JP5243009B2 - Newspaper and production method thereof - Google Patents

Description

The present invention relates to newsprint and a method for manufacturing the same . More specifically, for example, high-speed papermaking of, for example, a paper making speed of 1300 m / min or more is possible, and while being compatible with high-speed offset rotary printing of, for example, 200,000 copies / hour, the weight is light, no generation of paper dust, and no problem. The present invention relates to a newsprint having excellent transparency, particularly printing opacity, and a method for producing the same .

  Usually, newsprint paper is used as a filler to improve optical properties such as opacity and whiteness, as well as to improve smoothness and printability, and to improve operability during printing (increased friction coefficient). Acid is mainly used.

  Conventionally, as an industrial production technique of hydrated silicic acid, a method of neutralizing sodium silicate with a mineral acid has been known as a typical technique. However, many proposals have been made for improvement means for a long time. For example, a method of neutralizing by adding mineral acid in two steps, a multi-step neutralization method, a method of controlling the concentration of sodium silicate and sulfuric acid to be reacted, the addition rate of sulfuric acid, diluting sodium silicate, etc. Examples thereof include a method in which sodium sulfate is added to the liquid in advance and then a neutralization reaction is performed.

  Through control of the reaction by these methods, a hydrated silicic acid having a large oil absorption amount and pore volume can be obtained, and the effect of preventing paper breakthrough has been considerably improved. However, although the primary particles of the hydrated silicic acid to be produced have a relatively uniform particle size, the particle size is very small and in most cases does not exist in the shape of the primary particles and agglomerates. Thus, secondary particles are formed. Such secondary particles have a wide particle size distribution at the time of use, many coarse particles, and contain agglomerates. Therefore, in recent news paper weight reduction, high-speed papermaking, and high-speed offset rotary printing, quality degradation such as opacity, paper dust, and printing opacity is a problem.

  As a countermeasure against the above-mentioned problem of decreasing opacity, the hydrated silicic acid slurry is classified and / or pulverized using a wet classifier and / or a wet pulverizer, and the proportion of particles having a particle diameter of 1 to 30 μm is 80 mass. %, And the proportion of particles of 70 μm or more is 0.4% by mass or less, preferably 0.05% by mass. A manufacturing method has been proposed (see Patent Document 1).

  However, even if the ratio of fine particles and coarse particles in the hydrated silicic acid slurry is specified as in the technique disclosed in Patent Document 1, it exists on the surface of the paper due to the wet end and addition of various chemicals in the paper making stage. The amount of hydrated silicic acid to be adjusted or the formation of agglomerates of fine particles and coarse particles due to chemicals cannot be prevented. It does not lead to.

  In addition, paying attention to specifying the particle characteristics of hydrated silicic acid in detail, after confirming that hydrated silicic acid having pore volume and average particle diameter in a specific range exhibits filler performance exceeding expectations. Further, the production technology has been elucidated, and a hydrated silicic acid for paper fillers excellent in the effect of preventing the breakthrough and the filler yield and a method for producing the same have been proposed (see Patent Document 2).

  However, the technique disclosed in Patent Document 2 also adjusts the amount of hydrated silicic acid present on the paper surface by the addition of wet end and various chemicals in the paper making stage, as in the technique disclosed in Patent Document 1. In addition, the formation of agglomerates of fine particles and coarse particles due to the drug cannot be prevented, and the above problem cannot be solved sufficiently.

  Therefore, instead of specifying the filler to be included in the newsprint, by analyzing the ash and specifying the filler contained from the ash, newspaper that has high opacity and does not reduce the paper strength with a small amount of filler is obtained. A technique has been proposed (see Patent Document 3).

  However, although the nature of the filler contained in the paper can be specified from the ash by the technique disclosed in Patent Document 3, since the printing itself is performed on the paper surface, the presence of the filler in the thickness direction of the paper is not considered. In actual operation, the technology has a problem that it cannot be used as an index because it fluctuates due to the effects of paper machine characteristics, raw materials that change daily, the circulation white water environment in the system, and the like.

  Furthermore, apart from the trial regarding the filler to be added internally, by applying a surface treatment agent containing light calcium carbonate and a pigment composed of hydrated silicic acid having a predetermined particle diameter on the newspaper paper surface, the printing opacity is high, There has been disclosed a technique for obtaining newsprint paper that has both good printing quality and printing workability, which is less likely to cause plate wear problems (see Patent Document 4).

However, as described in Patent Document 4, in the means for applying the surface treatment agent, for example, in high-speed papermaking exceeding 1300 m / min or high-speed offset rotary printing at 200,000 copies / hour, wear / deterioration of papermaking equipment. There is a risk that paper dust and paper breakage may occur due to friction between the surface of the pigment coating layer and various rolls. On the other hand, to make the coating layer firm, it is necessary to drastically modify the paper machine, improve the coating equipment, and increase the drying capacity to dry the coating layer, resulting in excessive capital investment. In addition, when ink that is osmotically dried, such as newspaper offset printing ink, is used, the solvent is accelerated by the paper layer and the solute tends to remain on the paper surface. A problem occurs.
Japanese Patent Publication No. 01-060183 Japanese Patent Laid-Open No. 08-091280 Japanese Patent Application Laid-Open No. 2000-273796 JP 2006-233394 A

The present invention has been made in view of the background art described above. For example, high-speed papermaking such as a papermaking speed of 1300 m / min or more is possible, and for example, high-speed offset rotary printing such as 200,000 copies / hour is also possible. An object of the present invention is to provide a newsprint that is light in weight, does not generate paper dust, and has excellent opacity, particularly printing opacity, and a method for producing the same.

The present invention
A method for producing newsprint paper comprising a base paper in which hydrated silicic acid is internally added as a filler, and having a basis weight of 36 to 50 g / m ² in accordance with JIS P 8124 ,
The hydrated silicic acid is obtained without a drying step after the reaction,
The hydrated silicic acid is diluted in advance to a concentration of 2 to 3% by mass to prepare a diluted solution, and after adding the diluted solution to the raw pulp at the front stage of the screen, paper is made to produce a base paper,
Size of detection area of silicon analyzed by aggregated particles of hydrated silicate in surface analysis of paper surface using X-ray microanalyzer with X-ray acceleration voltage of 8 kV and diffusion region of 1 μm , The area ratio in the predetermined region of the aggregate particles having a particle diameter of 20 μm or more corresponding to the detection region is adjusted to be 10% or less.
A newspaper having a basis weight of 36 to 50 g / m ² in accordance with JIS P 8124, comprising a method for producing newsprint paper, and a base paper in which hydrated silicic acid is internally added as a filler. Paper,
The hydrated silicic acid is obtained without a drying step after the reaction,
The base paper is produced by adding a diluted solution prepared by diluting the hydrated silicic acid to a concentration of 2 to 3% by mass in advance to the raw pulp before the screen, and then making paper.
Size of detection area of silicon analyzed by aggregated particles of hydrated silicate in surface analysis of paper surface using X-ray microanalyzer with X-ray acceleration voltage of 8 kV and diffusion region of 1 μm The area ratio in the predetermined area | region of the aggregate particle | grains whose particle diameter according to a detection area is 20 micrometers or more is 10% or less, It is related with the newsprint.

According to the present invention, for example, high-speed papermaking of, for example, a papermaking speed of 1300 m / min or more is possible, and while being compatible with high-speed rotary printing of, for example, 200,000 copies / hour, it is lightweight and does not generate paper dust. A newsprint having excellent opacity, particularly printing opacity, and a method for producing the same are provided.

(Embodiment)
The newsprint of the present invention has a hydrated silicic acid internally added as a filler and a basis weight of 36-50 g / m ² .

In recent years, the weight reduction of newspapers has been promoted especially from the viewpoint of resource saving and transportation costs, and standard products with a basis weight of 43 g / m ² have become common as ultra-light newspapers. Some lightweight newspapers are also on the market. However, with the reduction in weight of such newsprint, optical suitability such as opacity and concealment is in the direction of decline.

  Conventionally, countermeasures such as adding an inorganic filler such as white carbon have been taken as a means to compensate for such opacity. However, the addition of an inorganic filler is caused by the generation of paper dust due to a decrease in the surface strength of the paper. Therefore, it is desirable to reduce the addition amount as much as possible. Furthermore, since the inorganic impurities accompanying the waste paper pulp tend to increase, it is difficult to further add inorganic filler on the papermaking side. However, in practice, the use of general white carbon which is bulky, has a large specific surface area, that is, has a small specific gravity, and has a high refractive index and oil absorption is still mainstream.

  From the above, in the newsprint of the present invention, instead of the conventional general white carbon as a filler, a specific hydrated silicic acid obtained without passing through a post-reaction drying step as described later is internally added. In addition, in the surface analysis of the paper surface up to 1 μm in thickness, the size of the silicon detection area analyzed for the hydrated silicic acid agglomerate particles has a particle diameter corresponding to the detection area of 20 μm or more. The area ratio of the aggregated particles is adjusted to be as low as 10% or less.

  On the other hand, in recent years, newspaper printing is rapidly progressing in color and speeding up, and accordingly, better color printing suitability and printing workability are required for newsprint as a printing medium. Newspaper paper is generally based on mechanical pulp and recycled paper (recycled) pulp, but such newsprint is required to contain a higher percentage of wastepaper pulp from the viewpoint of environmental protection. In addition, as a part of dealing with the increase in pages of newsprint, there is a demand for further weight reduction (low basis weight) of the paper.

However, if the basis weight is less than 36 g / m ² , it is difficult to obtain paper strength that is produced at a high speed of, for example, 1300 m / min or more and that corresponds to high-speed offset rotary printing at, for example, 200,000 copies / hour. For this reason, it is necessary to increase the paper strength enhancer. However, the increase in the paper strength enhancer causes a significant increase in dirt and manufacturing costs in the papermaking equipment system, which is not realistic. Conversely, newsprint with a basis weight exceeding 50 g / m ² goes against the trend of further weight reduction.

From the above, newsprint of the invention, the basis weight was measured according to "basis weight measurement method" described in JIS P 8124 is 36~50g / m ^2, preferably 38 g / m ² or more, More preferably, it is 39 g / m ² or more, preferably 48 g / m ² or less, and more preferably 46 g / m ² or less. When the basis weight is less than 36 g / m ² , the opacity and the paper quality strength are insufficient. For example, in high-speed rotary printing at 200,000 copies / hour, there is a problem that paper breakage easily occurs. On the other hand, when the basis weight exceeds 50 g / m ² , it becomes easy to secure sufficient opacity, but it is difficult to handle as lightweight newsprint.

  First, the raw material pulp used in the present invention will be described. The raw material pulp constituting the base paper of the newsprint of the present invention is not particularly limited. For example, waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, leaflet waste paper, office waste paper, upper white waste paper, Kent waste paper, imitation waste paper , Waste paper pulp made from ground paper waste, etc., waste paper pulp such as disaggregation / deinking waste paper pulp, disaggregation / deinking / bleached waste paper pulp; Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Machines such as Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermo Mechanical Pulp (TMP), Chemi Thermo Mechanical Pulp (CTMP), Refiner Mechanical Pulp (RMP) Pulp: Hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NB) P), chemical pulp such as hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), hardwood half bleached kraft pulp (LSBKP), softwood half bleached kraft pulp (NSBKP), hardwood sulfite pulp, coniferous sulfite pulp Various known pulps such as the above can be mentioned, and so long as they do not impair the object of the present invention, one or more of them can be appropriately selected, and the ratio can be appropriately adjusted and used.

  In order to obtain the base paper constituting the newsprint of the present invention, a filler is used together with the raw material pulp, and the base paper has hydrated silicic acid added internally as a filler.

  In the present invention, for example, a mineral acid is added to an alkali silicate aqueous solution to neutralize the alkali silicate aqueous solution, and the precipitated hydrated silicic acid is at least the same as the particles first dispersed in the alkali silicate aqueous solution. Hydrated silicic acid produced by adding a molar acid or more of a mineral acid and not undergoing a post-reaction drying step can be suitably used.

More specifically, for example, an alkali silicate aqueous solution (sodium silicate aqueous solution or silicic acid) in which SiO ₂ / R ′ ₂ O (molar ratio, R ′ represents Na or K) is in the range of 2.0 to 3.4. A mineral acid such as sulfuric acid is added to the aqueous potassium solution to neutralize the alkaline aqueous silicate solution. The mineral acid may be added at once or divided into a plurality of parts. When adding by dividing into a plurality of times, the first addition of the mineral acid is performed in the temperature range of the aqueous alkali silicate solution of 20 to 60 ° C., and the amount of mineral acid necessary for neutralizing the aqueous alkali silicate solution is increased. Add 10-50% by weight. Further, after raising the temperature of the alkali silicate aqueous solution to 85 ° C. or higher and lower than the boiling point of the aqueous solution, an aging time is provided as necessary, and then the second and subsequent mineral acids are added all at once or continuously. After the addition, an aging time may be provided as necessary.

  Mineral acid may be further added to the hydrated silicic acid produced by the method as described above. At this time, it is preferable to adjust the pH of the slurry containing the hydrated silicic acid to a range of 4-6. is there.

Hydrated silicic acid has a small primary particle of hydrated silicic acid at the stage of completion of the reaction in its production process, and the particle diameter is relatively uniform, but in the stable period after reaction, However, it does not exist and aggregates to form secondary particles. Further, when a drying process is performed at the stage of commercialization, secondary particles may form agglomerates and further coarse particles may be generated. The reason is not clear, but the hydrated silicic acid in the slurry state does not have some silica atoms and is liberated in the form of -SiOH, and the two-dimensional structure becomes a network tube and the surface is porous. ing. On the other hand, the dried hydrated silicic acid has a basic structure of SiO ₂ tetrahedron and shares a three-dimensional network structure with oxygen. Therefore, when the hydrated silicic acid is once dried, the bonding force with the cellulose fibers due to -SiOH on the surface is reduced. Therefore, the hydrated silicic acid that has finished the reaction remains in a slurry state and is subjected to a drying treatment. For example, high-speed papermaking such as a paper-making speed of 1300 m / min or more can be applied to the raw material pulp as a filler after performing wet grinding without application and subdividing the excessive secondary aggregates produced in the stable period. Newspaper paper based on the present invention which is possible and is lightweight, does not generate paper dust, and has excellent opacity, in particular, printing opacity, while being capable of high-speed rotary printing such as 200,000 copies / hour It is suitable for obtaining.

  The excessive agglomerate of hydrated silicic acid remaining after the wet pulverization is removed, or the volume average particle diameter of hydrated silicic acid is 3 to 10 μm and the particle diameter is 1 to 30 μm by laser analysis. In order to easily adjust the ratio of the hydrated silicate particles to 80% by mass or more, it is preferable to perform a classification treatment after the wet pulverization.

  If the volume average particle size of hydrated silicic acid by laser analysis is less than 3 μm, the loss of dehydration in the papermaking process will increase, it will remain in the white water, and it will combine with other foreign substances, resulting in equipment fouling and damage. There is a risk of causing it. On the other hand, when the volume average particle diameter exceeds 10 μm, it appears to be scattered as aggregates on the newspaper paper surface, resulting in reduced strength of the newspaper paper, generation of paper dust, opacity, especially printing opacity. There is a fear. Accordingly, the hydrated silicic acid used as a filler in the present invention has a volume average particle size of 3 μm or more, more preferably 4 μm or more, more preferably 10 μm or less, further 9 μm or less, as determined by laser analysis. For example, high-speed papermaking at a paper making speed of 1300 m / min or more is possible, and it is lightweight, free of paper dust, and not limited to opacity, especially printing, while supporting high-speed offset rotary printing at 200,000 copies / hour, for example. It is preferable for obtaining newsprint with excellent opacity.

  Furthermore, the ratio of the hydrated silicate particles having a particle size of 1 to 30 μm by laser analysis is preferably 80% by mass or more, more preferably 82% by mass or more, that is, by sharpening the particle size, The dispersibility of the hydrated silicic acid in the layer can be increased, and a homogeneous paper layer can be formed. Thereby, the intensity | strength of the newspaper paper surface can be improved, generation | occurrence | production of paper dust can be suppressed, and opacity, especially printing opacity can be improved simultaneously. Although it is preferable that the ratio of hydrated silicic acid particles having a particle size of 1 to 30 μm by laser analysis is as close to 100% by mass as possible, hydrated silicic acid, which is an aggregate of fine primary particles, is industrially used. In production, it is difficult to make the amount 100% by mass. From the viewpoint of production cost, the proportion of hydrated silicate particles having a particle diameter of 1 to 30 μm is at most about 95% by mass.

  In this specification, the laser analysis method refers to a particle size distribution measuring device (laser method) for a dispersion solution in which 10 mg of a sample is added to 8 ml of a methanol solution and dispersed for 3 minutes by an ultrasonic disperser (output: 80 W). The analysis method using a Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd.).

  The hydrated silicic acid not subjected to the drying step after the reaction used in the present invention is described in “Pigment test method—Part 13: Oil absorption amount—Section 1: Refined sesame oil” The amount of oil absorption based on the “method” is preferably 150 ml / 100 g or more, more preferably 160 ml / 100 g or more, and preferably 250 ml / 100 g or less, more preferably 240 ml / 100 g or less. If the oil absorption amount of the hydrated silicic acid is less than 150 ml / 100 g, the opacity may decrease and bleeding in offset printing may increase. On the other hand, if it exceeds 250 ml / 100 g, the vehicle component in the printing ink will be reduced. For producing newsprint paper that penetrates inside the paper and supports high-speed rotary printing such as 200,000 copies / hour, is lightweight, does not generate paper dust, and has excellent opacity, especially printing opacity. There is a risk that it is difficult to obtain an excellent printing density.

In the present invention, for example, the hydrated silicic acid obtained through the post-reaction drying stage obtained as described above is diluted in advance to a concentration of 2 to 3 % by mass, and the diluted solution is internally added to the raw pulp. papermaking Te.

Hydrated silicic acid that does not go through the drying stage after reaction has the property of reducing the apparent viscosity at high shear rate (thixotropic property), and exerts shearing force on the secondary aggregates and aggregates of hydrated silicic acid. When given, the agglomeration breaks down and becomes smaller agglomerates one after another. For obtaining a small agglomerated particles by this shearing force, and in order not to cause problems due to secondary aggregates or agglomerates of hydrated silicic acid, hydrated silicic acid in advance, 3 wt% or less, better good Ku is diluted to a concentration of 2.8 wt% or less, in terms of dispersed, it internally added in the raw material pulp. In addition, the concentration of the hydrated silicate is 2 mass from the viewpoint of effectively imparting the dispersion capacity of the existing equipment and the shearing force to the secondary agglomerates, and making the particle size distribution of the hydrated silicate after the dispersion not broad. It is preferable to dilute in advance so as to be at least% in high speed papermaking, for example, at a papermaking speed of 1300 m / min or more.

Furthermore, in order to prevent re-agglomeration of such small agglomerated particles, dilutions of hydrated silicate that does not undergo reaction after drying stage added to the pulp in the screen front.

  In the present invention, in addition to the hydrated silicic acid not subjected to the specific post-reaction drying step, as a filler, for example, calcite calcium carbonate in which calcite calcium carbonate or aragonite calcium carbonate is aggregated or crystallized in a chestnut shape, etc. Ordinary paper fillers such as calcium carbonate, clay, talc, titanium dioxide, zeolite, barium sulfate, zinc oxide, aluminum oxide, magnesium oxide, silicic acid, colloidal silica, colloidal alumina, satin white and other inorganic and organic fillers However, when using waste paper pulp as a raw material pulp, for example, the calcium chloride calcium carbonate is easy to provide a gap between the fibers due to its unique shape, and also tends to stay between the fibers, Especially in the present invention, high speed papermaking at a papermaking speed of 1300 m / min or more. Preferred.

  In the process of obtaining calcium carbonate having a stable calcite type crystal structure such as a spindle type or a columnar shape, or a calcium carbonate having a metastable aragonite type crystal structure by reacting calcium hydroxide with a carbon dioxide-containing gas. When the carbon dioxide-containing gas supply method is adjusted, or when dehydration, drying, and heat treatment are performed, for example, an additive such as condensed phosphoric acid or a metal salt thereof is added to agglomerate the spindle or columnar crystal structure. Obtained by crystallization.

In the case of calcite-based calcium carbonate, calcite is produced more naturally than limestone because it is more stable than other crystal structures. In addition, artificially, for example, natural limestone is decomposed into calcium oxide and carbon dioxide at high temperatures (impurities are removed), and calcium oxide is put into water to form calcium hydroxide (soaking). The calcite calcium carbonate can be obtained by blowing carbon dioxide while controlling the conditions (temperature, concentration, degree of stirring) as in the following reaction formula.
Ca (OH) ₂ + CO ₂ → CaCO ₃ + H ₂ O

Aragonite-based calcium carbonate is almost the same as the method for producing calcite-based calcium carbonate, and aragonite-based calcium carbonate can be obtained by adjusting the reaction conditions during the production. For example, as shown in the following reaction formula, using slaked lime and water in a causticization reaction tank, stirring and mixing with a stirrer equipped with a stirring blade to prepare lime milk, the sodium carbonate addition rate, addition time, and temperature conditions are appropriately set It is obtained by adjusting to cause a causticizing reaction.
Na ₂ CO ₃ + CaO + H ₂ O → CaCO ₃ + 2NaOH

The chestnut calcium carbonate used in the present invention has an oil absorption of 100 to 180 ml / 100 g, a BET specific surface area of 5 to ²⁰ m ² / g, and a volume average particle diameter based on the method described in JIS K 5101-13-1. Is preferably 1.0 to 10.0 μm.

  If the amount of oil absorption of potato chestnut calcium carbonate is less than 100 ml / 100 g, the opacity may decrease and bleeding in offset printing may increase. On the other hand, if it exceeds 180 ml / 100 g, the vehicle component in the printing ink will be inside the paper. There is a risk that it may be difficult to obtain an excellent printing density. Therefore, the amount of oil absorption of Oguri calcium carbonate is preferably 100 ml / 100 g or more, more preferably 110 ml / 100 g or more, and preferably 180 ml / 100 g or less, more preferably 170 ml / 100 g or less.

Further, if the BET specific surface area of calcium chloride calcium carbonate is less than 5 m ² / g, voids in the aggregated structure are reduced, so that the ink absorbability may be lowered. On the other hand, if it exceeds 20 m ² / g, the filler dispersion There is a risk that the dilution viscosity of the ink becomes high, the operability is lowered, and the printing density is lowered. Therefore, it is preferable that the BET specific surface area of Oguri calcium carbonate is 5 m ² / g or more, more preferably 7 m ² / g or more, and 20 m ² / g or less, further 18 m ² / g or less. It is capable of high-speed papermaking at a speed of 1300 m / min or more, and is also lightweight, does not generate paper dust, and supports opacity, particularly printing failure, while supporting high-speed offset rotary printing such as 200,000 copies / hour. This is preferable in providing newsprint paper with excellent transparency.

  In the present specification, the BET specific surface area of Oguri calcium carbonate refers to a value measured with a high-speed specific surface area / pore distribution measuring device (model number: Asap 2420, manufactured by Shimadzu Corporation).

  Further, when the volume average particle size of the calcium chloride calcium carbonate is less than 1.0 μm, when added as a filler, it becomes easy to enter the gaps between the pulp fibers constituting the paper, and the paper structure possessed by the calcium chloride calcium carbonate. It is difficult to exert the effect of increasing the bulk of the paper, and as a result, the printability may be reduced. On the other hand, when the thickness exceeds 10.0 μm, the contact area with the pulp fiber is reduced. There is a possibility that powder may be generated and printability may be deteriorated. Therefore, the volume average particle diameter of the calcium chloride calcium carbonate is preferably 1.0 μm or more, more preferably 1.8 μm or more, more preferably 10.0 μm or less, and further preferably 9.6 μm or less.

  In addition, in this specification, the volume average particle diameter of Higurashi calcium carbonate means the value measured by the said laser analysis method.

  Furthermore, the aspect ratio (the ratio of the major axis to the minor axis (major axis / minor axis)) of the calcium chestnut calcium carbonate is 3.5 or less from the viewpoint of further improving the opacity and printability of newsprint. It is preferably 1.5 to 3.3 from the viewpoint of sufficiently suppressing deterioration in quality of newsprint.

  In the present invention, as described above, other fillers such as calcium chestnut calcium carbonate can be used in combination as described above, but the total amount (100% by mass) is a specific hydrated silicic acid as described above. Desirably, in order for the effect of using the hydrated silicic acid to be sufficiently expressed, 20% by mass or more, further 40% by mass or more of the total filler is hydrated silicic acid. For example, high-speed papermaking is possible at a speed of 1300 m / min or more, and it is lightweight, no paper dust is generated, and opacity, in particular, is compatible with high-speed rotary printing such as 200,000 copies / hour This is preferable in providing newsprint with excellent printing opacity.

  In actual paper production, due to the use of waste paper pulp and the circulation of machine white water, fillers derived from waste paper, for example, other than the filler added to the raw pulp, are inevitably incorporated into the paper. It is. The average particle size of the filler in the paper is smaller than the average particle size in the slurry before addition. The reason is that in the preparation process before papermaking, the papermaking process, and the drying process, it is influenced by stirring force and shrinkage due to drying. Therefore, in the present invention, as will be described later, the particle diameter and particle size distribution on the surface of the newsprint after completion of papermaking are controlled within a certain range.

  The amount of filler added to the raw material pulp should be 10 kg or more, more preferably 15 kg or more per ton of pulp, in order to fully develop the effect of improving the opacity, particularly printing opacity, due to the use of the filler. In order to prevent the generation of paper dust from newsprint, it is preferably 50 kg or less, more preferably 40 kg or less per ton of dry weight pulp.

To obtain a base paper constituting the newsprint of the present invention, the raw material pulp, was added filler containing dilutions prepared by diluting the specific hydration silicic acid concentration of 2-3 wt%, for example preferably In this method, the pH and other conditions are adjusted so that the pH is neutral to alkaline in the range of 6.0 to 10.0, and the paper is made with a normal paper machine such as a long net paper machine or a twin wire paper machine. Can be adopted.

  Further, when making the paper, for example, normal paper chemicals such as a sizing agent, a dry paper strength enhancer, a wet paper strength enhancer, a yield improver, a drainage improver, an antifoaming agent, a slime control agent, and a dye. Can be added as needed.

  Further, in the present invention, when obtaining the base paper, it is possible to add a coagulant in the pulp preparation stage and further add a flocculant in the first stage of the papermaking process following the pulp preparation stage. The agglomeration of fine inorganic particles is promoted, and further, the inorganic particles are adhered to the raw material pulp to improve the filler yield, and the drainage is improved and the wet end stability is obtained.

  In particular, when mechanical pulp or used paper pulp having a high ratio of the mechanical pulp is used as a raw material pulp, since the pulp surface exhibits a relatively high anionic property, a coagulant is added at the pulp preparation stage, and further, Adding a flocculant before the papermaking process following the preparation stage improves the yield of the filler by physically and chemically adhering the filler between the pulp fibers, and improves the wet end stability by improving the drainage. For example, it is preferable because high-speed papermaking such as a papermaking speed of 1300 m / min or more is possible.

  As a coagulant preferably added in the pulp preparation stage as described above, for example, polyacrylamide (PAM), polyvinylamine (PVAm), polydiallyldimethylammonium chloride (Polydadomac, PDADMAC), polyamine (PAm), polyethyleneimine ( Organic polymer coagulants such as PEI) and inorganic coagulants such as sulfuric acid band and polyaluminum chloride.

  The average molecular weight of the organic polymer coagulant is preferably 400,000 to 1.3 million, and more preferably 700,000 to 1,200,000. When the average molecular weight is less than 400,000, the cohesive force is weak and the filler is not sufficiently fixed on the wet paper. As a result, the intended effect may not be improved. Since the strength is too strong, the amount of newsprint is reduced, and the amount added must be reduced to maintain a good result, and there is a possibility that the intended effect cannot be improved.

  The addition amount of the organic polymer coagulant is preferably adjusted so that the cation requirement reduction rate and the cation requirement of the paper filtrate after the addition of the organic polymer coagulant are satisfied. Therefore, although the addition amount of the organic polymer coagulant depends on the addition amount of the inorganic coagulant described later, it is 1000 to 4500 ppm in solid content with respect to the raw material pulp, and more preferably 1200 to 4000 ppm. preferable. If the amount of the organic polymer-based coagulant added is less than 1000 ppm, the effect may be insufficient. On the other hand, if it exceeds 4500 ppm, the formation of the paper may decrease and the cost may increase.

  Moreover, it is preferable that the addition amount of an inorganic type coagulant is 0.1-5.0 mass% with respect to a pulp, and also 0.1-3.0 mass%.

  In the present invention, as described above, it is preferable to add a coagulant in the pulp preparation stage. For example, the pulp and filler, and if necessary, an internal sizing agent, a fixing agent, a yield improver, a cation Various paper-making aids such as an agent, a paper strength enhancer, and an antifoaming agent are mixed in a compounding chest to become a finished raw material. Therefore, it is preferable that a coagulant is added between the compounding chest and the machine chest, and in order to sufficiently mix the coagulant with the finished raw material, it is more preferable to add the coagulant to the compounding chest.

  Furthermore, in the present invention, it is preferable to add a coagulant in the stage before the paper making process following the pulp preparation stage after adding the coagulant in the pulp preparation stage.

  As the flocculant, a cationic flocculant is particularly suitable for raw material pulp and filler exhibiting anionic properties. As such a cationic flocculant, for example, the average molecular weight is 8 million to 12 million, more preferably 8.5 million to 11 million, and the proportion of the cationic monomer is 5 to 100 mol%, further 10 to 100 mol%. Cationic water-soluble polymers or copolymers can be used. Typical examples of such cationic flocculants include PAM. If the average molecular weight of the cationic flocculant is less than 8 million, the effect using the cationic flocculant may not be sufficiently exhibited. On the other hand, if the average molecular weight is larger than 12 million, the desired effect can be hardly improved. However, there is a risk of high costs.

  As described above, the addition of the flocculant is particularly preferably performed in the head stage before the paper making process, that is, in the head box before the paper making net. Thereby, the amount of filler missing in the papermaking net can be significantly reduced.

  Moreover, the addition amount of the flocculant is preferably 100 to 150 ppm, more preferably 120 to 140 ppm as a pure component with respect to the raw material pulp. If the addition amount of the flocculant is less than 100 ppm, the filler yield improvement effect may not be sufficiently obtained, while if it exceeds 150 ppm, the formation of the newsprint may be lowered.

  Furthermore, in the present invention, the base paper obtained as described above preferably contains at least one water-soluble polymer compound such as starch and polyvinyl alcohol (hereinafter referred to as PVA), particularly starch as a main component. For example, it is preferable that high-speed papermaking at a papermaking speed of 1300 m / min or more is possible.

In the present invention, for example, when mechanical pulp or used paper pulp having a high ratio of the mechanical pulp is used as a raw material pulp, the pulp fiber is rigid and fibril fibers by fine beating exist on the fiber surface. A water-soluble polymer compound is externally added (coated), for example, to a solid content of 0.2 to 2.0 g / m ² on a base paper having rigid pulp fibers and fine fibril fibers. By adding it internally, the paper surface is secured by the water-soluble polymer compound, and while maintaining the bulkiness of the inside of the paper, it is lightweight while supporting high-speed offset rotary printing such as 200,000 copies / hour, for example. Thus, it is possible to provide newsprint paper that is excellent in opacity and printability, in particular, printing opacity, without generation of paper dust.

  The type of starch is not particularly limited, but in the present invention, for example, esterified starch or oxidized starch can be suitably used, and esterified starch is particularly preferable.

  For example, although modified starch has the effect of improving tensile strength and surface strength while penetrating into paper, it exhibits neutrality or anionic property, so it has low fixability on the surface of an anionic pulp fiber and has a coating property. Is low. Therefore, in the present invention, it is preferable to use a cationic starch having high fixability to the surface of an anionic pulp fiber. Further, when esterified starch or oxidized starch is used, the fixability to pulp fibers is high, the coating property is excellent, and the quality of the newspaper paper surface is improved.

  When esterified starch is used, the ink density and ink setting properties are dramatically improved. Examples of the raw material starch for obtaining such esterified starch include various starch-containing materials in addition to untreated starch and treated starch. Representative examples of such raw material starch include, for example, untreated starch such as wheat starch, potato starch, corn starch, sweet potato starch, tapioca starch, sago starch, rice starch, waxy corn flour, and high amylose content corn starch; And starch-containing materials such as tapioca starch, corn flour, rice flour, etc., and processed starch obtained by subjecting it to oxidation, acid treatment and the like. Among these, tapioca starch is preferable in that the ester-modified product is superior to other cereal starches in terms of viscosity, coating properties, elasticity, and extensibility. Furthermore, the esterified starch having thixotropic properties exhibits fluidity when applied to the surface of the base paper, but does not easily penetrate into the base paper after coating, and exhibits high coating properties on the surface of the base paper. preferable.

  In the esterified starch, the degree of esterification is not particularly limited, but the average number of ester bonds introduced is preferably 1 to 3, more preferably 1 to 2, per glucose unit. Of the esterified starches, hydroxyesterified starch is preferred, and it can be easily and inexpensively obtained by subjecting the raw material starch to an oxidation treatment and reducing the carboxymethyl group to a hydroxyethyl group.

  In particular, a hydrophobic group-containing ester-modified tapioca starch in which a hydrophobic group is introduced into the terminal group of the ester-modified starch can be suitably used.

  The esterified starch that can be used more suitably has a carboxylic acid (—COOH) structure in the terminal group, and in a neutral region, ionization like —COO— secures a linkage by hydrogen bonding. The esterified starch that exhibits thixotropic behavior due to its resilience cannot be penetrated into the base paper after being applied to the base paper surface, while exhibiting fluidity in coating. It is preferable from the point of exhibiting high film properties. In addition, when used in combination with a binder resin such as PVA having a high coatability, which will be described later, the effect is further achieved.

  As the esterified starch as described above, 1-octenyl succinic acid esterified starch obtained by ester-modifying tapioca starch as a main raw material is particularly preferable. 1-Octenyl succinate esterified starch is particularly excellent in terms of viscosity, film elasticity, and coatability, and in combination with PVA, it provides even more remarkable coatability and high-speed offset rotary printing such as 200,000 copies / hour. In addition, the ink density and the ink setting property can be improved.

  As the oxidized starch, conventionally used modified starch is preferably exemplified. For example, by oxidation reaction with sodium hypochlorite or the like, the molecular weight is reduced, and carboxyl groups, aldehyde groups, carbonyl groups, etc. The one that has been introduced.

  The starch used in the present invention has an average molecular weight of 600,000 to 3,000,000, more preferably 800,000 to 2.8 million, and the solvent component is used as a paper while keeping the paper surface coverage and the ink component on the paper surface. It is preferable from the point of taking in and improving absorption drying property.

Further, as the starch, those having a viscosity (10%) of 30 × 10 ⁻³ Pa · s or less, and further having a viscosity of 15 × 10 ^{−3 to} 25 × 10 ⁻³ Pa · s are fibers or fibrils protruding from the paper surface. In the flattening of the fibers, it is preferable from the viewpoint that it can remain on the paper surface without penetrating into the paper because of its high viscosity.

  As described above, examples of the water-soluble polymer compound include PVA in addition to starch. In general, when PVA is applied alone to the surface of a newsprint, it exhibits approximately three times the surface strength compared to the case where starch is applied alone, and is excellent in coating properties, but has high coating properties. In addition, when a printing ink that is dried by the penetration of a solvent into the paper, such as a cold set ink, is used, there is a possibility that the ink absorbability of the printing ink is low and sufficient ink setting properties cannot be obtained. In addition, when trying to apply a certain amount of PVA alone, the viscosity of the coating solution containing the PVA is high. For example, in the film transfer method, paper breakage, papermaking equipment stains, wrinkles, and paper surface stains may occur. . However, when such PVA is used in combination with starch, the coating property for retaining the ink filler component on the paper surface is improved while appropriately promoting the penetration of the solvent of the printing ink into the paper. For example, 200,000 parts In high-speed offset rotary printing such as / hour, there is an advantage that deterioration in ink setting is sufficiently suppressed.

  There is no particular limitation on the type of PVA, and the PVA that can be used in the present invention has a PVA having a terminal cation modified or an anionic group in addition to a normal PVA obtained by hydrolyzing polyvinyl acetate. Modified PVA such as anion-modified PVA is also included.

  As normal PVA obtained by hydrolyzing polyvinyl acetate, those having an average degree of polymerization of 300 to 3000, more preferably 1000 to 2400, and particularly 1700 to 2000 are excellent in compatibility with starch and have a uniform film. It is preferable from the viewpoint of being easily obtained.

  Moreover, as normal PVA, a thing with a saponification degree of 80-100 is preferable, and the complete saponification PVA with a saponification degree of 90-100 is more preferable. When completely saponified PVA is used, a film having water resistance and heat resistance is more easily obtained on the newspaper paper surface than when partially saponified PVA is used.

  When PVA is used as described above, since it has a good affinity with starch and can be blended with starch and PVA in a short time, the operability is improved and the occurrence of mist in the coating equipment can also be reduced. it can. Also, by using PVA with a high degree of saponification and a high degree of polymerization, it is possible to achieve high ink setting properties of offset ink while obtaining a high ink concentration. There is an advantage that ink transfer can be sufficiently prevented.

  When starch and PVA are used in combination, the solid mass ratio (starch: PVA) of both is 10: 0.8 to 10: 2.0, and further 10: 0.9 to 10: 1.2 Is preferred. If the ratio of PVA to starch exceeds 10: 2.0, for example, the viscosity of the coating liquid containing both increases rapidly, resulting in coating unevenness and mist, resulting in poor coating quality and around the equipment. There is a risk of fouling. On the other hand, if the ratio of PVA to starch is less than 10: 0.8, there is no problem in the compatibility of starch and PVA, but when applied to the surface of the base paper, there is a synergistic effect between starch and PVA. It may not be obtained, and penetration into the base paper or coating unevenness may occur. Therefore, by setting the solid content mass ratio of both in this range, a synergistic effect between starch and PVA, and further a synergistic effect with the filler constituting the base paper can be ensured. A high ink density can be expressed by being kept on the surface of the newsprint, and at the same time, the solvent in the ink can be quickly absorbed into the newsprint and a fast ink setting property can be expressed.

  For example, when a water-soluble polymer compound such as starch or PVA is applied to a base paper, if necessary, for example, an antifoaming agent, a water resistant agent, a surface paper strength agent, a surface sizing agent, a preservative, etc. Various auxiliary agents and the water-soluble polymer compound are appropriately mixed and water is added, and the solid content concentration is appropriately adjusted to, for example, about 2 to 15% by mass according to the coating apparatus and the target coating amount. A working solution may be used.

Coating liquids containing water-soluble polymer compounds such as starch and PVA are based on known coating methods such as film transfer methods such as gate rolls, two-roll size presses, and rod metering size presses. However, it is preferable to apply the film by the film transfer method. Coating by the film transfer method, particularly coating by a gate roll, unlike other coating methods, covers the surface of the base paper at a low coating amount of, for example, 0.2 to 2.0 g / m ² . The coating solution is optimal when applying a high contour coating, and since the coating solution is not subjected to a rapid shearing force, the coating solution used in circulation is excellent in stability, and a uniform coating can be obtained at high speed.

Water-soluble polymer compounds such as starch and PVA are coated and unevenly distributed on the surface of the base paper, and the solid content including those internally added in the base paper is 0.2 g / m ² or more, further 0 is preferably contained in the base paper in .5g / m ² or more quantities, also 2.0 g / m ² or less, more preferably it included in the base paper in an amount of 1.8 g / m ² or less. If the content of the water-soluble polymer compound is less than 0.2 g / m ² , the coating property by the water-soluble polymer compound is insufficient, the coating property on the surface of the base paper is not improved, and the ink pigment component is the newspaper. It may be difficult to stay on the surface of the paper and a high ink density may not be obtained. On the other hand, when the content of the water-soluble polymer compound exceeds 2.0 g / m ² , a large amount of starch solution mist is generated around the coating equipment, and the peripheral equipment is soiled. There is a risk of defects in the paper.

In the present invention, as described above, starch and PVA are used as the water-soluble polymer compound, and the solid content mass ratio (starch: PVA) of these starch and PVA is 10: 0.8 to 10: 2.0, And it is optimal that the total content of starch and PVA is 0.2 to 2.0 g / m ² in terms of solid content. As a result, for example, the pigment component of cold set type offset ink can be sufficiently retained on the surface of the newsprint, and the solvent (vehicle) permeability in the Z-axis direction of the newsprint can be further improved. By developing the concentration and obtaining a suitable solvent permeability, the ink setting property of the cold set type offset ink is further improved.

  The newspaper paper of the present invention thus obtained is a paper surface under the condition that an X-ray acceleration voltage is 8 kV and a diffusion region is 1 μm using an X-ray microanalyzer (model number: E-MAX, manufactured by Hitachi, Ltd.). In the surface analysis, the area ratio in the predetermined region of the aggregate particles having a particle diameter of 20 μm or more corresponding to the detection region is 10% or less in the size of the detection region of the hydrated silicic acid aggregate particles and the silicon to be analyzed. This is one of the major features.

Conventionally, map analysis of existing inorganic substances has been performed from elemental analysis of the paper surface using an X-ray microanalyzer, but each element is comprehensively detected in general elemental analysis using an X-ray microanalyzer. Therefore, the X-ray acceleration voltage is set to 15 kV or higher, and more preferably 20 kV or higher. However, with such a high acceleration voltage, the diffusion region by the following formula exceeds 1 μm, and even the presence of inorganic particles in the thickness direction of the paper is detected, so that only the paper surface can be accurately analyzed. Can not.
ρR = 0.0276E ₀ ^1.67 A / Z ^8/9
(Where R is the X-ray diffusion region, ρ is the average density, E ₀ is the acceleration voltage, A is the average molecular weight of the analysis site, and Z is the average atomic number.)

  Accordingly, in the present invention, in view of the relationship between the X-ray acceleration voltage and the diffusion region, the surface analysis of the paper surface using the X-ray microanalyzer under the conditions that the X-ray acceleration voltage is 8 kV and the diffusion region is 1 μm. Thus, in the size of the detection area of the silicon to be analyzed with the hydrated silicic acid aggregate particles, the area ratio in the predetermined area of the aggregate particles having a particle diameter corresponding to the detection area of 20 μm or more is 10% or less. By adjusting to, the target newspaper is realized.

  When the area ratio of the aggregated particles of 20 μm or more in a predetermined region exceeds 10%, when making paper at a high speed of, for example, 1300 m / min or higher, the resulting newspaper is used at a high speed of, for example, 200,000 copies / hour. When subjected to offset rotary printing, there is a problem that the papermaking equipment is worn and paper dust is generated, and in particular, the printing opacity is lowered. Therefore, the area ratio is 10% or less, preferably 9% or less.

  Although it is desirable that the area ratio of the aggregated particles of 20 μm or more in a predetermined region is as small as possible, in actual operation, hydrated silicic acid easily secondary agglomerates, so at least about several percent of aggregates of 20 μm or more. Presence of aggregate particles is observed.

  Ash content in newsprint is 4% by mass or more, more preferably 5% by mass or more, especially when measured according to “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method” described in JIS P 8251. It is preferably 7% by mass or more, 15% by mass or less, more preferably 13% by mass or less, and particularly preferably 10% by mass or less. If the ash content in the newspaper is less than 4% by mass, sufficient opacity is difficult to be obtained, and there is a risk that it will cause the show-through. Especially in the case of high whiteness, the show-through tends to be noticeable if the ash content is too small. . On the other hand, when the ash content exceeds 15% by mass, as described above, the paper quality strength is liable to decrease, a paper breakage trouble occurs in the paper making process, and the productivity may be lowered and the system may be contaminated. There is a tendency for paper breakage in high-speed offset rotary printing to occur, and print operability may be reduced.

  The ash content in the newsprint is preferably adjusted as appropriate according to the desired optical properties of the newsprint, the required surface strength, and the like. The amount of filler containing is appropriately adjusted and added internally. When the addition rate of the filler containing the hydrated silicic acid is too small, the effect of using the filler is not sufficiently expressed, and conversely, when too large, the paper strength may be reduced. The filler is preferably contained in the paper as a paper ash content of 4 to 15% by mass, and more preferably 5 to 10% by mass.

  Further, the newsprint of the present invention preferably has a formation index of 10% or less, more preferably 5 to 10%, particularly 6 to 9.5% by a sheet formation tester. The newsprint of the present invention requires a predetermined tensile strength because it is mainly printed on a rotary press. Therefore, in order to obtain a predetermined tensile strength in the longitudinal direction, it is preferable from experience that a formation unevenness having a formation index of about 5% occurs. On the other hand, when the formation index exceeds 10%, it is difficult to obtain a sufficient longitudinal tensile strength, and for example, in offset printing, particularly in color printing, uneven absorption of ink along the formation unevenness occurs, and printability, in particular, There is a risk of reducing the printing opacity.

  In addition, in this specification, the formation index of newsprint means a value measured by a sheet formation tester (manufactured by Toyo Seiki Seisakusho). The formation index is a value obtained by using a sheet formation tester which is a light transmission type ground total. The measuring principle of this measuring instrument is that the light transmitted through the base paper is decomposed into each pixel with a CCD camera, and the standard deviation, which is the variation in absorbance of each pixel, is divided by the average absorbance. "". That is, the larger the formation index, the worse the formation.

  In particular, in the present invention, newsprint with the ash content of 4 to 15% by mass and the formation index of 10% or less can be subjected to high speed papermaking such as a paper making speed of 1300 m / min or more, and for example 200,000 It is preferable from the standpoint of providing newsprint paper that is light in weight, does not generate paper dust, and has excellent opacity, in particular, printing opacity, while supporting high-speed offset rotary printing such as parts / hour.

  In the present invention, for example, high-speed papermaking of, for example, a papermaking speed of 1300 m / min or more is possible, and while being compatible with high-speed offset rotary printing of, for example, 200,000 copies / hour, it is lightweight and does not generate paper dust. The objective is to provide newsprint paper with excellent opacity, especially printing opacity, but of course the Macbeth densitometer after printing newsprint paper, not to mention satisfying the basic quality required for original newsprint paper. The ink density of the printed part measured at 1 is preferably 1.25 or more, more preferably 1.27 or more, and is preferably 1.36 or less, more preferably 1.34 or less. If the ink density is less than 1.25, it may be difficult to obtain a desired ink density, for example, in printing on an actual rotary press in a newspaper company. Conversely, if it exceeds 1.36, the ink density is sufficient. This can result in reduced print opacity and set-off problems.

  The ink concentration can be adjusted, for example, by appropriately adjusting the degree of saponification or polymerization of the water-soluble polymer compound such as starch or PVA and the amount of use thereof.

  In addition, in this specification, the ink density | concentration of the printing site | part after printing means the value calculated | required in the following ink density | concentration tests.

(Ink density test)
Using an RI printing aptitude tester (model number: RI-2 type, manufactured by Ishikawajima Industrial Machinery Co., Ltd.), offset printing ink (trade name: Newsz Naturalis (black), large, between the metal roll and rubber roll. After applying Nippon Ink Chemical Co., Ltd., ink usage: 0.85 ml), printing was performed at a speed of 30 rpm (test piece: CD direction 50 mm, MD direction 100 mm), and a constant chamber state (described in JIS P 8111) (Paper, paperboard and pulp-standard conditions for humidity conditioning and testing)) for 24 hours. About this print sample, the ink density of 25 printing parts selected at random is measured with a Macbeth densitometer, and these average values are calculated.

  The paper surface pH of the newsprint is preferably 6.0 or more, more preferably 6.5 or more, and is preferably 10.0 or less, more preferably 9.5 or less. For example, in correspondence to high-speed offset rotary printing such as 200,000 copies / hour, since the dampening water applied to the paper surface before printing varies depending on the newspaper company, it is almost neutral, so compatibility with dampening water In view of the above, it is preferable to adjust to such a paper surface pH range in order to reduce the risk of printing failure.

  In the present specification, the pH of the paper surface is visually determined with a discoloration standard meter using a reagent (MPC-BCP, pH 4.8 to 6.8) with a pH measurement kit for paper surface (manufactured by Kyoritsu Riken). This is the value measured.

  Further, the whiteness of the newsprint is 55% or more, more preferably 55.5 to 58, as measured according to “Pulp—Diffusion Blue Light Reflectance (ISO Whiteness) Measurement Method” described in JIS P 8212. % Is preferred. When the whiteness is less than 55%, not only the white paper appearance before printing is degraded, but also the appearance of the printed matter after offset printing, particularly after color printing, may be degraded.

  The blank paper opacity of the newsprint is 88% or more, and further 90 to 94%, as measured in accordance with “Paper and paperboard—Opacity test method (paper backing)” described in JIS P 8149. It is preferable. If the blank paper opacity is less than 88%, not only the appearance of the blank paper before printing is deteriorated but also the appearance of the printed matter after the offset printing may be lowered.

  The printing opacity after printing on the newsprint of the present invention is preferably 0.5% or more, more preferably 0.8 to 2.0% higher than the blank paper opacity.

Further, the newsprint of the present invention has a density of about 0.63 to 0.90 g / cm ³ measured in accordance with “Test method of thickness and density” described in JIS P 8118. The Beck smoothness measured in accordance with the described “paper and paperboard—smoothness test method using a Beck smoothness tester” is about 41 to 65 seconds. It is preferable in that it can be further improved.

Next, the newspaper and the manufacturing method thereof according to the present invention will be described in more detail based on the following examples. However, the present invention is not limited to these examples.

Preparation Examples 1-13 and Comparative Preparation Examples 1-4 (Preparation of hydrated silicic acid)
2500 L of sodium silicate aqueous solution adjusted to a concentration of 195 g / L in terms of silicon dioxide (silica), 4800 L of fresh water and 130 kg of anhydrous sodium sulfate were charged into a reaction tank having a volume of 10 m ³ .

  After the temperature of the solution in the reaction vessel was 50 ° C., 410 L of sulfuric acid (concentration: 20% by mass) corresponding to 32.5% by mass of the total amount of sulfuric acid necessary for neutralizing sodium silicate was stirred. Added continuously over 12 minutes. After the addition of sulfuric acid, the reaction solution was heated to 90 ° C. over 35 minutes with stirring, and then aged for 10 hours at 90 ° C.

  Next, the remaining 850 L of sulfuric acid (concentration: 20% by mass) was continuously added over 25 minutes. Further, aging was performed for 20 minutes while maintaining the temperature. Thereafter, sulfuric acid was continuously added to adjust the pH of the slurry to 5.2. The slurry with adjusted pH was filtered and washed, and then wet pulverization and classification were sequentially performed to obtain hydrated silicic acid (secondary aggregate).

  The obtained hydrated silicic acid composed of secondary aggregates was analyzed by the laser analysis method, and the volume average particle diameter and the ratio of hydrated silicate particles having a particle diameter of 1 to 30 μm (in Table 1, the particle ratio and Measured). The results are shown in Table 1.

  Moreover, the oil absorption of the obtained hydrated silicic acid was measured based on JIS K5101-13-1. The results are shown in Table 1.

  Furthermore, the obtained hydrated silicic acid was diluted with fresh water to prepare diluted water having the concentrations shown in Table 1.

Examples 1 to 13 and Comparative Examples 1 to 4 (Manufacture of newsprint)
Deinked waste paper pulp (disaggregation / deinked waste paper pulp) and mechanical pulp (TMP) are blended in the proportions shown in Table 2, and the fillers (variety A and variety B) shown in Table 3 are mixed in Table 3 per ton of pulp. And a coagulant (variety a and variety b) shown in Table 4 was added to obtain a pulp slurry.

  Next, the flocculant shown in Table 5 was added to the obtained pulp slurry, and paper was produced at a paper making speed of 1300 m / min with a long net paper machine to produce a paper. The water-soluble polymer compound shown in Table 6 was applied on the front and back surfaces of this paper by the coating method shown in Table 6 so that the coating amount on one side (total amount of water-soluble polymer compound) shown in Table 6 was obtained. Got a newspaper.

  The ratio of the filler shown in Table 3 (variety A: variety B (mass ratio)) is 500% in the image by electron beam probe microanalysis using ash obtained in accordance with JIS P 8251 as a sample. About 10 places selected for the purpose, the ratio of silica and calcium in terms of oxide was measured, and the measurement results at these 10 places were averaged. The measurement was performed using an X-ray microanalyzer (model number: E-MAX, manufactured by Hitachi, Ltd.) and an electron microscope (manufactured by Shimadzu Corporation) under the condition of an acceleration voltage of 8 kV.

Moreover, the filler shown in Table 3, the coagulant shown in Table 4, the flocculant shown in Table 5, and the water-soluble polymer compound shown in Table 6 are as follows.
(Filler)
Chestnut: Chestnut calcium carbonate Heavy: Heavy calcium carbonate Spindle type: Spindle type calcium carbonate (coagulant)
PEI: Polyethyleneimine PVAm: Polyvinylamine PDADMAC: Polydiallyldimethylammonium chloride PAm: Polyamine (flocculating agent)
PAM: Polyacrylamide (water-soluble polymer compound)
Esterified starch: 1-octenyl succinate esterified starch

  Each physical property of the obtained newspaper was measured by the following method. These results are shown in Table 7.

Further, commercially available newsprints A to C were used as Comparative Examples 5 to 7, and each physical property was measured in the same manner. These results are also shown in Table 7. In addition, the kind of filler currently mix | blended with these commercially available newsprints AC is as showing below.
Type of filler Newspaper A: White Carbon Newspaper B: Spindle-type Calcium Carbonate Newspaper C: White Carbon

(A) Basis weight It measured based on JISP8124.

(B) Paper surface pH
Using a pH measurement kit for paper (manufactured by Kyoritsu Riken), a reagent (MPC-BCP, pH 4.8 to 6.8) was used, and it was visually measured with a discoloration standard meter.

(C) Ash content It measured based on JISP8251.

(D) Formation index Measured with a sheet formation tester (manufactured by Toyo Seiki Seisakusho).

(E) Whiteness Measured according to JIS P 8212.

(F) Blank paper opacity Measured according to JIS P 8149.

(G) Printing Opacity Offset rotary printing press (model: RI-2, manufactured by Ishikawajima Industrial Machinery Co., Ltd.), offset rotary printing ink (trade name: News Zet Naturalis (black), Dainippon Ink and Chemicals, Inc. The ratio of the back surface reflectance after printing with respect to the back surface reflectance before printing when the printing amount is 200,000 parts / hour and the printed surface reflectance is 9%.
(Back side reflectance after printing / Back side reflectance before printing) × 100 (%)
Asked. A spectral whiteness colorimeter (manufactured by Suga Test Instruments Co., Ltd.) was used for measuring the reflectance.

(H) Opacity difference The difference (absolute value) between blank paper opacity and printing opacity was determined.

(I) Ink Concentration Using an RI printing aptitude tester (model number: RI-2 type, manufactured by Ishikawajima Industrial Machinery Co., Ltd.), offset printing ink (trade name: News Zet Naturalis) in the gap between the metal roll and the rubber roll. (Black), Dainippon Ink & Chemicals, Inc., ink usage: 0.85 ml), and printing at a speed of 30 rpm (test piece: CD direction 50 mm, MD direction 100 mm) (According to JIS P 8111) for 24 hours. About this print sample, the ink density | concentration of 25 printing parts selected at random was measured with the Macbeth densitometer, and these average values were calculated | required. If the ink density is less than 1.25, there may be a problem that the desired ink density does not occur, for example, in web offset printing in a newspaper company. Conversely, if it exceeds 1.36, the ink density is sufficient. However, there may be a decrease in printing opacity and a problem of set-off.

(J) Area ratio of aggregate particles having a particle diameter of 20 μm or more Using an X-ray microanalyzer (model number: E-MAX, manufactured by Hitachi, Ltd.) and an electron microscope (manufactured by Shimadzu Corporation), The surface of the paper is analyzed under the conditions of an acceleration voltage of 8 kV and a diffusion region of 1 μm, and the particle size corresponding to the detection region is 20 μm in the size of the silicon detection region analyzed for the hydrated silicic acid aggregate particles. The area ratio in the predetermined area of the above aggregate particles (area ratio in the 1 cm ² analysis area combined with the elemental analysis mapping photograph of the paper surface taken at 500 times) was determined.

  Next, each characteristic was investigated about the newsprint of Examples 1-13 and Comparative Examples 1-7 based on the following test examples 1-5. The results are shown in Table 8.

Test Example 1 (Ink setting property)
Using an RI printing aptitude tester (model number: RI-2 type, manufactured by Ishikawajima Industrial Machinery Co., Ltd.), newspaper ink (trade name: Newsjet Naturalis (black), manufactured by Dainippon Ink & Chemicals, Inc.) After solid printing with, the coated paper was stacked on the printing surface and pressure-bonded at a constant pressure. The state of ink transfer to the coated paper was visually observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
(Double-circle): The stain | pollution | contamination does not arise at all on the coated paper surface.
○: Slight dirt is generated on a part of the coated paper surface, but there is no practical problem.
Δ: Stain is observed on the entire coated paper surface.
X: Stain on the entire coated paper surface is remarkable.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

Test example 2 (ink inking property)
Using an offset printing machine (model number: Komori SYSTEMC-20, manufactured by Komori Corporation), using newspaper ink (trade name: Newsz Naturalis (black), manufactured by Dainippon Ink & Chemicals, Inc.), 20 Continuous 10,000 copies were printed at a speed of 10,000 copies / hour. About the obtained printed matter, the clearness and the shading unevenness of an image were observed visually, and it evaluated based on the following evaluation criteria.
(Evaluation criteria)
(Double-circle): The image is clear, there is no unevenness in density, and the ink deposition property is excellent.
A: The image is clear, there is almost no unevenness in density, and the ink deposition property is good.
Δ: There are portions where the image is unclear and unevenness in density, and ink inking properties are not good.
X: Overall, the image is unclear, the density unevenness is remarkable, and the ink deposition property is inferior.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

Test example 3 (surface strength)
Ink tack 18 using a color change tester (model number: RI-1 type, manufactured by Ishikawajima Sangyo Co., Ltd.) in accordance with “lithographic ink—Part 1: test method” described in JIS K5701-1. The printing was performed under the conditions of the first printing. The newspaper paper surface was visually observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: The entire surface of the newsprint is not removed.
○: Slightly removed on a part of the newspaper surface, but there is no practical problem.
Δ: Taken over the entire newspaper surface.
X: Significant removal on the entire newspaper surface.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

Test Example 4 (Ink absorption unevenness)
Using an offset printing machine (model number: Komori SYSTEMC-20, manufactured by Komori Corporation), using newspaper ink (trade name: Newsz Naturalis (black), manufactured by Dainippon Ink & Chemicals, Inc.), 20 Printing was performed at a speed of 10,000 copies / hour. The obtained printed matter was visually observed for ink density unevenness and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: There is no unevenness in the ink density, and the image is uniform and clear.
◯: There is almost no ink density unevenness and the image is uniform.
(Triangle | delta): The ink density nonuniformity is recognized in part, and there exists a location where an image is unclear.
X: Overall, the ink density unevenness is remarkable and the image is unclear.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

Test Example 5 (printing operability)
(1) Cutter tip clogging Using an offset rotary printing press (model number: LITHOPIA BTO-N4, manufactured by Mitsubishi Heavy Industries, Ltd.), printing was performed at a speed of 200,000 copies / hour on 50 continuous rolls of newspaper. The presence or absence of clogging of the sword tip was examined and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: No sword clogging occurred.
○: A sword clog occurred only once with one winding.
Δ: Claw tip clogging occurred 2 to 3 times with one winding.
X: Sword tip clogging occurred 4 times or more with one winding.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

(2) Blanket paper dust piling Using an offset printer (model number: Komori SYSTEMC-20, manufactured by Komori Corporation), continuous 4-color printing of 5000 parts at a speed of 200,000 parts / hour was performed. The presence or absence of paper dust generation / deposition in the blanket non-image area was visually observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
(Double-circle): Generation | occurrence | production of paper dust is not recognized at all.
○: Slight generation of paper dust is observed, but no deposition on the blanket is observed.
(Triangle | delta): Generation | occurrence | production of paper dust is recognized and it has accumulated on the blanket.
X: Accumulation of paper dust on the blanket is remarkable.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

(3) Neppari (Blanket adhesive)
Two samples obtained by cutting newspaper paper into a size of about 4 cm in width and about 6 cm in length were prepared and immersed in water for 10 seconds, and then these two samples were quickly brought into close contact with each other. This was passed through a calendar at a linear pressure of 100 kg / cm, dried at room temperature for 24 hours, and then manually peeled off two samples (T peel peel test imitation sensory test). Based on the evaluation.
(Evaluation criteria)
(Double-circle): It did not peel and it did not adhere | attach at all.
○: Although partly adhered, it could be easily peeled off.
(Triangle | delta): There existed a part which has adhere | attached and was hard to peel.
X: Adhered as a whole, and fluffing of fibers from the adhesion surface was observed at the time of peeling.
Of the above evaluation criteria, the cases of ○ and ○ are judged to be actually usable.

Any newsprint Examples 1-13 are internally added to the pulp in the state of dilution of low concentrations of hydrated silicic acid without going through a specific reaction after drying stages went with 2-3 wt% In addition, in the surface analysis of the paper surface up to a thickness of 1 μm, the aggregate particle having a particle size of 20 μm or more corresponding to the detection region in the size of the silicon detection region analyzed as the hydrated silica aggregate particle Is adjusted to be as low as 10% or less.

  Therefore, as shown in Tables 7 and 8, the newsprint papers of Examples 1 to 13 are not only lightweight, but also have high whiteness and white paper opacity, and high printing opacity is maintained. You can see that In addition, all the newspapers of Examples 1 to 13 have a high ink density of 1.25 to 1.36, but also have good ink setability and ink fillability and excellent printability, as well as surface strength. In other words, the paper powder is not generated at all, and the printing operability is excellent. In particular, the paper has excellent characteristics suitable for high-speed offset rotary printing.

  On the other hand, the newspapers of Comparative Examples 1 to 4 are not composed of the specific hydrated silicic acid as a filler, the concentration of the diluent is high, and the aggregate particles having a particle diameter of 20 μm or more are used. The area ratio exceeds 10%. Therefore, it can be seen that the newspapers of Comparative Examples 1 to 4 have insufficient whiteness and blank paper opacity, and low printing opacity. Moreover, all the newspapers of Comparative Examples 1 to 4 are suitable for high-speed offset rotary printing such as inferior ink setting properties and ink inking properties, uneven ink coloring, low surface strength, and poor printing operability. It can be seen that it does not have the necessary characteristics.

  In addition, the newspapers of Comparative Examples 5 to 7 use conventional white carbon or calcium carbonate as a filler instead of the specific hydrated silicic acid, and have an area ratio of aggregate particles having a particle diameter of 20 μm or more. Since it exceeds 10%, the properties necessary for high-speed offset rotary printing such as inferior ink setability and ink fillability, uneven ink coloring, low surface strength, and poor printing operability It turns out that it does not have.

  The newsprint of the present invention can be suitably used for offset rotary printing such as high-speed offset rotary printing such as 200,000 copies / hour.

Claims (4)

A method for producing newsprint paper comprising a base paper in which hydrated silicic acid is internally added as a filler, and having a basis weight of 36 to 50 g / m ² in accordance with JIS P 8124,
The hydrated silicic acid is obtained without a drying step after the reaction,
The hydrated silicic acid is diluted in advance to a concentration of 2 to 3% by mass to prepare a diluted solution, and after adding the diluted solution to the raw pulp at the front stage of the screen, paper is made to produce a base paper,
Size of detection area of silicon analyzed by aggregated particles of hydrated silicate in surface analysis of paper surface using X-ray microanalyzer with X-ray acceleration voltage of 8 kV and diffusion region of 1 μm in the particle diameter corresponding to the detection zone is the area ratio in a predetermined region of 20μm or more aggregate particles are characterized that you adjusted to be 10% or less, the production method of the newsprint. By laser analysis method, the volume average particle diameter of 3~10μm of the hydrated silicic acid, and is the ratio particle diameter of the hydrated silicic acid particles of 1~30μm 80 mass% or more, according to claim 1 Newspaper production method . A coating solution containing starch and polyvinyl alcohol, the solid content mass ratio of these two components (starch: polyvinyl alcohol) is 10: 0.8 to 10: 2.0, and the total content of starch and polyvinyl alcohol is the solid content. 0.2 to 2.0 g / m ² The manufacturing method of the newsprint of Claim 1 or 2 which coats on the surface of a base paper so that it may become. It consists of a base paper with hydrated silicic acid added internally as a filler, and has a basis weight of 36-50 g / m in accordance with JIS P 8124 ² Newspaper,
The hydrated silicic acid is obtained without a drying step after the reaction,
The base paper is produced by adding a diluted solution prepared by diluting the hydrated silicic acid to a concentration of 2 to 3% by mass in advance to the raw pulp before the screen, and then making paper.
Size of detection area of silicon analyzed by aggregated particles of hydrated silicate in surface analysis of paper surface using X-ray microanalyzer with X-ray acceleration voltage of 8 kV and diffusion region of 1 μm In the above, the area ratio in the predetermined region of the aggregate particles having a particle diameter of 20 μm or more corresponding to the detection region is 10% or less
Newspaper paper characterized by that.