Bulky pulp and bulky paper

Abstract

The object of the present invention is to provide bulky pulp that has a high bulkiness effect and suppresses discoloration. [Solution] The present invention provides bulky pulp and bulky paper with high bulkiness and reduced discoloration. The bulky pulp according to the present invention is bulky pulp containing chemical pulp, having a CSF of 500 ml or more and an average kink index of 1.3 (1 / mm) or more.

Description

[Technical Field]

[0001] This invention relates to bulky pulp. In particular, this invention relates to bulky pulp made from chemical pulp that has high bulkiness and is less prone to problems such as discoloration, and bulky paper containing the same. [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. 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.

[0003] One method for reducing the density (bulkness) of paper involves examining the pulp used for papermaking.

[0004] While wood pulp is generally used for papermaking, it is known that to achieve low density, 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, when mechanical pulp is used, the amount of petroleum-derived energy used in the pulping process is high, and the resulting pulp has a lower whiteness compared to chemical pulp, leading to problems such as a decrease in the overall whiteness of the paper and the paper turning yellow (fading).

[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] Japanese Patent No. 3041294 [Patent Document 5] Japanese Unexamined Patent Application Publication No. 2004-124289 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] In view of such a situation, an object of the present invention is to provide a bulky pulp having a high bulk effect and suppressing discoloration. [Means for Solving the Problems]

[0009] That is, the present invention provides, but is not limited thereto, the following. [1] A bulky pulp containing chemical pulp, wherein the CSF is 500 ml or more and the average kink index is 1.3 (1 / mm) or more. [2] The bulky pulp according to [1], wherein the average fibril area is 1.0% or less. [3] The bulky pulp according to [1] or [2], wherein the average fibril perimeter ratio is 2.0% or less. [4] The bulky pulp according to [1] or [2], wherein the chemical pulp is kraft pulp. [5] The bulky pulp according to [1] or [2], wherein the CSF is 750 ml or less. [6] A bulky paper containing 70% by weight or more of the bulky pulp according to [1] based on 100% by weight of the pulp. [7] The bulky paper according to [6], having a density of 0.5 g / cm 3 or less. [8] The bulky paper according to [6], containing a bulking agent. [Effects of the Invention]

[0010] It is to provide a bulky pulp having a high bulk effect and suppressing discoloration. According to the present invention, it is possible to provide a bulky pulp having sufficient bulkiness and capable of suppressing discoloration without using mechanical pulps such as mechanical pulp (MP) and thermomechanical pulp (TMP), and a bulky paper containing the same. [Modes for Carrying Out the Invention]

[0011] The bulky pulp of the present invention is a pulp used for low-density (bulking) of paper, which is a pulp using chemical pulp as a raw material and having a specific average kink index.

[0012] <Bulky pulp> The bulky pulp of the present invention is a chemical pulp having a specific average kink index, and in one aspect, it is a chemical pulp having a predetermined average kink index, average kink angle, fibril area, and fibril perimeter length. Examples of the raw material pulp include wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, and examples thereof include chemical pulps such as hardwood bleached kraft pulp (LBKP), hardwood unbleached kraft pulp (LUKP), softwood bleached kraft pulp (NBKP), softwood unbleached kraft pulp (NUKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), and oxygen bleached kraft pulp (OKP). Examples of the non-wood pulp are not particularly limited, and include cotton-based pulps such as cotton linter and cotton lint, and non-wood-based pulps such as hemp, wheat straw, bamboo, and bagasse. The raw material pulp may be used alone or in combination of two or more of the above. In addition, 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 easy availability, wood pulp is preferred as the raw material pulp. Also, among the wood pulps, from the viewpoint of suppressing discoloration, the raw material pulp is preferably a chemical pulp, more preferably a kraft pulp, still more preferably one or more selected from hardwood kraft pulps such as eucalyptus and acacia, and softwood kraft pulps such as pine and cedar, and even more preferably one or more selected from hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP).

[0013] <Average kink angle, average kink index> 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 angles in "An Analyzer for Fibre Shape and Length" by Olson, J et al. (Journal of Pulp and Paper Science, Vol. 21, No. 11, 1995, pp. J367-J373). 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. The average kink angle and average kink index 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.

[0014] The average kink angle of the bulky pulp is preferably 48° or higher, more preferably 49° or higher, and even more preferably 50° or higher. By setting it within this range, a bulkier paper can be obtained. The average kink index is 1.3 (1 / mm) or higher. If the average kink index is less than 1.3 (1 / mm), the pulp fibers are not bent enough, and a sufficient bulking effect cannot be obtained when the paper is made. If the average kink index exceeds 10 (1 / mm), the pulp fibers are bent too much, i.e., the fibers are damaged too much, which may cause a decrease in paper strength. Therefore, in the present invention, it is preferable to set the average kink index of the pulp to 10 or less, more preferably 8 or less or 6 or less, and it may also be 4 or less or 2.5 or less.

[0015] Furthermore, the average kink index mentioned above can be adjusted by the tree species and the pulp concentration during pulp beating. Specifically, the higher the pulp concentration during beating, the higher the average kink index, resulting in a greater number of bent fibers in the pulp fibers that make up the paper base material.

[0016] 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 by an automated optical analysis method using a commercially available fiber length measuring device. 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.

[0017] 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 per 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.

[0018] <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 fibers."

[0019] The water drainage (also known as Canadian Standard Freeness, CSF) of bulky pulp is preferably 500 ml (CSF) or higher, and more preferably 600 ml or higher, 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 it is less than 500 ml, the pulp may become too short-fibered and fibrillated, and the bulkiness effect may not be sufficiently obtained. Also, 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 paper with inferior strength and backing. It should be noted that the fiber characteristics of the raw pulp used to prepare bulky paper do not differ significantly from the fiber characteristics of the disintegrated pulp obtained by disintegrating bulky paper. For example, the length-weighted average fiber length of the pulp constituting the paper base can be appropriately adjusted by adjusting the length-weighted average fiber length of the raw pulp, and the same applies to other fiber characteristics. Pulp disintegration can be carried out in accordance with JIS P8220-1:2012. Furthermore, when analyzing pulp characteristics such as average kink index, fiber length, and water filtration efficiency from paper, pulp samples can be prepared using the following method. (Method for preparing pulp samples from paper) Cut a 40cm x 40cm piece of paper, immerse it in deionized water to adjust the solid content to 2% by mass, and immerse for 24 hours. After 24 hours of immersion, disintegrate the pulp into fibers using a standard disintegrator (manufactured by Kumagai Riki Kogyo) in accordance with JIS P8220-1. Even if the paper has a printed layer, disintegration may be performed with the printed layer included. The obtained pulp fiber sample can be used for analysis of various pulp properties.

[0020] In the bulky pulp of the present invention, it is preferable to use kraft pulp (BKP) that has been bleached by one or more known bleaching processes, from the viewpoint of suppressing discoloration of pulp and bulky paper. In this case, an oxidizing agent such as hydrogen peroxide, ozone, or peracetic acid, or a reducing agent such as hydrosulfite (sodium dithionite), sodium bisulfate, sodium borohydride, or formamidine sulfinic acid (FAS) can be used.

[0021] <Bulky paper> Bulky paper can be obtained by manufacturing paper using the bulky pulp of the present invention as a raw material. The bulky paper according to the present invention has a low density due to the use of bulky pulp, and in one embodiment the density of the paper is 0.50 g / cm³. 3 The following is the present invention. The bulky paper of the present invention can be obtained without using raw materials containing a large amount of lignin or hemicellulose, such as mechanical pulp, thus suppressing fading during long-term storage and when the paper is exposed to sunlight. The bulky paper of the present invention can be used as uncoated paper, coated base paper, and white cardboard. As uncoated paper, it is preferably used for newsprint, fine paper, printing paper, PPC paper, publishing paper, book paper, and cardboard. It is especially preferable to use it for newsprint, publishing paper, and book paper, which conventionally used a large amount of mechanical pulp. Furthermore, the bulky paper of the present invention can also be used as coated base paper with a pigment coating layer, and can be used for lightly coated paper, A2 coated paper, A3 coated paper, etc. In addition, the above-mentioned coated paper and uncoated paper can be used in applications where bulkiness is required, such as packaging and wrapping.

[0022] <Paper making raw materials> The bulky paper of the present invention contains at least the bulky pulp described above. The bulky pulp content is preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, based on 100% by weight of pulp. By increasing the bulky pulp content of the present invention, it is possible to produce paper that is even bulkier.

[0023] The bulky paper of the present invention may use only bulky pulp as the pulp, or it may use two or more different types of bulky pulp, or it may use bulky pulp in combination with pulp other than bulky pulp. However, from the viewpoint of environmental impact such as greenhouse gas reduction and discoloration, it is preferable not to use mechanical pulp such as wood pulp (GP), thermomechanical pulp (TMP), or chemothermetic pulp (CTMP). Examples of pulps other than bulky pulp that can be used include wood pulp, non-wood pulp, and deinked 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), 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 bulky paper, 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. In addition, 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 may be mixed into the raw material pulp.

[0024] The bulky paper 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 bulky paper 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.

[0025] When using the bulky paper of the present invention for applications such as printing paper where bleed-through is required, it is preferable to add a filler, more preferably calcium carbonate which has a high opacity-improving effect, and even more preferably light calcium carbonate which provides an even higher opacity-improving effect.

[0026] Furthermore, since the bulky paper of the present invention may have weaker interfiber bonding and lower paper strength compared to high-density paper, it is preferable to add a drying strength agent that can strengthen interfiber bonding. The drying strength agent is more preferably polyacrylamide (PAM) and / or starch.

[0027] In the papermaking of bulky paper, 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. Next, the paper layers formed by the papermaking machine are 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.

[0028] Furthermore, the bulky paper obtained as described above may be subjected to surface treatment with a calender to the extent that it does not impair the bulkiness effect of the bulky pulp, thereby uniformizing the thickness and profile and improving printability. A known calendering machine can be appropriately selected and used for the calendering process.

[0029] Furthermore, in the bulky 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. 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 chemicals 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 bulking paper of the present invention, the preferred amount added during the papermaking process is 0.1 to 2% of the pulp, more preferably 0.2 to 1.5%. By using pulp having a specific filtration rate and average kink index according to the present invention in combination with a bulking agent, it is possible to obtain paper with a higher bulk.

[0030] 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, or a pigment coating may be applied by adding a pigment. 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, and lubricants may be added to perform the clear coating.

[0031] <Adhesive> In the present invention, a coating layer containing a pigment and an adhesive may be provided on bulky paper. For the adhesive used during 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, and vinyl acetate-butyl acrylate; synthetic adhesives such as polyvinyl alcohol, maleic anhydride copolymer, and acrylic acid-methyl methacrylate copolymer; proteins such as casein, soy protein, and synthetic protein; starches such as oxidized starch, cationized starch, urea phosphate esterified starch, and hydroxyethyl etherified starch; and cellulose derivatives such as carboxymethylcellulose, hydroxymethylcellulose, and hydroxyethylcellulose.

[0032] <Pigments> 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.

[0033] When a coating layer containing the pigment and adhesive of the present invention 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.

[0034] The bulky paper of the present invention preferably contains a black colorant and / or two or more colorants of different hues. By including the above-mentioned colorants, it is possible to obtain paper with a subdued color tone, similar to conventional bulky papers containing mechanical pulp or recycled paper pulp, while still containing a large amount of bleached kraft pulp with high whiteness. Furthermore, since the opacity is further improved by using the above-mentioned colorants, it is possible to reduce print show-through when used as printing paper or book paper. Examples of black colorants include carbon black pigments such as furnace black, lamp black, acetylene black, channel carbon, and thermal black; magnetic fine particles such as magnetite and ferrite; aniline black, titanium black, copper oxide, iron oxide, and phthalocyanine black. In the present invention, from the viewpoint of dyeing efficiency, it is preferable to include the colorants internally. The two or more colorants of different hues may be dyes or pigments, and examples include colorants having red, yellow, brown, green, blue, and purple hues. The aforementioned colorant is preferably added to uncoated paper or lightly coated paper, where the color of the base paper directly corresponds to the color of the finished product.

[0035] The coating method and coating apparatus used in the clear coating or pigment coating of the present invention are not particularly limited, and known coating apparatus can be used, and it is preferable to use a rod metering type size press, a pound type size press, a gate rod coater, a spray coater, a blade coater, a bar coater, an air knife coater, a curtain coater, etc.

[0036] The bulky paper coated and dried as described above can be subjected to calendering. However, in the present invention, since it may impair the bulkiness of the bulky paper, it is better not to perform calendering or to perform a slight calendering. By not performing calendering, a bulky paper having high bulkiness can be obtained.

[0037] <Basis weight> The basis weight of the bulky paper of the present invention is not particularly limited, but is 30 g / m 2 or more and 300 g / m 2 or less. In one aspect, the basis weight of the paper according to the present invention can be 35 to 200 g / m 2 or 40 to 100 g / m 2 and may be 45 to 80 g / m 2

[0038] <Density> The density of the bulky paper of the present invention is preferably 0.50 g / cm 3 or less, more preferably 0.48 g / cm 3 or less. By setting it within the above range, a bulky paper having sufficient bulkiness can be obtained. The lower limit value of the density is not particularly limited, but for example, it may be 0.30 g / cm 3 or more or 0.35 g / cm 3 or more.

[0039] <Ash content> In the present invention, since the bulky pulp can be used to lower the density of the paper and improve the opacity of the paper, it is not necessary to add a filler (ash content: about 0%). When adding a filler, the ash content of the base paper is preferably 3% or more and 30% or less, more preferably 6% or more and 15% or less, and still more preferably, the upper limit is 10% or less. Since the filler in the paper inhibits the bonding between fibers, if the ash content becomes too high, the paper strength may be reduced, and the bulkiness and strength may be impaired.

[0040] <Opacity> ​In this invention, the opacity of the paper can be measured in accordance with JIS-P8149:2000. The upper limit of opacity is not limited, but considering its use in applications where opacity is required, it is preferably 78% or higher, 79% or higher, or 80% or higher, more preferably 85% or higher, and even more preferably 90% or higher or 92% or higher. Furthermore, in this invention, it is preferable that the bleed-through value is 85% or higher. Here, the bleed-through value is the value obtained by measuring the reflectance of the back surface of the printed surface using X-Rite520 (manufactured by X-Rite Corporation) and dividing the reflectance of the back surface of the printed surface by the reflectance of the back surface of the unprinted surface. A larger value indicates less bleed-through.

[0041] <Hue> When the bulky paper of the present invention is used, for example, as book paper, it is exposed to light from a light source including ultraviolet light according to JIS P8150. * a * b * The values ​​are L * 80 or more and 98 or less, a * -5 or more and 3 or less, b * -3 to 20 is preferable, and more preferably L * 82 or more and 96 or less, a * -4.5 or more and 2 or less, b * -2 to 19, and more preferably L * 83 or more and 95 or less, a * -4 or more and 1.5 or less, b * The value is between 0 and 18. Within this range, it is possible to obtain bulky paper with the same texture as conventional book paper, and furthermore, it can be made into bulky paper that is preferred by users in terms of aesthetics when books are displayed in stores and eye strain when reading. [Examples]

[0042] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and percentages in this specification are based on weight, and numerical ranges are given including their endpoints.

[0043] ■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: Measured according to JIS P 8116. (4) Ash content: Measured according to JIS P 8251. (5) Fadeability The 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. ○: The color remained almost unchanged and did not fade. ×: The color had changed to a yellowish hue and faded. Furthermore, the fading properties (ΔE) were evaluated according to JAPAN TAPPI No. 21 "Paper and Cardboard - Fading Test Method". An Atlas weatherometer Ci35W (Toyo Seiki Seisakusho) was used, with an irradiance of 60 W / m². 2 For bulky paper that was 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 before and after fading was measured, and ΔE was calculated according to the following formula, and the fading resistance was evaluated according to the following criteria. The 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 by diffuse illumination". ΔE*=((ΔL*)^2+(Δa*)^2+(Δb*)^2)^(1 / 2) (6) Fiber analysis The water filtration rate of pulp fibers was measured according to JIS P 8121-2. Average fiber length, average fiber width, total fineness, 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 P 8220-1 was used as a sample (solid content concentration: 2% by mass). 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. 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)

[0044] ■ Paper manufacturing and evaluation [Example 1] 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. 2The bulky paper was manufactured to achieve the following characteristics. The paper quality and other specifications are as shown in Table 1. [Example 2] Bulky paper was manufactured in the same manner as in Example 1, except that NBKP (imported material) prepared in CSF675ml was used. [Example 3] Bulky paper was manufactured in the same manner as in Example 1, except that NBKP (domestic material) prepared in CSF680ml was used. [Example 4] Bulky paper was manufactured in the same manner as in Experiment 1, except that NBKP was used after fluff pulping to obtain a CSF of 715 ml. [Example 5] Bulky paper was manufactured in the same manner as in Experiment 1, except that LBKP with a CSF of 765 ml, which was subjected to fluff pulping treatment, was used. [Example 6] Bulky paper was manufactured in the same manner as in Example 1, except that the amount of light calcium carbonate added as a filler was changed to achieve an ash content of 4.5% in the paper. [Example 7] Bulky paper was manufactured in the same manner as in Example 1, except that the amount of light calcium carbonate added as a filler was changed to achieve an ash content of 11.6% in the paper. [Example 8] Bulky paper was manufactured in the same manner as in Example 1, except that the amount of bulking agent added was changed to 1%. [Example 9] Bulky paper was manufactured in the same manner as in Example 8, except that no bulking agent was added. [Comparative Example 1] Bulky paper was manufactured in the same manner as in Example 1, except that bleached TMP (thermomechanical pulp) prepared in 158 ml of CSF was used. [Comparative Example 2] Bulky paper was manufactured in the same manner as in Example 1, except that the LBKP from Example 1 was further beaten to prepare LBKP with a CSF content of 390 ml. [Comparative Example 3] Bulky paper was manufactured in the same manner as in Comparative Example 2, except that a 1% bulking agent was added.

[0045] [Table 1]

[0046] The results in Table 1 show 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, Examples 1 to 9, which used pulp with an average kink index of 1.3 or higher, were bulky despite not containing mechanical pulp. Furthermore, the bulky paper containing the bulky pulp of the present invention had particularly excellent fade resistance because it does not contain mechanical pulp.

[0047] [Comparative Example 2-1] Bulky paper was manufactured in the same manner as in Comparative Example 1, except that aluminum sulfate, PAM (polyacrylamide), cationized starch, bulking agent, yield agent, and light calcium carbonate were not added. [Comparative Example 2-2] Bulky paper was manufactured in the same manner as in Comparative Example 2, except that aluminum sulfate, PAM, cationized starch, bulking agent, yielding agent, and light calcium carbonate were not added. [Example 2-1] Bulky paper was manufactured in the same manner as in Example 1, except that aluminum sulfate, PAM, cationized starch, bulking agent, yielding agent, and light calcium carbonate were not added. [Example 2-2] Bulky paper was manufactured in the same manner as in Example 4, except that aluminum sulfate, PAM, cationized starch, bulking agent, yielding agent, and light calcium carbonate were not added.

[0048] [Table 2]

[0049] 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. From the 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.

Claims

1. Bulky pulp containing chemical pulp, wherein the CSF is 500 ml or more and the average kink index is 1.3 (1 / mm) or more.

2. The bulky pulp according to claim 1, wherein the average fibril area is 1.0% or less.

3. The bulky pulp according to claim 1 or 2, wherein the average fibril circumference ratio is 2.0% or less.

4. The bulky pulp according to claim 1 or 2, wherein the chemical pulp is kraft pulp.

5. The bulky pulp according to claim 1 or 2, wherein the CSF is 750 ml or less.

6. Bulky paper containing 70% by weight or more of the bulky pulp described in claim 1, relative to 100% by weight of pulp.

7. Density is 0.5 g / cm³ ３ The bulky paper according to claim 6, as follows:

8. The bulky paper according to claim 6, comprising a bulking agent.

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