JP3328922B2 - Coated paper for 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 coating material for offset printing which is excellent in high-speed operability when coating a base paper with an undercoating liquid, and which is excellent in surface condition after printing, top surface strength and the like. The present invention relates to a method for producing paper and its coated paper.

[0002]

2. Description of the Related Art In recent years, demand for printing paper has tended to gradually increase. In particular, it is characterized by a steadily growing demand in the commercial printing field such as advertisements, mail order flyers, catalogs, pamphlets and the like. Unlike commercial printing and publishing, these commercial prints have low commercial value,
Since it is important for the purpose to be achieved as an advertising medium, low cost and good print finish are required.
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. It is important to increase productivity. 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, by coating the base paper with a base coat coating liquid containing a relatively inexpensive pigment on-machine, and then coating the base coat coating liquid, the coatability of the base paper is improved by the base coat in terms of quality. In addition, since the surface condition and the print 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 higher speed of a film transfer coating apparatus which is an on-machine coating method.

However, when an ordinary coating liquid is applied to base paper using a gate roll coater, a blade, or a rod metaling size press coater which is an on-machine coating method, the maximum operation speed at present is about 1100 m.
/ Min is the limit for speeding up. There are several factors that hinder this speed-up, such as a transfer pattern (hereinafter referred to as a “roll pattern”) caused by uneven transfer of the coating liquid to the roll or a mist at the exit of the application roll nip. There is a phenomenon called mist that scatters.
The mist starts to be generated even at a speed lower than 1100 m / min depending on the operating conditions. However, as the speed increases, the degree of the mist increases, causing a deterioration in the working environment. To fall into the product defect. In addition, especially in the case of a gate roll coater, a similar problem of mist generation occurs. In addition, the shearing force applied between the rolls having different roll diameters and peripheral speeds causes a phenomenon called gum-up in which the coating liquid solidifies and adheres to the roll surface, thereby reducing operability.

Further, the peeling at the exit of the application roll nip becomes unstable, and many peeling patterns occur. These problems can be reduced by lowering the coating solution concentration, but the drying load is increased, and the coating solution penetrates more into the base paper, and the base paper coatability is inferior.
There is a problem that gloss unevenness after overcoating is increased, and surface condition and printability are deteriorated.

[0006]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to use a film transfer method as described above, and particularly to a manufacturing process in which an undercoat is applied at a high coating speed of 1100 m / min or more. Another object of the present invention is to provide a coated paper for offset printing which is excellent in operability, which is a problem in the above, and which is excellent in quality after top coating.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned problems, and as a result, a coated paper for offset printing in which a base paper is coated twice with a coating liquid having a pigment and an adhesive. In the production method, after coating an undercoating coating liquid containing a styrene-butadiene copolymer latex having an average particle diameter of 40 to 70 nm on the surface of the base paper by a film transfer method, the average particle diameter is larger than 70 nm,
The present invention has been accomplished by applying an overcoating liquid containing a styrene / butadiene copolymer latex in the range of 110 nm or less by a blade method.

The present inventors have found that the problems of roll pattern, mist, release pattern and gum-up, which are more remarkably observed when the undercoating coating liquid is coated at a high coating speed of 1100 m / min or more, Correlation with the viscosity of the coating liquid under high shear rate showed that lowering the viscosity of the coating liquid under high shear rate was effective in solving these problems.

On the other hand, it is already known in the literature and the like that it is effective to reduce the latex particle diameter as one of the solutions for lowering the viscosity of a coating liquid under a high shear rate (see Chemical Society of Japan). , Symposium on Coating Technology, 199
3). However, the present inventors have conducted further intensive studies. As a result, when latex having an average particle diameter of 70 nm or less was used in the overcoating coating liquid, wet inking property (actual printing The ink density of the printing surface printed immediately after the dampening solution is applied on the press decreases, and the wet strength (the printing surface printed immediately after the dampening solution is applied during overprinting on the actual printing press) It was newly recognized that a problem of lowering the surface strength) occurred.

Based on the above findings, the present inventors have used latex having an average particle diameter of 40 to 70 nm in an undercoating coating liquid applied by a film transfer method, and used an average particle diameter in an overcoating coating liquid. Diameter greater than 70 nm, 110
It has been newly found that by using a latex within the range of nm or less, it is possible to produce a product having excellent high-speed operability at the time of undercoating and excellent print quality after overcoating.

When the average particle diameter of the latex used in the undercoating coating liquid is 70 nm or less, the viscosity of the coating liquid at a high shear rate can be reduced, and the roll pattern, peeling pattern, mist, gum Up can be greatly reduced. The reason for this is that since a latex with a very small particle size is used, the viscosity at high shear rates is low, the coating film is transferred uniformly to each roll, and the coating film is split from the rolls evenly and applied to paper. It is because it is covered. In addition, by using latex having a small particle size, the area of adhesion to the pigment in the coating layer increases, so that the dry strength (the printing strength of the printing surface during solid printing) improves. However, even in that case, if the average particle size is smaller than 40 nm, the wet strength is reduced due to the influence of the hydrophilic emulsifier incorporated during the production of the latex, regardless of the latex used in the overcoating liquid. Incidentally, the average particle diameter of the latex used in the undercoating coating liquid is more preferably 50 to 60 nm.

When the average particle diameter of the latex used in the overcoating liquid is 70 nm or less, the wet strength and the wet-coating property tend to decrease due to the effect of the hydrophilic emulsifier as described above. Becomes 70 nm
When it is larger, there is no problem with wet strength and wet inking property, and good quality is given. However, when it is larger than 110 nm, dry strength tends to decrease.

As described above, when the latex having a small particle diameter is used in the production of a single-layer coated paper, the wet strength and the wet-coating property, which may be a concern, can be changed to the multi-layer coating and the overcoat pigment coating liquid. The problem can be solved by using a latex having a larger average particle diameter than that used for the undercoat.
This is because wet strength and wet adhesion are affected by the hydrophilicity and void structure of the very surface layer of the coating layer, and when a latex with a large particle size is used for the upper layer of the coating layer, the compounding of the hydrophilic emulsifier Since the amount is small, the wet strength does not decrease, and the adhesion point with the pigment is small, so that a porous coating layer is formed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The pigment used in the present invention is not particularly limited, but is generally used for papermaking, such as heavy calcium carbonate, light calcium carbonate, kaolin, clay, talc, satin white, and plastic pigment. , Titanium dioxide and the like are used. However, as for the pigment used in the undercoating coating liquid, the average particle diameter is 0.5 to 0.5 in order to reduce the viscosity at a high shear rate as much as possible.
Heavy calcium carbonate of about 0.9μm is 70% of all pigments
It is preferable to mix the above.

The composition of the styrene / butadiene-based latex used in the present invention may be a commonly used styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer or a modified product thereof. , Styrene, butadiene, methyl methacrylate and other vinyl unsaturated carboxylic acid ester compounds,
Other vinyl compounds such as acrylonitrile, or vinyl unsaturated carboxylic acids such as acrylic acid and fumaric acid are used. Regarding the gel content of the latex, the latex used in the undercoating coating liquid is 7 from the viewpoint of preventing gum up.
It is preferably from 5 to 90%. The gel content of the latex used in the overcoating liquid is preferably 30 to 60% in order to obtain good printing surface strength and blister resistance. In addition, starches used as adhesives other than latex to maintain the water retention of the coating liquid and to increase the internal bond strength of the base paper include oxidized starch, esterified or etherified starch, enzyme-modified starch and the like. Use cold water soluble starch obtained by flash drying.

Further, the concentration of the undercoating coating liquid is more preferably 35 to 55% in terms of solid content. If it is lower than 35%, the viscosity at a high shear rate becomes too low, and the surface properties and printability of the product decrease. On the other hand, if it is higher than 55%, the viscosity at a high shear rate becomes too high. Roll patterns, peeling patterns, mist, and gum up easily occur.

In the present invention, as a film transfer type coating apparatus used for undercoating, a gate roll coater, a blade or a rod metering size press coater can be used. The blade coater used for the top coat may be either a roll application type or a fountain nozzle type. 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.

As the base paper, base paper having a basis weight of 30 to 100 g / m ² used for general coated paper for printing is preferable, and high quality paper and medium quality paper are selected and used according to the purpose.

The amount of the undercoating coating liquid applied is preferably in the range of ² to 8 g / m ^{2 as} a solid content per one side of the base paper. When the coating amount is less than 2 g / m ^{2, the} concentration of the coating liquid has to be greatly reduced due to limitations in the apparatus, and as a result, the coating properties of the base paper and the surface state are liable to be reduced. In the case of applying an amount of more than 8 g / m ² , it is necessary to increase the concentration of the coating liquid. In this case, it becomes difficult to control the amount of the coating on the apparatus, and at the same time, the surface roughness and roll pattern of the satin-like surface are reduced. This is because it easily occurs on the paper surface.

The pigment, adhesive composition, blending amount, coating amount, and the like of the overcoating liquid are not particularly limited, and generally used pigments and adhesives may be used. The coating liquid concentration is preferably from 60 to 68%, and the coating amount of the top coating liquid is usually 6% in solids per side.
１４14 g / m ² are preferred.

The coated paper which has been coated with the top coating liquid and dried,
Gloss is applied by a finishing process such as a super calendar and a soft calendar as usual.

[0022]

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. The quality evaluation method is shown below.

Quality Evaluation Method> (1) Latex Average Particle Size: A sample diluted to a concentration of 0.05 to 0.2% was prepared, the absorbance at a wavelength of 525 nm was measured, and the absorbance was determined by a previously prepared calibration curve. (2) Dry strength: RI-II type printing machine (Meiji Seisakusho)
And printing was performed at a constant ink amount of 0.35 ml using TV-24 manufactured by Toyo Ink Co., Ltd., and the degree of picking on the printing surface was visually evaluated relatively.

◎ = not generated at all, ＝= not generated at all, Δ = generated, × = remarkable generated (3) Wet strength: RI-I type printing machine (Meiji Seisakusho)
5 minutes after applying dampening water to the sample, using TK High Plus Red Ink (manufactured by Toyo Ink), printing at a fixed ink amount of 0.3 ml, and printing the print marks on the rubber roll on the transfer paper The images were manually transferred, and the degree of picking was visually evaluated relative to each other.

◎ = Not generated at all, ○ = Almost not generated, Δ = Produced, × = Remarkable generation (4) Wet inking property: Using a RI-I type printing machine (manufactured by Meiji Seisakusho), wet the sample 5 seconds after adding water, TK
Printing was carried out using High Plus Red Ink (manufactured by Toyo Ink) at a fixed ink volume of 0.3 ml, and the ink density of the printed matter was measured. The higher the value, the better.

(5) Evaluation of release pattern occurrence: The occurrence state of the release pattern at the time of undercoating was visually judged.

＝= Not generated at all, ＝= Not generated at all, Δ = Produced, X = Remarkable generation (6) Mist generation evaluation: The state of mist generation during undercoating was visually judged.

＝= Not at all, ○ = Almost no occurrence, Δ = Yes, X = Severe occurrence (7) Evaluation of gum-up occurrence: The occurrence of gum-up at the time of undercoating was visually judged.

＝= Not generated at all, ほ と ん ど = Not generated at all, Δ = Produced, X = Remarkable generation (8) Blank paper surface: The unevenness of blank paper gloss was evaluated by visual observation.

◎ = No unevenness, ＝= Almost no unevenness, Δ = Some unevenness, X = Notable unevenness [Example 1] 90 parts of heavy calcium carbonate, kaolin 10
Parts of sodium polyacrylate dispersant was added to the mixture, and the mixture was dispersed in water using a Cowles dispersing machine. As an adhesive, 22 parts of a phosphorylated starch and an average particle size of 6 parts were added.
4 parts of a 5 nm styrene / butadiene copolymer latex was blended to prepare an undercoat coating liquid having a solid content of 45%.

Further, sodium polyacrylate-based dispersant 0.1 part with respect to 65 parts of heavy calcium carbonate and 35 parts of kaolin.
3 parts were added, dispersed in water using a Cowles disperser, and 4 parts of a phosphorylated ester starch as an adhesive and 10 parts of a styrene-butadiene-based copolymer latex having an average particle diameter of 95 nm were compounded, An overcoating liquid having a solid content of 65% was prepared.

Using a gate roll coater as a coating device for undercoating base paper containing bleached hardwood bleached kraft pulp having a basis weight of 54 g / m ² , the undercoat coating solution was applied at a coating speed of 1300 m / min. 4g / m ^{2 on} both sides and dried, then soft calendered (50 ° C, 80kg
/ Cm).

Further, a high-speed blade coater was used as a coating apparatus for top-coating, and a top-coating pigment coating liquid was coated on both sides at a coating speed of 1300 m / min at a solid content of 8 g / m ² on one side. Further, gloss finishing was performed using a 12-stage super currenter.

Example 2 In preparing an undercoating coating solution,
Using a styrene-butadiene-based copolymer latex having an average particle size of 50 nm and preparing a top coating liquid, except that a styrene-butadiene-based copolymer latex having an average particle size of 75 nm was used. A coated paper was produced as in Example 1.

Example 3 When preparing an undercoat coating liquid,
Using a styrene-butadiene-based copolymer latex having an average particle size of 60 nm and preparing an overcoating coating solution, except that a styrene-butadiene-based copolymer latex having an average particle size of 75 nm was used. A coated paper was produced as in Example 1.

Example 4 In preparing an undercoating coating solution,
Using a styrene-butadiene-based copolymer latex having an average particle size of 45 nm and preparing an overcoating coating solution, except that a styrene-butadiene-based copolymer latex having an average particle size of 105 nm was used. A coated paper was produced as in Example 1.

Example 5 In preparing an undercoat coating solution,
Using a styrene-butadiene-based copolymer latex having an average particle size of 55 nm and preparing a topcoat coating liquid, except that a styrene-butadiene-based copolymer latex having an average particle size of 95 nm was used. A coated paper was produced as in Example 1.

Comparative Example 1 When preparing an undercoating coating solution,
A coated paper was produced in the same manner as in Example 1, except that a styrene / butadiene copolymer latex having an average particle diameter of 35 nm was used.

Comparative Example 2 When preparing an undercoating coating liquid,
Using a styrene-butadiene-based copolymer latex having an average particle size of 100 nm and preparing a top coating liquid, except that a styrene-butadiene-based copolymer latex having an average particle size of 35 nm was used. A coated paper was produced as in Example 1.

[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 an average particle diameter of 60 nm was used.

Comparative Example 4 When preparing an undercoating coating solution,
Using a styrene / butadiene copolymer latex having an average particle size of 90 nm and preparing a top coating liquid, except that a styrene / butadiene copolymer latex having an average particle size of 100 nm was used. A coated paper was produced as in Example 1.

Comparative Example 5 When preparing an undercoat coating liquid,
Enzyme-modified phosphate esterified starch as starch
Example 1 except that 0 parts were used as an undercoating liquid having a solid concentration of 30% to prepare an overcoating liquid, and a styrene-butadiene copolymer latex having an average particle diameter of 150 nm was used when preparing an overcoating liquid. A coated paper was produced in the same manner as described above.

Comparative Example 6 When preparing an undercoating coating solution,
Using 18 parts of oxidized starch as a starch, 3 parts of a styrene / butadiene copolymer latex having an average particle diameter of 65 nm is blended, and using an undercoat pigment coating liquid having a solid concentration of 57%, a top coating liquid is used. A coated paper was produced in the same manner as in Example 1, except that a styrene / butadiene copolymer latex having an average particle diameter of 60 nm was used in the preparation.

The above results are shown in Tables 1 and 2.

[0045]

[Table 1]

[Table 2] As is clear from Tables 1 and 2, Examples 1 to 5 have excellent surface strength (dry strength and wet strength) and wet inking property, and have a peeling pattern even at a coating speed of 1300 m / min.
No mist or gum-up occurred, and the blank surface was good.

On the other hand, in Comparative Example 1, the wet strength and wet inking property were reduced. Comparative Example 2 has dry strength,
The wet strength and wet inking property were reduced, and further, a stripping pattern, mist, and gum up occurred during the operation, and the blank surface was reduced. In Comparative Example 3, the wet strength and wet inking property were reduced. In Comparative Example 4, the dry strength was reduced, and a peeling pattern, mist, and gum up occurred during operation, and the white paper surface shape was reduced. Comparative Example 5 has dry strength,
The surface of the blank paper decreased. In Comparative Example 6, the wet strength and wet inking property were reduced, and a peeling pattern, mist, and gum up occurred during operation, and the blank surface was reduced.

Therefore, the coated paper produced according to the present invention is excellent in surface strength and surface condition, and also excellent in high-speed operability, and its effect is extremely large.

[0048]

According to the present invention, a film transfer method is used,
In particular, while improving the operability, which is a problem in the manufacturing process of applying the undercoat at a high speed of 1100 m / min or more,
It is possible to obtain coated paper for offset printing excellent in quality after overcoating.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-148796 (JP, A) JP-A-8-158296 (JP, A) JP-A-7-316212 (JP, A) JP-A-5-148212 32711 (JP, A) JP-A-5-32710 (JP, A) JP-A-6-158597 (JP, A) WO 95/30049 (WO, A1) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) D21H 11/00-27/42

Claims (3)

(57) [Claims] 1. A coating liquid having a pigment and an adhesive on a base paper
In the method for producing a coated paper for offset printing to be coated twice, an undercoat coating liquid containing a styrene / butadiene copolymer latex having an average particle diameter of 40 to 70 nm is prepared, and this undercoat coating liquid is subjected to film transfer. After undercoating the surface of the base paper by the method, a topcoat coating liquid containing a styrene-butadiene copolymer latex having an average particle diameter separately prepared within a range of greater than 70 nm and 110 nm or less is coated by a blade method. A method for producing a coated paper for offset printing. 2. The method for producing coated paper for offset printing according to claim 1, wherein the undercoat is applied at a coating speed of 1100 m / min or more. 3. An offset printing coated paper comprising two coating layers having a pigment and an adhesive on a base paper, wherein the undercoating layer has an average particle diameter of 40 to 70 nm.
A coating for offset printing, comprising a butadiene-based copolymer latex, wherein the overcoat layer contains a styrene-butadiene-based copolymer latex having an average particle diameter of more than 70 nm and not more than 110 nm. Covered paper.