JPH0633397A - Coated paper for offset printing - Google Patents

Abstract

PURPOSE:To obtain coated paper for offset printing having high coated layer strength withstanding high-speed offset printing. CONSTITUTION:The coated paper for offset printing is obtained by coating base paper with an undercoating liquid containing a pigment slurry prepared by adding 0.02-0.5 pt.wt. cationic water-soluble polymer containing >=20% tertiary amine or quaternary ammonium base and 0.1-1.5 pts.wt. nonionic polymer to 100 pts.wt. pigment containing >=80% calcium carbonate therein, carrying out the wet pulverizing treatment and providing 1.1-5.0mum average particle diameter.

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, it relates to offset printing coated paper having excellent offset printing suitability, particularly high pick resistance.

[0002]

2. Description of the Related Art In recent years, the speed of coating printing, especially offset printing, has been increasing, and a coated paper capable of withstanding this has been required. In particular, the 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 has increased, and high printing gloss and ink receptivity are required. ing.

To meet these demands, offset printing suitability, particularly pick strength, can be improved by generally increasing the amount of adhesive such as starch or synthetic polymer latex added. However, if the amount of starch added is greatly increased and the pick strength is improved, the viscosity of the coating solution is significantly increased and the coating suitability in a coater is reduced, so it is necessary to reduce the concentration of the coating solution. . As a result, the glossiness of the white paper and the gloss after printing are lowered, and the adhesive layer forms a film, so that the ink receptivity of the offset printing ink is also lowered. 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 deteriorated. This tendency is because the base paper is anionic due to the hydroxyl and carboxyl groups of the pulp fiber, and the coating liquid is also anionic due to the carboxyl groups of the adhesive, so that the adhesive in the coating liquid penetrates into the base paper during coating. Facilitated by. In order to prevent this, some measures have been taken to improve the water retention of the coating liquid. For example, a water-soluble polymer such as carboxymethyl cellulose that makes the aqueous solution extremely high in viscosity may be added to the coating composition. However, the effect of such a water retention agent is limited, and since the viscosity of the coating liquid increases, the concentration of the coating liquid during coating may rather decrease and the printability may not improve.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 1-97296, since the surface of pulp fiber constituting the base paper is anionically charged, the polarity of the coating liquid is set to be cationic to apply the base paper. There is also an idea to prevent the permeation of the liquid and improve the offset printing suitability. However, when the coating liquid is cationized in this way, the viscosity of the coating liquid is considerably increased, the coating density is rather lowered during coating, and printability may not be improved. Further, when kaolin is used as a pigment, a large amount of a cationizing agent must be used in order to block an anion group, so that not only the cost increases but also the liquidity deteriorates. For this reason, calcium carbonate or the like becomes the main component of the pigment, and as a result, the glossiness of the white paper becomes low.

Further, as disclosed in JP-A-55-13735, a specific surface area of 1% is obtained by mechanical treatment.
There is also a concept of using one or more kinds of pigments treated with a cationic polyelectrolyte on the surface of the inorganic pigments which are activated by increasing the number of the pigments, but the same problem as in JP-A-1-97296 is included. No, the pigment slurry concentration is 50%
When the amount is increased above, the viscosity is remarkably increased and the coating suitability is remarkably deteriorated, so that the coating is performed at a low concentration, and the glossiness of white paper and the printing gloss are deteriorated.

Further, by forming a coating layer by performing multi-layer coating, the printability of the top coating layer can be improved and the production efficiency can be increased. For this reason, multilayer coated paper, especially double coated paper, has become popular. However, in the case of multi-layer coating, both the undercoating liquid and the base paper are anionic, so a large amount of adhesive etc. penetrates into 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. Further, since a large amount of the adhesive is mixed in the undercoat layer, the adhesive of the undercoat layer forms a film that is difficult to permeate gas,
Blister problems are more likely to occur during offset rotary printing. When the undercoat is applied with a roll coater such as a gate roll coater, the pressing pressure of the coating liquid becomes small,
This tendency becomes remarkable. When the adhesive for the undercoat layer is mainly composed of a water-soluble polymer such as starch and is mixed in a large amount, the viscosity of the coating solution is significantly increased, coating with a coater becomes difficult, and the blending amount of the adhesive is limited. Therefore, it is necessary to blend a large amount of expensive synthetic polymer latex, which has little influence on the viscosity of the coating liquid.

[0007]

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

[0008]

The coated paper for offset printing of the present invention is a coated paper for offset printing in which two or more coating layers are provided on one side of the base paper, and the undercoat layer closest to the base paper is coated. The composition comprises a pigment slurry and a cationic binder, and the pigment slurry contains a cationic water-soluble polymer containing 20% or more of a tertiary amine or a quaternary ammonium salt group in the pigment, and a nonionic water-soluble polymer, 0.02 to 0.5 parts by weight, and 0.1 to 1.5 parts by weight, respectively, are added to 100 parts by weight of the pigment, and the average particle size is 1.1 to 5.0 μm by wet pulverization. Moreover, 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. It is a thing.

In the coating composition for the undercoat layer applied to the present invention, when the proportion of calcium carbonate in the pigment is less than 80%, the viscosity of the coating solution remarkably increases, and further fine agglomerates are formed in the coating solution. It tends to occur. Therefore, the coating suitability deteriorates,
The strength of the coating 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,
Examples include aragonite-based light calcium carbonate.

The cationic water-soluble polymer used in the present invention comprises, as a tertiary amine or a quaternary ammonium base, 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, and if it is less than 20%, the viscosity of the coating liquid increases and the effect of improving the coating layer strength cannot be obtained. Further, if the addition amount is less than 0.02 parts by weight with respect to 100 parts of the pigment,
The slurry viscosity increases remarkably, wet pulverization is difficult, and the average particle size cannot be set to a required level. Also, 0.
If the amount exceeds 5 parts by weight, the viscosity increases remarkably, which is not preferable.

When the amount of the nonionic water-soluble polymer used in the present invention is less than 0.1 parts by weight based on 100 parts by weight of the pigment, the viscosity of the pigment slurry increases and wet pulverization is difficult, and the average particle size is kept at a required level. In addition, the pigment is detached in the drying step after coating, which causes paper dust. On the other hand, if it exceeds 1.5 parts by weight, the viscosity is remarkably increased and the efficiency of wet pulverization is lowered. 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 Is desirable. Particularly desirable is polyvinyl alcohol.

When the average particle size of the pigment slurry after wet pulverization exceeds 5.0 μm, the pigment is significantly desorbed in the drying process after coating, and the rolls in the process become soiled. 1.1
If it is less than μm, it becomes difficult to obtain the coating layer strength.

The cationic binder of the present invention includes cationized starch, cationized acrylic emulsion, cationized styrene butadiene latex, cationized ethylene-vinyl acetate copolymer, cationized styrene-acrylic copolymer, cationized vinyl acetate-. Acrylic copolymer,
Cationized butadiene-methylmethacryl copolymer, cationized vinyl acetate-butyl acrylate copolymer, cationized polyvinyl alcohol, cationized soybean protein and the like can be mentioned, but particularly preferable are cationized starch and cationized acrylic emulsion. is there. As a raw material of the cationic starch, corn starch, tapioca, horse mackerel, etc. can be used, and cationization is performed with 2-diethylaminoethyl chloride or the like into a tertiary amine type.
Alternatively, it is prepared by making a quaternary ammonium salt type by reacting 2,3 epoxypropyltrimethylammonium chloride or the like.

By using the coating composition of the present invention to coat a base paper which has been made up as a base coat layer, the adhesive strength between the base paper and the base coat layer and the strength of the base coat layer itself are increased. Furthermore, since various anionic water-soluble adhesives and the like are contained in the composition of the usual overcoat coating composition for offset printing, the top coating composition is solidified at the interface with the undercoat layer. , The adhesive strength between the topcoat layer and the undercoat layer increases. As described above, since the printed coated paper of the present invention has high pick strength, it is possible to reduce the blending amount of the adhesive of the undercoat coating composition. 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 and cold water soluble starch and casein obtained by flash-drying them. , Natural adhesives such as soybean protein, and those obtained by cationizing these adhesives. These are also a dispersant, a thickener, a water retention agent, a defoaming agent, a water resistance agent, if necessary.
Various commonly used auxiliaries such as colorants, or cationized products of these various auxiliaries can be appropriately used.

The pigment used in the present invention includes kaolin,
Calcium carbonate, clay, satin white, talc, titanium oxide, aluminum hydroxide, silica, calcined kaolin, zinc oxide, activated clay, acid clay, silicon clay, lake,
Examples include plastic pigments, but a dispersion requires a cationic dispersant, and in some cases, it is necessary to add a low molecular weight cationic activator to block the 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
Including various pulps such as used paper pulp, etc., various fillers such as light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, etc., sizing agents, fixing agents, retention agents, cationizing agents, paper strengthening agents, etc. Including various additives, acidic,
Paper is neutral and alkaline. As the base paper of the present invention, a non-size press base paper, a base paper size-pressed with 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 dowel coaters are used. Two or more layers are coated using various ordinary coating equipment such as. Each time each layer is applied, or after two or more layers are applied in succession, the coated paper is dried. The coated and dried coated papers are super calendar, gloss calendar,
Apply soft calendar processing, etc.

[0020]

EXAMPLES The effects of the present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In addition, "part" and "%" in an Example show "weight part" and "weight%", respectively.

The evaluation method of the offset printing coated paper of the present invention is shown below. 1) Average particle size: Measured with a Microtrac 7995-30SPA model manufactured by Leads & Northrop Co., Ltd. to obtain a volume-weighted average particle size. 2) Viscosity: B type viscometer, temperature of 25 ° C., 60 rp
Measured under the condition of m. 3) White paper glossiness: Measured at an angle of 75 degrees according to JIS P8142. (Unit:%) 4) Glossiness of heavy-color printing: The sample was printed by a Roland offset printing machine and left at room temperature for one day and night, and the black, magenta, cyan, and yellow four-color overprinted solid printing parts of the sample were Gloss was measured at an angle of 60 degrees.
(Unit:%) 5) Pick strength: IP using RI printing machine (Ming Seisakusho)
Printing was performed with the 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 allowable limit is rank 3. 6) Blister resistance: A commercial offset rotary printing ink was printed on both sides of the test piece by an RI printer, the test piece was wrapped in aluminum foil, and placed in 300 ° C. silicone oil for 5 seconds, and the blister was ejected. One was visually evaluated. 5
A grade of 5 is the best level. 7) Degree of detachment of pigment: A rank of 5 was obtained by evaluating the degree of stains on the roll in the drying step after coating the undercoat coating liquid on a scale of 5
Was the highest standard. The allowable limit is rank 3.

Examples 1 to 7 and Comparative Examples 1 to 6 1. Base paper formulation LBKP (water flow degree 350mlcsf) 30 parts NBKP (water flow degree 420mlcsf) 70 parts 2. Internal additive Calcium carbonate (* Indicated by ash content in base paper) * 10 parts Commercial alkyl ketene dimer internal additive sizing agent (AKD) 0.03 parts Commercial cationic polyacrylamide retention aid 0.03 parts Above 1 and 2 The pulp slurry is prepared by blending
A base paper having a basis weight (absolute dryness) of 0 g / m ² was produced. Using a gate roll coater, an undercoat coating liquid having the formulation shown in Tables 1 to 3 was applied to this base paper at a coating liquid concentration of 49% at a coating amount of 3 g / m ² per side and dried.

3. Preparation of wet pulverized pigment slurries of Examples and Comparative Examples Calcium carbonate before pulverization was A grade (specific surface area 7,000 cm ² / g) manufactured by Sankyo Seiko Co., Ltd., and the following three types were used as cationic dispersants. I was there. A) (trimethyl ethyl ammonium chloride) methacrylate monomer: acrylamide = 90:
Copolymer of composition 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:
Copolymer having composition 90. The following three nonionic water-soluble polymers were used. D) Polyvinyl alcohol (Kuraray's Poval 105) E) Polyethylene oxide (Steel Chemical PEO500)
0) F) Commercially available polyacrylamide (molecular weight: 10,000) The wet crushing mill is agitator mill L manufactured by Ashizawa Corporation.
Using ME20 type, the crushing conditions are as follows: bead packing rate 80%,
Rotation speed 960 rpm, zirconia beads (average diameter 1.0
mm) and the treatment flow rate was 3.5 l / min, and the treatment was carried out with the pigment slurry having a solid content of 65%. Example 7 is 2
Pass treatment, comparative example 5 is 3 pass treatment, comparative example 4 has a flow rate of 5
1 / min.

Formulation of Undercoat Coating Liquid Kaolin was an ultra coat manufactured by Engelhard Co., and latex was a commercially available cationized acrylic emulsion (SFC54 manufactured by Dainippon Ink and Chemicals). 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 degree of substitution of 0.04 was used. The number of binders is as follows. Cationized acrylic emulsion 15 parts Cationized starch 15 parts

A coating solution having a solid content concentration of 60% having the following composition was applied to this undercoat paper with a blade coater on one side 1
3 g / m ^{2 was} applied and dried. Topcoat coating liquid formulation Commercially available primary kaolin (Ultra White 90) 30 parts Commercially available secondary kaolin (Ultra Coat) 40 parts Commercially available wet calcium carbonate (Carbital 90) 30 parts Commercially available polyacrylic acid-based dispersant 0.1 part Commercially available phosphoric acid Esterified starch 4 parts Commercially available styrene butadiene latex (JSR0617) 12 parts Calcium stearate 0.3 parts Sodium hydroxide 0.15 parts The produced coated paper was supercalendered under the following conditions.

Super calender conditions Number of steps 10 steps Rigid roll Chilled roll, Outer diameter 400 mm Elastic roll Cotton roll, Outer diameter 420 mm Processing speed 400 m / min Linear pressure 220 Kg / cm Subsequently, upon coating the topcoat layer, the topcoat coating liquid formulation, The coating method and the super calendar conditions were the same as the above conditions. The results of Examples and Comparative Examples are summarized in Tables 1 to 3.

Comparative Example 7 A base paper produced under the same composition and production conditions as in Examples 1 to 7 was coated with a gate roll coater at a coating amount of 4 g / m ² on one side with the undercoat coating liquid described below. Dried. Compounding of Undercoat Coating Liquid Dry heavy calcium carbonate (Escaron 1500 manufactured by Sankyo Seiko Co., Ltd.) was used as a pigment, without wet pulverization.
It was prepared in the same manner as in Example 1 except that only the cationic dispersant was used as the dispersant. Calcium carbonate (Escalon 1500 manufactured by Sankyo Seiko Co., Ltd.) 100 parts Cationic dispersant A 0.6 part After applying the above-mentioned undercoating liquid, the same topcoating liquid formulation and coating method as in Examples 1 to 10 are used. The top coat layer was applied and treated under the same supercalender conditions. The quality characteristics of Comparative Example 7 are summarized in Table 3. Compared with Example 1, the degree of pigment loss is remarkable.

Comparative Example 8 Using a base paper made under the same composition and production conditions as in Examples 1 to 7, the following undercoat coating liquid was applied at a coating amount of 4 g / m ² on one side with a gate roll coater. Dried. Mixing of undercoating liquid Calcium carbonate (Escalon 1500 manufactured by Sankyo Seiko Co., Ltd.) 100 parts Commercially available sodium polyacrylate dispersant 0.6 parts Commercially available styrene butadiene latex (0617 manufactured by Nippon Synthetic Rubber) 15 parts Commercially available phosphate esterified starch ( MS4600 manufactured by Nippon Shokuhin Kogyo Co., Ltd. 15 parts The above-mentioned undercoat layer coated paper is coated with the same topcoat coating solution and coating method as in Examples 1 to 7, and then treated under the same supercalender conditions. gave. Table 3 shows quality characteristics
Summarized in. Comparative Example 8 has a lower pick strength than that of Example 1, and is a level that cannot withstand offset printing.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

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

Claims (2)

[Claims] 1. In a coated paper for offset printing, wherein two or more coating layers are provided on one side of a base paper, a coating composition of an undercoat layer closest to the base paper is composed of a pigment slurry and a cationic binder. The slurry contains a cationic water-soluble polymer containing 20% or more of a tertiary amine or a quaternary ammonium salt in the pigment and a nonionic water-soluble polymer in an amount of 0.02 to 0.5 per 100 parts by weight of the pigment. 1 part by weight, 0.1 to 1.5 parts by weight, and wet pulverization treatment to obtain an average particle size of 1.1 to 5.0 μm, and 80% by weight of the pigment is calcium carbonate. Coated paper for offset printing. 2. The offset printing coating composition according to claim 1, wherein the nonionic water-soluble polymer is one or more selected from polyethylene oxide, polyvinyl alcohol, hydroxyethyl cellulose and hydroxyethylated starch. Craft paper