Paper and methods for manufacturing the same

Abstract

The object of the present invention is to provide high-quality paper made from kraft pulp and methods for producing the same. [Solution] The present invention provides a paper, a paper, in which the paper raw material includes kraft pulp and the density and tear length, or density and bending stiffness, are in a predetermined relationship, and a method for manufacturing the said paper using kraft pulp as the paper raw material. The kraft pulp has a volumetric weight of 635 kg / m³. 3 Preferably, the material is obtained by pulping kraft pulp from wood raw materials with a fiber length of 1.1 mm or less. The pulp pulp pulping is preferably carried out under conditions where the active alkali addition rate is 5 to 40%.

Description

[Technical Field]

[0001] This invention relates to paper and methods for manufacturing 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, and biomass fuel is expected to become increasingly important in the future from the perspective of carbon neutrality. Furthermore, large-scale commercial afforestation is an effective method for absorbing and sequestrating CO2 and increasing the production of biomass resources. When implementing commercial afforestation, cost reduction is essential, and therefore, increasing the yield (weight) of biomass obtained per unit area is a challenge. Wood chips obtained from commercial afforestation are transported by chip carriers. Chip carriers have limited loading capacity, and there is a need for high-volume, high-heavyweight chips that can carry a larger volume of chips in the same volume (reducing transportation costs).

[0003] Patent Document 1 states a volumetric weight of 450 kg / m³. 3 It has been reported that using the above-mentioned mechanical pulp derived from the eucalyptus genus in the production of coated paper for printing allows for the maintenance of the bulky structure of the base paper and the production of low-density coated paper for printing. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-106421 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] While mechanical pulp, such as that described in Patent Document 1, can easily produce higher quality paper than kraft pulp, it tends to consume more electricity because it is manufactured by mechanically defibrating wood or chips. As a result, it may contribute to an increase in greenhouse gas (GHG) emissions, which have become a global concern in recent years.

[0006] The object of the present invention is to provide high-quality paper made from kraft pulp and methods for producing the same. [Means for solving the problem]

[0007] The present invention provides the following [1] to [6]. [1] The paper raw material contains kraft pulp, A paper whose density and tear length are related by the following equation 1. (Formula 1) B≧26.537×A-8.153 (In Equation 1, A is density (g / cm³) 3 ) represents the fracture length (km), where 0.3 ≤ A ≤ 0.7. [2] The paper described in [1], wherein the density and bending stiffness are related by the following equation 2. (Formula 2) C ≥ -387.35 × A + 510.75 (In equation 2, A is density (g / cm³) 3 ) represents the case where 0.3 ≤ A ≤ 0.7. C is the bending stiffness (μN·m 2 (represents / m) [3] A method for manufacturing paper according to [1] or [2], using kraft pulp as a paper raw material. [4] Volumetric weight 635kg / m 3 The method for producing paper according to [3], further comprising: digesting wood raw materials with a fiber length of 1.1 mm or less to obtain kraft pulp; and producing paper using pulp containing the kraft pulp as a raw material. [5] The method for manufacturing paper according to [3] or [4], wherein the kraft pulp is digested under conditions of an activated alkali addition rate of 5 to 40%. 〔6〕The method for producing paper according to 〔4〕or〔5〕, wherein at least one treatment selected from delignification treatment, bleaching treatment, and beating treatment is performed after kraft pulp digestion.

Advantages of the Invention

[0008] According to the present invention, there are provided paper having good quality and showing paper properties equivalent to those of mechanical pulp, and a method for producing the same. Usually, in mechanical pulp, since wood or chips are mechanically defibrated, the power consumption tends to increase, which may lead to an increase in greenhouse gas (GHG) emissions, which has been regarded as a problem on a global scale in recent years. According to the present invention, since paper having paper properties equivalent to those of mechanical pulp can be obtained, an alternative material for mechanical pulp can be provided, and it is expected to contribute to power consumption reduction, carbon neutrality, and achievement of SDGs.

Brief Description of the Drawings

[0009] [Figure 1] Figure 1 is a graph showing the relationship between the breaking length and density in the examples. [Figure 2] Figure 2 is a graph showing the relationship between the bending strength and density in the examples.

Modes for Carrying Out the Invention

[0010] 〔1. Physical Properties of Paper〕 - Density and Breaking Length - The paper preferably has a relationship between density and breaking length as shown in Formula 1. (Formula 1) B ≧ 26.537 × A - 8.153 In Formula 1, A represents the density (g / cm 3 ), where 0.3 ≦ A ≦ 0.7, preferably 0.4 ≦ A ≦ 0.65. B represents the breaking length (km), and B > 0. The breaking length can be measured in accordance with JIS P 8113:2006.

[0011] - Density and Bending Strength - The paper preferably has a relationship between density and bending strength as shown in Formula 2. (Formula 2) C ≥ -387.35×A + 510.75 In Formula 2, A represents the density (g / cm 3 ), and 0.3 ≤ A ≤ 0.7. C represents the bending stiffness (μN·m 2 / m). The bending stiffness can be measured in accordance with ISO2493-2:2020.

[0012] - Density - The density is calculated from the value obtained by dividing the basis weight of the paper by the paper thickness, and is usually 0.3 to 0.7 g / cm 3 , preferably 0.4 to 0.65 g / cm 3 , more preferably 0.45 to 0.6 g / cm 3 .

[0013] The paper satisfying (Formula 1) or (Formula 2) can exhibit good bulkiness, strength, or stiffness. Also, since the bulkiness, strength, and stiffness at the same density are good, weight reduction is possible when used as the base paper for coated paper, etc., and cost reduction and resource conservation can also be achieved. Therefore, the paper can be used in various applications such as printing paper and packaging materials.

[0014] [2. Paper raw material] The paper of the present invention is paper obtained using kraft pulp as the paper raw material. In this specification, kraft pulp is fibers taken out from wood raw materials by the kraft pulping method using active alkali. The kraft pulp is preferably prepared from wood raw materials having a volume weight of 635 kg / m 3 or more and a fiber length of 1.1 mm or less.

[0015] - Volume weight - The volume weight of the wood, which is the raw material of the kraft pulp, is 635 kg / m 3 or more, preferably 650 kg / m 3That concludes the explanation. Wood that meets the above bulk density values ​​tends to have a structure with thick fiber walls (film thickness) and few voids (lumen diameter). Since most of the water in wood resides in the voids, a structure with fewer voids can make it less likely to absorb water. Furthermore, wood that meets the above bulk density values ​​can transport a larger amount of wood at once for the same volume compared to wood that does not, thus improving transportation efficiency. In addition, since it can be produced from wood with a higher carbon dioxide sequestration capacity, mass production of such wood chips can increase carbon dioxide sequestration, contributing to the realization of a sustainable society as a measure to mitigate global environmental change and curb global warming. The upper limit is typically 800 kg / m 3 Preferably 750 kg / m 3 More preferably, 730 kg / m 3 More preferably, 720 kg / m 3 The following are just examples, and are not limited to these.

[0016] Volumetric gravity is the ratio of weight to volume. Volumetric gravity can be measured by placing the sample into a graduated cylinder filled with water, reading the increase in volume, confirming the increase in volume, drying the chip, and measuring the weight when completely dry (JAPAN TAPPI No.3:2000). The measurement method in the examples described later is the same.

[0017] -Fiber length- The fiber length of kraft pulp is typically 1.1 mm or less, preferably 1.05 mm or less, and more preferably 1 mm or less. The lower limit is typically 0.5 mm or more, preferably 0.55 mm or more, more preferably 0.60 mm or more, and even more preferably 0.65 mm or more. These are just examples and are not particularly limited.

[0018] The fiber length can be measured as a length-weighted average fiber length using a fiber tester (Lorentzen & Wettre) in accordance with JIS P 8226:2011 "Pulp - Method for measuring fiber length by optical automated analysis," and the measurement method in the later examples is the same.

[0019] -Trees- The wood raw materials for kraft pulp are usually derived from plants, and these plants are usually woody plants. Woody plants are usually forest trees, such as broad-leaved trees like eucalyptus, acacia, birch, and beech, and coniferous trees like Japanese red pine, Japanese cedar, and Japanese cypress. Broad-leaved trees are preferred, more preferably plants of the Acacia and Eucalyptus genera, and even more preferably plants of the Eucalyptus genera. Eucalyptus plants grow quickly, resulting in a large yield of wood chips, making them suitable for fuel chips. Furthermore, after logging, reforestation is possible through coppicing from the stumps, enabling sustainable afforestation.

[0020] Examples of plants of the genus Eucalyptus include Eucalyptus pellita, Eucalyptus brassiana, Eucalyptus urophylla×Eucalyptus grandis, Eucalyptus pellita×Eucalyptus brassiana, Eucalyptus urophylla, Eucalyptus grandis, Eucalyptus maculata, Eucalyptus tereticornis, Eucalyptus camaldulensis, Eucalyptus rudis, Eucalyptus resinifera, Eucalyptus propinqua, Eucalyptus sideroxylon, Eucalyptus botryoides, Eucalyptus viminalis, Eucalyptus saligna, Eucalyptus ovata, Eucalyptus globulus, Eucalyptus nitens, Eucalyptus saligna, Eucalyptus Examples include *Eucalyptus cladocalyx*, *Eucalyptus urograndis*, and hybrids of two or more tree species selected from these. Of these, those suitable for the plantation environment (for example, tree species adaptable to tropical conditions when planting in the tropics) can be selected, but *E. pellita*, *E. brassiana*, *E. urophylla*, *E. urograndis*, hybrids of *E. brassiana* and *E. pellita*, hybrids of *E. urophylla* and *E. pellita*, and hybrids of two or more tree species selected from these are preferred, with hybrids of *E. brassiana* and *E. pellita* and *E. urograndis* being more preferred. High bulk density (e.g., 500 kg / m³) is desirable. 3 (As described above) It is believed that individuals with superior traits can be obtained by crossbreeding individuals and selecting the resulting F1 individuals.

[0021] The plants from which the timber is derived are usually plantation trees grown from clonal or seedling seedlings. The age of the trees is not particularly limited; any age at which timber can be obtained is acceptable (usually 2 years or more), preferably 5 years or more. While there is no upper limit from a quality standpoint, a shorter age is preferable from an economic perspective. In the case of eucalyptus plants, depending on the plantation area, the age is usually 15 years or less, preferably 10 years or less.

[0022] The wood raw material for kraft pulp may be wood derived from a single plant, or a combination of two or more woods derived from plants of different species and ages. The method for producing kraft pulp from wood raw material is not particularly limited, but the method described below is preferred.

[0023] -Pulps other than kraft pulp- The paper raw material may include pulp other than kraft pulp. Examples include pulp obtained by chemical methods other than the kraft method, such as the sulfite method, soda method, or polysulfide method (chemical pulp); pulp obtained by mechanical methods using equipment such as refiners and grinders (mechanical pulp); and pulp produced by a method in which chemical pretreatment is followed by mechanical force (semi-chemical pulp). The proportion of kraft pulp in the paper raw material is preferably 90% by weight or more, more preferably 95% by weight or more, even more preferably 98% by weight or more, even more preferably 99% by weight or more (substantially containing no raw materials other than kraft pulp), and particularly preferably 100% by weight (consisting solely of kraft pulp).

[0024] [3. Paper manufacturing method] Paper can be manufactured using kraft pulp as a raw material. -Method of manufacturing kraft pulp- Kraft pulp has a volumetric weight of 635 kg / m³. 3 Furthermore, kraft pulp manufactured from wood raw materials with a fiber length of 1.1 mm or less is preferred. The bulk density and fiber length are as described above.

[0025] -Wood raw materials- The wood raw material can be prepared from the aforementioned plants (e.g., eucalyptus plants) according to conventional methods, for example, wood chips. Methods for manufacturing wood chips include, for example, removing the bark from the woody parts (trunk and branches) after felling the plant, and then cutting or crushing it. The size of the wood chips is not particularly limited and can be determined according to its intended use.

[0026] -Kraft pulp distillation- Wood raw materials can be subjected to kraft pulp digestion to obtain kraft pulp. Kraft pulp digestion can be carried out by the kraft process. Kraft pulp digestion may also be carried out by a modified kraft process such as MCC, EMCC, ITC, or Lo-solid. In addition, examples of digestion types for kraft pulp digestion include single-vessel liquid phase, single-vessel gas / liquid phase, double-vessel liquid / gas phase, and double-vessel liquid phase, and any of these may be used.

[0027] (Activated alkali addition rate) In kraft pulp digestion, the active alkali addition rate is preferably 5% or more, more preferably 8% or more, and even more preferably 10% or more. This allows for sufficient removal of lignin and hemicellulose. The upper limit is preferably 40% or less, more preferably 30% or less, and even more preferably 20% or less. This suppresses a decrease in quality and / or yield, and allows for efficient digestion of kraft pulp. Therefore, 5-40% is preferred, more preferably 8-30%, and even more preferably 10-20%. In this specification, the active alkali addition rate is the addition rate of Na2O per unit weight of oven-dry wood chips, and is a converted value where the total addition rate of NaOH and Na2S is used as the addition rate of Na2O. That is, the addition rate of Na2O can be converted by multiplying the amount of NaOH added by 0.775 and the amount of Na2S added by 0.795.

[0028] (sulfidity) A sulfidation degree of 20% or higher is preferable. This helps to suppress the decrease in delignin properties and / or pulp viscosity, as well as the increase in the pulp content. The upper limit is usually 35% or less.

[0029] (Temperature conditions) Temperature control during kraft pulping is performed, for example, so that the maximum temperature is preferably 180°C or lower, more preferably 160°C or lower. This suppresses the decrease in the degree of polymerization (viscosity) of cellulose. The minimum temperature is preferably 120°C or higher, more preferably 140°C or higher. This allows for sufficient deligninization. The holding time (the time from when the pulping temperature reaches the maximum temperature until the temperature begins to decrease) is preferably 60 minutes or more, more preferably 120 minutes or more. This allows for sufficient pulping to proceed. The upper limit is preferably 600 minutes or less, and even more preferably 360 minutes or less. Pulping does not proceed if the pulping time is less than 60 minutes, and it is undesirable if it exceeds 600 minutes because the pulp production efficiency deteriorates.

[0030] (H Factor) In Kraft pulping, the H-factor (Hf) is preferably 300 to 2000, more preferably 350 to 1500, and even more preferably 400 to 1000. In this specification, Hf is an indicator of the total amount of heat supplied to the reaction system during the pulping process and is expressed by the following formula. Hf = ∫exp(43.20 - 16113 / T)dt [In the formula, T represents the absolute temperature at a given point in time.] Hf can be used as an indicator of the total amount of heat supplied to the reaction system during the pulping process, and the conditions for Kraft pulping (e.g., processing temperature and processing time) can be set using Hf as an indicator.

[0031] -Delignin treatment- It is preferable that the pulp after pulp digestion be deligned. Deligning can be carried out by conventional methods, but oxygen deligning is preferred. An example of oxygen deligning is as follows: An alkaline agent (e.g., NaOH) is added to the kraft pulp after digestion to make it alkaline, and then chemicals are added as needed, and oxidation is carried out under oxygen pressure. The pulp concentration in the system can be either 8-15% by mass (medium concentration method) or 20-35% by mass (high concentration method). The oxygen pressure (starting pressure) is, for example, 3-9 Bar, preferably 4-7 Bar. The amount of alkaline agent added (relative to the weight of oven-dry pulp) is, for example, 0.5-5%, preferably 1-3%. The temperature is, for example, 80-120°C, preferably 85-105°C. The amount of oxygen added (relative to the weight of oven-dry pulp) is, for example, 0.5-5%, preferably 1-3%. The reaction time is, for example, 30 to 180 minutes, preferably 60 to 90 minutes.

[0032] -Bleaching treatment- Examples of bleaching treatments include chlorine treatment (C), chlorine dioxide bleaching (D), alkaline extraction (E), hypochlorite bleaching (H), hydrogen peroxide bleaching (P), alkaline hydrogen peroxide treatment stage (Ep), alkaline hydrogen peroxide / oxygen treatment stage (Eop), ozone treatment (Z), chelation treatment (Q), and combinations of two or more of these treatments. Examples of combinations (sequences) of two or more treatments include DE / PD, C / DEHD, ZED-PZ / D-Ep-D, Z / D-Ep-DP, D-Ep-D, D-Ep-DP, D-Ep-PD, Z-Eop-DD, Z / D-Eop-D, Z / D-Eop-DED (the " / " in the sequence means that the treatments before and after the " / " are performed consecutively without washing), and other commonly used methods, with DE / PD being preferred. The temperature during each treatment is, for example, 40 to 90°C, preferably 50 to 80°C. The reaction time for each treatment is, for example, 30 to 180 minutes, preferably 50 to 90 minutes. The whiteness of the pulp after bleaching (ISO 2470-1:2016) is preferably 80% or higher.

[0033] -Beaten Processing- The beating process is preferably carried out using equipment such as high-speed rotary, colloidal mill, high-pressure, roll mill, or ultrasonic devices. Examples of such equipment include high-pressure or ultra-high-pressure homogenizers, refiners, beaters, PFI mills, kneaders, dispersers, high-speed dissociators, and top finers, which involve the interaction of metal or blades with pulp fibers around a rotating axis, or those that utilize friction between pulp fibers.

[0034] -Papermaking process- The aforementioned paper can be manufactured by papermaking using the aforementioned kraft pulp. Papermaking may be carried out, for example, by a process of forming a sheet from kraft pulp. Sheet formation may be carried out, for example, according to Japanese Industrial Standard (JIS) P 8122 "Pulp - Method for preparing test handmade paper" (1989 edition), and one example is a method of forming pulp into a sheet using a paper machine. When forming pulp into a sheet, additives commonly used in papermaking may be added to the pulp. Examples of such additives include paper strength enhancers, bulk enhancers, pigments, yield enhancers, water filtration enhancers, internal sizing agents (rosin-based sizing agents, aluminum sulfate, etc.), pH adjusters, defoamers, pitch control agents, and slime control agents. The amount of such additives used is not particularly limited and should be within a range that does not impair the effects of the present invention.

[0035] When forming the sheets, paper raw materials other than kraft pulp may be used, such as rayon fibers and other materials. The paper raw materials may be pre-formed into the shape of sheets, films, rolls, etc., along with the pulp obtained from the above-mentioned Eucalyptus plants. The paper raw materials may contain pulp made from other plants, but it is preferable that they do not.

[0036] Examples of paper machines include known paper machines that combine papermaking methods from two or more paper machines selected from among long-wire paper machines, round-wire paper machines, gap formers, hybrid formers, multi-layer paper machines, and paper machines with a long-wire wire wire wire wire wire, gap formers, hybrid formers, multi-layer paper machines, and paper machines with a long-wire wire wire wire wire selected from among these. The press line pressure in the paper machine and the calender line pressure when calendering is performed in the subsequent stage should both be set within a range that does not impair operability or the performance of the resulting plasticized cellulose.

[0037] [4. Uses of paper] The paper of the present invention, by satisfying (Formula 1) or (Formula 2), easily gains bulk, and therefore exhibits bulkiness even with a small amount of bulking agent added. Furthermore, because it easily gains strength at the same density, high-strength paper can be obtained even with a small amount of paper strength enhancer added.

[0038] Applications of the paper of the present invention include, for example, printing paper, newspaper, inkjet paper, PPC paper, form paper, kraft paper, fine paper, coated paper, lightly coated paper, wrapping paper, tissue paper, colored fine paper, cast coated paper, carbonless paper, label paper, thermal paper, various fancy papers, water-soluble paper, release paper, process paper, wallpaper base paper, flame-retardant paper (non-combustible paper), laminate base paper, printed electronics paper, battery separators, cushion paper, tracing paper, impregnated paper, ODP paper, building material paper, decorative material paper, envelope paper, tape paper, heat exchange paper, synthetic fiber paper, sterilization paper, water-resistant paper, oil-resistant paper, heat-resistant paper, photocatalytic paper, decorative paper (such as oil-absorbing paper), various sanitary papers (toilet paper, tissue paper, wipers, diapers, sanitary products, etc.), tobacco paper, cardboard (liners, core paper, white cardboard, etc.), paper plate base paper, cup base paper, baking paper, abrasive paper, synthetic paper, and more. Of these, printing paper, inkjet paper, PPC paper, form paper, kraft paper, fine paper, coated paper, lightly coated paper, and wrapping paper are preferred because they have good strength and stiffness at the same density. [Examples]

[0039] Examples 1-3 and Comparative Examples 1-9 Approximately 200,000 seedlings (seedlings) of Eucalyptus species, including species and hybrids adaptable to tropical and subtropical regions, were created and planted in a Brazilian plantation. The seedlings (age at planting: 100 days after cutting) underwent rooting treatment in a greenhouse with a watering system for approximately 100 days after sowing (approximately 3 weeks, high humidity (approximately 100%), shading), then in an acclimatization room (gradual decrease in shading and humidity), and finally in a field before being planted in the plantation during the rainy season (late December to June) (planting density: 1666 trees / ha). After approximately 4 years of care, the trees were selected based on timber volume and tree shape, narrowing the selection down to approximately 200 individuals. Subsequently, the selected individuals were felled, and clonal seedlings were propagated from the sprouts by cuttings. The cloned seedlings were transplanted to sand-cultivated shelves, where they were allowed to grow branches as mother trees. These branches were then propagated by cuttings to increase the number of cloned seedlings. Subsequently, a second planting trial was conducted using the cloned seedlings (30 trees per line). After four years of cultivation, the timber volume, tree shape, and uniformity of the clones were checked, and the selection was narrowed down to 40 clones. Then, large-scale propagation by cuttings was carried out using the mother trees in the sand-cultivated shelves, and a third large-scale planting trial was conducted using the cloned seedlings (500 trees per line). After four years of cultivation, the timber volume, tree shape, uniformity, and disease resistance of the clones were evaluated over a large area, and the selection was narrowed down to 10 clones. Subsequently, a pulping suitability test was conducted in accordance with TAPPI JAPAN standards, and several clones were selected. This process was repeated for five years, and selections were made from a total of 1 million individuals to select clones A to C (Examples 1 to 3).

[0040] Clones A and B were E. pellita × E. brassiana, and clone C was E. brassiana × E. pellita.

[0041] [Preparation and physical property testing of wood chips] (1) Preparation of the tip The bark was removed from the woody portions of clones A to C, and wood chips were obtained by cutting. The wood chips were sieved using a gyroshifter, and fractions ranging from 25.4 mmΦ pass to 9.5 mmΦ on were used for digestion testing. The volumetric weight of the chips obtained from clones A to C is 655 kg / m³. 3 , 640 kg / m 3 , 660 kg / m3 The fiber lengths were 0.88 mm, 0.85 mm, and 0.90 mm, and the tree ages were 6.5 years, 6.0 years, and 6.8 years.

[0042] (2) Digestion test (KP digestion) KP pulp was obtained from each material by digestion in a 2.5L rotary autoclave (multi-digester). The digestion conditions were as shown in Table 1.

[0043] [Table 1]

[0044] When the volumetric gravity of the obtained clones was measured, clone A was found to be 655 kg / cm³. 3 Clone B has a weight of 640 kg / cm³. 3 Clone C is 660 kg / cm³ 3 The results were as follows: When the fiber lengths were measured, clone A was 0.88 mm, clone B was 0.85 mm, and clone C was 0.90 mm. The fiber length was measured as the length-weighted average fiber length using a fiber tester (Lorentzen & Wettre) in accordance with JIS P 8226:2011 "Pulp - Method for measuring fiber length by optical automated analysis". The bulk density was measured in accordance with J TAPPI NO.3:2000 "Wood chips - Method for testing bulk density".

[0045] (3) Oxygen delignin The unbleached pulp obtained in (2) was subjected to oxygen delignin in an acid decontamination apparatus (CRS: Multipurpose Reactor, manufactured by CRS Reactor Engineering AB). The conditions for oxygen delignin were as shown in Table 2.

[0046] [Table 2]

[0047] [Notes on Table 2] The amount of oxygen added and the amount of NaOH added are expressed as percentages (%) of the weight of the oven-dried pulp.

[0048] (4) Bleaching test (chlorine bleaching) The pulp obtained in (3) was hand-bleached using the D0-E / P-D1 flow. The bleaching conditions were as shown in Table 3. The final target whiteness (ISO 2470-1:2016) was 86%.

[0049] [Table 3]

[0050] (5) Beating work The pulp obtained in (4) was beaten using a PFI mill. The beating intensity was controlled by the mill rotation speed.

[0051] (6) Making handmade paper From the beaten pulp obtained in (5), handmade paper was produced in accordance with JIS P 8222 "Pulp - Method for preparing test handmade paper - Method using a standard handmade paper machine". Target basis weight: 60 g / m² 2 That's what I decided.

[0052] (7) Paper quality test (6) For the handmade paper obtained by (6), the tear length (density 0.6 g / cm 3 The strength (0.6 g / cm²) was measured in accordance with JIS P 8113:2006. 3 The measurement was performed in accordance with ISO2493-2:2020. Furthermore, for Comparative Examples 1-3, the tear length and bending stiffness of handmade paper obtained by (1)-(6) were measured in the same manner as in the Examples, using wood from E. urophylla (6.5 years old), E. globulus (10 years old), and E. urograndis (7 years old), respectively. The bulk density and fiber length of each wood pulp for Comparative Examples 1-3 were as follows: Bulk density of Comparative Example 1: 530 kg / m 3 Fiber length: 0.86 mm; Volumetric density of Comparative Example 2: 516 kg / m 3Fiber length: 0.83 mm; Volumetric weight of Comparative Example 3: 550 kg / m 3 Fiber length: 0.80 mm. Comparative Examples 4-9 are based on the measured tear lengths of paper obtained from the following wood pulps, as described in H. Nanko et al., "THE WORLD OF MARKET PULP" (2010), TAPPI Press: E. grandis hybrid wood pulp (fiber length: 0.76 mm: Comparative Example 4); E. grandis and E. globulus hybrid wood pulp (fiber length: 0.72 mm: Comparative Example 5); E. globulus (fiber length: 0.75 mm: Comparative Example 6); E. caldumalesis wood pulp (fiber length: 0.65 mm: Comparative Example 7) (Table 4, Figure 1, Figure 2).

[0053] [Table 4]

[0054] The paper obtained in the examples has densities of 0.5 and 0.6 g / cm³. 3 In both cases, the tear length satisfied Equation 1. Furthermore, the bending stiffness also satisfied Equation 2. On the other hand, the comparative paper had densities of 0.5 and 0.6 g / cm³. 3 In all cases, the fracture length did not satisfy Equation 1, and the bending stiffness also did not satisfy Equation 2 (Table 4, Figure 1, Figure 2).

[0055] The above results demonstrate that, in the present invention, paper possessing both bulkiness and high strength can be obtained from kraft pulp.

Claims

1. Paper whose paper raw material includes hardwood kraft pulp that satisfies the following conditions (1), (2), (3), and (4). (1) The hardwood kraft pulp is derived from wood raw materials from plants of the genus Eucalyptus. (2) The volumetric density of the wood raw material of the hardwood kraft pulp is 635 kg / m³ 3 It must be the above. (3) The fiber length of the wood raw material of the hardwood kraft pulp is 0.65 mm or more and 1.1 mm or less. (4) The density and tear length of the handmade paper produced from the hardwood kraft pulp in accordance with JIS P 8122 are in the relationship given by Equation 1. (Formula 1) B ≥ 26.537 × A - 8.153 (In Equation 1, A is density (g / cm³) 3 ) represents the fracture length (km), where 0.3 ≤ A ≤ 0.

7.

2. The paper according to claim 1, wherein the hardwood kraft pulp further satisfies the following condition (5). (5) The density and bending stiffness of handmade paper made from the hardwood kraft pulp in accordance with JIS P 8122 are in relation to Equation 2. (Formula 2) C ≥ -387.35 × A + 510.75 (In equation 2, A is density (g / cm³) 3 This represents the flexural stiffness (μN·m), where 0.3 ≤ A ≤ 0.

7. C is the bending stiffness (μN·m). 2 (represents / m)

3. The paper according to claim 1 or 2, wherein the eucalyptus plants include E. pellita, E. brassiana, E. urophylla, E. urograndis, a hybrid of E. brassiana and E. pellita, a hybrid of E. urophylla and E. pellita, and a hybrid of two or more tree species selected from these.

4. The paper according to any one of claims 1 to 3, which is printing paper, inkjet paper, PPC paper, form paper, kraft paper, fine paper, coated paper, lightly coated paper, or packaging paper.

5. A method for producing paper according to claim 1 or 2, wherein hardwood kraft pulp satisfying the following conditions (1), (2), (3), and (4) is used as a paper raw material. (1) The hardwood kraft pulp is derived from wood raw materials from plants of the genus Eucalyptus. (2) The volumetric density of the wood raw material of the hardwood kraft pulp is 635 kg / m³ 3 It must be the above. (3) The fiber length of the wood raw material of the hardwood kraft pulp is 0.65 mm or more and 1.1 mm or less. (4) The density and tear length of the handmade paper produced from the hardwood kraft pulp in accordance with JIS P 8122 are in the relationship given by Equation 1. (Formula 1) B ≥ 26.537 × A - 8.153 (In Equation 1, A is density (g / cm³) 3 ) represents the fracture length (km), where 0.3 ≤ A ≤ 0.

7.

6. A method for producing paper according to claim 5, comprising: pulping the wood raw material to obtain the kraft pulp; and producing paper using the pulp containing the kraft pulp as a raw material.

7. The method for producing paper according to claim 6, wherein the kraft pulp digestion is carried out under conditions of an activated alkali addition rate of 5 to 40%.

8. A method for producing paper according to claim 6 or 7, comprising performing at least one of the following treatments after pulping kraft pulp: delignin treatment, bleaching treatment, and beating treatment.

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