JP6091309B2 - Newspaper - Google Patents

Description

  The present invention relates to newsprint.

  From the viewpoint of effective use of resources and environmental protection, the recycling of used paper is progressing. In particular, for newsprint, it is desired that the mixing ratio of used paper pulp approaches 100% by mass. However, newsprint is made mainly from recycled newsprint pulp that has been recycled many times, so the pulp fibers become brittle, and the higher the percentage of wastepaper pulp, the lower the tensile strength required in high-speed rotary printing. There is an inconvenience.

In recent years, weight reduction of newsprint is promoted in terms of resource conservation and transport cost reduction, a basis weight of ultra-light paper 43 g / m ² is the mainstream accounting for about 85% of newsprint domestic production . Recently, there is a demand for further reduction to save resources. However, when waste paper pulp is used extensively, fibrils necessary for entanglement of pulp fibers are reduced, so that sufficient volume cannot be obtained. There is an inconvenience that the paper cannot be reduced.

  Under such circumstances, newspaper paper has been proposed that uses raw fiber pulp that uses only the long fibers by classification treatment and the ratio of the remaining 42 mesh components in the sieving test is less than 50%. JP 2005-9057 A and JP 2005-42265 A). According to these newsprints, the use of waste paper pulp containing only long fibers can suppress the decrease in tensile strength, and can exhibit strength and printability that can withstand high-speed rotary presses. It is said that the white paper opacity can be increased by using raw material pulp having a component ratio of less than 50%. However, while these newsprint papers use only long fibers as waste paper pulp, the ratio of the remaining 42 mesh components is less than 50%, so the upper limit is set. In this case, sufficient bulk cannot be obtained. In addition, there is room for improvement in terms of effective utilization of waste paper pulp to remove short fibers.

JP-A-2005-9057 JP 2005-42265 A

  The present invention has been made in view of the above circumstances, and although the recycled paper pulp in the total pulp has a high blending ratio of 90% by mass or more and a low basis weight, it is bulky and has tensile strength, blank paper opacity, and printing. An object of the present invention is to provide a newsprint having high opacity, excellent printability, and particularly suitable for high-speed offset printing.

  In order to obtain a paper that is bulky and excellent in tensile strength, the present inventors need to use a certain amount of relatively long fiber waste paper pulp, while the factors that lower blank paper opacity and tensile strength are particularly long fibers. The present inventors found that it is present in the components and arrived at the present invention.

That is, the invention for solving the above problems is
Newspaper paper having a waste paper pulp content of 90% by mass or more and a basis weight of 35 g / m ² or more and 43 g / m ² or less with respect to the total pulp,
The disaggregated pulp disaggregated according to JIS-P8220 (1998) “pulp-disaggregation method” is 710 μm according to JIS-P8207 (2009) “pulp-sieving test method”. In the degree of sieving (%), the sieve mesh opening of the second tank is 355 μm, the sieve mesh opening of the third tank is 180 μm, and the sieve mesh opening of the fourth tank is 106 μm. The ratio of (C ₁ ) is 20% or less, and the ratio of the second tank residue (C ₂ ) is 20% or more.

In the newsprint, the content of a particularly long fiber component, specifically, the ratio of the first tank residue (C ₁ ) in the sieving pulp screening test is reduced to 20% or less. According to the newsprint, high blank paper opacity and tensile strength can be provided by reducing the content of such fiber components. The reason why the blank paper opacity and the tensile strength are increased by reducing the content of the particularly long fiber component in this way is not clear, but for example, such a particularly long fiber has a non-uniformly large gap in the base paper. It is presumed that the presence of this void reduces opacity and strength. Moreover, the newsprint, by the ratio of the second Sozan (C ₂₎ of the macerating the pulp 20% or more, it is possible to increase the bulk and tensile strength. Furthermore, since the newsprint paper can use waste paper pulp without undergoing special classification treatment, it is excellent in productivity and recyclability.

The proportion of the fourth tank passage (C ₅ ) in the sieving degree (%) is preferably 20% or more. By increasing the content of the short fiber component in this way, the short fibers can fill the voids in the base paper, and the white paper opacity can be further increased.

  It is preferable that content of the pulp which shows the color of mechanical pulp in the said disaggregated pulp is 40 to 70 mass%. In this way, by increasing the content of used paper pulp derived from mechanical pulp, the bulk, tensile strength, and the like can be further increased.

  The newspaper paper preferably has a paper thickness of 65 μm to 70 μm, a tensile strength of 2.1 kN / m to 3.1 kN / m, and a blank paper opacity of 92% to 96%. The newsprint is thus bulky despite its low basis weight and high wastepaper pulp content, and is excellent in tensile strength and blank paper opacity.

  As described above, the newsprint of the present invention has a high content of 90% by weight or more of waste paper pulp in all pulp, and is bulky without performing pulp classification treatment, despite having a low basis weight. In addition, it has excellent tensile strength, blank paper opacity, printing opacity and printability, and can be suitably used particularly for high-speed offset printing.

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

<Newspaper>
The newsprint of the present invention is usually obtained by papermaking a pulp slurry containing pulp and filler.

(pulp)
In the present invention, waste paper pulp is used as the main raw material of the pulp. The content of waste paper pulp in the total pulp in the newspaper is 90% by mass or more, preferably 95% by mass or more, and more preferably 100% by mass. By setting the content of the used paper pulp in the total pulp within the above range, it is possible to improve the printability such as the ink setting property and the recyclability such as the effective use of resources.

  Waste paper pulp, for example, tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, corrugated waste paper, upper white waste paper, Kent waste paper, imitation waste paper, ground ticket waste paper, etc. Examples include disaggregation / deinked waste paper pulp (DIP) and disaggregation / deinking / bleached waste paper pulp.

  Among these waste paper pulp, newspaper waste paper pulp derived from newspaper waste paper and magazine waste paper pulp derived from magazine waste paper are preferable, and it is more preferable to use a mixture of newspaper waste paper pulp and magazine waste paper pulp. Newspapers and magazines have a high recovery rate of used paper, and the raw material pulp and magazines that make up newsprint and magazine paper are similar in each paper manufacturer. Yes. In particular, newsprint, which is used as a raw material for newspaper wastepaper pulp, generally contains 50% or more of wastepaper pulp, has low virgin mechanical pulp and kraft pulp content, and various virgin pulps are used. However, since it is once paper-made and used paper pulp by used paper processing, the properties of newspaper waste paper pulp are homogenized. In addition, since the used magazine paper contains a lot of mechanical pulp with little fatigue and relatively low ash content, newsprint paper with excellent bulk and tensile strength can be obtained.

  Examples of virgin pulp include hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), conifer unbleached kraft pulp (NUKP), hardwood semi-bleached kraft pulp (LSBKP), conifer Chemical pulp such as semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, coniferous sulfite pulp, etc .; Mechanical pulp (MP) such as mechanical pulp (TMP); pulp chemically or mechanically produced from non-wood fibers such as kenaf, hemp, and straw.

  Among these virgin pulps, mechanical pulp (MP) having a high effect of complementing the decrease in bulk when used paper pulp is preferable, and thermomechanical pulp (TMP) suitable for adjusting used paper pulp is particularly preferable.

  Moreover, as content of the magazine waste paper pulp in the said waste paper pulp, 10 to 40 mass% is preferable, and 15 to 30 mass% is more preferable. If the content of the magazine waste paper pulp in the waste paper pulp exceeds the above upper limit, the magazine waste paper has a large number of printing surfaces, so that the deinking efficiency is lowered, which may reduce the whiteness and tensile strength of the newspaper. On the other hand, when the content of the magazine waste paper pulp in the waste paper pulp is less than the lower limit, the bulk and tensile strength of the newsprint may be lowered. Most preferably, the remaining waste paper pulp is all newspaper waste paper pulp. In addition, the above-mentioned used magazine paper means the return and the remaining copies of magazines, etc. generated by households, companies, government offices, etc. that conform to the “Recycled Paper Recycling Promotion Center“ Statistical Classification and Major Brands of Used Paper ”. Specifically, for example, a weekly magazine, a monthly magazine, a book, a telephone book, and the like can be given. In recent years, it has become possible to selectively collect used paper under the required conditions by improving the collection accuracy of used paper. In particular, among the above-mentioned weekly magazines, monthly magazines, book books, telephone books, and other magazine waste papers, JIS-P8120 (1998) among the disaggregated pulps disaggregated according to JIS-P8220 (1998) “pulp-disaggregation method”. The content of pulp showing the coloration of mechanical pulp measured in accordance with “Paper, paperboard and pulp-fiber composition test method” is as high as 85% by mass or more, and the waste paper is JIS-P8220 (1998) “pulp -The disaggregated pulp disaggregated according to the "disaggregation method" 2 Pulp filtered and dried with filter paper (manufactured by Advantech Toyo Co., Ltd.) ash content rate measured according to “paper, paperboard and pulp-ash content test method—525 ° C. combustion method” described in JIS-P8251 (2003) It is possible to selectively collect the above-mentioned magazine waste paper having a low value of 18% or less, and it is particularly preferable to use these.

The newsprint is in accordance with JIS-P8220 (1998) “pulp-disaggregation method” and the first tank according to JIS-P8207 (2009) “pulp-sieving test method” of disaggregated pulp obtained by disaggregating the newsprint. Sieve mesh size of 710 μm, sieve mesh of the second tank is 355 μm, sieve mesh of the third tank is 180 μm, and sieve mesh of the fourth tank is 106 μm. %) Of the first tank residue (C ₁ ) is 20% or less, and the ratio of the second tank residue (C ₂ ) is 20% or more, in particular, the ratio of the first tank residue (C ₁ ). Is preferably 5% or more and 20% or less, and the ratio of the second tank residue (C ₂ ) is preferably 25% or more and 50% or less, and the ratio of the first tank residue (C ₁ ) is 7% or more and 15% or less, 45% proportion 30% or more of the second Sozan _{(C 2)} than More preferably. When the ratio of the first tank residue (C ₁ ) in the sieving pulp sieving test exceeds the above upper limit, large gaps are likely to be generated in the newsprint, and the blank opacity and tensile strength of the newsprint may be reduced. The ratio of the second Sozan (C ₂₎ in the sieving test the fragmenting pulp of less than the above lower limit, there is a possibility that the bulk and the tensile strength of the newsprint is reduced. The degree of sieving can be adjusted by, for example, the type of used paper that is a raw material of used paper pulp, the blending amount, the degree of beating of the pulp, and the like. In particular, by setting the content of the magazine waste paper pulp in the waste paper pulp to 10% by mass or more and 40% by mass or less, the numerical value range of the sieving degree can be obtained, which is preferable.

In the newsprint, the ratio of the fourth tank passage (C ₅ ) of the degree of sieving (%) in the disaggregated pulp is preferably 20% or more and 30% or less, and more preferably 22% or more and 28% or less. Preferably, it is 24% or more and 26% or less. When the proportion of the sieving degree (%) in the disaggregated pulp in the fourth tank passage (C ₅ ) is less than the above lower limit, the content of the short fiber pulp may be reduced to reduce the blank opacity of the newspaper. There is. The degree of sieving can be adjusted by, for example, the type of used paper that is a raw material of used paper pulp, the blending amount, the degree of beating of the pulp, and the like. In particular, when the content of the magazine waste paper pulp in the waste paper pulp is 10% by mass or more and 40% by mass or less, the sieving degree can be obtained, which is preferable.

  Moreover, as a ratio of the mechanical pulp contained in the pulp of the newsprint, JIS-P8120 (1998) among the disaggregated pulp obtained by disaggregating the newsprint according to JIS-P8220 (1998) “pulp-disaggregation method”. The pulp content showing the coloration of mechanical pulp measured according to "Paper, paperboard and pulp-fiber composition test method" is preferably 40% by mass or more and 70% by mass or less, and 43% by mass or more and 60% by mass. % Or less is more preferable. If the content of pulp showing the color of mechanical pulp exceeds the above upper limit, the surface strength of the newsprint may be lowered. On the other hand, when the content of pulp showing the color of mechanical pulp is less than the lower limit, the bulk and tensile strength of the newsprint may be reduced. The ratio of the mechanical pulp can be adjusted by, for example, the type and blending amount of used paper that is a raw material of the used pulp and the blending amount of the mechanical pulp. In particular, the content of the used paper pulp in the used paper pulp is preferably 10% by mass or more and 40% by mass or less, so that the mechanical pulp content can be obtained.

  As the freeness measured in accordance with JIS-P8121 (1995) "pulp freeness test method" of disaggregated pulp obtained by disaggregating the newspaper according to JIS-P8220 (1998) "pulp-disaggregation method" It is preferably 200 ml or more and 370 ml or less, more preferably 230 ml or more and 350 ml or less, and further preferably 250 ml or more and 330 ml or less. If the freeness exceeds the upper limit, the entanglement between the fibers decreases, and the tensile strength of the newsprint may be reduced. On the other hand, if the freeness is less than the lower limit, the hand feeling may be reduced due to the decrease in bulk. In addition, the said freeness can be adjusted by changing the kind and compounding quantity of a raw material pulp, the grade of the beating of a pulp, etc., for example.

(Filler)
A filler can be blended in the pulp slurry. The filler is not particularly limited, and examples thereof include titanium dioxide, calcium carbonate, kaolin, talc, hydrated silicon, white carbon, and regenerated particles.

  Among these, white carbon and regenerated particles are preferable as fillers to be added to the pulp slurry, and regenerated particles derived from newspaper deinking floss are more preferable. Thus, by using regenerated particles derived from white carbon or newspaper deinking floss as a filler, it is possible to improve the whiteness and printing opacity of the newsprint, which has a high content of waste paper pulp, and the whiteness tends to decrease. .

In particular, the disaggregated pulp disaggregated according to JIS-P8220 (1998) “pulp-disaggregation method” conforms to JIS-P8207 (2009) “pulp-sieving test method”, and the sieve mesh of the first tank is opened. In the sieving degree (%) measured as 710 μm, the sieve mesh opening of the second tank is 355 μm, the sieve mesh opening of the third tank is 180 μm, and the sieve mesh opening of the fourth tank is 106 μm. In addition to the ratio of the remaining (C ₁ ) being 20% or less and the ratio of the second tank remaining (C ₂ ) being 20% or more, by using recycled particles derived from newspaper deinking floss as a filler, Despite having a high blending ratio of 90% by mass or more and a low basis weight, a newspaper paper having a high bulkiness, high tensile strength and high white paper opacity, and excellent printability is preferable. Hereinafter, regenerated particles derived from newspaper deinking floss will be described.

[Recycled particles from newspaper deinking floss]
Recycled particles derived from newspaper deinking floss are obtained by dewatering and heat-treating paper sludge made mainly from newspaper deinking floss. Since such regenerated particles derived from newspaper deinking floss have a relatively small particle size compared with white carbon or the like, when they are internally added as a filler, they can easily stay between fibers and improve the opacity of newsprint paper. In addition, the regenerated particles having a small particle size and an indefinite shape are easily entangled with the waste paper pulp fiber that has become brittle due to repeated use and has a high yield. In addition, since the regenerated particles having a small particle size and an indefinite shape are difficult to inhibit the entanglement between pulp fibers, it is possible to suppress a decrease in tensile strength. Moreover, since the regenerated particles derived from newspaper deinking floss are porous, they are preferable because they become bulky newsprint when used as a filler.

  The regenerated particles derived from the newspaper deinking floss are preferably particles having metakaolin and hydrous magnesium silicate as main components and at least a part of the surface of the core is coated with calcium carbonate.

  The content of calcium carbonate in the regenerated particles derived from newspaper deinking floss is preferably 70% by mass or more, and more preferably 80% by mass or more. When the content of calcium carbonate in the regenerated particles derived from newspaper deinking floss is less than the above-mentioned value, the oil absorption and whiteness of the regenerated particles derived from newspaper deinking floss decrease, resulting in the opacity and whiteness of the newspaper. May decrease. The content of calcium carbonate in the regenerated particles derived from newspaper deinking floss is controlled by the content of the newspaper deinking floss used as a raw material and the conditions of the carbon dioxide blowing step in the method for producing regenerated particles derived from newspaper deinking floss described later. can do.

  The content of calcium carbonate in the regenerated particles derived from newspaper deinking floss is included in the regenerated particles at an acceleration voltage of 15 KV using, for example, an X-ray microanalyzer (model number: E-MAX · S-2150) manufactured by Horiba Seisakusho. It can be calculated by obtaining the oxide-converted mass ratio of various elements and performing proportional calculation based on this result and the molecular weights of calcium carbonate, kaolin, talc and silicon dioxide.

  The whiteness of the regenerated particles derived from newspaper deinking floss is preferably 80% or more, more preferably 84% or more, and still more preferably 86% or more. When the whiteness of the regenerated particles derived from newspaper deinking floss is less than the above value, the whiteness of the newspaper may be lowered.

  The oil absorption amount of the regenerated particles derived from newspaper deinking floss is preferably 60 mL / 100 g or more and 150 mL / 100 g or less, and more preferably 70 mL / 100 g or more and 130 mL / 100 g or less. If the oil absorption amount of the regenerated particles derived from newspaper deinking floss exceeds the above upper limit, the ink sinks and so-called color developability may be lowered. On the other hand, if the oil absorption amount of the regenerated particles derived from newspaper deinking floss is less than the above lower limit, the ink vehicle or organic solvent cannot be sufficiently absorbed, and the drying property and blurring preventing effect of the ink may be reduced. There is.

  The average particle size (volume average particle size) of the regenerated particles derived from newspaper deinking floss is preferably 2 μm or more and 15 μm or less, and more preferably 3 μm or more and 10 μm or less. If the average particle size of the regenerated particles derived from newspaper deinking floss exceeds the above upper limit, the bond strength between pulp fibers may decrease and paper strength may decrease, and it may easily fall off after papermaking and cause an increase in paper dust. There is a fear. On the other hand, when the amount is less than the above lower limit, the effect of coating with calcium carbonate may not be sufficiently exhibited.

  The abrasion degree of the regenerated particles derived from newspaper deinking floss is preferably 150 mg or less, more preferably 125 mg or less, and even more preferably 100 mg or less. When the abrasion degree of the regenerated particles derived from newspaper deinking floss exceeds the above numerical value, the operability may be lowered.

[Method for producing regenerated particles derived from newspaper deinking floss]
(material)
Papermaking sludge is used as a raw material for recycled particles derived from newspaper deinking floss, and the main raw material of this papermaking sludge is newspaper deinking floss. Newspaper deinking floss is a floss separated when deinking pulp derived from newspaper wastepaper, and does not include a floss separated when deinking pulp other than newspaper wastepaper. In recent years, newspaper deinking floss has a tendency to have a relatively high amount of calcium carbonate and a relatively small amount of kaolin due to the fact that the paper used in the production of newsprint has become neutral paper making. The ratio exceeds 70% by mass, and the kaolin ratio changes at less than 30% by mass. Therefore, if the main raw material for papermaking sludge is newspaper deinking floss, the amount of cementitious material produced from calcium oxide and kaolin is reduced, and the resulting white particles are hardened and slurried. The problem of thickening and solidifying is improved. In the production of newspaper deinked pulp, in order to continuously obtain newspaper deinked pulp of stable quality, newspapers of a certain quality that have been selected tend to be used as raw materials. It tends to be stable. Therefore, if newspaper deinking floss is used as the main raw material, regenerated particles having high oil absorption and whiteness can be stably obtained. As a result, it is possible to stabilize the quality of the newsprint that internally contains the regenerated particles derived from the newspaper deinking floss as a filler, and at the same time improve the opacity and whiteness of the newsprint. The newspaper deinking floss has a low ash content and contains oil-derived fats and carbon black. Therefore, the fuel in the heat treatment process described later can be reduced.

  70 mass% or more is preferable and, as for content of the calcium carbonate in the inorganic particle in papermaking sludge, 80 mass% or more is more preferable. When the content of calcium carbonate in the inorganic particles in the papermaking sludge is less than the above value, precipitation (coating) of calcium carbonate in the carbon dioxide blowing step described below becomes insufficient, and the whiteness and oil absorption amount of the obtained regenerated particles As a result, the whiteness and opacity of the newsprint may be reduced.

  The content of calcium carbonate in the inorganic particles in the papermaking sludge is obtained by burning the papermaking sludge at 525 ° C. to produce a combustion product, for example, an X-ray microanalyzer (model number: E-MAX · S-2150) manufactured by Horiba, Ltd. By using the acceleration voltage of 15 KV to obtain oxide-converted mass ratios of various elements contained in the combustion product, and performing proportional calculation based on this result and the molecular weight of calcium carbonate, kaolin, talc and silicon dioxide Can be calculated.

  The content of newspaper deinking floss in the entire papermaking sludge is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more in terms of solid content. When the content of newspaper deinking floss in the entire papermaking sludge is less than the above value, the whiteness and oil absorption of the regenerated particles obtained may decrease due to a decrease in the content of calcium oxide contained in the papermaking sludge. In addition, the recycling rate of used newspaper is reduced.

  The content of kaolin in the entire inorganic particles in the newspaper deinking floss is preferably less than 20% by mass, and the ratio of other inorganic particles is preferably 80% by mass or more. The kaolin in the entire inorganic particles in the newspaper deinking floss More preferably, the content of is less than 20% by mass and the content of calcium carbonate is 80% by mass or more. By setting the contents of kaolin and calcium carbonate in the newspaper deinking floss within the above range, the regenerated particles obtained can be prevented from being hardened and regenerated particles having excellent whiteness can be obtained. In addition, among the inorganic particles, talc is classified into silicate mineral and clay mineral like kaolin, but it does not decompose at the combustion temperature in the heat treatment process described later and does not affect the hardening of regenerated particles. Is treated as the content of inorganic particles other than kaolin. Further, in order to make the contents of kaolin and calcium carbonate in the newspaper deinking floss within the above-mentioned range, the coated paper containing a large amount of kaolin may be selected and adjusted from the newspaper used as a raw material.

  The papermaking sludge can contain other raw materials in addition to the above-mentioned newspaper deinking floss as long as the effects of the present invention are not impaired. Examples of other raw materials include industrial wastewater (washing water, white water, surplus wastewater sludge, etc.), sludge discharged in the papermaking raw material preparation process, magazine deinking floss, and the like. However, since the above-mentioned magazine deinking floss is mainly made of coated paper (used paper) and contains a large amount of kaolin, the use of magazine deinking floss as a raw material for papermaking sludge can easily produce cementitious substances. Become. Therefore, it is preferable not to use magazine deinking floss as a raw material for papermaking sludge. When using magazine deinking floss, special attention should be paid to the calcium carbonate ratio and kaolin ratio. Specifically, for example, by mixing papermaking sludge generated from neutral papermaking process using calcium carbonate, or by mixing papermaking sludge such as washing water of calcium carbonate storage tank or screen cake, the ratio of calcium carbonate is increased. It is better to raise it relatively.

(Dehydration process)
The dewatering step is a step of removing the moisture of the papermaking sludge to a predetermined ratio. A known dehydrator or the like may be used for dehydration. The moisture content of the papermaking sludge after dehydration is preferably 30% by mass to 60% by mass, more preferably 30% by mass to 50% by mass, and further preferably 35% by mass to 45% by mass. If the moisture content of the papermaking sludge after dehydration exceeds the above upper limit, combustion unevenness is likely to occur in the heat treatment step described later, and the fuel required in the heat treatment step increases, which may increase the cost. On the other hand, when the moisture content of the paper sludge after dehydration is less than the above lower limit, the floc after dehydration becomes hard and the particle size of the regenerated particles may easily vary.

  The dehydration step is preferably performed in multiple stages. Examples of the multistage dehydration step include a method in which the moisture content of the papermaking sludge is set to 65% by mass or more and 90% by mass or less using a screen and then dehydrated to the target moisture content using a screw press. Thus, by making a dehydration process into a multistage, the loss | disappearance of inorganic particles, such as a filler contained in papermaking sludge, can be suppressed and it can prevent that the floc after dehydration becomes hard.

The above moisture content of the papermaking sludge is a value calculated by the following formula using the constant temperature dryer as the mass after drying when the sample is held at 105 ° C. for 6 hours or more and no change in mass is observed. is there.
Moisture content (%) = [(mass before drying−mass after drying) ÷ mass before drying] × 100

(Crushing process)
The papermaking sludge after dehydration can be crushed by a pulverizer (or pulverizer) prior to heat treatment in the heat treatment step. The average particle diameter of the papermaking sludge after the crushing step is preferably 2.5 mm or more and 12.5 mm or less, more preferably 2.5 mm or more and 7.0 mm or less, and further preferably 2.5 mm or more and 4.0 mm or less. When the average particle diameter of the papermaking sludge exceeds the above upper limit, it becomes difficult to uniformly heat-treat the papermaking sludge from the surface portion to the core portion. On the other hand, when the average particle diameter of the papermaking sludge is less than the lower limit, excessive heat treatment is likely to be performed in the subsequent heat treatment step.

  In addition, the average particle diameter of the papermaking sludge is obtained by measuring the mass of each sample obtained by classification with sieves having different eye holes, and the total of the measured values corresponds to 50% by mass of the whole. It is a size of a hole, and is a value measured using a metal plate sieve based on JIS-Z8801-2: 2000.

(Heat treatment process)
The papermaking sludge is then subjected to a heat treatment step. Although this heat treatment step can be carried out continuously with one apparatus, it is preferably carried out separately in a drying step and a combustion step. Hereinafter, the drying process and the combustion process will be described in detail.

(Drying process)
As a drying apparatus used in the drying step, a known apparatus may be used, and examples thereof include a stalker furnace, a fluidized bed furnace, a cyclone furnace, a kiln furnace, and an airflow drying apparatus.

  The drying temperature is preferably 200 ° C. or higher and 600 ° C. or lower, more preferably 200 ° C. or higher and 450 ° C. or lower, and further preferably 200 ° C. or higher and 300 ° C. or lower. If the drying temperature exceeds the above upper limit, overcombustion may occur, which may cause unintended thermal decomposition of organic substances. On the other hand, when the drying temperature is lower than the lower limit, the papermaking sludge is not sufficiently dried, and the decomposition of calcium carbonate contained in the papermaking sludge into calcium oxide may be reduced.

  The moisture content of the paper sludge after drying is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less. When the moisture content of the papermaking sludge after drying exceeds the above numerical value, combustion unevenness is likely to occur in the combustion process described later, and the decomposition of calcium carbonate contained in the papermaking sludge into calcium oxide may be reduced.

  By providing the drying step in advance as described above, the organic components contained in the papermaking sludge are gradually burned, and the regenerated particles obtained by suppressing the pulverization of the papermaking sludge can easily have the same particle size. As a result, it is possible to uniformly promote the decomposition of calcium carbonate contained in the papermaking sludge in the combustion process, which will be described later, into calcium oxide, and to suppress thickening when the obtained regenerated particles are slurried. it can.

(Combustion process)
A known apparatus may be used as the combustion apparatus used in the combustion process, and examples thereof include a stalker furnace, a fluidized bed furnace, a cyclone furnace, and a kiln furnace. Among these, a horizontal rotary kiln furnace is preferable, and an internal heat kiln furnace with high thermal efficiency is more preferable.

  The combustion temperature is preferably 750 ° C. or higher and 900 ° C. or lower, more preferably 800 ° C. or higher and 900 ° C. or lower, and further preferably 800 ° C. or higher and 850 ° C. or lower. If the combustion temperature exceeds the above upper limit, excessive fuel is required, which may be uneconomical. On the other hand, when the combustion temperature is lower than the lower limit, the papermaking sludge is not sufficiently combusted and the decomposition of calcium carbonate contained in the papermaking sludge is reduced, and the precipitation of calcium carbonate is reduced in the carbon dioxide blowing step described later. There is a fear.

  The oxygen concentration in the combustion step is preferably 3% by volume or more and 18% by volume or less, more preferably 4% by volume or more and 15% by volume or less, and further preferably 5% by volume or more and 12% by volume or less. If the oxygen concentration during the combustion process exceeds the upper limit, oxygen may be supplied more than necessary, which may be uneconomical. On the other hand, when the oxygen concentration during the combustion process is less than the lower limit, the papermaking sludge is insufficiently combusted and the decomposition of calcium carbonate contained in the papermaking sludge into calcium oxide may be reduced.

  In the combustion process, the decomposition rate of calcium carbonate contained in papermaking sludge into calcium oxide is preferably 80% by mass or more, and more preferably 90% by mass or more. When the decomposition rate of calcium carbonate contained in papermaking sludge into calcium oxide is less than the above value, the coating of the surface of the regenerated particles with calcium carbonate may be reduced in the carbon dioxide blowing step described later. Newspaper deinking floss, which is the main raw material for papermaking sludge, has a low kaolin content, so even when burned, it produces little cementitious material derived from kaolin. Therefore, the decomposition of calcium carbonate can be advanced as much as possible. By decomposing calcium carbonate into calcium oxide in the combustion process, it is possible to promote the coating of the surface of the regenerated particles with calcium carbonate in the carbon dioxide blowing process described later.

  The decomposition rate of calcium carbonate to calcium oxide was measured using a measuring instrument (model TG / DTA6200) manufactured by SII Nano Technology, Inc., with a heating rate of 20 ° C./min, a supply gas of air (oxygen concentration of about 5 volumes) %), Supply gas flow rate: a value measured under measurement conditions of 48 ml / min.

  It is preferable to pulverize the papermaking sludge after the combustion process (hereinafter also referred to as “combusted product”) to make the particle diameters uniform. By combusting the combusted material to make the particle diameter uniform, slurrying can be performed uniformly in a slurrying step described later. The average particle size of the combusted product after pulverization is preferably 1 μm to 50 μm, more preferably 1.5 μm to 30 μm, and even more preferably 2 μm to 20 μm. When the average particle diameter of the combusted product after pulverization exceeds the above upper limit, slurrying in the slurrying step described later is not uniform, and it may be difficult to adjust the viscosity of the slurry. On the other hand, when the average particle diameter of the combustion product is less than the lower limit, the particles may be too small to be handled easily.

  As the pulverizer, a known pulverizer may be used. Examples thereof include dry pulverizers such as jet mills and high-speed rotary mills: wet pulverizers such as attritors, sand grinders, and ball mills.

The average particle diameter of the burned product is a volume average particle diameter (D ₅₀ ) measured using a laser diffraction particle size distribution meter (model number: Microtrac MT-3000II, manufactured by Nikkiso).

(Slurry process)
The combustion product is then subjected to a slurrying process. The slurrying step is a step of mixing the combustion product with water to form a slurry. By this slurrying, the calcium oxide in the combustion product is eluted into water and becomes an aqueous calcium hydroxide solution. Note that the combusted material before the slurrying is preferably an aggregate.

  The concentration of the combustion product contained in the slurry is preferably 2% by mass or more and 25% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less in terms of solid content. If the concentration of the combustion product contained in the slurry exceeds the above upper limit, the viscosity of the slurry becomes too high, and the slurry may solidify or the efficiency of the carbon dioxide blowing process described later may be reduced. On the other hand, when the concentration of the combustibles contained in the slurry is less than the lower limit, the precipitation of calcium carbonate in the carbon dioxide blowing step described later is reduced, the dehydration efficiency after the carbon dioxide blowing step is lowered, and the productivity is reduced. May decrease.

(CO2 blowing process)
The carbon dioxide blowing step is a step in which carbon dioxide is blown into the slurry of the combustion product to deposit calcium carbonate on the surface of the combustion product (regenerated particles). Hereinafter, this mechanism will be described.

When calcium carbonate and kaolin are burned at high temperatures, calcium carbonate is decomposed into calcium oxide, and kaolin reacts with calcium oxide and silicic acid to produce various hydrated hard substances. However, when newspaper deinking floss is used to increase the proportion of calcium carbonate relatively and lower the proportion of kaolin, the proportion of calcium oxide that does not originate from hydrated hard substances (does not react with kaolin) increases. The calcium oxide (CaO) becomes calcium hydroxide (Ca (OH) ₂ ) by slurrying the combustion product. Therefore, the slurry of the combustion product contains OH ⁻ exhibiting strong alkalinity as represented by the following formula (1).
Ca (OH) ₂ → Ca ²⁺ + 2OH ⁻ (1)
When carbon dioxide (CO ₂ ) is blown into this slurry, calcium carbonate (CaCO ₃ ) is precipitated as shown in the following formula (2), and the pH is lowered.
Ca ²⁺ + 2OH ⁻ + CO ₂ → CaCO ₃ + H ₂ O (2)
Thus, the surface of the papermaking sludge which has a metakaolin and hydrous magnesium silicate as a main component is coat | covered with calcium carbonate, and the whiteness of the reproduction | regeneration particle | grains obtained can be improved.

  The concentration of carbon dioxide blown is preferably 5% by volume to 30% by volume, more preferably 10% by volume to 30% by volume, and still more preferably 20% by volume to 30% by volume. If the concentration of carbon dioxide to be blown exceeds the above upper limit, calcium carbonate having a columnar or needle-like crystal structure may precipitate, resulting in an excessive particle size. On the other hand, when the concentration of carbon dioxide to be blown is less than the above lower limit, calcium carbonate is not sufficiently precipitated and regenerated particles having sufficient whiteness may not be obtained.

  Through the above process, regenerated particles derived from newspaper deinking floss are obtained. Recycled particles derived from this newspaper deinking floss are composed mainly of particles containing metakaolin and hydrous magnesium silicate, and at least a part of the surface of the core is coated with calcium carbonate. Unlike conventional regenerated particles that are simply agglomerated, they have excellent whiteness. Further, since calcium carbonate covering the surface of the regenerated particles is light calcium carbonate having high oil absorption, it has a high oil absorption. Further, the regenerated particles derived from newspaper deinking floss have few knife edges and are excellent in wire wear.

  The amount of the regenerated particles derived from the newspaper deinking floss in the newspaper is preferably 1% by mass or more and 9% by mass or less, more preferably 2% by mass or more and 7% by mass or less in terms of solid content with respect to the raw material pulp. . If the added amount of the regenerated particles derived from the newspaper deinking floss exceeds the upper limit, the regenerated particles become excessive, the amount of filler that falls off in the production process or the printing process increases, and there is a risk that paper dust may be generated or the strength may be reduced. is there. On the other hand, when the added amount of the regenerated particles derived from the newspaper deinking floss is less than the lower limit, the regenerated particles are insufficient, and there is a risk that sufficient opacity and oil absorption may not be obtained or whiteness may not be improved. There is.

  The volume average particle diameter of the filler is preferably from 0.1 μm to 20 μm, more preferably from 1 μm to 15 μm. When the volume average particle diameter of the filler exceeds the above upper limit, the entanglement between the pulp fibers is weakened, and the paper strength may be reduced. On the other hand, when the volume average particle diameter of the filler is less than the lower limit, the yield decreases and the ash content decreases, so that the printing opacity of the newspaper may decrease. Moreover, the voids of the pulp fiber cannot be filled sufficiently, and the surface strength may be reduced.

  As content of a filler, 1 mass% or more and 9 mass% or less are preferable in conversion of solid content with respect to raw material pulp, and 3 mass% or more and 7 mass% or less are more preferable. When the filler content exceeds the above upper limit, the filler becomes excessive, and the generation of paper dust may increase, or the surface strength of the newspaper may decrease. On the other hand, when the filler content is less than the above lower limit, the whiteness and opacity of the newsprint may be reduced.

<Other additives>
In addition to the above pulp and filler, the pulp slurry contains internal additives such as starch, polyacrylamide, epichlorohydrin and other paper strength enhancers, rosin, alkyl ketene dimer, ASA (alkenyl succinic anhydride), neutral rosin and the like. A sizing agent, a coagulant such as a sulfuric acid band or polyethyleneimine, and a flocculant such as polyacrylamide or a copolymer thereof can be added.

<Quality etc.>
The basis weight of the newsprint is a 35 g / ^{m 2} or more 43 g / ^{m 2} or less, preferably 37 g / ^{m 2} or more 42 g / ^{m 2} or less. If the basis weight of the newsprint exceeds the above upper limit, it goes against the recent weight saving and resource saving. On the other hand, when the basis weight of the newsprint is less than the lower limit, sufficient opacity and strength cannot be obtained, and printing on a high-speed offset rotary printing press may be difficult.

  The thickness of the newspaper is preferably 65 μm or more and 70 μm or less, and more preferably 66 μm or more and 69 μm or less. If the paper thickness exceeds the above upper limit, there is a risk that it will violate the request for weight reduction. On the other hand, if the paper thickness is less than the above lower limit, the tensile strength may decrease.

  The tensile strength of the newspaper is preferably 2.1 kN / m or more and 3.1 kN / m or less, and more preferably 2.3 kN / m or more and 2.7 kN / m or less. When the tensile strength exceeds the above upper limit, the paper thickness increases, which may be contrary to the demand for weight reduction. On the other hand, when the tensile strength is less than the above lower limit, the occurrence of paper breaks or the like increases, and it may not be possible to cope with printing conditions such as offset printing.

  The blank paper opacity of the newsprint is preferably 92% to 96%, more preferably 94% to 96%. If the blank paper opacity exceeds the above upper limit, the necessary fillers and the like increase, which may reduce the economic efficiency. On the other hand, when the blank paper opacity is less than the above value, there is a possibility that the showthrough is likely to occur.

Density of the newsprint is preferably 0.60 g / cm ³ or more 0.70 g / cm ³ or less, 0.61 g / cm ³ or more 0.68 g / cm ³ or less is more preferable. When the density exceeds the above upper limit, workability may be reduced due to a decrease in rigidity. On the other hand, if the density is less than the above numerical value, there is a possibility that the showthrough is likely to occur.

  The ash content of the newspaper is preferably 5% or more and 15% or less, and more preferably 7% or more and 13% or less. If the ash content exceeds the above upper limit, the surface strength may decrease. On the other hand, when the ash content is less than the lower limit, sufficient tensile strength may not be obtained.

  The printing opacity of the newspaper is preferably 91.0% or more and 95.0% or less, and more preferably 91.5% or more and 94.0% or less. If the printing opacity is less than the lower limit, there is a possibility that a show-through occurs during printing.

  The whiteness of the newspaper is preferably 53% or more, and more preferably 54% or more. When the whiteness is less than the above lower limit, printed characters or the like are difficult to identify, and there is a risk of causing eye strain on the subscriber.

<Method of manufacturing newsprint>
(Deinking process)
In the newsprint of the present invention, the waste paper pulp in the total pulp is 90% by mass or more, and this waste paper pulp contains a large amount of magazine waste paper pulp. The weekly and monthly magazines from which this magazine waste paper pulp originates have many printed surfaces, so that the deinking performance in the deinking process in the waste paper pulp manufacturing process is likely to deteriorate. For this reason, in the newsprint paper manufacturing method, it is preferable to deink waste paper by the flotation method. The flotation method is a pulper that works with alkali and other deinking agents to break up old paper, peels the ink from the pulp fibers to produce pulp slurry, and blows air into the pulp slurry to form bubbles. In this method, the peeled ink is attached to the foam, and the ink is removed together with the foam.

  The deinking agent used in the deinking process is not particularly limited, and a known deinking agent can be used. Examples of such a deinking agent include fatty acid-based deinking agents and higher alcohol-based deinking agents. Can be mentioned.

  Examples of fatty acid deinking agents include myristic acid, pentadecanoic acid, palmitic acid, marigaric acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, stearolic acid, ricinoleic acid, ricinoelaidic acid, nonadecanoic acid Arachidic acid, heneicosanoic acid, behenic acid, brassic acid, erucic acid, tricosanoic acid, tetracosanoic acid, beef tallow fatty acid, rapeseed oil fatty acid, fish oil fatty acid, etc. These may be used alone or in combination. May be.

  Examples of the higher alcohol used in the higher alcohol deinking agent include isostearyl alcohol, oleyl alcohol, octyldodecanol, chimyl alcohol (glyceryl monocetyl ether), cholesteryl (cholesterin), sitosterol (sitosterin), stearyl alcohol. , Cetanol (cetyl alcohol, palmityl alcohol), cetostearyl alcohol, cerakil alcohol (monooleyl glyceryl ether), decyl tetradecanol, batyl alcohol (glyceryl monostearyl ether), phytosterol (phytosterin), hexyl decanol, behenyl alcohol, lauryl Examples include alcohol, lanolin alcohol, hydrogenated lanolin alcohol, and the like. It may be mixed and used.

  The addition amount of the deinking agent is preferably 2.1 kg / t or more and 3.3 kg / t or less, more preferably 2.3 kg / t or more and 3.1 kg / t or less in solid content with respect to the absolutely dry pulp. When the addition amount of the deinking agent exceeds the above upper limit, the yield may decrease due to excessive foaming, and the production cost may increase. On the other hand, when the addition amount of the deinking agent is less than the above lower limit, a sufficient deinking effect may not be obtained, and the whiteness of the waste paper pulp may be reduced, and glue applied to the back cover of a magazine or the like The adhesive foreign matter cannot be removed, and the quality of the pulp may be deteriorated.

  The proportion of the fatty acid-based deinking agent contained in the deinking agent is preferably 15% by mass or more and 30% by mass or less, and more preferably 20% by mass or more and 25% by mass or less. If the proportion of the fatty acid-based deinking agent contained in the deinking agent exceeds the above upper limit, the effect obtained with respect to the added amount may be reduced and the cost may be increased. On the other hand, when the ratio of the fatty acid-based deinking agent contained in the deinking agent is less than the above lower limit, the effect of suppressing foaming by the higher alcohol-based deinking agent is lowered, and thus the yield may be deteriorated.

  The pH of the disaggregated pulp slurry in the deinking treatment is preferably 8.0 or more and 9.5 or less, and more preferably 8.3 or more and 9.2 or less. When the pH of the disaggregated pulp slurry exceeds the above upper limit, the yield decreases and yellowing occurs in the pulp, which may reduce the quality of the pulp. On the other hand, when the pH of the disaggregated pulp slurry is less than the above lower limit, the foaming property is lowered, so that the ink is not discharged out of the system, the deinking agent effect is lowered, and the whiteness of the used paper pulp may be lowered. .

  As a density | concentration of the disaggregation pulp slurry in the said deinking process, 13 to 18 mass% is preferable. When the concentration of the disaggregated pulp slurry exceeds the above upper limit, the ink removing ability is lowered, and thus yield may be lowered when trying to obtain used paper pulp having high whiteness. On the other hand, when the density | concentration of a disaggregation pulp slurry is less than the said minimum, there exists a possibility that productivity may fall because the reactivity of ink and a deinking agent falls.

  The temperature of the disaggregated pulp slurry in the deinking treatment is preferably 43 ° C or higher and 47 ° C or lower. When the temperature of the disaggregated pulp slurry exceeds the above upper limit, the sticky foreign matter is softened and the removal efficiency of the sticky foreign matter is lowered, so that the quality of the used paper pulp may be lowered. On the other hand, when the temperature of the disaggregated pulp slurry is less than the above lower limit, the deinking effect is lowered due to a decrease in foamability, and the whiteness of the used paper pulp may be decreased.

  In the deinking treatment, in addition to the above deinking agent, for example, known alkaline agents such as caustic soda and sodium silicate; bleaching agents such as hydrogen peroxide, hypochlorite and hyposulfite; Foaming agents such as alkylbenzene sulfonates and sulfate esters; antifoaming agents such as silicone oil and mineral oil; pitch control agents; metal sequestering agents such as EDTA and DTPA, and the like may be blended.

  The apparatus used for the deinking process is not particularly limited, and a known apparatus can be used. However, it is particularly preferable to use a tab-type high-concentration pulper because disaggregation efficiency can be increased.

(Paper making process)
The newsprint can be obtained by paper-making the pulp slurry after the deinking process using a system generally used for papermaking. Specifically, for example, a paper making system including a wire part, a press part, a pre-dryer part, a coater part, a calendar part, and a reel part can be used. In addition to this, a paper making system comprising an off-machine coater in which the paper machine and the coater part are separated may be used, and a paper making system comprising an off-machine calendar in which the paper machine and the soft calendar are separated may be used.

  In the paper making process, a surface treatment agent can be applied to the paper surface. Examples of such a surface treatment agent include oxidized starch, hydroxyethylated starch, etherified starch, esterified starch, enzyme-modified starch, cationized starch, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, polyvinyl alcohol (PVA), styrene / Acrylic acid copolymer, styrene / (meth) acrylic acid copolymer, styrene / (meth) acrylic acid / (meth) acrylic acid ester copolymer, styrene / maleic acid copolymer, styrene / maleic acid half ester copolymer Anionic low molecular weight compounds such as polymers, styrene / maleic acid ester copolymers, water-soluble polymers such as polyacrylamide, saponified alkyd resins such as rosin, tall oil and phthalic acid, saponified products of petroleum resin and rosin Cationic polymers such as isocyanate polymers Chromatography and the like. Among these, water-soluble polymers are preferable, and oxidized starch and hydroxyethylated starch are more preferable. The said surface treating agent may be used individually by 1 type, and may use 2 or more types together. By adding these surface treatment agents, the vehicle of the ink can be absorbed quickly, the speed of the rotary press can be increased, and the filler is securely fixed to the fiber, thus preventing the filler from falling off. In addition, excellent printing opacity, printability and the like can be ensured.

The coating amount of the surface treatment agent is preferably 0.1 g / ^{m 2} or more 5 g / ^{m 2} or less in terms of solid per side content basis, 0.5 g / ^{m 2} or more 1 g / ^{m 2} or less is more preferable. If the coating amount of the surface treatment agent exceeds the above upper limit, mist of the surface treatment agent is generated and the peripheral device is soiled, and there is a possibility that a paper break or a paper defect due to the stain may occur. On the other hand, when the coating amount of the surface treatment agent is less than the above lower limit, the surface treatment of the paper becomes insufficient, and there is a possibility that the coating effect of the coating solution cannot be exhibited sufficiently.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples. In the following, unless otherwise specified,% means mass%, and the chemical addition amount means solid mass (kg) per pulp dry mass (t).

  In addition, each measured value in a present Example is a value measured with the following method.

[Sieving degree (unit:%)]
For the disaggregated pulp obtained by disaggregating newsprint paper according to JIS-P8220 (1998) “pulp-disaggregation method”, according to JIS-P8207 (2009) “pulp-sieving test method”, the sieve screen of the first tank The sieve opening of the second tank was 710 μm, the sieve opening of the second tank was 355 μm, the sieve opening of the third tank was 180 μm, and the sieve opening of the fourth tank was 106 μm.

[Machine pulp content (unit: mass%)]
The newsprint is disaggregated in accordance with JIS-P8220 (1998), and the mass ratio of the pulp showing the color of the mechanical pulp is obtained according to JIS-P8120 (1998) for the obtained disaggregated pulp. Measured according to “Fiber composition test method”.

[Basis weight (unit: g / m ² )]
It was measured according to “Paper and paperboard—basis weight measurement method” described in JIS-P8124 (1998).

[Thickness (unit: μm)]
Measured according to JIS-P8118 (1998) “Paper and paperboard—Test methods for thickness and density”.

[Tensile strength (longitudinal) (unit: kN / m)]
It was measured in the longitudinal direction of newsprint according to “Paper and paperboard—Test method for tensile properties—Part 2: Constant speed extension method” described in JIS-P8113 (2006).

[Blank Opacity (Unit:%)]
Measured according to JIS-P8149 (2000) "Paper and paperboard-Opacity test method (backing of paper)-Diffuse illumination method".

[Density (unit: g / cm ³ )]
Measured according to JIS-P8118 (1998) “Paper and paperboard—Test methods for thickness and density”.

[Ash content (unit:%)]
It was measured in accordance with “Paper, paperboard and pulp-ash content test method—525 ° C. combustion method” described in JIS-P8251 (2003).

[Printing opacity (unit:%)]
JAPAN TAPPI No. No. 45 (2000) “Newspaper—Post-printing opacity test method”, and measured using a measuring instrument ISO whiteness meter (manufactured by Suga Test Instruments Co., Ltd.).

[Whiteness (paper) (unit:%)]
Measured according to JIS-P8148 (2001) “Paper, paperboard and pulp—Measurement method of ISO whiteness (diffuse blue light reflectance)”.

[Ink fillability]
Using an offset printer (model number: Komori SYSTEMC-20, manufactured by Komori Corporation), continuous 10,000 copies can be printed with newspaper ink (trade name: Newsjet Naturalis (black), manufactured by Dainippon Ink & Chemicals, Inc.). went. About the obtained printed matter, the clearness and the shading unevenness of an image were observed visually, and it evaluated based on the following evaluation criteria.
(Evaluation criteria)
5: The image is clear and there is no unevenness in density, and the ink deposition property is excellent.
4: The image is clear, there is almost no unevenness in density, and the ink deposition property is good.
3: Some portions of the image are unclear and some shading unevenness.
2: There are portions where the image is unclear and unevenness in density, and ink deposition is not good.
1: As a whole, the image is unclear, the density unevenness is remarkable, and the ink deposition property is inferior.

[Blanket paper dust, piling]
Using an offset rotary printing press (model number: LITHOPIA BTO-4, manufactured by Mitsubishi Heavy Industries, Ltd.), prints 100,000 copies on both sides of a 50-continuous printing paper, and the paper on the printing paper and blanket non-image area. The presence or absence of powder generation and accumulation was visually observed and evaluated based on the following evaluation criteria.
(Evaluation criteria)
5: Generation | occurrence | production of paper surface scraps and paper dust is not recognized at all.
4: Scratch on the paper surface is slightly observed, but no deposition on the blanket is observed.
3: Scratch on the paper surface is slightly recognized and a little accumulation on the blanket is recognized.
2: Generation | occurrence | production of the paper surface scraping was recognized and it has accumulated on the blanket.
1: Accumulation of paper dust on the paper surface and blanket is remarkable.

[Production of recycled particles from newspaper deinking floss]
Paper sludge containing 100% by mass of newspaper floss with a calcium carbonate content of 78% by mass in the inorganic particles in the newspaper deinking floss is subjected to a dehydration step so that the moisture content is 45% by mass. After that, the papermaking sludge is crushed so as to have an average particle diameter of 3 mm, and subjected to a drying process using an internal combustion type horizontal rotary kiln furnace so that the moisture content becomes 2% by mass. Combustion treatment was performed at a temperature of 800 ° C. and an oxygen concentration of 12 vol% in a rotary kiln furnace. The decomposition rate of calcium carbonate in the combustion treatment was 90%. After combusting the combusted product after the combustion step so that the average particle size becomes 3 μm, it is slurried so that the combusted product concentration becomes 10% by mass, and the pH after reaction while stirring the carbon dioxide-containing gas (concentration 16 vol%) Was blown into the slurry until it reached 7.4, and calcium carbonate was precipitated to obtain regenerated particles derived from newspaper deinking floss. The average particle size of the regenerated particles derived from this newspaper deinking floss was 4 μm, the whiteness was 88%, the oil absorption was 115 mL / 100 g, and the wire wear was 80 mg.

Example 1
[Manufacture of newsprint]
(Deinking process)
Using waste paper raw material containing 80% of waste paper and 20% of magazine waste paper A, add warm water so that the concentration of the disaggregated pulp slurry is 13% by mass. After the addition amount was added and caustic soda and sodium silicate were added as a pH adjuster, a disaggregation treatment was performed for 15 minutes. The pH of this pulp slurry was 8.7. The used “magazine waste paper A” refers to the waste paper collected in accordance with the “Recycled Paper Recycling Promotion Center“ Statistical Classification and Major Brands of Waste Paper ”(JIS) P8220 (1998)“ Pulp ”. Among the disaggregated pulp disaggregated in accordance with “the disaggregation method”, the pulp content indicating the color of the mechanical pulp measured in accordance with JIS-P8120 (1998) “Paper, paperboard and pulp-fiber composition test method” Is 85% by mass or more, and the disaggregated pulp which has been disaggregated according to JIS-P8220 (1998) “pulp-disaggregation method” is No. 2 Pulp filtered and dried with filter paper (manufactured by Advantech Toyo Co., Ltd.) ash content rate measured according to “paper, paperboard and pulp-ash content test method—525 ° C. combustion method” described in JIS-P8251 (2003) Is a magazine waste paper that has been sorted so as to be 18% or less. Specifically, among magazine waste paper, there are few coated papers such as monthly magazines and weekly magazines, and magazine waste papers whose back cover is bound with wire or glue are selectively collected. Moreover, the used pulp paper A used had a mechanical pulp content of 90% by mass and an ash content of 10%.
(Deinking agent)
Fatty acid-based deinking agent: “DI-254” manufactured by Kao Corporation, 0.6 kg / t
Higher alcohol deinking agent: “DI-7000D” manufactured by Kao Corporation, 2.1 kg / t

  Then, the density | concentration of the disaggregation pulp slurry was diluted to 1%, and it floated using the eco-cell type | mold floatator by IHIVOITTH, and the used paper pulp was obtained.

Recycled particles derived from the newspaper deinking floss as a filler were added to a pulp slurry composed of 100% by mass of the used paper pulp at a solid content of 20 kg / t per absolutely dry pulp. Next, a 600 ppm cationic polymer (BASF Japan Co., Ltd., polymin PR8150) is added as a flocculant to the absolutely dry pulp, and a newspaper base paper having a basis weight of 41.0 g / m ² is added using a twin wire paper machine. Made paper.

Furthermore, a starch solution in which 90 parts by mass of oxidized starch (mass average molecular weight 700,000 manufactured by Nippon Food Processing Co., Ltd.) and 10 parts by mass of hydroxyethylated starch (HES, mass average molecular weight 150,000 manufactured by Penford) was mixed as a surface treatment agent. A surface treatment agent in which 15 parts by mass of styrene-based sizing agent (SS2712 manufactured by Seiko PMC Co., Ltd.) with a solid content of 100 parts by mass of starch is mixed with 1.2 g / m ² (per side) on both sides of the base paper. Each was coated with 0.6 g / m ² ) to obtain the newsprint of Example 1.

(Examples 2 to 4)
Ratio of waste newspaper and magazine waste paper composing raw pulp, ratio of first tank residue (C ₁ ), second tank residue (C ₂ ) and fourth tank passage (C ₅ ) of sieving degree, inclusion of mechanical pulp Except that the amount was changed as shown in Table 1, the same operation as in Example 1 was performed to obtain newspapers of Examples 2 to 4.

(Examples 5-7)
Except that the type and amount of filler were changed as shown in Table 1, the same operation as in Example 1 was performed to obtain newspapers of Examples 5 to 7. In Example 7, white carbon (volume average particle diameter of 18 μm) was used as a filler instead of the regenerated particles derived from newspaper deinking floss.

(Example 8)
The newsprint paper of Example 8 was obtained in the same manner as in Example 1 except that 90% by weight of the used paper pulp and 10% by weight of the thermomechanical pulp (freeness 120 ml CSF) were used as raw material pulp.

(Comparative Examples 1-2)
Ratio of waste newspaper and magazine waste paper in raw material waste paper, ratio of first tank residue (C ₁ ), second tank residue (C ₂ ) and fourth tank passage (C ₅ ) of sieving degree, mechanical pulp content, Except for changing the basis weight as shown in Table 1, the same operation as in Example 1 was performed to obtain newspapers of Comparative Examples 1 and 2. However, in Comparative Example 2, the basis weight of the newspaper base paper was 42.3 g / m ² .

(Comparative Example 3)
The newsprint paper of Comparative Example 3 was obtained in the same manner as in Example 1 except that the magazine waste paper B was used instead of the magazine waste paper A as the raw material pulp. “Magazine waste paper B” is magazine waste paper collected in accordance with “Statistical Classification and Major Brands of Waste Paper” (Recycle Promotion Center). The used magazine waste paper B had a mechanical pulp content of 75% by mass and an ash content of 20%.

(Reference Example A)
As a reference example, the ratio of the first tank residue (C ₁ ), the second tank residue (C ₂ ), the fourth tank passage (C ₅ ), and the mechanical pulp content of the newspaper paper made by other companies were measured. did.

(quality evaluation)
The basis weight, thickness, tensile strength, blank paper opacity, density, ash content, printing opacity, and whiteness of the newspapers of Examples 1-8, Comparative Examples 1-3, and Reference Example A are as described above. Measured and evaluated for ink fillability and blanket paper dust piling. The results are shown in Table 1.

  As shown in Table 1 above, the newsprint of the present invention is bulky in spite of the high blending and low basis weight of 90% by weight or more of the waste paper pulp in the total pulp, tensile strength, white paper It turns out that it is excellent in transparency, printing opacity, and printability.

  The newsprint of the present invention contains a large amount of waste paper pulp and has a low bulk weight, but it is bulky and has excellent tensile strength, blank paper opacity, printing opacity, and printability. It can be particularly preferably used.

Claims (4)

Newspaper paper having a waste paper pulp content of 90% by mass or more and a basis weight of 35 g / m ² or more and 43 g / m ² or less with respect to the total pulp,
The disaggregated pulp disaggregated according to JIS-P8220 (1998) “pulp-disaggregation method” is 710 μm according to JIS-P8207 (2009) “pulp-sieving test method”. In the degree of sieving (%), the sieve mesh opening of the second tank is 355 μm, the sieve mesh opening of the third tank is 180 μm, and the sieve mesh opening of the fourth tank is 106 μm. A newspaper having a ratio of (C ₁ ) of 20% or less and a ratio of the second tank residue (C ₂ ) of 20% or more. The newsprint according to claim 1, wherein a ratio of the fourth tank passage (C ₅ ) in the sieving degree (%) is 20% or more.   The newsprint according to claim 1 or 2, wherein the content of the pulp showing the color of mechanical pulp in the disaggregated pulp is 40 mass% or more and 70 mass% or less. The paper thickness is 65 μm or more and 70 μm or less,
The tensile strength is 2.1 kN / m or more and 3.1 kN / m or less,
The newsprint according to claim 1, 2 or 3, wherein the blank paper opacity is 92% or more and 96% or less.