JP2011102446A - Newsprint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide newsprint using mechanical pulp produced from Cryptomeria wood, which has been difficult to use as pulp as a raw material and has high opacity and strength. <P>SOLUTION: The newsprint prepared by adding fillers to pulp of raw material is characterized by using mechanical pulp produced from Cryptomeria wood chips and Pinus wood chips in an absolute dry weight ratio of Cryptomeria wood chips: Pinus wood chips of 5:95 to 50:50 as pulp of raw materials, and containing white carbon having a volume-average particle diameter of 15 to 25 μm and inorganic particles having a volume-average particle diameter of 1.7 to 12.5 μm as fillers. The inorganic particles may be silica-compounded reclaimed particles prepared by compounding silica on the surfaces of reclaimed particles obtained through dehydration, drying, combustion and crushing processes for paper-making sludges as a main raw material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a newsprint that has both high opacity and strength and is suitably used for cold offset rotary printing.

  Newspaper paper has a very high demand for weight reduction from the viewpoints of logistics costs and resource saving. However, when the weight of the paper is reduced, the thickness of the paper is reduced, and the opacity, particularly the so-called printing opacity after printing, is greatly reduced. The decrease in the printing opacity causes a phenomenon of see-through from the opposite surface, that is, a so-called back-through, and has a problem that the printing surface quality of the printed back surface is deteriorated.

  Conventionally, in order to improve the opacity of newsprint, mechanical pulp having thick fibers having a high opacity improving effect has been frequently used as a raw material pulp. In particular, mechanical pulp made of pine genus wood chips, such as radiata pine having thick and long fibers, has been suitably used. However, from the viewpoint of recycling, the use of recycled paper pulp is increasing, and the amount of mechanical pulp is naturally reduced, and new measures for improving opacity are required. In addition, with the widespread use of waste paper pulp, recently recycled paper containing waste paper pulp has been reused, and the fact that waste paper pulp is being reused repeatedly has led to the strength of the newsprint obtained. In addition, this causes a decrease in opacity, lowers the print-through and concealment during printing, and causes inconveniences such as a decrease in appearance such as fading of the printing surface and missing halftone dots.

  In the paper manufacturing industry, as an opacity countermeasure associated with the weight reduction of newsprint, attempts have been made to improve opacity by increasing the amount of filler and increasing the amount of ash derived from waste paper pulp. As a filler for increasing the opacity, for example, white carbon or calcium carbonate is generally used. However, simply increasing the amount of white carbon or calcium carbonate causes a problem that the improvement in opacity reaches its peak and the strength decreases and paper dust increases.

  Patent Document 1 discloses a technique using, for example, white carbon having a fine particle shape with a large pore volume as means for solving the problem. The white carbon disclosed in Patent Document 1 is a fine one obtained by neutralizing sodium silicate with sulfuric acid. Since the particle size is smaller than that of the conventional white carbon particles, the light scattering property is good. The opacity of the film can be improved. However, the white carbon according to this technology has a fine shape, and it is necessary to agglomerate with a sulfuric acid band etc. and fix it to the raw material pulp when using it, so the stability at the wet end decreases, and the quality at the time of operation There is an inconvenience that it is difficult to manage.

  Further, as another technique, Patent Document 2 includes newspapers mainly containing white carbon and calcium carbonate and containing them in an atomic absorption analysis ratio of 9: 1 to 5: 5. Has also been proposed. This newsprint uses a cheap calcium carbonate, and a technique for improving opacity at a low cost by processing at pH 6 to 8 with a good white carbon yield is disclosed. However, although this newsprint has an effect of improving opacity, there are many voids between white carbon particles and white carbon particles and pulp fibers that have become large due to secondary aggregation, and light is transmitted through these voids. Therefore, the effect of improving opacity is not sufficient.

  By the way, Japanese cedar, which has been planted a lot in Japan, has been used for a variety of purposes such as building materials and earth and lumber since ancient times. It has been replaced and the use of cedar is decreasing. In view of this situation, in recent years, effective use of cedar thinning is strongly desired from the viewpoint of avoiding the devastation of Japanese cedar forests.

  The paper industry has also tried to use cedar as a raw material for pulp, but cedar has an extremely high lignin content and is difficult to digest and bleach, and the fiber form of cedar is other conifers. It has been considered that cedar wood is not suitable as a raw material for pulp because it has shortcomings such as short fiber length and small fiber width compared to wood.

  Under such circumstances, as a method for producing pulp using cedar wood as a raw material, Patent Document 3 discloses that 100% of cedar wood chip raw material (preparation of chips with sodium sulfite having an initial pH of 7.0 to 9.5). Treatment)-Chemi-thermomechanical pulp manufacturing process including a process consisting of: (defining by primary refining fitted with refiner segments having 4-5 dams)-(beating by secondary refining) Techniques for obtaining high-yield, high-quality chemithermomechanical pulp have been proposed. However, since this method promotes defibration by chemical treatment, a decrease in opacity accompanying the outflow of lignin occurs. Therefore, a new measure for improving opacity is desired for blending into newsprint. Further, since chemical treatment of the chip raw material is performed, new equipment investment is required and there is a problem that the chemical cost increases.

Japanese Patent No. 2960001 JP 2002-201590 A Japanese Patent Laid-Open No. 2004-225201

  The present invention has been made in view of these disadvantages, and provides newsprint paper having high opacity and strength while using mechanical pulp made from cedar wood that has been difficult to use as pulp. It is intended.

[Invention of Claim 1]
As raw material pulp, Cryptomeria wood chips and Pinus wood chips are used as raw materials, and the absolute dry weight ratio between the cedar and pine wood chips is 5:95 or more and 50:50. Newspaper paper comprising mechanical pulp comprising: white carbon having a volume average particle diameter of 15 μm to 25 μm and inorganic particles having a volume average particle diameter of 1.7 μm to 12.5 μm as a filler. .

  In addition to the long fiber and thick fiber-derived pulp, which is generally used as a raw material for mechanical pulp, the newsprint is made of cedar genus pulp with short fibers and narrow fiber width and high opacity. It is used by mixing at the above absolute dry weight ratio. Therefore, the newsprint is made so that thin and short cedar-derived pulp fibers are entangled between the meshes formed by thick and long pine-derived pulp fibers, and the gap is filled, thereby increasing light scattering properties. Opacity is improved because the light transmittance is lowered. In addition, the newspaper paper is made so that thin and short cedar-derived pulp fibers are entangled between the meshes formed by thick and long pine-derived pulp fibers so as to fill the gaps. By suppressing the decrease in tear strength, which is a drawback of, and by incorporating pulp fibers derived from cedar with a large amount of resin components such as lignin, the friction effect between many different fibers can be exhibited, and the tensile strength can be improved. It has high strength.

  In addition, the newsprint includes, as internally added fillers, white carbon having a volume average particle diameter measured by a laser method of 15 μm or more and 25 μm or less, and inorganic particles having a volume average particle diameter of 1.7 μm or more and 12.5 μm or less. Contains. When white carbon having a volume average particle size of 15 μm or more and 25 μm or less and inorganic particles having a volume average particle size of 1.7 μm or more and 12.5 μm or less are used in combination, 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 fixed so as to fill between the fine pulp fibers in which the particles having a large particle size cannot be fixed and between the mesh formed by the pulp fibers and the particles having a large particle size. It will have opacity. According to the findings of the present inventors, in addition to the effect of improving the opacity, white carbon having a volume average particle diameter measured by a laser method of 15 μm or more and 25 μm or less, and a volume average particle diameter of 1.7 μm or more and 12.5 μm. It has been found that by using together with the following inorganic particles, paper dust drops can be reduced, dirt in the machine system in the manufacturing process can be reduced, and machine operability can be improved. Furthermore, the newsprint is made so that thin, short cedar-derived pulp fibers are intertwined between the meshes formed by thick and long pine-derived pulp fibers and slender waste paper deinked pulp fibers, thereby filling the gaps. By combining such a filler having a different fiber structure and particle size, the yield of the filler is improved and it has extremely high opacity.

[Invention of Claim 2]
2. The composite particles according to claim 1, wherein the inorganic particles are silica composite regenerated particles obtained by combining silica with regenerated particles obtained through a dehydration, drying, combustion, and pulverization process using papermaking sludge as a main raw material. Newspaper.

  The inorganic particles may be silica composite regenerated particles in which silica is combined with the surface of regenerated particles obtained through dehydration, drying, combustion, and pulverization processes using deinking floss and papermaking sludge as main raw materials. Since the surface of the silica composite 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, since the silica composite regenerated particles originally use regenerated particles with high opacity as the core, it is possible to improve opacity and reduce manufacturing costs.

[Invention of Claim 3]
The newsprint according to claim 1 or 2, wherein the content of silica in terms of oxide contained in the newsprint is 4.0% by mass to 7.2% by mass.

X-ray microanalyzer (model number: E-MAX · S-2150, manufactured by Horiba, Ltd.) The content of silica in the newsprint calculated from the following formula from the mass ratio of the oxide converted silica in the element converted to oxide obtained by the elemental analysis according to 4) is 4. The content is preferably 0% by mass or more and 7.2% by mass or less.
Silica content of newspaper (oxide equivalent, mass%) = ash content (mass%) × silica content in ash residue (oxide equivalent, mass%) ÷ 100
According to the newspaper, as the filler to be internally added, white carbon having a volume average particle diameter measured by a laser method of 15 μm or more and 25 μm or less, and inorganic particles having a volume average particle diameter of 1.7 μm or more and 12.5 μm or less, In addition, the silica content in terms of oxide is in the above range, so that white carbon and inorganic particles are effectively fixed between the voids of the pulp fiber, and can have extremely high opacity, Paper dust fall can be reduced. If the oxide-converted silica content is less than the above range, sufficient opacity improvement effect cannot be exhibited, and if it exceeds the above range, the opacity increases, but the added amount of filler is too much, and the paper strength decreases, There is a risk of paper dust falling.

[Invention of Claim 4]
The newsprint according to any one of claims 1 to 3, wherein the mechanical pulp is pulp treated with a screen having a slit width of 0.15 mm or less.

  It is preferable that the mechanical pulp is carefully selected by a screen having a slit width of 0.15 mm or less. In the mechanical pulp selection process, the shiving rate can be adjusted to a suitable range by performing a pulp selection process using a screen having a slit width in the above range. As a result, the newsprint paper can be provided with high opacity because it appropriately contains shives. A shive refers to a bundled portion of pulp fibers that has not been defibrated.

[Invention of Claim 5]
After blending so that the dry weight blending ratio of cedar and pine wood chips is 5: 95-50: 50 as raw material pulp and mechanical pulping, it is carefully selected with a screen with slit width of 0.15 mm or less 60 to 90% of deinked waste paper pulp is blended with 10 to 40% of the machined pulp, the ash content is 5 to 15% by mass, and the oxide-converted silica content contained in the newspaper is 4.0 to 7.2% by mass. The filler is made by adding white carbon having a volume average particle diameter of 15 μm or more and 25 μm or less and inorganic particles having a volume average particle diameter of 1.7 μm or more and 12.5 μm or less as a filler so as to be mass%. A method for producing newsprint.

  By adopting the above manufacturing method, the newsprint can be a newsprint with high opacity and strength as newsprint for offset rotary printing.

  According to the present invention, it is possible to provide newsprint with high opacity and strength while using mechanical pulp made from cedar wood that has been difficult to use as pulp.

1 is a schematic diagram of a production facility for regenerated particles or regenerated particle aggregates preferably used in the present invention. It is a schematic diagram of a 2nd combustion furnace, (a) is a longitudinal cross-sectional view, (b) is an expanded view of an inner surface.

  Hereinafter, embodiments of the present invention will be described in detail.

  The newsprint of the present invention contains white pulp and inorganic particles as mechanical pulp and two kinds of fillers as raw pulp.

  As raw materials for this mechanical pulp, wood chips of Cryptomeria and wood chips of Pinus are used. The absolute dry weight ratio between the cedar wood chip and the pine wood chip is preferably 5:95 or more and 50:50 or less, particularly preferably 10:90 or more and 40:60, and 15:85 or more and 25: More preferably, it is 75 or less.

  The fiber form of the pine genus is characterized by a long fiber length (usually about 5 mm) and a wide fiber width (usually about 50 μm). On the other hand, the cedar fiber form is characterized by a short fiber length (usually about 3 mm) and a narrow fiber width (usually about 30 μm). According to the newsprint containing mechanical pulp made from two kinds of wood chips having the above-mentioned absolute dry weight ratio, the thin and short cedar-derived pulp fibers are formed between the meshes formed by thick and long pine-derived pulp fibers. Since the paper is made so as to be intertwined to fill the gap, the light scattering property is increased and the light transmission property is lowered, so that the opacity is improved. Moreover, the high friction effect between cedar and pine pulp fibers is exhibited by blending cedar-derived pulp fibers with a large amount of resin components such as lignin, and the tensile strength can be improved.

  If the absolute dry weight ratio of the cedar wood chip is less than 5:95, when the pulp fiber is made, the cedar-derived pulp fiber cannot be filled between the meshes formed by the pine genus-derived pulp fiber, Opacity is not improved sufficiently. Further, the effect of improving the friction between fibers due to the mixing of cedar pulp having a large amount of resin components such as lignin is not sufficient, and the improvement in tensile strength is small. On the other hand, when the absolute dry weight ratio of the cedar wood chips is larger than 50:50, the amount of thick and long pine-derived pulp fibers decreases, and thus the paper strength such as tear strength decreases. Further, if the absolute dry weight ratio of the cedar wood chips is larger than the above upper limit, the amount of shives to be described later increases, and the quality of the pulp may be lowered.

  The shibu rate of the mechanical pulp is preferably 0.018% or more and 0.072% or less, and particularly preferably 0.018% or more and 0.066% or less. A shive refers to a bundled portion of pulp fibers that has not been defibrated. This “shy rate” is a value measured using a screen plate having a slit width of 0.15 mm and 100 g of sample dry pulp treated with a flat screen in accordance with TAPPI T275sp98.

  When cedar wood is treated with a refiner segment, a squirrel peculiar to the cedar genus is generated. The schives peculiar to the genus Cedar are harder than the shives generated in other tree species and have the property of being difficult to defibrate. The newspapers actively utilize the schives peculiar to the cedar genus mainly produced from cedar wood, and the amount of shives is 0.018% or more to 0.072%, preferably 0.018% or more and 0.066%. High opacity is realized by the following. That is, this shive has a branch shape by having a bound portion where pulp fibers are not defibrated. This branch-shaped shive can be suitably accommodated between relatively large meshes formed mainly by pulp fibers derived from the pine genus, and as a result, opacity can be increased. Furthermore, this binding part contains more resin components such as lignin than the others, and this functions as an opacity improver similar to fine fillers and scatters light to increase opacity. In addition, the strength of the paper is improved because the resin component increases the adhesion between the fibers.

  When the mechanical pulp shive rate is smaller than the above lower limit, the content of the pulp fiber having a branch-like shape is reduced, so that the cedar-derived pulp fiber is less likely to fill the mesh formed by the pine genus-derived pulp fiber, Small increase in opacity. In addition, since the amount of the accompanying resin component such as lignin also decreases, the opacity increasing function and paper strength improving function due to this resin component are not sufficiently exhibited.

  On the other hand, if the mechanical paper shive rate is higher than the upper limit, the amount becomes visible in the newsprint from which the shive is obtained, which may reduce the quality. Specifically, this shive is often found as a foreign material having a gloss like metal on the paper surface, and there is a possibility that the paper quality is deteriorated.

  A well-known thing can be used as a wood chip | tip of the Cryptomeria genus (Cryptomeria) used as the raw material of this mechanical pulp. Japanese cedar is one type of Cryptomeria japonica in Japan and can be used effectively. The Cryptomeria japonica has been cultivated and improved since it is relatively easy to cut. At present, there are 9 varieties from a botanical point of view, and it is a tree species with an extremely large number of forestry varieties. Speaking of finer varieties, it is said that there are about 100 varieties, such as spinach cedar, peas cedar, and green cedar. Japanese cedar grows across Honshu, Shikoku, Kyushu, and other parts of the country, and exists in the form of natural forests and plantations.

  In the present invention, the pine genus wood chip suitably used in combination with the cedar wood is not particularly limited, and known ones can be used, for example, red pine, black pine, spruce, todomatsu, radiata pine, etc. Although listed, Radiata pine is preferably used from the viewpoints of the distribution amount, cost, and ease of pulp processing.

  As a method for producing this mechanical pulp, a known method can be employed. For example, a defibration process by primary refining-a beating process by secondary refining-a fine selection process-a bleaching process may be adopted. it can.

  Wood chips mixed with cedar wood chips and pine wood chips are first subjected to a primary refining process. The apparatus used for this treatment is a pressurization or atmospheric pressure refining apparatus, and is defibrated into pulp fibers under known conditions. For refining, a general defibrating apparatus is sufficient, and defibration is preferably performed with a single disc refiner, a conical disc refiner, a double disc refiner, a twin disc refiner, or the like. The concentration of the chips during the refining step is preferably about 20 to 60% by solid mass, and the processing temperature is preferably 100 to 150 ° C. More preferably, it is 120-135 degreeC. For the purpose of improving defibration, it is preferable to pre-heat with a preheater prior to the primary refining. The temperature in this case is preferably 100 to 135 ° C.

  Next, the defibrated pulp is subjected to secondary refining treatment. As this device, a known refining device is used, and it is pulverized under known conditions to lower it to a desired pulp freeness. This step is carried out under pressure or normal pressure, and the refining device is preferably a general pressure or normal pressure type defibrating device, and the concentration can be carried out at about 10 to 60%.

  Subsequently, it is diluted to a concentration of 1 to 5%, and unbeaten fibers and shives are removed with a selective screen. In the selection process, it is preferable that the selection process is performed with a screen having a slit width of 0.15 mm or less. An ordinary screen having a slit width of about 0.20 mm is used, but a large amount of shives contained in the cedar are removed by carefully selecting pulp using a screen having a slit width of 0.15 mm or less. And a shiving rate suitable for the newsprint can be adjusted to 0.018% or more and 0.072% or less. As a result, the newsprint includes a moderate amount of shive and can have high opacity. On the other hand, if the slit width is 0.10 mm or less, the screen pores are too small, and the screen may be clogged and the processing amount may be reduced.

  The raw material pulp of the newsprint preferably contains deinked waste paper pulp in combination with the mechanical pulp. As content of the said mechanical pulp in raw material pulp, 10 to 40 mass% is preferable, and 20 to 40 mass% is more preferable. If the content of the mechanical pulp is less than the above range, it is difficult to improve the opacity, and the newspaper does not become bulky and has no waist, which may reduce the transportability and workability. In addition, if the content of mechanical pulp exceeds the above range, it becomes bulky and it becomes difficult to set the paper thickness accompanying weight reduction to a predetermined range, and the content of deinked waste paper pulp is reduced, so that resources are effective. Environmental properties such as use are reduced.

  The content of the deinked waste paper pulp in the raw material pulp is preferably 60% by mass or more and 90% by mass or less, particularly preferably 70% by mass or more and 90% by mass or less, and further preferably 80% by mass or more and 90% by mass or less. By setting the content of the waste paper deinked pulp in the raw material pulp to be in the above range, environmental properties such as effective use of resources are improved, and further, printing suitability such as ink deposition properties is improved. According to the newsprint, paper is made so that thin and short cedar-derived pulp fibers are intertwined between the mesh formed by thick and long pine-derived pulp fibers and slender waste paper deinked pulp fibers to fill the gaps. The opacity is improved because the light scattering property is increased and the light transmittance is decreased.

  Preferably, among the deinked 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 newspaper waste paper pulp and magazine waste paper pulp in combination. 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, the waste paper pulp generally contains 50% or more of recycled paper pulp, the content of virgin mechanical pulp and kraft pulp is low, and various virgin pulps are used for newsprint. Even if it is used, it is particularly preferable when used in combination with the mechanical pulp according to the present invention in that it is once paper-made and recycled into a waste paper pulp by a waste paper treatment, so that its properties are homogenized and has almost constant properties.

  Other pulps used as raw materials for the newspaper include, for example, hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP) Chemical pulps such as softwood unbleached kraft pulp (NUKP), hardwood semi-bleached kraft pulp (LSBKP), softwood half-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp, stone grand pulp (SGP), pressurized stone Arbitrary virgin pulp, such as ground pulp (TGP), chemi-ground pulp (CGP), and ground wood pulp (GP), can be used as appropriate.

  The newspaper has a volume average particle diameter of 15 μm or more and 25 μm or less, preferably 18 μm or more and 22 μm or less, and a volume average particle diameter of 1.7 μm or more and 12.5 μm or less, preferably 5.5-11. Contains 0 μm inorganic particles. Thus, the inorganic particles having a volume average particle size smaller than the volume average particle size of white carbon are distributed in voids formed by white carbon and pulp fibers. 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. Therefore, inorganic particles are caught in such voids, and the opacity is improved by filling the voids with inorganic particles. Furthermore, according to the knowledge of the present inventors, the opacity is further improved by combining with the above-mentioned white carbon and the network structure of inorganic particles by combining with the structure of the raw material pulp made of cedar and pine wood. It becomes possible to make it.

  By adjusting the addition amount of these fillers, the ash content in the newsprint is adjusted. The ash content based on JIS P 8251 in the newspaper is preferably 5% by mass to 15% by mass, and particularly preferably 6% by mass to 13% by 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.

  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.

  The volume average particle diameter of the white carbon is preferably 15 μm or more and 25 μm or less, and particularly preferably 18 μm or more and 22 μm or less. 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 particle diameter of white carbon in the present invention also refers to the average particle diameter of the aggregated secondary particles.

  If the volume average particle size of 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, when the volume average particle diameter of the white carbon exceeds the above upper limit, it becomes larger than the mesh size of the mesh structure formed by the pulp fibers, so that it is difficult to enter and fix this part. .

  The amount of white carbon added is preferably 1% by mass or more and 4% by mass or less, and particularly preferably 1.5% by mass or more and 3% by mass or less in terms of solid content with respect to the raw material pulp. If the amount of white carbon added is less 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 amount of white carbon 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 addition amount of white carbon, the strength between pulp fibers will fall and paper strength will fall.

  The inorganic particles used in the present invention have a volume average particle size smaller than that of the above-mentioned white carbon.

  The inorganic particles can be selected from fillers generally used for papermaking. For example, clay, aluminum hydroxide, titanium dioxide, white carbon, calcium carbonate, etc. are used, but general fillers used in papermaking applications, that is, calcium carbonate (heavy and light), clay, talc, etc. are made of silica. It is preferable to use composite silica composite inorganic particles. More preferably, the use of silica composite regenerated particles or silica composite regenerated particle aggregates in which the surfaces of regenerated particles or regenerated particle aggregates described later are combined with silica results in particles that are more bulky and have higher opacity. Newspaper paper having high opacity can be obtained by using it in combination with mechanical pulp made of cedar and pine.

  The volume average particle diameter of the inorganic particles is preferably 1.7 μm or more and 12.5 μm or less, and particularly preferably 5.5 μm or more and 11.0 μm or less. When the inorganic particles have a volume average particle diameter in the above range, they can enter and adhere to the voids formed by pulp fibers and white carbon particles. Therefore, according to the newspaper, high opacity can be provided. In addition, the use of inorganic particles having such a particle size increases the adhesiveness to the voids, so that particles once fixed in the manufacturing process can be spilled, that is, the amount of paper powder can be reduced, and therefore the manufacturing process. As well as reducing dirt in the machine system, machine operability can be improved.

  If the volume average particle diameter of the inorganic particles exceeds the above upper limit, the particle diameter is too large for the voids, so that it cannot enter the voids, resulting in a decrease in stickiness and thus contributing to an improvement in opacity. do not do. On the contrary, if the volume average particle diameter of the inorganic particles is smaller than the lower limit, the particle diameter is too small with respect to the voids, so that it is easy to pass through the voids and the sticking 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, even if it is fixed, the strength is weak and it is easy to fall off. Therefore, the rate of falling off in the manufacturing process increases, and there is a risk that machine operability may be reduced by generating dirt in the machine system in the manufacturing process.

  The addition amount of the inorganic particles is preferably 0.7% by mass or more and 5.5% by mass or less, and particularly preferably 1.5% by mass or more and 4.0% by mass or less in terms of solid content with respect to the raw material pulp. If the added amount of the inorganic 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, if the amount of inorganic particles added exceeds the above upper limit, the amount added is too large with respect to the volume of the voids formed, so that strong fixation cannot be achieved and the filler will fall off. Furthermore, the increase in filler weakens the adhesion between pulp fibers, and as a result, the strength of the newsprint decreases. It is preferable that the addition amount of the inorganic particles is 1.5 times or more the addition amount of the white carbon because the inorganic particles can efficiently fill the gaps between the white carbons and the opacity is improved.

(Regenerated particles)
Next, composite particles composed of silica and inorganic particles excellent in opacity that are suitably used as inorganic particles will be described. The use of regenerated particles or regenerated particle aggregates as the inorganic particles is particularly preferable because newspaper paper with better opacity can be obtained. Composite particles consisting of silica and recycled particles or aggregates of recycled particles are different from the commonly used calcium carbonate, talc, and clay in their constituent components and shape, and have excellent opacity. The amount of filler used can be reduced while maintaining opacity.

(Production process of regenerated particles and regenerated particle aggregates)
Recycled particles are deinked floss separated from pulp fibers in the deinking process of waste paper processing equipment that produces waste paper pulp, and paper sludge separated from paper mill wastewater as the main raw material, and the main raw material is dehydrated and dried. It is obtained through a combustion and pulverization process. For example, the manufacturing method described in Japanese Patent No. 3869455 can be used as the manufacturing method. When used as an internal filler, it is preferable to adjust the particle size by pulverizing the particle size to 1.0 to 10.0 μm by a known pulverization method. If the particle diameter is smaller than 1.0 μm, the yield is poor and it is not preferable because it easily becomes a foreign substance in the paper machine system. If it is larger than 10.0 μm, the formation is deteriorated, and the strength (tensile strength and tear strength) decreases. This is not preferable because there is a possibility.
Here, the particle diameter of the regenerated particles is a volume average particle diameter measured by a laser analysis type particle size distribution measuring apparatus “SALD-2200 type” manufactured by Shimadzu Corporation.

  The regenerated particles produced by the above method form a regenerated particle aggregate in which several individual particles are aggregated, and have an irregular shape such as a lump-like mass. Due to this irregularity, the thickness of the paper tends to be increased when it is contained in newsprint, and the printing opacity of the newsprint can be increased because of the highly opaque particles.

  These regenerated particles preferably contain calcium, silica, and aluminum in a mass ratio of 30 to 82: 5 to 40:13 to 30 in terms of oxides, and more preferably 40 to 60:25 to 40:18 to 25. It is a mass ratio. By including calcium, silica, and aluminum in a mass ratio of 30 to 82: 5 to 40:13 to 30 in terms of oxide, the specific gravity is light and excessive aqueous solution absorption is suppressed, so that the dehydration property in the dehydration process is good. It is.

  As a method for adjusting the calcium, silica, and aluminum oxide conversion ratio of regenerated particles or regenerated particle aggregates in the firing step, the main component is to adjust the raw material composition in the deinking floss, but drying and classification In the process and the baking process, it is possible to adjust the coating floss and the adjustment process floss with a clear origin by means of including in the process by spraying or by means of containing the incinerator scrubber lime.

  For example, neutral papermaking wastewater sludge and wastewater sludge from the coated paper manufacturing process are used to adjust calcium in recycled particles and inorganic particle aggregates, and white carbon as an opacity improver is used to adjust silicon. Wastewater sludge from newsprint manufacturing systems that contain a large amount of additives, papermaking drainage sludge that uses sulfuric acid bands such as acidic papermaking to adjust aluminum, and wastewater from high-quality papermaking processes that often use talc. Sludge can be used as appropriate.

[Attached process]
In production facilities, it is preferable to remove foreign substances other than regenerated particles and regenerated particle aggregates. For example, sand, plastic foreign materials, metals, etc. with pulpers, screens, cleaners, etc., before the deinking process of the used paper pulp manufacturing process It is preferable from the viewpoint of removal efficiency to remove. In particular, iron contamination is a substance that reduces the whiteness of fine particles due to oxidation, so it is recommended to avoid iron contamination and selectively remove it. Design or lining each process with materials other than iron, It is preferable to prevent iron from being mixed into the system due to abrasion or the like, and to further remove iron selectively by installing a high magnetic material such as a magnet in the drying / classifying equipment.

[Silica composite regenerated particles, silica composite regenerated particles aggregate]
In the present invention, it is preferable to use fillers generally used for papermaking, that is, silica composite inorganic particles in which calcium carbonate (heavy and light), clay, talc and the like are combined with silica. The use of silica composite regenerated particles or silica composite regenerated particle agglomerates in which the surface of the agglomerate is composited with silica is particularly preferred because it results in particles that are more bulky and have higher opacity, and a newspaper with high opacity can be obtained. .

  As a suitable measure for precipitating silica on the regenerated particles or regenerated particle aggregates, the method described in Japanese Patent No. 3907688 or Japanese Patent No. 393596 can be used. However, it is preferable to carry out as follows because silica composite regenerated particles or silica composite regenerated particle aggregates having better opacity can be obtained.

<Silica composite particles>
Next, the silica composite particles of the present invention will be described in more detail while taking the silica composite regenerated particles as an example and showing the production method.

(Silica composite treatment process)
As described above, regenerated particles mainly made of paper sludge and deinking floss are added to and dispersed in an alkali silicate aqueous solution, and a mineral acid is added in a temperature range of 50 ° C. to 100 ° C. while stirring. . More preferably, it is added in at least two stages to carry out a silica composite reaction.

  The particle size suitable for the filler use etc. of the regenerated particle of this form is 1.0 μm to 10.0 μm. The particle diameter of the regenerated particles after the pulverization step is a volume average particle diameter measured by a laser analysis type particle size distribution measuring apparatus “SALD-2200 type” manufactured by Shimadzu Corporation.

  If the particle size of the regenerated particles is excessively smaller than 1.0 μm, a sufficient particle size may not be obtained at the time of silica composite, and there is a possibility of clogging into a glass shape when silica is composited. Within the scope of the present invention, the silica composite reaction can be sufficiently promoted. On the other hand, if the particle size is excessively large, excessively regenerated silica composite particles are likely to be produced, and the opacity may be lowered.

  Silica composite is a reaction operation for generating silica sol particles having a particle diameter of 10 to 20 nm (measured particle diameter by a scanning electron microscope) on the surface of regenerated particles. The particle size of the silica sol particles can be controlled by the stirring conditions during the reaction, the addition conditions of the mineral acid, and the like.

  The present inventors have surpassed the knowledge that the pore volume of all fine pores of the internally added fine particles has been regarded as an index of oil absorption and opacity, and the actual oil absorption is only the pore volume of inorganic fine particles. In addition, the silica composite regenerated particles that can be suitably used in the present invention have been found to have a high contribution of the ability to retain oil between the particles of inorganic fine particles. It has been found that pores of 1,000 angstroms or less greatly contribute to the substantial oil absorption.

  The pore volume of the silica composite regenerated particles obtained in the present invention is a measured value using a mercury intrusion porosimeter (“PASCAL 140/240” manufactured by Terumo), and the pore volume in a region of 10,000 mm or less is 0.00. 5 to 1.5 cc / g, preferably 0.68 to 1.45 cc / g, more preferably 0.70 to 1.35 cc / g.

  When the pore volume of the pores in the region of 10,000 mm or less is less than 0.5 cc / g, sufficient oil absorption cannot be expressed, and when it exceeds 1.5 cc / g, the oil absorption is improved. Decrease in opacity is likely to occur.

  In a preferred embodiment of the present invention, the particle diameter of the obtained silica composite regenerated particles is set in the range of 1.7 to 12.5 μm, and the ratio of silica in terms of oxide contained in the silica composite regenerated particles is set. By setting it as 10.0-50.0 mass%, the high oil absorption and the opacity improvement effect can be acquired.

Although it does not specifically limit regarding alkali silicate aqueous solution, A sodium silicate solution (No. 3 water glass) is desirable at the point which is easy to acquire. The concentration of the alkali silicate solution is preferably 3 to 10% by mass in terms of the silicic acid content in the aqueous solution (in terms of SiO ₂ ). The composite of the regenerated particles and silica formed when the amount exceeds 10% by mass is not an inorganic fine particle / silica composite aggregate, but the regenerated particles are coated with white carbon, and the porosity of the regenerated particles in the core part, There is a risk that the optical properties may not be exhibited. On the other hand, if the amount is less than 3% by mass, the silica component in the composite particles is lowered, so that it is difficult to form regenerated particles combined with silica.

  The slurry concentration in the case where a regenerated particle or regenerated particle aggregate is added to and dispersed in an alkali silicate aqueous solution to prepare a slurry is preferably 8 to 14% by mass. By adjusting the slurry concentration, the particle size of the silica composite regenerated particles of the regenerated particles to be formed is controlled, and at the same time, the composition ratio of the regenerated particles and silica is adjusted. Mineral acids used in the present invention include dilute sulfuric acid, dilute hydrochloric acid, dilute nitric acid and other mineral acids, and dilute sulfuric acid is most desirable from the viewpoint of price and handling. Furthermore, when using dilute sulfuric acid, it is preferable to add the mineral acid at a concentration of about 4 to 10 N in terms of production efficiency and composite silica homogeneity. If it is less than 4N, the reaction is slow, and if it exceeds 10N, a local reaction occurs, and there may be a problem that amorphous composite particles that are unevenly distributed are likely to be generated. Moreover, since silica precipitates in a short time, so that there is much mineral acid addition amount, it is desirable to adjust an addition rate according to those conditions. Addition within 5 minutes makes the structure of the uniform reaction system insufficient.

  Since the regenerated particles or regenerated particle aggregates preferably used in the present invention contain calcium, aluminum, and silica as constituent elements, addition of an excessive concentration of mineral acid may cause alteration of the regenerated particles.

  As described above, the present invention adds and disperses an aqueous solution of alkali silicate to a regenerated particle or regenerated particle aggregate at a solid content ratio of 100: 5 to 100: 20 to form a slurry, while stirring. In the temperature range of 50 to 100 ° C., the mineral acid is added in at least two stages to perform a silica composite reaction.

  When the ratio of the alkali silicate aqueous solution to the regenerated particles or the regenerated particle aggregate is less than 100: 5 in terms of solid content, the silica composite effect of the obtained silica composite regenerated particles is low, and the effect of improving opacity is difficult to obtain. If the ratio exceeds 20, the amount of oil absorption increases and the ink absorbency is high, so that the ink sinks, so-called poor color developability may occur.

  In the step of adding the regenerated particles to the alkali silicate aqueous solution, the temperature of the alkali silicate aqueous solution can be heated to a temperature of 50 ° C. or higher, and then heated. When the porous regenerated particles are added in a state where the temperature of the aqueous alkali silicate solution is heated to 50 ° C. or higher in advance, the fluidity by heating is improved, so that the slurry can be easily homogenized. A homogeneous mixed slurry of alkali silicate and regenerated particles can be obtained.

On the other hand, after preparing a homogenized alkali silicate and regenerated particle slurry, the mixture can be heated and stirred. As a heat source in this case, a known heat source can be used. For example, by blowing live steam (for example, 13 kg / cm ² , 120 ° C.) in the factory, the temperature raising time can be shortened, and the regenerated particle slurry can be used. It is possible to prevent the temperature from being reduced when added, and to rapidly increase the temperature and the reaction, thereby improving the production efficiency.

  Regarding the reaction temperature during the production of the silica composite regenerated particles in the present invention, a slurry temperature range of 50 to 100 ° C., particularly a slurry temperature range of 50 to 98 ° C. is desirable. As a result of intensive studies by the present inventors, the reaction temperature with the regenerated particles used in the present invention affects the formation of silica, the crystal growth rate, and the mechanical strength of the formed silica composite regenerated particles. When the reaction temperature is less than 50 ° C., the rate of silica formation / growth does not occur or is slow, the silica composite regenerated particles have poor silica composite properties, are difficult to combine sufficiently, and the composite is formed by the shearing force applied during the making of the filler-added paper. Fragile. If it exceeds 100 ° C., the reaction process becomes complicated because an autoclave must be used because it is an aqueous reaction. In addition, the reaction proceeds excessively to form a dense silica composite regenerated particle form, and the opacity of the resulting silica composite regenerated particle is lowered, making it difficult to achieve the intended purpose.

  In the present invention, it is desirable to add at least two stages of mineral acid and to control the temperature at that time. That is, the slurry temperature at the time of adding the mineral acid in the first stage is 50 to 75 ° C., and the slurry temperature at the time of adding the mineral acid after the second stage is at least 10 ° C. higher than that at the first stage. Is desirable. Specifically, the desirable temperature conditions are that the liquid temperature in the first stage is 50 to 75 ° C., the temperature in the second stage is 70 to 100 ° C. in accordance with the number of mineral acid addition stages, and 90 in the final stage of the reaction. The temperature is set at a temperature of not lower than 98 ° C. and not higher than 98 ° C. Under these temperature conditions, more uniform silica composite regenerated particles can be obtained.

  The pH of the final reaction solution is preferably 8.0 to 11.0, more preferably 8.3 to 10.0, and most preferably 8.5 to 9.0.

  In the production of white carbon obtained by reacting a conventional alkali silicate and mineral acid, in order to complete the reaction between the alkali silicate and the mineral acid, the mineral acid is added to the alkali silicate until the pH is 5.5 to 7.0. However, when mineral acid is added until the pH reaches 7.0 or less, the calcium component contained in the regenerated particles is easily changed to calcium hydroxide, and the resulting silica composite regenerated particles are obtained. This is not preferable because the particle diameter of the toner is excessively reduced, the shape becomes inhomogeneous, the yield on paper is reduced, the generation of paper dust, and sufficient opacity are difficult to obtain. When the pH exceeds 11.0, the reaction between the alkali silicate and the mineral acid becomes dull, and it becomes difficult for silica to be combined with the surface of the regenerated particles, so that it is difficult to obtain sufficient opacity.

  When the mineral acid is added in one stage, it is preferable to set the addition amount of the mineral acid so that it takes 40 minutes or more for the pH to decrease by one.

  In the present invention, as described above, the mineral acid is preferably added in two or more stages. In this case, it is preferable to uniformly add the mineral acid in each stage in order to obtain a homogeneous silica composite. In addition, after one stage of addition (addition until the mineral acid has a neutralization rate of 20 to 50% with respect to the aqueous alkali silicate solution), a holding time of about 5 minutes to 20 minutes is made, so that the silica complex reaction is performed. A holding state is provided, silica is uniformly combined on the surface of the regenerated particles, and the addition of the mineral acid in the second stage can further promote the layered composite of silica, so that the surface of the regenerated particles is more uniformly distributed. Silica can be composited.

  The addition amount of the mineral acid for one stage is preferably set so that it takes 10 minutes to 45 minutes in order to uniformly combine silica on the surface of the regenerated particles. Even when the mineral acid is added in two or more stages, it is homogeneous to set the addition amount so that it takes about 10 to 120 minutes for the pH of the mineral acid to decrease by 1 in the fluctuation of the pH. Preferred for silica composites.

  In the agitation in this reaction step, for example, an unreacted zone is not formed. Therefore, it is preferable to employ an agitation means such as generating a turbulent flow by reversing the agitation blade or providing a baffle plate in the agitation tank.

  The particle diameter of the resulting silica composite regenerated particles is 1.7 to 12.5 μm, more preferably 5.5 to 11.0 μm. When the particle diameter of the silica composite regenerated particles is less than 1.7 μm, the effect of silica composite cannot be sufficiently exhibited, and it is difficult to obtain the effect of improving the oil absorption and opacity. When the particle diameter of the silica composite regenerated particles exceeds 12.5 μm, in the present invention, it becomes close to the average particle diameter of white carbon, can not enter the voids formed by white carbon and pulp fibers, the fixing property is reduced, As a result, the opacity is hardly improved.

  The silica composite regenerated particles preferably contain calcium, silica, and aluminum in a mass% ratio of 30 to 80:10 to 50: 7 to 20 in terms of oxide. This component analysis is a value obtained by performing elemental analysis at an acceleration voltage (15 KV) using an X-ray microanalyzer (model number: E-MAX · S-2150) manufactured by HORIBA, Ltd., and converting it to an oxide from the constituent components.

  Although depending on the volume average particle diameter of the regenerated particles after the pulverization step and the elemental composition of the regenerated particles themselves, the ratio of silica (silicon) in terms of oxide after combining the silica component is 10.0 to 50. By setting the content to 0% by mass, it is possible to improve the printing opacity of newsprint using the obtained silica composite recycled particles.

  The ratio of the silica component is preferably 41.0 to 49.0% by mass, and more preferably 42.0 to 48.0% by mass. If the ratio of the silica component is less than 10.0% by mass, the silica coating is not sufficiently performed. Therefore, the oil absorption and opacity cannot be improved. If the silica component ratio exceeds 50.0% by mass, the silica component is fine. There may be a problem that the silica particles are excessively filled, resulting in a decrease in oil absorption and opacity.

  As an incidental effect of the silica composite, the whiteness is improved by the silica composite. Although white paper opacity tends to decrease due to whiteness improvement, by using silica composite regenerated particles with high oil absorption, absorption dry printing ink for newspaper printing can be held and dried on the paper surface, making it a lightweight newspaper The printing opacity of the paper can be further improved.

  By combining the silica with the regenerated particles, the interfiber bonding is moderately inhibited by the cationic property of the regenerated particles and the anionic property of the silica, and the bulkiness is exhibited.

(Use or application)
The silica composite regenerated particles of the present invention have a large specific surface area because the surface of the porous regenerated particles are originally composited with silica, and when this is used as a filler for internal addition, whiteness and opacity are high. You can also get paper.

  Furthermore, the oil absorption amount of the silica composite regenerated particles is preferably in the range of 50 to 180 ml / 100 g. This is because when the silica composite regenerated particles in this range are used as an internal filler, the silica composite regenerated particles in the paper layer absorb the ink, the organic solvent, etc. impregnated in the paper layer. This is because a decrease in printing opacity is suppressed, and the effect of preventing ink drying and blurring becomes conspicuous by absorbing the ink and the organic solvent. On the other hand, when the oil absorption is less than 50 ml / 100 g, the above effect is not sufficient, and the silica composite regenerated particles may tend to inhibit the ink absorption and drying properties. On the other hand, when the oil absorption exceeds 180 ml / 100 g, there is a case where the ink sinks and the so-called color developability is inferior due to high ink absorbability.

  The oil absorption amount of the silica composite particles can be adjusted by adjusting the reaction temperature, the addition time, the holding time, the pH, the viscosity, the combustion means of the regenerated particles used, the particle diameter, etc. in the silica composite reaction step. When the pore volume of 1,000 Å or less is adjusted to 0.5 to 1.5 cc / g, silica composite regenerated particles that exhibit high oil absorption and can improve paper opacity can be obtained. High opacity can be obtained in the silica composite regenerated particle-containing paper containing regenerated particles.

As mentioned above, the production method of the silica composite regenerated particles has been described in detail by taking regenerated particles as an example. Recycled particle aggregates instead of regenerated particles, and calcium carbonate conventionally used as a filler for papermaking applications (heavy and light) Silica composite inorganic particles can be produced using talc, clay or the like and internally added to newsprint.
Thus, the particle | grains which combined the silica can make a wire wear degree low, since the particle | grain surface is compounded with the silica, and can be used suitably as a filler. Inorganic particles added internally to paper, if the particles are hard, the wire (net part) of the paper machine is liable to be damaged, and the life of the wire is shortened. However, as in the present invention, the life of the wire can be extended by using inorganic particles composited with silica, preferably silica composite regenerated particles or silica composite regenerated particle aggregates, which are soft inorganic particles that do not easily damage the wire.

  The degree of wire wear can be evaluated by a Filcon type wire wear degree test. When regenerated particle aggregates having an abrasion degree of about 80 mg are used as inorganic particles to be combined with silica, particles having a wear degree of about 20 to 70 mg can be lowered by the silica combination, and particles that can be sufficiently used as an internal filler. Can be obtained. In addition, the wire wear degree of heavy calcium carbonate is 100 mg or more, light calcium carbonate is about 50 mg, and white carbon is about 15 mg. If it is about 70 mg or less, it can be used as an internal filler.

  As described above, it is preferable to use composite particles composed of silica and inorganic particles other than silica, preferably silica composite regenerated particle aggregates, as a filler because newspaper paper having high opacity can be obtained.

In order to obtain the base paper constituting the newsprint of the present invention, the pulp slurry made of the pulp is machine chest, for example, preferably pH 6.0 to 10.0, more preferably pH 6.5 to 9.5. After adjusting conditions such as pH to be neutral to alkaline, the filler used in the present invention at the stage before being sent to the seed box, the first fan pump, the cleaner, the screen, and supplied to the next second fan pump After adding, it is possible to improve the yield of filler and improve the optical properties by adopting a method of making paper with a normal paper machine such as a long net paper machine or a twin wire type paper machine through a head box. This is preferable. That is, when the papermaking pH is neutral to alkaline, each fiber tends to swell more easily than in the case of acidity, and the area in which hydrogen bonds are formed between externally fibrillated and internally fibrillated fibers increases. To do. Therefore, in the mesh-like pulp structure composed of cedar wood and pine wood according to the present invention, the neutral newsprint paper has a higher paper strength even if the ash content is the same as that of the acid newsprint paper. As a result, sufficient quality that can withstand high-speed offset printing can be ensured even for newspapers with a low basis weight, such as 35-50 g / m ² .

  Further, in the present invention, when obtaining the base paper, it is possible to add a coagulant in the pulp preparation stage and further add a flocculant in the first stage of the papermaking process following the pulp preparation stage. This is preferable because it promotes agglomeration of fine inorganic particles, further adheres inorganic particles to the raw material pulp to improve filler yield, and improves drainage and wet-end stability.

  The raw material pulp used in the present invention contains mechanical pulp, and since the pulp surface exhibits a relatively high anionic property, a coagulant is added at the pulp preparation stage, and further a papermaking process following the pulp preparation stage. Adding a flocculant in the first stage improves the yield of the filler by physically and chemically adhering the filler between the pulp fibers, and also improves the wet end stability by improving drainage. To preferred.

  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, a cationic organic polymer-based coagulant is preferable because the yield improvement effect of the filler is high. Examples of the cationic organic polymer-based coagulant include one or more amines selected from ammonia, primary amines, secondary amines and tertiary amines, polycationic substances, and weight average molecular weights of 10,000 to 70,000. A polyalkyleneimine modified product obtained by reacting a polyalkyleneimine is preferred. By using the cationic organic polymer coagulant, a paper layer with high opacity can be effectively formed in the combined use of mechanical pulp made of cedar and pine in the present invention and two predetermined fillers.

The solid content of the cationic organic polymer-based coagulant is preferably 0.1 to 1.0 kg / absolutely dried pulp ton, particularly preferably 0.15 to 0.60 kg / absolutely dried pulp ton. When the blending amount of the cationic organic polymer-based coagulant is smaller than the above range, sufficient anion trash coagulation or ionic neutralization effect is not observed, and it is difficult to improve the yield of the filler.
Conversely, if the amount of the cationic organic polymer-based coagulant exceeds the above range, the ionicity in the raw material pulp system becomes excessively cationic, causing unevenness in unnecessary coagulation and size effects, and excessive addition. However, there is a problem in that the yield of filler is deteriorated, and further, a poor texture is developed.
Further, in addition to the cationic organic polymer-based coagulant, an inorganic coagulant such as a sulfuric acid band can be added. The solid content of the inorganic coagulant is preferably 0.3 to 14.0 kg / absolutely dried pulp ton, more preferably 0.5 to 8.0 kg / absolutely dried pulp ton, and 1.0 to 5.0 kg / absolutely dried. Pulpton is particularly preferred.

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

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

  As the flocculant, a cationic flocculant is preferable from the viewpoint of improving the yield of the filler. Specific examples of the cationic flocculant include a cationic polyamine resin, a cationic polyamine polyamide resin, a cationic polyacrylamide, a cationic modified starch, a styrene acrylic resin, and a cationic thermosetting resin. . By adding a cationic flocculant before the paper making process, it is possible to form a paper layer in which mechanical pulp composed of cedar wood and pine wood and two prescribed fillers are intimately contacted with the previous coagulant. The transparency can be further improved.

  The addition amount of the cationic flocculant is preferably 50 to 400 ppm, particularly preferably 80 to 200 ppm in terms of pure content. When the addition amount of the cationic flocculant is smaller than the above range, it is difficult to obtain the effect of improving the yield of talc, white carbon, silica-containing particles, and conversely, when the addition amount of the cationic flocculant exceeds the above range. , There is a risk that the texture will deteriorate. As such a cationic flocculant, for example, the weight average molecular weight is 8 million to 12 million, more preferably 8.5 million to 11 million, and the ratio of the cationic monomer is 5 to 100 mol%, preferably 10 to 100%. A mole% cationic water-soluble polymer or copolymer can be used. Typical examples of such cationic flocculants include PAM. If the weight average molecular weight of the cationic flocculant is less than 8 million, the effect of using the cationic flocculant may not be sufficiently expressed. On the other hand, even if it is larger than 12 million, the desired effect is not much improved. However, there is a risk of high costs.

  It is preferable to apply a surface sizing agent to the front and back surfaces of newsprint after adjusting the paper stock slurry from the raw pulp to make paper. Examples of the surface sizing agent include oxidized starch, etherified starch, esterified starch, enzyme-modified starch, cationized starch, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, polyvinyl alcohol (PVA), styrene / acrylic acid copolymer, styrene / (Meth) acrylic acid copolymer (in addition, (meth) acrylic acid means “acrylic acid and / or methacrylic acid”), styrene / (meth) acrylic acid / (meth) acrylic acid ester copolymer Polymers, styrene / maleic acid copolymers, styrene / maleic acid half ester copolymers, styrene / maleic acid ester copolymers, water-soluble polymers such as polyacrylamide, alkyd resins such as rosin, tall oil and phthalic acid Anionic low content such as saponified products, saponified products of petroleum resin and rosin Compounds, such as cationic polymers, such as Isojianeto polymers and the like, which may 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.

  Among these surface sizing agents, water-soluble polymers are preferable, and starch is particularly preferable.

  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 introduced with an aldehyde group, a carbonyl group, and the like.

In addition, as a weight average molecular weight of starch, 300,000-3 million are preferable. The starch having such a weight average molecular weight improves the absorption drying property by incorporating the solvent component into the paper while keeping the ink component on the paper surface, in addition to the covering property of the paper surface. 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, prevent the filler from falling off, and increase the opacity.

Moreover, it is preferable to use a styrenic polymer together with starch from the viewpoint of further improving the size, compatibility with ink in offset rotary printing, and the effect of preventing the filler from falling off.
When oxidized starch and styrene-based polymer are used as the surface sizing agent, the starch can be applied uniformly, the surface strength can be improved, and the filler can be prevented from falling off. The blending ratio of oxidized starch and styrene-based sizing agent is preferably 10-15 parts of styrene-based sizing agent with respect to 100 parts of oxidized starch as solid content. If the styrenic size is less than 10 parts, it is difficult to sufficiently improve the size and surface strength of the paper, and if it exceeds 15 parts, the cost may increase and the opacity and ink drying may be reduced. is there.

  Examples of the styrenic polymer include a styrene / acrylic acid copolymer and a styrene / (meth) acrylic acid copolymer (wherein (meth) acrylic acid means “acrylic acid and / or methacrylic acid”). Examples include styrene / (meth) acrylic acid / (meth) acrylic acid ester copolymers, styrene / maleic acid copolymers, styrene / maleic acid half ester copolymers, styrene / maleic acid ester copolymers, and the like.

The solid coating amount of surface sizing agent of the newsprint, preferably 0.1 g / ^{m 2} or more 1.0 g / ^{m 2} or less per side, 0.2 g / ^{m 2} or more 0.75 g / ^{m 2} or less Particularly preferred. If the coating amount of the surface sizing agent is smaller than the above range, sufficient film properties cannot be obtained, and it is difficult to sufficiently improve the surface strength. On the other hand, if the coating amount of the surface sizing agent exceeds the above range, a large amount of mist of the coating liquid containing the surface sizing agent will be generated around the coating equipment, fouling the peripheral equipment, and paper breakage due to dirt There is a risk of paper defects.

  The means for applying the surface sizing agent is not particularly limited, and for example, a transfer roll coater, an air doctor coater, a blade coater, a rod coater or the like is used. Among these coaters, a transfer roll coater type coating apparatus is preferable, and a gate roll coater is particularly preferable. Unlike other coating methods, coating by the film transfer method, particularly coating by a gate roll, is suitable for forming a highly coatable layer on the newspaper paper surface even with a low coating amount. Since no rapid shearing force is applied, the coating solution used for circulation is excellent in stability, and a uniform coating can be obtained at high speed. As a result, for example, when multicolor offset rotary printing is performed using a cold set type ink, it is excellent in printability such as ink density, ink setting property, ink setting property, and ink setting property on the surface of newsprint paper can be improved. Therefore, the opacity can be improved by combining the mechanical pulp made of cedar and pine in the present invention and two predetermined fillers.

  Further, the newspaper can be flattened by a calendar facility such as a super calendar, a gloss calendar, or a soft calendar. By performing the flattening process using such a calendar facility, the printability of the newspaper can be further improved. The calender equipment is not particularly limited, but for the newsprint with a high proportion of waste paper pulp, there is a soft calender that has the same tension at a low nip pressure, high smoothness, and thus light weight and color printing suitability. Particularly preferred.

The newspaper according to the present invention thus obtained has a basis weight in accordance with the “basis weight measuring method” described in JIS P 8124, preferably from 35 g / m ^2, from the viewpoint of reducing labor in transportation and reducing weight. As described above, the weight is more preferably 38 g / m ² or more, preferably 50 g / m ² or less, more preferably 48 g / m ² or less. When the basis weight is less than 35 g / m ² , the opacity cannot be secured sufficiently. For example, in recent high-speed printing of 170 to 180,000 copies / hour, paper breaks and wrinkles are likely to occur. May cause problems. On the other hand, if the basis weight exceeds 50 g / m ² , sufficient opacity is easily secured, but it becomes difficult to handle as lightweight newsprint. Since the internally added filler includes white carbon and silica-containing particles having different particle diameters, the silica-containing particles can be fixed in fine voids formed by white carbon and pulp fibers. Furthermore, as a raw material for mechanical pulp, mechanical pulp having a weight ratio of cedar wood chips to pine wood chips of 5:95 or more and 50:50 or less is mechanical pulp having high opacity, strength and bulk. Therefore, by blending the mechanical pulp, newsprint paper that ensures opacity even if it is reduced in weight can be obtained.

Further, the density of the newsprint is 0.56 to 0.70 g / cm ³ measured according to the method described in “Paper and paperboard—Test method for thickness and density” described in JIS P 8118. It is preferable. If the density is less than 0.56 g / cm ³ , the paper strength may be reduced, which may cause a paper break in high-speed rotary printing or a problem that paper dust is generated. On the other hand, if the density exceeds 0.70 g / cm ³ , it becomes easy to cause back-through after printing, and the rigidity may be lowered and the printing workability may be lowered.

  Further, the whiteness of the newsprint is 53% or more, more preferably 54 to 58%, as measured according to “Pulp-Diffusion Blue Light Reflectance (ISO Whiteness) Measurement Method” described in JIS P 8212. Preferably there is. If the whiteness is less than 53%, not only the appearance of the blank paper before printing may be deteriorated, but also the appearance of the printed matter after offset printing, particularly after color printing, may be deteriorated.

  The opacity of the newsprint is preferably 90% to 96% as measured in accordance with “Paper and Paperboard—Opacity Test Method (Paper Backing)” described in JIS P 8149. More preferably, it is 92 to 95%. When the opacity is less than 90%, 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. Mechanical pulp with a blending ratio of cedar wood chips and pine wood chips of 5:95 or more and 50:50 or less as a raw material for mechanical pulp becomes mechanical pulp with high opacity, strength and bulk. By blending the mechanical pulp, newspaper with high opacity can be obtained even if the weight is reduced. Furthermore, the combination of white carbon having a volume average particle diameter of 15 μm or more and 25 μm or less and silica composite regenerated particles in which silica is compounded on the surface of a regenerated particle having a volume average particle diameter of 1.7 μm or more and 12.5 μm or less is thick and long. In addition to paper making of white carbon and silica composite regenerated particles to fill the gap between the pine genus pulp fiber and the thin and short cedar genus pulp fiber, the light-scattering property is improved by improving the filler yield. At the same time, since the light transmittance is lowered, extremely high opacity can be obtained.

  The printing opacity of the newspaper is required to be high because it is difficult to see through during printing, but 90% is preferable as the lower limit measured in accordance with the printing opacity test method described later. 91% is particularly preferable. Further, the upper limit of the printing opacity is preferably 95%, particularly preferably 94%. 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. The paper dust at the time increases and the printing workability decreases. As a raw material for mechanical pulp, mechanical pulp having a blending ratio of cedar wood chips and pine wood chips of 5:95 to 50:50 is a mechanical pulp having high opacity, strength and bulk. Therefore, by blending the mechanical pulp, newsprint with high printing opacity can be obtained even if the weight is reduced. Further, by combining white carbon having a volume average particle diameter of 15 μm or more and 25 μm or less, and regenerated particles having a volume average particle diameter of 1.7 μm or more and 12.5 μm or less and silica composite regenerated particles composed of silica, a thick and long pine In addition to paper making of highly carbon-absorbing white carbon and silica composite recycled particles to fill the gap between the genus-derived pulp fibers and the thin and short cedar-derived pulp fibers, light scattering is achieved by improving the filler yield. In addition, the transparency increases and the light transmission decreases, so that a very high printing opacity can be obtained.

  The tear strength in the horizontal direction of newsprint is measured in accordance with “Paper—Tear Strength Test Method—Elmendorf Tear Test Method” described in JIS P 8116. In view of the workability, it is preferable. If the tear strength (horizontal) is less than 300 mN, there is a risk of paper breakage during offset rotary printing of newsprint paper. As a raw material of mechanical pulp, mechanical pulp having a weight ratio of cedar wood chips to pine wood chips of 5:95 or more and 50:50 or less becomes mechanical pulp having high opacity, strength and bulk. Therefore, the above-mentioned mechanical pulp is blended to make a newsprint with high opacity and tear strength (lateral).

  The tensile strength in the longitudinal direction of the newsprint is preferably 2.6 kN / m or more as measured according to “Paper and paperboard—Testing method for tensile properties” described in JIS P8113. If the tensile strength (longitudinal) is less than 2.6 kN / m, there is a risk of paper breaks and wrinkles occurring during offset rotary printing of newsprint paper. As a raw material of mechanical pulp, mechanical pulp having a weight ratio of cedar wood chips to pine wood chips of 5:95 or more and 50:50 or less becomes mechanical pulp having high opacity, strength and bulk. Therefore, the above-mentioned mechanical pulp is blended to make a newsprint with high opacity and tensile strength (longitudinal).

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

[Production of regenerated particles]
As the material to be processed (raw material), papermaking sludge or deinking floss is used in advance, and after the dehydration process, the manufacturing equipment shown in FIGS. 1 and 2 performs the organic component heat treatment process under the conditions shown in Table 1. A wet pulverization process was performed sequentially using the 1st combustion process and the 2nd combustion process as appropriate to obtain regenerated particles. The internal heat kiln used in the heat treatment process of the organic components in Production Examples 2 and 3 and Production Examples 6 and 7 is an internal heat kiln furnace in which the main body is placed horizontally and rotates around the central axis. The paper flow sludge was supplied from the raw material supply port and hot air was blown into it.

  The internal heat kiln used in the first combustion process is an internal heat kiln furnace in which the main body is placed horizontally and rotates around the central axis. Furthermore, the external heat kiln furnace used in the second combustion process is an external heat kiln furnace in which the main body is placed horizontally and rotates around the central axis, and as this external heat kiln furnace, an external heat having a parallel lifter in particular is provided. An electric kiln furnace was adopted. The wet pulverization process was performed using a ceramic ball mill. The deinking floss in Production Example 4 was used by separating it before the high-grade used paper deinking floss was mixed in the papermaking sludge.

  As the primary combustion temperature, the primary combustion furnace outlet temperature was measured. The secondary combustion temperature was measured at the secondary combustion furnace outlet temperature. As for the oxygen concentration, the primary combustion furnace outlet oxygen concentration and the secondary combustion furnace outlet oxygen concentration were measured.

[Production of silica composite regenerated particles]
Under the conditions shown in Table 2, 38% concentration of sodium silicate solution (No. 3 water glass) and 20% concentration of regenerated particle slurry were mixed as an aqueous solution of alkali silicate, diluted water was added, and it was composed of alkali silicate and regenerated particles as shown in Table 2. After adjusting the slurry to a predetermined reaction start concentration and reaction start pH, sulfuric acid was added as a mineral acid and stirred to produce silica composite regenerated particles. A known mixer is used for stirring the slurry. The pH of the slurry was measured with a pH meter manufactured by Horiba, and the reaction temperature was measured with a known thermometer. In the primary reaction step, the mineral acid was added so that the neutralization rate between the alkali silicate aqueous solution and the mineral acid was as shown in Table 2.

  The holding time refers to the time from the completion of the addition of the mineral acid performed in the primary reaction step to the re-addition of the mineral acid in the secondary reaction step.

  In the secondary reaction step, the same mineral acid as in the primary reaction step was added over a predetermined time so that the reaction completion pH was reached. As shown in Table 2, the 10% concentration slurry viscosity of the finished raw material is a B-type viscometer obtained by subjecting the silica composite regenerated particle slurry that has undergone the reaction through the secondary reaction step to dehydration filtration and adjusting the solid content concentration to 10%. (Measurement temperature 25 ° C.).

[Measurement of regenerated particles and silica composite regenerated particles]
Tables 1 and 3 show the component analysis results of the regenerated particles and the silica composite regenerated particles. The inorganic constituents in each step were subjected to elemental analysis at an acceleration voltage (15 KV) using an X-ray microanalyzer manufactured by Horiba, Ltd., and converted into oxides from the constituents.

  The specific surface area and pore volume were measured using a mercury intrusion porosimeter (“PASCAL 140/240” manufactured by Terumo Corporation) after filtration of the sample and vacuum drying.

The amount of oil absorption is based on the kneading method described in JIS K 5101-13-2. That is, 2 g to 5 g of a sample dried at 105 ° C. to 110 ° C. for 2 hours is taken on a glass plate, and refined linseed oil (oxidized 4 or less) is dropped from the buret little by little to the center of the sample and kneaded with a spatula each time. The dripping and kneading operations are repeated, and the amount of refined linseed oil dripped is determined with the end point when the whole is first assembled into a single rod shape, and the oil absorption is calculated by the following equation.
Oil absorption amount = [linseed oil amount (ml) × 100] / sample (g)

  The particle size is measured when the particle size distribution is measured with a laser particle size distribution measuring device (laser analysis type particle size distribution measuring device “SALD-2200 type” manufactured by Shimadzu Corporation), and the cumulative volume with respect to the volume of all particles is 50%. It is calculated | required as a particle diameter (d50). For the preparation of the measurement sample, silica composite regenerated particles were added to a 0.1% sodium hexametaphosphate aqueous solution and dispersed with an ultrasonic wave for 1 minute.

  An X-ray diffraction apparatus (Rigaku Denki, RAD2X) was used for the measurement of the hard substance. Measurement conditions: Cu-Kα-curved monochromator 40 KV-40 mA, diverging slit 1 mm SS 1 mm RS 0.3 mm, scanning speed 0.8 ° / min, scanning range 2 theta = 7 to 85 degrees, sampling 0.02 degrees.

  The productivity shown in Table 3 indicates that the yield of the silica composite reaction converted from the amount of unreacted chemical contained in the filtrate of the obtained silica composite regenerated particles is ◎, the yield is 95% or more, and 80% or more and less than 95%. 70% or more and less than 80% was evaluated as Δ, and less than 70% was evaluated as ×.

[Manufacture of white carbon]
The white carbon used in the present invention was prepared as follows.
2500 L of sodium silicate aqueous solution, 4800 L of fresh water and 170 kg of anhydrous sodium sulfate adjusted to a concentration of 195 g / L in terms of silicon dioxide (silica) were charged into a reaction vessel having a volume of 10 m ³ .

After the temperature of the solution in the reaction vessel was set to 40 ° C., while stirring, 410 L of sulfuric acid (concentration: 20% by mass) corresponding to 32.5% by mass of the total amount of sulfuric acid necessary for neutralizing sodium silicate was added. Added continuously over a period of minutes. After the addition of sulfuric acid, the reaction solution was heated to 90 ° C. over 35 minutes with stirring, and then aged for 10 minutes at 90 ° C.

Next, the remaining 850 L of sulfuric acid (concentration: 20% by mass) was continuously added over 25 minutes. Further, aging was performed for 20 minutes while maintaining the temperature. Thereafter, sulfuric acid was continuously added to adjust the pH of the slurry to 5.2. The slurry with adjusted pH was filtered and washed, and then wet pulverized to obtain hydrated silicic acid (secondary aggregate). The volume average particle diameter of the obtained white carbon was 20 μm.

In addition, while following the above manufacturing methods, the concentration of the initial sodium silicate aqueous solution, the amount of anhydrous sodium sulfate added, the molar ratio of sodium silicate and sulfuric acid, the reaction temperature, and the addition rate and amount of added chemicals were appropriately changed and adjusted. Then, white carbon having a volume average particle diameter used in Example 10, Example 11, Comparative Example 7, and Comparative Example 8 was produced.

Example 1
Using a mixed tip containing 95% by mass of radiata pine chips and 5% by mass of cedar chips in an absolutely dry mass, defibrating and beating, and using a screen with a slit width of 0.15 mm in the selection process, Mechanical pulp was produced, and this mechanical pulp and deinked waste paper pulp were blended at an absolutely dry mass ratio of 20:80 to obtain a raw material pulp slurry. After adjusting the pH of the pulp slurry to 6 to 7 with a sulfuric acid band, a cationic organic polymer coagulant (Himax SC924, manufactured by Hymo Co., Ltd.) was added in an amount of 0.4 kg / pulpton as a solid content. After adding 0.3 kg (solid content) / pulpton of alkyl ketene dimer sizing agent (product name: AD-1624, manufactured by Nippon PMC Co., Ltd.) to 1 t of the pulp solid content, the silica composite as silica-containing particles Regenerated particles (Production Example 1, volume average particle size 8.5 μm) were added at 30 kg (solid content) / pulptone, and white carbon (volume average particle size 20 μm) was added at 20 kg (solid content) / pulpton. Next, a flocculant having a solid content of 110 ppm (Himo Rock ND270 manufactured by Hymo Co., Ltd.) was added to the absolutely dried pulp, and a base paper having a basis weight of 42.5 g / m ² was obtained with a twin wire paper machine. Furthermore, as a surface sizing agent, oxidized starch and styrene-based polymer (SS2712 manufactured by Starlight PMC Co., Ltd.) are mixed in solid content so that 100 parts of oxidized starch is 30 parts of styrene-based polymer, and water is added to adjust the concentration. After preparing the coating liquid, 0.5 g / m ² per side by dry mass (1.0 g / m ^{2 on} both sides) was applied to obtain the newsprint of Example 1.
In addition, the pulp ton in this invention is an absolutely dry pulp ton.

(Example 2)
Newspaper paper of Example 2 was obtained in the same manner as Example 1 except that 90% by mass of radiata pine chips and 10% by mass of cedar chips were blended.

(Example 3)
Newspaper paper of Example 3 was obtained in the same manner as Example 1 except that 85% by mass of radiata pine chips and 15% by mass of cedar chips were blended.

Example 4
Newspaper paper of Example 4 was obtained in the same manner as in Example 1 except that 80% by mass of radiata pine chips and 20% by mass of cedar chips were blended.

(Example 5)
Newspaper paper of Example 5 was obtained in the same manner as Example 4 except that the volume average particle diameter of the silica composite regenerated particles was 1.7 μm (Production Example 6 shown in Table 3).

(Example 6)
Newspaper paper of Example 6 was obtained in the same manner as in Example 4 except that the volume average particle diameter of the silica composite recycled particles was 5.5 μm (Production Example 2 shown in Table 3).

(Example 7)
Newspaper paper of Example 7 was obtained in the same manner as Example 4 except that the silica composite recycled particles had a volume average particle size of 11.0 μm (Production Example 5 shown in Table 3).

(Example 8)
Newspaper paper of Example 8 was obtained in the same manner as Example 4 except that the silica composite recycled particles had a volume average particle size of 12.5 μm (Production Example 3 shown in Table 3).

Example 9
A newspaper web for Example 9 was obtained in the same manner as Example 4 except that the amount of the silica composite regenerated particles added was 10 kg / pulpton.

(Example 10)
Newspaper paper of Example 10 was obtained in the same manner as Example 4 except that the volume average particle diameter of white carbon was 15 μm.

(Example 11)
Newspaper paper of Example 11 was obtained in the same manner as Example 4 except that the volume average particle diameter of white carbon was 25 μm.

(Example 12)
Newspaper paper of Example 12 was obtained in the same manner as in Example 4 except that the amount of white carbon added was 7 kg / pulpton.

(Example 13)
Newspaper paper of Example 13 was obtained in the same manner as in Example 4 except that the amount of the silica composite regenerated particles added was 5 kg / pulp ton.

(Example 14)
Newspaper paper of Example 14 was obtained in the same manner as Example 4 except that the addition amount of the silica composite regenerated particles was 15 kg / pulp ton.

(Example 15)
Newspaper paper of Example 15 was obtained in the same manner as Example 4 except that the addition amount of silica composite regenerated particles was 15 kg / pulp ton.

(Example 16)
Newspaper paper of Example 16 was obtained in the same manner as in Example 4 except that the amount of white carbon added was 10 kg / pulpton and the amount of silica composite regenerated particles added was 10 kg / pulpton.

(Example 17)
Newspaper paper of Example 17 was obtained in the same manner as Example 4 except that the amount of white carbon added was 16 kg / pulpton and the amount of silica composite regenerated particles added was 25 kg / pulpton.

(Example 18)
Newspaper paper of Example 18 was obtained in the same manner as in Example 4 except that the amount of white carbon added was 30 kg / pulpton and the amount of silica composite regenerated particles added was 40 kg / pulpton.

(Example 19)
Newspaper paper of Example 19 was obtained in the same manner as in Example 4 except that the amount of white carbon added was 40 kg / pulpton and the amount of silica composite regenerated particles added was 55 kg / pulpton.

(Example 20)
Newspaper paper of Example 20 was obtained in the same manner as in Example 4 except that the amount of white carbon added was 45 kg / pulpton.

(Example 21)
Newspaper paper of Example 21 was obtained in the same manner as in Example 4 except that 30 kg / pulpton of silica composite calcium carbonate having a volume average particle size of 8.5 μm was added instead of the silica composite regenerated particles. In addition, the silica composite calcium carbonate is manufactured by using calcium carbonate (trade name: TP-121-6S, manufactured by Okutama Kogyo Co., Ltd., volume average particle diameter 2.1 μm) instead of regenerated particles. Manufactured according to the conditions of

(Example 22)
Newspaper paper of Example 22 was obtained in the same manner as Example 1 except that 75% by mass of Radiata pine chips and 25% by mass of cedar chips were blended.

(Example 23)
Newspaper paper of Example 23 was obtained in the same manner as in Example 1 except that 70% by mass of radiata pine chips and 30% by mass of cedar chips were blended.

(Example 24)
Newspaper paper of Example 24 was obtained in the same manner as in Example 1 except that 60% by mass of radiata pine chips and 40% by mass of cedar chips were blended.

(Example 25)
Newspaper paper of Example 25 was obtained in the same manner as Example 1 except that 50% by mass of radiata pine chips and 50% by mass of cedar chips were blended.

(Example 26)
Newspaper paper of Example 26 was obtained in the same manner as Example 4 except that the screen was carefully selected using a screen having a slit width of 0.20 mm.

(Example 27)
Newspaper of Example 27 was obtained in the same manner as Example 4 except that the blending amount of mechanical pulp was 10% by mass and the blending amount of deinked waste paper pulp was 90% by mass.

(Example 28)
Newspaper paper of Example 28 was obtained in the same manner as Example 4 except that the blending amount of mechanical pulp was 40% by mass and the blending amount of deinked waste paper pulp was 60% by mass.

(Comparative Example 1)
A newsprint of Comparative Example 1 was obtained in the same manner as in Example 1 except that the cedar chip was not blended.

(Comparative Example 2)
Newspaper paper of Comparative Example 2 was obtained in the same manner as in Example 1 except that 97% by mass of radiata pine chips and 3% by mass of cedar chips were blended.

(Comparative Example 3)
Newspaper paper of Comparative Example 3 was obtained in the same manner as in Example 1 except that 40% by mass of radiata pine chips and 60% by mass of cedar chips were blended.

(Comparative Example 4)
A newsprint of Comparative Example 4 was obtained in the same manner as in Example 1 except that Radiatapine was not blended.

(Comparative Example 5)
Newspaper paper of Comparative Example 5 was obtained in the same manner as in Example 4 except that the volume average particle diameter of the silica composite recycled particles was 1.5 μm (Production Example 7 shown in Table 3).

(Comparative Example 6)
Newspaper paper of Comparative Example 6 was obtained in the same manner as in Example 4 except that the volume average particle diameter of the silica composite recycled particles was 18.5 μm (Production Example 4 shown in Table 3).

(Comparative Example 7)
Newspaper paper of Comparative Example 7 was obtained in the same manner as Example 4 except that the volume average particle diameter of white carbon was 5 μm.

(Comparative Example 8)
Newspaper paper of Comparative Example 8 was obtained in the same manner as Example 4 except that the volume average particle diameter of white carbon was 30 μm.

(Comparative Example 9)
Newspaper paper of Comparative Example 9 was obtained in the same manner as Example 4 except that the silica composite regenerated particles were not added.

  About the newsprint and the mechanical pulp slurry of Examples 1-28 and Comparative Examples 1-9, performance evaluation was performed according to the following criteria. Freeness and shive rate are values for mechanical pulp. The results are shown in Table 1.

  [Evaluation]

(1) Volume average particle diameter The volume average particle diameter was measured by a laser analysis type particle size distribution measuring apparatus “SALD-2200 type” manufactured by Shimadzu Corporation.

(2) Silica content of newspaper (as oxide)
The silica content of oxide newspaper (in oxide equivalent) is determined by the X-ray microanalyzer (model number: E-) From the mass ratio of silica converted to oxide in the element converted to oxide obtained by elemental analysis at an acceleration voltage (15 KV) using MAX · S-2150 (manufactured by Horiba Ltd.) It was calculated and obtained.
Silica content of newspaper (oxide equivalent, mass%) = Newspaper ash (mass%) x silica content in ash residue (oxide equivalent, mass%) / 100

(3) Basis weight It measured based on the "basis weight measuring method" of JISP8124.

(4) Ash content Measured according to “Paper, paperboard and pulp-ash content test method” described in JIS P 8251.

(5) Print opacity JAPAN TAPPI No. Measured according to No. 45.

(6) Opacity Measured in accordance with “Paper and paperboard—Opacity test method (backing of paper)” described in JIS P 8149.

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

(8) Density Density was measured according to “Paper and paperboard—basis weight measurement method” described in JIS P 8124 and “Paper and paperboard—test method for thickness and density” described in JIS P 8118.

(9) Tensile strength (longitudinal)
In accordance with “Paper and paperboard—Testing method of tensile properties” described in JIS P 8113, the longitudinal direction of newsprint was measured.

(10) Tear strength (horizontal)
In accordance with “Paper—Tear Strength Test Method—Elmendorf Tear Tester Method” described in JIS P 8116, measurement was performed in the lateral direction of newsprint.

(11) Workability Offset rotary printing press (model number: LITHOPIA BTO-4, manufactured by Mitsubishi Heavy Industries, Ltd.)
Was used to print on 50 series of newsprint. 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.

(12) Freeness (mechanical pulp)
It was measured in accordance with “Pulp freeness test method” described in JIS P 8121 (1995).

(13) Shive rate (mechanical pulp)
In accordance with TAPPI T275sp98, a screen plate having a slit width of 0.15 mm was used, and the sample amount was measured using 100 g of completely dried pulp treated with a flat screen.

  As shown in Tables 4, 5, and 6, the newspapers of Examples 1 to 28 have high opacity (printing opacity and blank paper opacity). When the weight ratio of cedar is increased, the opacity increases, and when white composite particles containing silica composite particles having a volume average particle size smaller than that of white carbon are contained, the opacity is extremely high. Increasing the weight ratio of cedar increases tensile strength as well as opacity, but decreases tear strength. On the other hand, when the weight ratio of cedar is lowered (the weight ratio of radiata pine is increased), the opacity and tensile strength are lowered, and the tear strength is increased. In particular, newsprint paper with a weight ratio of cedar and pine of 15:85 to 25:75 and containing white carbon and silica composite recycled particles exhibits high opacity and satisfies both tensile strength and tear strength. is doing.

  On the other hand, the newspapers of Comparative Examples 1 to 4 have low cedar weight ratio and low opacity, or too high cedar weight ratio and low tear strength. Moreover, since the volume average particle diameter of the silica composite reproduction | regeneration particle | grains is too small and the comparative example 5 becomes difficult to pass through the space | gap in a pulp fiber and is not fixed, opacity does not improve. The newspaper paper of Comparative Example 6 has a volume average particle diameter of the silica composite regenerated particles that is too large to easily enter the voids in the pulp fiber, the opacity is not improved, and the printing workability by removing the filler from the paper surface. Is bad. Further, the newspaper paper of Comparative Example 7 does not improve opacity because the volume average particle diameter of white carbon is smaller than 15 μm and close to the particle diameter of silica composite regenerated particles. Since the volume average particle diameter of white carbon is too large, the newsprint paper of Comparative Example 8 has poor printing workability due to the removal of the filler from the paper surface. It can be seen that the one containing no silica-containing particles (Comparative Example 9) 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.

DESCRIPTION OF SYMBOLS 10 ... Raw material, 12 ... Storage tank, 14 ... 1st combustion furnace (internal heat kiln furnace), 20 ... Hot-air generating furnace, 22 ... Recombustion chamber, 26 ... Heat exchanger, 28 ... Induction fan, 30 ... Chimney, 31 ... External heat jacket, 32 ... second combustion furnace (external heat kiln furnace), 34 ... cooler, 36 ... particle size sorter, 42 ... heat treatment furnace (internal heat kiln furnace), 43 ... hot air generating furnace.

Claims (5)

  As raw material pulp, Cryptomeria wood chips and Pinus wood chips are used as raw materials, and the absolute dry weight ratio between the cedar and pine wood chips is 5:95 or more and 50:50. Newspaper paper comprising mechanical pulp comprising: white carbon having a volume average particle diameter of 15 μm to 25 μm and inorganic particles having a volume average particle diameter of 1.7 μm to 12.5 μm as a filler. .   2. The composite particles according to claim 1, wherein the inorganic particles are silica composite regenerated particles obtained by combining silica with regenerated particles obtained through a dehydration, drying, combustion, and pulverization process using papermaking sludge as a main raw material. Newspaper.   The newsprint according to claim 1 or 2, wherein the content of silica in terms of oxide contained in the newsprint is 4.0% by mass to 7.2% by mass.   The newsprint according to any one of claims 1 to 3, wherein the mechanical pulp is pulp treated with a screen having a slit width of 0.15 mm or less. After blending so that the dry weight blending ratio of cedar and pine wood chips is 5: 95-50: 50 as raw material pulp and mechanical pulping, it is carefully selected with a screen with slit width of 0.15 mm or less 60 to 90% of deinked waste paper pulp is blended with 10 to 40% of the machined pulp, the ash content is 5 to 15% by mass, and the oxide-converted silica content contained in the newspaper is 4.0 to 7.2% by mass. The filler is made by adding white carbon having a volume average particle diameter of 15 μm or more and 25 μm or less and inorganic particles having a volume average particle diameter of 1.7 μm or more and 12.5 μm or less as a filler so as to be mass%. A method for producing newsprint.

Images