JP3157044B2 - 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 novel coated paper for offset printing. More specifically, the present invention relates to a coated paper for offset printing having excellent suitability for offset printing, particularly high pick resistance.

[0002]

2. Description of the Related Art In recent years, the speed of coating printing, especially offset printing, has been increased, and coated papers that can withstand such printing have become necessary. In particular, high pick strength of coated paper that can withstand high-speed printing is required, and at the same time, the demand for reproducibility of image information in the market in recent years is also increasing, and high printing gloss and ink inking property are required. ing.

[0003] In response to these requirements, generally, the suitability for offset printing, particularly pick strength, can be improved by increasing the amount of an adhesive such as starch or synthetic polymer latex added. However, when the amount of starch added is greatly increased and the pick strength is improved, the viscosity of the coating liquid is significantly increased, and the suitability for coating with a coater is reduced. Therefore, it is necessary to lower the concentration of the coating liquid. . As a result, the gloss of white paper and the gloss after printing are reduced, and the adhesive layer forms a film, so that the inking property of the offset printing ink is also reduced. Further, even when the amount of the synthetic polymer latex added is greatly increased, the adhesive layer forms a film, and the inking property of the offset printing ink is reduced. This tendency is due to the fact that the base paper is anionic due to the hydroxyl groups and carboxyl groups of the pulp fibers, and the coating liquid is anionic due to the carboxyl groups of the adhesive, so that the adhesive in the coating liquid permeates the base paper during coating. Encouraged by To prevent this, some measures have been taken to improve the water retention of the coating solution. For example, a water-soluble polymer, such as carboxymethylated cellulose, which makes the aqueous solution extremely viscous may be added to the coating composition. However, the effect of such a water retention agent is limited, and the viscosity of the coating liquid increases, so that the concentration of the coating liquid at the time of coating may be reduced and printability may not be improved.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 1-97296, since the surface of the pulp fiber constituting the base paper is anionically charged, the polarity of the coating liquid is changed to cationic and the coating on the base paper is performed. There is also a concept of preventing penetration of the liquid and improving suitability for offset printing. However, when the coating liquid is cationized in this manner, the viscosity of the coating liquid is considerably increased, and the coating density is rather lowered at the time of coating, and the printability may not be improved. In addition, when kaolin is used as a pigment, a large amount of a cationizing agent must be used to block an anionic group, which not only increases the cost but also deteriorates the liquid property. For this reason, calcium carbonate or the like becomes the main component of the pigment, and as a result, the gloss of the white paper decreases.

Further, as disclosed in Japanese Patent Application Laid-Open No. 55-13735, the specific surface area is reduced to 1% by mechanical treatment.
Although there is a concept of using one or more kinds of pigments treated with a cationic polyelectrolyte on the surface of the inorganic pigment which has been activated by increasing the above, only the same problem as in the case of JP-A-1-97296 is included. No pigment slurry concentration of 50%
When it is increased above, the viscosity is remarkably increased, and the coating suitability is remarkably deteriorated. Therefore, the coating is performed at a low concentration, and the gloss of white paper and the gloss of printing are reduced.

[0006] Further, by forming a coating layer by performing multi-layer coating, the printability of the overcoat layer can be improved and the production efficiency can be increased. For this reason, multilayer coated paper, especially double coated paper, has become widespread. However, in the case of multi-layer coating, since both the undercoating liquid and the base paper are anionic, a large amount of adhesive or the like penetrates the base paper from the coating liquid of the undercoat layer closest to the base paper, and the coating amount of the undercoat layer is small. Therefore, a large amount of adhesive is required for the undercoat layer. Also, since a large amount of adhesive is blended into the undercoat layer, the adhesive of the undercoat layer forms a film that is difficult to transmit gas,
Blister problems are likely to occur during web offset printing. When undercoating is performed with a roll coater such as a gate roll coater, the indentation pressure of the coating liquid is reduced,
This tendency becomes remarkable. If the adhesive of the undercoat layer is mainly composed of a water-soluble polymer such as starch, and is blended in a large amount, the viscosity of the coating liquid will increase significantly, making it difficult to coat with a coater, and the amount of the adhesive to be blended will be limited. Thus, a large amount of expensive synthetic high-polymer latex, which has little effect on the viscosity of the coating liquid, is required.

[0007]

In view of this situation, an object of the present invention is to provide a multi-layer coated paper having high offset printing suitability, especially high pick resistance and excellent coating suitability, and excellent operability. And to get to.

[0008]

Means for Solving the Problems The coated paper for offset printing of the present invention is a coated paper for offset printing provided with two or more coating layers per one side of the base paper. The composition comprises a pigment slurry and a cationic binder, and the pigment slurry contains a cationic water-soluble polymer and a nonionic water-soluble polymer containing at least 20% of a tertiary amine or a quaternary ammonium base in a pigment, 0.02 to 0.5 parts by weight, 0.1 to 1.5 parts by weight are added to 100 parts by weight of the pigment, and the average particle diameter is 1.1 to 5.0 μm by wet pulverization. In addition, 80% by weight of the pigment is calcium carbonate.

Further, in the coated paper for offset printing of the present invention, the nonionic water-soluble polymer is characterized by using at least one selected from polyethylene oxide, polyvinyl alcohol, hydroxyethyl cellulose and hydroxyethylated starch. Things.

In the undercoat layer coating composition applied to the present invention, when the proportion of calcium carbonate in the pigment is less than 80%, the viscosity of the coating liquid increases significantly, and fine aggregates are formed in the coating liquid. It is easy to occur. For this reason, coating aptitude decreases,
The strength of the coated layer after coating is also significantly reduced. In the present invention,
The calcium carbonate used is, for example, dry-ground heavy calcium carbonate, calcite-based light calcium carbonate,
Aragonite light calcium carbonate and the like.

The cationic water-soluble polymer used in the present invention may be a tertiary amine or quaternary ammonium base, such as vinyltrimethylammonium chloride monomer, 2-methacryloyloxyethyltrimethylammonium chloride monomer, N-acrylamidoethyltrimethylammonium chloride monomer, It is necessary to contain 20% or more of a cationic monomer such as an acrylamide / diallylamine copolymer monomer. If the amount is less than 20%, the viscosity of the coating liquid increases, and the effect of improving the coating layer strength cannot be obtained. On the other hand, if the amount added to 100 parts by weight of the pigment is less than 0.02 parts by weight,
The slurry viscosity increases remarkably, making wet pulverization difficult and making it impossible to keep the average particle size to a required level. Also, 0.
If it exceeds 5 parts by weight, the viscosity will increase significantly, which is not preferable.

If the amount of the nonionic water-soluble polymer used in the present invention is less than 0.1 part by weight based on 100 parts of the pigment, the viscosity of the pigment slurry increases, making it difficult to wet-pulverize and keeping the average particle diameter at a required level. In addition, the pigment is detached in a drying step after coating, which causes paper dust. On the other hand, if the amount exceeds 1.5 parts by weight, the viscosity increases significantly, and the efficiency of wet pulverization decreases. As the nonionic water-soluble polymer, polyvinyl alcohol, polyethylene oxide, hydroxyethyl cellulose, hydroxyethylated starch, starch, dextrin, dextran, polyacrylamide and the like can be used, but polyvinyl alcohol, polyethylene oxide, hydroxyethyl cellulose, hydroxyethylated starch can be used. Is desirable. Particularly desirable is polyvinyl alcohol.

If the average particle diameter of the pigment slurry after the wet pulverization exceeds 5.0 μm, the pigment is remarkably detached in a drying step after coating, and the roll in the step becomes dirty. 1.1
If it is less than μm, it becomes difficult to obtain a coating layer strength.

The cationic binder of the present invention comprises a cationized starch, a cationized acrylic emulsion, a cationized styrene-butadiene latex, a cationized ethylene-vinyl acetate copolymer, a cationized styrene-acrylic copolymer, a cationized vinyl acetate- Acrylic copolymer,
Cationized butadiene-methyl methacrylic copolymer, cationized vinyl acetate-butyl acrylate copolymer, cationized polyvinyl alcohol, cationized soy protein and the like, and particularly preferable are cationized starch and cationized acrylic emulsion. is there. As a raw material of the cationic starch, corn starch, tapioca, potatoes and the like can be used, and the cationization is performed by using 2-diethylaminoethyl chloride or the like to make a tertiary amine type.
Alternatively, the quaternary ammonium salt is prepared by reacting 2,3 epoxypropyltrimethylammonium chloride or the like.

By using the coating composition of the present invention as an undercoat layer on the finished base paper, the adhesive strength between the base paper and the undercoat layer and the strength of the undercoat layer itself are increased. Furthermore, since various anionic water-soluble adhesives and the like are contained in the composition of the top coat composition of the coated paper for offset printing, the top coat composition is solidified at the interface with the undercoat layer. In addition, the adhesive strength between the overcoat layer and the undercoat layer increases. As described above, since the printing coated paper of the present invention has a high pick strength, the amount of the adhesive compounded in the undercoat coating composition can be reduced. Furthermore, by cationizing the undercoat layer,
Since the porosity of the undercoat layer is increased and the air permeability is increased, the blister resistance during offset rotary printing is further improved.

Other adhesives used in the present invention include synthetic binders such as polyvinyl alcohol, oxidized starch, etherified starch, esterified starch, enzyme-modified starch, cold-water-soluble starch obtained by flash-drying them, and casein. And natural adhesives such as soybean protein, and those obtained by cationizing these adhesives. These may also be used as required, such as dispersants, thickeners, water retention agents, defoamers, water resistant agents,
A variety of commonly used auxiliaries such as coloring agents, or cations of these auxiliaries can be used as appropriate.

As the pigment used in the present invention, kaolin,
Calcium carbonate, clay, satin white, talc, titanium oxide, aluminum hydroxide, silica, calcined kaolin, zinc oxide, activated clay, acid clay, silicon clay, lake,
Plastic pigments and the like are mentioned, but a cationic dispersant is required for dispersion, and in some cases, it is necessary to add a low molecular weight cationic activator to block an anionic group.

The base paper used in the present invention is LBKP, N
Chemical pulp such as BKP, GP, PGW, RMP, TM
Mechanical pulp such as P, CTMP, CMP, CGP, DIP
Includes various pulp such as waste paper pulp, etc., various fillers such as light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, etc., sizing agent, fixing agent, retention agent, cationizing agent, paper strength agent, etc. Containing various additives, acidic,
Neutral and alkaline papermaking. As the base paper of the present invention, a base paper that is size-pressed with a no-size press base paper, starch, polyvinyl alcohol, or the like is used.

The method of applying the coating composition according to the present invention to base paper is not particularly limited, and various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, short dwell coaters can be used. And the like, using two or more ordinary coating devices. The coated paper is dried every time each layer is coated, or after two or more layers are continuously coated. Coated and dried coated paper is super calendar, gloss calendar,
Perform soft calendar processing and the like.

[0020]

EXAMPLES Hereinafter, the effects of the present invention will be described in more detail using examples, but the present invention is not limited thereto. In the examples, "parts" and "%" indicate "parts by weight" and "% by weight", respectively.

The method for evaluating the coated paper for offset printing of the present invention is described below. 1) Average particle size: The volume-weighted average particle size was measured with a Microtrac 7995-30 SPA model manufactured by Lee & Northrop. 2) Viscosity: using a B-type viscometer at a temperature of 25 ° C. and 60 rpm
Measured under conditions of m. 3) White paper glossiness: measured at an angle of 75 degrees according to JISP8142. (Unit:%) 4) Multi-color printing glossiness: A sample was printed with a Roland offset printing machine, left at room temperature for 24 hours, and the four-color solid printing portion of black, magenta, cyan, and yellow of the sample was printed. Gloss was measured at an angle of 60 degrees.
(Unit:%) 5) Pick strength: IP using RI printing machine (Meiji Seisakusho)
Printing was performed using I ink, and the degree of picking on the printed surface was visually determined. 5 is the best level on a 5-point scale. The permissible limit is rank 3. 6) Blister resistance: A commercially available ink for rotary offset printing is printed on both sides of the test piece with an RI printing machine, and the test piece is wrapped with aluminum foil, placed in silicon oil at 300 ° C. for 5 seconds, and the blister is discharged. Was visually determined. 5
On a scale of 5, 5 is the best level. 7) Degree of detachment of the pigment: Five levels of evaluation were made on the degree of contamination of the roll in the drying step after the application of the undercoating liquid and the like, and rank 5
Was the highest standard. The permissible limit is rank 3.

Examples 1 to 7 and Comparative Examples 1 to 6 1. Base paper composition LBKP (filtration 350mlcsf) 30 parts NBKP (filtration 420mlcsf) 70 parts Internal additives Calcium carbonate (* expressed by ash content in base paper) * 10 parts Commercially available alkyl ketene dimer-based internal sizing agent (AKD) 0.03 parts Commercially available cationic polyacrylamide retention aid 0.03 parts Above 1 and 2 A pulp slurry is prepared by mixing
A base paper having a basis weight (absolutely dry) of 0 g / m ² was prepared. Using a gate roll coater, the base paper was coated with a coating amount of 3 g / m ² per one side at a coating liquid concentration of 49% with the composition shown in Tables 1 to 3 and dried.

3. Preparation of Wet-Pulverized Pigment Slurries of Examples and Comparative Examples As calcium carbonate before pulverization, A grade (specific surface area: 7000 cm ² / g) manufactured by Sankyo Seiko Co., Ltd. was used. Was. A) (Trimethyl ethyl ammonium chloride) methacrylate monomer: acrylamide = 90:
10) B) (trimethyl ethyl ammonium chloride) methacrylate monomer: vinyl alcohol = 3
Copolymer having a composition of 0: 70% C) (trimethyl ethyl ammonium chloride) methacrylate monomer: acrylamide = 10:
The following three types of nonionic water-soluble polymers having a composition of 90 were used. D) Polyvinyl alcohol (Poval 105 manufactured by Kuraray) E) Polyethylene oxide (PEO500 manufactured by Iron and Steel Chemical)
0) F) Commercially available polyacrylamide (molecular weight 10,000) Wet grinding mill is Agitator Mill L manufactured by Ashizawa Co., Ltd.
Using the ME20 type, the grinding conditions were as follows: bead filling rate 80%,
960 rpm, zirconia beads (average diameter 1.0
mm), the processing was performed under the conditions of a processing flow rate of 3.5 l / min, with the pigment slurry having a solid content of 65%. Example 7 is 2
Pass processing, Comparative example 5 is 3-pass processing, Comparative example 4 has a flow rate of 5
1 / min.

Formulation of Undercoat Coating Solution Kaolin was Ultracoat manufactured by Engelhardt Co., and latex was a commercially available cationized acrylic emulsion (SFC54 manufactured by Dainippon Ink and Chemicals, Inc.). Cationized starch is made from corn and has a 10% solution viscosity of 20 at 30 ° C.
A CPS quaternary ammonium alkylated starch having a substitution degree of 0.04 was used. The number of binders is as follows. Cationized acrylic emulsion 15 parts Cationized starch 15 parts

A coating liquid having a solid content of 60% and having the following composition was applied to one side of the undercoated paper by a blade coater.
3 g / m ^{2 was} applied and dried. Top coating liquid formulation Commercial primary kaolin (Ultra White 90) 30 parts Commercial secondary kaolin (Ultra Coat) 40 parts Commercial wet heavy calcium carbonate (Carbital 90) 30 parts Commercial polyacrylic dispersant 0.1 part Commercial phosphoric acid Esterified starch 4 parts Commercial styrene butadiene latex (JSR0617) 12 parts Calcium stearate 0.3 parts Sodium hydroxide 0.15 parts The produced coated paper was subjected to a super calender treatment under the following conditions.

Super calendar condition Number of stages 10 stages Rigid rolls Chilled rolls, outer diameter 400 mm Elastic roll Cotton rolls, outer diameter 420 mm Processing speed 400 m / min Linear pressure 220 Kg / cm Subsequently, when coating the overcoat layer, The coating method and the super calender conditions were the same as the above conditions. Tables 1 to 3 summarize the results of the examples and comparative examples.

Comparative Example 7 A base paper coated under the same composition and production conditions as in Examples 1 to 7 was coated with the following undercoat coating solution at a coating amount of 4 g / m ² per side by a gate roll coater. Dried. Mixing of undercoating liquid Using dry heavy calcium carbonate (Escalon 1500 manufactured by Sankyo Seiko Co., Ltd.) as a pigment, without wet grinding,
Except that only a cationic dispersant was used as the dispersant, it was prepared in the same manner as in Example 1. Calcium carbonate (Escalon 1500 manufactured by Sankyo Seiko Co., Ltd.) 100 parts Cationic dispersant A 0.6 part After applying the above undercoating liquid, the same topcoat coating liquid formulation and coating method as in Examples 1 to 10 are applied. An overcoat layer was applied and treated under the same supercalender conditions. Table 3 summarizes the quality characteristics of Comparative Example 7. Compared with Example 1, the degree of pigment detachment was remarkable.

Comparative Example 8 Using base paper made under the same composition and production conditions as in Examples 1 to 7, the following undercoating coating solution was applied by a gate roll coater at a coating amount of 4 g / m ² per side. And dried. Formulation of undercoat coating liquid Calcium carbonate (Escalon 1500, manufactured by Sankyo Seiko Co., Ltd.) 100 parts Commercial polyacrylate dispersant 0.6 parts Commercial styrene butadiene latex (Nippon Synthetic Rubber 0617) 15 parts Commercial phosphorylated ester ( 15 parts of MS4600 manufactured by Nippon Shokuhin Kako Co., Ltd. 15 parts of the paper coated with the undercoat layer described above were coated with the overcoat layer by the same coating method as in Examples 1 to 7, and processed under the same supercalender conditions. gave. Table 3 shows the quality characteristics.
Summarized in Comparative Example 8 has a lower pick strength than Example 1 and is at a level that cannot withstand offset printing.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

As is clear from the examples, according to the present invention, a coated paper for offset printing having high suitability for offset printing, particularly excellent pick resistance, could be obtained.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) D21B 1/00-1/38 D21C 1/00-11/14 D21D 1/00-5/28 D21F 1/00-13 / 12 D21G 1/00-9/00 D21H 11/00-27/42 D21J 1/00-7/00

Claims (2)

(57) [Claims] 1. An offset printing coated paper provided with two or more coating layers per one side of a base paper, wherein a coating composition of an undercoat layer closest to the base paper comprises a pigment slurry and a cationic binder, The slurry is prepared by adding a cationic water-soluble polymer and a nonionic water-soluble polymer each containing 20% or more of a tertiary amine or a quaternary ammonium base to the pigment in an amount of 0.02 to 0.5 with respect to 100 parts by weight of the pigment. 0.1 to 1.5 parts by weight, an average particle diameter of 1.1 to 5.0 μm by wet pulverization, and 80% by weight of the pigment is calcium carbonate. Coated paper for offset printing. 2. The coating for offset printing according to claim 1, wherein the nonionic water-soluble polymer is at least one selected from the group consisting of polyethylene oxide, polyvinyl alcohol, hydroxyethyl cellulose, and hydroxyethylated starch. Papermaking