Newspaper

Abstract

The objective of this invention is to develop newsprint paper with low density and suppressed fading. [Solution] The present invention provides newsprint with low density and suppressed fading. The newsprint according to the present invention contains 50% by weight or more of chemical pulp and / or recycled paper pulp with an average kink index of 1.2 (1 / mm) or higher, relative to 100% by weight of pulp.

Description

[Technical Field]

[0001] This invention relates to newsprint containing bulky pulp. In particular, this invention relates to newsprint containing bulky pulp that is highly bulky and less prone to problems such as discoloration. [Background technology]

[0002] To prevent global warming and build a sustainable society, it is crucial to reduce greenhouse gas emissions, promote CO2 absorption and sequestration, and encourage the use of biomass, a renewable resource. Effective ways to reduce greenhouse gas emissions include switching to non-fossil fuels and promoting energy conservation. In the paper industry, efforts have begun to reduce greenhouse gas emissions in the pulp and paper manufacturing processes. Furthermore, there is a growing demand for lighter paper in the paper distribution process to reduce transportation energy.

[0003] However, simply reducing the weight, i.e., lowering the basis weight of the paper, is undesirable because it reduces the paper's thickness, impairing the product's volume, aesthetics, and processing suitability. What paper users demand for weight reduction is to lower the paper's weight without reducing its thickness, or more preferably, to increase its thickness. Therefore, making paper lighter and bulkier is a crucial technological challenge in recent years.

[0004] One method for reducing the density (bulkness) of paper involves examining the pulp used for papermaking. Generally, wood pulp is used for papermaking, but to increase the bulk of paper, it is known that mechanical pulps such as wood pulp (made by grinding wood with a grinder), refiner mechanical pulp (made by refining wood with a refiner), or thermomechanical pulp are more effective than chemical pulp (made by extracting lignin, a reinforcing material in wood fibers, using chemicals) because the fibers are more rigid. However, mechanical pulps are known to use a large amount of petroleum-derived energy in the pulping process, and as a product, they have a lower whiteness compared to chemical pulps, resulting in problems such as a decrease in the overall whiteness of the paper and the paper turning yellow (fading) in color.

[0005] Furthermore, from the perspective of papermaking, methods for increasing the bulkiness (reducing the density) of uncoated paper and coated base paper are known, including the use of bulking agents. Known bulking agents include, for example, paper bulking agents containing specific alcohols and / or their polyoxyalkylene adducts (Patent Document 1), nonionic surfactants (Patent Document 2), and paper bulking agents consisting of ester compounds of polyhydric alcohols and fatty acids (Patent Document 3). Technologies applying these paper bulking agents to cardboard (Patent Document 4) have also been proposed.

[0006] Furthermore, from the perspective of reducing transportation costs as mentioned above, there is a growing demand for lighter coated paper. Technology has been disclosed for low-basis-weight lightly coated paper that, despite a low coating amount, has particularly excellent white paper appearance and rigidity, and is suitable for printing and bookbinding (Patent Document 5). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 98 / 03730 brochure [Patent Document 2] Japanese Patent Application Publication No. 11-200283 [Patent Document 3] Patent No. 2971447 [Patent Document 4] Patent No. 3041294 [Patent Document 5] Japanese Patent Publication No. 2004-124289 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Newspaper paper requires a low basis weight, yet possesses rigidity and minimal bleed-through, from the perspective of readability and printability. Furthermore, with the goal of efficient resource utilization and environmental protection, the recycling of waste paper is progressing, and efforts are being made to bring the recycled pulp content closer to 100%. However, because recycled newspaper pulp is recycled many times, the pulp fibers become brittle, and the higher the recycled pulp content, the lower the tensile strength required for high-speed web printing of newspaper paper becomes.

[0009] Meanwhile, in recent years, there has been a strong demand for companies to take measures against global warming, and as one of these measures, the lightweighting of newsprint is being promoted from the perspective of resource conservation, transportation energy, and cost reduction. The lightweighting required for paper means reducing the paper weight without reducing the paper thickness, or more preferably increasing the paper thickness, and making paper lightweight and bulky is an important technological challenge. In particular, newsprint uses a lot of recycled paper pulp with many fine fibers, and also uses a lot of filler to prevent bleed-through, so the interfiber bonding tends to decrease, and the decrease in rigidity that comes with lightweighting newsprint has been a major challenge.

[0010] For example, Japanese Patent Publication No. 2015-209603 proposes newsprint with a reduced amount of mechanical pulp to suppress discoloration caused by mechanical pulp, but this may result in insufficient bulk and strength.

[0011] In light of these circumstances, the object of the present invention is to develop a bulky pulp that has a high bulkiness effect and suppresses discoloration, and to provide excellent newsprint using it. [Means for solving the problem]

[0012] In other words, the present invention provides the following, but is not limited to the above. [1] Newspaper containing 50% by weight of chemical pulp and / or recycled paper pulp with an average kink index of 1.2 (1 / mm) or higher, relative to 100% by weight of pulp. [2] Newspaper as described in [1], having a synthetic kink index of 1.1 to 3.5 (l / mL). [3] The newsprint according to [1] or [2], wherein the content of mechanical pulp is less than 5% by weight based on 100% by weight of the pulp. [4] When the pulp obtained by disintegrating the newsprint is analyzed based on ISO 16065-2:2007, among the fibers having a fiber length of 0.2 to 7.5 mm, the proportion of fibers having a length-weighted average fiber length within the range of 1 to 1.5 mm is 5 to 30%. The newsprint according to [1] or [2]. [5] The chemical pulp is as follows: (a) having an average fibril area of 1.5% or less, (b) having an average fibril perimeter ratio of 5.0% or less, The newsprint according to [1] or [2], having one or more of the following characteristics. [6] The newsprint according to [1] or [2], wherein the CSF of the chemical pulp is 400 mL or more. [7] The newsprint according to [1] or [2], wherein the chemical pulp contains kraft pulp having a CSF of 500 mL or more and an average kink index of 1.3 (1 / mm) or more. [8] The newsprint according to [1] or [2], wherein the chemical pulp is contained at 70% by weight or more based on 100% by weight of the pulp. [9] The newsprint according to [1] or [2], containing a bulking agent.

Advantages of the Invention

[0013] According to the present invention, there is provided a bulky pulp having a high bulking effect and suppressing fading, whereby a newsprint having a high bulk and less fading can be obtained. In particular, according to the present invention, even when no mechanical pulp such as mechanical pulp (MP) or thermomechanical pulp (TMP) is used or when the blending ratio of mechanical pulp is low, a newsprint having sufficient bulkiness and suppressed fading can be obtained.

Embodiments for Carrying Out the Invention

[0014] The newsprint of the present invention is made from chemical pulp and recycled paper pulp and contains pulp having a specific average kink index. In the present invention, the newsprint is made bulkier by using 50% by weight or more of chemical pulp and / or recycled paper pulp (hereinafter also referred to as bulky pulp) with an average kink index of 1.2 (1 / mm) or higher.

[0015] Bulky pulp The bulky pulp of the present invention is a chemical pulp and / or recycled paper pulp having a specific average kink index, and in one embodiment, is a chemical pulp having a predetermined average kink index, average kink angle, fibril area, and fibril perimeter.

[0016] Examples of raw material pulps include wood pulp, non-wood pulp, and deinked pulp (recycled paper pulp). Wood pulp is not particularly limited, but examples include bleached hardwood kraft pulp (LBKP), unbleached hardwood kraft pulp (LUKP), bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and oxygen-bleached kraft pulp (OKP). Non-wood pulp is not particularly limited, but examples include cotton-based pulps such as cotton linters and cotton lint, and non-wood-based pulps such as hemp, straw, bamboo, and bagasse. The raw material pulp may be used individually or in mixtures of two or more types. Furthermore, organic synthetic fibers such as polyamide fibers and polyester fibers, recycled fibers such as polynosic fibers, and inorganic fibers such as glass fibers, ceramic fibers, and carbon fibers may be mixed with the raw material pulp. From the viewpoint of ease of availability, wood pulp is preferred as the raw material pulp. Furthermore, among wood pulps, from the viewpoint of suppressing discoloration, chemical pulp is preferred, more preferably kraft pulp, even more preferably one or more selected from hardwood kraft pulp such as eucalyptus and acacia, and softwood kraft pulp such as pine and cedar, and even more preferably one or more selected from bleached hardwood kraft pulp (LBKP) and bleached softwood kraft pulp (NBKP).

[0017] <Average kink angle, average kink index, composite kink index> The kink index of pulp fibers is an index that indicates the degree of bending of the pulp fibers. For example, it can be calculated by measuring the ratio of the length of individual fibers to the straight-line distance connecting the start and end points of those fibers using an image analysis device. In one embodiment, the average kink index can be calculated by weighting the number of kinks for each certain angular range according to the increase in angle, and dividing by the sum of the fiber lengths. For example, this can be measured using a fiber tester manufactured by Lorentzen & Wettre.

[0018] In this invention, it is believed that by blending pulp with a high degree of kink, specifically chemical pulp and / or recycled paper pulp (bulky pulp) with an average kink index of 1.2 (1 / mm) or higher, into newsprint, the gaps between fibers become larger, thereby improving the bulkiness of the paper. If the average kink index is too low, the pulp fibers will not bend enough, and sufficient bulkiness will not be obtained when the paper is made. On the other hand, if the average kink index exceeds 10 (1 / mm), the pulp fibers will be bent too much, meaning that the fibers will be damaged too much, or the interfiber bonds will become significantly weaker, which may cause a decrease in paper strength. Therefore, in this invention, it is preferable to set the average kink index of the pulp to 10 (1 / mm) or less, more preferably to 8 or less or 6 or less, and it may also be 4 (1 / mm) or less or 2.5 (1 / mm) or less. This makes it possible to maintain the desired bulkiness even when the proportion of mechanical pulp is reduced. Furthermore, increased bulkiness contributes to the opacity of the paper and is effective in suppressing bleed-through. In addition, bulky pulp has the effect of suppressing paper discoloration due to the stability of its fiber structure.

[0019] The average kink index mentioned above can be adjusted by the pulp concentration during pulp beating, the type of tree used for the pulp, etc. Specifically, the higher the pulp concentration during beating, the higher the average kink index becomes, and the more bent fibers will be present in the pulp fibers that make up the paper base material.

[0020] The synthetic kink index is an index that shows the kink index of the entire paper. It can be determined by multiplying the average kink index of each pulp by the amount of that pulp used and summing the results for all pulps. The synthetic kink index can also be determined by measuring the average kink index in the same way as the average kink index when the raw pulps are mixed, or by measuring the average kink index of the disintegrated pulp obtained by disintegrating the paper. The synthetic kink index is preferably between 1.1 (1 / mm) and 4.0 (1 / mm), and more preferably between 1.3 (1 / mm) and 3.5 (1 / mm). By keeping it within this range, it is possible to produce newsprint that balances bulkiness and strength such as specific tensile strength.

[0021] The average kink angle is the average value indicating the degree of bending of a straight fiber, and is defined, for example, as the average of the angles in Olson, J et al., “An Analyzer for Fiber Shape and Length” (Journal of Pulp and Paper Science, Vol. 21, No. 11, 1995, pp. J367-J373). The average kink angle of the present invention can be measured using, for example, a fiber tester manufactured by Lorentzen & Wettre after the pulp has been sufficiently disintegrated in water. The average kink angle of bulky pulp is preferably 48° or higher, more preferably 49° or higher, and even more preferably 50° or higher. By setting it within the above range, bulky paper can be obtained.

[0022] In this invention, the average fiber length, average fiber width, and average fibril circumference ratio are all length-weighted average values. These can be measured using commercially available fiber length measuring devices by an automated optical analysis method in accordance with JIS P8120. Specifically, the fibers dispersed in water are photographed and automatically analyzed. The length-weighted average fiber length is obtained by dividing the sum of the squares of the measured n fiber lengths by the sum of the n fiber lengths. The length-weighted average fiber width is obtained by dividing the sum of the areas of the measured n fibers, i.e., the sum of the values ​​(A) obtained by multiplying the n fiber widths (W) and fiber lengths (L), by the sum of the n fiber lengths. The fibril circumference ratio (FPR) is the value obtained by dividing the fibril circumference (FP) by the sum of the stem fiber circumference (P) and the fibril circumference (FP) (FP / (FP+P)). The stem fiber refers to the original fiber that is not a fibril. The perimeter (P) is twice the sum of the fiber length (L) and width (W) of the stem fiber (2(L+W)). The fibril perimeter (FP) is twice the sum of the fiber length (FL) and width (FW) of the fibril (2(FL+FW)). The length-weighted average fiber length, length-weighted average fiber width, and length-weighted average fibril perimeter ratio are calculated automatically.

[0023] The length-weighted average fiber length of the bulky pulp of the present invention is preferably 0.5 mm or more, more preferably 0.7 mm or more, and even more preferably 1.0 mm or more. The average fiber width is preferably 15 μm or more, and more preferably 30 μm or less. By using pulp fibers within the above range, it is possible to produce pulp with high strength and rigidity for each individual fiber, and high bulkiness. There is no particular upper limit to the average fiber length, but for example, it may be 5 mm or less, 4 mm or less, 3 mm or less, or 2 mm or less. In one embodiment, it is preferable that the content of fibers with a fiber length of 1.0 mm or more and 1.5 mm or less, when measured in the range of fiber length from 0.2 to 7.65 mm, among the fibers contained in the newspaper paper is 5% to 30%.

[0024] <Foil ratio> The proportion of fine fibers (fine content) can be measured after the pulp has been sufficiently disintegrated in water, for example, using a fiber tester manufactured by Lorentzen & Wettre. In this specification, pulp fibers with a fiber length of 0.2 mm or less are sometimes referred to as "fine content." In this invention, the total fine content is preferably 10 to 30%. By keeping it within this range, it is possible to produce newsprint with an excellent balance between strength and bulkiness.

[0025] The water drainage (also known as Canadian Standard Freeness, CSF) of bulky pulp is preferably 400 ml or more, or 450 ml or more, and may be 500 ml or more, or 600 ml or more, from the viewpoint of suppressing fibrillation of the pulp and maintaining the rigidity of the pulp. The upper limit is preferably 750 ml or less, and more preferably 700 ml or less. If the CSF is too low, the shortening of fibers and fibrillation may progress too much, and it may not be possible to obtain a sufficient bulking effect. On the other hand, if the CSF is too high, the water drains too well, and a good form may not be formed during papermaking, which may result in newsprint with inferior strength and backing. It should be noted that the fiber characteristics of the raw pulp used in papermaking do not differ significantly from the fiber characteristics of disintegrated pulp obtained by disintegrating newsprint. For example, by adjusting the length-weighted average fiber length of the raw pulp, the length-weighted average fiber length of the pulp constituting the paper base can be appropriately adjusted, and the same applies to other fiber characteristics.

[0026] Furthermore, when analyzing pulp properties such as average kink index, average kink angle, composite kink index, fiber length, and water filtration rate from paper, pulp samples can be prepared using the following method. (Method for preparing pulp sample from paper) Cut out a 40 cm × 40 cm piece of paper, immerse it in ion-exchanged water, adjust the solid content concentration to 2% by mass, and then immerse it for 24 hours. After immersing for 24 hours, according to JIS P8220-1, use a standard disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) to disintegrate the pulp into fibrous form. Even if there is a printed layer, disintegration may be carried out with the configuration including the printed layer. The obtained pulp fiber sample can be used for analysis of various pulp properties.

[0027] From the viewpoint of suppressing fading, the newsprint of the present invention may use kraft pulp (BKP) obtained by bleaching pulp through one or more known bleaching processes. In this case, oxidizing agents such as hydrogen peroxide, ozone, peracetic acid, or reducing agents such as hydrosulfite (sodium dithionite), sodium bisulfate, sodium borohydride, formamidine sulfinic acid (FAS), etc. can be used.

[0028] Newspaper The basis weight of the newsprint of the present invention is not particularly limited, but in one embodiment, it can be 30 g / m 2 or more and 80 g / m 2 or less. In one embodiment, the basis weight of the paper according to the present invention can be 32 - 64 g / m 2 or 34 - 60 g / m 2 and can be 38 - 56 g / m 2 or 40 - 52 g / m 2 as well. If the basis weight is too low, it is difficult to ensure sufficient printing suitability and strength as newsprint, and if the basis weight is too high, it is hard to say that it is lightweight. The newsprint of the present invention can ensure sufficient bulkiness and achieve excellent printing suitability within this basis weight range by containing the above-mentioned bulky pulp (high kink pulp). Also, the density of the newsprint according to the present invention can be, for example, 0.50 - 1.05 g / cm 3 and can be 0.60 - 1.03 g / cm 3 or 0.70 - 1.01 g / cm 3 as well.

[0029] In one embodiment, the newsprint paper according to the present invention preferably has a whiteness of 45% or more. In particular, for highly white newsprint paper, a whiteness of 60% or more is desirable. Furthermore, the opacity of the paper is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more or 92% or more. In the present invention, the opacity of the paper can be measured according to JIS P8149:2000.

[0030] In the present invention, the bulky pulp content is preferably 60% or more by weight, or 70% or more by weight, more preferably 80% or more by weight, and even more preferably 90% or more by weight, relative to 100% by weight of pulp. By increasing the bulky pulp content in the present invention, it is possible to manufacture newsprint with even greater bulk.

[0031] The newsprint paper of the present invention may use only bulky pulp as pulp, or may use two or more different types of bulky pulp, or may use bulky pulp in combination with pulp other than bulky pulp, but from the viewpoint of environmental impact such as greenhouse gas reduction and fading, crushed wood pulp (GP), thermo Mechanical pulp such as mechanical pulp (TMP) and chemothermomechanical pulp (CTMP) It is preferable not to use it, and if it is used, it is preferable to limit its content to 5% by weight or less. Examples of pulps other than bulky pulp that can be used include wood pulp, non-wood pulp, and deinked pulp (DIP). Wood pulp is not particularly limited, but examples include bleached hardwood kraft pulp (LBKP), unbleached hardwood kraft pulp (LUKP), bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), oxygen bleached kraft pulp (OKP), and other chemical pulps, as well as semi-chemical pulp (SCP) and chemiground wood pulp (CGP). From the viewpoint of suppressing discoloration of newsprint, it is preferable to use kraft pulp that has been bleached by one or more known bleaching processes, similar to the bulky pulp mentioned above, rather than unbleached pulp that contains a large amount of lignin or hemicellulose. Furthermore, the raw pulp may be mixed with organic synthetic fibers such as polyamide fibers and polyester fibers, regenerated fibers such as polynosic fibers, and inorganic fibers such as glass fibers, ceramic fibers, and carbon fibers.

[0032] The newsprint of the present invention is obtained by papermaking a pulp slurry to which internal additives are added as needed. In addition to the pulp described above, known internal additives for papermaking, such as fillers, sizing agents, dry strength enhancers, wet strength enhancers (e.g., polyamide polyamine epichlorohydrin), yield enhancers (e.g., aluminum sulfate), water drainage enhancers, pH adjusters, softeners, antistatic agents, defoamers, dyes, and pigments, may be added to the newsprint as needed. Examples of fillers include kaolin, talc, titanium dioxide, heavy calcium carbonate, light calcium carbonate, calcium sulfite, gypsum, calcined kaolin, white carbon, amorphous silica, delaminated kaolin, diatomaceous earth, magnesium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide. Examples of sizing agents include rosin-based, alkyl ketene dimer-based, alkenyl succinic anhydride-based, styrene-acrylic-based, higher fatty acid-based, and petroleum resin-based sizing agents.

[0033] In the newsprint paper according to the present invention, it is preferable to add a filler, more preferable to add calcium carbonate which has a high opacity-improving effect, and even more preferable to add light calcium carbonate which can obtain an even higher opacity-improving effect. In the present invention, the amount of filler added is not particularly limited, but for example, it can be added so that the ash content in the paper is 5% by weight or more and 30% by weight of solids. In particular, in the case of highly white newsprint paper, it is desirable to add filler so that the ash content in the paper is 15% by weight or more of solids.

[0034] The fillers used in the newsprint according to the present invention are not particularly limited and can be those known in the papermaking field. For example, one or more of the following can be used: light calcium carbonate, heavy calcium carbonate, light calcium carbonate-silica composites, white carbon, clay, amorphous silica, talc, titanium dioxide, etc. Among these, light calcium carbonate and light calcium carbonate-silica composites are preferred. For light calcium carbonate, rosette-shaped, spindle-shaped, or columnar shapes are preferred. The average particle diameter is 0.1 to 20 μm, and the specific surface area is 3 to 20 m². 2 / g is preferable.

[0035] Furthermore, a light calcium carbonate-silica composite can be used as a filler. Light calcium carbonate-silica composites are described in Japanese Patent Publication No. 2003-212539, Japanese Patent Publication No. 2005-272155, and others. The crystalline form of the light calcium carbonate forming the core of the light calcium carbonate-silica composite can be calcite or aragonite, and its shape can be needle-shaped, columnar, spindle-shaped, spherical, cubic, amorphous, or rosette-shaped. In particular, when rosette-shaped calcite-based light calcium carbonate is used, a light calcium carbonate-silica composite with excellent bulkiness, opacity improvement, and rigidity improvement effects can be obtained, and is suitably used in the present invention. The rosette shape refers to a shape in which primary particles of spindle-shaped light calcium carbonate aggregate radially to form secondary particles, and it exhibits a higher specific surface area and oil absorption than other types of light calcium carbonate. Therefore, during printing, ink is absorbed into this composite, improving ink bleed-through. The average particle size of the absorbent light calcium carbonate-silica composite is preferably 20 μm or less, and more preferably 1 to 10 μm. This range allows for an appropriate balance between surface strength and oil absorption. Furthermore, in this invention, the whiteness of the light calcium carbonate and the light calcium carbonate-silica composite is preferably 95% or higher.

[0036] The newsprint of the present invention is preferably manufactured using a neutral papermaking method. Compared to acidic paper produced by an acidic papermaking method, neutral paper has superior preservation properties and allows for a higher proportion of deinked pulp. Collected waste paper is usually processed under alkaline chemicals to produce deinked pulp. Under acidic papermaking conditions, calcium ions from calcium carbonate contained in the deinked pulp may react with aluminum sulfate to precipitate as gypsum (calcium sulfate). Furthermore, neutral papermaking allows for the effective utilization of calcium carbonate derived from waste paper pulp, thus conserving resources.

[0037] Furthermore, since the newsprint paper of the present invention has weaker interfiber bonding and may have lower paper strength compared to high-density paper, it is preferable to add a drying agent that can strengthen the interfiber bonding. The drying agent is more preferably polyacrylamide (PAM) and / or starch.

[0038] In the papermaking of newsprint, known wet papermaking machines, such as long-wire papermaking machines, gap former type papermaking machines, cylinder papermaking machines, and short-wire papermaking machines, can be appropriately selected and used. In the present invention, the papermaking machine is not particularly limited, and any known in the papermaking field can be freely used. For example, gap formers, hybrid formers, and on-top formers having a double-sided dewatering mechanism are desirable. Next, the paper layer formed by the papermaking machine is conveyed by felt and dried with a dryer. A multi-stage cylinder dryer may be used as a pre-dryer before drying with the dryer.

[0039] Furthermore, in the newsprint paper of the present invention, bulking agents (densitizing agents) such as surfactants, which are organic compounds that inhibit the interfiber bonding of pulp fibers, can be used. Organic compounds that inhibit the interfiber bonding of pulp fibers are compounds that have hydrophobic and hydrophilic groups, and examples include compounds shown in WO98 / 03730, JP-A-11-200284, JP-A-11-350380, JP-A-2003-96694, JP-A-2003-96695, etc.

[0040] Specifically, ethylene and / or propylene oxide adducts of higher alcohols, polyhydric alcohol-type nonionic surfactants, ethylene oxide adducts of higher fatty acids, ester compounds of polyhydric alcohols and fatty acids, ethylene oxide adducts of ester compounds of polyhydric alcohols and fatty acids, or fatty acid polyamidoamines, fatty acid diamidoamines, fatty acid monoamides, or polyalkylene polyamine-fatty acid-epichlorohydrin condensates, stearate amides, etc., can be used individually or in combination of two or more. Commercially available bulking agents include BASF's Suruzol VL, Bayer's Bivolume P Liquid, Kao's KB-08T, 08W, KB110, 115, KB130, Sansho's Reacto Pake, and Chukyo Oil's N327, which can be used individually or in combination of two or more. In the present invention, the preferred amount of bulking agent added in the papermaking process is 0.1 to 2% of the pulp, more preferably 0.2 to 1.5%. By using pulp having a specific average kink index according to the present invention in combination with a bulking agent, a more bulky paper can be obtained.

[0041] <Clear coating> In the present invention, if necessary, an adhesive such as starch may be used to apply a clear coating by sizing press or the like. The adhesive used for the clear coating is not particularly limited, but for example, starches such as oxidized starch, hydroxyethyl etherified starch, and oxygen-modified starch, polyacrylamide (PAM), polyvinyl alcohol (PVA), etc., can be used individually or in combination. Furthermore, if necessary, auxiliary agents such as surface sizing agents, water-resistant agents, water-retaining agents, thickeners, lubricants, dispersants, plasticizers, pH adjusters, defoamers, preservatives, coloring dyes, and UV-blocking agents may be added to perform the clear coating.

[0042] The clear coating of the present invention can be performed off-machine or on-machine on the base paper manufactured as described above, as needed. Unlike pigment coating, which involves applying a coating solution containing a white pigment, clear coating refers to applying a coating solution that does not contain a pigment. Clear coating allows for covering the surface of the base paper with a smaller amount of coating compared to pigment coating, and sufficient coverage can be obtained even with a small ratio of the coating layer to the basis weight. Therefore, it is possible to produce newsprint with excellent printability while minimizing the impact on the density and thickness of the resulting newsprint. Combined with the low density achieved by bulky pulp, clear coating can further enhance surface smoothness and improve printability.

[0043] The coating apparatus for clear coating is not particularly limited, but examples include blade coaters, gate roll coaters, size press coaters, and rod metering size presses, with gate roll coaters and rod metering size presses being preferred. The solid content concentration of the clear coating liquid can be adjusted as appropriate depending on the composition and coating method, but for example, it can be about 5 to 15% by weight. The amount of clear coating applied is not particularly limited, but for example, water-soluble polymer substances such as adhesives should be 0.05 to 2 g / m² in solid content. 2 The surface sizing agent has a solid content of 0.01-0.2 g / m². 2 It can be described as "to a certain extent."

[0044] For use as an adhesive in clear coating, for example, a water-soluble polymer substance that enhances surface strength can be suitably used. Examples of such water-soluble polymer substances include starches such as starch, enzyme-modified starch, thermochemically modified starch, oxidized starch, esterified starch, etherified starch (e.g., hydroxyethylated starch), and cationized starch; polyvinyl alcohols such as polyvinyl alcohol, fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, cationic-modified polyvinyl alcohol, and terminally alkyl-modified polyvinyl alcohol; polyacrylamides such as polyacrylamide, cationic polyacrylamide, anionic polyacrylamide, and amphoteric polyacrylamide; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and methylcellulose; styrene-butadiene copolymers; polyvinyl acetate; vinyl chloride-vinyl acetate copolymers; polyvinyl chloride; polyvinylidene chloride; and polyacrylic acid esters. These can be used individually or in mixtures of two or more types.

[0045] The surface sizing agent used in clear coating is not particularly limited, but examples include, but are not limited to, styrene-maleic acid copolymer resins, styrene-acrylic acid copolymer resins, α-olefin-maleic acid copolymer resins, acrylic acid ester-acrylic acid copolymer resins, cationic sizing agents, and alkyl ketene dimer sizing agents. Furthermore, in the case of neutral papermaking, cationic surface sizing agents are preferably used. Such cationic surface sizing agents are not particularly limited, but examples include those described in Japanese Patent Publication No. WO2005 / 003457, Japanese Patent Publication No. 2005-105488, Japanese Patent Publication No. 2005-248338, Japanese Patent Publication No. 2006-16712, Japanese Patent Publication No. 2006-16713, Japanese Patent Publication No. 2006-97179, Japanese Patent Publication No. 2006-152510, Japanese Patent Publication No. 2006-161259, Japanese Patent Publication No. 2006-322093, etc. Also, examples include those described in Japanese Patent Application Nos. 2005-223106, 2005-312381, and 2006-17607, which are pending applications from the applicant of this application. In particular, cationic styrene-based surface sizing agents described in publications such as WO2005 / 003457, JP 2005-016712, JP 2005-016713, and JP 2006-097179 are preferred.

[0046] <Pigment coating> In the present invention, a coating layer (pigment coating layer) containing a pigment and an adhesive may be provided on the newspaper paper. As the adhesive used for coating, adhesives conventionally used for coated paper can be used. As the latex, one or more can be appropriately selected and used from the following: various copolymer latexes such as styrene-butadiene, styrene-acrylic, ethylene-vinyl acetate, butadiene-methyl methacrylate, vinyl acetate-butyl acrylate, etc.; synthetic adhesives such as polyvinyl alcohol, maleic anhydride copolymer, acrylic acid-methyl methacrylate copolymer; proteins such as casein, soy protein, synthetic protein; starches such as oxidized starch, cationized starch, urea phosphate esterified starch, hydroxyethyl etherified starch, etc.; and cellulose derivatives such as carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, etc.

[0047] The pigments used in the pigment coating layer can be those conventionally used for coated paper. For example, inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as organic pigments such as solid, hollow, or core-shell types, can be used individually or in combination of two or more types as needed.

[0048] When a coating layer containing pigments and adhesives is provided, the coating solution may contain various commonly used auxiliary agents such as dispersants, thickeners, water-retaining agents, defoaming agents, water-resistant agents, dyes, pigments and other colorants, and fluorescent dyes.

[0049] <Calendar Processing> The newsprint paper according to the present invention may be subjected to surface treatment by calendering to the extent that it does not impair the bulkiness effect of the bulky pulp, thereby improving the uniformity of its thickness and profile and enhancing its printability. In one embodiment, the newsprint paper according to the present invention is bulky yet has little show-through during printing and good ink adhesion.

[0050] The calendering method is not particularly limited, and any known calendering device can be appropriately selected and used. Preferred calendering methods include high-temperature soft nip calendering and shoe calendering, but are not limited to these. The newsprint paper of the present invention, containing bulky pulp, makes it possible to obtain desired smoothness and ink adhesion while suppressing the reduction in bulkiness due to calendering. In particular, using a high-temperature soft nip calendering is preferable because it can suppress uneven ink adhesion in solid print areas caused by differences in paper density. The processing temperature is, for example, 80 to 200°C, and the linear pressure is approximately 25 to 500 kN / m. [Examples]

[0051] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, parts and percentages in this specification are based on weight, and numerical ranges are given including their endpoints.

[0052] Evaluation method Pulp and paper were tested based on the evaluation methods described below. (1) Basis weight: Measured according to JIS P 8124. (2) Density and paper thickness: Measured according to JIS P 8118. (3) Tear strength, specific tensile strength, ISO bending strength The tear strength was measured according to JIS P8116. Furthermore, the specific tensile strength was calculated from the tensile strength (N / m) measured according to JIS P8113. Specific tensile strength = Tensile strength (N / m) / Basis weight (g / m²) 2 ) It was calculated using the following formula. Furthermore, the ISO bending stiffness (rigidity) was measured according to JIS P8115. (4) Ash content: Measured according to JIS P 8251. (5) Fadeability The sample (bulky paper) was left undisturbed for one month in a windowsill exposed to direct sunlight, and the color change was observed visually and evaluated according to the following criteria (Experiment 1). ○: The color remained almost unchanged and did not fade. ×: The color had changed to a yellowish hue and faded.

[0053] Furthermore, the fading properties (ΔE) were evaluated according to JAPAN TAPPI No. 21 "Paper and Cardboard - Fading Test Method". A weather resistance tester (Atlas Weatherometer Ci35W, Toyo Seiki Seisakusho) was used, with an irradiance of 60 W / m². 2 Samples were faded under the conditions of (300-400nm), BPT (black panel temperature) 63°C, and irradiation time of 7 hours (equivalent to 43 hours of sunlight). The hue (L*a*b*) of the paper was measured before and after fading, and ΔE was calculated according to the following formula. The fading resistance was evaluated according to the following criteria. Hue was measured using an ISO whiteness-compatible spectrophotometer (CMS-35SPXM, Murakami Color Technology Laboratory) in accordance with JIS P8148 "Test method for whiteness of paper and cardboard using diffuse illumination".

[0054] ΔE*=((ΔL*)^2+(Δa*)^2+(Δb*)^2)^(1 / 2) (6) Fiber analysis The freeness of pulp fibers was measured according to JIS P8121-2. Average fiber length, average fiber width, average fibril area, average fibril perimeter ratio, average kink angle, average kink index, and fiber percentage were measured using a fiber tester (L&W Fiber Tester Plus, ABB). The length-weighted average fiber length and average fiber width of the pulp were measured in accordance with ISO 16065-2:2007, and pulp slurry disintegrated according to JIS P8220-1 was used as a sample (solid content concentration: 2% by mass).

[0055] When analyzing the pulp fibers that make up paper from a paper sample, a pulp slurry can be prepared as follows: The cut paper sample is immersed in deionized water to adjust the solid content concentration to 2% by mass, and then immersed for 24 hours. After 24 hours of immersion, a disintegration treatment is performed for 30 minutes using a standard disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) to disintegrate the pulp into fibers. If the sample has a printed layer, disintegration may be performed with the printed layer included, but it is preferable to perform the analysis using a pulp fiber sample obtained without collecting the printed layer.

[0056] The "length-weighted average fiber length (ISO)" is the length-weighted average fiber length calculated by selecting fibers between 0.2 mm and 7.5 mm in length. In this invention, a kink is a fiber that has local deformation exceeding 30° and the distance between the two deformed parts is 200 μm or more. The average kink index (1 / mm) is the kink index of kibblewhite calculated by the following formula (1). The average kink index is calculated by weighting the number of kinks for each certain angle range according to the increase in angle, and dividing by the sum of the fiber lengths. Equation (1) Average Kink Exponent = (2 × n1 + 3 × n2 + 4 × n3) / Lc The symbols in equation (1) represent the following: n1 = Number of kinks (bends) between 21° and 45° in the measurement sample n2 = Number of kinks (bends) between 46° and 90° in the measurement sample n3 = Number of kinks (bends) between 91° and 180° in the measured sample Lc = Sum of fiber lengths of the measurement sample (mm) Furthermore, the synthetic kink index is calculated by multiplying the average kink index of each pulp in the entire pulp mixture by the weight percentage (amount in the blend) of that pulp, and then summing these values ​​for all the pulps.

[0057]

number

[0058] A. Experiment 1 (Paper Manufacturing and Evaluation) (1) Sample A1 To LBKP prepared in 600 ml of CSF, 1.0% aluminum sulfate, 0.35% polyacrylamide, 0.65% cationized starch, 0.3% bulking agent (fatty acid ester / fatty acid salt), 100 ppm yield agent, and light calcium carbonate were added to achieve a paper ash content of approximately 1%, resulting in a basis weight of approximately 60 g / m². 2 The bulky paper was manufactured to achieve the following characteristics. The paper quality and other specifications are as shown in the table below. (2) Sample A2 Bulky paper was manufactured in the same manner as Sample A1, except that NBKP (imported material) prepared in CSF675ml was used. (3) Sample A3 Apart from using NBKP (domestic material) prepared in CSF680ml, bulky paper was manufactured in the same manner as Sample A1. (4) Sample A4 A bulky paper was manufactured in the same manner as Sample A1, except that NBKP was used after fluff pulping to obtain a CSF of 715 ml. (5) Sample A5 Aside from using LBKP that had undergone fluff pulping to produce 765 ml of CSF, bulky paper was manufactured in the same manner as Sample A1. (6) Sample A6 Except for changing the amount of light calcium carbonate added as a filler to achieve an ash content of 4.5%, bulky paper was manufactured in the same manner as Sample A1. (7) Sample A7 Aside from changing the amount of light calcium carbonate added as a filler to achieve an ash content of 11.6%, bulky paper was manufactured in the same manner as Sample A1. (8) Sample A8 Bulky paper was manufactured in the same manner as Sample A1, except that the amount of bulking agent added was changed to 1%. (9) Sample A9 Bulky paper was manufactured in the same manner as sample A8, except that a bulking agent was not added. (10) Sample A10 (Comparative Example) Bulky paper was manufactured in the same manner as Sample A1, except that bleached TMP (thermomechanical pulp) prepared in 158 ml of CSF was used. (11) Sample A11 (Comparative Example) Bulky paper was manufactured in the same manner as with sample A1, except that LBKP prepared by further beating the LBKP from sample A1 to obtain a CSF of 390 ml was used. (12) Sample A12 (Comparative Example) Bulky paper was manufactured in the same manner as sample A11, except that a 1% bulking agent was added.

[0059] [Table 1-1]

[0060] From the results above, it was found that the bulky paper of the present invention, which uses pulp with a high average kink index and high water drainage, is a bulky paper with excellent fade resistance and bulkiness. In other words, when pulp with an average kink index of 1.3 or higher was used (Samples A1 to A9), bulkiness was achieved even though no mechanical pulp was contained. Furthermore, the bulky paper containing the bulky pulp of the present invention had particularly excellent fade resistance because it does not contain mechanical pulp. (13) Sample A13 (Comparative Example) Bulky paper was manufactured in the same manner as Sample A10, except that aluminum sulfate, PAM (polyacrylamide), cationized starch, bulking agent, yield agent, and light calcium carbonate were not added. (14) Sample A14 (Comparative Example) Bulky paper was manufactured in the same manner as Sample A11, except that aluminum sulfate, PAM, cationized starch, bulking agent, yielding agent, and light calcium carbonate were not added. (15) Sample A15 Bulky paper was manufactured in the same manner as Sample A1, except that aluminum sulfate, PAM, cationized starch, bulking agent, yielding agent, and light calcium carbonate were not added. (16) Sample A16 Bulky paper was manufactured in the same manner as sample A4, except that aluminum sulfate, PAM, cationized starch, bulking agents, yielding agents, and light calcium carbonate were not added.

[0061] [Table 1-2]

[0062] As is clear from the results above, by using pulp with a high average kink index, it was possible to reduce the density and obtain bulky paper without using bulking agents or mechanical pulp. B. Experiment 2 (Paper Manufacturing and Evaluation) B-1. Pulp Preparation Eight types of pulp with different average kink indices were prepared for use in making newsprint. Details of the prepared pulps are shown in the table below. The average kink indices of kraft pulp (KP), for example, were adjusted as needed to achieve the desired values ​​through tree species and beating treatment. The synthetic kink indices were calculated from the average kink indices and blending ratios of the pulps used.

[0063] [Table 2-1]

[0064] B-2. Manufacturing of newsprint The pulp was mixed according to the formulations shown in the table below, and 1.0% aluminum sulfate (relative to pulp), 0.35% polyacrylamide (relative to pulp), 0.65% cationized starch (relative to pulp), and 100 ppm yield agent were added. Furthermore, light calcium carbonate was added to bring the paper ash content to approximately 1%. In addition, for samples other than B7-B8, 0.3% of a bulking agent (fatty acid ester / fatty acid salt type) was added relative to the pulp.

[0065] Next, newsprint was manufactured from the pulp prepared as described above using a twin-wire machine (hybrid former) with a neutral papermaking process (papermaking speed: approximately 1000 m / min, set basis weight: approximately 45 g / m²). 2 The paper surface is coated with a clear coating of oxidized starch and a sizing agent (coating amount on both sides: approximately 0.8g / m²). 2 Furthermore, calendar processing was performed using a soft nip calendar.

[0066] [Table 2-2]

[0067] Samples B3 to B8, which are embodiments of the present invention, showed superior fade resistance compared to sample B1. In particular, the newsprint paper of samples B4 to B8 had a ΔE* value of less than 3.0, indicating that fade resistance was significantly suppressed.

[0068] On the other hand, while the newsprint paper of the comparative example, Sample B1, achieved low density through TMP, it was extremely prone to discoloration. Furthermore, when using general chemical pulp with a low average kink index (Sample B2), although the discoloration resistance was excellent, it was not possible to sufficiently reduce the density of the newsprint paper.

Claims

1. Newspaper containing 50% by weight of chemical pulp and / or recycled paper pulp with an average kink index of 1.2 (1 / mm) or higher, relative to 100% by weight of pulp.

2. The newsprint according to claim 1, wherein the synthetic kink index is 1.1 to 3.5 (l / mL).

3. The newsprint according to claim 1 or 2, wherein the mechanical pulp content is less than 5% by weight relative to 100% by weight of pulp.

4. The newspaper paper according to claim 1 or 2, wherein, when the pulp obtained by disintegrating the newspaper paper is analyzed in accordance with ISO 16065-2:2007, the proportion of fibers with a length-weighted average fiber length in the range of 1 to 1.5 mm among fibers with a fiber length of 0.2 to 7.5 mm is 5 to 30%.

5. The aforementioned chemical pulp is as follows: (a) The average fibril area is 1.5% or less. (b) The average fibril circumference ratio is 5.0% or less. Newspaper paper according to claim 1 or 2, having one or more of the features of the above.

6. The newspaper paper according to claim 1 or 2, wherein the CSF of the chemical pulp is 400 mL or more.

7. The newsprint according to claim 1 or 2, wherein the chemical pulp comprises kraft pulp with a CSF of 500 mL or more and an average kink index of 1.3 (1 / mm) or more.

8. The newspaper paper according to claim 1 or 2, wherein the aforementioned chemical pulp is contained in an amount of 70% by weight or more relative to 100% by weight of pulp.

9. Newspaper paper according to claim 1 or 2, comprising a bulking agent.

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