JP3143892B2 - Coated paper for rotary offset printing and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper for rotary offset printing which is excellent in high-speed operability, blister resistance and glossiness of blank paper.

[0002]

2. Description of the Related Art In recent years, demand for printing paper has tended to gradually increase. In particular, there is a growing demand in the commercial printing field for advertisements and advertisements such as flyers, catalogs, brochures, and direct mails. 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 are required. Also,
On the other hand, the cost reduction of users is becoming stronger, and the paper used is also lower in grade and weight.

[0003] In order to respond to such strong demand for coated paper, paper manufacturers are promoting wider and faster coating equipment in order to more efficiently produce products and reduce costs. In such a situation, it is an important technical problem to increase productivity while maintaining high quality.

[0004] Conventional methods for producing coated paper include an off-machine coating method in which papermaking and coating are performed in separate steps, and an on-machine coating method in which papermaking and coating are performed simultaneously by a single machine. The on-machine coating method enables more efficient production. In the case of multi-layer coated paper, the cost can be reduced by applying an undercoating coating liquid containing an inexpensive pigment on-machine, and the undercoating coating improves the coverage of the base paper. It is generally said that the quality also improves. However, the quality of multi-layer coated paper produced by the on-machine coating method is higher than that of single-layer coated paper because the basis weight of the base paper is reduced and the total coating amount of the base coat and top coat is reduced accordingly. I have to do a lot of it. Conventionally, in the production of single-layer coated paper, the pigment coating liquid is applied to the base paper so that the pigment coating liquid does not seep into the base paper. Had been doing. However, in the case of on-machine multi-layer coating, the surface size coating and the undercoat pigment coating are performed simultaneously, so that the undercoat pigment coating liquid permeates into the base paper. As a result, the same quality cannot be obtained unless the total amount of pigment coating is made greater than in the case of single-layer coated paper. Therefore, at present, the cost is not necessarily reduced by multilayer coating.

[0005] In order to further reduce costs, paper makers have made efforts to make the total coating amount the same as the coating amount of single-layer coated paper, that is, to reduce the coating amount.
In this case, there is a problem that the smoothness, glossiness of white paper, and gloss after printing are inferior to those of the single-layer coated paper.

As described above, in recent years, in order to further improve productivity, an attempt has been made to commercialize an on-machine coating apparatus at a higher speed. In general, a gate transfer coater, a blade or a rod metaling size press coater of a film transfer system is used for the on-machine coating apparatus. Due to various operability and quality problems, the maximum operable speed to date is about 1100.
m / min is said to be the limit. Operational problems that become prominent at a speed higher than 1100 m / min include problems such as mist generation in which the coating liquid becomes mist at the exit of the application roll nip and shearing between rolls having different roll diameters and peripheral speeds. There is a gum-up problem in which the coating liquid solidifies due to the force and adheres to the roll surface.

[0007] These problems can be reduced by lowering the concentration of the coating solution. However, in addition to increasing the drying load, the coating solution is more likely to soak into the base paper in terms of quality, and it becomes difficult to control the coating amount. At the same time, there is a problem that the base paper covering property is inferior and the surface properties, surface condition, and printability deteriorate.

As described above, in the case of on-machine multi-layer coating, the same coating amount as in the case of single-layer coated paper results in inferior surface properties and printability, and the problem of operability becomes more pronounced at higher speed conditions. Therefore, it is difficult to achieve both quality and operability.

On the other hand, the characteristic of the demand for coated paper in recent years from the viewpoint of the printing method is that the coated paper for rotary offset printing is increasing and the required quality is also diversified in response to the speeding up of the offset printing field. . Among them, blister resistance is one of the most important qualities. In rotary printing, the moisture contained in the paper layer of the coated paper is also evaporated in order to dry the printing ink at a high temperature. If the air permeability of the coated paper is inferior, the generated vapor does not escape and blisters occur on the coated paper surface. This blister is called a blister and is one of the defects in printed matter. With the rapid increase in printing speed, there is a demand for printing paper having better blister resistance. At the same time, as described above, it is an important issue to obtain a high surface property with a smaller coating amount by a more efficient production means, that is, an on-machine multilayer coating method.

However, the multi-layer coated paper usually has a lower air permeability than the single-layer coated paper, and thus has a problem that the blister resistance is inferior. Therefore, many studies have hitherto been made with a view to improving the blister resistance of the multilayer coated paper and mainly from the viewpoint of optimizing the binder and the pigment. As a method for improving the binder, the undercoat layer has a gel content of 5 to 60% and the overcoat layer has a gel content of 60%.
How to use 95% of latex (JP fairness 7-13
No. 360), the average particle diameter of the undercoat layer is 1500.
Latex having a gel content of not more than 60% and a mean particle diameter of 500 to
1500 angstrom, 30-90% gel content
Using latex (Japanese Patent Laid-Open No. 2-269897)
Japanese Patent Application Laid-Open No. H11-216, and a method in which a base paper is coated with a coating liquid using a latex having a gel content of 15 to 70% in a base coat layer, and then subjected to a soft calender treatment. All of these use latex having a low gel content in the undercoating coating layer, and use a film transfer type coating apparatus using such a latex having a low gel content, such as a gate roll coater, at a high speed. When the coating liquid is applied to the base paper, there is a problem that a gum-up trouble occurs as described above.

As described above, by using the film transfer method for the undercoating and the blade method for the overcoating, the coated paper for rotary offset printing excellent in high-speed operability and excellent in blister resistance can be obtained. Had not been obtained.

[0012]

In view of the above situation, the undercoating coating solution is applied using the above-described on-machine coating method under high-speed conditions, particularly at a high speed of 1100 m / min or more. Improves gum-up troubles that lower the operability of the manufacturing process. In addition, in terms of quality after overcoating, it is excellent in blister resistance, and has excellent surface properties (white paper gloss) with less coating amount. An object of the present invention is to provide a coated paper for offset printing.

[0013]

The inventors of the present invention have conducted intensive studies on the above problems, and as a result, have found that a coating for rotary offset printing having an undercoat coating layer and an overcoat coating layer containing a pigment and an adhesive, respectively. In the base paper, the base paper has a gel content of 7
A styrene-butadiene-based copolymer latex having a butadiene content of 20 to 40% by weight after applying an undercoating coating liquid containing a styrene-butadiene-based copolymer latex of 5 to 90% by weight by a film transfer method. The present invention has been accomplished by coating a topcoating coating solution containing the above with a blade system.

When a base coat is applied to base paper at a high speed by using a film transfer system such as a gate roll or a rod metering size press as a system for applying the undercoat coating solution, the gel content is 75 to 90. By using the weight% latex, it was recognized that the mechanical stability of the latex could be maintained, the gum did not occur between the rolls, and the operability was excellent. On the other hand, when the gel content is less than 75% by weight, the mechanical stability of the latex is inferior and the phenomenon of gum up between the rolls is observed, and the operability is reduced. When the gel content exceeds 90% by weight, the adhesive is used. Does not fulfill its function.

Next, an overcoating liquid containing a styrene / butadiene copolymer latex having a butadiene content of 20 to 40% by weight is applied by a blade method, whereby the blister resistance is improved and the conventional method is used. The glossiness of white paper can be increased with a coating amount as small as a single-layer coated paper. In this regard, since the film forming property of the latex is small, the coating layer becomes more porous, and as a result, steam easily escapes during rotary offset printing, and the blister resistance is improved. Further, since the film formability is small, the shrinkage of the latex film during drying is suppressed, and the orientation of the pigment is less disturbed during drying. The white paper glossiness is greatly improved. When a latex having a butadiene content of less than 20% by weight is used, not only does the film formability become too small, so that not only the adhesion ability is inferior, the printing surface strength is reduced, but also the voids in the coating layer become too large and the ink becomes too large. The drying property becomes faster and the gloss after printing decreases. If the butadiene content exceeds 40% by weight, the film forming property of the latex is large and the air permeability of the coating layer is inferior, so that the blister resistance is lowered. As a result of excessive penetration into the inside of the coating layer, gloss after printing is reduced. The latex used in the overcoating liquid of the present invention can achieve the desired quality and operability only by controlling the butadiene content within the range of 20 to 40% by weight. If the gel content is limited to 30 to 60% by weight, more excellent blister resistance can be obtained. Furthermore, as a result of further study on the optimal butadiene content of the latex used in the undercoating coating layer, it is desirable that the butadiene content in the monomer used be 35 to 70% by weight. When the amount is less than 35% by weight, the printing surface strength after overcoating is inferior, and when it is more than 70% by weight, the gloss after printing tends to decrease.

The film transfer type coating apparatus used for the undercoating coating used in the present invention is, in particular, 11
It is desirable to use a gate roll coater or a rod metering size press coater having a rod having a smooth surface with a diameter of 30 to 50 mm, which can operate even at a high speed of 00 m / min or more. When a rod metering size press coater having a smooth rod is used, a rod smaller than 30 mm cannot transfer a uniform film to the paper surface due to the ability of the coating liquid to form a film, so that the surface of the topcoat coating liquid cannot be transferred. It tends to be inferior. On the other hand, rods larger than 50 mm do not need to be particularly large because the effect does not change. If the rod is not a smooth surface, that is, if it is a rod with a groove, a new problem of streak generation is likely to occur.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The pigment used in the undercoat coating layer used in the present invention is mainly heavy calcium carbonate or light calcium carbonate in terms of cost, but other pigments such as kaolin, clay, talc, satin white, One or more types of plastic pigment, titanium dioxide, silica and the like are used.

The styrene / butadiene copolymer latex used in the undercoat coating layer of the present invention contains styrene and butadiene as monomers, and may be copolymerized with other monomers as necessary, or may be copolymerized by a chemical reaction. This is a modified copolymer latex generally used for paper coating. As other monomers, vinyl monomers such as acrylic acid, methacrylic acid, alkyl esters of acrylic acid or methacrylic acid, acrylonitrile, maleic acid, fumaric acid, and vinyl acetate are often used. Although the amount of the latex varies depending on the pigment used, it is preferable to use the latex in the range of 3 to 8% by weight based on the total pigment. Further, in addition to the latex of the present invention, in order to maintain the water retention of the coating liquid and increase the internal bond strength of the base paper, oxidized starch, esterified starch, enzyme-modified starch, etherified starch and the like are obtained by flash drying. Natural adhesives such as cold water-soluble starch, casein, soy protein, etc., and synthetic adhesives such as polyvinyl alcohol may be used in combination.

As the pigment for the overcoat layer used in the present invention, one or more of heavy calcium carbonate, light calcium carbonate, kaolin, clay, talc, satin white, plastic pigment, titanium dioxide, silica and the like are used. However, from the viewpoint of high-speed operability and quality, it is preferable that heavy calcium carbonate is blended in an amount of 50 to 70% by weight based on all the pigments, and the average particle diameter is 0.3 to 0.9 μm.

The adhesive used in the overcoating liquid of the present invention may be styrene / butadiene, styrene / acrylic,
Various copolymer latexes such as acrylic, vinyl acetate / acrylic, butadiene / methyl methacrylic, or denatured products by chemical reaction of these various copolymer latexes, synthetic adhesives such as polyvinyl alcohol, starch oxide, ester One or more types of starch, enzyme-modified starch, etherified starch, cold-water-soluble starch obtained by flash-drying them, and natural adhesives such as casein are used. It is desirable to use the latex in an amount of 7 to 12% by weight based on the total pigment. Also, the average particle diameter of the latex is preferably 50 to 110 nm from the viewpoint of high-speed operability and quality.

In the coating liquid of the present invention, various auxiliaries, such as a dispersant, a thickener, a water retention agent, an antifoaming agent, and a water-proofing agent, which are blended in a general pigment for coated paper may be used. As base paper, a basis weight of 30 to 100 g / m used for a general coated paper for printing is used.
Base paper ² is preferred, and high quality paper and medium quality paper are selected and used according to the purpose.

The undercoating and the overcoating may be not only a single layer but also a multilayer, and the total coating amount of the undercoating and the overcoating is 9% in solid content per one side of the base paper.
It is preferred that the coating be performed in the range of ２０20 g / m ² .

The coated paper which has been coated and dried as described above,
It is manufactured by glossing by a finishing process such as a normal super calender or soft calender.

[0024]

The present invention will be specifically described below with reference to examples. In the examples, parts and% indicate parts by weight and% by weight, respectively. The quality evaluation method is as follows.

<Quality Evaluation Method> (1) Calcium Carbonate Average Particle Size Seishin Enterprise Light Transmission Type Particle Size Distribution Measurement System SHC5000
Was used to measure the 50% point of the weight cumulative distribution as the average particle diameter.

(2) Gel content of latex About 0.3 g of latex is spread thinly on a slide glass.
Dry in a dryer at 50 ° C. until a film is formed. The latex film is immersed in about 50 ml of toluene for 24 hours, filtered with a glass filter, and the filtrate is dried with a dryer at 105 ° C., and the weight of the toluene-soluble matter is measured. From the weight of the toluene-soluble component obtained here, the gel content is calculated by the following equation.

Gel content (%) = (dry film weight−toluene soluble weight) × 100 / (dry film weight) (3) Glossiness of white paper Measured at an angle of 75 ° according to JIS P-8142.

(4) Gloss after printing Using an RI-II type printing machine (manufactured by Meiji Seisakusho), printing was performed using 0.35 cc of offset printing ink (trade name: Diatone GSL Red) manufactured by Sakata Inx, and left overnight. , 75 degree glossiness.

(5) Printing surface strength Using an RI-II type printing machine (manufactured by Meisho Seisakusho), using Toyo Ink's TV-24, printing with a constant ink amount of 0.35 cc, and checking the degree of picking on the printing surface. The relative evaluation was made visually.

◎ = Not generated at all, ○ = Almost not generated △ = Generated, × = Remarkable generation (6) Blister resistance TV mark V made by Toyo Ink using RI-II type printing machine (manufactured by Meiji Seisakusho) After printing at a constant 0.8 cc using New 617, use hot air with different temperatures between hair dryers.
The mixture was heated for 2 seconds, and the degree of blisters generated was visually evaluated relative to each other.

◎ = Not generated at all, ○ = Not generated at all △ = Produced, × = Remarkable occurrence (7) Evaluation of gum up occurrence Visual observation of gum up occurrence during pigment coating with an undercoat gate roll coater did.

＝= Not generated at all, ○ = Almost not generated △ = Generated, × = Remarkable generation [Example 1] 90 parts of heavy calcium carbonate having an average particle diameter of 1.20 μm and an average particle diameter of 0. To 100 parts of a pigment containing 10 parts of 55 μm kaolin, 0.3 part of a sodium polyacrylate dispersant was added and dispersed in water using a Cowles disperser, and then phosphated starch was used as an adhesive. 19 parts, 5 parts of a carboxy-modified styrene / butadiene copolymer latex having a gel content of 80% and a butadiene content of 40% were blended to prepare an undercoat pigment coating liquid having a solid content of 46%.

Further, 0.3 part of sodium polyacrylate dispersant was added to 60 parts of heavy calcium carbonate having an average particle diameter of 0.65 μm and 40 parts of kaolin, and water was added using a Cowles disperser. Then, 4 parts of a phosphate esterified starch and 10 parts of a carboxy-modified styrene / butadiene copolymer latex having a butadiene content of 25% and a gel content of 50% as an adhesive were blended, and the solid content was 65%.
% Of a topcoat pigment coating solution was prepared.

The coating liquid was bleached to a hardwood having a basis weight of 54 g / m ^{2, and} a kraft pulp blended base paper was coated with a high-speed gate roll coater as an undercoating apparatus at a coating speed of 1100 m / min. After coating 5 g / m ² on both sides and drying, a high-speed fountain blade coater is used as a top coating device, and the coating speed is 1300 m.
At 8 g / m ² at a solids content per side on both sides and dried. Further, gloss finishing was performed using a 12-stage super calendar.

Example 2 In preparing a topcoat coating solution,
A coated paper was produced in the same manner as in Example 1 except that a carboxy-modified styrene / butadiene copolymer latex having a butadiene content of 35% and a gel content of 35% was used.

Example 3 In preparing an undercoating coating solution,
A gel content was 85%, a butadiene content was 60%, and a carboxy-modified styrene / butadiene copolymer latex having a butadiene content of 22% was used in preparing the overcoating coating liquid, in the same manner as in Example 1. Coated paper was produced.

Example 4 As a device for undercoating, a rod metering size press coater having a 35 mm diameter rod having a smooth surface was used, and the coating speed was 1400 m.
A coated paper was produced in the same manner as in Example 1 except that the undercoat was applied at a rate of / min.

[Comparative Example 1] In preparing an overcoating liquid,
A coated paper was produced in the same manner as in Example 1 except that a carboxy-modified styrene / butadiene copolymer latex having a butadiene content of 50% was used.

[Comparative Example 2] When preparing an overcoating liquid,
A coated paper was produced in the same manner as in Example 1 except that a carboxy-modified styrene / butadiene copolymer latex having a butadiene content of 15% was used.

[Comparative Example 3] When preparing an undercoat coating liquid,
Using a carboxy-modified styrene / butadiene copolymer latex having a gel content of 40% and a butadiene content of 25% to prepare an overcoating liquid, a carboxy-modified styrene / butadiene copolymer having a butadiene content of 60% is prepared. A coated paper was produced in the same manner as in Example 1 except that latex was used.

Comparative Example 4 When preparing an undercoating coating solution,
A coated paper was produced in the same manner as in Example 1 except that a carboxy-modified styrene / butadiene copolymer latex having a gel content of 60% was used.

The results are shown in Table 1.

[0043]

[Table 1] As is clear from Table 1, Examples 1 to 4 are excellent in blister resistance, and have high surface strength, blank gloss, high gloss after printing,
No gum up is observed.

On the other hand, Comparative Example 1 was inferior in blister resistance and low in glossiness of white paper and gloss after printing. Comparative Example 2 was inferior in printing surface strength and low in gloss after printing. In Comparative Example 3, gum was generated by the gate roll, was inferior in blister resistance, and had low glossiness on white paper and gloss after printing. In Comparative Example 4, gum up occurs with the gate roll. Therefore, a base paper is coated with a styrene-butadiene copolymer latex having a gel content of 75 to 90% as a base coat liquid by a film transfer method, and then as a top coat liquid.
Coated paper manufactured by coating with a blade method using a styrene-butadiene-based copolymer latex having a butadiene content of 20 to 40% is suitable for rotary offset printing, has excellent high-speed operability, and Excellent white paper glossiness in addition to blister resistance.

[0045]

According to the present invention, a film transfer method is used,
Even at high speed conditions, especially at high speeds of 1100 m / min or more,
It improves operability, which is a problem in the manufacturing process of applying the undercoating coating liquid, and also has excellent blister resistance and high surface properties with less coating amount (white paper gloss The coated paper for rotary offset printing which is excellent in (1) can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-192896 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 19/00-27/42

Claims (5)

(57) [Claims] An undercoat, each containing a pigment and an adhesive.
In a coated paper for rotary offset printing having an overcoat layer different from the undercoat layer, a styrene / butadiene copolymer latex having a gel content of 75 to 90% by weight is contained in the undercoat layer. A coated paper for rotary offset printing, characterized in that a styrene / butadiene copolymer latex having a butadiene content of 20 to 40% by weight is contained in the overcoat layer. 2. The styrene / butadiene copolymer latex used in the overcoat layer has a gel content of 30 to 60.
2. The coated paper for rotary offset printing according to claim 1, wherein the coating weight is% by weight. 3. A method for producing a coated paper for rotary offset printing, wherein a base paper is coated with a coating liquid containing a pigment and an adhesive, and a styrene-butadiene having a gel content of 75 to 90% by weight. An undercoat coating solution containing a copolymer latex is prepared, and this undercoat coating solution is applied to base paper by a film transfer method, and then a styrene / butadiene copolymer having a butadiene content of 20 to 40% by weight is used. A method for producing a coated paper for rotary offset printing, which comprises applying a top coating liquid containing the above by a blade method. 4. In the undercoating, the coating speed is 1
The method for producing a coated paper for rotary offset printing according to claim 3, wherein the coating speed is 100 m / min or more. 5. A coating apparatus using a gate roll coater or a rod metering size press coater having a rod having a smooth surface with a diameter of 30 to 50 mm as a film transfer type coating apparatus used for the undercoating. The method for producing a coated paper for rotary offset printing according to claim 3 or 4, wherein: