JP2910030B2 - 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 having excellent high-speed operability and excellent blister resistance.

[0002]

2. Description of the Related Art In recent years, the demand for coated paper for printing has been increasing with the visualization and upgrading of printing paper. In particular, in response to speeding up in the field of offset printing, the demand for coated paper for rotary offset printing has increased, and the required quality has also been diversified. Among them, blister resistance is the most important quality. In rotary printing, since the printing ink is heated instantaneously, the water contained in the paper layer of the coated paper is also instantaneously evaporated. If the coated paper has poor air permeability,
The generated steam does not escape and causes blisters 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. In addition, it has been proposed that the coating layer be formed into a two-layer structure, and that an inexpensive pigment be used for the undercoating layer to produce a product at a lower cost than a single-layer coated paper. Is increasing.

[0003] However, multi-layer coated paper usually has a lower air permeability than single-layer coated paper, and thus has a problem of inferior blister resistance. 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 conventional latex, a latex having a gel content of 5 to 60% in the undercoat layer and a gel content of 60 to 95% in the overcoat layer (Japanese Patent Laid-Open No. 7-13360), The coating layer has an average particle size of 1500 to
Latex having a gel content of not more than 60% at 3000 Å and an average particle diameter of 500 to 1
A method using a latex having a gel content of 30 to 90% at 500 Å (JP-A-2-26989).
7) A method has been proposed 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, followed by soft calendering. In each of these, latex having a low gel content is used for the undercoat layer.

[0004]

However, when a coating liquid of latex having a low gel content is used in a film transfer type coating apparatus, for example, a gate roll coating method, and a coating liquid is coated on base paper at a high speed. The latex gums up due to the shearing force applied between rolls with different roll diameters and peripheral speeds, such as between the inner roll and the outer roll or between the inner roll and the applicator roll, and the coagulated material adheres to the roll surface. Therefore, there was a problem that the operability was reduced.

[0005] Further, the blade coating method usually used for high-speed coating also has a problem that when the operating speed is simply increased, troubles such as stalagmite and bleeding tend to occur. Staglamite is a dried stalagmite-like collar agglomerate that forms on the blade tip during coating, and bleeding is wet aggregate that occurs over the entire blade edge, with stalagmite further deteriorated. These agglomerates are transferred from the blade edge to the surface of the coated paper, causing quality defects such as partial coating unevenness and coating streaks.

As described above, by using the film transfer system for the undercoating coating solution and the blade system for the overcoating coating solution, the coating for rotary offset printing which is excellent in high-speed operability and blister resistance is excellent. No paper was obtained.

In view of such circumstances, an object of the present invention is to provide a coated paper for rotary offset printing which is excellent in high-speed operability and excellent in blister resistance of the coated paper.

[0008]

The present inventors have conducted intensive studies to solve these problems, and as a result, in a coated paper for rotary offset printing, in which a base paper is coated twice with a coating liquid,
An undercoat pigment coating liquid containing a copolymer latex selected from styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer or a modified product thereof having a gel content of 75 to 90% on a base paper by a film transfer method. After coating, the gel content is 30 to
The present invention is achieved by applying a topcoat pigment coating liquid containing a copolymer latex selected from a styrene-butadiene copolymer, a styrene-butadiene-acrylic copolymer or a modified product thereof at 60% by a blade method. It came to be. Particularly, when the base paper is coated at a high speed of 1000 m / min or more using a film transfer system such as a gate roll or a blade metalling size press as a system for applying the undercoat pigment coating solution, the gel content is 75 to 90.
%, It was confirmed that the mechanical stability of the latex could be maintained, there was no gum up between rolls, and the operability was excellent. On the contrary, when the gel content is less than 75%, the mechanical stability of the latex is inferior, and the phenomenon of gum up between the rolls is observed, whereby the operability is reduced. Does not function as an agent.

Next, the gel content of the topcoat pigment coating liquid is 30 to
A coating solution containing a copolymer latex selected from a styrene-butadiene copolymer, a styrene-butadiene-acrylic copolymer or a modified product thereof, which is 60%, is coated at 1000 m / min by a blade method. The coating liquid has a low viscosity under the above-mentioned high shearing rate, has excellent staglamite and high-speed operability without occurrence of bleeding, and also has excellent quality in terms of blister resistance after coating and printing surface strength. . The high-speed operability correlates with the fluidity of the coating liquid at a high shear rate, and the lower the viscosity of the coating liquid at a high shear rate, the better. Using a latex having a gel content of less than 30% results in reduced printing surface strength and a 60%
If it exceeds the above, blister resistance was reduced. The average particle size of the latex is preferably from 500 to 1100 angstroms, and particularly preferably from 600 to 1000 angstroms. The average particle size of the latex is 50
If it is less than 0 angstroms, the printing surface strength tends to decrease due to the effect of the emulsifier, and if it exceeds 1100 angstroms, the viscosity of the coating liquid at a high shear rate tends to increase, resulting in poor operability at high speed.

In the present invention, in addition to the latex described above, oxidized starch, esterified starch, enzyme-modified starch, and those obtained by flash-drying them are used to maintain the water retention of the coating layer and increase the internal bond strength of the base paper. A natural adhesive such as cold water-soluble starch, casein, and soy protein obtained by the above method may be used in combination.

Regarding the pigment, in the case of the undercoat coating liquid, kaolin, light calcium carbonate, heavy calcium carbonate, clay, satin white, talc, titanium oxide, silica,
Zinc oxide, aluminum hydroxide, plastic pigment and the like are used, but it is preferable to use inexpensive heavy calcium carbonate or light calcium carbonate in terms of cost. Further, with respect to the overcoating liquid, it is necessary to mix heavy calcium carbonate in an amount of 50% by weight to 70% by weight based on the total pigment in view of high-speed operability and other qualities .
If the amount of heavy calcium carbonate is less than 50% by weight, the viscosity of the coating liquid under a high shear rate becomes high, stalagmite and bleeding are likely to occur, the high-speed operability is poor, and the compounding amount of heavy calcium carbonate is 70% by weight. Exceeds the high-speed fluidity, excellent operability, and has excellent blister resistance due to the formation of a coating layer with good air permeability. Surface properties such as degree, gloss after printing, smoothness and surface feeling are reduced. The average particle size of the heavy calcium carbonate is 0.1.
It is preferably from 3 to 0.9 μm, particularly preferably from 0.4 to 0.7 μm. If it is smaller than 0.3 μm, the viscosity of the coating liquid at a high shear rate becomes high, and high-speed operability is poor. If it exceeds 0.9 μm, the surface properties such as white paper glossiness, smoothness and surface feel of the product are reduced. descend.

The composition of the latex used in the undercoating and topcoating pigment coating solutions may be a styrene / butadiene copolymer, a styrene / butadiene / acrylic copolymer, or a modified product thereof, which are generally used. Also,
The optimum amount of the latex in the undercoating layer varies depending on the pigment to be used, but it is preferable to use the latex in the range of 3 to 8% by weight based on the total pigment. The latex content of the overcoat layer also varies depending on the pigment used,
It is desirable to use it in the range of 7 to 12% by weight based on the total pigment.

The coating liquid of the present invention contains a dispersant, a thickener,
Various auxiliaries which are blended with ordinary pigments for coated paper, such as a water retention agent, an antifoaming agent, and a water resistance agent, are used. The base paper used is a basis weight of 30 to 200 g / m used for general coated paper for printing.
^2. Paper-based or board-based base paper is used.

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

[0015]

In the present invention, the undercoat pigment coating liquid is coated by a film transfer type coating apparatus. By using latex having a gel content of 75 to 90%, the coating liquid is subjected to strong shearing force. No gum up phenomenon is observed. This is because latex has excellent mechanical stability.

On the other hand, with respect to the topcoat pigment coating liquid, a latex having a gel content of 30 to 60% is coated by a blade method. However, when a latex having a low gel content is used, the fluidity at high temperatures is good and the lower temperature is lower. Under the conditions, it becomes soft and melts, so steam easily escapes and the coating layer becomes porous.
A coated paper for rotary offset printing having excellent blister resistance can be obtained. It should be noted that high-speed operability and blister resistance have excellent effects for the first time by providing specific upper and lower layers using such a manufacturing method.

[0017]

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) Gel content of latex About 0.3 g of latex was 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 through a glass filter, and the filtrate is dried with a dryer at 105 ° C., and the weight of the toluene-soluble component 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−toluene soluble weight) × 100 / (dry film weight) (2) Average particle size of heavy calcium carbonate Using a light transmission type particle size distribution analyzer SHC5000 of Seishin Enterprise The 50% point of the weight cumulative distribution was defined as the average particle size.

(3) A sample diluted to a latex average particle diameter of 0.05 to 0.2% is prepared, the absorbance at a wavelength of 525 nm is measured, and the absorbance is determined by a previously prepared calibration curve.

(4) Capillary Viscosity Value The overcoated pigment coating liquid was kept at 30 ° C., and the diameter was adjusted to 0.1 using a high pressure capillary viscometer HVA-6 manufactured by Anton Paar.
Shear rate 1 × using 4 mm, 10 mm long capillary
Viscosity value measured under the condition of 10 ⁶ sec ^-1 . The lower the viscosity value, the better the high-speed fluidity.

(5) Blank glossiness Measured at an angle of 75 ° according to JIS P-8142.

(6) Gloss after printing Using an RI-II type printing machine (manufactured by Meisho Seisakusho), ink for Sakata ink offset printing (trade name: Diatone GSL)
Red) and printed at a constant 0.35 cc. After standing overnight, the glossiness at 75 ° was measured.

(7) Smoothness JAPAN Tappi No5 Measured with an Oken-type smoothness tester.

(8) Printing surface strength Using an RI-II type printing machine (manufactured by Meisho Seisakusho), using Toyo Ink's TV-24, printing at a constant 0.35 cc, and visually checking the degree of picking on the printing surface. Was relatively evaluated. ◎ = not generated at all, ＝= not generated at all △ = generated, × = remarkably generated

(9) Blister resistance Using a RI-II type printing machine (manufactured by Meisho Seisakusho), using TK Mark V New 617 manufactured by Toyo Ink, printing at a constant 0.8 cc, and controlling the temperature between hair dryers. It was heated with different hot air for 3 seconds, and the degree of blisters generated was visually evaluated relative to each other.

◎ = Not generated at all, ほ と ん ど = Not generated at all △ = Produced, × = Remarkably generated.

(10) Evaluation of generation of staglamite The generation of staglamite at the time of coating the topcoat pigment was visually judged.

◎ = No occurrence, ＝= Almost no occurrence Δ = Yes, × = Notable occurrence.

(11) Evaluation of Gum-Up Occurrence The occurrence of gum-up at the time of coating the pigment with the undercoat gate roll was visually determined.

◎ = No occurrence, ＝= Almost no occurrence Δ = Yes, × = Notable occurrence.

(12) Evaluation of Streak Occurrence Streak occurrence was visually determined when the topcoat pigment was applied.

◎ = Not generated at all, ほ と ん ど = Not generated at all △ = Produced, × = Remarkably generated.

Example 1 0.3 parts of sodium polyacrylate dispersant was added to 100 parts of heavy calcium carbonate having an average particle diameter of 1.2 μm, and dispersed in water using a Cowles disperser. Then, a pigment dispersion having a solid content of 65% was prepared. 17 parts of oxidized starch and 5 parts of a styrene-butadiene copolymer latex having a gel content of 80% and an average particle size of 1300 angstroms are mixed with the dispersion as an adhesive, and an undercoat pigment coating liquid having a solid content of 55% is prepared. Prepared. Further, to 60 parts of heavy calcium carbonate having an average particle diameter of 0.5 μm and 40 parts of kaolin, 0.3 part of a sodium polyacrylate-based dispersant was added, and dispersed in water using a Cowles disperser. A pigment dispersion having a solid content of 67% was prepared. 5 parts of oxidized starch and 10 parts of a styrene-butadiene copolymer latex having an average particle diameter of 900 Å and a gel content of 50% as an adhesive were mixed with the dispersion, and a topcoat pigment coating liquid having a solid content of 65% was added. Prepared.

The coating liquid was bleached to a hardwood having a basis weight of 54 g / m ² , and the kraft pulp blended base paper was coated on the base paper using a high-speed gate roll coater as an undercoating apparatus.
5 g / m ² per side of undercoating coating liquid at 00 m / min
After the double-side coating, a high-speed blade coater was used as a top-coating apparatus, and a top-coating coating solution was coated at 8 g / m ² on one side at a coating speed of 1200 m / min. In addition, 12
Gloss finishing was performed using a stepped super calender.

Example 2 When preparing an undercoat coating liquid,
A coated paper was produced in the same manner as in Example 1 except that a styrene / butadiene copolymer latex having a gel content of 87% and an average particle size of 1300 Å was used.

Example 3 In preparing a topcoat coating solution,
A coated paper was produced in the same manner as in Example 1 except that a styrene / butadiene copolymer latex having a gel content of 40% and an average particle diameter of 700 Å was used.

Example 4 In preparing a topcoat coating solution,
A coated paper was produced in the same manner as in Example 1 except that a styrene / butadiene copolymer latex having a gel content of 50% and an average particle diameter of 550 Å was used.

[Comparative Example 1] When preparing an undercoat coating liquid,
A coated paper was produced in the same manner as in Example 1 except that a styrene / butadiene copolymer latex having a gel content of 50% and an average particle diameter of 1300 Å was used.

[Comparative Example 2] In preparing a topcoat coating solution,
A coated paper was produced in the same manner as in Example 1, except that a styrene / butadiene copolymer latex having a gel content of 80% and an average particle diameter of 1000 Å was used.

[Comparative Example 3] When preparing an overcoating liquid,
A coated paper was produced in the same manner as in Example 1, except that a styrene / butadiene copolymer latex having a gel content of 20% and an average particle size of 1000 Å was used.

The results are shown in Table 1.

[0043]

[Table 1]

[0044]

The base paper is coated with a latex of a styrene / butadiene copolymer having a gel content of 75 to 90% as a base coat pigment coating liquid by a film transfer method, and then as a top coat pigment coating liquid. Gel content 30-60
% Styrene-butadiene-based copolymer is coated by a blade method to produce coated paper that is suitable for rotary offset printing, has excellent high-speed operability, and has good printing properties in addition to blister resistance. Excellent surface properties such as surface strength, gloss after printing, and smoothness.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-269897 (JP, A) Japan Pulp and Paper Technology Association, “Paper Pulp Manufacturing Technology Series (8) Coating”, First Edition, Japan Paper Pulp Technology Association, 1993 August 17, p. 98-99 (58) Field surveyed (Int. Cl. ⁶ , DB name) D21H 19/58 D21H 19/82

Claims (4)

(57) [Claims] 1. A method for producing a coated paper for rotary offset printing wherein a base paper is coated with a coating liquid twice, wherein the gel content is 75%.
An undercoat pigment coating solution containing a copolymer latex selected from a styrene-butadiene copolymer, a styrene-butadiene-acryl copolymer or a modified product thereof of about 90% is prepared, and this undercoat pigment coating solution is prepared. After being coated on the surface of the base paper by a film transfer method, a copolymer selected from a styrene / butadiene copolymer, a styrene / butadiene / acrylic copolymer or a modified product thereof having a gel content of 30 to 60% prepared separately. A method for producing a coated paper for rotary offset printing, comprising applying a topcoat pigment coating liquid containing coalesced latex by a blade method. 2. In a coated paper for rotary offset printing having two coating layers, the undercoat pigment coating layer has a gel content of 7%.
It contains a copolymer latex selected from 5-90% of styrene-butadiene copolymer, styrene-butadiene-acrylic copolymer or a modified product thereof, and has a gel content of 30-60% in the overcoated pigment coating layer. Styrene
Contains a copolymer latex selected from butadiene copolymer, styrene-butadiene-acrylic copolymer or a modified product thereof , and 50 to 50% of all pigments in the overcoat pigment coating layer.
A coated paper for rotary offset printing, wherein 70% by weight is heavy calcium carbonate . 3. The coated paper for rotary offset printing according to claim 2, wherein the average particle size of the copolymer latex in the top-coat pigment coating layer is 500 to 1100 angstroms. 4. The heavy calcium carbonate has an average particle size of
3. The structure according to claim 2, wherein the thickness is 0.3 to 0.9 μm.
Or the coated paper for rotary offset printing according to 3 .