JP2007162178A - Offset printing newsprint paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide offset printing newsprint paper having high opacity, excellent ink setting properties and printability with slight piling during printing in the newsprint paper having a high waste paper pulp blending ratio, produced with a high-speed paper machine and used for high-speed cold offset rotary printing and to further provide the offset printing newsprint paper suitable for printing with an environmentally friendly type ink (eco-ink). <P>SOLUTION: The offset printing newsprint paper is obtained by forming pigment coating layers on both surfaces of base paper having ≥60 mass% waste pulp blending ratio and 5-15 mass% ash content. The pigment coating layers have 0.5-3 g/m<SP>2</SP>total coating weight of both the surfaces converted into the dry solid content and 37-45 g/m<SP>2</SP>metric basis weight (weight per m<SP>2</SP>). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to newspaper printing paper whose main object is so-called daily paper that is made in large quantities every day and printed in large quantities, and in particular, printed on a so-called cold set type printing machine that does not dry with a heating dryer after printing. The present invention relates to newsprint for rotary offset printing.

  In the past, mechanical pulp was mainly used as a raw material for newsprint, but deinked waste paper pulp (DIP) has become the main raw material for newsprint due to a shortage of raw materials and environmental reasons. The problem with high-rate blending of DIP is that it is difficult to achieve opacity compared to mechanical pulp, and it is difficult to achieve both improved opacity and high-blend blending of DIP. In particular, clay, talc, and calcium carbonate contained in DIP have a relatively poor effect on opacity, so paper with a high DIP content often contains 5% or more of ash to maintain sufficient opacity. In addition, printing troubles caused by paper dust, as well as ash spilled off at places where paper was cut, such as pasters, slitters, and cutters, caused dust to fly and increased various troubles including deterioration of the working environment.

  About pH at the time of newsprint paper making, in order to improve the fixing of the sizing agent as much as possible, it was adjusted with aluminum sulfate or the like, and a condition of pH less than 5 was generally adopted. However, in recent years, there is also a benefit of improving the performance of the sizing agent and the yield improving agent, and it has become possible to maintain the sizing property even at a relatively high pH of 5 or more, including neutral to alkaline ones.

Newspapers have also been reduced in weight. Around 1980, lighter weight was spread from the previous 49g / m ² , and 46g / m ² was the mainstream until around 1990. After that, 43g / m ² became mainstream, and in 2001, 40g / m ² of ultra-lightweight paper was introduced as an XL grade. Along with this, there is an increasing demand for paper that can maintain high opacity after printing. In order to increase the opacity of paper, inorganic fine particles such as white carbon, calcium carbonate, titanium oxide or talc are used as a filler during papermaking. As came to be used a lot. As the ash content that was once less than 5% was also added, these inorganic fine particles are one of the main components of paper powder that easily leaches out of the paper layer by dampening water during offset printing and is piled on the blanket. Become one.

  As a newspaper printing method, cold offset printing has become the mainstream in recent years. 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 plate, and the image area on the printing plate is treated to have an oleophilic surface, and the non-image area is treated to have a hydrophilic surface. When dampening 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 the ink is transferred from the printing plate to the paper through the blanket for printing. To do.

  With the recent increase in environmental awareness, “environmentally friendly inks” (so-called eco-inks) such as soybean oil ink that does not use aromatic solvents have been used for printing. These are inks with relatively strong tack, and the paper is required to have high surface strength. Further, since dampening water adheres to the paper surface, paper dust may accumulate on the blanket when paper having a high paper ash content, low surface strength, or low water resistance is used.

In recent years, colorization and speeding-up have been rapidly progressing, and there is a demand for newsprint having better color printing suitability and printing workability for newsprint used as a printing medium. In addition, color images such as newspaper advertisements are required to have higher reproducibility. In addition, the coated paper made by coating the base paper with a paint consisting of pigment and binder at a dry weight of about 8 g / m ² or more and drying is suitable for high-quality printing. Printing presses with a heat setting device and oxidative polymerization drying ink are used, and the ink drying system is different from cold offset printing presses and newspaper printing using penetrating drying ink. Printing paper on a newspaper press may cause troubles related to print quality and workability, such as poor set-off due to poor ink absorbency, and conversely dirt on the guide roller caused by too high ink absorbency. .

  As a means to improve ink deposition and opacity after printing without applying a high amount of paint to the level of coated paper, and without adding inorganic fine particles at the time of papermaking, various pigments are applied to the newspaper paper surface after papermaking. A method of applying a relatively small amount has been proposed. Satin white, hydrated silicic acid, and hollow organic pigments can be applied to improve whiteness, opacity, and opacity after printing with a small amount of coating, but the bonding strength with the adhesive is weak and size characteristics Deterioration of blanket piling due to lack of. For example, a method of applying a hollow organic pigment (Patent Document 1) and an opacity improving method by applying a silica pigment on a surface (Patent Document 2) are caused by insufficient adhesion due to high oil absorption of the pigment, Printing workability such as powder falling is inferior.

Light calcium carbonate coating has also been studied in the past, and its effect on opacity and opacity after printing is inferior to that of satin white, hydrated silicic acid, and hollow organic pigments, but the surface strength is relatively low. Are better. For example, the opacity improving method (Patent Document 3) by providing a coating layer containing a pigment containing an acicular pigment and having an average oil absorption of 65 cc / 100 g or more is similar to the above in that a powder oil absorption is high. In order to make up for the disadvantages, mechanical pulp was the main component, and a coating amount of about 10 g / m ² had to be applied, and it was not able to withstand the current high-speed printing. In addition, Patent Documents 4 to 9 are known as documents relating to newspaper-printed paper coated with pigments.
JP 2000-34694 A Japanese Patent Laid-Open No. 11-189995 Japanese Patent No. 2504819 Japanese Patent Laid-Open No. 4-47998 Japanese Patent Laid-Open No. 11-50393 JP 2000-136497 A JP 2001-164494 A JP 2001-226896 A JP2003-286686A

  The problem to be solved by the present invention is that the ratio of waste paper pulp is high, and the newspaper paper for high-speed cold offset rotary printing manufactured by a high-speed paper machine has high opacity during printing and excellent ink setting properties. Another object of the present invention is to provide newsprint paper that is excellent in printability with little piling. It is another object of the present invention to provide newsprint suitable for printing with environmentally friendly ink.

In order to solve the above problems, the present invention employs the following configurations (1) to (8).
(1) A pigment coating layer containing calcium carbonate is formed on both sides of a base paper having a waste paper pulp content of 60% by mass or more and an ash content of 5 to 15% by mass, and the pigment coating layer has a dry solid content. Convert the a 0.5 to 3 g / m ² in total coating amount of two-sided, offset printing newsprint basis weight is 37~45g / m ² in.
(2) The newspaper for offset printing according to (1) above, wherein the pigment coating layer has a binder content of 40 to 130 parts by mass with respect to 100 parts by mass of the pigment.
(3) Newsprint paper for offset printing according to (1) or (2) above, wherein calcium carbonate is 50% by mass or more in all pigments in the pigment coating layer.
(4) Newsprint paper for offset printing according to any one of (1) to (3) above, wherein the contact angle of water on the surface is 45 to 110 degrees.
(5) The newspaper for offset printing according to any one of (1) to (4) above, wherein the product has a tightness of 0.6 to 0.7 g / cm ³ and a smoothness of 20 to 60 seconds.
(6) The offset according to any one of (1) to (5) above, wherein the calcium carbonate used for the pigment coating layer is wet-synthesized and then blended into the paint without passing through a drying step. Newsprint paper for printing.
(7) The newsprint for offset printing according to any one of (1) to (6) above, which is for environmentally friendly ink printing.
(8) A method for producing the newsprint according to any one of (1) to (7) above, wherein the base paper is made with a gap-type former, and the pigment coating layer is formed on an on-machine gate roll system. A method for producing newsprint for offset printing, characterized in that coating is performed with a coating facility and surface treatment is performed with an on-machine calendar of a soft nip.

  The newsprint for offset printing according to the present invention has excellent opacity after printing at the time of cold set type rotary offset printing, excellent ink setting properties, excellent ink setting, and good printing work with less troubles such as piling. There is an advantage of having a good color printing quality. Further, even when an environmentally friendly ink is used, there is an advantage that each of the above characteristics is excellent.

The present inventors have intensively studied means for improving the post-printing opacity with a waste paper pulp content of 60% or more, an ash content of 5% or more and less than 15%, and a rice basis weight of 37 g / m ² or more and 45 g / m ² or less. As a result, a pigment coating layer containing calcium carbonate is provided on the newspaper paper surface with a gate roll, etc., and by controlling the coating amount, the set-off is excellent, and there is no occurrence of piling, powder falling, etc., good printing The inventors found that very good opacity after printing was obtained while maintaining workability, and completed the present invention.

<Base paper>
The base paper for newsprint for offset printing used in the present invention is based on the premise that 60% or more of deinked waste paper pulp (DIP) is blended. The ratio is expected to increase in the future. In the old newsprint mainly composed of mechanical pulp, the opacity after printing becomes relatively good, so that the effect of the present invention cannot be sufficiently exhibited. In addition, chemical pulp (NBKP, LBKP, etc.), mechanical pulp (GP, CGP, RGP, PGW, TMP, etc.), etc. are used alone or mixed at an arbitrary ratio as raw material pulp. Further, a paper filler such as white carbon, clay, amorphous silica, talc, titanium oxide, calcium carbonate is added during papermaking.

These inorganic fine particles, together with the inorganic fine particles contained in the pigment coating layer, are based on the premise that the ash content in the entire newspaper is 5% or more and less than 15%. This is an area necessary to prevent piling and dust falling while maintaining appropriate post-printing opacity for eco-inks based on soybean oil and other materials widely used in current cold offset rotary presses. Yes, when the ash content is lower than this, the opacity is insufficient even when the pigment is applied, and when the ash content is high, piling and powder fall off occur. Further, if necessary, publicly known papermaking chemicals such as an internal sizing agent, a fixing agent, a paper strength enhancer, a yield improver, a water resistance agent, and an ultraviolet absorber are appropriately added to make paper. It is assumed that the paper weight including the pigment coating layer is 37g / m ² or more and 45g / m ² or less. This is also related to the ratio of waste paper content and ash content, but in each of the above ranges, the pigment coating method causes a decrease in strength in varieties with a weight of less than 37 g / m ² , so it is compatible with current high-speed offset printing. In addition, when the amount exceeds 45 g / m ² , there is sufficient post-printing opacity, so that the effect of the present invention cannot be sufficiently exhibited.

<Coating pigment>
In the present invention, in the newspaper for offset printing, it is the basis of the present invention to provide a pigment coating layer containing calcium carbonate on the surface, but the calcium carbonate has a needle shape, a spindle shape, a cubic shape, etc. Various calcium carbonates can be used. Any calcium carbonate can be used, including heavy calcium carbonate, including causticized light calcium carbonate produced in the papermaking process. However, the particle size is a problem from the viewpoint of coating on the paper surface, and the average particle size is preferably 5 μm or less, and preferably 2 μm or less. Various pulverizers can be used to adjust to this particle size. The average particle diameter referred to here is a median diameter obtained by measuring the particle size distribution with a laser diffraction particle size distribution analyzer (type: SALD-2000, manufactured by Shimadzu Corporation).

  Light calcium carbonate is particularly preferably used, and the effect is particularly great when 50% or more of the pigment is light calcium carbonate. In addition to pigments other than light calcium carbonate, pigments such as kaolin clay, talc, aluminum hydroxide, titanium dioxide, and satin white can be blended. As the characteristics of these pigments, the oil absorption and the frictional characteristics resulting from the surface shape are considered to affect the effect of the present invention, and calcium carbonate is considered to be in an appropriate range. If a pigment such as hydrated silicic acid such as hydrated silicic acid exceeding 100 ml / 100 g (JIS K-5101) is used, the binder will be insufficient and powder will fall off, and the object of the present invention will not be achieved. Also, kaolin, which has low frictional properties, will cause piling. In addition, a combination of only those having a low oil absorption such as titanium dioxide leads to defective ink setting.

Thus, calcium carbonate is a well-balanced inorganic fine particle in order to achieve this purpose, but among the particularly preferred light calcium carbonates, piling tends to deteriorate after a drying process once after wet synthesis. More preferably, it is blended into the coating material without passing through the drying step in the slurry state.
Further, commercially available dry powdered light calcium carbonate has been devised to contain a dispersing agent so that it can be easily dispersed in water. On the other hand, when trying to absorb ink such as soybean oil ink with a small amount of coating layer as in the present invention, it is also effective means to slightly agglomerate the pigment to increase oil absorption. In such a case, it is preferable to produce a paint by using the synthesized light calcium carbonate without passing through a drying step.

<Coating amount>
Pigment layer containing the calcium carbonate is provided in 0.5 g / m ² or more 3 g / m ² or less in the range in both sides. If it is less than 0.5 g / m ² , the effect of the present invention is not sufficient, and the opacity after printing becomes the same level as that of non-coated paper. In addition, since the ink is not sufficiently absorbed, the ink setting in the high-speed printing machine is deteriorated, and a set-off occurs in which the ink on the paper once printed is transferred to another paper. On the other hand, if the coating amount exceeds 3 g / m ² , the opacity after printing will be good, but the guide roller will be smeared if the ink is excessively absorbed by the vehicle. Further, it is considered that the stiffness tends to decrease with the decrease in the amount of the base paper. The object of the present invention can be achieved in this coating amount range, but for the same reason as above, preferably 0.6 g / m ² or more and 2.8 g / m ² or less, more preferably 1.0 g / m ² or more and 2.5 g / m ^2. The range is ² or less.

<Composition of paint>
The pigment of the pigment coating layer preferably adjusts the ratio of the pigment to the adhesive to 0.8 to 2.5 from the viewpoint of enhancing the opacity effect after printing and maintaining the piling and dusting characteristics. When the amount of the pigment is less than this ratio, the opacity effect after printing cannot be obtained sufficiently, and when the amount of the pigment is larger than this ratio, piling and powder fall off easily occur.
Moreover, as an adhesive, an adhesive generally used in papermaking, such as starch, natural rubber latex, synthetic resin latex, and PVA can be used. As a main component of the adhesive, starch is preferably used from the viewpoint of cost. As the kind of starch, generally used raw starch, oxidized starch, etherified starch such as hydroxyethyl etherified starch, esterified starch such as phosphate esterified starch, or enzyme-modified starch can be used. Components other than starch include water-soluble celluloses such as carboxymethylcellulose, methylcellulose, and hydroxyalkylcellulose, natural water-soluble polymer derivatives such as alginic acid, guar gum, xanthan gum, and pullulan, and synthetic water-soluble high polymers such as polyvinyl alcohol and polyacrylamide. Molecules can be used as an adhesive. As the latex, any synthetic latex such as styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, and methyl methacrylate-butadiene copolymer can be suitably used. In addition, antifoaming agents, slime control agents, dyes and the like may be appropriately blended. When synthetic resin latex is used in combination with starch, there is a balance with the surface contact angle described later, but due to surface strength, soybean oil ink absorbability, etc., about 10-60 parts by weight of latex is 100 parts by weight of starch. preferable.

<Paper making equipment>
Gap-type formers are desirable for papermaking conditions. The reason is that it is advantageous in post-printing opacity, which is the center of the present invention, as well as high operational efficiency that can be produced at a high speed exceeding 1500 m / min. In the gap former, since the raw material slurry injected from the slice is sandwiched between the wires from both sides at the same time, there is little difference between the front and back, and the paper layer structure of the front and back is taken when the cross section of the paper layer is observed. As a result, the penetration of ink is suppressed evenly with respect to newspaper printing printed from both sides, and it is possible to appropriately set the amount that cannot be absorbed by the pigment coating layer on the surface. Therefore, it is desirable that the pigment coating, which is the main component of the present invention, be performed by a gap former type paper machine. Other paper machines include, for example, commercial-scale paper machines such as long net paper machines, circular net paper machines, and short net paper machines. Is not enough. In addition, the on-top paper machine with a wire added to the long paper machine also has a difference in front and back, which may result in a decrease in opacity after printing, powder falling from the surface with a large amount of filler, and piling.

  A gate roll coater is desirable as a coating apparatus for applying the pigment coating layer to newsprint base paper. The reason is that it is a suitable facility for obtaining the coating amount region of the present invention, and that it can be easily produced at high speed on-machine, but most importantly, compared with other coating devices. This is advantageous for opacity after printing. A roll coater such as a gate roll coater forms a coating film on the roll and then transfers it to the base paper, so that the coating liquid does not penetrate into the paper layer and stays on the surface to form a barrier layer for printing. can do. Since this layer suppresses ink penetration into the base paper during newspaper printing, good post-print opacity can be obtained. Therefore, it is desirable that the main pigment coating of the present invention is applied by an on-machine gate roll coater. Other coating machines include two-roll size press, blade metering size press, rod metering size press, off-machine gate roll, trailing, flexible, roll application, fountain application, short dwell and other bevel types and vent types. There are devices such as a rod coater, a bar coater, an air knife coater, a curtain coater, a spray coater, and a gravure coater, but the effect of the present invention is not sufficient due to the penetration of the coating layer. In addition, as a method of drying the wet coating layer after apply | coating a surface treating agent composition, various systems, such as vapor | steam drying, gas heater drying, electric heater drying, infrared heater drying, are employable, for example.

  In the production of newsprint for offset printing according to the present invention, after the formation of the coating layer of the surface treating agent composition, smoothing treatment is performed with various calendering devices, and an on-machine calender with a soft nip is desirable. The reason for this is that, with the calendar strength normally performed with a soft calendar such as on-machine, one stack, etc., sufficient smoothness is obtained as newsprint, and it is suitable for high-speed production applied in the present invention. It is most important that this is also a preferable facility for the opacity after printing as described above. Since the paper is obtained by molding a non-uniform pulp slurry into a sheet shape, the thickness is not completely uniform. In the soft nip calender, since a relatively uniform pressure is applied even when the paper surface is uneven when pressure is applied to the paper, the tension is almost constant over the entire surface. This is because, compared with the case where the thickness is constant, the ink penetration and light scattering properties are uniform, which is preferable for opacity after printing. Therefore, the main pigment coating of the present invention is desirably performed by an on-machine soft nip calender. Examples of other calendars include commonly used calendars such as a super calendar, a gloss calendar, a compact calendar, a mat super calendar, and a mat calendar, but the effects of the present invention are not sufficient. As the soft nip calender described above, MOL from Kiesta, Optinip from Valmet, etc. can be used. As a method of applying a soft nip calender, either a method of passing one calender of 1 nip (1 nip × 1 stack) or a method of passing two calenders of 1 nip (1 nip × 2 stacks) may be used. In this case, it is usually preferable to reverse the surfaces in contact with the metal roll between the first and second units. The linear pressure of the calendar is 5 to 200 kg / cm, preferably 50 to 150 kg / cm.

<Physical properties of paper>
The newsprint paper, which is the object of the present invention and has high opacity at the time of printing, excellent ink-setting properties, and excellent printability with little piling, can be obtained according to the above production method, but also has physical properties as newsprint paper. It is desirable to manage. The tightness is desirably 0.6 g / cm ³ or more and 0.7 g / cm ³ or less. This is the basis weight 37 g / m ² or more 45 g / m ² or less of newsprint prerequisite is required for imparting strength to withstand after appropriate printing opacity and high-speed printing, 0.6 g / cm ^If it is less than ³ , the paper surface may not withstand the tack of the ink and may peel off or the contained inorganic fine particles may fall off. On the other hand, if it exceeds 0.7 g / cm ³ , the opacity after printing may be lowered or the ink set may be deteriorated.

  The smoothness is preferably from 20 seconds to 60 seconds. The smoothness is a value measured by the Oken type smoothness meter, and is a method according to “Testing and measuring instrument in paper and printing” edited by Ministry of Finance, Printing Bureau Research Institute. When the smoothness is less than 20 seconds, the image quality is deteriorated due to the poor surface property, and the guide roller is easily soiled and blanket piling. Also, if it exceeds 60 seconds, there is a risk that it will lead to a decrease in opacity after printing and ink set failure. For the same reason, it is more preferably 20 seconds or longer and 40 seconds or shorter, and most preferably 25 seconds or longer and 35 seconds or shorter.

The contact angle of the surface is preferably 45 degrees or more and 110 degrees or less. The contact angle is defined as the contact angle one second after the water droplet is dropped. The contact angle is an index for measuring the size, and in the present invention, it is adjusted to prevent powder falling and piling, which are weak points in pigment coating. If the contact angle is less than 45 degrees, ink inking property is low, and there is a risk of powder falling off due to the action of water by dampening water and blanket piling. Further, if it exceeds 110 degrees, the surface strength may be decreased because the capability of the adhesive may be decreased. For the same reason, it is more preferable to adjust between 70 degrees and 100 degrees.
Therefore, in order to maximize the effects of the present invention, the strength of the product is 0.6 g / cm ³ or more and 0.7 g / cm ³ or less, the smoothness is 20 seconds or more and 60 seconds or less (particularly 40 seconds or less), the surface The contact angle of 45 ° to 110 ° (especially 70 ° to 100 °) is desirable.

When a water-soluble polymer such as starch or polyvinyl alcohol is used as a binder, the contact angle of the conceptual surface is generally low, for example, about 40 to 44 degrees for starch.
In such a case, methods for adjusting the contact angle of the surface to the above range include a method using a hydrophobic synthetic resin latex as a part of the binder of the coating, a method of blending a surface sizing agent in the coating, Examples thereof include a method of introducing a hydrophobic group into the water-soluble polymer binder and a method of crosslinking a water-soluble polymer bander with a crosslinking agent.

  Examples of the surface sizing agent include alkyl ketene dimer surface sizing agents, emulsion polymer surface sizing agents, olefin surface sizing agents, and styrene surface sizing agents. Specifically, the olefin sizing agent is a copolymer mainly composed of an olefinic unsaturated monomer which is a hydrophobic unsaturated monomer and a carboxy group-containing unsaturated monomer or a salt thereof. Specifically, the styrenic sizing agent is a copolymer mainly composed of a styrenic unsaturated monomer which is a hydrophobic unsaturated monomer and a carboxy group-containing unsaturated monomer or a salt thereof. The mass average molecular weight of the olefin-based surface sizing agent is preferably 1000 to 10,000, and more preferably 5000 to 7000. If the surface sizing agent used in the present invention is exemplified as a more specific copolymer, the olefin-based surface sizing agent may be ethylene / acrylic acid copolymer, isobutylene / acrylic acid copolymer, n-butylene. / (Meth) acrylic acid / (meth) acrylic acid ester copolymer, propylene / maleic acid copolymer, ethylene / maleic acid copolymer and the like. Examples of the styrene surface sizing agent include styrene / acrylic acid copolymers and styrene / maleic acid copolymers.

<Printing ink>
Ink for offset printing is composed of pigment, vehicle, and auxiliary components. Of the vehicle, about 30% of the organic solvent functions to dissolve the binder.
The environmentally friendly ink as used in the present invention is one in which at least the aromatic hydrocarbon content in the organic solvent is zero and plant-derived oil such as soybean oil is used.
As described above, soybean oil ink is a tacky ink, and the paper is required to have surface strength. In addition, it has a high viscosity and is difficult to penetrate into paper. In cold-set type offset printing, since the ink is not heated and dried to evaporate the solvent, it is necessary to quickly absorb the ink on the paper. Therefore, if the ink penetration is poor, the printing speed cannot be increased accordingly. Therefore, when using an environmentally friendly ink such as soybean oil ink that does not easily penetrate into paper, it is necessary to absorb the ink as much as possible on the surface of the paper.
The present invention is characterized in that soybean oil ink is easily absorbed by applying a specific amount of a pigment coating layer mainly composed of calcium carbonate, particularly calcium carbonate having a small particle diameter.
In addition, by making the binder 40 to 130 parts by mass with respect to 100 parts by mass of the pigment, the effects of both penetration of soybean oil ink into the paper and absorption at the surface are balanced.
Furthermore, by smoothing the coated layer of the present invention with an on-machine calender with a soft nip, the paper layer is not excessively compressed, and the soybean oil absorbing ability of the coated layer is not impaired while printing. The gloss can be increased.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In addition, throughout the present specification and in the following examples, “%” unless otherwise specified is all “% by mass”, and “part” is “part by mass”.

First, various physical property measurement methods will be described.
(ash)
A temperature of 525 ° C. and 3 hours were applied in accordance with JIS P 8251. Further, according to JIS P-8252, the calcium carbonate content was converted to calcium oxide at 900 ° C. for 3 hours, and the calcium carbonate content was determined from the difference.
(Tensity)
It was obtained from the rice tsubo and thickness by a conventional method.
(Contact angle)
Using a dynamic surface contact angle measuring device (Dynamic Absorption Tester DAT1100, manufactured by Fibro) under a 23 ° C., 50% RH atmosphere, the surface contact angle was measured 1 second after dropping a water droplet.
(Smoothness)
It was measured using an air leak type Oken type smoothness meter (Asahi Seiko Co., Ltd.) according to JAPAN TAPPI paper pulp test method No. 5B.

(Opacity after printing)
JAPAN TAPPI No. 45.

(Ink setting)
A sample mount on which newsprint paper for printing was pasted was prepared, and printing was performed using 0.5 cc of soybean oil ink (Naturalis 100 manufactured by Dainippon Ink & Chemicals, Inc.) using an RI printing tester. Printing was performed every 2 to 3 cm at regular intervals from the point where the sample touched the ink roll, and the ink roll after printing was copied onto another sheet of paper, and the density change was visually evaluated. Evaluation was performed by the following five-step evaluation. The sample of Reference Example 1 was used as a standard product.
5: Compared with the standard product, the ink density of the single-sided coated paper that transferred the surface of the newspaper printing paper for cold offset after printing is clearly lower. 4: The cold offset after printing is finished compared with the standard product The ink density of single-sided coated paper with the surface of newspaper printing paper used for printing is slightly low 3: Ink density equivalent to the standard product.
2: Compared with the standard product, the ink density of the single-sided coated paper that transfers the surface of the newspaper printing paper for printing after printing is slightly higher. 1: For cold offset after printing compared with the standard product The ink density of single-sided coated paper to which the surface of newspaper printing paper is transferred is clearly high.

(Guide roller dirt)
About the newsprint for offset printing obtained in each Example and Comparative Example, using an offset printing machine (Mitsubishi Lithopia L-BT3-1100) on which an aluminum plate made with a drawing rate of 10% (area ratio) was set, After performing black ink printing of soybean oil ink and printing 100,000 copies, the dirt on the guide roller was visually determined. Evaluation was performed by the following five-step evaluation.
<Evaluation criteria> 5 (excellent) -1 (inferior)
5: Almost no dirt is observed.
4: Slight dirt is observed.
3: Slight adhesion is observed, but there is no practical problem.
2: Dirt has adhered.
1: Dirt is significantly attached.
Those with an evaluation of less than 3 have practical problems.

(Dry surface strength)
As an index of powder falling, a sample mount on which the newspaper for offset printing obtained in each of the examples and comparative examples was pasted in the same manner as described above was prepared, and the printing ink (manufactured by T & K TOKA Co., Ltd.) was used with an RI printing tester. ) Was printed using 0.4 cc, and the degree of picking on the printed surface was visually evaluated. Evaluation was performed by the following five-step evaluation.
<Evaluation criteria>
5: No fiber is removed and no white spots occur.
4: The fibers are taken out very slightly, and white portions are slightly seen (1 to 5 places / about 36 cm ² ).
3: A level where there is no problem in practical use although fibers are partially removed. White spots section ² about 6 to 20 points / 36cm.
2: Fibers are observed on the entire surface, and the area ratio of white spots is less than 5%.
1: Fibers are removed from the entire surface and the paper surface is peeled off, and the area ratio of white areas is 5% or more.
Those with an evaluation of less than 3 have practical problems.

(Blanket Piling)
The newspaper for offset printing obtained in each Example and Comparative Example was printed on four colors using the offset printing machine, printed 5000 copies, and then deposited paper dust on the blanket non-image area. The degree was determined visually. Evaluation was performed by the following five-step evaluation.
<Evaluation criteria> 5 (excellent) -1 (inferior)
5: Little generation of paper dust is observed.
4: Generation of paper dust is slightly observed.
3: Although generation | occurrence | production of paper dust is recognized a little, it is a level which is satisfactory practically.
2: Generation of paper dust is clearly recognized.
1: A lot of paper dust is deposited on the blanket.
Those with an evaluation of less than 3 have practical problems.
The preparation method of the sample is shown below. Table 1 shows the results of evaluating the prepared samples.

<Example 1>
Base paper: Pulp slurry prepared by mixing 10 parts of softwood kraft pulp, 20 parts of thermomechanical pulp, 70 parts of deinked waste paper pulp and mixing to 70 parts of freeness 120% CSF (Canadian Standard Freeness, hereinafter simply abbreviated as CSF). Then, 0.5% of cationized starch (trade name; P3Y, manufactured by PIRAAB STARCH Co., Ltd.) per dry pulp was added, 2% of white carbon was added as a filler, and the papermaking pH was adjusted to 5 with a sulfuric acid band. The resulting paper stock was made with a gap former type (MH former) paper machine.
Coating: Calcium carbonate (A) 1.0 g / m ² , oxidized starch (Oji Ace A, manufactured by Oji Cornstarch Co., Ltd.) 0.6 g / m ² , surface sizing agent (OT25, manufactured by Arakawa Chemical Industries, Ltd.) Prepare a pigment dispersion with a solids concentration of 20% so that the concentration is 0.05 g / m ^2, and use a gate roll (manufactured by Mitsubishi Heavy Industries), and the coating amount after drying, excluding the sizing agent, is 1.6 on both sides. It was coated to a g / m ^2. While monitoring the coating amount, it was set to automatically obtain 40 g / m ^{2 of} rice paper with the base paper and coating layer combined. Here, the calcium carbonate (A) is a calcite spindle light calcium carbonate having an average particle diameter of 0.8 μm produced by a carbon dioxide method by reaction of carbon dioxide and lime milk, and is dried as it is after production. Used for paint.
Surface treatment: After drying, finish with a soft nip calender (manufactured by Kiesta) of 1 nip x 2 stacks under the condition that the smoothness is 40 seconds (At this time, the tension became 0.65 g / m ³ ) The newsprint for offset printing was obtained.

<Example 2>
Newsprint paper for offset printing was obtained in the same manner as in Example 1, except that in the coating step, coating was performed so that the coating amount of the pigment layer was 2.8 g / m ² .

<Example 3>
Newsprint paper for offset printing was obtained in the same manner as in Example 1, except that in the coating step, coating was performed so that the coating amount of the pigment layer was 0.6 g / m ² .

<Example 4>
In the coating process, newspapers for offset printing were used in the same manner as in Example 1 except that the coating liquid was calcium carbonate 0.5 g / m ² and kaolin (Miragros, manufactured by Engelhard) 0.5 g / m ^2. Got the paper.

<Example 5>
Newsprint paper for offset printing was obtained in the same manner as in Example 1, except that the surface treatment step was carried out so that the smoothness was 22 seconds (at this time, the tension was 0.62 g / cm ³ ).

<Example 6>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that the surface treatment step was performed so that the smoothness was 58 seconds (the tightness was 0.68 g / cm ^{3 at} this time).

<Example 7>
In the base paper and the coating process, the coating amount is 1.6 g / m ² , the rice tsubo is 45 g / m ² , and the smoothness is 40 seconds in the surface treatment process (at this time, the tension is 0.62 g / cm ³ ). An offset printing newsprint was obtained in the same manner as in Example 1 except that the above processing was performed.

<Example 8>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that the coating was applied so that the surface sizing agent was 0.02 g / m ² (the contact angle was 47 degrees at this time).

<Example 9>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that the coating was applied so that the surface sizing agent was 0.08 g / m ² (the contact angle was 105 ° at this time).

<Comparative Example 1>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that kaolin 0.5 g / m ² and titanium dioxide (JA-1, manufactured by Teika) 0.5 g / m ² were applied as pigments in the coating process. It was.

<Comparative example 2>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that in the coating process, coating was performed so that the coating amount of the pigment layer was 3.3 g / m ² .

<Comparative Example 3>
Newsprint paper for offset printing was obtained in the same manner as in Example 1, except that in the coating step, the coating amount of the pigment layer was 0.3 g / m ² .
The results of the above examples and comparative examples are shown in Table 1.

Reference examples are given below. In the reference example, the manufacturing apparatus or the like was changed, but the reference example was created in accordance with Example 1 in order to clarify the effect of the change requirement. If other conditions are changed, a product satisfying practicality can be obtained.
<Reference Example 1>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that in the base paper process, paper was made using an on-top former type (dynaformer) paper machine.
<Reference Example 2>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that coating was performed using a 2-roll size press machine (manufactured by Mitsubishi Heavy Industries).
<Reference Example 3>
Newspaper for offset printing was obtained in the same manner as in Example 1 except that a chilled roll calendar (manufactured by Mitsubishi Heavy Industries) was used in the surface treatment step.
<Reference Example 4>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that dry calcium carbonate (TP-123, manufactured by Okutama Kogyo Co., Ltd.) 1.0 g / m ² was applied as a pigment in the coating process.
<Reference Example 5>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that the surface treatment step was carried out so that the smoothness was 18 seconds (at this time, the tightness was 0.58 g / cm ³ ).
<Reference Example 6>
Newsprint paper for offset printing was obtained in the same manner as in Example 1, except that the surface treatment step was performed so that the smoothness was 65 seconds (at this time, the tension was 0.72 g / cm ³ ).
<Reference Example 7>
In the base paper and the coating process, the coating amount is 1.6 g / m ² , the rice tsubo is 45 g / m ² , and the smoothness is 30 seconds in the surface treatment process (at this time, the tension is 0.58 g / cm ³ ). An offset printing newsprint was obtained in the same manner as in Example 1 except that the above processing was performed.
<Reference Example 8>
Except that no surface sizing agent was added to the coating liquid and the coating process was performed so that the surface sizing agent was 0 g / m ² (the contact angle was 43 degrees at this time), the same as in Example 1. We obtained newspaper for offset printing.
<Reference Example 9>
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that the coating was applied so that the surface sizing agent was 0.10 g / m ² (the contact angle was 115 degrees at this time).
The results of the above reference examples are shown in Table 2.

上表で、ＧＲはゲートロールコーターを示し、ＣＲはチルドロールカレンダーを示す。

In the above table, GR represents a gate roll coater, and CR represents a chilled roll calendar.

Claims (8)

A pigment coating layer containing calcium carbonate is formed on both sides of the base paper having a waste paper pulp content of 60% by mass or more and an ash content of 5 to 15% by mass, and the pigment coating layer is converted to a dry solid content. Newsprint paper for offset printing with a total coating weight of 0.5 to 3 g / m ² on both sides and a rice paper weight of 37 to 45 g / m ² . The newsprint paper for offset printing according to claim 1, wherein the pigment coating layer has a binder of 40 to 130 parts by mass with respect to 100 parts by mass of the pigment. The newsprint for offset printing according to claim 1 or 2, wherein calcium carbonate is 50% by mass or more in all pigments in the pigment coating layer. The newspaper for offset printing according to any one of claims 1 to 3, wherein the contact angle of water on the surface is 45 to 110 degrees. Bulk density of the product 0.6~0.7g / cm ^3, an offset printing newsprint according to claim 1, smoothness, characterized in that from 20 to 60 seconds. 6. Newsprint paper for offset printing according to any one of claims 1 to 5, wherein the calcium carbonate used for the pigment coating layer is wet-synthesized and then blended into the paint without passing through a drying step. The newsprint paper for offset printing according to any one of claims 1 to 6, wherein the newsprint paper is for environment-friendly ink printing. A method for producing a newsprint according to any one of claims 1 to 7, wherein the base paper is made with a gap-type former, and the pigment coating layer is applied with an on-machine gate roll type coating equipment. And a method of producing newsprint for offset printing, characterized in that the surface treatment is performed with an on-machine calendar of a soft nip.