WO2020241435A1 - Kraft paper and kraft paper sack - Google Patents

Kraft paper and kraft paper sack Download PDF

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Publication number
WO2020241435A1
WO2020241435A1 PCT/JP2020/020052 JP2020020052W WO2020241435A1 WO 2020241435 A1 WO2020241435 A1 WO 2020241435A1 JP 2020020052 W JP2020020052 W JP 2020020052W WO 2020241435 A1 WO2020241435 A1 WO 2020241435A1
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Prior art keywords
kraft paper
pulp
jis
kraft
measured
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PCT/JP2020/020052
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French (fr)
Japanese (ja)
Inventor
佐和子 赤井
智裕 遠藤
陵 清水
実沙 江原
由貴 田村
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王子ホールディングス株式会社
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Application filed by 王子ホールディングス株式会社 filed Critical 王子ホールディングス株式会社
Priority to KR1020217039769A priority Critical patent/KR20220004197A/en
Priority to JP2021522282A priority patent/JP7552592B2/en
Publication of WO2020241435A1 publication Critical patent/WO2020241435A1/en

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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/02—Chemical or chemomechanical or chemothermomechanical pulp
    • D21H11/04—Kraft or sulfate pulp

Definitions

  • the present invention relates to kraft paper and kraft paper bags.
  • the present invention relates to kraft paper and kraft paper bags suitable for heavy packaging used for filling and transporting powder products.
  • Kraft paper obtained from kraft pulp is used for various purposes such as bag making and wrapping paper.
  • Kraft paper, especially kraft paper bags for heavy packaging for transporting heavy objects, is required to have high strength so as not to cause bag breakage in processes such as filling, transporting, and storing the contents.
  • Patent Document 1 proposes kraft paper that has both strength and breathability by using pulp having a long fiber length.
  • kraft paper obtained from kraft pulp is a strong, durable and hard-to-tear paper, so it can be used for various purposes such as heavy wrapping paper bags used for transporting heavy objects, corrugated cardboard materials, envelopes, and adhesive tapes. It may also be used (Patent Document 2).
  • kraft paper bags are sometimes used for transporting heavy objects, they need to be strong and durable.
  • the kraft paper bag needs to have a certain degree of air permeability.
  • the speed of airflow filling has been increasing, so that kraft paper bags are required to have further improved air permeability. Therefore, in view of the above circumstances, it is an object of the present invention to provide kraft paper having higher breathability while maintaining strength and a kraft paper bag using the same.
  • the present invention has adopted the following configuration.
  • Kraft paper containing kraft pulp as the main component The Canadian standard free water content measured in accordance with JIS P 811-2: 2012 of the disintegrated pulp obtained by disintegrating the kraft paper by the pulp disintegration method described in JIS P 8220: 2012 is 700 mL or more, and JIS Kraft paper having a fiber roughness of 0.200 mg / m or more as measured in accordance with P 8120: 1998.
  • JIS P 8116 ratio tear strength in the longitudinal direction as measured according to 2000 is at 15.0mN ⁇ m 2 / g or more, lateral specific tear strength 18.0mN ⁇ m 2 / The kraft paper according to [1], which is g or more.
  • the longitudinal tensile elongation at break measured in accordance with JIS P 8113: 2006 is 8.0% or more, and the lateral tensile elongation at break is 6.0% or more, [1] or [ 2] The kraft paper described in.
  • the present invention may have the following configuration.
  • Kraft paper containing kraft pulp as the main component The basis weight measured in accordance with JIS P 8124: 2011 is 70 g / m 2 or more. Measured according to JIS P 8140: 1998, the Cobb water absorption at a temperature of 23 ° C. and a contact time of 60 seconds is 15 to 28 g / m 2 . Kraft paper with a ratio of Cobb water absorption to basis weight of 0.18 to 0.35.
  • JIS P 8116 ratio tear strength in the longitudinal direction as measured according to 2000 is at 15.0mN ⁇ m 2 / g or more, the ratio of the transverse tear strength of 18.0mN ⁇ m 2 / The kraft paper according to [11], which is g or more.
  • the longitudinal tensile elongation at break measured in accordance with JIS P 8113: 2006 is 8.0% or more, and the lateral tensile elongation at break is 6.0% or more, [11] or [ 12] The kraft paper described in.
  • the specific tensile energy absorption amount in the vertical direction measured in accordance with JIS P 8113: 2006 is 2.5 J / g or more, and the specific tensile energy absorption amount in the horizontal direction is 2.3 J / g or more.
  • the kraft paper according to any one of [11] to [14], wherein the air permeation resistance measured in accordance with JIS P 8117: 2009 is 10 seconds or less.
  • the Canadian standard freeness measured in accordance with JIS P 811-2: 2012 of the obtained disintegrated pulp is 700 mL or more.
  • One embodiment of the present invention is kraft paper containing kraft pulp as a main component, and JIS P 811-2 of the disintegrated pulp obtained by disintegrating the kraft paper by the pulp disintegration method described in JIS P 8220: 2012. : Kraft paper having a Canadian standard freeness of 700 mL or more measured in accordance with 2012 and a fiber roughness of 0.200 mg / m or more measured in accordance with JIS P 8120: 1998.
  • the kraft paper according to this embodiment has excellent breathability while maintaining strength. Further, according to the kraft paper bag according to the present embodiment, it is possible to efficiently perform air blowing filling.
  • another embodiment of the present invention is kraft paper containing kraft pulp as a main component, and the basis weight measured in accordance with JIS P 8124: 2011 is 70 g / m 2 or more, and JIS P 8140.
  • Cobb water absorption at a temperature of 23 ° C. and a contact time of 60 seconds, measured in accordance with 1998, is 5 to 40 g / m 2 (preferably 10 to 35 g / m 2 , more preferably 15 to 28 g / m 2 ).
  • It is a kraft paper having a ratio of the water absorption of Cobb to the basis weight of 0.10 to 0.45 (preferably 0.15 to 0.40, more preferably 0.18 to 0.35). Even if the kraft paper according to the present embodiment is stored in a stacked state, the glue used during bag making does not easily penetrate to the opposite surface, and the surface stickiness and adhesion between the kraft paper bags do not easily occur.
  • the present invention will be described in detail below.
  • the description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments.
  • the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
  • the kraft paper of the present invention contains kraft pulp as a main component.
  • kraft pulp is pulp obtained by treating wood with an alkaline chemical containing sodium hydroxide and sodium sulfide as main components.
  • the main component in kraft paper means a component that accounts for 50% by mass or more with respect to the total mass of kraft paper. That is, the mass ratio of kraft pulp to the total mass of kraft paper is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more. The mass ratio of kraft pulp to the total mass of kraft paper is preferably 100% by mass or less.
  • the ratio of the mass (solid content) of the kraft pulp to the mass (solid content) of the total pulp constituting the kraft paper is preferably 97% by mass or more, and more preferably 98% by mass or more.
  • the ratio of the mass (solid content) of kraft pulp to the mass (solid content) of all pulp constituting the kraft paper is preferably 100% by mass or less.
  • the dissociated pulp obtained (hereinafter, simply referred to as "dissociated pulp") is measured in accordance with JIS P 811-2: 2012.
  • the Canadian standard freeness (hereinafter sometimes referred to as “freeness”) is 700 mL or more
  • the fiber roughness measured in accordance with JIS P 8120: 1998 (hereinafter, simply referred to as “fiber roughness”). ) Is 0.200 mg / m or more. Since the kraft paper of the present invention has the above-mentioned structure, it has both excellent strength and breathability.
  • the upper limit of the freeness of the dissociated pulp measured in accordance with JIS P 811-2: 2012 is not particularly limited, but is preferably 800 mL or less, more preferably 750 mL or less, and preferably 735 mL or less. More preferred.
  • the freeness of the dissociated pulp can be adjusted by beating or the like.
  • the basis weight measured according to JIS P 8124: 2011 of kraft paper is preferably 70 g / m 2 or more, more preferably 75 g / m 2 or more, and 80 g / m 2 or more. Is even more preferable.
  • the upper limit of the basis weight measured in accordance with JIS P 8124: 2011 of kraft paper is not particularly limited, but is preferably 150 g / m 2 or less.
  • the Cobb water absorption at a temperature of 23 ° C. and a contact time of 60 seconds, measured in accordance with JIS P 8140: 1998 of kraft paper, is preferably 5 to 40 g / m 2 and preferably 10 to 35 seconds. Is more preferable, 15 to 28 g / m 2 is further preferable, and 20 to 25 g / m 2 is particularly preferable.
  • the ratio of the water absorption of the cobb to the basis weight is preferably 0.10 to 0.45, more preferably 0.15 to 0.40, and even more preferably 0.18 to 0.35. , 0.21 to 0.35, more preferably 0.28 to 0.35.
  • the ratio of the Cobb water absorption to the basis weight is the value of the Cobb water absorption / basis weight.
  • Cobb water absorption can be adjusted by adding a sizing agent, for example.
  • the sizing agent include a rosin-based sizing agent, an alkyl ketene dimer-based sizing agent, an alkenyl succinic anhydride-based sizing agent, and a synthetic sizing agent.
  • the amount of the sizing agent added is preferably 0.05 to 1.00% by mass, preferably 0.10 to 0.20% by mass, based on the mass (solid content) of the total pulp constituting the kraft paper. Is more preferable.
  • the fiber roughness of the dissociated pulp obtained is defined in JIS P 8120: 1998 (hereinafter, simply referred to as "fiber roughness". ) Is 0.200 mg / m or more.
  • the upper limit of the fiber roughness is not particularly limited, but is preferably 0.400 mg / m or less, more preferably 0.350 mg / m or less, and further preferably 0.300 mg / m or less. It is particularly preferably 0.250 mg / m or less.
  • Fiber roughness is the absolute dry mass of fiber per unit length. The larger the fiber roughness, the more curled the fiber and the easier it is for elongation to develop.
  • the fiber roughness of the disintegrated pulp can be adjusted by the runkel ratio of the raw material pulp, the copper value (K ⁇ value) of the raw material pulp, the blade used for beating, the temperature at the time of beating, and the like.
  • the Runkel ratio is a value obtained by dividing twice the average fiber wall thickness (average of the cell wall thickness of fibers) by the average diameter of the lumen diameter. The average lumen diameter is determined by subtracting twice the average fiber wall thickness from the average fiber width. That is, the Runkel ratio is a value obtained from the average fiber wall thickness and the average fiber width.
  • the average fiber wall thickness and average fiber width required to obtain the Runkel ratio can be measured by a fiber analyzer (Kajaani FiberLab ver4.0, manufactured by Mezzo Automation).
  • the runkel ratio of the raw material pulp is preferably 1.5 to 2.5, and more preferably 1.7 to 2.3.
  • the Runkel ratio is higher for pulp made from softwood than for pulp made from hardwood. Therefore, the runkel ratio of the raw material pulp can be adjusted by the mixing ratio of the softwood kraft pulp and the hardwood kraft pulp. However, the raw material pulp may be only softwood kraft pulp.
  • coniferous kraft pulp examples include unbleached coniferous kraft pulp (NUKP), bleached coniferous kraft pulp (NBKP), semi-bleached coniferous kraft pulp (NSBKP), and coniferous sulfite pulp. These may be used together. Above all, it is preferable to use softwood unbleached kraft pulp (NUKP) as the raw material pulp in terms of excellent tensile elongation at break and strength.
  • grades of softwood kraft pulp examples include Douglas fir, Japanese red pine, spruce, and radiata pine. Among them, Douglas fir is preferably used because it has a high Runkel ratio. Two or more of these may be used in combination as the raw material pulp.
  • broad-leaved kraft pulp examples include broad-leaved unbleached kraft pulp (LUKP), broad-leaved bleached kraft pulp (LBKP), broad-leaved semi-bleached kraft pulp (LSBKP), and broad-leaved sulfite pulp.
  • LLKP broad-leaved unbleached kraft pulp
  • LLBKP broad-leaved bleached kraft pulp
  • LSBKP broad-leaved semi-bleached kraft pulp
  • broad-leaved sulfite pulp broad-leaved sulfite pulp.
  • the K ⁇ value is an index of the lignin content or bleaching property of pulp measured in accordance with JIS P 8211: 2011.
  • the K ⁇ value is too low, the strength of the single fiber may decrease.
  • the K ⁇ value is too high, the fibers are hard, so that curling is difficult and elongation may be difficult to develop. Therefore, considering the balance as a whole, the K ⁇ value of the raw material pulp is preferably 35 to 55, and more preferably 38 to 50.
  • a deluxe finer (basalt) is preferable as the blade used for beating.
  • the deluxe finer has a wider blade width for both the rotor and the stator, so the beating is closer to kneading and loosening than cutting, and it is easy to curl and stretch. That is, the fiber roughness of the disintegrated pulp can be increased.
  • the tear strength of kraft paper is unlikely to decrease.
  • the temperature at the time of beating is preferably 30 to 90 ° C, more preferably 70 to 90 ° C.
  • the higher the temperature the easier it is for curling and the more likely it is to develop elongation. That is, the fiber roughness of the disintegrated pulp can be increased.
  • the softening point of lignin is 70 ° C. or higher, when the lignin is beaten at 70 ° C. or higher, the fibers become soft and curl (roughness) is particularly likely to occur.
  • the specific tear strength in the vertical direction measured in accordance with JIS P 8116: 2000 of kraft paper is not particularly limited, but is preferably 15.0 mN ⁇ m 2 / g or more from the viewpoint of drop impact resistance. , 16.0 mN ⁇ m 2 / g or more, more preferably 17.0 mN ⁇ m 2 / g or more, further preferably 17.5 mN ⁇ m 2 / g or more, 18 It is particularly preferable that the content is 0.0 mN ⁇ m 2 / g or more.
  • the upper limit of the relative tear strength in the longitudinal direction is not particularly limited, but is preferably 25.0 mN ⁇ m 2 / g or less.
  • the lateral specific tear strength measured in accordance with JIS P 8116: 2000 of kraft paper is not particularly limited, but is preferably 18.0 mN ⁇ m 2 / g or more, and 20.0 mN ⁇ . more preferably m 2 / g or more, still more preferably 22.0MN ⁇ m 2 / g or more, particularly preferably 23.0MN ⁇ m 2 / g or more.
  • the ratio tear strength in the transverse direction is not particularly limited, from the viewpoint of the drop impact resistance is preferably at most 28.0mN ⁇ m 2 / g, more not more than 26.0mN ⁇ m 2 / g preferably, more preferably at most 25.0mN ⁇ m 2 / g, particularly preferably not more than 24.0mN ⁇ m 2 / g.
  • the relative tear strength in the vertical direction and the horizontal direction is equal to or higher than the above lower limit value, a kraft paper bag that is unlikely to break in the steps of filling, transporting, and storing the contents can be obtained.
  • the relative tear strength in the longitudinal direction and the lateral direction tends to be higher as the freeness of the disintegrated pulp is larger.
  • the horizontal direction means the width direction of the paper machine
  • the vertical direction means the flow direction of the paper machine.
  • the tensile elongation at break in the vertical direction measured in accordance with JIS P 8113: 2006 of kraft paper is preferably 6.0% or more from the viewpoint of drop impact resistance and / or suppression of glue penetration. It is more preferably 0% or more, further preferably 7.5% or more, further preferably 8.0% or more, and particularly preferably 8.5% or more.
  • the tensile elongation at break in the longitudinal direction is not particularly limited, but is preferably 12.0% or less, and more preferably 10.0% or less.
  • the tensile elongation at break in the lateral direction measured in accordance with JIS P 8113: 2006 of kraft paper is not particularly limited, but is preferably 4.0% or more, and preferably 5.0% or more.
  • the tensile elongation at break in the lateral direction is not particularly limited, but is preferably 10.0% or less, more preferably 9.0% or less, and further preferably 8.0% or less.
  • the tensile elongation at break in the vertical direction and the horizontal direction is at least the above lower limit value, a kraft paper bag that is unlikely to break in the steps of filling, transporting, and storing the contents can be obtained.
  • the tensile elongation at break in the longitudinal direction and the transverse direction tends to be higher as the fiber roughness of the dissociated pulp is larger.
  • the amount of specific tensile energy absorbed in the vertical direction specified in JIS P 8113: 2006 of kraft paper is preferably 2.5 J / g or more, more preferably 2.8 J / g or more, and 3.0 J. It is more preferably / g or more.
  • the lateral specific tensile energy absorption amount specified in JIS P 8113: 2006 of kraft paper is preferably 1.5 J / g or more from the viewpoint of drop impact resistance and / or suppression of glue penetration. It is more preferably 2.0 J / g or more, further preferably 2.3 J / g or more, further preferably 2.5 J / g or more, and particularly preferably 2.8 J / g or more. preferable.
  • the specific tensile energy absorption amount in the vertical direction and the horizontal direction is equal to or higher than the above lower limit value, a kraft paper bag that is less likely to break in the process of filling, transporting, storing, etc. of the contents can be obtained.
  • the amount of specific tensile energy absorbed in the longitudinal direction and the lateral direction tends to be higher as the fiber roughness of the disintegrated pulp is larger.
  • the air permeability resistance measured in accordance with JIS P 8117: 2009 of kraft paper is preferably 50 seconds or less, more preferably 30 seconds or less, further preferably 20 seconds or less. It is more preferably 10 seconds or less, and particularly preferably 7 seconds or less. Further, the air permeation resistance measured in accordance with JIS P 8117: 2009 of kraft paper is preferably 0 seconds or more. When the air permeation resistance is not more than the above upper limit value, kraft paper having excellent breathability can be obtained. The air permeation resistance tends to be lower as the freeness of the dissociated pulp increases.
  • Kraft paper may contain arbitrary components in addition to kraft pulp.
  • Optional components include sizing agents, anionic, cationic or amphoteric yield improvers, drainage improvers, dry paper strength enhancers, wet paper strength enhancers, internal chemicals such as fillers, water resistant agents, and dyes. , Fluorescent whitening agent and the like.
  • the sizing agent examples include internal sizing agents such as rosin and alkyl ketene dimer (AKD); surface sizing agents such as styrene / acrylic acid copolymer and styrene / methacrylic acid copolymer.
  • the blending amount of the sizing agent is not particularly limited, but is preferably 1.0 part by mass or less, more preferably 0.50 part by mass or less, and further preferably 0.% by mass with respect to 100 parts by mass (solid content equivalent) of the raw material pulp. It is 30 parts by mass or less, more preferably 0.20 parts by mass or less.
  • the blending amount of the sizing agent is preferably 0 parts by mass or more with respect to 100 parts by mass of the raw material pulp.
  • the yield improving agent examples include polyacrylamide and sulfuric acid band.
  • the amount of the yield improving agent to be blended is not particularly limited, but is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and further, with respect to 100 parts by mass (solid content equivalent) of the raw material pulp. It is preferably 2.5 parts by mass or less. Further, the blending amount of the yield improving agent is preferably 0 parts by mass or more with respect to 100 parts by mass of the raw material pulp.
  • dry paper strength enhancer examples include cationized starch, polyacrylamide, carboxymethyl cellulose and the like.
  • the amount of the dry paper strength enhancer to be blended is not particularly limited, but is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, based on 100 parts by mass (solid content equivalent) of the raw material pulp.
  • the blending amount of the dry paper strength enhancer is preferably 0 parts by mass or more with respect to 100 parts by mass of the raw material pulp.
  • wet paper strength enhancer examples include polyamide polyamine epichlorohydrin (PAE), urea formaldehyde resin, melamine formaldehyde resin, and the like, and the wet paper strength enhancer is preferably PAE.
  • the blending amount of the wet paper strength enhancer in the paper base material is not particularly limited, but is preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass with respect to 100 parts by mass (solid content equivalent) of the raw material pulp. It is more than a department.
  • the amount of the wet paper strength enhancer blended is preferably 1.0 part by mass or less, and more preferably 0.7 part by mass or less with respect to 100 parts by mass of the raw material pulp.
  • Fillers include clay, talc, kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite, smectite, etc.
  • Inorganic fillers organic fillers such as acrylic resins and vinylidene chloride resins can be mentioned.
  • the kraft paper may have a coating layer.
  • the coating layer is preferably a coating layer containing a natural adhesive such as starch or a synthetic adhesive such as polyvinyl alcohol, polyacrylamide, styrene-butadiene copolymer resin, and acrylic resin as a main component.
  • the coating amount of the coating layer is preferably 0.3 to 3.0 g / m 2 .
  • the method for producing kraft paper of the present invention includes a step of using wood chips as a main raw material and steaming it by a kraft method to obtain unbleached kraft pulp, a step of beating the unbleached kraft pulp to obtain pulp slurry, and pulp. It is preferable to include a step of making a pulp of the slurry. In addition, pulp other than unbleached kraft pulp may be added to this pulp slurry. Further, the above-mentioned internal chemicals may be added to the pulp slurry as long as the effects of the present invention are not impaired.
  • the sizing agent it is preferable to add the above-mentioned sizing agent.
  • the amount of the sizing agent added is preferably 0.05 to 1.00% by mass, preferably 0.10 to 0.20% by mass, based on the mass (solid content) of the total pulp contained in the slurry. Is more preferable.
  • a dry paper strength enhancer to the pulp slurry after beating.
  • the amount of the dry paper strength enhancer added is preferably 0.5 to 3.0% by mass with respect to the mass (solid content) of the total pulp contained in the slurry.
  • the freeness of the disintegrated pulp in order to set the freeness of the disintegrated pulp to 700 to 750 mL, it is preferable to perform beating until the finished freeness is 670 to 750 mL. Further, for example, in order to make the fiber roughness of the disintegrated pulp 0.200 mg / m or more, it is preferable to perform beating until the finished fiber roughness becomes 0.160 to 0.250 mg / m.
  • the temperature at the time of beating is preferably 30 to 90 ° C, more preferably 70 to 90 ° C.
  • the higher the temperature the easier it is for curling and the more likely it is to develop elongation. That is, the fiber roughness of the disintegrated pulp can be increased.
  • the softening point of lignin is 70 ° C. or higher, when the lignin is beaten at 70 ° C. or higher, the fibers become soft and curl (roughness) is particularly likely to occur.
  • kraft paper paper making method and the paper machine type. It is possible. In addition, special processing such as crepe processing can be performed if necessary.
  • the kraft paper bag of the present invention is a bag made from the above-mentioned kraft paper.
  • the shape of the bag is not particularly limited. Examples include a glue bag such as a bottom bag with a foldless valve.
  • Glue may be used when making kraft paper bags.
  • the glue used during bag making include vinyl acetate copolymers, ethylene-vinyl acetate copolymers, acrylic copolymers, hot melt resins, and carboxymethyl cellulose.
  • Water is preferable as the solvent for the glue used during bag making.
  • the dry coating amount of the glue used at the time of bag making is preferably 15 to 23 g / m 2 .
  • the dry coating amount is equal to or more than the above lower limit value, it can be firmly adhered with glue, so that bag making is easy. Further, if the dry coating amount is not more than the above upper limit value, the glue does not easily seep out even if the kraft paper bags are stacked after the bag is made.
  • the kraft paper bag of the present invention is preferably a multi-layer paper bag having two or more layers in order to further increase the strength.
  • the kraft paper bag is a multi-layer paper bag, for example, it may have a structure in which a synthetic resin layer is laminated on the above-mentioned kraft paper, or a three-layer structure of kraft paper / synthetic resin layer / kraft paper. Further, when the kraft paper bag is a multi-layer paper bag, an adhesive layer may be provided between each layer.
  • the kraft paper bag of the present invention is a tough paper bag, it can be used as a heavy wrapping paper bag that can withstand the weight and handling of the contents by wrapping the contents in weight units.
  • the contents of the kraft paper bag of the present invention are not particularly limited, but powder or granular materials are preferable as the contents because they are excellent in air permeability and suitable for air-filling. That is, the kraft paper bag of the present invention is preferably for containing powder.
  • K ⁇ value The K ⁇ value of the dissociated pulp was measured by the method specified in JIS P 8211: 2011.
  • the kraft paper produced in the following Examples and Comparative Examples was disintegrated by the pulp dissociation method described in JIS P 8220: 2012 to obtain dissociated pulp.
  • JIS P 8120: 1998 accurately separate 25 mL (equivalent to 5 mg of absolute dry pulp) from a slurry obtained by diluting dissociated pulp with water to 0.02% by mass, and use Kajaani FiberLab ver4.0 manufactured by Metso Automation Co., Ltd. The fiber roughness of the disintegrated pulp was measured.
  • the basis weight of kraft paper was measured according to the method specified in JIS P 8124: 2011. Subsequently, the thickness of the kraft paper was measured by the method specified in JIS P 8118: 2014. The value obtained by dividing the basis weight by the paper thickness was taken as the density of kraft paper.
  • a tear tester Elemendorff tear tester (SA-W type) manufactured by Toyo Seiki Co., Ltd.) according to the method specified in JIS P 8116: 2000, the kraft paper is used in the vertical direction (MD direction) and the horizontal direction (MD direction). The tear strength in the CD direction) was measured. The specific tear strength of the kraft paper in the vertical direction (MD direction) and the horizontal direction (CD direction) was determined by dividing each tear strength by the basis weight.
  • TEAI Specific tensile energy absorption
  • Air permeability resistance The air permeability resistance of kraft paper was measured by a method specified in JIS P 8117: 2009 with an Oken type testing machine (manufactured by Asahi Seiko Co., Ltd., digital type Oken type air permeability / smoothness testing machine).
  • Kraft paper was processed into a bottom bladder bag with a foldless valve specified in JIS Z 1505: 2004 having a height of 370 mm, a depth of 95 mm and a width of 320 mm, and 25 kg of cement was filled by air blowing. Based on JIS Z 0217: 1998, the cement-filled bag was dropped horizontally from a height of 1.2 m, and the number of times until the bag was broken was counted and evaluated according to the following criteria. ⁇ : The number of times until the bag is broken is 10 times or more. ⁇ : The number of times until the bag is broken is 8 times or more and 9 times or less. X: The number of times until the bag is broken is 7 times or less.
  • Adhesiveness A (adhesiveness) Cut the kraft paper of each example into a width of 30 mm and a length of 150 mm, and thinly stretch 0.3 mL of water-soluble glue (Lifebond P-8100 manufactured by Niei Kako Co., Ltd., concentration 48% by mass) to a width of 7 mm and a length of 10 cm. It was applied to the part of, and other kraft papers of the same example were layered and glued. Three sets of these were stacked, a weight of 5 kg was placed on the top, and the mixture was left for a day, and then the adhesive portion was tried to be peeled off and evaluated. ⁇ : The glued parts of the kraft paper are completely adhered to each other. ⁇ : Mostly adhered, but some parts are not adhered. X: Almost no adhesion and easy peeling.
  • Glue suitability B (glue permeability) Cut the kraft paper of each example into 50 mm squares, and apply 1.5 mL of water-soluble glue (Lifebond P-8100 manufactured by Niei Kako Co., Ltd., concentration 48% by mass) to the central part of the kraft paper with an area of 3 cm 2. Then, other kraft papers of the same example were layered and glued. Three sets of these were stacked, a weight of 5 kg was placed on the top, and the mixture was left for 6 hours, and then the penetration of the glue was evaluated. ⁇ : The glue has not penetrated to the opposite surface of the glued part. ⁇ : The glue has penetrated slightly to the opposite surface of the glued portion, but no stickiness is observed on the opposite surface. X: The glue has penetrated into the opposite surface of the glued part and is adhered to other paper.
  • Kraft pulp (1) Unbleached coniferous kraft pulp (NUKP) made from Douglas fir.
  • Kraft pulp (2) Unbleached coniferous kraft pulp (NUKP) made from domestic pine.
  • Kraft pulp (3) Unbleached coniferous kraft pulp (NUKP) made from domestic cedar.
  • a synthetic sizing agent (Size Pine MXE2, manufactured by Arakawa Chemical Industries, Ltd.) was added to the pulps having the formulations shown in Tables 1 and 2 as an internal chemical in an amount of 0.15% by mass based on the solid content of the pulp. Then, it was beaten at 80 ° C. using a deluxe finer. The characteristics of the pulp after beating are shown in Tables 1 and 2.
  • a sulfuric acid band was added to 1.2% by mass based on the solid content of the pulp, and cationized starch was added to the pulp after beating as an internal preparation in an amount of 0.9% by mass based on the solid content of the pulp.
  • the evaluation results of the kraft paper of each example are shown in Tables 1 and 2. As shown in Tables 1 and 2, the kraft papers of Examples had low air permeation resistance and excellent air permeability. Further, the bag obtained from the kraft paper of the example had good filling property, bag breaking suitability, and drop impact characteristics, and had excellent strength. Further, the kraft paper of the example had good adhesiveness (excellent adhesiveness, and penetration of glue into other kraft papers under load was suppressed).

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Abstract

Provided is kraft paper and a kraft paper sack that have excellent permeability while maintaining strength. When the kraft paper is disintegrated by a pulp-disintegration method specified in JIS P 8220:2012, the disintegrated pulp thus acquired has a Canadian standard freeness, which is measured in accordance with JIS P 8121-2:2012, of 700 mL or more, and a fiber roughness, which is specified in JIS P 8120:1998, of 0.200 mg/m or more.

Description

クラフト紙及びクラフト紙袋Kraft paper and kraft paper bags
　本発明はクラフト紙及びクラフト紙袋に関する。特に、粉体製品を充填して運搬するために用いられる重包装用に適したクラフト紙及びクラフト紙袋に関する。 The present invention relates to kraft paper and kraft paper bags. In particular, the present invention relates to kraft paper and kraft paper bags suitable for heavy packaging used for filling and transporting powder products.
　クラフトパルプを原料として得られるクラフト紙は、製袋や包装紙等の様々な用途に用いられている。クラフト紙、特に、重量物の運搬用である重包装用のクラフト紙袋には、内容物の充填、輸送、保管等の工程において破袋を生じさせないために、高い強度が要求される。 Kraft paper obtained from kraft pulp is used for various purposes such as bag making and wrapping paper. Kraft paper, especially kraft paper bags for heavy packaging for transporting heavy objects, is required to have high strength so as not to cause bag breakage in processes such as filling, transporting, and storing the contents.
　クラフト紙袋を利用する産業の中でも、製粉業、化学品製造業などでは、クラフト紙袋に微細な粒子状の粉体が風送充填される。風送充填を効率的に行うためには、高い通気性を有するクラフト紙が求められる。しかし、クラフト紙の強度を考慮すると、叩解を進めてパルプ繊維同士の結合点を増やす必要があるが、叩解を進めるとクラフト紙の通気性は悪くなる傾向がある。そこで、特許文献１では、繊維長が長いパルプを使用することにより、強度と通気性を両立させたクラフト紙が提案されている。 Among the industries that use kraft paper bags, in the flour milling industry, chemical manufacturing industry, etc., kraft paper bags are filled with fine particulate powder by air. Kraft paper with high air permeability is required for efficient air filling. However, considering the strength of kraft paper, it is necessary to proceed with beating to increase the bonding points between pulp fibers, but as beating is advanced, the air permeability of kraft paper tends to deteriorate. Therefore, Patent Document 1 proposes kraft paper that has both strength and breathability by using pulp having a long fiber length.
　また、クラフトパルプを原料として得られるクラフト紙は、強度が高く丈夫で破れにくい紙であるため、重量物の運搬に使用する重包装紙袋や段ボールの材料、封筒、粘着テープ等の様々な用途に用いられる場合もある（特許文献２）。 In addition, kraft paper obtained from kraft pulp is a strong, durable and hard-to-tear paper, so it can be used for various purposes such as heavy wrapping paper bags used for transporting heavy objects, corrugated cardboard materials, envelopes, and adhesive tapes. It may also be used (Patent Document 2).
特許第６２２２９４６号公報Japanese Patent No. 6222946 特許第６１９８３７６号公報Japanese Patent No. 6198376
　クラフト紙袋は重量物の運搬に用いられる場合もあるため、強度が高く丈夫である必要がある。一方で、粉体を充填する場合においては、クラフト紙袋はある程度の通気性を有することが必要である。近年は、風送充填の高速化が進んでいるため、クラフト紙袋には、さらなる通気性の向上が求められている。
　そこで、本発明は、上記事情に鑑みて、強度を維持しつつ、さらに通気性を高めたクラフト紙とこれを用いたクラフト紙袋を提供することを課題とする。 Since kraft paper bags are sometimes used for transporting heavy objects, they need to be strong and durable. On the other hand, when filling powder, the kraft paper bag needs to have a certain degree of air permeability. In recent years, the speed of airflow filling has been increasing, so that kraft paper bags are required to have further improved air permeability.
Therefore, in view of the above circumstances, it is an object of the present invention to provide kraft paper having higher breathability while maintaining strength and a kraft paper bag using the same.
　上記の課題を達成するために、本発明は以下の構成を採用した。
［１］クラフトパルプを主成分とするクラフト紙であって、
　該クラフト紙をＪＩＳ　Ｐ　８２２０：２０１２に記載のパルプ離解法により離解して得られる離解パルプのＪＩＳ　Ｐ　８１２１－２：２０１２に準拠して測定されるカナダ標準ろ水度は７００ｍＬ以上であり、ＪＩＳ　Ｐ　８１２０：１９９８に準拠して測定される繊維粗度は０．２００ｍｇ／ｍ以上である、クラフト紙。
［２］ＪＩＳ　Ｐ　８１１６：２０００に準拠して測定される縦方向の比引裂強さが１５．０ｍＮ・ｍ２／ｇ以上であり、横方向の比引裂強さが１８．０ｍＮ・ｍ２／ｇ以上である、［１］に記載のクラフト紙。
［３］ＪＩＳ　Ｐ　８１１３：２００６に準拠して測定される縦方向の引張破断伸びが８．０％以上であり、横方向の引張破断伸びが６．０％以上である、［１］又は［２］に記載のクラフト紙。
［４］ＪＩＳ　Ｐ　８１１３：２００６に準拠して測定される縦方向の比引張エネルギー吸収量が２．５Ｊ／ｇ以上であり、横方向の比引張エネルギー吸収量が２．３Ｊ／ｇ以上である、［１］～［３］のいずれかに記載のクラフト紙。
［５］ＪＩＳ　Ｐ　８１１７：２００９に準拠して測定される透気抵抗度が１０秒以下である、［１］～［４］のいずれかに記載のクラフト紙。
［６］ＪＩＳ　Ｐ　８１４０：１９９８に準拠して測定される、温度２３℃、接触時間６０秒でのコッブ吸水度が１５～２８ｇ／ｍ２である、［１］～［５］のいずれかに記載のクラフト紙。
［７］［１］～［６］のいずれかに記載のクラフト紙で構成されたクラフト紙袋。
［８］粉体収容用である［７］に記載のクラフト紙袋。 In order to achieve the above problems, the present invention has adopted the following configuration.
[1] Kraft paper containing kraft pulp as the main component.
The Canadian standard free water content measured in accordance with JIS P 811-2: 2012 of the disintegrated pulp obtained by disintegrating the kraft paper by the pulp disintegration method described in JIS P 8220: 2012 is 700 mL or more, and JIS Kraft paper having a fiber roughness of 0.200 mg / m or more as measured in accordance with P 8120: 1998.
[2] JIS P 8116: ratio tear strength in the longitudinal direction as measured according to 2000 is at 15.0mN · m 2 / g or more, lateral specific tear strength 18.0mN · m 2 / The kraft paper according to [1], which is g or more.
[3] The longitudinal tensile elongation at break measured in accordance with JIS P 8113: 2006 is 8.0% or more, and the lateral tensile elongation at break is 6.0% or more, [1] or [ 2] The kraft paper described in.
[4] The specific tensile energy absorption amount in the vertical direction measured in accordance with JIS P 8113: 2006 is 2.5 J / g or more, and the specific tensile energy absorption amount in the horizontal direction is 2.3 J / g or more. , The kraft paper according to any one of [1] to [3].
[5] The kraft paper according to any one of [1] to [4], wherein the air permeation resistance measured in accordance with JIS P 8117: 2009 is 10 seconds or less.
[6] Any of [1] to [5], which is measured in accordance with JIS P 8140: 1998 and has a Cobb water absorption of 15 to 28 g / m 2 at a temperature of 23 ° C. and a contact time of 60 seconds. Described kraft paper.
[7] A kraft paper bag made of the kraft paper according to any one of [1] to [6].
[8] The kraft paper bag according to [7] for storing powder.
　また、本発明は以下の構成であってもよい。
［１１］クラフトパルプを主成分とするクラフト紙であって、
　ＪＩＳ　Ｐ　８１２４：２０１１に準拠して測定される坪量が７０ｇ／ｍ２以上であり、
　ＪＩＳ　Ｐ　８１４０：１９９８に準拠して測定される、温度２３℃、接触時間６０秒でのコッブ吸水度が１５～２８ｇ／ｍ２であり、
　坪量に対するコッブ吸水度の比が０．１８～０．３５である、クラフト紙。
［１２］ＪＩＳ　Ｐ　８１１６：２０００に準拠して測定される縦方向の比引裂強さが１５．０ｍＮ・ｍ２／ｇ以上であり、横方向の比引裂強さが１８．０ｍＮ・ｍ２／ｇ以上である、［１１］に記載のクラフト紙。
［１３］ＪＩＳ　Ｐ　８１１３：２００６に準拠して測定される縦方向の引張破断伸びが８．０％以上であり、横方向の引張破断伸びが６．０％以上である、［１１］又は［１２］に記載のクラフト紙。
［１４］ＪＩＳ　Ｐ　８１１３：２００６に準拠して測定される縦方向の比引張エネルギー吸収量が２．５Ｊ／ｇ以上であり、横方向の比引張エネルギー吸収量が２．３Ｊ／ｇ以上である、［１１］～［１３］のいずれかに記載のクラフト紙。
［１５］ＪＩＳ　Ｐ　８１１７：２００９に準拠して測定される透気抵抗度が１０秒以下である、［１１］～［１４］のいずれかに記載のクラフト紙。
［１６］クラフト紙をＪＩＳ　Ｐ　８２２０：２０１２に記載のパルプ離解法により離解した場合、得られる離解パルプのＪＩＳ　Ｐ　８１２１－２：２０１２に準拠して測定されるカナダ標準ろ水度は７００ｍＬ以上であり、ＪＩＳ　Ｐ　８１２０：１９９８に準拠して測定される繊維粗度は０．２００ｍｇ／ｍ以上である、［１１］～［１５］のいずれかに記載のクラフト紙。
［１７］［１１］～［１６］のいずれかに記載のクラフト紙で構成されたクラフト紙袋。 In addition, the present invention may have the following configuration.
[11] Kraft paper containing kraft pulp as the main component.
The basis weight measured in accordance with JIS P 8124: 2011 is 70 g / m 2 or more.
Measured according to JIS P 8140: 1998, the Cobb water absorption at a temperature of 23 ° C. and a contact time of 60 seconds is 15 to 28 g / m 2 .
Kraft paper with a ratio of Cobb water absorption to basis weight of 0.18 to 0.35.
[12] JIS P 8116: ratio tear strength in the longitudinal direction as measured according to 2000 is at 15.0mN · m 2 / g or more, the ratio of the transverse tear strength of 18.0mN · m 2 / The kraft paper according to [11], which is g or more.
[13] The longitudinal tensile elongation at break measured in accordance with JIS P 8113: 2006 is 8.0% or more, and the lateral tensile elongation at break is 6.0% or more, [11] or [ 12] The kraft paper described in.
[14] The specific tensile energy absorption amount in the vertical direction measured in accordance with JIS P 8113: 2006 is 2.5 J / g or more, and the specific tensile energy absorption amount in the horizontal direction is 2.3 J / g or more. , [11] to [13].
[15] The kraft paper according to any one of [11] to [14], wherein the air permeation resistance measured in accordance with JIS P 8117: 2009 is 10 seconds or less.
[16] When kraft paper is disintegrated by the pulp disintegration method described in JIS P 8220: 2012, the Canadian standard freeness measured in accordance with JIS P 811-2: 2012 of the obtained disintegrated pulp is 700 mL or more. The kraft paper according to any one of [11] to [15], wherein the fiber roughness measured in accordance with JIS P 8120: 1998 is 0.200 mg / m or more.
[17] A kraft paper bag made of the kraft paper according to any one of [11] to [16].
　本発明の一実施形態は、クラフトパルプを主成分とするクラフト紙であって、該クラフト紙をＪＩＳ　Ｐ　８２２０：２０１２に記載のパルプ離解法により離解して得られる離解パルプのＪＩＳ　Ｐ　８１２１－２：２０１２に準拠して測定されるカナダ標準ろ水度は７００ｍＬ以上であり、ＪＩＳ　Ｐ　８１２０：１９９８に準拠して測定される繊維粗度は０．２００ｍｇ／ｍ以上である、クラフト紙である。本実施形態に係るクラフト紙は、強度を維持しつつ優れた通気性を備える。また、本実施形態に係るクラフト紙袋によれば、風送充填を効率的に行うことも可能となる。 One embodiment of the present invention is kraft paper containing kraft pulp as a main component, and JIS P 811-2 of the disintegrated pulp obtained by disintegrating the kraft paper by the pulp disintegration method described in JIS P 8220: 2012. : Kraft paper having a Canadian standard freeness of 700 mL or more measured in accordance with 2012 and a fiber roughness of 0.200 mg / m or more measured in accordance with JIS P 8120: 1998. The kraft paper according to this embodiment has excellent breathability while maintaining strength. Further, according to the kraft paper bag according to the present embodiment, it is possible to efficiently perform air blowing filling.
　また、本発明の別の実施形態は、クラフトパルプを主成分とするクラフト紙であって、ＪＩＳ　Ｐ　８１２４：２０１１に準拠して測定される坪量が７０ｇ／ｍ２以上であり、ＪＩＳ　Ｐ　８１４０：１９９８に準拠して測定される、温度２３℃、接触時間６０秒でのコッブ吸水度が５～４０ｇ／ｍ２（好ましくは１０～３５ｇ／ｍ２、より好ましくは１５～２８ｇ／ｍ２）であり、坪量に対するコッブ吸水度の比が０．１０～０．４５（好ましくは０．１５～０．４０、より好ましくは０．１８～０．３５）である、クラフト紙である。本実施形態に係るクラフト紙は、積み重ねた状態で保管しても、製袋時に使用された糊が反対面にまで浸透しにくく、表面のべたつきや、クラフト紙袋同士の接着が生じにくい。 Further, another embodiment of the present invention is kraft paper containing kraft pulp as a main component, and the basis weight measured in accordance with JIS P 8124: 2011 is 70 g / m 2 or more, and JIS P 8140. : Cobb water absorption at a temperature of 23 ° C. and a contact time of 60 seconds, measured in accordance with 1998, is 5 to 40 g / m 2 (preferably 10 to 35 g / m 2 , more preferably 15 to 28 g / m 2 ). It is a kraft paper having a ratio of the water absorption of Cobb to the basis weight of 0.10 to 0.45 (preferably 0.15 to 0.40, more preferably 0.18 to 0.35). Even if the kraft paper according to the present embodiment is stored in a stacked state, the glue used during bag making does not easily penetrate to the opposite surface, and the surface stickiness and adhesion between the kraft paper bags do not easily occur.
　以下において、本発明について詳細に説明する。以下に記載する構成要件の説明は、代表的な実施形態や具体例に基づいてなされることがあるが、本発明はそのような実施形態に限定されるものではない。なお、本明細書において「～」を用いて表される数値範囲は「～」前後に記載される数値を下限値及び上限値として含む範囲を意味する。 The present invention will be described in detail below. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
［クラフト紙］
　本発明のクラフト紙は、クラフトパルプを主成分とする。本明細書において、クラフトパルプとは、水酸化ナトリウムと硫化ナトリウムを主成分とするアルカリ性薬剤を用いて木材を処理して得られたパルプである。クラフト紙における主成分とは、クラフト紙の全質量に対して５０質量％以上を占める成分をいう。すなわち、クラフト紙の全質量に対するクラフトパルプの質量割合は、５０質量％以上であることが好ましく、６０質量％以上であることがより好ましく、７０質量％以上であることがさらに好ましい。なお、クラフト紙の全質量に対するクラフトパルプの質量割合１００質量％以下であることが好ましい。また、クラフト紙を構成する全パルプの質量（固形分）に占めるクラフトパルプの質量（固形分）の割合は、９７質量％以上であることが好ましく、９８質量％以上であることがより好ましい。なお、クラフト紙を構成する全パルプの質量（固形分）に占めるクラフトパルプの質量（固形分）の割合は、１００質量％以下であることが好ましい。 [Kraft paper]
The kraft paper of the present invention contains kraft pulp as a main component. In the present specification, kraft pulp is pulp obtained by treating wood with an alkaline chemical containing sodium hydroxide and sodium sulfide as main components. The main component in kraft paper means a component that accounts for 50% by mass or more with respect to the total mass of kraft paper. That is, the mass ratio of kraft pulp to the total mass of kraft paper is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more. The mass ratio of kraft pulp to the total mass of kraft paper is preferably 100% by mass or less. Further, the ratio of the mass (solid content) of the kraft pulp to the mass (solid content) of the total pulp constituting the kraft paper is preferably 97% by mass or more, and more preferably 98% by mass or more. The ratio of the mass (solid content) of kraft pulp to the mass (solid content) of all pulp constituting the kraft paper is preferably 100% by mass or less.
　本発明のクラフト紙をＪＩＳ　Ｐ　８２２０：２０１２に記載のパルプ離解法により離解した場合、得られる離解パルプ（以下、単に「離解パルプ」という。）のＪＩＳ　Ｐ　８１２１－２：２０１２に準拠して測定されるカナダ標準ろ水度（以下「フリーネス」という場合がある。）は７００ｍＬ以上であり、ＪＩＳ　Ｐ　８１２０：１９９８に準拠して測定される繊維粗度（以下、単に「繊維粗度」という。）は０．２００ｍｇ／ｍ以上である。本発明のクラフト紙は、上記構成を有するため、優れた強度と通気性を兼ね備えている。 When the kraft paper of the present invention is dissociated by the pulp dissociation method described in JIS P 8220: 2012, the dissociated pulp obtained (hereinafter, simply referred to as "dissociated pulp") is measured in accordance with JIS P 811-2: 2012. The Canadian standard freeness (hereinafter sometimes referred to as "freeness") is 700 mL or more, and the fiber roughness measured in accordance with JIS P 8120: 1998 (hereinafter, simply referred to as "fiber roughness"). ) Is 0.200 mg / m or more. Since the kraft paper of the present invention has the above-mentioned structure, it has both excellent strength and breathability.
　ＪＩＳ　Ｐ　８１２１－２：２０１２に準拠して測定される離解パルプのフリーネスの上限は、特に制限されないが、８００ｍＬ以下であることが好ましく、７５０ｍＬ以下であることがより好ましく、７３５ｍＬ以下であることがさらに好ましい。離解パルプのフリーネスを７００ｍＬ以上とすることにより、優れた通気性が得られやすくなる。離解パルプのフリーネスを上記上限値以下とすることにより、クラフト紙は、より優れた強度を発揮し易くなる。離解パルプのフリーネスは、叩解等により調整することができる。 The upper limit of the freeness of the dissociated pulp measured in accordance with JIS P 811-2: 2012 is not particularly limited, but is preferably 800 mL or less, more preferably 750 mL or less, and preferably 735 mL or less. More preferred. By setting the freeness of the dissociated pulp to 700 mL or more, excellent air permeability can be easily obtained. By setting the freeness of the dissociated pulp to the above upper limit or less, the kraft paper tends to exhibit more excellent strength. The freeness of the disintegrated pulp can be adjusted by beating or the like.
　クラフト紙のＪＩＳ　Ｐ　８１２４：２０１１に準拠して測定される坪量は、７０ｇ／ｍ２以上であることが好ましく、７５ｇ／ｍ２以上であることがより好ましく、８０ｇ／ｍ２以上であることがさらに好ましい。なお、クラフト紙のＪＩＳ　Ｐ　８１２４：２０１１に準拠して測定される坪量の上限値は特に限定されるものではないが、１５０ｇ／ｍ２以下であることが好ましい。 The basis weight measured according to JIS P 8124: 2011 of kraft paper is preferably 70 g / m 2 or more, more preferably 75 g / m 2 or more, and 80 g / m 2 or more. Is even more preferable. The upper limit of the basis weight measured in accordance with JIS P 8124: 2011 of kraft paper is not particularly limited, but is preferably 150 g / m 2 or less.
　クラフト紙のＪＩＳ　Ｐ　８１４０：１９９８に準拠して測定される、温度２３℃、接触時間６０秒でのコッブ吸水度は、５～４０ｇ／ｍ２であることが好ましく、１０～３５秒であることがより好ましく、１５～２８ｇ／ｍ２であることがさらに好ましく、２０～２５ｇ／ｍ２であることが特に好ましい。 The Cobb water absorption at a temperature of 23 ° C. and a contact time of 60 seconds, measured in accordance with JIS P 8140: 1998 of kraft paper, is preferably 5 to 40 g / m 2 and preferably 10 to 35 seconds. Is more preferable, 15 to 28 g / m 2 is further preferable, and 20 to 25 g / m 2 is particularly preferable.
　坪量に対するコッブ吸水度の比は、０．１０～０．４５であることが好ましく、０．１５～０．４０であることがより好ましく、０．１８～０．３５であることがさらに好ましく、０．２１～０．３５であることが一層好ましく、０．２８～０．３５であることが特に好ましい。ここで、坪量に対するコッブ吸水度の比は、コッブ吸水度／坪量の値である。 The ratio of the water absorption of the cobb to the basis weight is preferably 0.10 to 0.45, more preferably 0.15 to 0.40, and even more preferably 0.18 to 0.35. , 0.21 to 0.35, more preferably 0.28 to 0.35. Here, the ratio of the Cobb water absorption to the basis weight is the value of the Cobb water absorption / basis weight.
　従来、クラフト紙袋においては、積み重ねた状態で保管されている間に、製袋時に使用された糊が反対面にまで浸透し、表面がべたついたり、クラフト紙袋同士が接着してしまうという課題もあった。しかしながら、クラフト紙の坪量、コッブ吸水度及び坪量に対するコッブ吸水度の比を上記範囲内とすることにより、クラフト紙袋を積み重ねた状態で保管しても、製袋時に使用された糊が反対面にまで浸透しにくくすることができる。これにより、表面のべたつき発生を防止し、さらにはクラフト紙袋同士の接着を防ぐことができる。特に、クラフト紙の坪量を上記範囲内とすることにより、接着に必要な充分な量の糊を用いても、積み重ねた状態での保管による反対面への糊の浸透を抑制しやすくなる。また、コッブ吸水度を上記下限値以上とすることにより、クラフト紙同士を糊によってしっかりと接着させやすくなり、コッブ吸水度を上記上限値以下とすることにより、製袋後にクラフト紙袋を積み重ねた際に、糊のしみ出しをより効果的に抑制することができる。さらに、坪量に対するコッブ吸水度の比を上記下限値以上とすることにより、クラフト紙同士を糊によってしっかりと接着させやすくなり、坪量に対するコッブ吸水度の比を上記上限値以下とすることにより、製袋後にクラフト紙袋を積み重ねた際に、糊のしみ出しをより効果的に抑制することができる。 Conventionally, in kraft paper bags, there is a problem that the glue used at the time of bag making permeates to the opposite surface while the kraft paper bags are stored in a stacked state, and the surfaces become sticky or the kraft paper bags adhere to each other. It was. However, by setting the basis weight of kraft paper, the water absorption of the cubs, and the ratio of the water absorption of the cubs to the basis weight within the above range, even if the kraft paper bags are stored in a stacked state, the glue used at the time of bag making is opposite. It can be difficult to penetrate even to the surface. As a result, it is possible to prevent the occurrence of stickiness on the surface and further prevent the kraft paper bags from adhering to each other. In particular, by setting the basis weight of the kraft paper within the above range, even if a sufficient amount of glue required for adhesion is used, it becomes easy to suppress the penetration of the glue into the opposite surface due to storage in a stacked state. In addition, by setting the Cobb water absorption to be equal to or higher than the above lower limit, it becomes easier to firmly bond the kraft papers to each other with glue, and by setting the Cobb water absorption to be equal to or lower than the above upper limit, when the kraft paper bags are stacked after bag making. In addition, the exudation of glue can be suppressed more effectively. Furthermore, by setting the ratio of the Cobb water absorption to the basis weight to the above lower limit or more, it becomes easier to firmly bond the kraft papers to each other with glue, and by setting the ratio of the Cobb water absorption to the basis weight to the above upper limit or less. When kraft paper bags are stacked after bag making, it is possible to more effectively suppress the seepage of glue.
　コッブ吸水度は、例えば、サイズ剤を添加することで調整することができる。サイズ剤としては、ロジン系サイズ剤、アルキルケテンダイマー系サイズ剤、アルケニル無水コハク酸系サイズ剤、合成サイズ剤等が挙げられる。サイズ剤の添加量は、クラフト紙を構成する全パルプの質量（固形分）に対して、０．０５～１．００質量％であることが好ましく、０．１０～０．２０質量％であることがより好ましい。 Cobb water absorption can be adjusted by adding a sizing agent, for example. Examples of the sizing agent include a rosin-based sizing agent, an alkyl ketene dimer-based sizing agent, an alkenyl succinic anhydride-based sizing agent, and a synthetic sizing agent. The amount of the sizing agent added is preferably 0.05 to 1.00% by mass, preferably 0.10 to 0.20% by mass, based on the mass (solid content) of the total pulp constituting the kraft paper. Is more preferable.
　なお、同種のクラフトパルプを用いたクラフト紙であれば、坪量が大きい程コッブ吸水度は大きい値となる。 For kraft paper using the same type of kraft pulp, the larger the basis weight, the larger the Cobb water absorption.
　本発明のクラフト紙をＪＩＳ　Ｐ　８２２０：２０１２に記載のパルプ離解法により離解した場合、得られる離解パルプのＪＩＳ　Ｐ　８１２０：１９９８に規定される繊維粗度（以下、単に「繊維粗度」という。）は、０．２００ｍｇ／ｍ以上である。繊維粗度の上限は、特に限定されないが、０．４００ｍｇ／ｍ以下であることが好ましく、０．３５０ｍｇ／ｍ以下であることがより好ましく、０．３００ｍｇ／ｍ以下であることがさらに好ましく、０．２５０ｍｇ／ｍ以下であることが特に好ましい。繊維粗度は、単位長さあたりの繊維の絶乾質量である。繊維粗度が大きいほど、繊維がカールしており、伸びが発現しやすいことを意味する。 When the kraft paper of the present invention is dissociated by the pulp disintegration method described in JIS P 8220: 2012, the fiber roughness of the dissociated pulp obtained is defined in JIS P 8120: 1998 (hereinafter, simply referred to as "fiber roughness". ) Is 0.200 mg / m or more. The upper limit of the fiber roughness is not particularly limited, but is preferably 0.400 mg / m or less, more preferably 0.350 mg / m or less, and further preferably 0.300 mg / m or less. It is particularly preferably 0.250 mg / m or less. Fiber roughness is the absolute dry mass of fiber per unit length. The larger the fiber roughness, the more curled the fiber and the easier it is for elongation to develop.
　離解パルプの繊維粗度は、原料パルプのルンケル比、原料パルプのカッパー価（Ｋα価）、叩解に使用する刃、叩解時の温度等により調整できる。
　ルンケル比は、平均繊維壁厚（繊維の細胞壁の厚さの平均）の２倍を、ルーメン径の平均直径で割った値である。ルーメン径の平均直径は、平均繊維幅から平均繊維壁厚の２倍を引くことにより求められる。すなわち、ルンケル比は、平均繊維壁厚と平均繊維幅から求められる値である。ルンケル比を求めるために必要な平均繊維壁厚と平均繊維幅は、繊維分析器（メッツォオートメーション社製、カヤーニファイバーラボｖｅｒ４．０）により測定することができる。 The fiber roughness of the disintegrated pulp can be adjusted by the runkel ratio of the raw material pulp, the copper value (Kα value) of the raw material pulp, the blade used for beating, the temperature at the time of beating, and the like.
The Runkel ratio is a value obtained by dividing twice the average fiber wall thickness (average of the cell wall thickness of fibers) by the average diameter of the lumen diameter. The average lumen diameter is determined by subtracting twice the average fiber wall thickness from the average fiber width. That is, the Runkel ratio is a value obtained from the average fiber wall thickness and the average fiber width. The average fiber wall thickness and average fiber width required to obtain the Runkel ratio can be measured by a fiber analyzer (Kajaani FiberLab ver4.0, manufactured by Mezzo Automation).
　原料パルプのルンケル比が低い程、繊維が柔軟であるために叩解による揉みほぐし作用によりカールが付きやすくなり、伸びが発現しやすい。すなわち、繊維粗度が大きくなりやすい。また、ルンケル比が低い程、叩解による物理的な力でつぶれやすくなるため、繊維間結合が増えて強度が向上しやすい。ただし、ルンケル比が低いと引裂強度は低くなる傾向がある。このため、全体としてのバランスを考慮すると、叩解前の原料パルプのルンケル比は、１．５～２．５であることが好ましく、１．７～２．３であることがより好ましい。 The lower the runkel ratio of the raw material pulp, the more flexible the fibers are, and the easier it is to curl due to the kneading and loosening action by beating, and the more easily the elongation is developed. That is, the fiber roughness tends to increase. Further, the lower the Runkel ratio, the easier it is to be crushed by the physical force of beating, so that the interfiber bond is increased and the strength is likely to be improved. However, when the Runkel ratio is low, the tear strength tends to be low. Therefore, considering the balance as a whole, the runkel ratio of the raw material pulp before beating is preferably 1.5 to 2.5, and more preferably 1.7 to 2.3.
　ルンケル比は、広葉樹を原料とするパルプに比べて、針葉樹を原料とするパルプの方が高い。そのため、原料パルプのルンケル比は、針葉樹クラフトパルプと広葉樹クラフトパルプの混合割合により調整できる。ただし、原料パルプは、針葉樹クラフトパルプのみであってもよい。 The Runkel ratio is higher for pulp made from softwood than for pulp made from hardwood. Therefore, the runkel ratio of the raw material pulp can be adjusted by the mixing ratio of the softwood kraft pulp and the hardwood kraft pulp. However, the raw material pulp may be only softwood kraft pulp.
　針葉樹クラフトパルプとしては、針葉樹未晒クラフトパルプ（ＮＵＫＰ）、針葉樹晒クラフトパルプ（ＮＢＫＰ）、針葉樹半晒クラフトパルプ（ＮＳＢＫＰ）、針葉樹亜硫酸パルプ等を挙げることができる。これらは併用してもよい。中でも原料パルプとして針葉樹未晒クラフトパルプ（ＮＵＫＰ）を使用することが、引張破断伸びおよび強度に優れるという点で好ましい。針葉樹クラフトパルプの材種としては、ダグラスファー、アカマツ、スプルース、ラジアータパイン等が挙げられる。中でも、ダグラスファーはルンケル比が高いため好ましく用いられる。原料パルプには、これらから２種以上を組み合わせて用いてもよい。 Examples of the coniferous kraft pulp include unbleached coniferous kraft pulp (NUKP), bleached coniferous kraft pulp (NBKP), semi-bleached coniferous kraft pulp (NSBKP), and coniferous sulfite pulp. These may be used together. Above all, it is preferable to use softwood unbleached kraft pulp (NUKP) as the raw material pulp in terms of excellent tensile elongation at break and strength. Examples of the grades of softwood kraft pulp include Douglas fir, Japanese red pine, spruce, and radiata pine. Among them, Douglas fir is preferably used because it has a high Runkel ratio. Two or more of these may be used in combination as the raw material pulp.
　広葉樹クラフトパルプとしては、広葉樹未晒クラフトパルプ（ＬＵＫＰ）、広葉樹晒クラフトパルプ（ＬＢＫＰ）、広葉樹半晒クラフトパルプ（ＬＳＢＫＰ）、広葉樹亜硫酸パルプ等を挙げることができる。中でも原料パルプとして広葉樹未晒クラフトパルプ（ＬＵＫＰ）を使用することが、強度の点で好ましい。広葉樹クラフトパルプの材種としては、ユーカリ、ブナ、アカシア等が挙げられる。原料パルプには、これらから２種以上を組み合わせて用いてもよい。 Examples of broad-leaved kraft pulp include broad-leaved unbleached kraft pulp (LUKP), broad-leaved bleached kraft pulp (LBKP), broad-leaved semi-bleached kraft pulp (LSBKP), and broad-leaved sulfite pulp. Above all, it is preferable to use hardwood unbleached kraft pulp (LUKP) as the raw material pulp in terms of strength. Examples of hardwood kraft pulp grades include eucalyptus, beech, and acacia. Two or more of these may be used in combination as the raw material pulp.
　Ｋα価は、ＪＩＳ　Ｐ　８２１１：２０１１に準拠して測定されるパルプのリグニン含有量又は漂白性の指標である。原料パルプのＫα価が低い（リグニン少ない）ほど、繊維が柔軟であるため、叩解による揉みほぐし作用によりカールが付きやすくなり、伸びが発現しやすくなる。すなわち、離解パルプの繊維粗度を大きくすることができる。ただし、Ｋα価が低すぎると単繊維強度が低下する場合もある。一方、Ｋα価が高すぎると繊維が硬いため、カールが付きにくく、伸びが発現しにくい場合がある。このため、全体としてのバランスを考慮すると、原料パルプのＫα価は、３５～５５であることが好ましく、３８～５０であることがより好ましい。 The Kα value is an index of the lignin content or bleaching property of pulp measured in accordance with JIS P 8211: 2011. The lower the Kα value of the raw material pulp (less lignin), the more flexible the fibers are, and the more easily the curls are formed by the kneading and loosening action by beating, and the more easily the elongation is developed. That is, the fiber roughness of the disintegrated pulp can be increased. However, if the Kα value is too low, the strength of the single fiber may decrease. On the other hand, if the Kα value is too high, the fibers are hard, so that curling is difficult and elongation may be difficult to develop. Therefore, considering the balance as a whole, the Kα value of the raw material pulp is preferably 35 to 55, and more preferably 38 to 50.
　叩解に使用する刃としては、デラックスファイナー（玄武岩）が好ましい。デラックスファイナーは、コニカル型リファイナーと比べ、ローター、ステーターともに刃幅が広いため、カッティングよりは揉みほぐしに近い叩解となり、カールが付きやすくなり、伸びが発現しやすい。すなわち、離解パルプの繊維粗度を大きくすることができる。また、デラックスファイナーを使用すると、クラフト紙の引裂強度が低下しにくい。 A deluxe finer (basalt) is preferable as the blade used for beating. Compared to the conical type refiner, the deluxe finer has a wider blade width for both the rotor and the stator, so the beating is closer to kneading and loosening than cutting, and it is easy to curl and stretch. That is, the fiber roughness of the disintegrated pulp can be increased. Moreover, when a deluxe finer is used, the tear strength of kraft paper is unlikely to decrease.
　叩解時の温度は、３０～９０℃が好ましく、７０～９０℃がより好ましい。温度を高くする程、カールが付きやすくなり、伸びが発現されやすくなる。すなわち、離解パルプの繊維粗度を大きくすることができる。特に、リグニンの軟化点は７０℃以上であるため、７０℃以上で叩解すると、繊維が軟らかくなり、特にカール（粗度）が付きやすくなる。 The temperature at the time of beating is preferably 30 to 90 ° C, more preferably 70 to 90 ° C. The higher the temperature, the easier it is for curling and the more likely it is to develop elongation. That is, the fiber roughness of the disintegrated pulp can be increased. In particular, since the softening point of lignin is 70 ° C. or higher, when the lignin is beaten at 70 ° C. or higher, the fibers become soft and curl (roughness) is particularly likely to occur.
　クラフト紙のＪＩＳ　Ｐ　８１１６：２０００に準拠して測定される縦方向の比引裂強さは、特に限定されないが、落下衝撃耐性の観点から、１５．０ｍＮ・ｍ２／ｇ以上であることが好ましく、１６．０ｍＮ・ｍ２／ｇ以上であることがより好ましく、１７．０ｍＮ・ｍ２／ｇ以上であることがさらに好ましく、１７．５ｍＮ・ｍ２／ｇ以上であることが一層好ましく、１８．０ｍＮ・ｍ２／ｇ以上であることが特に好ましい。縦方向の比引裂強さの上限は、特に限定されないが、２５．０ｍＮ・ｍ２／ｇ以下であることが好ましい。また、クラフト紙のＪＩＳ　Ｐ　８１１６：２０００に準拠して測定される横方向の比引裂強さは、特に限定されないが、１８．０ｍＮ・ｍ２／ｇ以上であることが好ましく、２０．０ｍＮ・ｍ２／ｇ以上であることがより好ましく、２２．０ｍＮ・ｍ２／ｇ以上であることがさらに好ましく、２３．０ｍＮ・ｍ２／ｇ以上であることが特に好ましい。横方向の比引裂強さは、特に限定されないが、落下衝撃耐性の観点から、２８．０ｍＮ・ｍ２／ｇ以下であることが好ましく、２６．０ｍＮ・ｍ２／ｇ以下であることがより好ましく、２５．０ｍＮ・ｍ２／ｇ以下であることがさらに好ましく、２４．０ｍＮ・ｍ２／ｇ以下であることが特に好ましい。縦方向及び横方向の比引裂強さが上記下限値以上であれば、内容物の充填、輸送、保管等の工程において破袋が生じにくいクラフト紙袋を得ることができる。縦方向及び横方向の比引裂強さは、離解パルプのフリーネスが大きい程、高い値となりやすい傾向がある。なお、本明細書において、横方向とは抄紙機の幅方向をいい、縦方向とは抄紙機の流れ方向をいう。 The specific tear strength in the vertical direction measured in accordance with JIS P 8116: 2000 of kraft paper is not particularly limited, but is preferably 15.0 mN · m 2 / g or more from the viewpoint of drop impact resistance. , 16.0 mN · m 2 / g or more, more preferably 17.0 mN · m 2 / g or more, further preferably 17.5 mN · m 2 / g or more, 18 It is particularly preferable that the content is 0.0 mN · m 2 / g or more. The upper limit of the relative tear strength in the longitudinal direction is not particularly limited, but is preferably 25.0 mN · m 2 / g or less. The lateral specific tear strength measured in accordance with JIS P 8116: 2000 of kraft paper is not particularly limited, but is preferably 18.0 mN · m 2 / g or more, and 20.0 mN ·. more preferably m 2 / g or more, still more preferably 22.0MN · m 2 / g or more, particularly preferably 23.0MN · m 2 / g or more. The ratio tear strength in the transverse direction is not particularly limited, from the viewpoint of the drop impact resistance is preferably at most 28.0mN · m 2 / g, more not more than 26.0mN · m 2 / g preferably, more preferably at most 25.0mN · m 2 / g, particularly preferably not more than 24.0mN · m 2 / g. When the relative tear strength in the vertical direction and the horizontal direction is equal to or higher than the above lower limit value, a kraft paper bag that is unlikely to break in the steps of filling, transporting, and storing the contents can be obtained. The relative tear strength in the longitudinal direction and the lateral direction tends to be higher as the freeness of the disintegrated pulp is larger. In the present specification, the horizontal direction means the width direction of the paper machine, and the vertical direction means the flow direction of the paper machine.
　クラフト紙のＪＩＳ　Ｐ　８１１３：２００６に準拠して測定される縦方向の引張破断伸びは、落下衝撃耐性および／または糊の浸透抑制の観点から、６．０％以上であることが好ましく、７．０％以上であることがより好ましく、７．５％以上であることがさらに好ましく、８．０％以上であることが一層好ましく、８．５％以上であることが特に好ましい。縦方向の引張破断伸びは、特に限定されないが、１２．０％以下であることが好ましく、１０．０％以下であることがより好ましい。また、クラフト紙のＪＩＳ　Ｐ　８１１３：２００６に準拠して測定される横方向の引張破断伸びは、特に限定されないが、４．０％以上であることが好ましく、５．０％以上であることがより好ましく、６．０％以上であることがさらに好ましく、６．５％以上であることが特に好ましい。横方向の引張破断伸びは、特に限定されないが、１０．０％以下であることが好ましく、９．０％以下であることがより好ましく、８．０％以下であることがさらに好ましい。縦方向及び横方向の引張破断伸びが上記下限値以上であれば、内容物の充填、輸送、保管等の工程において破袋が生じにくいクラフト紙袋を得ることができる。縦方向及び横方向の引張破断伸びは、離解パルプの繊維粗度が大きい程、高い値となりやすい傾向がある。 The tensile elongation at break in the vertical direction measured in accordance with JIS P 8113: 2006 of kraft paper is preferably 6.0% or more from the viewpoint of drop impact resistance and / or suppression of glue penetration. It is more preferably 0% or more, further preferably 7.5% or more, further preferably 8.0% or more, and particularly preferably 8.5% or more. The tensile elongation at break in the longitudinal direction is not particularly limited, but is preferably 12.0% or less, and more preferably 10.0% or less. Further, the tensile elongation at break in the lateral direction measured in accordance with JIS P 8113: 2006 of kraft paper is not particularly limited, but is preferably 4.0% or more, and preferably 5.0% or more. More preferably, it is more preferably 6.0% or more, and particularly preferably 6.5% or more. The tensile elongation at break in the lateral direction is not particularly limited, but is preferably 10.0% or less, more preferably 9.0% or less, and further preferably 8.0% or less. When the tensile elongation at break in the vertical direction and the horizontal direction is at least the above lower limit value, a kraft paper bag that is unlikely to break in the steps of filling, transporting, and storing the contents can be obtained. The tensile elongation at break in the longitudinal direction and the transverse direction tends to be higher as the fiber roughness of the dissociated pulp is larger.
　クラフト紙のＪＩＳ　Ｐ　８１１３：２００６に規定される縦方向の比引張エネルギー吸収量は、２．５Ｊ／ｇ以上であることが好ましく、２．８Ｊ／ｇ以上であることがより好ましく、３．０Ｊ／ｇ以上であることがさらに好ましい。また、クラフト紙のＪＩＳ　Ｐ　８１１３：２００６に規定される横方向の比引張エネルギー吸収量は、落下衝撃耐性および／または糊の浸透抑制の観点から、１．５Ｊ／ｇ以上であることが好ましく、２．０Ｊ／ｇ以上であることがより好ましく、２．３Ｊ／ｇ以上であることがさらに好ましく、２．５Ｊ／ｇ以上であることが一層好ましく、２．８Ｊ／ｇ以上であることが特に好ましい。縦方向及び横方向の比引張エネルギー吸収量が上記下限値以上であれば、内容物の充填、輸送、保管等の工程において破袋が生じにくいクラフト紙袋を得ることができる。縦方向及び横方向の比引張エネルギー吸収量は、離解パルプの繊維粗度が大きい程、高い値となりやすい傾向がある。 The amount of specific tensile energy absorbed in the vertical direction specified in JIS P 8113: 2006 of kraft paper is preferably 2.5 J / g or more, more preferably 2.8 J / g or more, and 3.0 J. It is more preferably / g or more. Further, the lateral specific tensile energy absorption amount specified in JIS P 8113: 2006 of kraft paper is preferably 1.5 J / g or more from the viewpoint of drop impact resistance and / or suppression of glue penetration. It is more preferably 2.0 J / g or more, further preferably 2.3 J / g or more, further preferably 2.5 J / g or more, and particularly preferably 2.8 J / g or more. preferable. When the specific tensile energy absorption amount in the vertical direction and the horizontal direction is equal to or higher than the above lower limit value, a kraft paper bag that is less likely to break in the process of filling, transporting, storing, etc. of the contents can be obtained. The amount of specific tensile energy absorbed in the longitudinal direction and the lateral direction tends to be higher as the fiber roughness of the disintegrated pulp is larger.
　クラフト紙のＪＩＳ　Ｐ　８１１７：２００９に準拠して測定される透気抵抗度は、５０秒以下であることが好ましく、３０秒以下であることがより好ましく、２０秒以下であることがさらに好ましく、１０秒以下であることが一層好ましく、７秒以下であることが特に好ましい。また、クラフト紙のＪＩＳ　Ｐ　８１１７：２００９に準拠して測定される透気抵抗度は、０秒以上であることが好ましい。透気抵抗度が上記上限値以下であることにより、通気性に優れたクラフト紙を得ることができる。透気抵抗度は、離解パルプのフリーネスが大きい程、低い値となりやすい傾向がある。 The air permeability resistance measured in accordance with JIS P 8117: 2009 of kraft paper is preferably 50 seconds or less, more preferably 30 seconds or less, further preferably 20 seconds or less. It is more preferably 10 seconds or less, and particularly preferably 7 seconds or less. Further, the air permeation resistance measured in accordance with JIS P 8117: 2009 of kraft paper is preferably 0 seconds or more. When the air permeation resistance is not more than the above upper limit value, kraft paper having excellent breathability can be obtained. The air permeation resistance tends to be lower as the freeness of the dissociated pulp increases.
　クラフト紙は、クラフトパルプの他に任意成分を含んでいてもよい。任意成分としては、サイズ剤、アニオン性、カチオン性もしくは両性の歩留向上剤、濾水性向上剤、乾燥紙力増強剤、湿潤紙力増強剤、填料等の内添薬品、耐水化剤、染料、蛍光増白剤等が挙げられる。 Kraft paper may contain arbitrary components in addition to kraft pulp. Optional components include sizing agents, anionic, cationic or amphoteric yield improvers, drainage improvers, dry paper strength enhancers, wet paper strength enhancers, internal chemicals such as fillers, water resistant agents, and dyes. , Fluorescent whitening agent and the like.
　サイズ剤としては、ロジン、アルキルケテンダイマー（ＡＫＤ）等の内添サイズ剤；スチレン／アクリル酸共重合体、スチレン／メタクリル酸共重合体等の表面サイズ剤が挙げられる。サイズ剤の配合量は、特に限定されないが、原料パルプ１００質量部（固形分換算）に対して、好ましくは１．０質量部以下、より好ましくは０．５０質量部以下、さらに好ましくは０．３０質量部以下、一層好ましくは０．２０質量部以下である。また、サイズ剤の配合量は、原料パルプ１００質量部に対して０質量部以上であることが好ましい。 Examples of the sizing agent include internal sizing agents such as rosin and alkyl ketene dimer (AKD); surface sizing agents such as styrene / acrylic acid copolymer and styrene / methacrylic acid copolymer. The blending amount of the sizing agent is not particularly limited, but is preferably 1.0 part by mass or less, more preferably 0.50 part by mass or less, and further preferably 0.% by mass with respect to 100 parts by mass (solid content equivalent) of the raw material pulp. It is 30 parts by mass or less, more preferably 0.20 parts by mass or less. The blending amount of the sizing agent is preferably 0 parts by mass or more with respect to 100 parts by mass of the raw material pulp.
　歩留向上剤としては、ポリアクリルアミド、硫酸バンド等が挙げられる。歩留向上剤の配合量は、特に限定されないが、原料パルプ１００質量部（固形分換算）に対して、好ましくは５．０質量部以下であり、より好ましくは３．０質量部以下、さらに好ましくは２．５質量部以下である。また、歩留向上剤の配合量は、原料パルプ１００質量部に対して０質量部以上であることが好ましい。 Examples of the yield improving agent include polyacrylamide and sulfuric acid band. The amount of the yield improving agent to be blended is not particularly limited, but is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and further, with respect to 100 parts by mass (solid content equivalent) of the raw material pulp. It is preferably 2.5 parts by mass or less. Further, the blending amount of the yield improving agent is preferably 0 parts by mass or more with respect to 100 parts by mass of the raw material pulp.
　乾燥紙力増強剤としては、カチオン化澱粉、ポリアクリルアミド、カルボキシメチルセルロース等が挙げられる。乾燥紙力増強剤の配合量は、特に限定されないが、原料パルプ１００質量部（固形分換算）に対して、好ましくは３．０質量部以下、より好ましくは２．０質量部以下である。また、乾燥紙力増強剤の配合量は、原料パルプ１００質量部に対して０質量部以上であることが好ましい。 Examples of the dry paper strength enhancer include cationized starch, polyacrylamide, carboxymethyl cellulose and the like. The amount of the dry paper strength enhancer to be blended is not particularly limited, but is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, based on 100 parts by mass (solid content equivalent) of the raw material pulp. The blending amount of the dry paper strength enhancer is preferably 0 parts by mass or more with respect to 100 parts by mass of the raw material pulp.
　湿潤紙力増強剤としては、ポリアミドポリアミンエピクロロヒドリン（ＰＡＥ）、尿素ホルムアルデヒド樹脂、メラミンホルムアルデヒド樹脂等が挙げられ、湿潤紙力増強剤はＰＡＥであることが好ましい。紙基材中の湿潤紙力増強剤の配合量は、特に限定されないが、原料パルプ１００質量部（固形分換算）に対して、好ましくは０．０５質量部以上、より好ましくは０．０７質量部以上である。また、湿潤紙力増強剤の配合量は原料パルプ１００質量部に対して好ましくは１．０質量部以下、より好ましくは０．７質量部以下である。 Examples of the wet paper strength enhancer include polyamide polyamine epichlorohydrin (PAE), urea formaldehyde resin, melamine formaldehyde resin, and the like, and the wet paper strength enhancer is preferably PAE. The blending amount of the wet paper strength enhancer in the paper base material is not particularly limited, but is preferably 0.05 parts by mass or more, more preferably 0.07 parts by mass with respect to 100 parts by mass (solid content equivalent) of the raw material pulp. It is more than a department. The amount of the wet paper strength enhancer blended is preferably 1.0 part by mass or less, and more preferably 0.7 part by mass or less with respect to 100 parts by mass of the raw material pulp.
　填料としては、クレー、タルク、カオリン、焼成カオリン、炭酸カルシウム、硫酸カルシウム、硫酸バリウム、二酸化チタン、酸化亜鉛、アルミナ、炭酸マグネシウム、酸化マグネシウム、シリカ、ホワイトカーボン、ベントナイト、ゼオライト、セリサイト、スメクタイト等の無機填料；アクリル系樹脂、塩化ビニリデン系樹脂等の有機填料が挙げられる。 Fillers include clay, talc, kaolin, calcined kaolin, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, alumina, magnesium carbonate, magnesium oxide, silica, white carbon, bentonite, zeolite, sericite, smectite, etc. Inorganic fillers; organic fillers such as acrylic resins and vinylidene chloride resins can be mentioned.
　クラフト紙は、塗工層を有するものであってもよい。塗工層は、澱粉等の天然接着剤やポリビニルアルコール、ポリアクリルアミド、スチレン-ブタジエン共重合体樹脂、アクリル樹脂などの合成接着剤を主成分とする塗工層であることが好ましい。クラフト紙が塗工層を有する場合、塗工層の塗工量は０．３～３．０ｇ／ｍ２であることが好ましい。 The kraft paper may have a coating layer. The coating layer is preferably a coating layer containing a natural adhesive such as starch or a synthetic adhesive such as polyvinyl alcohol, polyacrylamide, styrene-butadiene copolymer resin, and acrylic resin as a main component. When the kraft paper has a coating layer, the coating amount of the coating layer is preferably 0.3 to 3.0 g / m 2 .
［クラフト紙の製造方法］
　本発明のクラフト紙の製造方法は、木材チップを主原料にして、クラフト法で蒸解し、未晒クラフトパルプを得る工程と、この未晒クラフトパルプを叩解してパルプスラリーを得る工程と、パルプスラリーを抄紙する工程と、を含むことが好ましい。なお、このパルプスラリーには未晒クラフトパルプ以外のパルプが添加されていてもよい。また、パルプスラリーには、本発明の効果を損なわない範囲で上記の内添薬品が添加されていてもよい。 [Kraft paper manufacturing method]
The method for producing kraft paper of the present invention includes a step of using wood chips as a main raw material and steaming it by a kraft method to obtain unbleached kraft pulp, a step of beating the unbleached kraft pulp to obtain pulp slurry, and pulp. It is preferable to include a step of making a pulp of the slurry. In addition, pulp other than unbleached kraft pulp may be added to this pulp slurry. Further, the above-mentioned internal chemicals may be added to the pulp slurry as long as the effects of the present invention are not impaired.
　サイズ剤としては、上述したサイズ剤を添加することが好ましい。また、サイズ剤の添加量は、スラリー中に含まれる全パルプの質量（固形分）に対して、０．０５～１．００質量％であることが好ましく、０．１０～０．２０質量％であることがより好ましい。 As the sizing agent, it is preferable to add the above-mentioned sizing agent. The amount of the sizing agent added is preferably 0.05 to 1.00% by mass, preferably 0.10 to 0.20% by mass, based on the mass (solid content) of the total pulp contained in the slurry. Is more preferable.
　未晒クラフトパルプを叩解してパルプスラリーを得る工程では、叩解後のパルプスラリーには、乾燥紙力増強剤を加えることが好ましい。乾燥紙力増強剤の添加量は、スラリー中に含まれる全パルプの質量（固形分）に対して、０．５～３．０質量％であることが好ましい。カチオン化澱粉を加えることにより、クラフト紙の強度が増強され、かつ破断伸びのよいクラフト紙を得ることができる。 In the step of beating unbleached kraft pulp to obtain a pulp slurry, it is preferable to add a dry paper strength enhancer to the pulp slurry after beating. The amount of the dry paper strength enhancer added is preferably 0.5 to 3.0% by mass with respect to the mass (solid content) of the total pulp contained in the slurry. By adding the cationized starch, the strength of the kraft paper is enhanced, and the kraft paper having good breaking elongation can be obtained.
　例えば、離解パルプのフリーネスを７００～７５０ｍＬとするために、叩解は、仕上がりのフリーネスが６７０～７５０ｍＬとなるまで行うことが好ましい。また、例えば、離解パルプの繊維粗度を０．２００ｍｇ／ｍ以上とするために、叩解は、仕上がりの繊維粗度が０．１６０～０．２５０ｍｇ／ｍとなるまで行うことが好ましい。 For example, in order to set the freeness of the disintegrated pulp to 700 to 750 mL, it is preferable to perform beating until the finished freeness is 670 to 750 mL. Further, for example, in order to make the fiber roughness of the disintegrated pulp 0.200 mg / m or more, it is preferable to perform beating until the finished fiber roughness becomes 0.160 to 0.250 mg / m.
　未晒クラフトパルプを叩解してパルプスラリーを得る工程では、叩解時の温度を、３０～９０℃とすることが好ましく、７０～９０℃とすることがより好ましい。温度を高くする程、カールが付きやすくなり、伸びが発現されやすくなる。すなわち、離解パルプの繊維粗度を大きくすることができる。特に、リグニンの軟化点は７０℃以上であるため、７０℃以上で叩解すると、繊維が軟らかくなり、特にカール（粗度）が付きやすくなる。 In the step of beating unbleached kraft pulp to obtain a pulp slurry, the temperature at the time of beating is preferably 30 to 90 ° C, more preferably 70 to 90 ° C. The higher the temperature, the easier it is for curling and the more likely it is to develop elongation. That is, the fiber roughness of the disintegrated pulp can be increased. In particular, since the softening point of lignin is 70 ° C. or higher, when the lignin is beaten at 70 ° C. or higher, the fibers become soft and curl (roughness) is particularly likely to occur.
　クラフト紙の抄紙方法および抄紙機の型式としては、長網抄紙機、短網抄紙機、ツインワイヤー抄紙機、円網抄紙機、ギャップフォーマー式抄紙機等の公知の抄紙方法および抄紙機が選択可能である。また、クレープ加工等の特殊な処理は、必要により行うことができる。 Known paper making methods and paper machines such as long net paper machines, short net paper machines, twin wire paper machines, circular net paper machines, and gap former paper machines are selected as the kraft paper paper making method and the paper machine type. It is possible. In addition, special processing such as crepe processing can be performed if necessary.
　クラフト紙の製造工程では、表面性向上のため、各種の仕上げ装置、例えば、マシンカレンダーやソフトニップカレンダー等に通紙して、製品仕上げを施すことも可能である。 In the kraft paper manufacturing process, in order to improve the surface quality, it is possible to finish the product by passing it through various finishing devices such as a machine calendar and a soft nip calendar.
［クラフト紙袋］
　本発明のクラフト紙袋は、上述したクラフト紙を製袋したものである。袋の形状に特に限定はないが、例えば、ＪＩＳ　Ｚ　０１０２：２００４に記載のひだなし開口式ミシン縫い袋、ひだなしバルブ付きミシン縫い袋等のミシン縫い袋や、ひだなし開口式底ばり袋、ひだなしバルブ付き底ばり袋等ののりばり袋が挙げられる。 [Craft paper bag]
The kraft paper bag of the present invention is a bag made from the above-mentioned kraft paper. The shape of the bag is not particularly limited. Examples include a glue bag such as a bottom bag with a foldless valve.
　クラフト紙を製袋する際には糊を使用してもよい。製袋時に使用する糊としては、酢酸ビニル共重合体、エチレン‐酢酸ビニル共重合体、アクリル系共重合体、ホットメルト樹脂、カルボキシメチルセルロース等が挙げられる。製袋時に使用する糊の溶媒としては、水が好ましい。この際、製袋時に使用する糊の乾燥塗工量は、１５～２３ｇ／ｍ２であることが好ましい。乾燥塗工量が上記下限値以上であれば、糊によってしっかりと接着させることができるので、製袋しやすい。また、乾燥塗工量が上記上限値以下であれば、製袋後にクラフト紙袋を積み重ねても、糊がしみ出しにくい。 Glue may be used when making kraft paper bags. Examples of the glue used during bag making include vinyl acetate copolymers, ethylene-vinyl acetate copolymers, acrylic copolymers, hot melt resins, and carboxymethyl cellulose. Water is preferable as the solvent for the glue used during bag making. At this time, the dry coating amount of the glue used at the time of bag making is preferably 15 to 23 g / m 2 . When the dry coating amount is equal to or more than the above lower limit value, it can be firmly adhered with glue, so that bag making is easy. Further, if the dry coating amount is not more than the above upper limit value, the glue does not easily seep out even if the kraft paper bags are stacked after the bag is made.
　本発明のクラフト紙袋は、強度をより高めるため、２層以上の多層紙袋とすることが好ましい。クラフト紙袋を多層紙袋とする場合、例えば、上述したクラフト紙に合成樹脂層を積層した構成としてもよく、クラフト紙／合成樹脂層／クラフト紙の３層構成としてもよい。また、クラフト紙袋を多層紙袋とする場合、各層間には接着剤層が設けられていてもよい。 The kraft paper bag of the present invention is preferably a multi-layer paper bag having two or more layers in order to further increase the strength. When the kraft paper bag is a multi-layer paper bag, for example, it may have a structure in which a synthetic resin layer is laminated on the above-mentioned kraft paper, or a three-layer structure of kraft paper / synthetic resin layer / kraft paper. Further, when the kraft paper bag is a multi-layer paper bag, an adhesive layer may be provided between each layer.
　本発明のクラフト紙袋は強靭な紙袋であるため、内容物を重量単位に包装しその重さと取り扱いに耐える重包装用紙袋として使用できる。また、本発明のクラフト紙袋の内容物に特に限定はないが、通気性に優れ、風送充填に適しているため、内容物としては、粉体又は粒状体のものが好ましい。すなわち、本発明のクラフト紙袋は粉体収容用であることが好ましい。 Since the kraft paper bag of the present invention is a tough paper bag, it can be used as a heavy wrapping paper bag that can withstand the weight and handling of the contents by wrapping the contents in weight units. The contents of the kraft paper bag of the present invention are not particularly limited, but powder or granular materials are preferable as the contents because they are excellent in air permeability and suitable for air-filling. That is, the kraft paper bag of the present invention is preferably for containing powder.
　以下、実施例により本発明を詳細に説明するが、本発明は下記実施例に限定されるものではない。なお、％は特に断りのない限り質量％である。 Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples. In addition,% is mass% unless otherwise specified.
［測定方法、評価方法］
（ルンケル比）
　離解パルプのルンケル比は、上記平均繊維幅と平均繊維壁厚から計算により求めた。ルンケル比は、平均繊維壁厚（繊維の細胞壁の厚さの平均）の２倍を、ルーメン径の平均直径で除することにより算出した。 [Measurement method, evaluation method]
(Runkel ratio)
The Runkel ratio of the dissociated pulp was calculated from the average fiber width and the average fiber wall thickness. The Runkel ratio was calculated by dividing twice the average fiber wall thickness (the average fiber cell wall thickness) by the average lumen diameter.
（離解パルプのフリーネス）
　下記実施例および比較例で製造したクラフト紙をＪＩＳ　Ｐ　８２２０：２０１２に記載のパルプ離解法により離解し、離解パルプを得た。離解パルプのフリーネスは、ＪＩＳ　Ｐ　８１２１－２：２０１２に規定される方法により測定した。 (Freeness of dissociated pulp)
The kraft paper produced in the following Examples and Comparative Examples was disintegrated by the pulp dissociation method described in JIS P 8220: 2012 to obtain dissociated pulp. The freeness of the disintegrated pulp was measured by the method specified in JIS P 811-2: 2012.
（Ｋα価）
　離解パルプのＫα価は、ＪＩＳ　Ｐ　８２１１：２０１１に規定されている方法により測定した。 (Kα value)
The Kα value of the dissociated pulp was measured by the method specified in JIS P 8211: 2011.
（離解パルプの繊維粗度）
　下記実施例および比較例で製造したクラフト紙をＪＩＳ　Ｐ　８２２０：２０１２に記載のパルプ離解法により離解し、離解パルプを得た。ＪＩＳ　Ｐ　８１２０：１９９８に準拠し、離解パルプを０．０２質量％まで水で希釈したスラリーから２５ｍＬ（絶乾パルプ５ｍｇ相当）を正確に取り分け、メッツォオートメーション社製、カヤーニファイバーラボｖｅｒ４．０を用いて、離解パルプの繊維粗度を測定した。 (Fiber roughness of disintegrated pulp)
The kraft paper produced in the following Examples and Comparative Examples was disintegrated by the pulp dissociation method described in JIS P 8220: 2012 to obtain dissociated pulp. In accordance with JIS P 8120: 1998, accurately separate 25 mL (equivalent to 5 mg of absolute dry pulp) from a slurry obtained by diluting dissociated pulp with water to 0.02% by mass, and use Kajaani FiberLab ver4.0 manufactured by Metso Automation Co., Ltd. The fiber roughness of the disintegrated pulp was measured.
（坪量、密度）
　ＪＩＳ　Ｐ　８１２４：２０１１に規定される方法に準拠してクラフト紙の坪量を測定した。続いてＪＩＳ　Ｐ　８１１８：２０１４に規定される方法で、クラフト紙の厚さを測定した。坪量を紙厚で除した値を、クラフト紙の密度とした。 (Basis weight, density)
The basis weight of kraft paper was measured according to the method specified in JIS P 8124: 2011. Subsequently, the thickness of the kraft paper was measured by the method specified in JIS P 8118: 2014. The value obtained by dividing the basis weight by the paper thickness was taken as the density of kraft paper.
（比引裂強さ）
　ＪＩＳ　Ｐ　８１１６：２０００に規定される方法により、引裂試験機（東洋精機社製、エレメンドルフ引裂試験機（ＳＡ－Ｗ型））を用いて、クラフト紙の縦方向（ＭＤ方向）及び横方向（ＣＤ方向）の引裂強さを測定した。各々の引裂強さを坪量で除すことにより、クラフト紙の縦方向（ＭＤ方向）及び横方向（ＣＤ方向）の比引裂強さを求めた。 (Ratio tear strength)
Using a tear tester (Elemendorff tear tester (SA-W type) manufactured by Toyo Seiki Co., Ltd.) according to the method specified in JIS P 8116: 2000, the kraft paper is used in the vertical direction (MD direction) and the horizontal direction (MD direction). The tear strength in the CD direction) was measured. The specific tear strength of the kraft paper in the vertical direction (MD direction) and the horizontal direction (CD direction) was determined by dividing each tear strength by the basis weight.
（引張破断伸び）
　ＪＩＳ　Ｐ　８１１３：２００６に規定される方法により、横型引張試験機（Ｌ＆Ｗ社製、ＣＯＤＥ　ＳＥ－０６４）を用いて、クラフト紙の縦方向（ＭＤ方向）及び横方向（ＣＤ方向）の引張破断伸びを測定した。 (Tensile breaking elongation)
Tensile breaking elongation of kraft paper in the vertical direction (MD direction) and the horizontal direction (CD direction) using a horizontal tensile tester (manufactured by L & W, CODE SE-064) by the method specified in JIS P 8113: 2006. Was measured.
（比引張エネルギー吸収量（ＴＥＡＩ））
　ＪＩＳ　Ｐ　８１１３：２００６に規定される方法により、横型引張試験機（Ｌ＆Ｗ社製、ＣＯＤＥ　ＳＥ－０６４）を用いて、クラフト紙の縦方向（ＭＤ方向）及び横方向（ＣＤ方向）の引張エネルギー吸収量を測定した。各々の引張エネルギー吸収量を坪量で除すことにより、クラフト紙の縦方向（ＭＤ方向）及び横方向（ＣＤ方向）の比引張エネルギー吸収量（ＴＥＡＩ）を求めた。 (Specific tensile energy absorption (TEAI))
Absorption of tensile energy in the vertical direction (MD direction) and horizontal direction (CD direction) of kraft paper using a horizontal tensile tester (manufactured by L & W, CODE SE-064) by the method specified in JIS P 8113: 2006. The amount was measured. By dividing each tensile energy absorption amount by the basis weight, the specific tensile energy absorption amount (TEAI) of the kraft paper in the vertical direction (MD direction) and the horizontal direction (CD direction) was determined.
（コッブ吸水度（６０秒））
　ＪＩＳ　Ｐ　８１４０：１９９８に規定される方法により、温度２３℃、接触時間を６０秒としクラフト紙のコッブ吸水度を測定した。 (Cobb water absorption (60 seconds))
The Cobb water absorption of kraft paper was measured at a temperature of 23 ° C. and a contact time of 60 seconds by the method specified in JIS P 8140: 1998.
（透気抵抗度）
　ＪＩＳ　Ｐ　８１１７：２００９に規定される方法により、王研式試験機（旭精工社製、デジタル型王研式透気度・平滑度試験機）でクラフト紙の透気抵抗度を測定した。 (Air permeability resistance)
The air permeability resistance of kraft paper was measured by a method specified in JIS P 8117: 2009 with an Oken type testing machine (manufactured by Asahi Seiko Co., Ltd., digital type Oken type air permeability / smoothness testing machine).
（充填性・破袋適性）
　クラフト紙を、高さ３７０ｍｍ，奥行き９５ｍｍ，幅３２０ｍｍのＪＩＳ　Ｚ　１５０５：２００４に規定されるひだなしバルブ付き底ばり袋に加工し、２５ｋｇまたは４０ｋｇのセメントを風送により５秒で充填した後の袋を、以下の基準でそれぞれ評価した。
◎：エアーが素早く抜け、破袋せずに充填が極めてよく行えた。
○：一部に破袋が見られたが使用上問題ない。
△：破袋が発生し使用上問題があった。
×：破袋が多く発生した。 (Fillability / bag breakability)
After processing kraft paper into a bottom bladder bag with a foldless valve specified in JIS Z 1505: 2004 with a height of 370 mm, a depth of 95 mm, and a width of 320 mm, and filling 25 kg or 40 kg of cement by air blowing in 5 seconds. The bags were evaluated according to the following criteria.
⊚: Air was released quickly, and filling was extremely good without breaking the bag.
◯: A broken bag was found in some parts, but there is no problem in use.
Δ: A bag was broken and there was a problem in use.
X: Many bag breaks occurred.
（落下衝撃特性）
　クラフト紙を、高さ３７０ｍｍ，奥行き９５ｍｍ，幅３２０ｍｍのＪＩＳ　Ｚ　１５０５：２００４に規定されるひだなしバルブ付き底ばり袋に加工し、２５ｋｇのセメントを風送により充填した。セメントを充填した袋を、ＪＩＳ　Ｚ　０２１７：１９９８に基づき、高さ１．２ｍから水平落下させ、破袋に至るまでの回数を数え、以下の基準で評価した。
◎：破袋に至るまでの回数が１０回以上。
△：破袋に至るまでの回数が８回以上９回以下。
×：破袋に至るまでの回数が７回以下。 (Drop impact characteristics)
Kraft paper was processed into a bottom bladder bag with a foldless valve specified in JIS Z 1505: 2004 having a height of 370 mm, a depth of 95 mm and a width of 320 mm, and 25 kg of cement was filled by air blowing. Based on JIS Z 0217: 1998, the cement-filled bag was dropped horizontally from a height of 1.2 m, and the number of times until the bag was broken was counted and evaluated according to the following criteria.
⊚: The number of times until the bag is broken is 10 times or more.
Δ: The number of times until the bag is broken is 8 times or more and 9 times or less.
X: The number of times until the bag is broken is 7 times or less.
（糊付け適性Ａ（接着性））
　各例のクラフト紙を幅３０ｍｍ、長さ１５０ｍｍにカットし、０．３ｍＬの水溶性糊（日栄化工株式会社製ライフボンドＰ－８１００、濃度４８質量％）を薄く伸ばして幅７ｍｍ、長さ１０ｃｍの部分に塗布し、同じ例の他のクラフト紙を重ねて接着した。これを３セット重ね、上から５ｋｇの重りをのせて、一日放置した後、接着部分の剥離を試み評価した。
◎：糊付けした部分のクラフト紙同士が完全に接着している。
△：概ね接着しているが、一部接着していない部分がある。
×：ほとんど接着しておらず、容易に剥離できる。 (Adhesiveness A (adhesiveness))
Cut the kraft paper of each example into a width of 30 mm and a length of 150 mm, and thinly stretch 0.3 mL of water-soluble glue (Lifebond P-8100 manufactured by Niei Kako Co., Ltd., concentration 48% by mass) to a width of 7 mm and a length of 10 cm. It was applied to the part of, and other kraft papers of the same example were layered and glued. Three sets of these were stacked, a weight of 5 kg was placed on the top, and the mixture was left for a day, and then the adhesive portion was tried to be peeled off and evaluated.
⊚: The glued parts of the kraft paper are completely adhered to each other.
Δ: Mostly adhered, but some parts are not adhered.
X: Almost no adhesion and easy peeling.
（糊付け適性Ｂ（糊の浸透性））
　各例のクラフト紙を５０ｍｍ角にカットし、１．５ｍＬの水溶性糊（日栄化工株式会社製ライフボンドＰ－８１００、濃度４８質量％）をクラフト紙の中央部の面積３ｃｍ２の部分に塗布し、同じ例の他のクラフト紙を重ねて接着した。これを３セット重ね、上から５ｋｇの重りをのせて、６時間放置した後、糊の浸透を評価した。
◎：糊付けした部分の反対面へ糊が浸透していない。
△：糊付けした部分の反対面へ糊がやや浸透しているが、反対面においてべたつきは見られない。
×：糊付けした部分の反対面へ糊が浸透しており、他の紙と接着している。 (Glue suitability B (glue permeability))
Cut the kraft paper of each example into 50 mm squares, and apply 1.5 mL of water-soluble glue (Lifebond P-8100 manufactured by Niei Kako Co., Ltd., concentration 48% by mass) to the central part of the kraft paper with an area of 3 cm 2. Then, other kraft papers of the same example were layered and glued. Three sets of these were stacked, a weight of 5 kg was placed on the top, and the mixture was left for 6 hours, and then the penetration of the glue was evaluated.
⊚: The glue has not penetrated to the opposite surface of the glued part.
Δ: The glue has penetrated slightly to the opposite surface of the glued portion, but no stickiness is observed on the opposite surface.
X: The glue has penetrated into the opposite surface of the glued part and is adhered to other paper.
［原料パルプ］
クラフトパルプ（１）：ダグラスファーを原料とする針葉樹未晒クラフトパルプ（ＮＵＫＰ）。
クラフトパルプ（２）：国内松を原料とする針葉樹未晒クラフトパルプ（ＮＵＫＰ）。
クラフトパルプ（３）：国内杉を原料とする針葉樹未晒クラフトパルプ（ＮＵＫＰ）。 [Raw material pulp]
Kraft pulp (1): Unbleached coniferous kraft pulp (NUKP) made from Douglas fir.
Kraft pulp (2): Unbleached coniferous kraft pulp (NUKP) made from domestic pine.
Kraft pulp (3): Unbleached coniferous kraft pulp (NUKP) made from domestic cedar.
［クラフト紙の製造］
　表１及び表２に記載した配合のパルプに、内添薬品として合成サイズ剤（荒川化学工業製、サイズパインＭＸＥ２）を、パルプの固形分に対して０．１５質量％添加した。その後、デラックスファイナーを用いて８０℃で叩解した。叩解後のパルプの特性を表１及び表２に示した。
　叩解後のパルプに、内添薬品として、硫酸バンドをパルプの固形分に対して１．２質量％、乾燥紙力増強剤としてカチオン化澱粉をパルプの固形分に対して０．９質量％およびポリアクリルアミドをパルプの固形分に対して１．０質量％添加した後、オープントップフォーマー式抄紙機を用いて抄紙（１層抄き）し、各例のクラフト紙を得た。各例のクラフト紙とその離解パルプの特性を表１及び表２に示した。 [Manufacturing of kraft paper]
A synthetic sizing agent (Size Pine MXE2, manufactured by Arakawa Chemical Industries, Ltd.) was added to the pulps having the formulations shown in Tables 1 and 2 as an internal chemical in an amount of 0.15% by mass based on the solid content of the pulp. Then, it was beaten at 80 ° C. using a deluxe finer. The characteristics of the pulp after beating are shown in Tables 1 and 2.
In the pulp after beating, as an internal chemical, a sulfuric acid band was added to 1.2% by mass based on the solid content of the pulp, and cationized starch was added to the pulp after beating as an internal preparation in an amount of 0.9% by mass based on the solid content of the pulp. After 1.0 mass% of polyacrylamide was added to the solid content of the pulp, paper was made (one layer) using an open top former paper machine to obtain kraft paper of each example. The characteristics of the kraft paper of each example and its disintegrated pulp are shown in Tables 1 and 2.
［評価］
　各例のクラフト紙の評価結果を表１及び表２に示す。表１及び表２に示すように、実施例のクラフト紙は透気抵抗度が低く、通気性に優れていた。また、実施例のクラフト紙で得られた袋は、充填性・破袋適性、落下衝撃特性が共に良好であり、優れた強度を有していた。さらに、実施例のクラフト紙は、糊付け適性も良好であった（接着性に優れ、加重時の他のクラフト紙への糊の浸透が抑制されていた）。 [Evaluation]
The evaluation results of the kraft paper of each example are shown in Tables 1 and 2. As shown in Tables 1 and 2, the kraft papers of Examples had low air permeation resistance and excellent air permeability. Further, the bag obtained from the kraft paper of the example had good filling property, bag breaking suitability, and drop impact characteristics, and had excellent strength. Further, the kraft paper of the example had good adhesiveness (excellent adhesiveness, and penetration of glue into other kraft papers under load was suppressed).
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002

Claims (8)

  1. 　クラフトパルプを主成分とするクラフト紙であって、
    　該クラフト紙をＪＩＳ　Ｐ　８２２０：２０１２に記載のパルプ離解法により離解した場合、得られる離解パルプのＪＩＳ　Ｐ　８１２１－２：２０１２に準拠して測定されるカナダ標準ろ水度は７００ｍＬ以上であり、ＪＩＳ　Ｐ　８１２０：１９９８に準拠して測定される繊維粗度は０．２００ｍｇ／ｍ以上である、クラフト紙。     Kraft paper whose main component is kraft pulp
    When the kraft paper is disintegrated by the pulp disintegration method described in JIS P 8220: 2012, the Canadian standard freeness measured in accordance with JIS P 8121-2: 2012 of the obtained disintegrated pulp is 700 mL or more. Kraft paper having a fiber roughness of 0.200 mg / m or more, measured in accordance with JIS P 8120: 1998.
  2. 　ＪＩＳ　Ｐ　８１２４：２０１１に準拠して測定される坪量が７０ｇ／ｍ２以上であり、
    　ＪＩＳ　Ｐ　８１４０：１９９８に準拠して測定される、温度２３℃、接触時間６０秒でのコッブ吸水度が１５～２８ｇ／ｍ２であり、
    　前記坪量に対する前記コッブ吸水度の比が０．１８～０．３５である、請求項１に記載のクラフト紙。     The basis weight measured in accordance with JIS P 8124: 2011 is 70 g / m 2 or more.
    Measured according to JIS P 8140: 1998, the Cobb water absorption at a temperature of 23 ° C. and a contact time of 60 seconds is 15 to 28 g / m 2 .
    The kraft paper according to claim 1, wherein the ratio of the water absorption of the cobb to the basis weight is 0.18 to 0.35.
  3. 　ＪＩＳ　Ｐ　８１１６：２０００に準拠して測定される縦方向の比引裂強さが１５．０ｍＮ・ｍ２／ｇ以上であり、横方向の比引裂強さが１８．０ｍＮ・ｍ２／ｇ以上である、請求項１又は２に記載のクラフト紙。 When the specific tear strength in the vertical direction measured in accordance with JIS P 8116: 2000 is 15.0 mN ・ m 2 / g or more and the specific tear strength in the horizontal direction is 18.0 mN ・ m 2 / g or more. The kraft paper according to claim 1 or 2.
  4. 　ＪＩＳ　Ｐ　８１１３：２００６に準拠して測定される縦方向の引張破断伸びが８．０％以上であり、横方向の引張破断伸びが６．０％以上である、請求項１～３のいずれか一項に記載のクラフト紙。 Any of claims 1 to 3, wherein the tensile elongation at break in the vertical direction measured in accordance with JIS P 8113: 2006 is 8.0% or more, and the tensile elongation at break in the lateral direction is 6.0% or more. The kraft paper described in item 1.
  5. 　ＪＩＳ　Ｐ　８１１３：２００６に準拠して測定される縦方向の比引張エネルギー吸収量が２．５Ｊ／ｇ以上であり、横方向の比引張エネルギー吸収量が２．３Ｊ／ｇ以上である、請求項１～４のいずれか一項に記載のクラフト紙。 Claims that the specific tensile energy absorption amount in the vertical direction measured in accordance with JIS P 8113: 2006 is 2.5 J / g or more, and the specific tensile energy absorption amount in the horizontal direction is 2.3 J / g or more. The kraft paper according to any one of 1 to 4.
  6. 　ＪＩＳ　Ｐ　８１１７：２００９に準拠して測定される透気抵抗度が１０秒以下である、請求項１～５のいずれか一項に記載のクラフト紙。 The kraft paper according to any one of claims 1 to 5, wherein the air permeability resistance measured in accordance with JIS P 8117: 2009 is 10 seconds or less.
  7. 　請求項１～６のいずれか一項に記載のクラフト紙で構成されたクラフト紙袋。 A kraft paper bag made of the kraft paper according to any one of claims 1 to 6.
  8. 　粉体収容用である請求項７に記載のクラフト紙袋。 The kraft paper bag according to claim 7, which is for storing powder.
PCT/JP2020/020052 2019-05-30 2020-05-21 Kraft paper and kraft paper sack WO2020241435A1 (en)

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JP2010229564A (en) * 2009-03-25 2010-10-14 Daio Paper Corp Kraft paper
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