JP2008231612A - Printing paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide printing paper having good rotary offset printing operability even when supplied to multicolor offset high-speed rotary printing using a cold setting type ink in spite of light weight, having good ink setting properties and excellent printability and maintaining high printing opacity though having high ink density and inking properties without causing problems of color drift. <P>SOLUTION: The printing paper comprises pulp and a filler as at least constituent components. The pulp contains 30-100 mass% of deinked used paper pulp based on the total pulp component. At least calcium carbonate in the form of chestnuts in burrs in which calcite-based calcium carbonate or aragonite-based calcium carbonate is aggregated or crystallized in the form of the chestnuts in the burrs is contained as a filler. The basis weight according to JIS P 8124 is 38-48 g/m<SP>2</SP>and the paper surface pH is 6-10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to printing paper. More specifically, the present invention relates to a printing paper particularly suitable for offset rotary printing using a cold set ink.

In order to reduce the burden of delivery work, reduce delivery costs, and effectively use resources, printing papers such as newspapers and free papers that are used daily in large quantities are desired to be lighter, especially in recent newspapers, The use of lightweight materials with a basis weight of 38 to 48 g / m ² is mainly used.

  However, as the weight reduction and effective use of resources increase, the ratio of used paper increases, resulting in a decrease in blank paper opacity and printing opacity of the obtained printing paper. Therefore, as a measure for reducing the opacity, an inorganic filler is usually blended into the raw material pulp. However, due to the increased distribution of the inorganic filler, troubles such as a decrease in the surface strength of printing paper and generation of paper dust have occurred. In recent years, with the increase in advertising media, there is an increasing demand for the printing surface quality of the advertising surface on printing paper. For this reason, for example, newspaper companies and printing companies that increase the speed of rotary presses and increase the number of tower presses for double-sided color printing are increasing, and efforts are being made to improve the printing surface quality in multicolor printing with high-speed offset rotary printing. . However, particularly in such multi-color printing (addition of a double-sided color tower press) in high-speed offset rotary printing, there is a problem in that printability and print paper opacity are reduced.

  Problems such as those described above cannot be addressed by conventional methods such as a technique for physically flattening the surface of the base paper or a means for applying a surface treatment agent to the surface of the base paper. This is because, for example, when the surface of a base paper containing a large amount of deinked waste paper pulp or mechanical pulp is subjected to a flattening treatment, the paper is once made, deinked by physical and chemical means, and deteriorated, and the pulp fiber becomes brittle. However, it becomes paper dust and drops from the surface of the printing paper, and also facilitates the dropping of the filler contained in the printing paper, leading to contamination of the printing equipment and printing defects.

  Therefore, as a technique for solving such a problem, for example, in Patent Document 1, a conventional calendar formed of a metal roll is replaced with a soft calendar including a combination of an elastic roll and a metal roll, and a metal roll (heat roll) is used. ) Is flattened at a temperature of 20 to 150 ° C. to produce a newspaper for offset printing with a small amount of paper dust. However, the physical flattening process reduces the rigidity of the paper, worsens the handling as newsprint, makes it difficult for the reader to handle the newsprint, and makes the newsprint surface more precise, so The absorption drying property is hindered, and causes problems such as ink stains and set-off.

On the other hand, in the technique of simply applying starch (surface treatment agent) to the surface of the base paper, for example, a starch application amount exceeding 2.0 g / m ² is required. As a result, there is a problem that nepari occurs, and it becomes difficult for the newsprint to be peeled off from the blanket and the workability is lowered.

Therefore, as a technique for solving such a problem, for example, Patent Document 2 discloses that a high-speed printing with a cold-set ink is performed by applying a newsprint coating composition containing a specific polymer latex to a newsprint base paper. In color offset rotary printing, newspapers are excellent in offset printing suitability such as surface strength, ink fillability, ink setability, etc. and tensile strength (especially wet tensile strength), and a good balance between these offset printing suitability and tensile strength. Techniques for obtaining a coating composition for paper and newsprint are disclosed. This is because latex generally has high film properties, so the strength of the newsprint surface is increased, and when printing is performed using cold-set ink, the ink is retained on the newsprint surface, so that the ink setting properties and ink setting properties are improved. Thus, it is intended to obtain offset printing aptitude. However, such a polymer latex has too high film-forming property, and the ink setting property of the cold set ink in newspaper printing is warped and causes problems such as rubbing stains and ink back-off.
Japanese Patent Laid-Open No. 2002-285496 JP-A-6-123099

  The present invention has been made in view of the above-mentioned background art, and in recent years, printing operability in high-speed offset rotary printing using 170 to 180,000 copies / hour using a cold-set type ink has become mainstream. Another object of the present invention is to provide a printing paper in which conventional problems such as printability such as color misregistration and printing opacity are improved.

The present invention
Printing paper comprising at least pulp and filler as constituents,
The pulp contains 30 to 100% by mass of deinked waste paper pulp based on the total pulp components,
As the filler, at least calcite calcium carbonate or aragonite calcium carbonate aggregated or crystallized in a chestnut shape is contained, characterized in that,
The present invention relates to a printing paper having a basis weight based on JIS P 8124 of 38 to 48 g / m ² and a paper surface pH of 6 to 10.

According to the present invention, even when the basis weight is as small as 38 to 48 g / m ² and it is light, even when it is subjected to multicolor offset high-speed rotary printing using a cold set ink, the offset Printing with good rotary printing operability, high ink density and ink fillability, good ink setting, no color misregistration problems, excellent printability, and high printing opacity Paper is provided.

(Embodiment)
The printing paper of the present invention comprises pulp and filler at least as constituents, contains deinked waste paper pulp in an amount of 30 to 100% by weight based on the total pulp components, and contains calcite calcium carbonate or aragonite calcium carbonate as filler. The basis weight is 38 to 48 g / m ² and the pH of the paper surface is 6 to 10, which contains at least calcium chestnut calcium carbonate agglomerated or crystallized in a chestnut shape.

  First, the pulp used in the present invention will be described. The pulp constituting the base paper of the printing paper of the present invention contains 30 to 100% by mass of deinked waste paper pulp based on the total pulp components.

  Such an increase in the amount of deinked waste paper pulp is preferable from the viewpoint of environmental conservation, and in recent years, particularly in printing paper, the use of deinked waste paper pulp and higher blending have been demanded from the viewpoint of effective use of resources. On the other hand, increasing the amount of deinked waste paper pulp, as described above, generally makes it difficult to ensure a predetermined printing paper strength, and lowers the printability such as ink setting property and ink setting property. 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, printing paper containing a large amount of deinked waste paper pulp has high density and low cushioning properties, resulting in poor ink setability, poor ink setting, and generation of paper dust due to reduced surface strength. As a result, the ink density is lowered due to the ink.

  In particular, among the deinked waste paper pulp, the use of deinked waste paper pulp from which newspaper wastepaper has been deinked is similar in constituent materials and is most efficient in terms of resource recycling. Deinked waste paper pulp that has been recycled repeatedly exists, and the pulp fiber deteriorates due to repeated recycling, which not only reduces the opacity of the printing paper but also makes it brittle, paper dust and powder, and the surface of the paper. The problem arises that the fibers are picked up by an offset printing blanket.

  However, in the present invention, as will be described later, as a filler to be blended with the pulp, at least a specific calcium chloride calcium carbonate is contained, such deinked waste paper pulp is 30 to 100% by mass based on the total pulp components. Despite being contained in large quantities, the printing paper of the present invention solves the conventional problems when a large amount of deinked waste paper pulp is blended, has good printing operability, high ink concentration, and ink inking. In addition, the ink setting property is good, the problem of color misregistration does not occur, the printability is excellent, and the high printing opacity is maintained.

  As the deinked waste paper pulp used in the present invention, for example, tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, reprint waste paper, flyer waste paper, office waste paper, corrugated waste paper, upper white waste paper, Kent waste paper, imitation waste paper, ground Disaggregated / deinked waste paper pulp, disaggregated / deinked / bleached deinked waste paper pulp, etc. produced from ticket waste paper and the like can be used, and one or more of these can be appropriately selected and used.

  In the present invention, from the viewpoint of weight reduction of printing paper and effective use of resources, the deinked waste paper pulp is 30 to 100% by mass, preferably 50 to 100% by mass, more preferably 70 to 100% by mass based on the total pulp components. % Content.

  In addition to the deinked waste paper pulp, for example, Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp as a constituent component of printing paper as long as the purpose of the present invention is not impaired (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), etc .; Hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKKP), hardwood semibleached kraft pulp (LSBKP), coniferous semibleached kraft pulp (NSBKP) ), Hardwood sulfite Pulp, such as chemical pulp such as soft wood sulfite pulp, be mentioned various known pulp, one or more from among these suitably selected, can be used to adjust the ratio.

  The bleaching method for producing the chemical pulp is not particularly limited, but chlorine-free bleached (ECF) pulp bleached without using molecular chlorine such as chlorine gas in the bleaching process, and further chlorine dioxide Chlorine-free bleached (TCF) pulp bleached without using any chlorine compound is preferred from the viewpoint of environmental protection.

  The printing paper of the present invention contains at least a filler as a constituent component together with the pulp. The filler used in the present invention contains at least calcium chloride calcium carbonate obtained by agglomerating or crystallizing calcite calcium carbonate or aragonite calcium carbonate in a brown chestnut shape.

It is one of the great features of the present invention that it contains at least the above-mentioned calcium chestnut calcium carbonate as a filler. This chestnut calcium carbonate is used as a filler, and preferably has a pH of 6 to 10, more preferably as described later. In the case of making paper with a pH of 6.5 to 9.5 neutral to alkaline, the optical properties and strength of the resulting printing paper are simultaneously improved. That is, due to the buffer effect of calcium carbonate, the papermaking pH becomes 7-9, and when the papermaking pH is neutral or alkaline, each fiber is sufficiently stretched compared to the acidic case, so that the fibers are hydrogenated. The area forming the bond is increased. Therefore, when the ash content is about the same as that of acidic printing paper, the neutral printing paper has a higher paper strength. As a result, even if the printing weight is as low as 38 to 48 g / m ² , Sufficient strength to withstand color offset high-speed rotary printing can be obtained.

  In addition, the printability of the printing paper of the present invention blended with calcium chestnut calcium carbonate as a filler is very good compared with, for example, conventional printing paper blended with spindle type, columnar, cubic, or needle-like light calcium carbonate. , Whiteness is also increased.

  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 adjusting the supply method of carbon dioxide-containing gas, or adding dehydration, drying, or heat treatment, for example, by adding an additive such as condensed phosphoric acid or a metal salt thereof, the spindle-type or columnar crystal structure has a chestnut-like shape. Obtained by agglomeration or 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 oil chestnut calcium carbonate used in the present invention has an oil absorption amount of 100 to 100 according to “Pigment test method—Part 13: Oil absorption amount—Section 1: Refined linseed oil method” described in JIS K 5101-13-1. It is preferable that it is 250 ml / 100g, a BET specific surface area is 5-50 m < ² > / g, and a volume average particle diameter is 1.0-10.0 micrometers.

  When the amount of oil absorption of Hashiguri calcium carbonate is less than 100 ml / 100 g, for example, there is a risk that the blank paper opacity may be lowered and bleeding may increase in cold-set offset printing, while if it exceeds 250 ml / 100 g, The vehicle component 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 100 ml / 100 g or more, more preferably 110 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 5 m ² / g, voids in the aggregated structure may decrease, and ink absorbability may decrease. On the other hand, if it exceeds 50 m ² / g, the filler dispersion As the diluted viscosity of the ink becomes high, the operability is lowered, or the drying property of the cold-set offset ink taken in is lowered, and there is a possibility that rubbing stains and print set-off occur. Therefore, it is preferable that the BET specific surface area of Oguri calcium carbonate is 5 m ² / g or more, more preferably 10 m ² / g or more, and 50 m ² / g or less, more preferably 20 m ² / g or less.

  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 apparatus (model number: Frosorb 2300, Shimadzu Corp. make).

  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, paper strength and printability may be reduced. Therefore, the volume average particle diameter of the potato chestnut calcium carbonate is preferably 1.0 μm or more, more preferably 1.8 μm or more, and is preferably 10.0 μm or less, more preferably 9.6 μm or less.

  In the present specification, the volume average particle size of calcium chloride calcium carbonate is a particle size distribution measuring device 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 with an ultrasonic disperser (output: 80 W). It means a value measured with a laser type microtrack particle size analyzer, manufactured by Nikkiso Co., Ltd.

  Furthermore, the aspect ratio (the ratio of the major axis to the minor axis (major axis / minor axis)) of calcium chloride calcium carbonate is 3.5 or less, and further 3 from the viewpoint of further improving the opacity and printability of the printing paper. .4 or less, and from the viewpoint of sufficiently suppressing a decrease in paper strength of the printing paper, it is preferably 2.0 or more, more preferably 2.4 or more.

  In the present invention, in order to sufficiently improve the printability, opacity, whiteness and the like of the target printing paper, the above-mentioned calcium carbonate is added to the filler in an amount of 5% by mass or more, further 20%. It is preferably contained in an amount of at least 40% by mass, particularly at least 40% by mass.

  In the present invention, a filler containing at least calcium chloride calcium carbonate is used, but when white carbon is further contained as the filler, the paper structure becomes more bulky, and cushioning properties are imparted to the printing paper, For example, there is an advantage that the cold-set type ink is further improved, and the blank paper opacity, printing opacity, printability and the like are further improved.

  Further, the whiteness of the white carbon alone preferably used is low in contribution to the base paper of the normal printing paper. However, when used together with calcium chloride calcium carbonate, the whiteness of the printing paper increases as a result.

  Examples of the white carbon used in the present invention include wet silica, calcium silicate, aluminum silicate and the like, which are generally used for papermaking as a highly oil-absorbing filler.

White carbon improves opacity due to the formed porous aggregate structure, but in particular, the apparent specific gravity is 0.10 to 0.25 g / ml, and the BET specific surface area is 100 to 250 m ² / g. The particle size distribution by the Coulter counter method is as follows: D50 μm is 3.0 to 8.0, D80 μm is 8.0 to 18.0, D97 μm is 19.0 to 40.0, and conforms to JIS K 5101-13-1. The oil absorption is preferably 190 to 230 ml / 100 g. As the white carbon, wet silica having a primary particle diameter of 10 to 50 nm and a secondary particle diameter of 15 to 20 μm is particularly preferable from the viewpoint of further improving printability.

  Although the opacity and printability are further improved by blending white carbon, if there is too much such white carbon, ink sinking may occur and ink density may be lowered. Further, since white carbon is generally expensive, in order to reduce production costs, it is preferable to adjust so that the amount of use thereof does not become excessive. Therefore, in order to further improve the printability, bulkiness, and paper strength in a well-balanced manner and to reduce the cost, the ratio of calcium chloride calcium carbonate to white carbon (calcium calcium carbonate: white carbon (mass ratio)) is 5:95. As described above, it is further preferably 20:80 or more, 80:20 or less, and more preferably 60:40 or less.

  In the present invention, the filler contains the above-mentioned calcium chestnut calcium carbonate, and the calcium chloride calcium carbonate and white carbon are used in combination, if necessary. Engineered kaolin, clay, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, zeolite, barium sulfate, zinc oxide, aluminum oxide, magnesium oxide, silicic acid, colloidal silica, colloidal alumina, satin An inorganic filler such as white or an organic filler can be used alone or in combination of two or more.

  The ratio of the filler to the pulp is the pulp solid content (absolutely dry) in order to sufficiently exhibit the effects of improving the printing operability, printability, etc. while maintaining high printing opacity due to the use of the filler. 10 kg / ton or more, more preferably 20 kg / ton or more, and in order to prevent a decrease in the surface strength of the printing paper and the generation of paper dust, pulp solids (absolutely dry) Is preferably 40 kg / ton or less, more preferably 30 kg / ton or less.

  In order to obtain the printing paper of the present invention, a filler is added to the pulp slurry made of the above-mentioned pulp, for example, preferably pH 6 to 10, more preferably pH 6.5 to 9.5 neutral to alkaline. It is possible to adopt a method of making paper using a normal paper machine such as a long net paper machine or a twin wire type paper machine by adjusting conditions such as pH, but in the present invention, condensation is performed at the pulp preparation stage. Adding a flocculant and further adding a flocculant in the pre-stage of the paper making process following the pulp preparation step promotes the aggregation of fine inorganic particles mixed in the pulp suspension, and further adds inorganic particles to the raw pulp. It is preferable because it has the advantage of improving the yield of the filler by adhering, and improving the drainage and obtaining the wet end stability.

  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. Among these, it is preferable to use at least one of PAM, PDADMAC, PAm, and PEI.

  The organic polymer-based coagulant has a charge density of 3 meq / g in that, for example, when calcium chloride calcium carbonate and white carbon are used in combination, the white carbon can be retained in the pulp and the drainage can be improved. As mentioned above, it is more preferable that it is 10 meq / g or more. When the charge density is less than 3 meq / g, it is necessary to increase the amount of the organic polymer coagulant in order to increase the cation requirement of the pulp to a predetermined value, which increases the cost and increases the ground of the printing paper. The sheet formation may be reduced. The average molecular weight of the organic polymer coagulant is preferably 700,000 to 1.3 million, more preferably 800,000 to 1,200,000. If the average molecular weight is less than 700,000, the cohesive force is weak, and the fixing of the chestnut calcium carbonate and the white carbon particles to the wet paper may be insufficient, and as a result, the intended effect may not be improved. If it exceeds 10,000, the cohesive force is too strong, so the paper texture will decrease, and in order to maintain good paper texture, the addition amount must be reduced, and the desired effect can also be improved. There is no fear.

  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, the addition amount of the organic polymer coagulant depends on the addition amount of the inorganic coagulant described later, but is preferably 1000 to 4000 ppm, more preferably 1200 to 3800 ppm in solid content with respect to the pulp. . 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 4000 ppm, the paper texture may be lowered and the cost may be increased.

  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 addition, when using a cationic coagulant especially among the said coagulants, it is preferable that the addition amount is 50-400 ppm with a pure part with respect to a pulp, Furthermore, it is preferable that it is 100-300 ppm. As such a cationic coagulant, a polymer compound similar to the aggregating agent described later, that is, a cationic water-soluble polymer or copolymer, can be used, but those having a small molecular weight are preferably used. That is, as the cationic coagulant, a cationic water-soluble polymer having an average molecular weight of 1,000,000 to 1,200,000 and a ratio of the cationic monomer of 5 to 100 mol%, further 10 to 100 mol%, or Copolymers can be used. Representative examples of such cationic coagulants include PAm, PEI and the like. If the average molecular weight of the cationic coagulant is less than 1 million, the effect of using the cationic coagulant may not be sufficiently exhibited. However, there is a risk of high costs.

  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.

  In particular, when a cationic flocculant is used as the flocculant described later, it is preferable to add the coagulant at an early stage of pulp preparation, that is, at an early stage with respect to the pulp slurry. After that, it is optimal to add the flocculant before the paper making process, that is, at the head box before the paper making net. When such an addition procedure is employed, in the slurry solution state before the papermaking raw material is placed on the papermaking net, the cohesive effect of the coagulant increases the adhesion between the pulp fiber and calcium carbonate, and white carbon that is suitably used together. In papermaking nets, the cohesive effect of the flocculant strengthens the adhesion between the pulp fiber and the calcium carbonate and white carbon. As a result, the yield of paper chestnut calcium carbonate and white carbon used in combination is further improved. And when such an addition procedure is taken, the effect that smooth paper-making work progresses is exhibited with the further improvement of the yield of the chestnut calcium carbonate and the white carbon used together suitably.

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

  As the flocculant, a cationic flocculant is particularly suitable for an anionic pulp and filler. 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 quantity of the chestnut calcium carbonate and white carbon which are missing in the papermaking net can be remarkably reduced.

  Moreover, it is preferable that the addition amount of a flocculant is 100-150 ppm with a pure part with respect to a pulp, Furthermore, it is preferable that it is 120-140 ppm. If the addition amount of the flocculant is less than 100 ppm, there is a possibility that the yield improvement effect of calcium chloride or white carbon may not be sufficiently obtained, while if it exceeds 150 ppm, the formation of the printing paper may be lowered.

  In the present invention, for example, by using the coagulant and the flocculant, the formation index of the printing paper is 5.0 to 10.0%, more preferably 6.0 to 9.5%, and particularly 8.0 to 8. It is preferable to adjust to 5%. The printing paper 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, the formation index is preferably 5.0% or more. On the other hand, even if the formation index exceeds 10.0%, it is difficult to obtain sufficient tensile strength in the vertical direction, and for example, in offset printing, ink absorption unevenness occurs particularly in color printing, and printability, particularly printing opacity. There is a risk of lowering.

  In the present specification, the formation index of printing paper refers to a value measured by a sheet formation tester (manufactured by Toyo Seiki Seisakusho).

  Further, when the printing paper of the present invention is manufactured, before preparing a plurality of stocks and supplying them to the seed box, the slurry of each stock is subjected to a cation demand measurement value measured using an online cation demand measurement device. Based on this, the amount of the coagulant added in the preparation stage can be controlled.

  Thus, by controlling the addition amount of the coagulant on-line, it is possible to control the potential according to the optimum cation demand. In particular, it is possible to feed back and control the rapid cation demand measurement value, stabilize the drainage at the wire part of the paper machine, and only reduce the paper breakage at the wet part. In addition, the formation of the obtained printing paper can be maintained well.

  The cation demand is the total charge of the anionic substance. An anionic substance (anionic trash) is a negatively charged substance, including pulp (including fine fibers), fillers (such as calcium carbonate and white carbon used in combination), and various wet end papermaking. Auxiliaries (other fillers, internal sizing agents, antifoaming agents, etc.), resin pitch, elution lignin and the like.

  By adding a cationic coagulant to the anionic substance and adding the anionic (or cationic) flocculant to the coagulated substance, the coagulated anionic substance aggregates to form a floc. Under such a mechanism, the pitch concentration can be reduced mainly by adsorbing the pitch to the pulp and passing the process together with the paper stock in a minimal state, or discharging the process out of the system. Thereby, dirt, a defect, a paper break, etc. can be reduced and productivity can be further improved. Further, the yield can be further improved by neutralization with an anionic substance, and when the anionic substance aggregates and forms a floc, the drainage state is improved. For this reason, it is preferable that the cation demand (or the amount thereof) is low with respect to the drainage state.

  A typical example of an apparatus for measuring an online cation demand as described above is a cation demand measuring apparatus (model number: PCT15 or PCT20, manufactured by Mutek). In the cation demand measuring apparatus, when the stock is introduced into the cell of the tester, the sample liquid flows between the cell cylinder and the piston by the operation of the upper and lower pistons, and electricity is generated by the distortion of the surface charge of the colloidal particles. Arise. The colloidal dissolved substance particles in the pulp suspension are charged with ions, and the charge requirement is measured by measuring the polymer electrolyte by using this.

  Thus, the printing paper of the present invention is obtained through the paper making process. In the present invention, it is preferable that, for example, a water-soluble polymer compound is applied to the front and back surfaces of the printing paper.

  As a result, for example, the vehicle of cold set type offset ink is quickly absorbed, and even if the amount of printing ink is increased by using a high-speed rotary press or using a tower press for double-sided color, sufficient absorption and drying properties are expressed, Excellent printing opacity, printability, etc. can be ensured.

The reason why the combination of calcium carbonate or white carbon and water-soluble polymer compound used in the present invention is preferable is that calcium carbonate is rich in three-dimensional porosity and has a large BET specific surface area. Based on a synergistic effect with a water-soluble polymer compound such as starch and / or polyvinyl alcohol (PVA), it is excellent in film formability when an offset ink receiving agent is applied to the surface of a printing paper. In particular, calcium chestnut calcium carbonate has a larger oil absorption than normal calcium carbonate, and a basis weight of 38 to 48 g / m is obtained by quickly absorbing and drying a cold set type offset ink on the surface of a printing paper and combining it with a water-soluble polymer compound. ^{Even if it is 2} and lighter, it exhibits an even better printing opacity improvement effect.

  Suitable water-soluble polymer compounds include, for example, starch and PVA, and these can be used alone or simultaneously.

  The type of starch is not particularly limited. For example, modified starch has an effect of improving tensile strength and surface strength while penetrating into paper, but exhibits neutrality or anionic property, and thus exhibits anionic property. The fixability to the pulp fiber surface is low and the 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. In the case of cationic starch, the fixability to pulp fibers is high, the coating property is excellent, and the surface strength is also improved.

  Furthermore, as said starch, esterified starch is more preferable. 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, 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.

  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. The hydroxyesterified starch 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. Among them, it is optimal to use a hydrophobic group-containing ester-modified tapioca starch in which a hydrophobic group is introduced into the end group of the ester-modified starch.

  Furthermore, the esterified starch that can be preferably used in the present invention has a carboxylic acid “—COOH” structure in the terminal group and is ionized like “—COO—” in the neutral region to form hydrogen bonds. The ester-modified starch, which exhibits thixotropic behavior based on showing rebound without being able to secure the connection due to, penetrates into the paper after application while showing fluidity when applied to the surface of printing paper This is preferable from the viewpoint of exhibiting a high film property on the paper surface. In particular, when used in combination with PVA or the like having a high coating property, which will be described later, even if a large amount of calcium chloride calcium carbonate, which is a filler added to the pulp, is used, ink density and ink setting properties can be further improved. As such esterified starch, 1-octenyl succinic 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. For example, when used in combination with PVA described later, printing operability and coatability, ink concentration, and ink setability Can be further improved.

  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.

As the starch, those having a viscosity (10%) of 30 × 10 ⁻³ Pa · s or less, more preferably 15 × 10 ^{−3 to} 25 × 10 ⁻³ Pa · s have a high viscosity on the paper surface. From the point that it can not penetrate into the paper and can remain on the paper surface.

  As described above, examples of the water-soluble polymer compound include PVA in addition to starch. In general, when PVA alone is applied to the front and back surfaces of printing paper, the surface strength is approximately three times that of the case where starch is applied alone, and the coating property is excellent, but the coating property is high. If a printing ink is used that penetrates into the paper and dries like a cold set ink, the ink absorbability of the printing ink is low, and sufficient ink setting properties may not be obtained. In addition, when a certain amount of PVA is applied alone, the treatment liquid containing the PVA has a high viscosity. 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 and the ink setting property is lowered while appropriately promoting the penetration of the printing ink solvent into the paper. Is also 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 fully saponified PVA is used, a coating having water resistance and heat resistance is more easily obtained on the printing paper surface than when partially saponified PVA is used.

  When such PVA is used, the affinity with starch is good, and it is possible to blend starch and PVA in a short time, further improving the operability and reducing the occurrence of mist in the coating equipment. be able to.

  By using PVA having the above characteristics, it is possible to realize high ink setting properties of offset ink while obtaining a high ink concentration. Further, when the printing paper is laminated after printing, ink transfer to the back surface can be sufficiently prevented.

  When starch and PVA are used in combination, the ratio of the two (starch: PVA (solid content mass ratio)) is 10: 0.8 to 10: 2.0, and further 10: 0.9 to 10: 1.2. It is preferable that If the ratio of PVA to starch exceeds 10: 2.0, the viscosity of the treatment liquid containing both will rapidly increase, which may cause uneven coating and mist, resulting in poor coating quality and damage around the equipment. On the other hand, if the ratio is less than 10: 0.8, there is no problem in the compatibility of starch and PVA, but when applied to the surface of printing paper, the synergistic effect of starch and PVA cannot be obtained, and the paper There is a risk of infiltration into the inside and uneven application. Therefore, by setting the ratio of both in this range, it is possible to ensure a synergistic effect between starch and PVA, and at the same time to develop a high ink concentration by retaining the filler component in the ink on the surface of the printing paper, It is possible to quickly absorb the solvent in the ink into the printing paper and to exhibit quick ink setting.

When the starch and PVA are used in combination as the water-soluble polymer compound applied to the front and back surfaces of the printing paper, these starch and PVA are 0.2 to 2.0 g / m ² per side on the front and back surfaces of the printing paper, Furthermore, it is preferably applied in an amount of 0.5 to 1.5 g / m ² (is unevenly distributed). When the amount of starch and PVA is less than 0.2 g / m ² , it becomes difficult to obtain sufficient film properties with these starch and PVA, and it is difficult for the filler component in the ink to stay on the surface of the printing paper. On the other hand, if it exceeds 2.0 g / m ² , a large amount of mist of the processing solution containing starch and PVA is generated around the coating equipment, and the peripheral equipment is soiled and caused by dirt. There is a risk of paper breaks and paper defects.

  In the present invention, a large amount of deinked waste paper pulp is used as the pulp, but when the above-mentioned specific calcium chloride calcium carbonate is used as a filler and starch and PVA are applied to the front and back surfaces, a large amount of deinked waste paper pulp is used. The shortcomings are covered, and at the same time, the synergistic effect of further improving the ink density and printability is exhibited.

  When a treatment liquid containing a water-soluble polymer compound such as starch or PVA is applied to the front and back surfaces of the printing paper, it is preferable to employ a film transfer system such as a gate roll coater or a blade. In particular, coating with a gate roll coater is optimal when applying contour coating with high coverage on the surface of printing paper with a low coating amount, unlike other coating methods, and does not apply a sudden shear force to the processing liquid. The processing solution used for circulation is excellent in stability, and a uniform film can be obtained at high speed. In particular, when thixotropic ester-modified starch is used, it exhibits fluidity when applied to the surface of the printing paper, but after application, the fluidity is suppressed, and the treatment liquid is difficult to penetrate into the paper. The high film property is imparted to the printing paper.

  In addition, when applying a treatment liquid mainly composed of starch and PVA as water-soluble polymer compounds on the front and back surfaces of the printing paper, for example, a size press or a rod metering size press may be adopted without adopting the film transfer method. It is also possible to employ conventionally known application means. However, if the contour coating along the unevenness of the surface of the printing paper is not applied, the coating property with starch and PVA becomes insufficient. For example, in the case of multicolor offset rotary printing using a cold set type ink, the ink concentration, the ink There is a risk that it may be difficult to obtain a printing paper sufficiently excellent in printability such as setability and ink fillability. Therefore, in order to apply the treatment liquid mainly composed of starch and PVA at a low concentration and a low coating amount on the front and back surfaces of the printing paper, it is optimal to adopt a film transfer method.

  Further, the printing paper of the present invention can be flattened by a calendar facility such as a super calendar, a gloss calendar, or a soft calendar.

The printing paper of the present invention thus obtained has a basis weight based on the “basis weight measuring method” described in JIS P 8124 of 38 g / m ² or more, preferably 40 g / m ² or more, and 48 g / m ^2. The weight is preferably 46 g / m ² or less. When the basis weight is less than 38 g / m ² , the opacity and the paper quality strength are insufficient, and the problem of paper breakage is likely to occur in the recent high-speed printing that reaches 170 to 180,000 copies / hour. On the other hand, when the basis weight exceeds 48 g / m ² , it becomes easy to ensure sufficient opacity, but it is difficult to handle as a lightweight printing paper.

  The paper surface pH of the printing paper is 6 or more, preferably 6.5 or more, and 10 or less, preferably 9.5 or less. Especially in high-speed rotary offset printing on newsprint, the dampening solution applied to the paper before printing varies depending on the newspaper company, but it is almost neutral. In order to reduce the risk of occurrence of defects, it is preferable to adjust to such a paper surface pH range.

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

  The ash content in the printing paper is measured in accordance with the method described in “Paper, board and pulp-ash content test method—525 ° C. combustion method” described in JIS P 8251, and is 7.0% or more, and further 7 It is preferably 2% or more, particularly 7.5% or more, 15.0% or less, more preferably 13.5% or less, and particularly preferably 10.0% or less. If the ash content is less than 7.0%, the ink setting property becomes insufficient when printing is performed on the printing paper, and there is a possibility that the ink may be easily transferred or rubbed. On the other hand, if the ash content exceeds 15.0%, a paper breakage trouble in the paper making process is likely to occur, productivity may be reduced, and contamination in the system may be easily caused. This is likely to occur and may cause a decrease in printing operability.

  Further, the whiteness of the printing paper is preferably 55% or more, more preferably 55.5 to 58%, as measured in accordance with “Testing Method for Hunter Whiteness of Paper and Pulp” described in JIS P 8123. . 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 opacity of the printing paper 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 printing paper 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 printing paper of the present invention has a density measured in accordance with “Thickness and density test method” described in JIS P 8118 of about 0.63 to 0.90 g / cm ³ , and JIS P 8119. That the Beck smoothness measured in accordance with "Paper and paperboard-smoothness test method using a Beck smoothness tester" is about 41 to 65 seconds, printing suitability and printing operation in high-speed rotary offset printing It is preferable in that the property can be further improved.

  Next, although the printing paper of this invention is demonstrated still in detail based on the following Examples, this invention is not limited only to these Examples.

Examples 1 to 13 and Comparative Examples 1 to 4 (Manufacture of printing paper)
Deinked waste paper pulp (disaggregation / deinked waste paper pulp) and mechanical pulp (TMP) are blended in the proportions shown in Table 1, and the filler consisting of varieties A and B shown in Table 2 is mixed with pulp solids (absolute Added in the proportions shown in Table 2, and further the coagulants (variety a and variety b) shown in Table 3 were added to obtain a pulp slurry.

  Subsequently, the flocculant shown in Table 3 was added to the obtained pulp slurry, and paper was made by a long net paper machine to produce a paper. A water-soluble polymer compound was applied to the front and back surfaces of this paper by the coating method shown in Table 4 so that the coating amount on one side (total amount of starch and PVA) shown in Table 4 was obtained to obtain a printing paper.

  The ratio of the filler shown in Table 2 (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 calcium and silica 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 15 kV.

  Each physical property of the obtained printing paper was measured by the following method. These results are shown in Table 5.

Moreover, commercial printing paper AC was made into Comparative Examples 5-7, and each physical property was measured similarly. These results are also shown in Table 5. In addition, the kind of filler mix | blended with these commercially available printing paper AC and the single-sided coating amount of a water-soluble polymer compound (starch) are as showing below.
Filler type Starch one side coating amount Printing paper A: White carbon 1.5g / m ²
Printing paper B: Spindle type calcium carbonate 1.2 g / m ²
Printing paper C: white carbon 1.0 g / m ²

(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) Opacity of printing 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 to the back-surface reflectance before printing when the amount of ink is 9% and the printing 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) It was dried for 24 hours according to “Paper, paperboard and pulp-standard conditions for humidity conditioning and testing” described in JIS P8111. 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 0.8, there is a possibility that a desired ink density may not be obtained in, for example, offset rotary printing in a newspaper company. Conversely, if the ink density exceeds 1.2, the ink density is sufficient. However, there may be a decrease in printing opacity and a problem of set-off.

  Next, each characteristic was investigated about the printing paper of Examples 1-13 and Comparative Examples 1-7 based on the following test examples 1-5. The results are shown in Table 6.

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), continuously 10,000 newspaper newspapers (trade name: News Zet Naturalis (black), manufactured by Dainippon Ink & Chemicals, Inc.) Copies were printed. 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 surface of the printing paper was visually observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
A: The entire surface of the printing paper is not removed at all.
○: Slightly removed on a part of the surface of the printing paper, but there is no practical problem.
Δ: Taken over the entire surface of the printing paper.
X: Significant removal on the entire surface of the printing paper.
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), printing with newspaper ink (trade name: Newsz Naturalis (black), manufactured by Dainippon Ink & Chemicals, Inc.) went. 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 on printing paper of 50 continuous windings. 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 printing machine (model number: Komori SYSTEMC-20, manufactured by Komori Corporation), continuous 4-color 4-color printing 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 the printing paper into a size of about 4 cm wide × about 6 cm long were prepared, 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.

From the results shown in Tables 5 and 6, all of the printing papers of Examples 1 to 13 use a specific calcium chloride calcium carbonate as a filler, and have a basis weight of 38 to 48 g / m ² and are lightweight. In addition, it can be seen that the pH of the paper surface is 6 to 10 neutral to alkaline, the whiteness and white paper opacity are high, and high printing opacity is maintained. Moreover, all the printing papers of Examples 1 to 13 have high ink concentration, good ink setability and ink fillability, excellent print operability, and high speed using cold set ink. It can be seen that the film has excellent characteristics suitable for offset rotary printing.

  On the other hand, since the printing paper of Comparative Examples 1 to 4 uses ordinary calcium carbonate as a filler, whiteness and white paper opacity are insufficient, and printing opacity is low. I understand. In addition, all of the printing papers of Comparative Examples 1 to 4 use cold set inks such as low ink density, poor ink setting and ink inking properties, uneven ink coloring, poor printing operability, etc. It can be seen that it does not have the characteristics necessary for high-speed offset rotary printing.

  In addition, the commercially available printing papers of Comparative Examples 5 to 7 are also inferior in ink setting property and ink inking property, cause uneven coloring of ink, inferior in printing operability, etc. It can be seen that it does not have the characteristics necessary for offset rotary printing.

  The printing paper of the present invention can be suitably used for offset rotary printing at a high speed of 170 to 180,000 copies / hour using a cold set type ink, which has become mainstream in recent years.

Claims (4)

Printing paper comprising at least pulp and filler as constituents,
The pulp contains 30 to 100% by mass of deinked waste paper pulp based on the total pulp components,
As the filler, at least calcite calcium carbonate or aragonite calcium carbonate aggregated or crystallized in a chestnut shape is contained, characterized in that,
Printing paper having a basis weight based on JIS P 8124 of 38 to 48 g / m ² and a paper surface pH of 6 to 10. Oguri calcium carbonate has an oil absorption of 100 to 250 ml / 100 g, a BET specific surface area of 5 to 50 m ² / g, and a volume average particle size of 1.0 to 10.0 μm in accordance with JIS K 5101-13-1. The printing paper according to claim 1.   The filler further contains white carbon, and the ratio of calcium carbonate and white carbon (calcium calcium carbonate: white carbon (mass ratio)) is 5:95 to 80:20. Printing paper.   The printing paper according to claim 1, 2, or 3, wherein a coagulant is added at a pulp preparation stage, and further a flocculant is added at a stage before the paper making process following the pulp preparation stage.