JP2011026714A - Newsprint paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide newsprint paper that has high filler sticking tendency between pulp fibers even by using an internal filler, high opacity and oil absorption property, reduces contamination in a machine system in a production step due to a small amount of paper powder drop and improves machine operability. <P>SOLUTION: The newsprint paper contains at least two kinds of fillers in pulp. White carbon and silica-containing particle are used as the two kinds of the fillers. The total of the two kinds of the fillers has an area particle diameter distribution having maximal values in the ranges of (A) ≥15 μm and ≤25 μm and (B) ≥1 μm and ≤15 μm, respectively, in the area particle diameter distribution totaled for every 0.5 μm. The silica-containing particles having the maximal values in the rages of (A) and (B) are preferably silica-coated regenerated particles obtained by coating the surfaces of regenerated particles comprising a deinked floss as a main raw material with silica. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to newsprint with high opacity, and in particular, relates to newsprint suitably used for offset ink rotary printing.

  Newspapers and other papers are in great demand for weight reduction from the standpoints of logistics costs and resource saving. However, when the weight of the paper is reduced, the thickness of the paper is reduced, and opacity, particularly opacity after printing, is greatly reduced. The decrease in opacity after printing causes a phenomenon that is seen through from the opposite side, that is, so-called back-through, and reduces the printing surface quality on the printed back side.

  Conventionally, in order to improve the opacity of newsprint, mechanical pulp having thick fibers has been frequently used as raw material pulp. However, in recent years when high blending of used paper pulp is desired, it is difficult to use the mechanical pulp as a main raw material in newsprint. In addition, with the widespread use of recycled paper, in recent years, recycled paper, which is recycled paper, has been further reused, and since the pulp fiber is being reused repeatedly, the resulting recycled paper pulp has many fine fibers. The strength is also reduced. Adding high amounts of this waste paper reduces the strength and opacity of newspapers, lowers the back-through and concealment during printing, and reduces the appearance of the printed surface, such as fading and missing halftone dots. Inconvenience arises.

  In order to improve the concealing property of newsprint and reduce back-through, it is common practice to improve the opacity and oil absorption of paper using fillers such as white carbon and calcium carbonate. . Methods for adding the filler include an external addition in which a filler is surface-coated with a binder and the like, and an internal addition in which the filler is mixed with a pulp raw material to make paper. Among the fillers, fine filler particles have good light scattering coefficient and absorption coefficient and high opacity improvement effect, but when used as an internal filler, the yield is low, and it is mainly applied by external addition. The However, when the filler is externally applied and used, it is necessary to form a coating layer of a certain level or more, and thus the weight reduction required for newsprint cannot be achieved. In addition, newsprint web offset presses do not have a drying facility at high speed, so when externally applying fillers, the quality required for newsprint is improved in terms of ink drying, surface strength, plate stains, etc. It is difficult to be satisfied.

  Therefore, as a paper using an internal filler for improving the opacity, for example, a technology for producing newsprint paper using white carbon in combination with talc, clay or kaolin has been proposed (see Japanese Patent No. 2960001). . The white carbon used in this newsprint is a fine one obtained by neutralizing sodium silicate with sulfuric acid, and its particle size is smaller than that of conventional white carbon particles, so it has good light scattering and white paper opacity. Can be improved. However, the white carbon according to this technique has a fine shape, and it is necessary to agglomerate with a sulfuric acid band or the like when used. Therefore, there is an inconvenience that quality control during operation is difficult.

  In addition, as another technique, there has been proposed a newsprint that mainly contains white carbon and calcium carbonate, and contains them in a ratio of 9: 1 to 5: 5 in the atomic absorption analysis of ash ( Japanese Patent Laid-Open No. 2002-201590). This newsprint can be manufactured at low cost by using inexpensive calcium carbonate and processing at pH 6 to 8 with a good white carbon yield. However, although the production cost of this newspaper can be reduced, there are many voids between the white carbon particles that have become large due to secondary aggregation and between the white carbon particles and the pulp fibers, and light is transmitted through these voids. Therefore, it cannot be said that the effect of improving opacity and whiteness is sufficient.

  In addition to these, in the prior art, there is a disadvantage that satisfactory opacity cannot be obtained and the yield of the filler is poor due to the fact that the adhesiveness between the fillers is not high. Furthermore, since the conventional fillers that are not high in stickiness are easily spilled from the paper after paper making, the inside of the machine system is soiled, and furthermore, the operability of the machine is lowered due to the spilled particles. There is.

Japanese Patent No. 2960001 JP 2002-201590 A

  The present invention has been made in view of these inconveniences, and by using an internal filler, it has high filler fixing property between pulp fibers, has high opacity and oil absorption, and generates paper dust during printing. The purpose of the present invention is to provide newsprint paper that can reduce the contamination in the machine system in the manufacturing process and improve the machine operability because it has less printability and excellent paper workability.

Newsprint with at least two types of fillers added to pulp,
As these two kinds of fillers, white carbon and silica-containing particles are used,
The total of these two kinds of fillers is characterized by having an area particle size distribution having a maximum value in each of the following ranges (A) and (B) in the distribution of the area particle size counted every 0.5 μm. Newspaper.
(A) 15 μm to 25 μm (B) 1 μm to 15 μm

  In the newspaper, white carbon and silica-containing particles are used as fillers internally added, and these two types of fillers have maximum values of 15 μm to 25 μm and 1 μm to 15 μm in area particle size distribution. It is what you have. In this way, in the distribution of the area particle diameter of two kinds of fillers containing silica (white carbon and silica-containing particles), when using fillers having maximum values in the respective ranges of 15 μm to 25 μm and 1 μm to 15 μm, A filler having a small particle size is combined with a gap between fillers having a large particle size. This combination provides newspaper with high opacity. That is, the particles having a small particle size are extremely high because the particles having a large particle size cannot be fixed, and are fixed so as to fill the mesh formed by the pulp fibers and the particles having a large particle size. It will have opacity. Furthermore, the use of a filler that increases the sticking property in this way reduces paper dust fall, thereby reducing dirt in the machine system in the manufacturing process and improving machine operability. it can. In addition, the newsprint can exhibit extremely high oil absorbency by including silica-containing particles in addition to white carbon as an internally added filler.

  The silica-containing particles may be silica-coated regenerated particles in which silica is coated on the surface of regenerated particles mainly made of deinked floss. Since the surface of the silica-coated regenerated particles has a porous shape, the newspaper can exhibit an extremely high oil absorption function, and in addition, the opacity can be further increased due to its high light scattering property. In addition, the silica-containing particles can use the regenerated particles whose main raw material is deinking floss as a core, thereby reducing the manufacturing cost.

  The content of the silica-coated regenerated particles is preferably 0.5% by mass or more and 4% by mass or less. According to the newsprint, when the content of the silica-containing particles is in the above range, the white carbon can be effectively fixed between the gaps that could not be filled, and can have extremely high opacity, so that the paper dust drops. Can be reduced.

  The ash content is preferably 8% by mass or more and 13% by mass or less. When the ash content is in the above range, the opacity and oil absorption of the newsprint can be further increased.

Since the newsprint has high opacity, excellent oil absorption, and high papermaking workability as described above, the basis weight is 38 g / m ^{2 to} 48 g / m ² and the whiteness is 52%. By setting the opacity to 57% or less and the opacity to 90% or more and 95% or less, it is possible to exhibit workability such as high opacity and printability as a newspaper for offset rotary printing.

  Here, “ash content” is a measurement value based on “paper, paperboard and pulp-ash content test method—525 ° C. combustion method” described in JIS-P8251. “Basis weight” is a measured value based on “Basis weight measuring method” described in JIS-P8124. “Whiteness” is a measured value based on “Measuring method of paper, paperboard and pulp-ISO whiteness (diffuse blue light reflectance)” described in JIS-P8148. "Opacity" is a measured value based on "Paper and paperboard-Opacity test method (backing of paper)-Diffuse illumination method" described in JIS-P8149. In addition, the “area particle diameter” in the present invention is a scanning electron microscope (model S-4800, manufactured by Hitachi High-Technologies Corporation, model ENERGY EX-250, Horiba, Ltd.) equipped with an energy dispersive X-ray analyzer. This is the diameter of the smallest circle (the circumscribed circle of particles) that can be included in the filler particles observed by photographing the newspaper paper surface at a magnification of 3000 times at a manufacturing company). In the case of secondary particles in which particles are aggregated, the diameter of the aggregated secondary particles is defined as the particle size. The average area particle diameter means an average of 100 area particle diameters randomly extracted from the particles observed with the scanning electron microscope. The total of the two types of filler particles containing silica (white carbon and silica-containing particles), that is, the maximum value of the area particle size distribution of the filler particles in which silica is detected by an energy dispersive X-ray analyzer is the energy dispersive X-ray Particles containing silica observed by scanning with a scanning electron microscope (model number S-4800, manufactured by Hitachi High-Technologies Corporation, model number ENERGY EX-250, Horiba Seisakusho) at a magnification of 3000 times with an analyzer Then, 100 particles are randomly extracted, and the number of filler particles is calculated for each area particle diameter of 0.5 μm to determine the area particle diameter distribution, and the presence or absence of the maximum value is determined.

  As described above, according to the newsprint of the present invention, even when an internal filler is used, the filler adherence between pulp fibers is high, and it has high opacity and oil absorption, and in addition, there is little paper dust falling. Therefore, it is possible to reduce contamination in the machine system during the manufacturing process and improve machine operability. Therefore, the newsprint of the present invention can be suitably used as a newsprint for high-speed offset rotary printing.

  Hereinafter, preferred embodiments of the newsprint of the present invention will be described.

  The newsprint of the present invention contains pulp and white carbon and silica-containing particles as at least two kinds of fillers.

  The pulp used as the raw material of the newsprint may be a known pulp, and the type and combination thereof can be set as appropriate. For example, virgin pulp can be used in addition to waste paper pulp and waste paper pulp as main components. Thus, it is preferable to use waste paper pulp as a main component from the viewpoint of resource saving.

  Waste paper pulp includes, for example, tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, leaflet waste paper, office waste paper, corrugated waste paper, Kamihiro waste paper, Kent waste paper, imitation waste paper, and old paper waste paper. Examples of such a paper include disaggregation / deinked waste paper pulp (DIP) and disaggregation / deinking / bleached waste paper pulp.

  Among these waste paper pulp, newspaper waste paper pulp derived from newspaper waste paper, magazine waste paper pulp derived from magazine waste paper, and the like are preferable, and it is particularly preferable to use a mixture of newspaper waste paper pulp and magazine waste paper pulp. Such waste paper pulp and magazine waste paper pulp has a high recovery rate of waste paper, and the paper pulp types and fillers that make up news paper and magazine paper are similar in each paper maker, thus suppressing fluctuations in the raw material composition. It is suitable at the point which can do. In particular, wastepaper pulp is generally used in newsprints because it is already 50% or more of wastepaper pulp and the content of virgin mechanical pulp and kraft pulp is low. Since it is once paper-made and used paper pulp by used paper processing, it is particularly preferable in that it has uniform properties and has almost constant properties.

  Examples of virgin pulp include hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), hardwood semibleached kraft pulp (LSBKP), Chemical pulp such as softwood semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp, etc .; Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (TGP), Chemi Grand Pulp (CGP), Ground Pulp (GP), Various well-known pulps such as mechanical pulps such as thermomechanical pulp (TMP); pulps chemically or mechanically produced from non-wood fibers such as kenaf, hemp, and straw can be used.

  Among these virgin pulps, in the production of newsprint, mechanical pulp (MP) having an effect of complementing the decrease in bulk due to the use of waste paper pulp is preferable, and thermomechanical pulp suitable for the adjustment of waste paper pulp obtained from waste paper ( TMP) is particularly preferred.

  The content of the used paper pulp in the raw material pulp is preferably 50% by mass or more, particularly preferably 70% by mass or more, and further preferably 80% by mass or more. By setting the content of the used paper pulp in the raw material pulp within the above range, environmental properties such as effective use of resources are improved, and printability such as ink inking properties is also improved. Conversely, the content of virgin pulp in the raw material pulp is preferably 20% by mass or more, and particularly preferably 30% by mass or more. If the content of the virgin pulp is less than the above range, it is difficult to adjust the waste paper pulp obtained from the waste paper, and the newspaper paper does not become bulky and has no waist, which may deteriorate the transportability and workability.

  The newsprint contains white carbon as a filler and silica-containing particles having an average area particle size smaller than the average area particle size of the white carbon. The total area particle size distribution of these two fillers containing silica is (A) 15 μm to 25 μm, preferably 18 μm to 22 μm, and (B) 1 μm to 15 μm, preferably 2 μm to 12 μm, Preferably, it has a maximum value in each range of 5 μm or more and 10 μm or less. In this example, the average area particle diameter of white carbon has a maximum value of (A), and the average area particle diameter of silica-containing particles has a maximum value of (B). Thus, the silica containing particle | grains which have an average particle diameter smaller than the average particle diameter of white carbon will be distributed by the space | gap which white carbon and a pulp fiber make. That is, the portion of the mesh structure created by the pulp fibers mutually, the gap between the white carbon and the pulp fibers, and the gap created by the white carbon can be defined as the gap, and light passes through the gap through the paper. It is considered that the opacity is lowered. Accordingly, the silica-containing particles are caught in such voids, and the voids are filled with the silica-containing particles, so that the opacity is improved.

  By adjusting the addition amount of these fillers, the ash content in the newsprint is adjusted. The lower limit of the ash content based on JIS-P8251 in the newspaper is preferably 8% by mass, and particularly preferably 10% by mass. Moreover, 13 mass% is preferable and the upper limit of ash content is especially preferable 12 mass%. When the ash content is in the above range, the newspaper can have high opacity. When the ash content is smaller than the above lower limit, the opacity is lowered. Conversely, when the ash content exceeds the upper limit, the opacity increases, but the adhesion between the pulp fibers decreases, leading to a decrease in paper strength.

  The ash content preferably contains 40% by mass to 60% by mass (oxide conversion) of silicon and 20% by mass to 40% by mass (oxide conversion) of calcium. In the newspaper, the ash content is mainly adjusted by the addition amount of white carbon as a filler and silica-containing particles. By containing silicon and calcium in the above range in the ash content, ink adsorbability suitable for rotary printing is exhibited, and high opacity can be realized. When the content of silicon and calcium is less than the above range, ink adsorbability and opacity are lowered. In addition, this ash-containing element is a value measured by analyzing 0.2 g of ash with an energy dispersive X-ray analyzer (model number ENERGY EX-250, HORIBA, Ltd.) (50 times). is there.

  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 oil absorption according to JIS-K5101-13-1 is preferably 190 to 230 ml / 100 g.

  The lower limit of the average area particle diameter of the white carbon is 15 μm, and preferably 18 μm. Further, the upper limit of the average area particle diameter of the white carbon is 25 μm, and preferably 22 μm. The primary particle diameter of white carbon is smaller than the above average particle diameter (for example, about 0.01 μm or more and 0.05 μm or less), but usually aggregates in a higher order to form secondary particles. The average area particle diameter of white carbon in the present invention also refers to the average area particle diameter of the aggregated secondary particles.

  If the average area particle size of the white carbon is smaller than the above lower limit, the size of the mesh structure formed by the pulp fibers becomes smaller, so the proportion of particles passing through this part increases, and the fixation rate decreases. To do. Conversely, if the average area particle size of the white carbon exceeds the above upper limit, it becomes larger than the mesh size of the mesh structure created by the pulp fibers, so it is difficult to enter and fix this part. .

  The lower limit of the amount of white carbon added is preferably 1% by mass and particularly preferably 1.5% by mass with respect to the raw material pulp. On the other hand, the upper limit of the amount of white carbon added is preferably 4% by mass, and particularly preferably 3% by mass. As a minimum of content of white carbon, 0.5 mass% is preferred and 1 mass% is especially preferred. On the other hand, the upper limit of the white carbon content is preferably 3% by mass, and particularly preferably 2% by mass. If the white carbon content is smaller than the above lower limit, the generated voids are too large and too large, so that the voids cannot be filled with silica-containing particles, and the function of improving opacity is low. Conversely, if the white carbon content exceeds the above upper limit, the amount of white carbon is too large for the size of the voids formed between the pulp fibers, so that it cannot be reliably embedded between the voids. There is a risk that more filler will fall off during production and use. Moreover, when there is too much content of white carbon, the strength between pulp fibers will fall and paper strength will fall.

  The silica-containing particles used in the present invention have an average area particle size smaller than that of the above-mentioned white carbon. Since silica has a porous shape and has high oil absorption, when used together with white carbon, the opacity of the newspaper can be increased and the oil absorption can be increased to exhibit excellent printability.

  The upper limit of the average area particle diameter of the silica-containing particles is 15 μm, preferably 12 μm, and particularly preferably 10 μm. The lower limit of the average area particle diameter of the silica-containing particles is 1 μm, preferably 2 μm, and particularly preferably 5 μm. When the silica-containing particles have an average area particle diameter in the above range, the silica-containing particles can enter and adhere to voids formed by pulp fibers and white carbon particles. Therefore, according to the newspaper, high opacity can be provided. In addition, the use of silica-containing particles having such a particle size increases the adhesion to the voids, so that the particles once fixed in the production process can be spilled, that is, the amount of paper powder can be reduced, and thus produced. It is possible to reduce contamination in the machine system in the process and improve machine operability.

  If the average area particle size of the silica-containing particles exceeds the above upper limit, the particle size is too large for the voids, so that it cannot enter the voids, resulting in a decrease in stickiness, and thus an improvement in opacity. Does not contribute. On the contrary, if the average area particle diameter of the silica-containing particles is smaller than the lower limit, the particle diameter is too small with respect to the voids, so that the particles easily pass through the voids, and the fixing property is lowered. In addition, when the particle diameter is small in this way, the light scattering action is small even if the particle size is fixed, so that the contribution to the improvement of opacity is small. Furthermore, since the strength is weak and easy to fall even if it is fixed, the rate of dropout in the manufacturing process increases, and dirt in the machine system in the manufacturing process is generated, thereby reducing machine operability.

  The lower limit of the amount of silica-containing particles added is preferably 0.5% by mass, particularly preferably 1.5% by mass, and more preferably 2% by mass with respect to the raw material pulp. Moreover, as an upper limit of the addition amount of a silica containing particle, 5 mass% is preferable, 4 mass% is especially preferable, and 3 mass% is more preferable. As a minimum of content of silica content particles, 0.5 mass% is preferred, 1 mass% is especially preferred, and 1.5 mass% is still more preferred. Moreover, as an upper limit of content of a silica containing particle, 4 mass% is preferable, 3 mass% is especially preferable, and 2.5 mass% is still more preferable. When the content of the silica-containing particles is smaller than the above lower limit, the generated voids cannot be filled, and the function of improving opacity cannot be sufficiently exhibited. On the contrary, when the content of the silica-containing particles exceeds the above upper limit, the content is too much with respect to the volume of the generated voids, so that the solid fixation cannot be performed and the filler is dropped off. Furthermore, the increase in filler weakens the adhesion between pulp fibers, and as a result, the strength of the newsprint decreases.

  As the silica-containing particles, silica particles, particles in which silica particles and other particles are aggregated, or particles in which other particles are coated with silica are used, and white carbon may be used. From the standpoints of mutual adsorption with each other, light scattering properties, and reduction in production costs, particles coated with silica are preferable, and the surface of regenerated particles mainly composed of silica-coated calcium carbonate particles or deinked floss The silica-coated regenerated particles are preferably coated with silica.

  When silica-coated calcium carbonate particles are used, the base calcium carbonate particles are produced by, for example, heavy calcium carbonate (GCC) obtained by grinding limestone, or by a chemical method such as a carbon dioxide method or a carbonate solution method. Light calcium carbonate (PCC) can be preferably used.

  The silica particles used for coating the calcium carbonate particles include those produced from colloidal silica and hydrous silicic acid produced by neutralization of sodium silicate, and those having an average particle size of 20 nm to 500 nm. Preferably used. The silica particles coated on the surface of the calcium carbonate particles so that the mass of the silica particles is 1 and the calcium carbonate mass is 2.5 to 4.0 is preferably used. Examples of the method for producing the calcium carbonate particles coated with silica include a method in which a mineral acid is dropped into a sodium silicate aqueous solution in which the calcium carbonate particles are suspended to deposit hydrous silicic acid on the surface of the calcium carbonate particles. There is.

  Next, regenerated particles coated with silica that are suitably used as silica-containing particles will be described. Such regenerated particles are obtained by using deinked floss as a main raw material and passing through a dehydration step, a drying step, a firing step, and a pulverization step. Furthermore, as will be described later, a deinking floss aggregation process, a granulation process, a classification process provided between the processes, and the like may be performed. In addition, it is desirable to provide various sensors in the production facility for regenerated particles to control the state of the object to be processed and the equipment, the processing speed, and the like. At least regenerated particles containing specific amounts of calcium, silicon and aluminum obtained through the above steps are used.

  The regenerated particles using deinking floss as a main raw material are mainly made of deinking floss generated in a deinking process for producing waste paper pulp from used paper. Particularly, deinking floss discharged in the recycling process of waste paper is preferable because it is made of a material derived from papermaking raw materials and contains less impurities such as iron and other heavy metals. And in the used paper recycling process, since the used paper itself is selected in advance, the deinking floss has a stable composition over time of its inorganic matter, and thus the composition of the resulting recycled particle aggregate is also stable. Become. These deinking froths contain calcium carbonate, kaolin, talc, titanium dioxide, silica, alumina and the like as inorganic substances.

  Usually, the deinking floss has a moisture content of about 95 to 98% by mass, and a floc is formed by adding a flocculant to perform dehydration. The dehydration process can be carried out in one or more stages, but if the floc is solidified, it causes carbonization unevenness in the subsequent carbonization process. Therefore, the moisture content is preferably 25 to 45% by mass in a plurality of stages. It is preferable to dehydrate to about 30 to 40% by mass. If the moisture content is less than the above lower limit, the dehydration energy cost increases.On the other hand, if the moisture content exceeds the upper limit, the drying energy cost in the drying means in the next step increases, resulting in variations in the particle size after drying. As a result, uniform firing becomes difficult.

  The dehydrated product is dried in advance. As the drying means, known drying means such as hot air drying can be used, but hot air drying means which can be loosened while drying the deinking floss and further can be classified by specific gravity can be most preferably used.

  A specific example of a hot air drying means that can be suitably used is a hot air blower provided below the impeller equipment while loosening the deinked deinking floss with a loosening equipment such as an impeller so that the volume average particle diameter is about 355 to 2000 μm. Hot air drying is performed by blowing hot air by means. Of the deinked floss that has been loosened and dried, the deinked floss having a low specific gravity is discharged from the outlet provided in the upper part of the hot air drying means, whereby drying and classification can be performed.

  As a suitable means for classification of the deinked floss that has been dried, classification by a cyclone can be employed. The deinked floss that has been dried and classified has a similar shape to the regenerated particle aggregate that has already been finally obtained.

  The deinked floss that has been dried and classified is sent to the firing process. For firing, for example, a commonly used incinerator such as a rotary kiln, a fluidized bed furnace, a floating furnace, a stoker furnace, etc. can be used, and a combustion method by indirect heating using a hot air furnace or an electric furnace is particularly preferred. Fine adjustment of the degree of firing is easy. The firing temperature is not particularly limited as long as it is sufficiently stable and stable to burn ink pigments such as carbon black in sludge and organic compounds such as fibers and polymers.

  When silica is contained in the deinking floss, there is a possibility that silica reacts with calcium and aluminum to produce aluminum calcium silicate having high hardness. In order to prevent the formation of a substance with high hardness, for example, baking at a temperature of 500 ° C. or less is considered. However, under such conditions, it is difficult to completely burn the organic compound, and it is useful for papermaking. Silica-coated regenerated particles with a possible level of whiteness cannot be obtained.

  On the other hand, when the firing temperature exceeds 1000 ° C., the decomposition and sintering of inorganic substances such as calcium carbonate, kaolin, talc, titanium dioxide, silica, and alumina contained in the deinking floss progresses and the hardness is increased. In addition, it is not preferable because regenerated particles mainly composed of deinked floss may be required to take a great deal of energy and time to be pulverized to the desired particle size in the present invention. Therefore, as firing conditions, primary firing is preferably performed at 510 to 750 ° C., secondary firing is preferably performed at 500 to 700 ° C., primary firing is performed at 520 to 650 ° C., and secondary firing is performed at 500 to 600 ° C. More preferably.

  The firing process can be performed in one step, but is preferably at least two steps, and more preferably at least two steps by continuous equipment. If the firing process is composed of at least two stages of firing, firing unevenness is less likely to occur in firing by burning organic matter, and firing can be performed evenly. In particular, by varying the physical means in the firing step, it is possible to avoid uneven firing and improve the firing rate.

  The firing temperature has a great influence on the whiteness and hardness of the regenerated particles to be produced. When the primary firing temperature is less than 510 ° C., the remaining amount of unburned material is large, and the whiteness of the obtained regenerated particles is 70%. It doesn't reach above. On the other hand, when the primary firing temperature exceeds 750 ° C., most of the calcium carbonate contained in the deinking floss is thermally decomposed, and many substances causing high pH such as calcium oxide and calcium silicate are generated which are difficult to use as resources. In addition, there is a possibility that the obtained regenerated particles are melted by heat and are extremely hard and have poor wire wear properties. On the other hand, when the secondary firing temperature is less than 500 ° C., the organic matter is not sufficiently combusted, or the combustion is uneven and the whiteness of the produced regenerated particles is not increased. On the other hand, if the secondary calcination exceeds 700 ° C., the problem is that the surface of the regenerated particles that have been carbonized and calcined is melted due to exposure to a high temperature, forming a very hard melt, Therefore, it is difficult for oxygen to reach the regenerated particle core, and there are concerns about occurrence of uneven combustion and unburned sites. Moreover, by making the temperature of the secondary firing 10-50 ° C. lower than the temperature of the primary firing, the unburned material can be burned while preventing overfire of the surface of the regenerated particles. Of course, the temperature of the secondary firing can be the same as the temperature of the primary firing. In the case of the same temperature, if it is set to 520 to 600 ° C., the firing can be performed slowly and the unburned material can be reduced. Regenerated particles having a degree of at least 70% or more, preferably more than 80% can be obtained. In this embodiment, the temperature difference between the primary firing temperature and the secondary firing temperature is based on the temperature at the upper end in the firing furnace.

  In the baking process, the oxygen concentration in the process is 0.05% or more, preferably 0.05 to 20 by at least one of the means for blowing air in the process and the means for exhausting air from the process. %, More preferably 5 to 15% at the upper end in the primary firing furnace, more preferably 7 to 13%, and 10 to 20%, more preferably 12 to 18% in the vicinity of the burner of the secondary firing furnace. When the oxygen concentration in the primary firing furnace is less than 0.05%, firing does not proceed and not only uneven firing proceeds, but also enormous time and energy costs are required for firing. On the other hand, when the oxygen concentration in the secondary baking furnace exceeds 20%, the paper is easily overfired, and the regenerated particles are yellowed due to overheating unevenness, and the regenerated particles are frequently melted, and the decomposition and oxidation of the regenerated particles progresses. Use as a filler may be difficult. In the present embodiment, the moisture content of the dried and classified deinked floss (dried product) supplied to the firing step is adjusted to at least 2 to 20% by mass, more preferably 5 to 15% by mass. Therefore, when the oxygen concentration in the firing step is 0.05 to 20%, firing can be performed very efficiently, firing can be performed within 90 minutes, and extremely high productivity can be obtained. . For example, baking can be performed in about 60 minutes by setting the moisture content of the dried product to 10% by mass.

  In this regard, oxygen in the firing process is consumed by a burner or the like for firing, and the oxygen concentration decreases. However, the oxygen concentration can be maintained and adjusted by blowing or exhausting an oxygen-containing gas such as air. Furthermore, by blowing or exhausting oxygen-containing gas, the temperature in the firing process can be finely adjusted, and the regenerated particles can be fired uniformly without unevenness.

  Firing in the primary firing furnace is performed so that the unburned rate becomes 5 to 30% by mass. It is more preferable to carry out so that it may become 8-25 mass%, and it is especially preferable to carry out so that it may become 10-20 mass%. When the unburned ratio in the primary firing is less than 5 mass percent, over-burning of the particle surface in firing occurs, the surface becomes hard, oxygen deficiency inside occurs, and the whiteness of the regenerated particles decreases. On the other hand, if the unburned ratio in the primary firing exceeds 30% by mass, there will be a problem that unburned matter will remain even after the subsequent burning and firing, a problem that the unburned matter will be cured by over-baking due to self-combustion, unburned matter In order to prevent the remaining of the particles, the surface of the particles is burnt and fired until it is overfired, resulting in a problem that the surface of the regenerated particles becomes hard.

  In the regenerated particle manufacturing facility, it is preferable to remove in advance foreign substances other than the raw material of the regenerated particles, for example, sand with a pulper, screen, cleaner, etc. in the previous stage leading to the deinking process of the used paper pulp manufacturing process, It is preferable in terms of removal efficiency to remove foreign matters such as plastic and metal. In particular, the iron content is preferably selectively removed while avoiding the mixing of iron content because a substance causing a decrease in the whiteness of the regenerated particles is generated by oxidation. Therefore, each process is designed or lined with materials other than iron to prevent iron from being mixed into the system due to wear, etc., and a high magnetic material such as a magnet is installed in the drying / classifying equipment, etc. In particular, it is preferable to remove iron.

  In the present embodiment, in the drying step, the firing step, and the classification step as necessary, particles having a particle size of 40 μm or less are 80% by mass or more, more preferably 90% or more in advance before the pulverization step. It is preferable to process in this way. Accordingly, a single-stage pulverization process by wet pulverization can be performed without performing a multistage pulverization process such as pulverization of coarse particles by dry pulverization and fine particle formation by wet pulverization.

In addition, by adjusting calcium, silicon and aluminum in the deinking floss as a raw material in advance to a mass ratio described below, for example, the pore volume of the regenerated particles is 0.15 to 0.60 cc / g, and the pore surface area is 10 to 25 m ² / g, pore radius can be 30 to 100 nm, and regenerated particles excellent in oil absorption and opacity can be obtained.

  In order to make the particle size of the regenerated particles uniform in each step, classification is preferably performed, and the quality can be further stabilized by feeding back coarse particles and fine particles to the previous step. In addition, it is preferable to granulate the deinked floss that has been dehydrated in the previous stage of the drying process, and more preferably to classify the granulated product uniformly so that coarse or fine particles are formed. The quality can be further stabilized by feeding back the grains to the previous process. In granulation, ordinary granulation equipment can be used, and equipment such as a rotary type, a stirring type, and an extrusion type is preferable.

  These recycled particles can be recycled and used by firing deinked floss, so there is no need to dispose of landfills as waste, contributing greatly to reducing environmental impact and saving resources. Is. Further, since the raw material is deinking floss generated in the waste paper processing step, there is an advantage that it is inexpensive, the amount of new regenerated particles used can be suppressed, and the manufacturing cost is sufficiently reduced. Furthermore, by using such regenerated particles, the yield of ash during paper making is high, and unlike calcium carbonate, for example, there is no wear deterioration of paper making equipment such as wire wear, and the resin component becomes fine particles under fine conditions. Adsorption prevents pitch troubles due to resin agglomeration, hardly causes contamination of printing equipment, makes it possible to produce paper at low cost and high operability, and has excellent opacity that is equal to or better than conventional ones. Paper strength is imparted to the paper, resulting in less breakthrough and breakage.

  The silica covering the surface of the regenerated particles can be used without particular limitation as long as it is not naturally produced silica but synthetic silica by some chemical reaction. Specific examples include colloidal silica, silica gel, and anhydrous silica. These synthetic silicas make use of excellent properties such as high specific surface area, high gas adsorbing capacity, fineness, permeability to pores and large adsorbing power, high adhesion, and high oil absorption. It is used in a wide range of fields. Among these, colloidal silica has a shape such as a spherical shape, a chain shape, and an amorphous shape, in which impurities are removed from a silicic acid compound to form an anhydrous silicic acid sol, and the sol is stabilized by adjusting pH and concentration. Amorphous silica. Silica gel is hydrous silicic acid obtained by decomposing sodium silicate with an inorganic acid. Anhydrous silica is obtained by hydrolysis of silicon tetrachloride.

  The method for depositing silica on the surface of the regenerated particles to obtain silica-coated regenerated particles is not particularly limited. For example, the following method can be suitably employed. First, regenerated particles are added and dispersed in an alkali silicate solution, and after preparing a slurry, while heating and stirring, an acid is added while maintaining the liquid temperature at about 70 to 100 ° C. to produce a silica sol. Subsequently, silica can be deposited on the surface of the regenerated particles by adjusting the pH of the final reaction solution to a range of 8 to 13. Silica precipitated on the surface of the regenerated particles in this way, using alkali silicate (for example, sodium silicate: water glass) as a raw material, reacts with a dilute solution of mineral acid such as sulfuric acid, hydrochloric acid, nitric acid at high temperature, Silica sol particles having a particle size of about 10 to 20 nm, obtained by hydrolysis reaction and polymerization of silicic acid.

  In addition, silica sol fine particles having a particle size of about several nanometers, which are generated by adding an acid such as dilute sulfuric acid to an alkali silicate solution such as a sodium silicate solution, cover the entire porous surface of the regenerated particles. The silica is deposited on the surface of the regenerated particles due to the bond between the silica sol fine particles on the surface of the inorganic fine particles and the silicon, calcium, or aluminum included in the regenerated particles accompanying the crystal growth of the silica sol fine particles. You can also. In this case, the pH when adding the acid to the alkali silicate solution is in a neutral to weakly alkaline range, and the pH is preferably adjusted in the range of 8 to 13. This is because if the acid is added until the pH reaches an acidic condition of less than 7, white carbon may be generated instead of silica sol particles.

The type of the alkali silicate solution is not particularly limited, but a sodium silicate solution (No. 3 water glass) is particularly desirable from the viewpoint of easy availability. The concentration of the alkali silicate solution is such that the silica component in the regenerated particles is reduced and the silica content (SiO ₂ equivalent) in the solution is 3 in order to prevent the silica from becoming difficult to precipitate on the surface of the regenerated particles. The silica deposited on the surface of the regenerated particles is preferably white carbon from the form of the silica sol, impairing the porosity of the regenerated particles and insufficiently improving the opacity and toner fixability. In order to eliminate the risk of becoming, it is preferable that the silicic acid content (in terms of SiO ₂ ) is 10% by mass or less.

  By using the silica-coated regenerated particles, it is possible to react with sodium hydroxide in the used paper processing step in circulation use, and to contribute to the recycle use of the raw material for papermaking and regenerated particles as a buffer or bleaching aid. Further, when such silica-coated regenerated particles are internally added to the raw material pulp as a filler, the paper whiteness, opacity, surface strength, ink drying property, and more than when using regenerated particles not coated with silica, Effects such as ink absorption unevenness and bulkiness can be further improved.

  The deinking floss produced in the used paper processing step used in the present embodiment has a tendency to increase the content of calcium carbonate with the recent neutral paper making, and the ratio of calcium in the obtained regenerated particles is also high. Tend to be. When regenerated particles with a high calcium content are added to the raw material pulp in this way, the opacity of the paper may be slightly reduced, but the silica-coated regenerated particles with silica precipitated on the surface are used as regenerated particles for papermaking. The opacity of the paper obtained by internally adding the silica-coated regenerated particles to the raw pulp is remarkably improved.

  The silica-coated regenerated particles thus obtained contain calcium, silicon and aluminum. The ratio of these calcium, silicon, and aluminum in the regenerated particles is analyzed by elemental analysis using an X-ray microanalyzer (model number: E-MAX S-2150, manufactured by Hitachi, Ltd./Horiba, Ltd.) and oxidized. It is preferable that calcium, silicon, and aluminum have a mass ratio of 10 to 80:10 to 80: 5 to 29 in terms of oxide in terms of physical properties. At the same time, the total content in terms of oxides in the elemental analysis of calcium, silicon and aluminum is 90% by mass or more, preferably 93% by mass or more. Thus, when the regenerated particle | grains made into 10 mass ratio or more in oxide conversion are internally added to raw material pulp as a filler, the whiteness of the paper obtained especially can be improved.

  In order to adjust the ratio of calcium, silicon, and aluminum in the silica-coated regenerated particles within the above range, for example, in terms of oxide, it is originally preferable to adjust the raw material composition in the deinking floss, but the drying step and the firing step Further, if necessary, in the classification step, it is also possible to employ a method in which a coating floss having a clear origin or an adjustment step floss is contained by spraying or a method in which incinerator scrubber lime is contained.

  For example, neutral papermaking wastewater sludge and coated paper manufacturing wastewater sludge are used to adjust calcium in recycled particles, and newspaper manufacturing systems that are added in large quantities as opacity improvers are used to adjust silicon. For the adjustment of aluminum, a papermaking drainage sludge using an acid papermaking sulfuric acid band or the like, and a drainage sludge from a high quality papermaking process in which a large amount of clay is used can be appropriately used.

  Furthermore, since the silica-coated regenerated particles used in this embodiment have a flexible and porous property in which fine particles are aggregated, the silica-coated regenerated particles contribute to the formation of a bulky paper layer, and the silica-coated regenerated particles are internally added to the raw material pulp as a filler. The newsprint obtained in this way has a high filler yield, low density, and good stiffness.

  In addition, as an additive to be added to the stock slurry obtained from the raw pulp and filler, those added to ordinary newsprint can be used, for example, paper strength enhancers such as starches, polyacrylamide, epichlorohydrin, Examples thereof include internal sizing agents such as rosin, alkyl ketene dimer, ASA (alkenyl succinic anhydride) and neutral rosin, coagulants such as sulfuric acid band and polyethyleneimine, and coagulants such as polyacrylamide and copolymers thereof.

  Furthermore, it is preferable that a surface treatment agent containing at least starch as a main component is applied to the front and back surfaces of newsprint paper after paper stock slurry is prepared from raw pulp to make paper. Examples of starch include oxidized starch and modified starch, and other examples include PVA (polyvinyl alcohol) and polyacrylamide, which can be used alone or simultaneously. As a result, the vehicle of cold-set offset ink is quickly absorbed, and even if the amount of printing ink increases due to the speedup of a rotary press or the use of a tower press for double-sided color, sufficient absorption and drying properties are exhibited. Since the filler is securely fixed to the fiber, it is possible to prevent the filler from falling off and to ensure excellent printing opacity, printability and the like.

  The type of the starch is not particularly limited. For example, the modified starch has an effect of improving tensile strength and surface strength while penetrating into paper, but exhibits neutrality or anionic property. The fixability to the pulp fiber surface to be exhibited is low, and the film 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 film 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 starch, high amylose-containing corn starch, wheat starch And starch-containing materials such as tapioca starch, corn flour, and rice flour are treated with oxidized and acid-treated starch. Among these, tapioca starch is preferable in that the ester-modified product is superior to other cereal starches in terms of viscosity, film property, elasticity, and extensibility.

  In addition, as the oxidized starch used in the present invention, conventionally used modified starch is preferably exemplified, for example, by oxidation reaction with sodium hypochlorite or the like, low molecular weight, carboxyl group in the molecule, Examples include those in which an aldehyde group, a carbonyl group or the like has been introduced.

In addition, as an average molecular weight of these starches, 600,000-3 million are preferable and 800,000-2,800,000 are especially preferable. The starch having such an average molecular weight improves the absorption and drying property by incorporating the solvent component into the paper while keeping the ink component on the paper surface, in addition to the improvement in size. The viscosity of the starch (10%), preferably not more than 30 × ¹⁰ -3 Pa · s, particularly preferably ^{15 × 10 -3 ~25 × 10 -3} Pa · s. Since starches having such a viscosity are high in viscosity, they do not penetrate into the paper and can remain on the paper surface, improve the fixing property of the filler, and prevent the filler from falling off.

  Various auxiliary agents such as an antifoaming agent, a water resistant agent, a surface sizing agent, and a preservative can be appropriately added to the surface treatment agent. In order to further improve the sizing property, a surface sizing agent is preferably applied. As the surface sizing agent, known ones are used, and for example, styrene-based sizing agent, olefin-based sizing agent, alkyl ketene dimer, alkenyl succinic anhydride, rosin and the like can be used. Styrenic sizing agents are preferred from the viewpoint of compatibility with ink in rotary printing and the effect of preventing the filler from falling off.

  As the styrene-based sizing agent, styrene / acrylic acid copolymer, styrene / (meth) acrylic acid copolymer (note that (meth) acrylic acid means “acrylic acid and / or methacrylic acid”). Styrene / (meth) acrylic acid / (meth) acrylic acid ester copolymer, styrene / maleic acid copolymer, styrene / maleic acid half ester copolymer, styrene / maleic acid ester copolymer, etc. .

  The surface treatment agent is a coating apparatus commonly used in the papermaking field, for example, a size press, a blade metering size press, a rod metalling size press, a blade coater, a bar coater, a gate roll coater, a rod coater, an air knife coater or the like. And apply.

In order to sufficiently improve the surface strength of the paper, the coating amount of the surface treatment agent is 0.1 to 2.0 g / m ² , and further 0.3 to 1 in terms of dry mass per side on the front and back of the newspaper. It is preferably applied in an amount of 0.5 g / m ² . If it is less than 0.1 g / m ² , it will be difficult to obtain sufficient film properties with starch, PVA, etc., and sufficient paper surface strength will not be obtained. On the other hand, if it exceeds 2.0 g / m ² , a large amount of mist of a surface treatment agent such as starch or PVA is generated around the coating equipment, and the peripheral equipment may be soiled, and paper breakage or paper defects may occur due to the dirt. There is. The coating amount of the surface sizing agent is preferably adjusted to be 0.03 g / m ² or more in terms of dry mass in order to sufficiently improve the paper size and surface strength. In order not to cause a decrease in opacity or ink drying property, the dry mass is adjusted to 0.7 g / m ² or less, more preferably 0.1 to 0.5 g / m ² or less. It is preferable to do.

  The stock prepared from the stock slurry and, if necessary, the additive can be made by a known paper machine, and further passed through a calender device as necessary, subjected to pressure and smoothing treatment. Can be finished in newsprint.

  As the calendar device, from a machine calendar by a combination of metal rolls, a metal roll, and a roll imparted with elasticity such as a roll covered with a highly durable resin material such as a woolen paper roll or a polyamide resin. A so-called soft calendar is known, and a machine calendar using a combination of a metal roll and a metal roll is generally used.

  However, if smoothening is achieved by increasing the nip pressure in the calendar process or increasing the number of nips, the ink fillability will increase, but the bulkiness of the paper will be impaired. There is a possibility of causing trouble, and the opacity after printing is lowered and the rigidity is lowered.

  On the other hand, if the calendar process is reduced, a bulky paper can be obtained, but the difference in front and back of the paper surface is increased. There arises a problem that the density of the image is significantly different between the back side and the back side. This is because the dehydration conditions in the wire part and press part are slightly different between the front and back sides during the paper making process, so there is a difference in the smoothness of the paper, and the distribution of filler and fine fibers in the thickness direction. This is considered to be because the transferability of the ink has a difference between the front and the back.

  In particular, in recent years, with the colorization and weight reduction of newsprint, there has been a further demand for good ink fillability and high opacity after printing. In the present invention, a soft calender is preferably used.

  When a machine calendar is used in a suitable combination with newsprint when regenerated particles are internally added as a filler, there is a tendency to promote the difference between the smoothness and the smoothness generated in the process up to drying before applying the surface treatment agent. On the other hand, when combined with a soft calendar, density unevenness after calendering due to uneven formation of the paper layer can be reduced, and as a result, printing with a uniform density without ink absorption unevenness when color printing is performed during offset printing. The surface can be obtained, especially in the combined use with recycled particles, and by using a soft calendar that reduces irregularities so that the surface of the paper is flattened with a high-temperature iron without increasing the density and the recycled particles originally having cushioning properties, Recycled particles tend to get entangled with the fibril fibers of the raw pulp, improving the flatness and denseness of the paper surface without increasing the density and reducing the paper strength. Pile. In addition, as a means for improving ink fillability, it is possible to smooth newspaper paper by flattening with a soft calender or the like as described above, and to smooth the paper layer without strongly pressing, It is more preferable to use a soft calender because a decrease in paper layer strength can be sufficiently suppressed.

  On the other hand, the hardness of the elastic roll of the soft calendar is preferably 87 to 95 ° in Shore hardness according to JIS-Z2246. If it is less than 87 °, the durability of the elastic roll is poor and sufficient smoothness cannot be obtained. On the other hand, if it exceeds 95 °, there is a problem that it is difficult to obtain a uniform profile. As for the roughness of the elastic roll, it is particularly desirable that the maximum value of the surface roughness according to JIS-B 6001 is less than 0.5 μm in order to reduce ink unevenness on the paper surface.

  Moreover, in order to smooth the surface which touches the metal roll of the soft calender, the surface temperature of the metal roll is set to 40 to 150 ° C, preferably 80 to 140 ° C, and more preferably 90 to 120 ° C. By setting the surface temperature within this range, even in multi-color printing in which slight density unevenness affects, a printing surface with a uniform density can be made without any difference between the front and the back.

  In the use of the soft calendar, the flatness and bulkiness can be further improved by passing the paper so that the back side that contacts the wire side of the newsprint is in contact with the metal roll surface of the soft calendar first, In high-speed papermaking at 1500 m / min or more, it is possible to obtain newsprint with high flatness and little difference in front and back in color printing.

  More preferably, by increasing the coating amount of the surface sizing agent provided on the front and back surfaces on the back surface side than on the front surface side, better flatness and bulkiness can be obtained, and a firm newsprint can be obtained.

The basis weight of the newspaper is measured in accordance with the “basis weight measurement method” described in JIS-P8124 from the viewpoint of weight reduction, for example, ensuring the paper quality strength in high-speed rotary printing, ensuring the printing opacity, It is preferably 38 g / m ² or more, more preferably 40 g / m ² or more, and from the viewpoint of weight reduction, the basis weight is preferably 48 g / m ² or less, more preferably 46 g / m ² or less. If the basis weight is less than the above lower limit, for example, it is difficult to ensure the strength in a high-speed offset rotary printing press.

  The whiteness of the newspaper is in accordance with “Measuring method of paper, paperboard and pulp-ISO whiteness (diffuse blue light reflectance)” described in JIS-P8148 so as not to cause eye strain of subscribers. 52% to 57% is preferable, and 53% to 56% is particularly preferable.

  The opacity of the newspaper is required to be high because it is difficult to see through during printing, but was measured in accordance with “Paper Opacity Test Method” described in JIS-P8138. The lower limit is preferably 90%, particularly preferably 92%. Moreover, as an upper limit of opacity, 95% is preferable and 94% is especially preferable. If the opacity is less than the above lower limit, the show-through tends to occur. On the other hand, when the opacity exceeds the upper limit, the necessary filler is increased. As a result, the adhesion between the pulp fibers is lowered, and the strength of the newsprint is lowered.

  The newspaper uses at least white carbon and silica-containing particles as a filler, and the filler has an area particle diameter distribution of particles containing silica aggregated every 0.5 μm to 15 μm to 25 μm and 1 μm or more. By having an area particle size distribution having a maximum value in each range of 15 μm or less, silica-containing particles are combined in the gaps of white carbon, and the opacity can be 90% or more. Furthermore, the opacity can be increased by using silica-coated regenerated particles in which silica is coated on the surface of regenerated particles mainly made of deinked floss as silica-containing particles.

  The printing opacity of the newspaper is required to be high because it is difficult to show through during printing, but 90% is the lower limit measured in accordance with the printing opacity test method described later. Preferably, 91% is particularly preferable. The upper limit of opacity is preferably 94% and particularly preferably 93%. If the printing opacity is less than the above lower limit, show-through tends to occur. Conversely, if the printing opacity exceeds the above upper limit, the necessary fillers increase, resulting in a decrease in the adhesion between pulp fibers, the strength of the newsprint, or printing due to the loss of the filler from the paper surface. Not only the paper dust increases, but also dirt in the machine system in the manufacturing process increases and the operability deteriorates.

  The newspaper uses at least white carbon and silica-containing particles as a filler, and the filler has an area particle diameter distribution of particles containing silica aggregated every 0.5 μm to 15 μm to 25 μm and 1 μm or more. By having an area particle size distribution having a maximum value in each range of 15 μm or less, silica-containing particles are combined in the gaps of white carbon, and the printing opacity can be 90% or more. Furthermore, printing opacity can be increased by using silica-coated regenerated particles in which silica is coated on the surface of regenerated particles mainly composed of deinked floss as silica-containing particles.

Further, the density of newsprint is measured in accordance with “Paper and paperboard—Thickness and density test method” described in JIS-P8118 from the viewpoint of maintaining the strength associated with the recent weight reduction and weight reduction. It is preferably 50 to 0.80 g / cm ³ , more preferably 0.55 to 0.75 g / cm ³ .

In addition, the stiffness in the MD direction of the paper is measured in accordance with, for example, a stiffness test method using a paper Clark stiffness tester described in JIS-P8143 from the viewpoint of imparting a waist suitable for high-speed rotary printing, It is preferable that it is 30-55 cm < ³ > / 100, Furthermore, it is 32-50 cm < ³ > / 100.

  As described above, the newsprint of this embodiment includes silica-containing particles in addition to white carbon as an internally added filler, and therefore can exhibit extremely high oil absorbency. Further, the silica-containing particles can be fixed in the fine voids formed by the white carbon and the pulp fibers due to the relationship between the average area particle diameters of the silica-containing particles and the white carbon internally added to the newspaper. Accordingly, the newspaper has extremely high opacity because silica-containing particles having a small particle diameter and a high light scattering function are fixed so as to fill the gap. Furthermore, by using two kinds of fillers having high fixing properties in this way, dirt in the machine system in the manufacturing process is reduced and machine operability is improved.

  The newsprint of the present invention is not limited to the above embodiment, and for example, the average area particle diameter of white carbon may be smaller than the average area particle diameter of silica-containing particles. In this case, the average area particle diameter of white carbon is preferably 1 μm or more and 15 μm or less, and the average particle diameter of silica-containing particle diameters is preferably 15 μm or more and 25 μm or less. In newsprint with two kinds of fillers having such particle diameters internally added, white carbon having a small particle diameter is embedded in the voids of the mesh formed by the silica-containing particle diameter and the pulp fibers. Therefore, even with such newspapers, the opacity is increased and the two kinds of fillers have an appropriate size ratio and are fixed in the base paper, so that paper dust can be reduced.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1
80% by mass of disaggregated / deinked waste paper pulp (DIP) and 20% by mass of thermomechanical pulp (TMP), and 120 mL freeness with a refiner. S. A pulp slurry adjusted to F (based on JIS-P8121) was obtained. To this pulp slurry, white carbon (average area particle size 20 μm) is added at 20 kg / pulp ton, and silica-coated regenerated particles (average area particle size 8 μm) are added as silica-containing particles at 30 kg / pulp ton, and the pH is adjusted with a sulfate band. Thereafter, 0.07 part of a flocculant (Himolock ND270 manufactured by Hymo Co., Ltd.) was added per 100 parts by mass of the absolutely dry pulp, and newspaper paper having a basis weight of 42 g / m ² was made with a twin wire paper machine. Furthermore, the oxidized starch as a surface treatment agent was applied to both surfaces at a dry mass of 1.5 g / m ² to obtain the newspaper of Example 1. The silica-coated regenerated particles were produced according to Production Example 1 described in Examples of Japanese Patent Application Laid-Open No. 2008-111206.

(Example 2)
Newspaper paper of Example 2 was obtained in the same manner as in Example 1 except that the average area particle size of the silica-coated regenerated particles was 1 μm.

(Example 3)
Newspaper paper of Example 3 was obtained in the same manner as in Example 1 except that the average area particle diameter of the silica-coated regenerated particles was 2 μm.

Example 4
Newspaper paper of Example 4 was obtained in the same manner as Example 1 except that the average area particle diameter of the silica-coated regenerated particles was 5 μm.

(Example 5)
Newspaper paper of Example 5 was obtained in the same manner as in Example 1 except that the average area particle size of the silica-coated regenerated particles was 10 μm.

(Example 6)
Newspaper paper of Example 6 was obtained in the same manner as in Example 1 except that the average area particle size of the silica-coated regenerated particles was 12 μm.

(Example 7)
Newspaper paper of Example 7 was obtained in the same manner as in Example 1 except that the average area particle diameter of the silica-coated regenerated particles was 14 μm.

(Example 8)
Newspaper paper of Example 8 was obtained in the same manner as in Example 1 except that the amount of the silica-coated regenerated particles added was 10 kg / pulpton.

Example 9
Newspaper paper of Example 9 was obtained in the same manner as Example 1 except that the average area particle size of white carbon was 15 μm.

(Example 10)
Newspaper paper of Example 10 was obtained in the same manner as Example 1 except that the average area particle size of white carbon was 24 μm.

(Example 11)
Newspaper paper of Example 11 was obtained in the same manner as Example 1 except that the amount of white carbon added was 5 Kg / pulp ton.

(Example 12)
Newspaper paper of Example 12 was obtained in the same manner as Example 1 except that the addition amount of silica-coated regenerated particles was 5 kg / pulp ton.

(Example 13)
Newspaper paper of Example 13 was obtained in the same manner as Example 1 except that the addition amount of the silica-coated regenerated particles was 15 kg / pulp ton.

(Example 14)
Newspaper paper of Example 14 was obtained in the same manner as in Example 1 except that the amount of the silica-coated regenerated particles added was 50 kg / pulpton.

(Example 15)
Newspaper paper of Example 15 was obtained in the same manner as Example 1 except that the addition amount of white carbon was 10 kg / pulpton and the addition amount of silica-coated regenerated particles was 10 kg / pulpton.

(Example 16)
Newspaper paper of Example 16 was obtained in the same manner as in Example 1 except that the addition amount of white carbon was 16 kg / pulpton and the addition amount of silica-coated regenerated particles was 25 kg / pulpton.

(Example 17)
Newspaper paper of Example 17 was obtained in the same manner as in Example 1 except that the amount of white carbon added was 30 kg / pulpton and the amount of silica-coated regenerated particles added was 40 kg / pulpton.

(Example 18)
Newspaper paper of Example 18 was obtained in the same manner as Example 1 except that the addition amount of white carbon was 40 kg / pulpton and the addition amount of silica-coated regenerated particles was 55 kg / pulpton.

(Example 19)
Newspaper paper of Example 19 was obtained in the same manner as in Example 1 except that the amount of white carbon added was 45 kg / pulpton.

(Example 20)
Newspaper paper of Example 20 was obtained in the same manner as in Example 1 except that silica-coated calcium carbonate was used in place of the silica-coated regenerated particles.

(Comparative Example 1)
Newspaper paper of Comparative Example 1 was obtained in the same manner as Example 1 except that the area-average particle size of the silica-coated regenerated particles was 0.5 μm.

(Comparative Example 2)
Newspaper paper of Comparative Example 2 was obtained in the same manner as in Example 1 except that the area-average particle size of the silica-coated regenerated particles was 20 μm.

(Comparative Example 3)
Newspaper paper of Comparative Example 3 was obtained in the same manner as in Example 1 except that the area average particle size of white carbon was 5 μm.

(Comparative Example 4)
Newspaper paper of Comparative Example 4 was obtained in the same manner as Example 1 except that the area average particle size of white carbon was 30 μm.

(Comparative Example 5)
Newspaper paper of Comparative Example 5 was obtained in the same manner as in Example 1 except that 15 kg / pulpton of talc having an average area particle diameter of 8 μm was added instead of the silica-coated regenerated particles.

(Comparative Example 6)
A newsprint of Comparative Example 6 was obtained in the same manner as in Example 1 except that the silica-coated regenerated particles were not added.

  About the newsprint of Examples 1-20 and Comparative Examples 1-6, quality evaluation was performed by the following references | standards. The results are shown in Table 1.

[Evaluation]
(1) Ash content Measured according to JIS-P8251 (2003) “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method”.

(2) Whiteness Measured according to “Measuring method of paper, paperboard and pulp—ISO whiteness (diffuse blue light reflectance)” described in JIS-P8148.

(3) Opacity Measured according to “Paper Opacity Test Method” described in JIS-P8138.

(4) Printing Opacity Ink for offset rotary printing (trade name: Newsz Naturalis (black), Dainippon Ink Chemicals, Inc. The ratio of the back-surface reflectance after printing to the back-surface reflectance before printing when the printing amount is 9% and the ink amount is changed by Kogyo Co., Ltd .:
(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.

(5) Workability Using an offset rotary printing press (model number: LITOPOPIA BTO-4, manufactured by Mitsubishi Heavy Industries, Ltd.), printing was performed on newspaper paper of 50 continuous rolls. 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 accumulation 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.

(6) Area particle size and area particle size distribution “Area particle size” is a scanning electron microscope equipped with an energy dispersive X-ray analyzer (model number S-4800, manufactured by Hitachi High-Technologies Corporation, model number ENERGY EX-250). The diameter of the smallest circle (the circumscribed circle of particles) that can enclose the particles was observed for the filler particles observed by photographing the newspaper paper surface at a magnification of 3000 times. In the case of secondary particles in which particles are aggregated, the diameter of the aggregated secondary particles is defined as the particle size. The average area particle diameter was obtained by averaging 100 area particle diameters randomly extracted from the particles observed with the scanning electron microscope. The total of the two types of filler particles containing silica (white carbon and silica-containing particles), that is, the maximum value of the area particle size distribution of the filler particles in which silica is detected by an energy dispersive X-ray analyzer is the energy dispersive X-ray Filler particles containing silica observed by scanning with a scanning electron microscope (model number S-4800, manufactured by Hitachi High-Technologies Corporation, model number ENERGY EX-250, Horiba, Ltd.) with a magnification of 3000 times. 100 particles are randomly extracted, the number of filler particles is totaled for every 0.5 μm area particle size to obtain the distribution of area particle size, and the range of 15 μm to 25 μm is (A), 1 μm or more The range of 15 μm or less was defined as (B), and the presence or absence of a maximum value in the ranges of (A) and (B) was determined.

  It can be seen that the newsprints of Examples 1 to 20 all have high printing opacity and satisfactory workability, and are excellent in properties as newsprint for offset rotary printing. In particular, when the average area particle diameter of the silica-coated regenerated particles (silica-containing particles) is adjusted, it is confirmed that the quality is greatly influenced, and the average area particle diameter of the silica-coated regenerated particles is 2 to 12 μm. In particular, when it is 5 to 10 μm, it is shown that extremely high characteristics can be exhibited. In addition, the amount of ash in newsprint can be adjusted by adjusting the amount of filler added. The opacity increases when the ash increases, and when the ash is 8 to 13%, there is little drop of paper dust. It can be seen that the workability is also excellent.

  On the other hand, the newspaper of Comparative Example 1 has an average area particle diameter of the silica-coated regenerated particles that is too small to pass through the voids in the pulp fiber and is difficult to be fixed. The newsprint paper of Comparative Example 2 has an average area particle diameter of the silica-coated regenerated particles that is too large to enter into the gaps in the pulp fiber, the opacity is not improved, and the printing workability by removing the filler from the paper surface. I'm sorry. In addition, the newspaper of Comparative Example 3 has a small average area particle diameter of white carbon and has a maximum value only in the range of 1 to 15 μm in the area particle diameter distribution of the particles containing silica, and thus the opacity is not improved. Since the average area particle diameter of white carbon is too large, the newsprint paper of Comparative Example 4 has poor printing workability due to the removal of the filler from the paper surface. In addition, the one containing talc instead of the silica-containing particles (Comparative Example 5) has a lower printing opacity and a poor printing workability. It can be seen that the one containing no silica-containing particles (Comparative Example 6) has low printing opacity.

The newsprint of the present invention can be suitably used for offset rotary printing at a high speed of, for example, 170 to 200,000 copies / hour.

Claims (4)

Newsprint with at least two types of fillers added to pulp,
As these two kinds of fillers, white carbon and silica-containing particles are used,
The total of these two kinds of fillers is characterized by having an area particle size distribution having a maximum value in each of the following ranges (A) and (B) in the distribution of the area particle size counted every 0.5 μm. Newspaper.
(A) 15 μm to 25 μm (B) 1 μm to 15 μm   The newsprint according to claim 1, wherein the silica-containing particles are silica-coated regenerated particles obtained by coating silica on the surface of regenerated particles mainly made of deinked floss.   The newsprint according to claim 1, wherein the ash content is 8% by mass or more and 13% by mass or less. Basis weight is 38 g / m ² or more and 48 g / m ² or less,
Whiteness is 52% or more and 57% or less,
The newsprint according to any one of claims 1 to 3, wherein the opacity is 90% or more and 95% or less.