JP2012097371A - Newsprint paper and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide newsprint paper that prevents properties such as tensile strength, bulkiness, paper thickness and stiffness from being degraded even when formed of a high blending ratio of recycled pulp.SOLUTION: There is provided newsprint paper containing recycled pulp of 80 mass% or more in its pulp material, in which a paper surface pH is 6.0 to 7.0, and an ash content measured in conformity to JIS P 8251 is 5 to 10 mass%, and a content ratio of calcium is 2 mass% or less.

Description

  The present invention relates to newsprint with a high recycled paper pulp content and a method for producing newsprint.

  At present, recovered newspapers are being systematically collected, and after being recycled into recycled paper pulp, it is used (blended) as a raw material for newsprint pulp. This blending ratio tends to increase particularly in recent years from the viewpoint of effective use of resources, environmental protection, and the like. However, the use of waste paper pulp has the following problems. That is, the pulp fiber becomes brittle due to the regeneration treatment, so that the tensile strength of the newsprint obtained is reduced, and the fibrils are reduced, so that the volume, thickness, waist, etc. of the newsprint obtained are reduced. Then it is a problem. In particular, as the blending ratio of the used paper pulp increases, the blending ratio of the used paper pulp that has been recycled many times increases, and this problem becomes remarkable.

  In addition, a filler is internally added to the newsprint, but in recent years, calcium carbonate tends to be selected as the filler (see, for example, Patent Document 1). Therefore, the combination of the used paper pulp means the presence of the brought-in calcium carbonate, and the higher use of the used paper pulp means an increase in the brought-in calcium carbonate. However, calcium carbonate has a buffer effect and the like as described in the same document, and affects other agents such as inhibiting the fixing performance of sulfate bands. In addition, in the case of acidic papermaking, calcium carbonate is eluted and scales are generated. Therefore, it is necessary to stop the papermaking machine to remove scales and the operability is lowered.

  Therefore, this document states that calcium carbonate is added as much as possible after the paper making process, but in the case of brought-in calcium carbonate, it cannot be solved by such a method. Calcium carbonate is also a kind of filler. When the filler is increased, there arises a problem that the bulk and tensile strength of the resulting newspaper are reduced. Therefore, there arises a problem that the amount of white carbon that is effective for improving the printing opacity, which is also a kind of filler, must be limited.

  Therefore, it is conceivable to reduce the ratio of the carry-in filler by using the waste paper pulp classification method disclosed in Patent Documents 2 to 4. However, according to this method, not only the carry-in filler but also fine fibers are removed, and there arises a problem that the yield (regeneration rate) of waste paper pulp is lowered. It is also conceivable to reduce the carry-in filler by repeating the deinking process etc. in the recycling process of used newspaper. However, the regeneration treatment causes degradation of pulp fibers, decrease in fibrils, etc., resulting in a decrease in the tensile strength, bulk, etc. of the resulting newsprint, and it is difficult to reduce the ratio of brought-in filler only by repeated processing. It is.

Japanese Patent Laid-Open No. 9-078491 JP 2002-180394 A JP-A-2005-9057 JP 2005-42265 A

  The main problem to be solved by the present invention is a newsprint paper in which tensile strength, physical properties such as bulk, paper thickness, waist, etc. are prevented from being deteriorated while wastepaper pulp is highly blended, and a method for producing this newsprint paper. It is to provide.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
80% by mass or more of pulp raw material is newsprint paper that is waste paper pulp,
The paper surface pH is 6.0-7.0,
The ash content measured in accordance with JIS P 8251 is 5 to 10% by mass, and the calcium content calculated by the following formula is 2% by mass or less.
Newspaper that is characterized by that.
Calcium content ratio (oxide conversion, mass%) = the ash content (mass%) × calcium content in the ash content (oxide conversion, mass%) ÷ 100
Here, the calcium content in the ash is obtained by using an X-ray microanalyzer (model number: E-MAX / S-2150, manufactured by Horiba, Ltd.) as a result of ashing the newspaper according to JIS P 8251. It is the value obtained by using and elemental analysis.

(Main effects)
In the range where the paper surface pH is 6.0 to 7.0, for example, calcium is dissolved and removed by adding sulfuric acid, sulfuric acid band, etc., and the ash content measured in accordance with JIS P 8251 is 5 to 10% by mass. On the other hand, by setting the calcium content ratio to 2% by mass or less, the newspaper paper is prevented from being deteriorated in physical properties such as tensile strength, bulk, paper thickness, waist, etc., even though the waste paper pulp is highly blended.

[Invention of Claim 2]
80% by mass or more of the pulp raw material is waste paper pulp, and newsprint paper coated with a surface treatment agent containing a pigment and an adhesive,
The paper surface pH is 6.0-7.0,
The ash content measured according to JIS P 8251 is 10 to 15% by mass, and the calcium content calculated by the above formula is 4% by mass or less.
Newspaper that is characterized by that.

(Main effects)
The surface treatment agent containing the pigment and the adhesive is naturally applied after the paper making process, and the pigment does not affect the paper making. Therefore, when a surface treatment agent is applied, it is sufficient to keep the ash content measured in accordance with JIS P 8251 at 15% by mass or less and the calcium content ratio at 4% by mass or less.

[Invention of Claim 3]
The density measured according to JIS P 8188 is 0.60 to 0.69 g / cm ³ , the tensile strength (longitudinal) measured according to JIS P 8113 is 2.1 to 3.1 kN / m, and JAPAN TAPPI No. Print opacity measured according to No. 45 is 89-94%,
The newsprint according to claim 1 or 2.

(Main effects)
The effect of this invention is mentioned later.

[Invention of Claim 4]
A method for producing newsprint, comprising a slurry preparation step for preparing a raw material slurry from a pulp raw material, and a paper making step for papermaking the raw material slurry, wherein 80% by mass or more of the pulp raw material is used paper pulp. ,
The resulting newsprint has a paper surface pH of 6.0 to 7.0,
The ash content measured according to JIS P 8251 is 5 to 10% by mass, and the calcium content calculated by the above formula is 2% by mass or less.
In the slurry preparation step, at least one of sulfuric acid and a sulfuric acid band is added to the raw slurry.
A method for producing newsprint.

(Main effects)
According to the present invention, it is possible to obtain a newsprint having the same effects as those of the first aspect of the present invention. In addition, since the method of adding at least one of sulfuric acid and sulfuric acid band is adopted in producing the newsprint, calcium carbonate is discharged out of the system in the state of being dissolved in the waste water as calcium ions. There are no problems such as yield reduction due to fiber removal, pulp fiber deterioration due to repeated regeneration treatment, and fibril reduction.

[Invention of Claim 5]
At least one of the sulfuric acid and the sulfuric acid band is added so that the product of the calcium ion concentration and the sulfate ion concentration of the raw material slurry in the slurry preparation step is 300,000 to 3,000,000 ppm.
The method for producing newsprint according to claim 4.

(Main effects)
By adding at least one of sulfuric acid and a sulfuric acid band so that the product of the calcium ion concentration and the sulfate ion concentration is 300,000 to 3,000,000 ppm, generation of calcium sulfate, that is, generation of scaling can be prevented.

  According to the present invention, there are newsprint paper in which deterioration of physical properties such as tensile strength, bulk, paper thickness, waist, and the like is prevented, and a method for producing the newsprint paper, while wastepaper pulp is highly blended.

Next, an embodiment of the present invention will be described.
[Pulp raw material]
The pulp raw material for producing the newsprint of this embodiment contains 80% by mass or more, preferably 90% by mass or more, and more preferably 100% by mass of waste paper pulp. This waste paper pulp includes deinked pulp made from waste paper that has been subjected to printing treatment, and disaggregated pulp made from waste paper waste paper that has not been subjected to printing treatment.

  Examples of used paper include newspaper waste paper, magazine waste paper, flyer waste paper, colored waste paper, Kent waste paper, upper white waste paper, coat waste paper, copy waste paper, and waste paper waste paper, preferably waste paper waste paper. .

  Waste paper pulp can be blended with virgin pulp such as mechanical virgin pulp, chemical virgin pulp, and semi-chemical virgin pulp within a range of less than 20% by mass.

[Slurry preparation process]
In this embodiment, in a slurry preparation step of preparing a raw material slurry from a pulp raw material, at least one of sulfuric acid and a sulfuric acid band, preferably sulfuric acid, is added to the raw material slurry. By adding sulfuric acid or a sulfuric acid band, calcium carbonate dissolves in the waste water and is discharged out of the system together with the waste water. Therefore, the problem that the yield due to the removal of fine fibers is reduced, the problem that the pulp fibers are deteriorated due to the repetition of the regeneration treatment, the problem that the fibrils are reduced, and the like do not occur.

However, excessive addition of sulfuric acid or sulfuric acid band may cause problems such as generation of scaling. Therefore, the amount of sulfuric acid or sulfuric acid band added is measured in accordance with JIS P 8251 so that the resulting newspaper has a pH of 6.0 to 7.0, preferably 6.4 to 6.7. The ash content is 5 to 10% by mass, preferably 6 to 8% by mass, and the calcium content calculated by the following formula is 2% by mass or less, preferably 0.7 to 1.8% by mass, more preferably Is performed so that it may become 0.8-1.6 mass%. Note that these conditions do not have to be realized only by adding sulfuric acid or a sulfuric acid band. For example, in the case of ash, the above conditions may be satisfied with a separate filler added.
Calcium content ratio (oxide conversion, mass%) = the ash content (mass%) × calcium content in the ash content (oxide conversion, mass%) ÷ 100

  Here, the calcium content in the ash is obtained by using an X-ray microanalyzer (model number: E-MAX / S-2150, manufactured by Horiba, Ltd.) as a result of ashing the newspaper according to JIS P 8251. It is the value obtained by using and elemental analysis.

  Here, the pH of the paper is measured using a reagent (MPC-BCP: pH 4.8 to 6.8, MPC-CR: pH 6.8 to 8.8) with a pH measurement kit for paper (manufactured by Kyoritsu Riken). It is a value measured visually with a discoloration standard meter.

  When added so that the pH of the paper surface is less than 6.0, sulfuric acid and sulfuric acid band react with calcium carbonate to produce carbon dioxide and calcium sulfate, which may cause scale trouble due to adhesion of calcium sulfate in the papermaking system. . Moreover, there exists a possibility that tensile strength may fall because papermaking pH falls. On the other hand, when added so that the paper surface pH exceeds 7.0, the effect of reducing calcium carbonate in ash is low, and as a result, the proportion of ash is increased, and the bulk and waist may be lowered. Moreover, if ash is added so as to be less than 5% by mass, the resulting newsprint may have insufficient opacity and may cause a calcium sulfate scale trouble. On the other hand, if the ash content is added so as to exceed 10% by mass, the resulting newspaper may have insufficient tensile strength, and the bulk and waist may be reduced. Furthermore, when the calcium content is added so as to be less than 0.7% by mass, a scale trouble due to calcium sulfate may occur. On the other hand, when the calcium content is added to exceed 2.0% by mass, the bulk and waist are lowered, the problem that the tensile strength is lowered due to the increase in ash content, the problem that the papermaking chemicals are not good, etc. It can happen.

  Further, it is preferable that the sulfuric acid or sulfuric acid band is added so that the product (ion product) of the calcium ion concentration and the sulfate ion concentration of the raw material slurry is 300000 to 3000000 ppm, preferably 450,000 to 1000000 ppm. The ionic product always changes depending on the amount of calcium carbonate brought in and the amount of sulfuric acid and sulfuric acid band to be added. By setting this ionic product within the above range, calcium ions can be sufficiently removed, and scaling can be reduced. Occurrence can be prevented. Furthermore, an increase in white water concentration in the wire part is suppressed and an improvement in retention can be achieved by making the ash content 5 to 10% by mass while the ion product is 300000 to 3000000 ppm. In addition, the tensile strength is improved and the printing opacity tends to decrease, but it can be compensated by adding white carbon or the like, which has a higher printing opacity improvement effect than calcium carbonate.

  In this embodiment, sulfuric acid or a sulfuric acid band can be used as a chemical for dissolving calcium carbonate, but it is preferable to use sulfuric acid, particularly dilute sulfuric acid having a concentration of less than 4% by mass. Sulfuric acid is inexpensive and does not have a function as a coagulant such as a sulfuric acid band (aluminum sulfate), so even if the amount added is increased or decreased, it has little influence on the yield of fine fibers and other chemicals.

  The addition of sulfuric acid or sulfuric acid band does not have to be performed once, and can be performed in two, three or more times. By adding in multiple portions, precipitation such as pitch due to pH shock is prevented, and the concentration of sulfuric acid and sulfuric acid band is partially increased, and it reacts with calcium carbonate excessively to precipitate calcium sulfate scale. Can be prevented. Furthermore, when added in multiple portions, the calcium ion concentration and the sulfate ion concentration can be easily controlled. When the addition of sulfuric acid or a sulfuric acid band is performed in a plurality of times, the sulfuric acid or the sulfuric acid band can be added, for example, in a feed tank and a subsequent compounding box. When sulfuric acid is used, a fixing agent such as a sulfuric acid band or a filler such as white carbon can be added in a machine chest at the latter stage of the blending box. According to this embodiment, since the sulfuric acid band is added in a state where calcium carbonate is dissolved and removed by the addition of sulfuric acid, the generation of scale is prevented.

  For measurement of the ion product of the raw slurry, it is preferable to use an apparatus that emphasizes ease of measurement rather than measurement accuracy. For example, DIGITAL WATER ANALYZER (Lambda 9000) manufactured by Kyoritsu Riken Corporation may be used. it can. By using a device that is easy to measure and increasing the number of additions and the measurement frequency, dissolution of calcium carbonate can be promoted more reliably, and scale formation can also be prevented.

  In the above, the calcium ion concentration is usually 300 to 1000 ppm, preferably 450 to 550 ppm, and the sulfate ion concentration is usually 1000 to 3000 ppm, preferably 1000 to 2500 ppm. The calcium ion concentration was determined by using a lambda 9000 from Kyoritsu Riken Co., Ltd., with the measurement principle being the phthalein complexone method and reagent type LR-Ca-B Reagent No. It is a value measured using 48. The sulfate ion concentration was determined by using a lambda 9000 manufactured by Kyoritsu Riken Co., Ltd., the measurement principle being barium sulfate turbidimetry, reagent type LR-SO4, reagent no. This is a value measured using 16.

  In this embodiment, a filler can be added in a range where the ash content measured in accordance with JIS P 8251 is 10% by mass or less. As this filler, in addition to white carbon, for example, calcium carbonate such as heavy calcium carbonate and light calcium carbonate, clay such as talc, kaolin clay, and delaminated clay, inorganic such as titanium dioxide, synthetic silica, and aluminum hydroxide Synthetic polymer fine particles such as filler, polystyrene resin, urea formaldehyde resin and the like can be used.

  In addition, the raw material slurry with internal filler (appropriately added) as appropriate includes, for example, starch, vegetable gum, aqueous cellulose derivative, paper strength enhancer such as sodium silicate, rosin, starch, carboxymethylcellulose, Polyvinyl alcohol, alkyl ketene dimer, alkenyl succinic anhydride, neutral rosin and other internal sizing agents, polyacrylamide, copolymers thereof, yield improvers such as sodium silicate, dyes such as dyes and pigments Additives to be used can be added as long as the object of the present invention is not impaired.

[Paper making process, etc.]
The raw material slurry prepared in the slurry preparation step is used as newsprint through a paper making step, a drying step, a smoothing step, and the like. The raw slurry papermaking may be acidic papermaking, neutral papermaking, or alkaline papermaking, but is preferably neutral papermaking with a pH of 6.0 to 7.5. As the paper machine, a known paper machine such as a long net paper machine, a circular net paper machine, an on-top former, or a gap former can be used.

  In this embodiment, a surface treatment agent not containing a pigment can be applied to the surface of paper obtained by papermaking, drying, or the like, if necessary (coating step). Examples of the surface treatment agent include starches such as corn, potato, tapioca, wheat and rice, starches such as modified starch obtained by subjecting these starches to oxidation treatment and enzyme treatment, polyvinyl alcohol, polyacrylamide and the like. Polymer materials and the like can be blended. Moreover, various adjuvants, such as an antifoamer, a water-resistant agent, a surface sizing agent, an antiseptic | preservative, can also be mix | blended with this surface treating agent, for example.

  The solid content concentration of the surface treatment agent is not particularly limited, and can be adjusted to, for example, 2 to 25% by mass depending on the coating apparatus, the coating amount, and the like.

The coating amount of this surface treatment agent (in terms of dry solid content, per side) can be 0.4 to 3.0 g / m ² , preferably 0.7 to 2.5 g / m ² . If the amount of the surface treatment agent applied is too small, the effect of the application may not be obtained. On the other hand, when the coating amount of the surface treatment agent exceeds 3.0 g / m ² , not only the cost becomes high, but also the adhesiveness called “Nepari” is developed when the surface of the newsprint becomes wet. This may lead to poor printability.

  In this coating step, a surface treatment agent containing a pigment and an adhesive can also be applied (different from the surface treatment agent in that it contains a pigment). By applying a surface treatment agent containing a pigment, the smoothness of the paper surface is improved and the printability is improved. The application of the surface treatment agent containing the pigment changes the ash content and calcium content measured in accordance with JIS P 8251. However, the surface treatment agent containing the pigment is naturally applied after the paper making process, and the pigment does not affect the paper making raw material. Therefore, when applying the surface treating agent containing a pigment, it is sufficient to keep the ash content measured in accordance with JIS P 8251 at 15% by mass or less and the calcium content at 4% by mass or less. In addition, Preferably ash content is 10 mass% or more.

  Examples of the pigment in the surface treatment agent include calcium carbonate such as heavy calcium carbonate and light calcium carbonate, clay such as talc, kaolin clay, and delaminated clay, and inorganic such as titanium dioxide, synthetic silica, and aluminum hydroxide. Synthetic polymer fine particles such as particles, polystyrene resin, urea formaldehyde resin and the like can be used.

  Examples of the adhesive in the surface treatment agent containing a pigment include starch made from corn, potato, tapioca, wheat, rice, etc., modified starch obtained by subjecting these starches to oxidation treatment, enzyme treatment, etc. Starch, synthetic polymer compounds such as polyvinyl alcohol, polyacrylamide, synthetic resin latex such as styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl methacrylate-butadiene copolymer, natural rubber latex, etc. be able to. Furthermore, various auxiliary agents, such as an antifoamer, a water-resistant agent, a surface sizing agent, and a preservative, can be added to the surface treatment agent as necessary.

  The solid content concentration (pigment concentration) of the surface treatment agent is not particularly limited, but is preferably adjusted to 15 to 40% by mass.

The coating amount of the surface treatment agent containing a pigment (in terms of dry solid content, per side) can be 0.3 to 2.0 g / m ² , preferably 0.5 to 1.5 g / m ² . If the coating amount of the surface treatment agent is too small, it is difficult to obtain sufficient smoothness, and there is a possibility that the effect of improving the ink deposition property cannot be obtained. On the other hand, when the coating amount of the surface treatment agent exceeds 2.0 g / m ² , not only the cost becomes high, but also when the surface of the newsprint becomes wet, it expresses adhesiveness called nepariness. It may lead to a decrease in printability.

  The surface treatment agent can be applied to the paper surface by a size press such as a blade metering size press or a rod metalling size press, or a coater such as a gate roll coater, a blade coater, a bar coater, a rod coater or an air knife coater.

[Newspaper]
Newsprint of this embodiment, JIS P 8188 density 0.60~0.69g / cm ^3, as measured in accordance with, and preferably suitable that is 0.63~0.66g / cm ^3. If the density is less than 0.60 g / cm ³ , the paper strength decreases, which may cause paper breakage in high-speed rotary printing, and paper dust may be generated. May be reduced. On the other hand, if the density is more than 0.69 g / cm ³ , it becomes easy to cause a back-through after printing, and the bulk and waist may be lowered, and the printing workability and hand feeling may be lowered.

  The newsprint of this embodiment preferably has a tensile strength (longitudinal) measured in accordance with JIS P 8113 of 2.1 to 3.1 kN / m, preferably 2.2 to 2.8 kN / m. . If the tensile strength is less than 2.1 kN / m, troubles such as paper breakage may occur in high-speed rotary printing, and color misregistration may occur during color printing because the paper tends to stretch. There is. On the other hand, in order to produce the tensile strength to exceed 3.1 kN / m, it is necessary to increase the amount of paper strength enhancer, etc., which may lead to an increase in cost and high strength kraft pulp. If the blending ratio of is increased, the opacity may decrease.

  The newspaper of this form is JAPAN TAPPI No. The printing opacity measured according to No. 45 is 89 to 94%, preferably 90 to 93%. If the printing opacity is less than 89%, there is a possibility of show-through. On the other hand, if the printing opacity exceeds 94%, it is necessary to increase the amount of filler. However, increasing the amount of filler causes a decrease in tensile strength, generation of paper dust, etc. May be out of balance.

  The newsprint of this embodiment is suitable when the opacity measured according to JIS P 8149 (blank paper) is 90 to 95%, preferably 92 to 94%. If the opacity is less than 90%, not only the appearance of the blank paper is deteriorated but also the back-through may occur. On the other hand, if the opacity exceeds 95%, it is necessary to increase the amount of filler. However, increasing the amount of filler causes a decrease in tensile strength, generation of paper dust, etc. There is a possibility that balance may be lost.

  The newspaper of this embodiment has a paper thickness measured according to JIS P 8118 of 65 to 75 μm, preferably 67 to 72 μm. When the paper thickness is less than 65 μm, sufficient bulkiness cannot be obtained, and there is a possibility that the newspaper will have no hand feeling, and there is a possibility that the newspaper will be difficult to fold. On the other hand, if the paper thickness exceeds 75 μm, the paper is too bulky and may be clogged in a high-speed rotary printing machine, or a paper break may occur.

The newspaper of this embodiment has a basis weight measured according to JIS P 8124 of 42 to 49 g / m ² , preferably 43 to 48 g / m ² , more preferably 43 to 45 g / m ^2. . If the basis weight is less than 42 g / m ² , the opacity may be insufficient, and paper breaks and wrinkles occur in recent high-speed rotary printing of 170 to 180,000 copies / hour. There is a possibility that it becomes easy to do. In this respect, the opacity can be improved by increasing the amount of filler, but as described above, the increase in the amount of filler may cause a decrease in tensile strength, generation of paper dust, and the like. On the other hand, if the basis weight exceeds 49 g / m ² , it may not be possible to reduce labor in transportation.

[Others]
The method for producing waste paper pulp to be blended with the pulp raw material in this embodiment is not particularly limited, but a method in which the deinking process is a multi-stage of two or more stages, for example, a disaggregation process, a rough selection process, a first deinking process, It is preferable that the process proceeds in the order of the selection process and the second deinking process. According to this step, the ash content can be reduced to about 15% by mass, and the ash content can be reliably reduced to 10% by mass or less by adding sulfuric acid or a sulfuric acid band in the subsequent stage. Of course, if the deinking process is multi-staged with two or more stages, the deinking rate is increased, and the whiteness of the obtained waste paper pulp and newsprint is also increased. Further, according to this method, since the bleaching step can be omitted, it is possible to prevent degradation of pulp fibers caused by bleaching and a decrease in opacity due to lignin elution.

  In order to confirm the effects of the newsprint according to the present invention and the manufacturing method thereof, the following various samples were prepared, and tests for evaluating the quality of these samples were performed. In addition, in a present Example, the numerical value which shows a mixing | blending, a density | concentration, etc. is a numerical value of solid content or the mass reference | standard of an active ingredient. Moreover, since the pulp, chemical | medical agent, etc. which are shown in a present Example are only examples, it cannot be overemphasized that this invention is not restrict | limited by these Examples, and can be selected suitably.

Using a pulp slurry consisting of 100% waste paper pulp, the concentration of calcium ions and sulfate ions in the pulp slurry at the inlet of the paper making process will be the values shown in Table 1. Diluted sulfuric acid having a concentration of 4% by mass was added to the blending box, and papermaking was performed with a twin wire type paper machine. Diluted sulfuric acid was added after adjusting concentrated sulfuric acid (manufactured by Sumitomo Chemical) with water. Furthermore, using oxidized starch and a styrene polymer (SS2712 manufactured by Seiko PMC Co., Ltd.) as a surface treatment agent (a surface treatment agent not containing a pigment), the styrene polymer is 30 parts by mass with respect to 100 parts by mass of the oxidized starch. After mixing so as to be part by mass and adjusting the concentration by adding water to prepare a coating solution for surface treatment, 0.5 g / m ² per side (1.0 g / m ^{2 on} both sides) is applied in terms of dry mass. The surface treatment was applied to obtain a test piece, and various tests were performed on this test piece. Preparation methods, measurement conditions, and the like were in accordance with Table 1 and the conditions shown below. In Examples 1 to 5 as a filler, white carbon was added to the solid pulp in a solid content of 1.5%, and in Comparative Examples 1 to 3, a solid content of 1.0% was added.

(Sulfuric acid)
Concentrated sulfuric acid (manufactured by Sumitomo Chemical Co., Ltd.) diluted with water and adjusted to 4% by mass was added.

(Calcium ion concentration)
Lambder 9000 from Kyoritsu Institute of Physical and Chemical Research, reagent type LR-Ca-B reagent No. 48 is a value measured using the phthalein complexone method as the measurement principle.

(Sulfate ion concentration)
Lambder 9000 of Kyoritsu Riken, Inc., reagent type LR-SO4 as a reagent, reagent No. 16 is a value measured using the barium sulfate turbidimetric method as the measurement principle.

(Calcium content)
It is the value calculated by the following formula.
Calcium content ratio (oxide conversion, mass%) = the ash content (mass%) × calcium content in the ash content (oxide conversion, mass%) ÷ 100

  Here, the calcium content in the ash is obtained by using an X-ray microanalyzer (model number: E-MAX / S-2150, manufactured by Horiba, Ltd.) as a result of ashing the newspaper according to JIS P 8251. It is the value obtained by using and elemental analysis.

(Basis weight)
It was measured according to “basis weight measuring method” described in JIS P 8124: 1998.

(Paper thickness)
It was measured according to “Paper and paperboard—Test method for thickness and density” described in JIS P 8118: 1998.

(ash)
It was measured according to “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method” described in JIS P 8251: 2003.

(Page pH)
Using a reagent (MPC-BCP: pH 4.8 to 6.8, MPC-CR: pH 6.8 to 8.8) with a pH measurement kit for paper (manufactured by Kyoritsu Riken), visually check with a discoloration standard meter Measured at

(Whiteness)
It was measured according to “Pulp-Diffusion Blue Light Reflectance (ISO Whiteness) Measurement Method” described in JIS P 8212: 1998.

(Blank paper opacity)
It was measured according to “Paper and paperboard—Opacity test method (paper backing)” described in JIS P 8149: 2000.

(Print opacity)
JAPAN TAPPI No. 45: 2000, and measured according to “Newspaper paper—post-printing opacity test method”.

(Tensile strength (longitudinal))
It was measured in accordance with “Constant speed extension type tensile test method” described in JIS P 8113: 2006.

(Scaling evaluation)
After one month of use, the inside of the approach pipe was visually observed and evaluated based on the following evaluation criteria.
A: No scaling occurs on the entire pipe surface.
○: Scaling slightly occurs on a part of the pipe surface, but there is no practical problem.
Δ: Scaling is observed on the entire pipe surface.
X: Scaling of the entire surface of the pipe is remarkable, and the number of engraving defects increases.
Of the above evaluation criteria, ◎ and ○ are judged to be actually usable.

  INDUSTRIAL APPLICABILITY The present invention can be applied as a newsprint with a high recycled paper pulp composition and a method for producing newsprint.

Claims (5)

80% by mass or more of pulp raw material is newsprint paper that is waste paper pulp,
The paper surface pH is 6.0-7.0,
The ash content measured in accordance with JIS P 8251 is 5 to 10% by mass, and the calcium content calculated by the following formula is 2% by mass or less.
Newspaper that is characterized by that.
Calcium content ratio (oxide conversion, mass%) = the ash content (mass%) × calcium content in the ash content (oxide conversion, mass%) ÷ 100
Here, the calcium content in the ash is obtained by using an X-ray microanalyzer (model number: E-MAX / S-2150, manufactured by Horiba, Ltd.) as a result of ashing the newspaper according to JIS P 8251. It is the value obtained by using and elemental analysis. 80% by mass or more of the pulp raw material is waste paper pulp, and newsprint paper coated with a surface treatment agent containing a pigment and an adhesive,
The paper surface pH is 6.0-7.0,
The ash content measured according to JIS P 8251 is 10 to 15% by mass, and the calcium content calculated by the above formula is 4% by mass or less.
Newspaper that is characterized by that. The density measured according to JIS P 8188 is 0.60 to 0.69 g / cm ³ , the tensile strength (longitudinal) measured according to JIS P 8113 is 2.1 to 3.1 kN / m, and JAPAN TAPPI No. Print opacity measured according to No. 45 is 89-94%,
The newsprint according to claim 1 or 2. A method for producing newsprint, comprising a slurry preparation step for preparing a raw material slurry from a pulp raw material, and a paper making step for papermaking the raw material slurry, wherein 80% by mass or more of the pulp raw material is used paper pulp. ,
The resulting newsprint has a paper surface pH of 6.0 to 7.0,
The ash content measured according to JIS P 8251 is 5 to 10% by mass, and the calcium content calculated by the above formula is 2% by mass or less.
In the slurry preparation step, at least one of sulfuric acid and a sulfuric acid band is added to the raw slurry.
A method for producing newsprint. At least one of the sulfuric acid and the sulfuric acid band is added so that the product of the calcium ion concentration and the sulfate ion concentration of the raw material slurry in the slurry preparation step is 300,000 to 3,000,000 ppm.
The method for producing newsprint according to claim 4.