JP2007031917A - Method for producing newsprint for offset printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of coating unevenness of starch by optimizing surface properties of metering rolls and surface tension of a starch coating liquid and provide a method capable of producing newsprint for offset printing excellent in printability thereby. <P>SOLUTION: The method for producing the newsprint for offset printing comprises applying a starch liquid in which the surface tension at 40°C is not higher than wetting index of metering rolls to a long continuous paper by using metering rolls in which wetting exponent defined by JIS K 6768 is ≥40 mN/m, in a gate roll coater equipped with a pair of metering rolls 3a and 3b horizontally installed side by side and rotating while being pressed onto each other and applicator rolls 2a and 2b for applying a coating pressed onto either one metering roll and passed through a space between both metering rolls to the lower part by rotation of rolls. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a method for producing a surface-printed printing paper, particularly newsprint, using a gate roll coater, and relates to a newsprint paper for offset printing excellent in printing quality, which has improved starch coating unevenness that occurs during starch coating in a gate roll coater. It is related with the manufacturing method.

In recent years, the offset printing method has become the mainstream as commercial printing, and in particular, newspaper printing has been printed by the letterpress printing method for a long time. However, offset printing rapidly progressed in the 1980s, and the number of newspaper presses in the latter half of the 1980s. After the offset printing system is reversed from the system, most newspapers are now printed by the offset printing system. Offset printing is a method in which a printing plate, usually called a PS plate, is prepared and dampening water and ink are supplied to the printing plate for printing. The printing plate is a lithographic printing plate, and the image area on the printing plate is treated so as to have an oleophilic surface, and the non-image area is treated so as to have a hydrophilic surface. When water and ink are supplied to the printing plate, ink is attached to the image area and water is attached to the non-image area, and printing is performed by transferring ink from the printing plate to paper through a blanket. Done.

In this offset printing, since ink having a relatively strong tack is used, the paper is required to have a high surface strength. In addition, when a paper having a surface with low surface strength or low water resistance is used to treat the paper surface with immersion water, so-called blanket piling may occur due to the paper dust accumulating on the blanket, and further, the paper dust. When the ink is mixed into the ink, a problem such as so-called printing surface blurring occurs on the printing surface.

As a method for dealing with the problems related to the reduction in surface strength during offset printing such as blanket piling and printing surface scuffing, an adhesive such as starch, polyvinyl alcohol or polyacrylamide resin has been used as a main component on the surface of printing paper. The surface treatment agent to be applied is applied using a roll coater such as a two-roll size press coater, a metal ring size press coater, or a gate roll coater.

In recent years, multi-color printing has become widespread in offset printing. In this multi-color offset printing, water is transferred to the paper at the specific image area every time it passes through the printing unit, so a stronger paper surface strength is required. As a result, further uniformity in the application state of the surface treatment agent has been demanded. When uneven coating occurs, the surface strength of the uncoated portion of the surface treatment agent is weak, so that paper dust is generated and troubles such as blanket piling are likely to occur. In newspaper printing, it is necessary to print a large number of copies within the limited time from the completion of the manuscript school to delivery to the newspaper dealer. It becomes a serious complaint that the distribution time to the person is delayed and is very disliked.

When PVA or PAM is used as a surface treatment agent, the surface strength is increased and the cost is increased, but also the adhesiveness of the paper surface that occurs when the paper surface is dampened with dampening water during printing (commonly called Nepari property) ) Has a tendency to increase. Compared with this, starch is advantageous in terms of cost and has a low Nepari property, but its surface strength is inferior to that of PVA or PAM.

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. However, when the peripheral speed is defined, the coating amount is adjusted only by the concentration. At this time, if the starch concentration is high, the amount of starch applied increases, which causes Nepari, and if the starch concentration is low, penetration into the paper may occur, resulting in a decrease in strength. Furthermore, the adjustment range of the coating amount is narrow only with the peripheral speed, and there is a limit to improving the surface shape of the coated 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 technique, the splash and mist of the coating liquid were suppressed, but the coating surface was not improved sufficiently.

On the other hand, Japanese Patent Laid-Open No. 8-169063 (Patent Document 3) discloses a ceramic clothing roll for an inner gate roll (metal ring roll). Although a ceramic coating of chromium oxide improves wear resistance and scratch resistance, a dynamic friction coefficient and wettability are further improved compared to chromium plating, and rolls with good wettability and no coating unevenness are disclosed. The current situation is that we are not satisfied.
Japanese Patent Laid-Open No. 11-50392 JP 2002-105893 A JP-A-8-169063

The present invention provides a method capable of solving the problem of uneven coating of starch by optimizing the surface property of the metering roll and the surface tension of the starch coating solution, and producing newsprint paper for offset printing excellent in printing suitability. This is the issue.

The inventors have studied not only the surface properties of the metering roll, but also the surface tension of the starch solution to be applied, and solved the starch coating unevenness problem by optimizing, and the wetting index below the metering roll surface By applying the starch coating solution, it was possible to produce newsprint paper for offset printing having a good starch 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 provided with an applicator roll to be applied to continuous paper, a metalling roll having a wetting index defined by JIS K 6768 of 40 mN / m or more is used. A method for producing newsprint for offset printing, in which a starch solution having an index or less is applied.

(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%.

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 and free from starch coating unevenness.

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. Then, apply with a gate roll coater.

The gate roll coater was originally developed and developed as a kind of precoater for applying pigments, etc., but in recent years, it has been newly incorporated into newspaper machines that make newspaper paper due to market demands, and paper quality has improved as an on-machine coater. It has come to be planned and is spreading rapidly.

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 40 mN / m or more is used. Those having a wetting index of less than 40 mN / m are not preferred because the starch coating solution on the surface of the metalling roll is difficult to spread and causes starch coating unevenness. 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 starch solution with the roll surface, and the application with a high-speed machine becomes possible.
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 starch coating solution hardly spreads on the surface of the metalling roll and causes uneven starch coating. 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 starch coating solution is difficult to spread on the surface of the metalling roll, which is not preferable because it causes uneven starch coating. If it exceeds 15%, the roll surface becomes brittle and is inferior in durability.

In the present invention, oxidized starch which does not cause nepari and is relatively inexpensive is used as the surface treatment agent. The starch used in the present application is prepared such that the surface tension at 40 ° C. is equal to or less than the wettability of the surface of the metering roll when it is prepared as a coating solution. When starch is cooked and diluted with diluting water, the temperature of the starch solution in the final tank is usually 40 ° C to 50 ° C. When the surface tension of the starch coating solution is equal to or lower than the wettability of the metering roll, leveling of the starch coating solution on the surface of the metalling roll is improved and coating unevenness is improved.

If the surface tension of the starch coating solution exceeds the wettability of the metalling surface, the starch coating solution 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. Examples of the starch used include oxidized starch, enzyme-modified starch, etherified starch such as hydroxyethyl etherified starch, esterified starch such as acetylated and phosphate esterified starch, and hydrophobic starch. Corn, wheat, tapioca, sago, rice, potato, etc. are used as the starch raw material, but tapioca starch has a high amylopectin ratio, so it has a high adhesiveness when wet, and there is a problem with the coatability in the coating machine. May occur. Corn starch with low tack is preferred.

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 May be added as appropriate.

Chemical pulp (NBKP, LBLP, etc.), mechanical pulp (GP, CGP, RGP, PGW, TMP, etc.), deinked waste paper pulp (DIP, etc.) alone or any as a raw material pulp for newsprint for offset printing used in the present invention Used in a mixed 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. The base paper may be made by any method such as acid paper, neutral paper, weak alkaline paper, etc., but there are newspapers for offset printing obtained by neutral paper with a large amount of filler, or vessels. The effect of the present invention is great for newsprint paper for offset printing containing a large amount of used waste paper.

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. .
Although the base paper used for the newsprint for offset printing of the present invention is not particularly limited, generally, the base paper having a basis weight in the range of about 30 to 70 g / m ² is appropriately selected according to the purpose. Select and use. The physical properties of the newspaper base paper need to be printable by an offset printing machine, and may be any material having properties such as tensile strength, tear strength, and elongation comparable to those of newsprint paper.

In addition, as a method of drying the wet application layer after starch solution application | coating, various systems, such as vapor | steam drying, gas heater drying, electric heater drying, and infrared heater drying, are employable, for example.

In the production of newsprint for offset printing of the present invention, after the formation of the coating layer of the coating composition, smoothing treatment is performed in various super calender devices. As such a calender device, a super calender is used. Commonly used calendar devices such as a soft 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 (Blanket piling)
Using the offset printing press (Mitsubishi Lithopia L-BT3-1100) for the newspaper for offset printing obtained in each Example and Comparative Example, printing four colors and printing 5000 copies, then blanket non-printing The degree of paper dust accumulation on the line was visually determined. Evaluation was the following five-step evaluation.
5: Little generation of paper dust is observed 4: Slight generation of paper dust is slightly observed 3: Although generation of paper dust is slightly observed, there is no practical problem Level 2: Clear generation of paper dust is clearly recognized 1: A lot of paper dust accumulates on the blanket

(Coating unevenness)
The newsprint paper for offset printing obtained in each Example and Comparative Example was coated with an ethanol solution of iodine and potassium iodide with a brush, colored with water vapor, and then air-dried to obtain an evaluation sample. A frequency analysis is performed on an evaluation sample of 18.06 cm square, and it is binary in a wavelength region of 0.28 cm to 3 cm in which components of a long wavelength region of 3 cm or more (derived from the floc texture) and a short wavelength region of 0.28 cm or less are cut. Then, the area ratio of the white part (the non-starch coated part) was determined.

・ 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 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 .

Preparation of Starch Liquid (A) 100 parts of oxidized starch (trade name; Oji Ace A, manufactured by Oji Corn Starch) were gelatinized at 90 ° C. and 15%, and then cooled to 60 ° C. Thereafter, 50 ppm of antifoaming agent (trade name; Bismer S, manufactured by Nisshin Chemical Laboratory) and 10 parts of a surface sizing agent (trade name: Polymaron GS25, manufactured by Arakawa Chemical Industries, Ltd.) were diluted to 5%. In addition, a starch solution (A) was produced.
Preparation of Starch Solution (B) 100 parts of oxidized starch (trade name; Oji Ace A, manufactured by Oji Corn Starch) was gelatinized at 90 ° C. and 15%, and then cooled to 60 ° C. Thereafter, 50 ppm of an antifoaming agent (trade name; Bismer S, manufactured by Nisshin Chemical Laboratory) was added to the product diluted to 5% to prepare a starch solution (B).

Preparation of starch solution (C) 100 parts of oxidized starch (trade name; Oji Ace A, manufactured by Oji Corn Starch) were gelatinized at 90 ° C. and 15%, and then cooled to 60 ° C. to prepare a starch solution (C). .

Applying the starch solution obtained above on the both sides of the base paper obtained in the above using 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 coating under the coating conditions shown in Table 1. And obtained newspaper.

Example 1
Using a gate roll coater having a ceramic solvent 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%, the surface tension at 40 ° C. is 33 mN. The starch solution (A) at a rate of 0.2 g / m ² was applied at a rate of 0.2 g / m ² per side and calendered with a soft calender at a pressure of 50 kg / cm to obtain newspaper for offset printing.

Example 2
An offset newsprint 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
An offset newsprint was obtained in the same manner as in Example 1 except that the starch solution (B) having a surface tension of 40 mN / m at 40 ° C. was used.

Comparative Example 1
An offset newsprint was obtained in the same manner as in Example 1 except that a gate roll coater having a chromium plating solvent metering roll having a surface wetness index of 30 mN / m and a maximum surface roughness of 0.99 μm was used. .

Comparative Example 2
Surface tension at 40 ° C. is 67 mN using a gate roll coater having a ceramic solvent 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%. The starch solution (C) of / m was applied so as to be 0.2 g / m ² per side and calendered with a soft calender at a pressure of 50 kg / cm to obtain offset printing newsprint.

Comparative Example 3
An offset newsprint was obtained in the same manner as in Example 1 except that a gate roll coater having a tungsten solvent 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 into a papermaking machine, particularly a paper machine for producing paper, and applies a starch coating solution to the surface of the paper. It is related with the printing paper manufactured by.

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 metal roll with a wetting index specified by JIS K 6768 of 40 mN / m or more, the surface tension at 40 ° C. is below the wetting index of the metal ring roll. A method for producing newsprint for offset printing, which comprises applying a starch solution. 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%. A newsprint for offset printing, which is manufactured by the method for manufacturing newsprint for offset printing according to claim 1.

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