JP5258482B2 - Newspaper for offset printing - Google Patents

Description

The present invention relates to newsprint for offset printing. More particularly, the present invention relates to a newsprint for offset printing that is particularly suitable for high-speed color printing, although it is a lightweight newsprint with a basis weight of less than 46 g / m ² .

  In recent years, the printing system has rapidly changed from a relief printing system to an offset printing system in accordance with the reduction in weight, speed, and color of newspaper printing. When printing by such an offset printing method, newsprint paper is required to have printing characteristics that are not only lightweight but also can be applied to an offset rotary press in large quantities and at high speed.

  On the other hand, automation of the entire newspaper printing system has also been promoted, and automatic unpacking machines for processing wound outer paper and automatic tailoring machines for automatically pasting tape for pasters have been introduced, and labor saving has also progressed. Yes. If such system automation and labor saving progresses, troubles such as poor recovery of exterior paper in the automatic unpacking machine or paper jams in the automatic tailoring machine will occur, and the paper roll will be fed to the rotary press paper feeder. As a result, the printing process is delayed, which may cause a serious trouble that the newspaper is delayed.

Conventionally, newspapers have a waste paper pulp content as high as 80% by mass or more of the total pulp, a basis weight of about 43 to 46 g / m ² , a density of about 0.63 g / cm ³ or more, and an ash content of about 6% by mass or more. In the case of paper, there is a high occurrence frequency of paper jam troubles in an automatic tailor that is thought to be caused by a decrease in paper thickness and stiffness, and various countermeasures are being studied.

  In order to solve the paper jam problem, methods such as mixing mechanical pulp with waste paper pulp, increasing the basis weight, or adding a bulking agent have been tried. It is thought that the cause is not only the decrease in paper thickness and stiffness, but the cause of the trouble is not clear, so an effective countermeasure has not been found.

For example, in Patent Document 1, the basis weight is 35 to 52 g / m ² , and the average dynamic friction force with a metal plate measured according to the friction test measurement method specified in JIS P 8147 is 1.5 to 3.0 mN. There has been proposed a newsprint in which the surface roughness of the metal plate measured by a stylus type surface roughness measuring instrument stipulated in JIS B 0651 is 0.1 to 2.0 μm. However, in the case of such newsprint paper, it is possible to prevent clogging of the sword in a newspaper rotary press. However, adjustment of the surface roughness alone can prevent general problems such as paper jam in the entire newspaper printing system. This cannot be improved, and it is impossible to prevent the occurrence of a paper jam problem in the automatic tailor as described above.

  Further, it has been found that the surface electrical resistance of the paper is involved as a cause of the paper jam trouble in the automatic tailoring machine.

For example, in Patent Document 2, by adding 50% or more of deinked waste paper pulp and adding carboxymethylcellulose or an inorganic salt thereof, the surface electrical resistance in an environment of a temperature of 20 ° C. and a humidity of 65% is 10 ⁸ Ω. Electronic copying paper or foam paper having a range of not less than / sq and less than 10 ¹⁰ Ω / sq has been proposed. However, the electrophotographic paper disclosed in Patent Document 2 has problems such as paper jams due to the occurrence of paper dust in a copying machine, poor toner fixing, form printing plate stains, and image reproducibility during toner transfer. Although problems such as reduction and double feeding of paper due to generation of static electricity can be solved, the basis weight is 64 g / m ² or more, which is heavier than newsprint, and is naturally highly rigid and air permeable. However, as in the case of the newsprint according to the present invention, the trouble of paper jam in the automatic tailor must be solved, and it is difficult to simply apply the electrophotographic paper technology to the newsprint as it is.
JP 2004-036017 A Japanese Patent No. 3075734

  The present invention has been made in view of the above-described background art, and is capable of preventing the occurrence of a paper jam problem in an automatic tailoring machine while being compatible with the recent high-speed offset rotary printing, and is capable of preventing the occurrence of a paper jam trouble in an automatic tailoring machine. The purpose is to provide.

The present invention
A newspaper containing a filler, made by a neutral papermaking method, and having a surface treatment agent applied to the front and back surfaces of the base paper,
The base paper is mainly composed of waste paper pulp,
The surface treatment agent is at least (A) a surface sizing agent,
(B) A paper strength enhancer and (C) a conductive agent, and the ratio of (A) surface sizing agent, (B) paper strength enhancer, and (C) conductive agent in the surface treatment agent is a solid content. In terms of mass ratio, (A) :( B) :( C) = 5: 100: 3 to 20: 100: 17, and the total coating amount on both surfaces in terms of solid content of the surface treatment agent is 0.00. The present invention relates to newsprint for offset printing, which is 1 to 2.0 g / m ² .

  ADVANTAGE OF THE INVENTION According to this invention, the newsprint paper for offset printing which can prevent generation | occurrence | production of the paper jam trouble with an automatic tailoring machine can be provided, respond | corresponding to recent high-speed offset rotary printing.

(Embodiment)
The newsprint for offset printing according to the present invention is obtained by applying a surface treatment agent to the front and back surfaces of a base paper made by a neutral papermaking method. The base paper is mainly composed of waste paper pulp, and preferably 100% by mass. The surface treatment agent contains at least specific three components described in detail later.

  First, the pulp component used for this invention is demonstrated. The pulp component constituting the base paper of the newsprint for offset printing of the present invention is mainly composed of waste paper pulp, preferably 60% by mass or more, and more preferably 100% by mass of waste paper pulp. As the waste paper pulp, it is preferable to use at least deinked waste paper pulp regenerated from newspaper waste paper, for example.

  The use of deinked waste paper pulp is preferable from the viewpoint of environmental conservation, and in newsprint paper, in particular, the use of deinked waste paper pulp and high blending have been demanded from the viewpoint of effective use of resources. However, high blending of deinked waste paper pulp generally makes it difficult to ensure a predetermined paper thickness and surface strength. In other words, deinked waste paper pulp is pulp that has been once paper-made, calendered, and recycled from used paper collected after use in the market, so the pulp fibers are damaged, the fibers are short, and the cushioning properties are low. . For this reason, newsprint paper containing a large amount of deinked waste paper pulp has high density and low cushioning properties, and is likely to cause paper dust due to a decrease in surface strength.

  In particular, among the deinked wastepaper pulp, the use of deinked wastepaper pulp that has been deinked from newspaper wastepaper is similar to the constituent material of newsprint for offset printing in the present invention, and is the most efficient in terms of resource recycling. It is good, but there is deinked waste paper pulp that is repeatedly recycled in the waste paper, and it becomes brittle due to the deterioration of the pulp fiber due to repeated regeneration treatment, and the fiber on the paper surface is taken up by the offset printing blanket, The paper dust causes problems such as scraping of the printing surface.

  However, the newsprint for offset printing of the present invention, as will be described later, is coated with a surface treatment agent containing at least three specific components on the front and back surfaces, and preferably with a specific filler contained in the paper. In combination, the paper is mainly composed of waste paper pulp such as deinked waste paper pulp, and it is suitable for recent high-speed offset rotary printing even though the base paper is preferably composed of 100% by weight waste paper pulp. However, the newspaper for offset printing is capable of preventing the occurrence of a paper jam problem in an automatic tailoring machine.

  As the deinked waste paper pulp used in the present invention, waste paper pulp derived from newspaper waste paper is preferably used, but in addition, for example, tea waste paper, craft envelope waste paper, magazine waste paper, renewed waste paper, flyer waste paper, office waste paper, Examples of these include dewaxing / deinking waste paper pulp, delamination / deinking / bleaching deinked waste paper pulp, etc., manufactured from corrugated waste paper, Kamihaku waste paper, Kent waste paper, imitation waste paper, old paper waste paper, plasterboard waste paper, etc. 1 type or 2 types or more can be suitably selected and used.

  In order to obtain the base paper constituting the newsprint for offset printing according to the present invention, for example, a filler generally used for newsprint, for example, calcium carbonate and / or hydrated silicic acid not subjected to a drying treatment is blended together with the raw material pulp. can do.

  Examples of the filler used in the present invention include calcium carbonate such as calcite calcium carbonate and aragonite calcium carbonate aggregated or crystallized in a chestnut shape, heavy calcium carbonate, light calcium carbonate, etc., clay, talc, Examples include ordinary paper fillers such as inorganic fillers and organic fillers such as titanium dioxide, zeolite, barium sulfate, zinc oxide, aluminum oxide, hydrated silicic acid, colloidal silica, colloidal alumina, and satin white. Alternatively, two or more kinds can be appropriately selected and used.

For example, when calcium carbonate is used as a filler, the paper surface pH is 7 to 9 due to its buffer effect. When the paper surface pH is neutral or alkaline, each fiber is sufficiently stretched compared to the acidic case. Therefore, the area | region where a fiber mutually forms a hydrogen bond increases. Therefore, when the ash content is about the same as that of acid newsprint, the paper strength such as the tensile strength and tear strength of the newsprint is higher in the papermaking by the neutral papermaking method. As a result, for example, the basis weight is 43. Even newspapers as low as ˜46 g / m ² have the advantage that sufficient strength to withstand high-speed offset printing can be obtained. In the present invention, newsprint paper for offset printing by a neutral papermaking method is preferably used. be able to.

  Note that the calcium chloride calcium carbonate reacts with calcium hydroxide and a carbon dioxide-containing gas to obtain, for example, calcium carbonate having a spindle or columnar stable calcite crystal structure or calcium carbonate having a metastable aragonite crystal structure. In the process, when adjusting the supply method of carbon dioxide-containing gas, or when performing dehydration, drying, or heat treatment, for example, by adding an additive such as condensed phosphoric acid or a metal salt thereof, a spindle type or columnar crystal structure is formed. Obtained by agglomeration and 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 above-mentioned calcium carbonate of the chestnut has an oil absorption amount of 150 to 250 ml / 100 g in accordance with the method described in JIS K 5101-13-1 “Pigment Test Method—Part 13: Oil Absorption—Section 1: Refined Amarine Oil Method”. The BET specific surface area is preferably 50 to 150 m ² / g, and the volume average particle diameter (secondary particle diameter) is preferably 1.0 to 10.0 μm.

  If the amount of oil absorption of Hashikari calcium carbonate is less than 150 ml / 100 g, for example, there may be a decrease in white paper opacity and bleeding in cold-set offset printing, while if it exceeds 250 ml / 100 g, the vehicle in the printing ink The components may penetrate into the paper and make it difficult to obtain an excellent printing density. Therefore, the amount of oil absorption of Oguri calcium carbonate 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.

In addition, if the BET specific surface area of calcium chloride calcium carbonate is less than 25 m ² / g, the voids in the aggregated structure are reduced, so that the ink absorbability may be lowered. On the other hand, if it exceeds 150 m ² / g, the filler dispersion The dilution viscosity of the ink becomes high, so that the operability is lowered, for example, the drying property of the cold-set type offset ink taken in is lowered, and there is a possibility that rubbing stains and printing print-off occur. Therefore, the BET specific surface area of the chestnut calcium carbonate is preferably 25 m ² / g or more, more preferably 70 m ² / g or more, and 150 m ² / g or less, further 130 m ² / g or less. It is preferable in providing newsprint paper that is capable of high-speed papermaking at a papermaking speed of 1300 m / min or more and that is compatible with high-speed rotary printing of, for example, 170 to 200,000 copies / hour, and that does not generate paper dust. Can solve the paper jam problem in the automatic tailor machine due to the synergistic effect with the surface treatment agent.

  In addition, in this specification, the BET specific surface area of Oguri calcium carbonate means the value measured with the fully automatic BET specific surface area measuring device (model number: Frosorb 2300, Shimadzu Corporation make).

  Further, the calcium chloride calcium carbonate has a primary particle of, for example, 100 nm or less, and when its volume average particle diameter (secondary particle diameter) is less than 1.0 μm, when added as a filler, This makes it easier to enter the gaps between the pulp fibers that make up, making it difficult to exert the bulky effect of the paper chestnut calcium carbonate, resulting in a decrease in printability. The amount decreases and it becomes difficult to hold the ink. If the ink penetrates into the base paper or in the extreme case, the ink may penetrate into the back surface, resulting in a decrease in print density or print back-through. On the other hand, when the volume average particle size (secondary particle size) of the calcium chloride calcium carbonate exceeds 10.0 μm, the contact area with the pulp fiber decreases, and as a result, paper dust is generated at the paper making stage and the printing stage. In addition to the possibility of a decrease in printability, there is a risk of paper dust and printing failure due to the drop of calcium chloride. 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 the present specification, the volume average particle diameter of Hashiguri calcium carbonate is a value measured by a laser analysis method. The laser analysis method is a method in which 10 mg of a sample is added to 8 ml of a methanol solution and an ultrasonic disperser (output) : 80 W) is a method of analyzing a dispersion solution dispersed for 3 minutes with a particle size distribution analyzer (laser type microtrack particle size analyzer, manufactured by Nikkiso Co., Ltd.).

  Furthermore, the aspect ratio of the calcium chloride calcium carbonate (the ratio of the major axis to the minor axis (major axis / minor axis) of the particles) is 3.5 or less, and further 3 from the viewpoint of further improving the printability of newsprint for offset printing. .4 or less, and 1.5 or more, more preferably 2.0 or more, from the viewpoint of sufficiently suppressing the deterioration of the quality of newsprint for offset printing.

  In particular, when calcium carbonate such as calcium chestnut calcium carbonate is used as a filler, in order to efficiently disperse it in paper, the calcium carbonate is previously adjusted to a concentration of 7.5% by mass or less, and further 7.0% by mass or less. After dilution, it is preferably added internally to the pulp component, and from the viewpoint of yield to paper, the concentration of calcium carbonate is 5.5% by mass or more, more preferably 6.0% by mass or more. It is preferable to dilute in advance.

  If the diluted concentration of calcium carbonate exceeds 7.5% by mass, uniform dispersion in the pulp component becomes difficult, and conversely, if it is less than 5.5% by mass, the amount of filler dispersion in the pulp component increases. As a result, the operability deteriorates and the frequency of contact with the pulp component decreases, which causes a decrease in yield.

  In addition, depending on the concentration of the added pulp slurry, excessive physical dispersion force is added to the filler aggregate by the pulp fiber in the mixing with the pulp component, as in the case of the bead mill. It is preferable that the filler is added in an environment where the filler itself is easily dispersed. Therefore, in the present invention, the pulp slurry is preferably 0.5 to 5.0% by mass in line with the finished chest, the fan pump suction side before the seed box, most preferably the fan pump suction before the seed box. It is desirable to add a filler at a concentration of 1.5 to 3.0% by mass.

  Calcium calcium carbonate has a larger specific surface area than general spindle-type calcium carbonate, so the surface treatment agent coated on the front and back sides of the base paper is relatively large on the surface without impregnating the newspaper for offset printing. It makes it easier to adjust the dynamic friction force and surface electrical resistance by water-soluble resin, and more effectively suppress the decrease in stiffness and the increase in air permeability, and jams in an automatic tailoring machine (jamming) Troubles and reductions in the surface strength of newsprint can be improved more effectively.

  Here, by sufficiently suppressing the decrease in stiffness and the increase in air permeability, it is possible to prevent occurrence of a paper jam problem in an automatic tailoring machine, which is a problem of the present invention, and high-speed color printing. In the newsprint for offset printing particularly suitable for the above, the decrease in the rigidity and the increase in the air permeability are matters that lead to a paper feed failure on the tailoring plate of the automatic tailor.

  If the rigidity is low, the offset printing newsprint itself undulates when the paper is fed into the apparatus and tends to be jammed by the tailoring plate of the automatic tailor. Therefore, in consideration of a series of workability in offset rotary printing, adjusting the rigidity to a range of 25 to 45, and further 30 to 40 is preferable in terms of workability, particularly in terms of operability in newspaper readers. .

  On the other hand, when the air permeability is high, there is a problem that the static elimination property of static electricity is lowered, and the air permeability is an index of ink absorption drying property at the time of high-speed offset rotary printing, particularly at full color printing. If the air permeability exceeds 50 seconds, there is a risk of causing a paper flow in multi-page printing due to air entrapment between the newsprint paper for offset printing and the various rolls of the rotary press during the printing operation.

  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 has at least the same mol or more as the particles first dispersed in the alkali silicate aqueous solution. Hydrated silicic acid produced by adding a mineral acid and not undergoing a post-reaction drying step can be suitably used as a filler.

More specifically, for example, an alkali silicate aqueous solution (sodium silicate aqueous solution or potassium silicate aqueous solution) in which SiO ₂ / R ′ ₂ O (molar ratio, R ′ represents Na or K) is in the range of 2.0 to 3.4. Further, a mineral acid such as sulfuric acid is added to neutralize the alkali silicate aqueous 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 carried out in the temperature range of the alkali silicate aqueous solution in the range of 20 to 60 ° C., and the amount of mineral acid required to neutralize the alkali silicate aqueous solution is 10 to 10. 50% by weight is added. Further, after raising the temperature of the alkali silicate aqueous solution to a range of 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 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.

Hydrated silicic acid is present in the form of primary particles in the stable period after reaction, although the primary particles of hydrated silicic acid are small and the particle size is relatively uniform in the process where the reaction is completed in the production process. They are not agglomerated and form secondary particles. In addition, when a drying process is performed in the product production process, secondary particles may form aggregates, and 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. Yes. On the other hand, the dried hydrated silicic acid has a basic structure of SiO ₂ tetrahedron and shares a three-dimensional network structure sharing oxygen. Therefore, when the hydrated silicic acid is once dried, the bonding force with the cellulose fibers due to -SiOH on the surface decreases, so that the hydrated silicic acid that has finished the reaction remains in a slurry state and is not subjected to a drying treatment. It is possible to perform high-speed papermaking at a speed of 1300 m / min or more, for example, by adding wet pulverization to the secondary pulp as a filler after subdividing the excessive secondary aggregates produced in the stable period. In addition, it is suitable for obtaining newsprint paper for offset printing based on the present invention, which can solve a paper jam trouble in an automatic tailoring machine while corresponding to high-speed offset rotary printing such as 170 to 200,000 copies / hour, for example. It is.

  Water having a volume average particle diameter of hydrated silicic acid of, for example, 3 to 10 μm and a particle diameter of 1 to 30 μm by laser analysis is used to remove excessive agglomerates of hydrated silicic acid remaining after the wet pulverization. In order to easily adjust the ratio of the Japanese silicate particles to, for example, 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 3μm, 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 to cause damage and damage to the equipment. The effect of retaining the water-soluble resin in the present invention on the surface of the base paper cannot be expected. On the contrary, when the volume average particle diameter exceeds 10 μm, it is a hydrated silicic acid that has the appearance of being scattered as agglomerates on the newspaper paper surface and originally has the property of increasing the frictional resistance, which is the main subject of the present invention. In addition, there is a risk of causing paper jam troubles in an automatic tailoring machine, and there is a risk of reducing the strength of the newspaper surface, generating paper dust, and decreasing opacity, particularly printing opacity. Therefore, the hydrated silicic acid used as a filler in the present invention preferably has a volume average particle diameter of 3 μm or more, more preferably 4 μm or more, more preferably 10 μm or less, further 9 μm or less by laser analysis. Newsprint paper for offset printing capable of high-speed papermaking at a paper making speed of 1300 m / min or more, prevention of paper jam troubles in an automatic tailor machine, and high-speed offset rotary printing such as 170 to 200,000 copies / hour, for example It is preferable to obtain

  This not only eliminates paper jam troubles in the automatic tailoring machine, but also improves the strength of the newspaper surface, suppresses the generation of paper dust, and at the same time improves opacity, particularly printing opacity. 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 as possible to 100% by mass, hydrated silicic acid, which is an aggregate of fine primary particles, is produced industrially. In doing so, it is difficult to adjust to 100% by mass. From the viewpoint of production cost, the proportion of hydrated silicic acid particles having a particle diameter of 1 to 30 μm is at most about 95% by mass.

  In addition, the hydrated silicic acid not subjected to the post-reaction drying step used in the present invention is described in JIS K 5101-13-1, “Pigment Test Method—Part 13: Oil Absorption—Section 1: Refined Sesame Oil Method Is preferably 150 ml / 100 g or more, more preferably 160 ml / 100 g or more, more preferably 250 ml / 100 g or less, and even more preferably 240 ml / 100 g or less. If the oil absorption of the hydrated silicic acid is less than 150 ml / 100 g, there is a problem that a paper jam trouble is likely to occur in an automatic tailor due to the anti-slip property inherent in the hydrated silicic acid, and a decrease in opacity. In addition, there is a risk that bleeding in offset printing becomes large.

  In the present invention, the amount of filler added to the pulp component is sufficient to express the effect of improving printing operability and printability while maintaining appropriate opacity due to the use of the filler. P 8251 "Paper, paperboard and pulp-Ash content test method-525 ° C combustion method" The ash content in the paper measured according to the method described above is preferably 5% by mass or more, more preferably 7% by mass or more, and preferably It is preferable to add a filler in addition to the ash content from the waste paper so that the amount becomes 20 mass% or less, more preferably 15 mass% or less.

  If the ash content in the paper is less than 5% by mass, it is difficult to maintain sufficient opacity and printing opacity, resulting in a problem that the dryness of the offset ink is poor. On the contrary, if the ash content in the paper exceeds 20% by mass, the entanglement between the raw pulp fibers decreases, so the paper quality decreases and the proportion of the filler that does not adhere to the raw pulp fibers increases. Is expressed.

  In order to obtain the base paper constituting the newsprint for offset printing of the present invention, for example, the filler is appropriately added to the pulp component, preferably pH 6.0 to 10.0 so as to be neutral to alkaline. By adjusting these conditions, it is possible to suitably employ a neutral paper making method in which paper is made with a normal paper machine such as a long net paper machine or a twin-wire paper machine.

  Further, when making the paper, for example, normal paper making 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.

  Thus, the base paper constituting the newsprint for offset printing of the present invention can be obtained through the paper making process. In the present embodiment, preferably, the calcium carbonate and the hydrated silicic acid not subjected to the drying treatment are added to JIS P 8251. A base paper is made by adding to the pulp component as a filler so that the ash content in the paper measured in accordance with 5 to 20% by mass, and (A) surface sizing agent and (B) paper strength are formed on the front and back surfaces of the base paper. By applying a surface treating agent containing at least an enhancer and a conductive agent (C), it is possible to cope with recent high-speed offset rotary printing and to prevent the occurrence of paper jam troubles in an automatic tailoring machine. Newsprint paper for offset printing can be obtained.

As described above, conventionally, in newspapers with a high content of waste paper pulp, a basis weight of about 40 to 48 g / m ² , a density of about 0.63 g / cm ³ or more, and an ash content of about 6% by mass or more, The frequency of paper jam troubles in the automatic tailor is high, but the paper jam troubles in this automatic tailor were thought to be caused by a decrease in paper thickness and stiffness. However, in fact, it has become clear that not only such a decrease in paper thickness and stiffness, but also the surface electrical resistance of the paper is deeply involved in a paper jam problem in an automatic tailor.

  Therefore, in the present invention, (A) a surface sizing agent, (B) a paper strength enhancer, and (C) a surface treatment agent containing at least three specific components, ie, a conductive agent, is coated on the base paper, more preferably By including a predetermined filler in the base paper, the average dynamic friction force and the surface electrical resistance of the paper are adjusted as appropriate, thereby eliminating paper jam troubles in the automatic tailoring machine that frequently occurred in the past.

  Examples of the (A) surface sizing agent include alkyl ketene dimer, alkenyl succinic anhydride, polyethyleneimine, polydimethyl diallyl ammonium chloride, polyalkylene polyamine dicyandiamide ammonium condensate, polyvinyl pyridium halide, alkyl (meth) acrylate 4 Polymers such as quaternary ammonium salts, (meth) acrylamide alkyl quaternary ammonium salts, ω-chloro-poly (oxyethylene-polymethylene-alkyl quaternary ammonium salts), polyvinylbenzyltrimethylammonium salts, styrene polymers, acrylic polymers, and the like. In particular, the cationic surface sizing agent is preferable because it has better fixability with, for example, anionic calcium chestnut carbonate contained in the base paper and hydrated silicic acid that has not undergone drying treatment. Exemplified are, it can be used by selecting one or more from among these as appropriate.

  Examples of the paper strength enhancer (B) include so-called paper strength enhancers and wet strength enhancers such as oxidized starch, cation-modified starch, polyamide / epichlorohydrin resin, polyethyleneimine resin, polyacrylamide resin, and polyamide resin. Of these, one or more of them can be appropriately selected and used.

  In the present invention, when oxidized starch is used as the paper strength enhancer (B), the newspaper for offset printing is particularly suitable for high-speed color printing, which has a higher effect of preventing the occurrence of a paper jam problem in an automatic tailor. Paper can be provided.

  In particular, (B) oxidized starch suitably used as a paper strength enhancer includes, for example, wheat starch, potato starch, corn starch, sweet potato starch, tapioca starch, sago starch, rice starch, waxy corn flour, high amylose content corn starch and the like. Unprocessed starch: Processed starch that has been used historically, such as wheat starch, tapioca starch, corn flour, and starch containing ingredients such as rice flour that have been oxidized. The molecular weight is reduced and a carboxyl group, an aldehyde group, a carbonyl group or the like is introduced into the molecule by an oxidation reaction with sodium hypochlorite or the like.

  Oxidized starch has long been used as a processed starch for papermaking, and is a papermaking chemical that has a high paper strength improving effect despite its low cost. (A) Surface sizing agent and (C) Conductive agent described later Are compatible with each other and are most preferably used in the present invention.

  The weight average molecular weight of the oxidized starch is preferably in the range of 500,000 to 800,000, more preferably 600,000 to 700,000, particularly 600,000 to 650,000, which is an essential component of the surface treatment agent. From the viewpoints of compatibility with (A) surface sizing agent and (C) conductive agent, homogeneous mixing, and coatability on the base paper. When oxidized starch having a weight average molecular weight of less than 500,000 is used as a raw material for the surface treatment agent, it is difficult to obtain a sufficient surface strength improvement effect as a paper strength enhancer, even if starch paste is applied to the paper surface. Also, in combination with the (A) surface sizing agent and (C) conductive agent used in combination, the impregnation into the base paper is fast, preventing the occurrence of paper jam troubles in the automatic tailoring machine, especially for high-speed color printing It may be difficult to obtain a suitable newsprint for offset printing. On the other hand, when oxidized starch having a weight average molecular weight of more than 800,000 is used as a raw material, the viscosity of the surface treatment agent obtained becomes too high, and workability when coating the surface treatment agent on a base paper may be reduced. .

  Examples of the conductive agent (C) include hygroscopic inorganic salts such as sodium chloride and lithium chloride, acrylic acid derivatives such as polydiethylaminoethyl methacrylate and dimethyl sulfate quaternary compounds, polyalkylene polyamine derivatives such as polyamine, polyethylene glycol and terephthalate. Polyester with acid, quaternary ammonium salt type polyelectrolyte such as polyvinylbenzyltrimethyl chloride, alkali metal salt of polyelectrolyte having carboxyl group such as maleic anhydride, alkali metal of styrene-maleic anhydride copolymer Salt, conductive oligomer such as sulfonated styrene oligomer, alkyl sulfate ester, alkyl phosphate ester, fatty acid ethylene oxide adduct, fatty acid ethylene oxide adduct, alkylphenol ethylene oxide Side adduct, surfactants such as carboxylic acid derivatives, are exemplified polyhydric alcohols such as sorbitol or the like, can be used to select one or more from among these as appropriate.

  Preferably, offset printing newsprints are used for various purposes such as house cleaning, food packaging, and tatami mats, in addition to being used as an information transmission medium. Sodium) is preferred.

  The ratio of (A) surface sizing agent, (B) paper strength enhancer, and (C) conductive agent in the surface treatment agent corresponds to the recent high-speed offset rotary printing which is the main problem of the present invention, and is an automatic tailor In order to obtain newsprint paper for offset printing that can sufficiently prevent the occurrence of paper jam troubles, the surface sizing agent has improved slip resistance and the paper strength enhancer has improved surface strength, stiffness, and air permeability. There is a combination to obtain the desired properties without offsetting the effects on the static electricity and the antistatic property due to the conductive agent, and the solid content also from the viewpoint of uniform mixing, adjustment and workability during coating of the surface treatment agent By mass ratio, (A) :( B) :( C) = 5: 100: 3-20: 100: 17, further 8: 100: 6-18: 100: 15, especially 10: 100: 7-12 : 100: 13 It is preferable to integer.

  The method for obtaining the surface treating agent is not particularly limited, and the types of (A) surface sizing agent, (B) paper strength enhancing agent, and (C) conductive agent are selected, for example, (A) surface sizing agent and ( B) A treatment usually adjusted to a surface treatment agent for printing paper such as newsprint paper, if necessary, so that the ratio of the paper strength enhancer and (C) the conductive agent is appropriately adjusted within the above range. The target surface treatment agent can be obtained by sufficiently mixing and stirring, for example, at room temperature so as to obtain a uniform composition together with the agent.

  The coating apparatus for coating the front and back surfaces of the base paper with a surface treatment agent containing at least (A) a surface sizing agent, (B) a paper strength enhancer, and (C) a conductive agent is particularly limited. Although not, for example, size press coaters such as ink line or vertical two-roll size press, blade metalling size press, rod metalling size press, roll coater such as gate roll coater, trailing, flexible, roll application, fountain application Well-known and publicly used devices such as bevel type coaters such as short dwells, bent type blade coaters, rod blade coaters, bar coaters, air knife coaters, curtain coaters, spray coaters, and gravure coaters are appropriately used.

The coating of the surface treatment agent adjusts the average dynamic frictional force and surface electrical resistance of the paper as appropriate to fully develop the effect of eliminating paper jam troubles in the automatic tailor, and has sufficient strength, especially high surface strength. to maintain, the total 0.1 to 2.0 g / m ² of both surfaces of the coating amount in terms of solid content, preferably 0.05 per range (single-sided 0.5 to 1.0 g / m ² 1.0 g / m ^2, preferably it is desirable to conduct such a range) of 0.25~0.5g / m ^2. If the coating amount of the surface treatment agent is within the range, it is possible to prevent the occurrence of paper jam troubles in an automatic tailoring machine sufficiently easily, and an excellent newspaper for offset printing particularly suitable for high-speed color printing. Paper can be provided. Further, in consideration of the problem of the occurrence of drip due to wet water in high-speed offset printing, the surface treatment agent may be applied in an amount of 2.0 g / m ² or less per side of the base paper, and further 1.0 g / m ² or less. preferable.

  In addition, since the surface of the winding paper, that is, the surface of the newsprint is in contact with the tailoring plate of the automatic tailoring machine, the proportion of the conductive agent (C) on the front and back surfaces of the newsprint for offset printing is the mass. It is preferable to appropriately adjust the composition of the surface treatment agent and the coating amount so that the ratio of front to back is 1: 1 to 4: 1, and 1: 1 to 3: 1.

  By making the ratio of (C) conductive agent present on the front surface equal to or higher than that on the back surface, it becomes possible to suppress the generation of static electricity on the surface of the paper in contact with the tailoring plate, and (C) the amount of conductive agent used Reduction and chemical cost reduction.

  Further, in the present invention, a paper obtained by coating a base paper with a surface treatment agent may be passed through a calender device as necessary, and subjected to pressurization and smoothing to finish. As the calendar device, any of an off type and an on type can be used. For example, a commonly used calendar device such as a super calendar, a soft calendar, a gloss calendar, a compact calendar, a mat super calendar, a mat calendar is appropriately used. Can be used. As the calender finishing conditions, the temperature of the rigid roll, the calender pressure, the number of nips, the roll speed, the paper moisture before the calender, and the like may be appropriately selected according to the required quality. As the roll of the calender device, as the rigid roll, a metal roll, a roll whose surface is mirror-finished with hard chrome plating, a roll whose surface is roughened, etc. are used as appropriate. . As the elastic roll, a resin roll such as a urethane resin, an epoxy resin, a polyamide resin, a phenol resin, or a polyacrylate resin, a roll formed of cotton, nylon, asbestos, aramid fiber, or the like is appropriately used. It is of course possible to condition the newspaper after finishing with a calendar, or to humidify it using a water coating device, an electrostatic humidifier, a steam humidifier or the like.

  A newsprint in which a base paper is made by a neutral paper making method, and a surface treatment agent is coated on the front and back surfaces of the base paper, wherein the base paper is mainly composed of waste paper pulp, and the surface treatment agent is at least (A A surface sizing agent, (B) a paper strength enhancer, and (C) a conductive agent, and preferably (A) a surface sizing agent and (B) a paper strength enhancing agent in the surface treatment agent. (C) The ratio with the conductive agent is (A) :( B) :( C) = 5: 100: 3 to 20: 100: 17 in terms of solid content mass ratio, and (B) paper strength. The enhancer is oxidized starch, and it is preferable that the weight average molecular weight of the oxidized starch is 500,000 to 800,000, more preferably, the ash content in paper measured according to JIS P 8251 is 5 to 20% by mass. A newsprint for offset printing according to the present invention is JIS P 8147 “Paper and paperboard abrasion”. Average dynamic friction force between the newspaper surface for offset printing (paper flow direction) and the metal surface (surface of stainless steel plate having a surface roughness Ra of 0.4 or less) measured according to the method described in “Coefficient Test Method”. However, it is preferably 1.50 mN or more, more preferably 1.55 mN or more, and preferably 3.00 mN or less, more preferably 2.80 mN or less. If the average dynamic friction force is less than 1.50 mN, there is a risk of paper flow and wrinkling during printing on a rotary press. On the other hand, if the average dynamic friction force exceeds 3.00 mN, the tip of the sword is likely to be clogged.

  Since the surface of the web, that is, the surface of the newsprint, comes into contact with the tailor plate of the automatic tailoring machine, the average dynamic friction force of the newsprint for offset printing is 1.55 to 2. It is preferably 80 mN.

  The average dynamic frictional force has a great influence on paper jamming (jamming) due to physical frictional force in the occurrence of a paper jam trouble in an automatic tailoring machine, which is a main problem of the present invention.

  If the average dynamic friction force is less than 1.50 mN, there is a risk of static electricity generation due to slipping. Conversely, if the average dynamic friction force exceeds 3.00 mN, paper jamming due to physical friction (jamming), the reason is not clear. Static electricity due to friction is likely to be generated, and further, it may cause a paper jam (jamming) in a printing machine such as a high-speed offset rotary printing machine.

  The average dynamic frictional force of the newsprint for offset printing in the present invention is influenced by the surface treatment agent coated on the front and back surfaces of the base paper and tends to be relatively high by the influence of the filler contained in the base paper. Therefore, the coating of the surface treatment agent within the preferred range described above, and more preferably, calcium carbonate and / or hydrated silicic acid that does not undergo a drying treatment is used as a filler to be added during the production of the base paper. It is preferable.

Further, the newsprint for offset printing of the present invention is a standard having a temperature of 23 ± 1 ° C. and a relative humidity of 50 ± 2% in accordance with the description of JIS P 8111 “Paper, paperboard and pulp-standard conditions for humidity conditioning and testing”. The surface electrical resistance measured in accordance with the method described in JIS K 6911 “General Test Method for Thermosetting Plastics” in the state is preferably 1 × 10 ⁸ Ω / sq or more, and preferably 1 × 10 ¹¹ Ω / sq or less.

When the surface electrical resistance is less than 1 × 10 ⁸ Ω / sq, it is possible to prevent occurrence of a paper jam problem in an automatic tailoring machine while corresponding to recent high-speed offset rotary printing. However, if the surface electrical resistance exceeds 1 × 10 ¹¹ Ω / sq, jamming in an automatic tailoring machine may be promoted.

In addition, since the surface of the web, that is, the surface of the newsprint, comes into contact with the tailoring plate of the automatic tailoring machine, the offset measured in accordance with JIS K 6911 in a standard state in conformity with JIS P 8111. The surface electrical resistance of the newsprint for printing is particularly preferably 1 × 10 ⁸ Ω / sq or more and 1 × 10 ¹¹ Ω / sq or less on the surface thereof.

  In general, newsprint is used in various printing machines, printing conditions, etc. for each printing station. Therefore, when using the newsprint for offset printing of the present invention, based on the use conditions such as the type of printing machine and printing conditions, the average dynamic friction force and the surface electrical resistance are, for example, within the above ranges, respectively. It is preferable to appropriately adjust the ratio of (A) surface sizing agent, (B) paper strength enhancing agent, and (C) conductive agent contained in the surface treatment agent.

Further, the newsprint for offset printing of the present invention has a density measured according to the method described in JIS P 8118 “Paper and paperboard—Test method for thickness and density”, preferably 0.70 g / cm ³ or less, still more preferably 0.68 g / cm ³ or less, and preferably 0.50 g / cm ³ or more, further preferably 0.55 g / cm ³ or more.

If the density is less than 0.50 g / cm ³ , the amount of the water-soluble resin according to the present invention penetrated into the base paper is large, and it may be difficult to obtain newsprint for offset printing having desired water absorption and surface strength. There is. On the other hand, when the density exceeds 0.70 g / cm ³ , it becomes difficult to obtain newspaper for offset printing having a desired stiffness, and workability such as wrinkling in high-speed offset rotary printing is reduced. There is a fear.

Furthermore, the newsprint for offset printing of the present invention preferably has a basis weight of 43 to 46 g / m ² measured in accordance with the method described in JIS P 8124 “Method of measuring basis weight”, and is lightweight. .

When the basis weight exceeds 46 g / m ² , the occurrence of a paper jam problem in an automatic tailoring machine, which is caused by a lightweight thing mainly composed of waste paper pulp, is small. On the other hand, when the basis weight is less than 43 g / m ^2, it is difficult to produce newspapers for offset printing mainly composed of waste paper pulp due to a decrease in paper quality strength. It is difficult to obtain newsprint for offset printing that can prevent the occurrence of paper jam troubles.

  The newsprint paper for offset printing of the present invention has an ash content in the paper measured in accordance with JIS P 8251 of 5% by mass or more, and more preferably 7% by mass or more. Further, in addition to maintaining a sufficient surface strength, a water-soluble resin in which a filler contained in the base paper as an ash, preferably calcium chestnut calcium carbonate and / or hydrated silicic acid not subjected to a drying treatment is applied to the base paper Is preferable in providing newsprint paper that does not generate paper dust while being compatible with high-speed offset rotary printing such as 170 to 200,000 copies / hour. The paper jam problem in the automatic tailor can be solved by the synergistic effect.

  In addition, in order to eliminate the possibility that the entanglement between the raw material pulp fibers is reduced and the paper quality is reduced, or the ratio of the filler not fixed to the raw material pulp fibers is increased and the problem of paper dust and white spots is developed. The middle ash content is preferably 20% by mass or less, more preferably 15% by mass or less.

  Next, the newspaper for offset printing of the present invention will be described in more detail based on the following examples, but the present invention is not limited to these examples.

Preparation Examples 1 to 10 and Comparative Preparation Examples 1 to 4 (Preparation of surface treatment agent)
The following (A) surface sizing agent, (B) paper strength enhancer, and (C) conductive agent are mixed at room temperature so as to have a uniform composition at the ratio (solid content mass ratio) shown in Table 1. The surface treatment agent was obtained by stirring.

(A) Surface sizing agent Styrenic polymer: Cationic (Brand name: Vasoplast 8838, manufactured by BASF Corporation)
Acrylic polymer: Cationic (Brand name: Vasoplast 250D, manufactured by BASF Corporation)
Alkyl ketene dimer (AKD): cationic (trade name: SE2360, manufactured by Seiko PMC Co., Ltd.)

(B) Paper strength enhancer / oxidized starch oxidized starch A: (Daio Paper Chemical Co., Ltd., weight average molecular weight: 300,000)
Oxidized starch B: (Daioh Paper Chemical Co., Ltd., weight average molecular weight: 500,000)
Oxidized starch C: (manufactured by Daio Paper Chemical Co., Ltd., weight average molecular weight: 600,000)
Oxidized starch D: (manufactured by Daio Paper Chemical Co., Ltd., weight average molecular weight: 700,000)
Oxidized starch E: (Daioh Paper Chemical Co., Ltd., weight average molecular weight: 800,000)
Oxidized starch F: (trade name: SK-20, manufactured by Nippon Corn Starch Co., Ltd.,
(Weight average molecular weight: 640,000)
Oxidized starch G: (trade name: MS3800, manufactured by Nippon Food Processing Co., Ltd.,
(Weight average molecular weight: 490,000)
Hydroxyethylated starch Ethylated starch A: (trade name: PG-270, manufactured by Penford Gum,
(Weight average molecular weight: 1 million)
Ethylated starch B: (trade name: ETHYLE-2025, manufactured by Steele,
(Weight average molecular weight: 540,000)
・ Polyacrylamide resin PAM: (trade name: DS4344, manufactured by Seiko PMC Co., Ltd.)

(C) Conductive agent / sodium chloride (trade name: Nami-Sho, Nihonkaisui Co., Ltd.)

Examples 1 to 10 and Comparative Examples 1 to 4 (Manufacture of newsprint for offset printing)
A pulp slurry was obtained by adding the filler shown in Table 2 to 100% by mass of the deinked waste paper pulp (disaggregation / deinked waste paper pulp) so as to have an ash content in the paper shown in Table 3.

  Next, the obtained pulp slurry was made with a gap former type paper machine at a paper making speed of 1300 m / min to produce a base paper. The surface treatment agent shown in Table 2 was applied to the front and back surfaces of this base paper by the coating method shown in Table 2 so that the coating amount on one side shown in Table 2 was obtained, thereby obtaining newspaper for offset printing.

The fillers shown in Table 2 are as follows.
Filler 1: Chestnut calcium carbonate (Oil absorption: 180 ml / 100 g, BET specific surface area: 25 m ² / g,
(Volume average particle diameter: 5 μm)
Filler 2: Light calcium carbonate (trade name: Tama Pearl 121, manufactured by Okutama Kogyo Co., Ltd.)
Filler 3: Hydrated silicic acid (manufactured by Eliere Chemical Co., Ltd., volume average particle size: 5 μm,
No drying process)

  Table 2 also shows the proportion of the conductive agent (C) on the front and back surfaces. The content ratio of the conductive agent (C) was obtained by dividing the obtained newspaper for offset printing into two parts (peeling into two layers) using a razor and an adhesive tape in the thickness direction (Z-axis direction). The amount of sodium chloride contained in the paper layer on each of the front and back surfaces was calculated by measuring with a quantification means (salt content measurement) by the Mole method. The Mall method will be described below.

[Mohr method]
The Mole method is a kind of precipitation titration. Using a potassium chromate solution as an indicator, a silver nitrate solution is dropped into a sample solution containing sodium chloride. The dropped silver nitrate reacts with chloride ions of sodium chloride to form a white precipitate of silver chloride as shown in formula (1-1). However, when the chlorine ions are not consumed, silver nitrate reacts with the indicator potassium chromate to form a reddish brown precipitate of silver chromate as shown in formula (1-2). The end point is when the solution is reddish.
NaCl + AgNO ₃ → NaNO ₃ + AgCl ↓ (white) (1-1)
2AgNO ₃ + K ₂ CrO ₄ → 2KNO ₃ + Ag ₂ CrO ₄ ↓ (reddish brown) (1-2)
In order to generate a reddish brown precipitate of silver chromate to an extent that can be recognized, a little more silver nitrate is required from the equivalent point. Therefore, it is necessary to perform a blank test to correct the titration value.

  In the blank test, potassium chromate is added to the same amount of water as at the end of the titration, and calcium carbonate is added until the turbidity is about the same, and titrated with silver nitrate. Since the titration required for the blank test is the same as the amount of silver nitrate required to produce silver chromate to the extent that it can be recognized after equivalence, subtract the blank test titration from the titration in this test. The value obtained is the amount of silver nitrate required for the equivalent in this experiment. The silver nitrate solution must be standardized with a sodium chloride standard solution.

  Each physical property of the obtained newsprint for offset printing was measured by the following method. These results are shown in Tables 3 and 4. Also, commercially available newsprint (Comparative Example 5: Commercial product A (with hydrated silicic acid added internally and no conductive agent contained), Comparative Example 6: Commercial product B (calcium carbonate added internally and no conductive agent contained) Each physical property was measured in the same manner, and the results are also shown in Tables 3 and 4.

(A) Basis weight It measured based on JISP8124.

(B) Paper thickness and density It measured based on JISP8118.

(C) Ash content in paper Measured according to JIS P8251.

(D) Average dynamic friction force In accordance with JIS P 8147, the average dynamic friction force between the newspaper surface for offset printing (paper flow direction) and the metal surface (the surface of the stainless steel plate having a surface roughness Ra of 0.4 or less) is measured. did.

(E) Surface electrical resistance Surface electrical resistance (surface, back surface) was measured according to JIS K 6911 under standard conditions of a temperature of 23 ± 1 ° C. and a relative humidity of 50 ± 2% in accordance with JIS P8111.

(F) Stiffness The stiffness in the vertical direction (Clark stiffness) was measured in accordance with the method described in JIS P 8143 “Test for stiffness test by paper weight bending method (Clark method)”.

(G) Air permeability JAPAN TAPPI No. The measurement was performed according to the method described in 5-1, "Paper and paperboard-Test method for smoothness and air permeability-Part 1: Smoother method".

  Next, each characteristic was investigated about the newsprint for offset printing of Examples 1-10 and Comparative Examples 1-4, and the commercial item A and the commercial item B based on the following test examples 1-2. The results are shown in Table 4.

Test example 1 (paper jam in automatic tailor: jamming rate)
The ratio of the number of failures due to jamming when 50 windings were made with an automatic tailor (manufactured by Kanada Machinery Co., Ltd., PPR1 type) was taken as the jamming rate.

Test example 2 (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.

In each of the newspapers for offset printing of Examples 1 to 10, a surface treatment agent containing (A) a surface sizing agent, (B) a paper strength enhancing agent, and (C) a conductive agent is applied to the front and back surfaces of the base paper. Therefore, the average dynamic friction force is adjusted to 1.50 to 3.00 mN, the surface electric resistance is adjusted to 1 × 10 ⁸ to 1 × 10 ¹¹ Ω / sq, and the basis weight is 43 to 46 g / m ^2. Although it is moderately lightweight, the density is 0.55 to 0.70 g / cm ³ , and the ash content in the paper is 6.5% by mass or more, it is possible to sufficiently prevent the occurrence of paper jam troubles in the automatic tailoring machine. It can be seen that the higher surface strength is maintained.

On the other hand, all the newspapers of Comparative Examples 1 to 4 do not contain (C) a conductive agent, and (A) a surface treatment agent containing only a surface sizing agent and (B) a paper strength enhancer is the base paper. Because it is coated on the front and back surfaces, the average dynamic friction force exceeds 3.5 mN, the surface electrical resistance is as large as 1 × 10 ¹² Ω / sq, and the frequency of paper jam troubles in the automatic tailor is high. It can be seen that the surface strength is also reduced.

In addition, commercial products A and B originally contain no conductive agent and have printing suitability as newsprint, but have a large surface electrical resistance of 1 × 10 ¹⁵ to 1 × 10 ¹⁶ Ω / sq. The occurrence frequency of paper jam troubles in the tailor was high.

  The newsprint for offset printing of the present invention can be used particularly suitably for high-speed color printing, for example.

Claims (5)

A newspaper containing a filler, made by a neutral papermaking method, and having a surface treatment agent applied to the front and back surfaces of the base paper,
The base paper is mainly composed of waste paper pulp,
The surface treatment agent is at least (A) a surface sizing agent,
(B) A paper strength enhancer and (C) a conductive agent, and the ratio of (A) surface sizing agent, (B) paper strength enhancer, and (C) conductive agent in the surface treatment agent is a solid content. In terms of mass ratio, (A) :( B) :( C) = 5: 100: 3 to 20: 100: 17, and the total coating amount on both surfaces in terms of solid content of the surface treatment agent is 0.00. Newsprint paper for offset printing, which is 1 to 2.0 g / m ² . The newsprint for offset printing according to claim 1, wherein the filler is calcium chestnut calcium carbonate and / or hydrated silicic acid.   (B) Newsprint paper for offset printing according to claim 1 or 2, wherein the paper strength enhancer is oxidized starch, and the weight average molecular weight of the oxidized starch is 500,000 to 800,000.   The newsprint for offset printing according to claim 1, 2 or 3, wherein the ash content in the paper measured in accordance with JIS P 8251 is 5 to 20% by mass. The average dynamic frictional force between the newspaper surface for offset printing (paper flow direction) and the metal surface measured according to JIS P 8147 is 1.50 to 3.00 mN, and the temperature is 23 ± 1 according to JIS P 8111. The surface electrical resistance measured according to JIS K 6911 in a standard state at 50 ° C. and a relative humidity of 50 ± 2% is 1 × 10 ⁸ to 1 × 10 ¹¹ Ω / sq. The newsprint paper for offset printing as described in one.