JP2008196094A - Method for producing newsprint paper for offset printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of producing newsprint paper for offset printing, in which transfer printing to an applicator roll is improved and problem of color roll is solved, and which is excellent in printability by optimizing surface property of a metering roll and surface tension of a pigment coating liquid. <P>SOLUTION: The method for producing the newsprint paper for offset printing includes applying a pigment coating liquid in which the surface tension is not higher than the wet index of the metering rolls to a paper by using a metering roll in which wet index specified by JIS K 6768 is ≥50 mN/m in a gate roll coater equipped with a pair of metering rolls horizontally arranged side by side and rotating while brought into press-contact with each other and an applicator roll for applying coating pressurized to either one metering roll and passing downward by rotation of the rolls between both metering rolls to a long continuous paper. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for producing printing paper, particularly newsprint paper, on which a pigment coating liquid is applied to the surface using a gate roll coater, and improves applicator roll stains (hereinafter referred to as color winding) that occur during pigment coating in the gate roll coater. The present invention also relates to a method for producing newsprint for offset printing excellent in print quality.

In recent years, newspaper printing using cold-set offset rotary presses has been rapidly offset, colorized, and speeded up, and has better color printing suitability and printing workability for newspapers that serve as printing media. There is a need for newsprint. In addition, color images such as newspaper advertisements are required to have higher reproducibility. Although the progress of the printing plate manufacturing process and the sharpness of the original image are remarkable, the color and sharpness of the color printed under normal newsprint conditions are significantly inferior to those of ordinary coated paper for printing. , Lacking in appealing power.

Recently, in order to improve the reproducibility of the color image of this newspaper, technical development relating to high-definition printing for minimizing halftone dots (dots) representing the image has been advanced. However, when high-definition printing is performed on printing paper with poor surface properties, the minimized halftone dots are not reflected on the printing paper (missing), causing a problem in image reproducibility.

As a method for improving the image reproducibility of the printing paper, it is conceivable to improve smoothness and provide a pigment coating layer. Since there is a limit to improving smoothness with non-coated paper, it is conceivable to apply pigment, but newspaper rotary presses are mainly cold set offset type rotary presses that do not have drying equipment, so the amount of coating can be reduced. The increased number not only affects the set-off after printing, but also the amount of coating is limited due to the recent reduction in weight of newspapers.

Coating methods that can reduce the coating amount include two-roll size press coaters, roll coaters such as metal ring size press coaters and gate roll coaters, rod blades, and shim sizers. In many cases, a gate roll coater is introduced for coating an additive sizing agent.

Troubles at the time of coating with the gate roll include problems such as color winding due to transfer failure from the gumming up and the metering roll to the applicator roll, in addition to coating unevenness due to the coating liquid peeling pattern on the roll.

Various proposals have been made to improve the above-described problems. For example, in JP-A-11-50392 (Patent Document 1), a coating liquid in which a pigment and starch are blended at a specific ratio is specified. When applying with an applicator roll having a diameter, the peripheral speed ratio of the inner gate roll (metering roll) and the outer gate roll (fountain roll) to the applicator roll is set to 50 to 80%, so that the surface shape of the application surface is changed. Methods that can be improved have been proposed. With only the peripheral speed, the adjustment range of the coating amount is narrow, and there is a limit to improving the surface shape of the coating surface.

In JP-A-2002-105893 (Patent Document 2), the coating speed is 1400 m / min or more, and the peripheral speed of the fountain roll is 45% or less and 20% or more of the coating speed. The peripheral speed is 85% or less of the coating speed, 60% or more, and the hardness of the fountain roll is 70 to 90 degrees, and the roll diameter of the fountain roll and the metering roll is 500 mm or more. We are proposing a technology to suppress the generation of mist. By using this technology, the splash and mist of the coating liquid were suppressed, but the color winding was not improved sufficiently.

On the other hand, Japanese Patent Laid-Open No. 8-169063 (Patent Document 3) discloses a ceramic coating roll for an inner gate roll (metalling roll). A ceramic coating with chromium oxide improves wear resistance and scratch resistance, further improves the dynamic friction coefficient and wettability compared to chromium plating, and a roll with no coating unevenness has been disclosed. The winding improvement was not enough.
Japanese Patent Laid-Open No. 11-50392 JP 2002-105893 A JP-A-8-169063

By optimizing the surface property of the metering roll and the surface tension of the pigment coating liquid, the present invention improves the transferability to the applicator roll, solves the problem of color winding, and provides excellent offset printing. It is an object of the present invention to provide a method capable of producing paper.

The present inventors examined not only the surface properties of the metering roll, but also the surface tension of the pigment coating solution, and by optimizing it, the transferability to the applicator roll was solved, and color winding did not occur. It was possible to produce newsprint for offset printing that had a smooth coating surface and excellent printability.
The present invention includes the following inventions.

(1) A pair of metering rolls arranged side by side and rotating while being pressed against each other, and a long paint which is pressed against one of the metalling rolls and passes downward between the two metalling rolls by the rotation of the rolls. In a gate roll coater equipped with an applicator roll that is applied to continuous paper, a wetting index as defined in JIS K 6768 is 50 mN / m or more, and the surface tension is below the wetting index of the metering roll. A method for producing newsprint for offset printing by applying a pigment coating solution.

(2) The method for producing newsprint for offset printing according to (1), wherein the maximum surface roughness of the metering roll measured by a JIS B 0651 stylus type surface roughness measuring machine is 3.0 μm or more.

(3) The method for producing newsprint for offset printing according to (1) or (2), wherein the porosity of the roll surface layer portion measured according to JIS R 2205 of the metalling roll is 8 to 15%.

(4) Newsprint paper for offset printing manufactured by the method for manufacturing newsprint for offset printing described in (1) to (3) above.

According to the present invention, it is possible to obtain a newsprint for offset printing excellent in surface strength without uneven application of a pigment coating liquid.

Generally, the surface treatment agent coating apparatus includes, for example, a two roll size press, a blade metalling size press, a rod metalling size press, a gate roll coater, a blade coater, a bar coater, a rod blade coater, an air knife coater, Curtain coaters, spray coaters, etc. are used as appropriate, but in the case of newspaper base paper, high-speed coating exceeding 1000 m / min is possible, and the paper surface coating agent must be efficiently coated on the paper surface. It is preferable to apply with a gate roll coater.

FIG. 1 is a conceptual cross-sectional explanatory view of a gate roll coater used in the present invention. As shown in FIG. 1, in the gate roll coater, applicator rolls 2a and 2b are arranged on both sides of the base paper 1, and metering rolls 3a and 3b and fountain rolls 4a and 4b are arranged on the outer sides thereof. This is a device that simultaneously applies to both the front and back sides of paper. The coating agent is supplied between a metering roll and a fountain roll from a coating agent supply pipe (not shown) to form coating agent pounds 5a and 5b. The coating agent supplied between the fountain roll and the metalling roll forms a thin film on the surface of the metalling roll, and is transferred to paper through the applicator roll. The metering roll 2 is installed between the applicator roll 1 and the fountain roll 3 and is generally coated with chrome plating from the beginning in order to prevent rust and wear resistance of the steel roll. It was. In recent years, rolls having various surface materials have been developed with the advance of technology, and tungsten spraying and ceramic spraying are examples. Depending on the coater, even if the chrome plating is the same, the plating surface may be flat (plane) or roughened to have fine irregularities.

In the present invention, a metalling roll having a wetting index (specified in JIS K6768) of 50 mN / m or more is used. When the wetting index is less than 50 mN / m, the pigment coating liquid on the surface of the metering roll is difficult to spread, and this is not preferable because it causes poor transferability to the applicator roll. The upper limit of the measured value of the wetting index according to JIS K 6768 is 73 mN / m, but there is no particular upper limit to the wettability of the metalling roll surface. The higher the wettability of the roll surface, the faster the familiarity of the pigment coating liquid on the roll surface, and the higher speed machine can be applied.
Moreover, it is preferable that the maximum surface roughness (measured with a JIS B0651 stylus type surface roughness measuring machine) of the metering roll is 3.0 μm or more. When the maximum surface roughness is less than 3.0 μm, it is not preferable because the coating liquid hardly spreads on the surface of the metalling roll and causes transferability to the applicator roll. If it exceeds 20 μm, roll patterns and splash are likely to occur, which is not preferable.

  Furthermore, the porosity (specified in JIS R2205) of the surface of the metalling roll used in the present invention is preferably 8 to 15%, more preferably 12 to 13%, and the porosity is less uneven. preferable. When the porosity is less than 8%, the pigment coating solution is difficult to spread on the surface of the metalling roll, which is not preferable because it causes poor transfer to the applicator roll. If it exceeds 15%, the roll surface becomes brittle and is inferior in durability.

If the surface tension of the pigment coating liquid exceeds the wettability of the metalling surface, the pigment coating liquid is difficult to level on the roll surface, and the split pattern is difficult to disappear. However, if it is less than 25 mN / m, it may cause splashing of the coating liquid and mist on the exit side of the nip between the metering roll and the fountain roll, resulting in a decrease in the yield of the coating agent and coating around the coater. There is a risk that the operability will be reduced, such as the occurrence of dirt due to the agent.

The pigment coating solution of the present invention is not particularly limited as long as the surface tension is not more than the wetting index of the metering roll. The pigment in the pigment coating solution is not particularly limited, and it is optimal to use calcium carbonate and kaolin as main pigments. Among calcium carbonates, there are acicular, columnar, spherical, spindle-shaped, etc. Among them, a cubic one is preferable because it has an effect on set-off. Cubic light coal tends to have a sparse structure in the coating layer, has a high ability to absorb the vehicle component in the ink, and thus has a high set-off suppressing effect, and is structurally susceptible to a friction coefficient. The smaller the particle diameter of calcium carbonate, the smaller the pore diameter of the coating layer and the larger the specific surface area, which is advantageous for set-off and opacity. Calcium carbonate is highly effective in improving opacity, but tends to increase the coefficient of dynamic friction. In the case of newspapers driven at high speed, if the coefficient of friction is low, web tension is less likely to be applied, and wrinkles and paper flow may occur. Adjustment is necessary. Kaolin is used in combination so that the dynamic friction coefficient is in the range of 0.5 to 0.65 from the viewpoint of printing workability and printing suitability, and considering the balance with the effect of improving opacity.

Although it does not specifically limit as a binder of a coating liquid, Latexes, such as synthetic latexes, such as a styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, and a methylmethacrylate-butadiene copolymer, or oxidized starch Enzymatically modified starch, etherified starch such as hydroxyethyl etherified starch, esterified starch such as acetylated or phosphate esterified starch, starch such as hydrophobic starch, and the like can be used.

There is no particular limitation on the adjustment of the surface tension of the pigment coating liquid, but there are adjustment methods based on the addition amount and blending amount of the adhesive, and adjustment methods using a water retention agent. This is preferable because the influence of
As water retention agents, alkali thickening types such as polycarboxylic acids and acrylic copolymers, methacrylic acid-acrylic acid ester copolymers, acrylic polymers, and hydrophilic base polymers such as polyethylene oxide are used at both ends. Naturally derived types such as an association type in which an oil group is arranged, carboxymethylcellulose, sodium alginate and the like can be mentioned, but are not limited to these water retention agents.

In the present invention, as a subcomponent of the coating liquid, synthetic water-soluble polymers such as polyvinyl alcohol and polyacrylamide, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl methacrylate-butadiene copolymer Synthetic latexes such as defoamers, slime control agents, dyes, water resistance agents, surface sizing agents, water-soluble celluloses such as carboxymethylcellulose, methylcellulose, and hydroxyalkylcellulose, natural water-soluble substances such as alginic acid, guar gum, xanthan gum, and pullulan A functional polymer derivative or the like may be appropriately blended within a range that does not affect the surface tension of the pigment coating solution.

Although it does not necessarily limit as raw material pulp of the newsprint for offset printing used by this invention, Chemical pulp (NBKP, LBLP, etc.), Mechanical pulp (GP, CGP, RGP, PGW, TMP, etc.), Deinked waste paper Pulp (DIP or the like) is used alone or mixed at an arbitrary ratio. Further, a paper filler such as white carbon, clay, amorphous silica, talc, titanium oxide, calcium carbonate is added during papermaking. Also, if necessary, publicly known papermaking chemicals such as internal sizing agents, fixing agents, paper strength enhancers, retention agents, water resistance agents, UV absorbers, etc. are added as appropriate, using known publicly available paper machines. Paper is made. As a papermaking method of the base paper, any method such as acid papermaking, neutral papermaking, and weak alkali papermaking may be used.

There are no particular limitations on the papermaking conditions of the base paper. As the paper machine, for example, a commercial paper machine such as a long paper machine, a gap former paper machine, a circular paper machine, or a short paper machine can be selected and used as appropriate according to the purpose. .
The base paper used for the offset printing paper of the present invention is not particularly limited, but in general, a base paper having a basis weight in the range of about 30 to 70 g / m ² is appropriately selected according to the purpose. Used. The physical properties of the base paper need to be printable by an offset printing machine, as long as it has physical properties such as tensile strength (1.5 kN / m or higher) and tear strength (390 mN or higher), which is usually about that of newsprint. good.

In addition, as a drying method after pigment coating, various systems, such as vapor drying, gas heater drying, electric heater drying, infrared heater drying, etc., are employable, for example.

In the production of the offset printing paper of the present invention, after the formation of the coating layer of the coating composition, smoothing treatment is performed in various super calender devices. Such calender devices include super calenders, software Commonly used calendar devices such as a calendar, a gloss calendar, a compact calendar, a mat calendar, and a mat super calendar can be used as appropriate. As the calender finishing conditions, the temperature of the rigid roll, the calender pressure, the number of two cups, the roll speed, the paper moisture before the calender, and the like are appropriately selected according to the required quality. Furthermore, the calendar device includes an off type that is different from the coater and an on type that is integrated with the coater, but can be used in either case. The material of the calendar apparatus to be used is a roll which is mirror-finished with a metal or a hard chrome plating on the surface of a rigid roll. As the elastic roll, a roll obtained by molding a resin roll such as urethane resin, cotton, nylon, asbestos, aramid fiber or the like is used as appropriate. It should be noted that it is of course possible to use a suitable combination of a water coating device, an electrostatic humidifier, a steam humidifier, and the like for conditioning and humidifying the coated paper after finishing with a calendar.

  The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example represent a weight part and weight%, respectively.

Evaluation method (color winding evaluation)
The pigment coating liquid obtained in each Example and Comparative Example was applied with the gate roll coater shown in FIG. 1, and the applicator roll was visually checked for dirt.
○: No applicator roll contamination ×: Applicator roll contamination

(Coating liquid surface tension)
The surface tension of the coating solution was measured using a Dunui surface tension meter.

・ Preparation of base paper 10 parts of softwood kraft pulp, 25 parts of thermomechanical pulp, 5 parts of groundwood pulp and 60 parts of deinked waste paper pulp were mixed and disaggregated. S. 100 parts of pulp slurry made of pulp prepared in F (Canadian Standard Freeness), 2 parts of white carbon as a filler, 2% of aluminum sulfate, rosin sizing agent (trade name; SPG, Arakawa) A stock was prepared by adding 0.4% of Chemical Industries). The obtained paper stock was made with a twin wire type paper machine to prepare a base paper having a rice basis weight of 42 g / m ² .

-Adjustment of coating solution Light calcium carbonate (Brilliant S15, manufactured by Shiraishi Kogyo Co., Ltd.) 70 parts Kaolin (trade name: Milagros J, manufactured by Seal Co., Ltd.) 30 parts Dispersant (trade name: Aron T-40, Toa Gosei Co., Ltd.) 0.05 parts added and dispersed in 60% dispersion slurry 8.5 parts of styrene-butadiene latex (trade name: T-2635R, JSR Co., Ltd.), heat-dissolved oxidized corn starch (Product name: Oji Ace A, manufactured by Oji Cornstarch Co., Ltd.) 43 parts, Lubricant (Product name: SN8004SP, manufactured by San Nopco Co., Ltd.) 0.23 parts, Water resistant agent (Product name: Sumires SPI-102A, Sumitomo Chemical Co., Ltd.) Company made) 0.15 part, fluorescent dye (trade name: Kaya Hall BHT, Nippon Kayaku Co., Ltd.) 0.5 part, water retention agent (trade name: Somalex 2) A pigment coating liquid having a solid content concentration of 25% and comprising 0.2 parts (70K, manufactured by Somar Co., Ltd.) was prepared.

Coating On the both sides of the base paper obtained above, the above-obtained pigment coating solution is a gate roll coater composed of a metering roll having a diameter of 810 mm, a fountain roll having a diameter of 860 mm, and an applicator roll having a diameter of 1070 mm. The peripheral speed is 100% for the 2b applicator roll, 3a metallizing roll 85%, 3b metallizing roll 75%, 4a fountain roll 55%, 4b fountain roll 40%, and the coating conditions shown in Table 1 Coating was performed to obtain newsprint for offset printing.

Example 1
The surface tension is 46 mN / m using a gate roll coater having a ceramic sprayed metalling roll having a surface wetness index of 65 mN / m, a maximum surface roughness of 2.6 μm, and a porosity of the surface of 8 to 15%. The coating solution was applied at 1.4 g / m ² per side and calendered with a soft calender at a pressure of 50 kg / cm to obtain offset printing newsprint.

Example 2
Newspaper for offset printing was obtained in the same manner as in Example 1 except that a metalling roll having a maximum surface roughness of 4.6 μm was used.

Example 3
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that the amount of water retention agent in the pigment coating solution was changed to 0.5 part.

Comparative Example 1
Newspaper for offset printing was obtained in the same manner as in Example 1 except that a gate roll coater having a chrome plating sprayed metalling roll having a surface wetness index of 30 mN / m and a maximum surface roughness of 0.99 μm was used. It was.

Comparative Example 2
Using a gate roll coater having a ceramic sprayed metalling roll having a surface wetness index of 65 mN / m, a maximum surface roughness of 2.6 μm and a surface porosity of 8 to 15%, An offset stamp paper was obtained in the same manner as in Example 1 except that 5.0 parts and 1.0 part of the water retention agent were used.

Comparative Example 3
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that a gate roll coater having a tungsten sprayed metalling roll having a surface wetness index of 35 mN / m and a maximum surface roughness of 2.7 μm was used.

The present invention is a kind of roll coater that is incorporated in a papermaking machine, in particular, a paper machine for producing paper, and applies a pigment coating liquid to the surface of the paper. The surface property of the gate roll coater suitable mainly for the production of printing paper and The present invention relates to a printing paper manufactured thereby.

It is sectional drawing which shows schematically the structure of the gate roll coater used for this invention.

Explanation of symbols

1 Base paper 2a, 2b Applicator roll 3a, 3b Metering roll 4a, 4b Fountain roll 5a, 5b Coating agent pound

Claims (4)

A pair of metering rolls arranged side by side and rotating while being pressed against each other, and a long continuous sheet of paint that is pressed against one of the metalling rolls and passes downward between the two metalling rolls by the rotation of the rolls In a gate roll coater provided with an applicator roll to be applied to a pigment, a wetting index as defined in JIS K 6768 is 50 mN / m or more, and a pigment whose surface tension is less than or equal to the wetting index of the metering roll A method for producing newsprint for offset printing, which comprises applying a coating liquid containing the offset liquid. The method for producing newsprint for offset printing according to claim 1, wherein the maximum surface roughness of the metering roll measured by a JIS B 0651 stylus type surface roughness measuring machine is 3.0 µm or more. . The method for producing newsprint for offset printing according to claim 1 or 2, wherein the porosity of the roll surface layer portion measured according to JIS R 2205 of the metalling roll is 8 to 15%. Newsprint paper for offset printing, which is manufactured by the method for manufacturing offset printing paper according to claim 1.

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