = significant picking

Example 1 The pigment has an average particle size of 0.1.
95 parts of 65 μm heavy calcium carbonate and 0.50 μm
To 100 parts of a pigment containing 5 parts of kaolin, 0.3 part of a sodium polyacrylate dispersant was added and dispersed in water using a Cowles disperser, and 25 parts of a phosphorylated starch was used as an adhesive. And 4 parts of carboxy-modified styrene / butadiene copolymer latex were blended to prepare an undercoat coating solution having a concentration of 38%. An applicator roll having a diameter of 1450 mm and an inner gate roll having a diameter of 970 mm were added to base paper containing only bleached kraft pulp having a basis weight of 45 g / m ^2.
Using a gate roll coater composed of a 20 mm outer gate roll, a peripheral speed ratio of the inner and outer gate rolls to the applicator roll of 55%, a coating speed of 1200 m / min, and a solid content of 5 g / m ² (both sides) ) Soft calender treatment (50 ° C, 80kg / c)
m).

Next, to 100 parts of the pigment containing 60 parts of heavy calcium carbonate and 40 parts of kaolin, 0.3 part of a sodium polyacrylate dispersant was added and dispersed in water using a Cowles disperser. Then, 4 parts of phosphorylated esterified starch and 10 parts of carboxy-modified styrene / butadiene copolymer latex were blended as an adhesive, a 64% concentration topcoat coating liquid was prepared, and a high-speed fountain type blade coater was used. At a speed of 1200 m / min.
6 g / m ² (both sides) were coated.

Further, using a two-roll / four-stack soft calender, the metal nip of each of the first to third nips was 150 ° C., the linear pressure was 200 kg / cm, and the fourth nip was 45 kg.
It was calendered at 100 ° C / cm.

Example 2 30 parts of a hydroxyethyl etherified starch was used as a starch in the undercoating coating solution, and 2 parts of a carboxy-modified styrene / butadiene copolymer latex was used, and a 36% concentration undercoating solution was used. And an applicator roll with a diameter of 1830 mm and 10
A gate roll coater composed of a 20 mm inner gate roll and a 1450 mm outer gate roll, except that the undercoat was applied under the condition that the peripheral speed ratio of the inner and outer gate rolls to the applicator roll was 70%. Similarly, coated paper was produced.

Example 3 The pigment has an average particle size of 0.1.
50 parts of 65 μm heavy calcium carbonate and 0.50 μm
To 100 parts of a pigment containing 50 parts of kaolin, 0.3 part of a sodium polyacrylate dispersant was added and dispersed in water using a Cowles disperser, and 17 parts of a phosphorylated starch was used as an adhesive. And a carboxy-modified styrene / butadiene copolymer latex (10 parts), and a coating solution having a concentration of 50% was used. The coating solution was applied by a gate roll coater under the same conditions as in Example 1 above. At that time, the coating amount was 14 g / m ^{2 in} solid content.
(Double-sided) coating, followed by calendering at 100 ° C. and 100 kg / cm using a two-roll, two-stack soft calender to obtain a single-layer coated paper.

Comparative Example 1 An applicator roll having a diameter of 1240 mm and an inner gate roll having a diameter of 860 mm
A coated paper was produced in exactly the same manner as in Example 1 except that a gate roll coater composed of a 0 mm outer gate roll was used.

Comparative Example 2 An applicator roll having a diameter of 1060 mm and an inner gate roll having a diameter of 860 mm
Example 1 Example 1 was a gate roll coater composed of a 0 mm outer gate roll, except that undercoating was performed at a coating speed of 850 m / min under the condition that the peripheral speed ratio of the inner and outer gate rolls to the applicator roll was 95%. A coated paper was manufactured in exactly the same manner as in Example 1.

[Comparative Example 3] The undercoating coating liquid was prepared by using 13 parts of a phosphate esterified starch, and further mixing 10 parts of a carboxy-modified styrene / butadiene copolymer latex with a 35% concentration undercoating liquid. Is a gate roll coater consisting of an applicator roll of 700 mm, an inner gate roll of 560 mm and an outer gate roll of 600 mm, and the coating speed is set at a peripheral speed ratio of the inner and outer gate rolls to the applicator roll of 40%. A coated paper was produced in exactly the same manner as in Example 1, except that the primer was coated at 1000 m / min.

Comparative Example 4 A coated paper was produced in exactly the same manner as in Example 1 except that 12 parts of hydroxyethyl etherified starch was used in the undercoat coating liquid.

Comparative Example 5 A coated paper was produced in exactly the same manner as in Example 1 except that 38 parts of oxidized starch was used in the undercoating coating liquid.

Comparative Example 6 A coated paper was produced in exactly the same manner as in Example 1 except that the peripheral speed ratio of the inner and outer gate rolls to the applicator roll was 40%.

Comparative Example 7 A coated paper was manufactured in exactly the same manner as in Example 1 except that the peripheral speed ratio of the inner and outer gate rolls to the applicator roll was 90%.

Comparative Example 8 An applicator roll having a diameter of 1240 mm and an inner gate roll having a diameter of 860 mm
A coated paper was produced in exactly the same manner as in Example 3 except that a gate roll coater constituted by a 0 mm outer gate roll was used. Table 1 shows the above results.

[0039]

[Table 1]

As is evident from Table 1, Examples 1, 2 and 3 have no peeling pattern and no problem of boiling, are excellent in high-speed operability, and have no problem in quality in terms of surface condition and dry strength.

On the other hand, in Comparative Example 1, the release pattern
Comparative Example 2 is inferior in the surface pattern, and the peeling pattern, the boiling and the surface state are inferior in Comparative Example 2. Comparative Example 3 is inferior in peel pattern and surface condition, inferior in dry strength, and has large roll abrasion. Comparative Example 4 is inferior in dry strength, and Comparative Example 5 is inferior in release pattern, boiling, and surface state. In Comparative Example 6, the abrasion of the roll was large.
Comparative Example 7 is inferior in boiling. Comparative Example 8 is inferior in the release pattern and the surface state.

[0042]

EFFECT OF THE INVENTION Using a gate roll coater, improved operability, which is a problem in the manufacturing process of coating a coating liquid having a pigment and an adhesive under high-speed conditions, is excellent in surface printing. Provide paper.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yukio Fukudome 2-1-1, Iida-cho, Iwakuni-shi, Yamaguchi Japan Inside the Iwakuni Mill of Nihon Paper Industries Co., Ltd. (56) References JP-A-9-170195 (JP, A) JP-A-9-67796 (JP, A) JP-A-9-85144 (JP, A) JP-A-6-55113 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27/42 B05C 1/00-3/20 B05D 1/00-7/26

Claims (3)

(57) [Claims] 1. A method for producing a coated paper in which a base paper is coated with a coating liquid containing a pigment and an adhesive, wherein starch or a derivative thereof is used as an adhesive component in an amount of 15 to 100 parts of the pigment.
To 35 parts by weight of the coating liquid, and using the coating liquid with a gate roll coater having an applicator roll having a diameter of 1400 mm or more, and a peripheral speed ratio of the inner and outer gate rolls to the applicator roll of 50 or more. ~
A method for producing coated paper for offset printing, characterized in that the base paper is coated within a range of 80%. 2. A method for producing a coated paper in which a base paper is coated with a coating liquid containing a pigment and an adhesive, wherein starch or a derivative thereof is used as an adhesive component in an amount of 15 to 100 parts of the pigment.
An undercoating coating solution containing up to 35 parts by weight was prepared, and the undercoating coating solution was prepared using a gate roll coater having an applicator roll having a diameter of 1400 mm or more, and a peripheral speed ratio of the inner and outer gate rolls to the applicator roll. A method for producing coated paper for offset printing, comprising coating a base paper within a range of 50% to 80% and then applying a topcoat liquid. 3. The method for producing coated paper for offset printing according to claim 1, wherein the coating is performed at a coating speed of 1100 m / min or more.