JP2007291569A - Newspaper for cold offset printing - Google Patents

Abstract

[PROBLEMS] To significantly improve ink fillability and post-printing opacity during cold offset printing using penetrable drying ink in a multicolor printing system, and causes printing troubles such as defective set-off. Provision of newspaper printing paper for cold offset having good printing workability and color printing quality without having to do so.
In a newsprint for cold offset printing in which a surface treatment agent mainly composed of a pigment and an adhesive is coated on one or both sides, dried and then smoothed, the amount of the surface treatment agent applied is Talc in a range of 0.5 to 2.4 g / m ² per side, 50 to 95 parts by mass of light calcium carbonate as a pigment in 100 parts by mass of the pigment, and an average particle diameter measured by the laser method of 2 to 12 μm; 5 to 50 parts by mass of chlorite is contained in 100 parts by mass of the pigment, the whiteness is 53 to 78%, and the Oken smoothness is 10 to 100 seconds.
[Selection figure] None

Description

  The present invention can remarkably improve ink fillability and post-print opacity in multi-color printing using a cold offset printing press, and troubles such as Nepari phenomenon, blanket piling, and set-off defects. The present invention relates to a newsprint for cold offset printing having good printing workability and color printing quality without causing occurrences of the problem.

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.

Furthermore, recent newspaper papers are required to be lighter, and accordingly, there is an increasing demand for papers that can maintain high opacity after printing. In order to meet this demand, inorganic pigments such as white carbon, calcium carbonate, titanium oxide, and talc have been used as fillers during papermaking in order to improve the opacity of paper. Moreover, although high-rate blending of DIP (deinked waste paper pulp), which is regarded as important in terms of the environment, has progressed, opacity is less likely to occur compared to mechanical pulps such as GP, RGP, and TMP. It is extremely difficult to achieve both improvement in opacity and high rate blending of DIP.

On the other hand, coated paper made by coating a base paper with a pigment and a binder having a dry weight of about 8 g / m ² or more and having a dry surface has good surface properties and is suitable for multicolor printing. Paper printing uses a printing press with a heat-setting device and oxidative polymerization drying ink, and the ink drying system differs between cold offset printing press and newspaper printing using penetrating drying ink. If the coated paper is printed on a cold offset newspaper rotary press, it may cause troubles related to printing surface quality and printing workability such as set-off failure and smearing that occur when the ink is not sufficiently dried.

A technology for providing a coating layer containing a needle pigment and a pigment having an oil absorption of 65 cc / or more is disclosed as a news paper for cold offset printing (see Patent Document 1). Although the improvement of the coating suitability is aimed at by containing the acicular pigment, the acicular pigment has a low effect of preventing the see-through, and the more it is added, the more disadvantageous it becomes for the opacity after printing. In addition, a coating layer containing a large amount of pigment having an extremely high oil absorption tends to have a weak surface strength in a wet state, and is likely to cause pigment piling on a blanket of a printing press. Furthermore, the coating layer containing a large amount of pigment with high oil absorption absorbs the vehicle components in the ink rapidly, causing a rapid rise in ink tack on the paper surface, and high tack ink adheres to the printing press roll. The paper surface was sometimes stained. The technology for improving the ink set suitability and the ink density by using dynamic pigment of the base paper and the use of kaolin and an irregular pigment with an average particle size is disclosed, but this method improves opacity. The effect is small, the ink setting becomes slow, and stickiness may occur (see Patent Document 2). Newspaper coated paper using a specific latex and water-soluble polymer as a binder and an organic pigment as the pigment is disclosed, but the organic pigment contributes to improving the blank paper opacity, but the ink absorption The contribution to opacity after printing is low due to poor properties. In addition, when the organic pigment is present on the outermost surface of the paper, wrinkles may occur at a place where friction occurs such as a fixed roll or a fixed sensor (see Patent Document 6). On the other hand, as a technique aimed at improving opacity after printing on a base paper, a technique for applying an external additive such as starch or latex to a base paper containing hydrated silicic acid that satisfies specific particle characteristics is disclosed. These internally added particles have insufficient oil absorption, and the particle diameter range is too small, resulting in a low yield on the paper machine. Although coated paper for offset printing provided with a coating layer containing chlorite is disclosed, this technology is within the coating amount range used in ordinary coated paper and fine coated paper, and cold offset. In printing, ink absorption on a printing machine becomes insufficient, and printing surface troubles such as ink back-off occur, resulting in deterioration of printing surface quality (Patent Documents 4, 5, and 6). reference).

From the above situation, in cold set type high-speed rotary printing using penetrable ink, the ink setting property is good, the printing workability is excellent, the post-printing opacity is high, and the color multicolor printing. There has been a strong demand for newspaper printing paper having printability with good color reproducibility and sharpness.
JP-A-01-174697 Japanese Patent Laid-Open No. 04-57988 Japanese Patent Laid-Open No. 02-74698 JP 2005-133226 A JP 2005-139565 A JP 2005-154933 A

The present invention can remarkably improve ink fillability and opacity after printing in cold offset printing using penetrable drying ink in a multicolor printing system, and can also prevent printing troubles such as defective set-off. It is an object of the present invention to provide a cold offset newsprint paper having good printing workability and color printing quality without occurrence.

This application includes the following inventions.
(1) In a cold offset printing newsprint coated with a surface treatment agent mainly composed of a pigment and an adhesive, dried, and then smoothed, the coating amount of the surface treatment agent is at least 0. Talc and chlorite, which are 5 to 2.4 g / m ² , light calcium carbonate as a pigment in a range of 50 to 95 parts by mass in 100 parts by mass of the pigment, and an average particle diameter measured by a laser method of 2 to 12 μm. Newsprint paper for cold offset printing, containing 5 to 50 parts by mass in 100 parts by mass, having a whiteness of 53 to 78% and an Oken type smoothness of 10 to 100 seconds.
(2) The ratio of chlorite to talc is 5 to 95% by mass, the coating amount of talc and chlorite is 0.05 to 0.5 g / m ² per side, water-soluble and / or water The newsprint for cold offset printing according to (1), comprising 30 to 70 parts by mass of a dispersible adhesive in 100 parts by mass of pigment.
(3) The newsprint for cold offset printing according to (1) or (2), wherein the surface treatment agent is applied by a film transfer system coating apparatus.
(4) Any of (1) to (3), wherein the adhesive contains a water-soluble adhesive and a water-dispersible adhesive, and contains 5 to 50 parts by mass of the water-dispersible adhesive in 100 parts by mass of the adhesive. 1. Newsprint paper for cold offset printing according to item 1.

The newspaper paper for cold offset printing according to the present invention can remarkably improve ink fillability and post-print opacity in multi-color printing using a cold offset type rotary printing press, and also has a Nepari phenomenon, blanket There is an advantage of having good printing workability and color printing quality without causing problems such as piling and set-off defects.

In the cold offset type newspaper printing using the penetrating absorption type ink, the present inventors have applied the surface treatment agent applied to the newspaper paper surface, such as opacity after printing, printability such as ink fillability, ink set, etc. The effect on the printing workability was investigated. As a result, it is important to apply a very small amount of a surface treatment agent containing a certain amount of both chlorite and talc in order for pigment coating performance to be fully demonstrated in multicolor printing. I found. Moreover, it discovered that the opacity after printing improved by making it the compounding quantity of a specific binder, and blanket piling can be suppressed simultaneously. Furthermore, it has been found that the printing surface suitability and the printing workability can be compatible by controlling the smoothness, and the present invention has been completed.

In the present invention, it is necessary that light calcium carbonate, talc, and chlorite are blended in the surface treatment agent. A combination of light calcium carbonate and chlorite alone, a combination of light calcium carbonate and talc alone, or a combination of talc and chlorite alone does not provide an effect of improving opacity after printing. When light calcium carbonate is used as a main pigment in combination with talc and chlorite, the post-printing opacity is remarkably improved by the synergistic action. After drying talc and chlorite, the surface of the particles becomes hydrophobic, which improves ink inking, and the flat pigment prevents the surface treatment agent from penetrating into the base paper even with a very small amount of coating. It is considered that the opacity after printing can be improved without sacrificing the ink set. Furthermore, talc and chlorite have different behaviors in aqueous dispersions, and it is thought that the opacity after printing is improved because it becomes easy to incorporate light calcium carbonate by the interaction between these particles in the drying process.

Light calcium carbonate includes acicular, columnar, spherical, spindle, and cubic shapes, and any of them can be used in the present invention, but calcite light calcium carbonate, that is, cubic and spindle-shaped preferable. The reason why calcite light calcium carbonate is suitable is not clear, but it is thought that calcite light calcium carbonate tends to have a rough structure in the coating layer compared to aragonite calcium carbonate or vaterite calcium carbonate. It is done. The calcite calcium carbonate can be identified by an X-ray diffraction apparatus (form: RINT-2200, manufactured by Rigaku Corporation). The light calcium carbonate is preferably blended in an amount of 50 to 95 parts by weight, more preferably 70 to 90 parts by weight, based on 100 parts by weight of the pigment. If it is less than 50 parts by mass or more than 95 parts by mass, the synergistic effect of the combination of the three pigments will not be seen.

In the present invention, the average particle diameter of talc and chlorite is preferably 2 to 12 μm. If the average particle diameter is less than 2 μm, it is difficult for light calcium carbonate to be taken in between talc and chlorite particles, and the effect of improving opacity after printing becomes low. When it exceeds 12 μm, the coating property of the paint deteriorates, and uniform coating becomes difficult. Furthermore, since the surface strength is reduced, blanket piling may occur during cold offset printing. In addition, this average particle diameter means the median diameter obtained by measuring a particle size distribution with a laser diffraction type particle size distribution measuring apparatus (type: SALD-2000, manufactured by Shimadzu Corporation).

In the present invention, the total amount of talc and chlorite is preferably 5 to 50 parts by mass in 100 parts by mass of the pigment. When the blending amount is less than 5 parts by mass, the effect of the combined use of the three types of pigments is hardly seen, as in the case where only light calcium carbonate is applied in the opacity after printing. Moreover, it is preferable that chlorite is mix | blended in the ratio of 5-95 mass% with respect to talc. When the chlorite ratio is less than 5% by mass or more than 95% by mass, the interaction between particles does not work sufficiently, and the effect of improving opacity after printing is considered to be small. In addition, it is preferable that the coating amount of talc and chlorite is 0.05-0.5 g / m < ² > per single side | surface. The blending amount of all pigments including talc and chlorite needs to be within the above range, and the coating amount needs to be within this range. Is less than 0.05 g / ^{m 2,} without affecting the well after printing opacity even when they range amount is from 5 to 50 parts by weight in 100 parts by weight of the pigment, while more than 0.5 g / ^{m 2} In some cases, the set-off is adversely affected. The pigment used in combination with light calcium carbonate, talc, and chlorite is not particularly limited. For example, heavy calcium carbonate, kaolins, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white , Aluminum silicate, Diatomaceous earth, Calcium silicate, Magnesium silicate, Hydrated silicic acid, Colloidal silica, Colloidal alumina, Pseudoboehmite, Aluminum hydroxide, Alumina lithopone, Zeolite, Hydrous halloysite, Magnesium carbonate, Magnesium hydroxide, Porous magnesium carbonate And white inorganic pigments such as porous alumina, styrene or acrylic hollow, honey-type plastic pigments, organic pigments such as polyethylene beads, urea resins, and melamine resins. In the case of newspaper rotation that is operated at high speed, if the dynamic friction coefficient is low, the web tension is less likely to be applied and wrinkles and paper flow may occur. Therefore, the dynamic friction coefficient is preferably in the range of 0.45 to 0.65. The dynamic friction coefficient adjustment method can be adjusted not only by adjusting the pigment coating amount, but also by commonly used lubricants such as fatty acid metal soaps such as zinc stearate and calcium stearate, alkyl ketene dimers, and ethylene compounds. Deterioration of printing workability such as background stains is likely to occur, and opacity after printing may be affected. As a method of adjusting the dynamic friction coefficient without reducing the printing workability and the opacity after printing, it is preferable to blend kaolin, which is a plate-like pigment, into the paint. As kaolin, kaolin such as primary kaolin, secondary kaolin, fine-grain kaolin, engineered kaolin and the like is suitable for reducing the dynamic friction coefficient. Firing kaolin and chemically structured kaolin can be used to increase the dynamic friction coefficient.

In the present invention, an adhesive is blended with the surface treatment agent together with the pigment in order to avoid troubles related to surface strength typified by piling. As an adhesive for increasing both surface strength and opacity, a water-soluble adhesive is most preferable. In order to improve adhesion between pigments, a water-dispersible adhesive is preferably blended, and the water-soluble adhesive and the water-dispersible adhesive may be used alone or in combination. These adhesives are particularly preferably used because they have good compatibility with pigments and hardly cause coarse aggregation during coating. The water-soluble adhesive is preferable because it has a high adhesive ability with the fiber that is a hydrophilic component, and strongly adheres fine fibers that easily fall off from the paper surface when the coating amount is small. As the water-soluble adhesive, starch is most preferable. Examples of starches include enzyme-modified starch, oxidized starch, etherified starch, esterified starch, cationized starch, and hydrophobic starch. It is also possible to use ordinary coated paper binders such as water-soluble cellulose compounds such as carboxymethylcellulose, methylcellulose and hydroxyalkylcellulose, polyvinyl alcohol compounds and polyacrylamides, proteins such as casein, soybean protein, and synthetic proteins. One or more of these may be used in combination. Synthetic latexes such as acrylic latex, vinyl acetate latex, styrene butadiene latex, acrylonitrile butadiene latex, and methyl methacrylate butadiene latex are used as water-dispersible adhesives. Among them, styrene butadiene latex has high printing quality and printing workability. It is preferably used to improve. Although there is no restriction | limiting in particular as Tg of these latex, The thing of 20 degrees C or less is preferable in consideration of the balance of surface strength and Nepari, and the thing of 0 degrees C or less is further more preferable. Those in this Tg range exhibit tackiness at room temperature and have good adhesion to the pigment / filler, but the polarities of the molecules are very low and adhesion to strong hydrophilic cellulose fibers is difficult. It is used in combination with starch that has high adhesive strength to the fiber, and starch alone has the function of covering adhesion to weak pigments / fillers. In the case of a low coating amount as in the present invention, the effect of the interaction between the latex and starch may be greatly affected. As the latex, a core-shell type can also be used. In this case, a core having a Tg of 0 ° C. or less is preferably used. A latex called a concentration gradient type, in which the composition from the inside of the particle to the outside continuously changes, has the same effect. In this case, an average Tg of 0 ° C. or less is preferable. The water-dispersible adhesive is desirably used in combination with a water-soluble adhesive. In this case, the blending amount of the water-dispersible adhesive per 100 parts by mass of the adhesive is preferably 5 to 50 parts by mass, and 10 to 30 parts by mass. Is more preferable. If the water-dispersible adhesive ratio is less than 5 parts by mass, the adhesion to pigments and fillers is insufficient, and troubles such as piling are likely to occur on the printing press. When it exceeds 50 parts by mass, the amount of the water-soluble adhesive is relatively reduced, the surface strength is lowered, and the fibers are easily taken off. In addition, a large amount of adhesive is present in the gaps between the pigment particles, and the gaps are filled and the absorption of the vehicle component in the ink is hindered, so that the opacity after printing may be lowered. In addition, although the contact angle with respect to the water of the paper surface can be improved by mix | blending a water dispersible adhesive agent, it is desirable that the contact angle 0.1 second after water dripping is 80 degrees or more. When the contact angle 0.1 seconds after water dripping is 80 ° or more, sufficient affinity for the ink is ensured and the ink deposition property is good. In addition, the wet surface strength required in cold offset newspaper printing can be easily obtained. These adhesives and additives are preferably anionic solutions or dispersions. When a cationic binder or additive is used, the light calcium carbonate secondary agglomerates may further agglomerate to form coarse agglomerates, and the viscosity of the surface treatment agent tends to become unstable. .

The ratio of the adhesive to 100 parts by mass of the pigment is desirably 30 parts by mass or more and less than 70 parts by mass. When the coating amount is small as in the present application, the ratio of the binder penetrating into the base paper increases, and when it is less than 30 parts by mass, sufficient adhesion to the coating pigment and paper surface fibers cannot be obtained. On the other hand, at 70 parts by mass or more, although the adhesion between the coating pigment and the paper surface fiber is sufficient, the gap between the coating pigments is filled with the binder, and the ink absorbability is hindered. Furthermore, there is a possibility that the amount of binder penetrating into the base paper increases and the opacity decreases.

The surface treatment agent mainly composed of a pigment and an adhesive preferably has a coating amount of 0.5 to 2.4 g / m ² , preferably 0.5 to 1.4 g / m ² per side. More preferably, it is more preferable that it is 0.7-1.4 g / m < ² >. If it is less than 0.5 g / m ² , the effect of improving the opacity after printing is small, and if it exceeds 2.4 g / m ² , the ink absorption is hindered and the ink setting becomes slow. May cause problems.

In the present invention, the Oken smoothness needs to be 10 to 100 seconds. Higher surface smoothness is preferable because ink deposition is better, but if it is 100 seconds or longer, ink absorbability is extremely lowered, and troubles such as set-off are likely to occur. On the other hand, if the time is less than 10 seconds, the surface is too rough, the ink deposition is deteriorated, and the stamped surface tends to be rough. By setting the Oken type smoothness to 10 to 100 seconds, more preferably 15 to 60 seconds, the effect of the surface treatment agent can be sufficiently exerted.

As an apparatus for applying the coating composition to the base paper of offset printing paper, for example, an ink line or vertical to roll size press, a blade metalling size press, a rod metalling size press, a roll coater such as a gate roll coater, trailing, Known and publicly used equipment such as bevel type, bent type blade coater, rod blade coater, bar coater, air knife coater, curtain coater, spray coater, gravure coater such as flexible, roll application, fountain application, short dwell etc. are used as appropriate However, a film transfer type coating apparatus such as a blade metering size press, a rod metering size press, or a gate roll coater is preferably used. The film transfer type coating apparatus is difficult to penetrate the coating liquid even at a low concentration, and can effectively keep the surface treatment agent on the paper surface. These coating machines may be on-machine or off-machine, but on-machine coating is preferred in consideration of productivity. 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, and infrared heater drying, are employable, for example.

Regarding the production of the cold offset newspaper printing paper of the present invention, after forming the coating layer of the coating composition, smoothing treatment is performed in various calendar devices. As such a calendar device, a super calender is used. Commonly used calendar devices such as a soft calendar, a gloss calendar, a compact calendar, a mat super calendar, and a mat calendar are appropriately used. As the calender finishing conditions, the temperature of the rigid roll, the calender pressure, the number of nips, the roll speed, the moisture before the calender, etc. are appropriately selected according to the required quality. Furthermore, the calendar device has 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 metal roll or a roll whose surface is mirror-finished with hard chrome plating or the like. As the elastic roll, a roll formed by molding a resin roll such as urethane resin, epoxy resin, polyamide resin, phenol resin, polyacrylate resin, cotton, nylon, aramid resin or the like is used as appropriate. It should be noted that it is also possible to use a suitable combination of a water coating device, an electrostatic humidifier, a steam humidifier, and the like for humidity control and humidification of the coated paper after finishing with a calendar.

The base paper of the cold offset newspaper printing paper according to the present invention is obtained as follows. First, as a raw material pulp, chemical pulp (NBKP, LBKP, etc.), mechanical pulp (GP, CGP, RGP, PGW, TMP, etc.), and waste paper pulp (DIP, etc.) are mixed as appropriate to prepare a stock. Is done. If a large amount of waste paper pulp is blended, the ink absorbability of the base paper tends to be reduced, but in the present invention, it is preferable to blend 50% or more of waste paper pulp, and to blend 60% or more in order to perform surface treatment with high ink absorptivity. Is more preferable. Next, a filler such as white carbon, clay, amorphous silica, talc, titanium oxide, or calcium carbonate is added to the paper as necessary, but is added so that the ash content in the paper is 5 to 15%. Is preferable, and it is more preferable to add so that it may become 7 to 11%. A higher ash content in the paper is preferable because the opacity is higher, but an excessively high ash content causes a decrease in stiffness and may cause problems such as wrinkles and stacker jamming on the printing press. In addition, generally known and commonly used papermaking chemicals such as paper strength enhancers, yield improvers, reinforced rosin sizing agents, internal sizing agents such as emulsion sizing agents, water resistance agents, and UV protection agents are added as necessary. A base paper is produced by making paper with a conventionally used paper machine. The papermaking pH is not particularly limited, but acidic to neutral pH = 4-7 is economically preferable. 52 g / ^{m 2} or less as a product basis weight, and more preferably when the 35~45g / ^{m 2,} the effect of the present invention as desired is very remarkably exhibited particularly desirable. The newspaper for cold offset printing thus obtained is subjected to a surface smoothing process by calendar feeding. In that case, machine calender finishing by a double-sided metal roll and soft calender finishing by passing paper through a pressure nip composed of a metal roll and an elastic roll are appropriately performed. The physical properties of this base paper need to be sufficient to allow penetrating and drying ink to be printed on a cold set type high-speed rotary press, and have physical strength such as tensile strength, tear strength, and elongation equivalent to that of general newsprint. I just need it.

The higher the whiteness of the newspaper printing paper for cold offset of the present invention, the higher the whiteness of the printed color contrast, so it is better for color printing.However, if it is too high, the printing on the back side can be seen through, and the print quality deteriorates. End up. Specifically, the whiteness is 53 to 78%, and 55 to 70% is more preferable. Moreover, the higher the opacity after printing, the better, and it is preferably 88% or more, more preferably 90% or more. A low opacity after printing is not preferable in the case of newsprint that prints on both sides because the printing quality on the back side is lowered. The newsprint paper for cold set offset printing according to the present invention has excellent printability, and in particular, when printing in multi-color, there is no thickening of halftone dots and little back-through, so that a high-quality image can be obtained.

The present invention will be specifically described below with reference to examples. Of course, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example show a mass part and mass%, respectively.
The following physical properties were measured for the cold offset newsprint papers as Examples and Comparative Examples obtained as described below, and the results are shown in Table 1.

(Average particle size)
Laser diffraction particle size distribution analyzer (type: SALD) for pigment slurry of talc or chlorite slurry mixed with 0.2% by mass of polyacrylic acid soda dispersant (trade name; Aron T50, manufactured by Toagosei Co., Ltd.) -2000, manufactured by Shimadzu Corporation), and the median diameter was defined as the average particle diameter.

(Whiteness)
The whiteness of the cold offset newsprint in the present invention was measured by the method described in ISO 3688 using a spectral whiteness colorimeter (manufactured by Suga Test Instruments Co., Ltd.).

(Dynamic friction coefficient)
Conforms to JIS P 8147.
Measurement at front and back-vertical and vertical, with a tensile speed of 200 mm / min.

(Contact angle)
About the newsprint for offset printing obtained in each Example and Comparative Example, using a dynamic surface contact angle measuring device (Dynamic Absorption Tester DAT1100, manufactured by Fibro) at 23 ° C. and 50% RH atmosphere, The surface contact angle 0.1 seconds after dropping was measured.

(Smoothness)
JAPAN TAPPI No. Measured with 5 Kenken type smoothness tester.

(Opacity after printing)
JAPAN TAPPI No. 45.

(Blanket Piling)
The newsprint paper for offset printing obtained in each of the examples and comparative examples was printed on a paper wire side by color four-color single-sided printing using an offset printer (Mitsubishi Lithopia L-BT3-1100), and 5000 copies were printed. After that, the deposit on the first blanket non-image area was collected with a PET transparent tape, and the deposit area ratio was measured with an image analyzer (DA-6000, manufactured by Oji Scientific Instruments). Evaluation was performed by the following five-step evaluation.
<Evaluation criteria>
5: The area ratio is 0.5% or less, and the degree of paper powder accumulation is clearly low 4: The area ratio exceeds 0.5 and is 1.0% or less, and the degree of paper powder accumulation is slightly low 3 : The area ratio exceeds 1.0 and is 3.0% or less, and the degree of paper dust accumulation is practically acceptable. Level 2: The area ratio exceeds 3.0 and is 5.0% or less. 1 is slightly high 1: the area ratio is over 5.0%, and the degree of paper dust accumulation is clearly high.

(Ink set)
The cold offset newsprint paper obtained in each of the examples and comparative examples was cut into strips, and a sample paper (OK special art post 256 g / m ² ) was attached side by side. Newspaper printing ink (NEWS WEBMASTER / process ink G2: Sakata Inx Co., Ltd.) for offset rotary press with the corresponding metal roll in the RI printing tester (made by Ishikawajima Industrial Machinery Co., Ltd.) with the rubber roll for ink kneading set on the 4th cylinder Manufactured) 0.5 cc kneaded, moved the ink kneading rubber roll to the second cylinder, and newly installed a rubber roll wrapped with relatively smooth one-side coated paper for ink transfer on the fourth cylinder, Printing is performed on the second cylinder. When the 4th roll was touched, the rotation was temporarily stopped, and from there, the ink was transferred to the 4th roll by 2 cm at regular intervals, and the transfer density change was visually evaluated. Evaluation was performed in five stages. In the following, the reference product is the cold offset printing paper obtained in Comparative Example 1.
<Evaluation criteria>
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.

(Neppali)
For the newsprint for offset printing obtained in each example and comparative example, an offset printing machine (Mitsubishi Lithopia L-BT3-1100) in which an aluminum plate having only a non-image area and a blanket (DAY blanket 8891 manufactured by DAY International) was set was used. Using this, water printing was performed on all the cylinders 1 to 4 without applying ink, and after 200 copies were printed, the water supply was stopped, and the degree of sticking of newsprint paper to the blanket was visually determined. Evaluation was performed by the following five-step evaluation.
<Evaluation criteria>
5: No fiber removal occurs.
4: A very small amount of fiber was removed.
3: A level where there is no problem in practical use although fibers are removed.
2: Paper layer breakage occurred in part.
1: Paper layer breakage occurred on the entire surface.
Those with an evaluation of less than 3 have practical problems.

Manufacture of newsprint base paper (A) for cold offset printing 10 parts of softwood bleached kraft pulp (NBKP), 26 parts of thermomechanical pulp (TMP), 64 parts of newspaper deinked pulp (DIP) containing 40% leaflet Then, cationized starch (trade name: P3Y, manufactured by PIRAAB STARCH Co. Ltd) 0.5%, neutral rosin sizing agent (trade name: N815, Arakawa Chemical Co., Ltd.) 0.8%, talc (trade name; made by Mistron, made by Nippon Mistron Co., Ltd.) as 2%, white carbon (own product) as 2%, all of them in the proportion of dry pulp mass% was added, after adjusting the paper making pH to 6.5 with aluminum sulfate, the resulting stock was paper in the gap former paper machine, rice basis 42.0 g / ^{m 2} To obtain a newsprint base paper for over field offset.

Production of base paper for cold offset printing (B) 10 parts of softwood bleached kraft pulp (NBKP), 26 parts of thermomechanical pulp (TMP), 64 parts of newspaper deinked pulp (DIP) containing 40% leaflet Then, cationized starch (trade name: P3Y, manufactured by PIRAAB STARCH Co. Ltd) 0.5%, neutral rosin sizing agent (trade name: N815, Arakawa Chemical Co., Ltd.) 0.8%, talc (trade name; made by Mistron, made by Nippon Mistron Co., Ltd.) as 2%, white carbon (own product) as 2%, all of them in the proportion of dry pulp mass% was added, after adjusting the paper making pH to 6.5 with aluminum sulfate, the resulting stock was paper in the gap former paper machine, rice basis 40.5 g / ^{m 2} To obtain a newsprint base paper for over field offset.

Manufacture of newsprint base paper (C) for cold offset printing 10 parts of softwood bleached kraft pulp (NBKP), 26 parts of thermomechanical pulp (TMP), 64 parts of newspaper deinked pulp (DIP) containing 40% leaflet Then, cationized starch (trade name: P3Y, manufactured by PIRAAB STARCH Co. Ltd) 0.5%, neutral rosin sizing agent (trade name: N815, Arakawa Chemical Co., Ltd.) 0.8%, talc (trade name; made by Mistron, made by Nippon Mistron Co., Ltd.) as 2%, white carbon (own product) as 2%, all of them in the proportion of dry pulp mass% was added, after adjusting the paper making pH to 6.5 with aluminum sulfate, the resulting stock was paper in the gap former paper machine, rice basis 43.0 g / ^{m 2} To obtain a newsprint base paper for over field offset.

Manufacture of newsprint base paper (D) for cold offset printing 10 parts of softwood bleached kraft pulp (NBKP), 26 parts of thermomechanical pulp (TMP), 64 parts of newspaper deinked pulp (DIP) containing 40% leaflet Then, cationized starch (trade name: P3Y, manufactured by PIRAAB STARCH Co. Ltd) 0.5%, neutral rosin sizing agent (trade name: N815, Arakawa Chemical Co., Ltd.) 0.8%, talc (trade name; made by Mistron, made by Nippon Mistron Co., Ltd.) as 2%, white carbon (own product) as 2%, all of them in the proportion of dry pulp mass% was added, after adjusting the paper making pH to 6.5 with aluminum sulfate, the resulting stock was paper in the gap former paper machine, rice basis 37.5 g / ^{m 2} To obtain a newsprint base paper for over field offset.

Example 1
70 parts as a solid content of light calcium carbonate (trade name; Brilliant S15, manufactured by Shiraishi Kogyo Co., Ltd.) as a pigment, and talc (trade name: talc NTP2, manufactured by Nippon Talc Co., Ltd., average particle size: 6.6 μm) as a solid content. 3 parts, 27 parts chlorite (trade name: IRK-C1, manufactured by Iriki Kaolin Co., Ltd., average particle size 6.0 μm) as solids, and oxidized corn starch gelatinized and dissolved as an adhesive (trade name: Oji Ace A) 50 parts as the solid content of Oji Cornstarch Co., Ltd., 5 parts of the olefin surface sizing agent (trade name: OT25, manufactured by Arakawa Chemical Industries, Ltd.) as the solid content, and a solid content concentration of 20% the paint was prepared, which on both sides of the base paper (a), the coating amount after drying became per side 0.78 g / m ² using a gate roll coater Uni coating, after drying, through a soft nip calender, the actual weight of 43.6 g / m ^2, Oken type smoothness was obtained cold offset printing newsprint 37 seconds.

Example 2
As the adhesive of Example 1, the amount of oxidized corn starch was 40 parts, the styrene butadiene latex (trade name: T2635R, manufactured by JSR Corporation) was 10 parts, the surface sizing agent was not used, and the coating amount after drying was one side. Cold offset printing newsprint paper having an actual amount of 43.5 g / m ² and a Oken type smoothness of 37 seconds was obtained in the same manner as in Example 1 except that the amount was 0.75 g / m ² per unit.

Example 3
As a pigment of Example 2, 70 parts by weight of light calcium carbonate (trade name; Brilliant S15, manufactured by Shiraishi Kogyo Co., Ltd.), talc (trade name; talc NTP2, manufactured by Nippon Talc Co., Ltd., average particle size: 6.6 μm) In the same manner as in Example 2, except that the solid content was 27 parts and the chlorite (trade name IRK-C1, manufactured by Irika Kaolin Co., Ltd., average particle size 6.0 μm) was 3 parts. A news paper for cold offset printing having an amount of 43.6 g / m ² and a Oken type smoothness of 38 seconds was obtained.

Example 4
The actual amount is 43.6 g / m ² and the Oken smoothness is 38 seconds, except that the light calcium carbonate (A) prepared by the following method is used as the light calcium carbonate of Example 2. A newsprint for cold offset printing was obtained.

(Production of light calcium carbonate (A))
Light calcium carbonate was synthesized using a carbonation reaction between calcium hydroxide and carbon dioxide to obtain a light calcium carbonate aggregate slurry having a solid content concentration of 25% and an average particle size of 4.7 μm. The primary particles of the light calcium carbonate aggregate were calcite-type spindle-shaped light calcium carbonate having a major axis of about 1.5 μm, and formed secondary particles with an average particle size of 4.7 μm. After adding 0.8 parts of a dispersant (trade name; Aron T50, manufactured by Toagosei Co., Ltd.) to this calcium carbonate slurry, a processing flow rate is obtained using a horizontal sand grinder (trade name; UVM-60, manufactured by Imex Corporation). A light calcium carbonate slurry was obtained by pulverization at 9 L / min. The average particle size of this pulverized product measured after ultrasonic treatment for 10 minutes was 0.68 μm.

Example 5
Actual amount 43.6 g / m ² , king, except that aragonite acicular light calcium carbonate (trade name: TP-123CS, manufactured by Okutama Kogyo Co., Ltd.) was used as the pigment of Example 2. A news paper for cold offset printing having a polishing smoothness of 39 seconds was obtained.

Example 6
The actual amount of 43.6 g / s in the same manner as in Example 2 except that the paint solid content concentration of Example 2 was 27%, the base paper (B) was used, and the coating amount was 1.5 g / m ² per side. A newsprint for cold offset printing of m ² was obtained.

Example 7
As the adhesive of Example 2, the amount of oxidized corn starch was 15 parts, the styrene butadiene latex was 20 parts, and the coating amount after drying was 0.68 g / m ² per side. A news paper for cold offset printing having an amount of 43.4 g / m ² and a Oken type smoothness of 39 seconds was obtained.

Comparative Example 1
100 parts as the solid content of gelatinized and dissolved oxidized corn starch (trade name: Oji Ace A, manufactured by Oji Cornstarch Co., Ltd.), and olefin-based surface sizing agent (trade name: OT25, manufactured by Arakawa Chemical Industries, Ltd.) As a solid content, 5 parts are added to prepare a paint having a solid content concentration of 10%. The coating amount after drying using a gate roll coater on both sides of the base paper (C) is 0.3 g / per side. m ² and so as coated and dried to actual amount 43.6 g / ^{m 2,} Oken type smoothness was obtained cold offset printing newsprint 36 seconds.

Comparative Example 2
The pigment of Example 2 is 100 parts of light calcium carbonate, except that talc and chlorite are not used, and in the same manner as Example 2, the actual amount is 43.5 g / m ² and the Oken smoothness is 38 seconds. A newsprint for cold offset printing was obtained.

Comparative Example 3
The pigment of Example 2 was 70 parts of light calcium carbonate and 30 parts of talc, and was the same as Example 2 except that chlorite was not used. The actual amount was 43.5 g / m ² , and the Oken type smoothness was 37. A news offset paper for cold offset printing was obtained.

Comparative Example 4
The pigment of Example 2 was changed to 70 parts of light calcium carbonate and 30 parts of crotite, and in the same manner as in Example 2 except that talc was not used, the actual amount was 43.5 g / m ² , and the Oken smoothness was 38 seconds. The news paper for cold offset printing was obtained.

Comparative Example 5
As the adhesive of Example 2, the amount of oxidized corn starch was 60 parts, 10 parts of styrene butadiene latex was used, except that the base paper (C) was used and the coating amount after drying was 0.34 g / m ² per side. In the same manner as in Example 2, a news offset paper for cold offset printing having an actual amount of 43.7 g / m ² and a Oken type smoothness of 38 seconds was obtained.

Comparative Example 6
The actual amount of 43.5 g / m was the same as in Example 2 except that the base paper (A) of Example 2 was replaced with the base paper (D) and the coating amount after drying was changed to 3.0 g / m ² per side. ^2. Newspaper paper for cold offset printing having a Oken type smoothness of 38 seconds was obtained.

Comparative Example 7
Cold offset printing newsprint with an actual amount of 43.5 g / m ² was obtained in the same manner as in Example 2 except that the soft nip calender conditions were changed and the Oken smoothness was changed to 120 seconds.

Comparative Example 8
As a pigment of Example 2, 70 parts as a solid content of light calcium carbonate (trade name; Brilliant S15, manufactured by Shiraishi Kogyo Co., Ltd.), talc (trade name: Talc D-3, manufactured by Katsuyama Industrial Co., Ltd., average particle size 16. 0 μm) was 3 parts as a solid content, and Chlolite (trade name IRK-C1, manufactured by Irika Kaolin Co., Ltd., average particle size 6.0 μm) was 27 parts as a solid content, and was the same as in Example 2. Thus, a news paper for cold offset printing having an actual amount of 43.6 g / m ² and a Oken type smoothness of 45 seconds was obtained.

Claims (4)

In a news paper for cold offset printing in which a surface treatment agent mainly composed of a pigment and an adhesive is applied on one or both sides, dried and then smoothed, the coating amount of the surface treatment agent is 0. Talc and chlorite, which are 5 to 2.4 g / m ² , light calcium carbonate as a pigment in a range of 50 to 95 parts by mass in 100 parts by mass of the pigment, and an average particle diameter measured by a laser method of 2 to 12 μm. Newsprint paper for cold offset printing, containing 5 to 50 parts by weight in 100 parts by weight, having a whiteness of 53 to 78% and a Oken type smoothness of 10 to 100 seconds The ratio of the chlorite to talc is 5 to 95% by mass, the coating amount of the talc and chlorite is 0.05 to 0.5 g / m ² per side, water-soluble and / or water-dispersible adhesion The newsprint for cold offset printing according to claim 1, wherein the agent is contained in an amount of 30 to 70 parts by mass in 100 parts by mass of the pigment. The newsprint for cold offset printing according to claim 1 or 2, wherein the surface treatment agent is applied by a film transfer system coating apparatus. The said adhesive agent contains a water-soluble adhesive agent and a water-dispersible adhesive agent, and contains 5-50 mass parts of water-dispersible adhesive agents in 100 mass parts of adhesive agents. 1. Newsprint paper for cold offset printing according to item 1.