Classifications

• • 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
• • 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
  • D21H11/14—Secondary fibres
• • 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
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes

Definitions

• the present invention relates to paperboard suitable for corrugated board, particularly corrugated board liners, box making, laminated interleaving paper, etc., and a method for manufacturing the same.
• Corrugated cardboard is manufactured by laminating liners on one or both sides of a corrugated core with a corrugator. Corrugated cardboard is used for packing various articles because it is lightweight and inexpensive. Corrugated cardboard may collide with the packaged material from the inside during transportation, or may be impacted from the outside during storage. Therefore, the corrugated board liner may be required to have a high burst strength so as not to be torn even if it receives an impact, depending on its use.
• the paperboard for which burst strength is required either virgin pulp, used paper pulp derived from 100% virgin pulp corrugated board, or a mixture thereof has been used as raw material pulp. The paperboard using such raw material pulp has high strength and is less likely to cause ruled line cracking (damaged line generated from the ruled line (shallow groove) given to the corrugated board base paper), and is suitable for a corrugated board liner.
• virgin pulp has a high raw material cost.
• recycled paper pulp derived from 100% virgin pulp corrugated cardboard is also expensive because it needs to be collected by a dedicated collection route so that other used paper (for example, corrugated cardboard using used paper pulp) is not mixed.
• the amount generated is also small. Therefore, when a paperboard containing a large amount of these pulps as a raw material pulp is used for corrugated board manufacturing, box making, and interleaving paper manufacturing, the cost is high.
• paperboard with a high blending ratio of used paper pulp has been proposed.
• the applicant proposes a paperboard in which the content of used paper pulp in the total pulp is 70% by mass or more, the basis weight is 350 g / m 2 or more, and the air permeation resistance is 25 seconds or more. (Patent Document 1).
• An object of the present invention is to provide a paperboard having excellent burst strength while blending used paper pulp.
• the means for solving the above problems are as follows. It has 1.3 or more paper layers and has Recycled paper pulp is contained in an amount of 40% by weight or more and 80% by weight or less, and kraft pulp is contained in an amount of 20% by weight or more and 60% by weight or less with respect to the total pulp contained in the entire paper layer.
• At least one of the surface layer and the back layer contains 60% by weight or more of kraft pulp with respect to the pulp contained in the one layer.
• 3. The surface layer, the back layer, or both contain used paper pulp. Or 2.
• the paperboard described in any of. 5. 1.
• the specific burst strength is 3.5 kPa ⁇ m 2 / g or more.
• the paperboard described in any of. 6. 1.
• the tensile strength is 7 kN / m or more in the vertical direction and 4 kN / m or more in the horizontal direction.
• the paperboard described in any of. 7. It is characterized in that the 120-second Cobb water absorption of both the surface layer surface and the back layer surface is 100 g / m 2 or less.
• the ratio (surface layer / back layer) of the 120-second cob water absorption of the surface layer surface to the 120-second cob water absorption of the back layer surface is within the range of 0.5 or more and 2.0 or less.
• the paperboard described in any of. It has 10.3 or more paper layers and has 10.3 layers or more. Recycled paper pulp is contained in an amount of 40% by weight or more and 80% by weight or less, and kraft pulp is contained in an amount of 20% by weight or more and 60% by weight or less with respect to the total pulp contained in the entire paper layer.
• the drainage level (CSF) of at least one layer of the middle layer pulp immediately after the mechanical treatment is 150 ml or more and 550 ml or less.
• a shaking device is used in the wire part. Or 11.
• the paperboard of the present invention contains 40% by weight or more of used paper pulp with respect to the total pulp, so that the cost is low.
• the paperboard of the present invention has excellent burst strength and tensile strength, and is not easily torn even when subjected to impact or the like.
• the paperboard of the present invention is not easily affected by moisture and moisture, and its strength does not decrease significantly depending on the usage environment.
• the paperboard of the present invention can be suitably used for corrugated board liners, medium-sized paperboards, paperboards for paper containers, paperboards for box making, paperboards for laminated interleaving papers, and the like.
• the paperboard of the present invention has three or more paper layers, and has three or more paper layers.
• Recycled paper pulp is contained in an amount of 40% by weight or more and 80% by weight or less
• kraft pulp is contained in an amount of 20% by weight or more and 60% by weight or less with respect to the total pulp contained in the entire paper layer.
• the surface layer and the back layer together are characterized by containing 80% by weight or more of the total kraft pulp contained in the entire paper layer.
• the paperboard of the present invention is composed of three or more paper layers, that is, a surface layer, one or more middle layers, and a back layer, and the front layer and the back layer are the outermost layers.
• the number of layers of the paperboard of the present invention is three or more, and can be appropriately set according to the basis weight.
• the back layer refers to a layer that is the lower surface in the flow direction of the paper at the time of paper making and is formed by first supplying the raw material to the wire part in the multi-layer paper machine, and is opposite to the front layer. It refers to the side, that is, the upper surface in the paper flow direction at the time of paper making, and the layer formed by finally supplying the raw material to the wire part in the multi-layer paper machine.
• the paperboard of the present invention contains 40% by weight or more and 80% by weight or less of used paper pulp with respect to the total pulp. Since the cost of the raw material pulp can be reduced by increasing the blending ratio of the recycled paper pulp, the blending ratio of the recycled paper pulp to the total pulp is preferably 50% by weight or more, preferably 60% by weight or more. Is more preferable.
• used paper pulp used paper pulp, high-quality paper, high-quality coated paper, medium-quality paper, medium-quality coated paper, shavings, etc.
• corrugated cardboard used paper pulp used paper pulp derived from corrugated cardboard
• Corrugated cardboard is mainly made of relatively long fiber pulp such as unbleached kraft pulp of coniferous trees, and liner and lignin are bonded with a starch-based adhesive, and the amount of printing is small. Compared to pulp, it tends to have a longer fiber length, a higher lignin content and a higher starch content, and a lower ink content.
• corrugated cardboard waste paper pulp is inexpensive because many countries have established recycling systems and the collection rate is high along with used newspaper and magazine waste paper.
• the blending ratio of the corrugated cardboard waste paper pulp with respect to the used paper pulp is preferably 80% by weight or more, more preferably 90% by weight or more, further preferably 95% by weight or more, and preferably 100% by weight. Most preferred.
• the paperboard of the present invention contains 20% by weight or more and 60% by weight or less of kraft pulp with respect to the total pulp, and the front layer and the back layer together contain 80% by weight or more of the total kraft pulp contained in the total paper layer.
• the burst strength of the paperboard can be increased by containing 20% by weight or more of kraft pulp with respect to the total pulp and concentrating 80% by weight or more of the total kraft pulp in the outermost layer.
• the blending ratio of kraft pulp to the total pulp is high, and the blending ratio of kraft pulp to the total pulp is preferably 22% by weight or more, preferably 24% by weight.
• the surface layer and the back layer together preferably contain 85% by weight or more, more preferably 90% by weight or more, and 95% by weight of the total kraft pulp contained in the entire paper layer. It is more preferable to contain% or more.
• kraft pulp one or more of bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), bleached hardwood kraft pulp (LBKP), and unbleached softwood kraft pulp (LUKP) are mixed. Can be used.
• softwood unbleached kraft pulp (NUKP) is preferable because it has a long fiber length and a large fiber diameter, which contributes to improvement in burst strength.
• the blending ratio of NUKP to the kraft pulp is preferably 80% by weight or more, more preferably 90% by weight or more, further preferably 95% by weight or more, and most preferably 100% by weight. ..
• the paperboard of the present invention contains 80% by weight or more of the total kraft pulp contained in the total paper layer in the surface layer and the back layer, but it is preferable that the surface layer contains kraft pulp, and both the surface layer and the back layer contain kraft pulp. It is more preferable to include it. Both the surface layer and the back layer can contain kraft pulp to increase the burst strength.
• the paperboard of the present invention preferably contains 60% by weight or more of kraft pulp in either or both of the surface layer pulp and the back layer pulp. The burst strength can be further increased by containing 60% by weight or more of kraft pulp in either or both of the surface layer pulp and the back layer pulp.
• the kraft pulp content is more preferably 80% by weight or more, further preferably 90% by weight or more, and most preferably 100% by weight.
• the paperboard of the present invention may contain recycled paper pulp, either or both of the surface layer pulp and the back layer pulp.
• the paperboard of the present invention is a pulp other than used paper pulp and kraft pulp, for example, crushed wood pulp (GP), refiner ground pulp (RGP), chemical pulp (CP), and thermostat, as long as the effect of the present invention is not impaired.
• GP crushed wood pulp
• RGP refiner ground pulp
• CP chemical pulp
• thermostat Various pulps derived from wood fibers such as mechanical pulp (TMP) and chemithermomechanical pulp (CTMP), and non-wood pulps obtained from Kenaf, Bagus, bamboo, hemp, wara and the like can be included. Further, the above-mentioned other pulp can be contained in the surface layer and the back layer as long as the effect of the present invention is not impaired.
• the paperboard of the present invention preferably has an average fiber length of 1.2 mm (1200 ⁇ m) or more and 2.0 mm (2000 ⁇ m) or less in either or both of the surface layer pulp and the back layer pulp. Keeping the average fiber length within the above range contributes to the improvement of burst strength.
• the average fiber length of either or both of the surface layer pulp and the back layer pulp is preferably 1.3 mm or more, and more preferably 1.4 mm or more.
• the upper limit is preferably 1.9 mm or less, and more preferably 1.8 mm or less. Further, it is preferable that both the surface layer pulp and the back layer pulp satisfy the above average fiber length.
• the average fiber length is a length-weighted average fiber length, and the fiber is observed using an image analysis device such as a fiber tester manufactured by ABB Co., Ltd. or a fractionator manufactured by Valmet Co., Ltd., an optical microscope, or an electron microscope. Can be measured by.
• the paperboard of the present invention contains used paper pulp in the middle layer.
• the blending ratio of the recycled paper pulp in the pulp for the middle layer is preferably 80% by weight or more, more preferably 90% by weight or more, further preferably 95% by weight or more, and preferably 100% by weight. Most preferred.
• the recycled paper pulp in the middle layer preferably has an average fiber length in the range of 0.7 mm (700 ⁇ m) or more and 1.6 mm (1600 ⁇ m) or less. By setting the average fiber length within the above range, the fiber content is evenly dispersed during papermaking with a paper machine, and a good formation is formed, which contributes to the improvement of burst strength.
• the average fiber length of the recycled paper pulp in the middle layer is preferably 0.8 mm or more, more preferably 0.9 mm or more.
• the upper limit is preferably 1.5 mm or less, more preferably 1.4 mm or less.
• the degree of drainage of the surface and back pulp immediately after mechanical treatment is higher than the degree of drainage of at least one of the middle layer pulp immediately after mechanical treatment (CSF). Large, specifically, 10 ml CSF or more is preferable, 30 ml CSF or more is more preferable, and 50 ml CSF or more is more preferable.
• CSF middle layer pulp immediately after mechanical treatment
• the pulp for the middle layer closest to the back layer satisfies the above-mentioned relationship of drainage degree, and the pulp for the middle layer closest to the back layer among the pulps for the middle layer has a drainage degree. It is more preferably 10 ml CSF or more smaller than the drainage degree of other middle-layer pulp, and further preferably 30 ml CSF or more smaller.
• the surface layer pulp preferably has a drainage degree (CSF) of 400 ml or more and 650 ml or less immediately after the mechanical treatment is completed.
• the lower limit is more preferably 420 ml or more, further preferably 440 ml or more.
• the upper limit is more preferably 600 ml or less, further preferably 550 ml or less.
• the back layer pulp preferably has a drainage degree (CSF) of 300 ml or more and 600 ml or less immediately after the mechanical treatment is completed.
• the lower limit is preferably 320 ml or more, more preferably 350 ml or more, still more preferably 370 ml or more.
• the upper limit is preferably 580 ml or less, more preferably 550 ml or less.
• the pulp for the middle layer has a drainage degree (CSF) of 150 ml or more and 550 ml or less immediately after the mechanical treatment is completed.
• CSF drainage degree
• the lower limit is preferably 200 ml or more, more preferably 250 ml or more.
• the upper limit is preferably 500 ml or less, more preferably 450 ml or less.
• the burst strength can be improved by beating the corrugated cardboard waste paper pulp to CSF of 150 ml or more and 550 ml or less.
• the middle layer pulp closest to the back layer has the lowest drainage degree immediately after the mechanical treatment is completed among the plurality of middle layer pulps.
• the average fiber length and drainage degree (CSF) of pulp can be adjusted by mechanical treatment.
• the method of mechanical treatment is not particularly limited, and examples thereof include beating, defibration, dispersion, and kneading, and beating is particularly preferable.
• the equipment used for mechanical processing is not limited, and examples thereof include types of equipment such as high-speed rotary type, colloidal mill type, high-pressure type, roll mill type, and ultrasonic type, such as refiner, beater, PFI mill, kneader, and disperser.
• a high-speed breaker, a conifer, a top finer, or the like, in which a metal or a cutting tool acts on a pulp fiber around a rotation axis, or a machine in which pulp fibers are rubbed against each other can be used.
• the mechanical treatment is preferably beaten using a discifier, a conifer, or a top finer.
• the concentration at the time of mechanical treatment is not particularly limited, and may be carried out under high concentration conditions where the solid content concentration is 15% by weight or more and 50% by weight or less, and is as low as 0.5% by weight or more and less than 15% by weight. It may be carried out under concentration conditions.
• the number of times of the mechanical treatment is not limited, and the mechanical treatment may be performed once or a plurality of times, and when the mechanical treatment is performed a plurality of times, different devices and solid content concentration conditions may be combined.
• conventionally used paper strength enhancers such as polyacrylamide (PAM) and modified starch can be added internally and / or externally as needed. , It is preferable to add it internally.
• the external paper strength enhancer is also referred to as a surface paper strength agent.
• the paper strength enhancer is preferably contained in an amount of 0.3% by weight or more, more preferably 0.4% by weight or more, based on the entire paperboard.
• the upper limit of the blending ratio of the paper strength enhancer is not particularly limited, but may be, for example, 1.5% by weight or less.
• a paper strength enhancer Even if a paper strength enhancer is added in an amount of more than 1.5% by weight, the effect is saturated and further paper strength enhancement can hardly be expected, resulting in high cost.
• a paper strength enhancer it is preferable to use polyacrylamide because it has a high paper strength enhancer effect.
• the polyacrylamide any of anionic, cationic and amphoteric can be used.
• the blending ratio of the paper strength enhancer in each paper layer of the paperboard of the present invention may be the same or different.
• the inner coating strength enhancer is blended in the surface layer and / or the back layer, and the blending ratio of the inner packing strength agent in the surface layer is the blending of the inner packing strength agent in another paper layer. It is more preferably less than or equal to the rate.
• the paperboard of the present invention can be supplemented with a sizing agent for preventing moisture absorption in order to improve the weather resistance of the paperboard.
• a sizing agent for preventing moisture absorption in order to improve the weather resistance of the paperboard.
• the sizing agent include rosin-based sizing agents, rosin emulsion-based sizing agents, ⁇ -carboxymethyl saturated fatty acids, etc., neutral rosin-based sizing agents, alkyl ketene dimer (AKD), alkenyl anhydride succinic acid (ASA), and the like.
• ASA alkenyl anhydride succinic acid
• examples thereof include cationic polymer-based sizing agents.
• internal chemicals such as aluminum sulfate band, aluminum chloride, sodium aluminate, basic aluminum compound, water-soluble aluminum compound, polyvalent metal compound, and silica sol can be added as long as the quality is not affected.
• the blending ratios of the sizing agent and the internal chemicals in each layer of the paperboard of the present invention may be the same or different.
• a known filler can be added as needed.
• the filler include kaolin, calcined kaolin, delaminated kaolin, clay, calcined clay, delaminated clay, illite, heavy calcium carbonate, light calcium carbonate, light calcium carbonate-silica complex, magnesium carbonate, barium carbonate. , Titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide and other inorganic fillers, and urea-formalin resin, polystyrene resin, phenolic resin and other organic fillers. And so on.
• the blending ratio of the filler in each paper layer of the paperboard of the present invention may be the same or different.
• the paperboard of the present invention may have a coating layer on the surface for the purpose of improving the strength of the paperboard, imparting printability, and the like.
• the coating layer may be a surface paper strength agent (external paper strength enhancer), a surface size agent, a water repellent agent, a pigment, a binder resin, an antislip agent, a preservative, an antifoaming agent, or a viscosity modifier.
• One kind of known surface treatment chemicals such as a rule-breaking inhibitor, or two or more kinds can be contained.
• the paperboard of the present invention preferably has a coating layer containing a surface paper strength agent from the viewpoint of improving strength.
• the surface paper force agent polyacrylamide-based, polyvinyl alcohol-based, oxidized starch, cationized starch, starch-based such as amphoteric starch, cellulose-based such as carboxymethyl cellulose and the like can be used, but polyacrylamide-based is preferable.
• a coating amount of the surface paper strength agent contained in the coating layer is preferably at 0.05 g / m 2 or more, 0.1 g / m 2 or more It is more preferable to have.
• it is preferable to have a coating layer containing a surface sizing agent and a water repellent agent for the purpose of improving weather resistance.
• the surface sizing agent include the same ones as those for internal use described above, and examples of the water repellent agent include a fluorine-based resin, a polyamide-based resin, and a wax emulsion.
• the paperboard of the present invention preferably has a basis weight of 70 g / m 2 or more, more preferably 100 g / m 2 or more, and further preferably 120 g / m 2 or more.
• the upper limit of the basis weight is not particularly limited as long as it can be manufactured by the paper machine, but it is preferably 350 g / m 2 or less, more preferably 320 g / m 2 or less, and 300 g / m 2 or less. Is even more preferable.
• the ratio of the basis weight of the surface layer to the total basis weight of the entire paper layer is preferably 20% by weight or more and 35% by weight or less, more preferably 22% by weight or more and 32% by weight or less, and 24% by weight or more and 30. More preferably, it is by weight% or less.
• the ratio of the basis weight of the back layer to the total basis weight of the entire paper layer is preferably 25% by weight or more and 55% by weight or less, and more preferably 30% by weight or more and 50% by weight or less from the viewpoint of burst strength.
• the paperboard of the present invention preferably has a specific burst strength (value obtained by dividing the burst strength by the basis weight) specified in JIS P8131: 2009 of 3.5 kPa ⁇ m 2 / g or more. Paperboard having a specific burst strength of 3.5 kPa ⁇ m 2 / g or more is more suitable for corrugated board liners because it is not easily torn by impact.
• the ratio burst strength is more preferably 3.6kPa ⁇ m 2 / g or more, still more preferably 3.8kPa ⁇ m 2 / g or more, is 4.0kPa ⁇ m 2 / g or more Is the most preferable.
• the paperboard of the present invention preferably has a tensile strength specified in JIS P8113 of 7.0 kN / m or more in the vertical direction (MD direction) and 4.0 kN / m or more in the horizontal direction (CD direction).
• a tensile strength specified in JIS P8113 of 7.0 kN / m or more in the vertical direction (MD direction) and 4.0 kN / m or more in the horizontal direction (CD direction).
• the tensile strength is more preferably 9.0 kN / m or more in the vertical direction, and further preferably 11.0 kN / m or more.
• the lateral width is more preferably 4.5 kN / m or more, and further preferably 5.0 kN / m or more.
• 120 seconds Cobb water absorption of the surface layer is preferably from 100 g / m 2 or less as specified in JIS P8140, more preferably not more than 90g / m 2, 80g / m 2 or less is more preferred.
• the water absorption of the back layer surface for 120 seconds is preferably 100 g / m 2 or less, more preferably 90 g / m 2 or less, still more preferably 80 g / m 2 or less.
• the paperboard having a water absorption of 120 seconds on both sides of 100 g / m 2 or less is not easily affected by the usage environment such as moisture and humidity, and can maintain burst strength and tensile strength. More suitable for liners.
• the paperboard of the present invention has a small difference between the front and back sides of the Cobb water absorption.
• the ratio (surface layer surface / back layer surface) of the 120-second cob water absorption value of the surface layer surface to the 120-second cob water absorption value of the back layer surface is within the range of 0.50 or more and 2.00 or less. Is preferable.
• the ratio of the 120-second Cobb water absorption between the front layer surface and the back layer surface is out of the above range (that is, the difference between the front and back sides of the 120-second Cobb water absorption is large)
• the paperboard is liable to peel off between the paper layers due to moisture and moisture. Delamination may tend to reduce the paperboard strength, including burst strength.
• the ratio of the water absorption of the Cobb is more preferably 0.60 or more and 1.67 or less, and further preferably 0.70 or more and 1.43 or less.
• the paperboard of the present invention preferably has an air permeation resistance (Oken type testing machine method) specified in JIS P8117: 2009 for 150 seconds or more.
• an air permeation resistance (Oken type testing machine method) specified in JIS P8117: 2009 for 150 seconds or more.
• the air permeation resistance is more preferably 175 seconds or longer, and further preferably 200 seconds or longer.
• the paperboard of the present invention preferably has a specific compressive strength of 170 Nm 2 / g or more as defined in JIS P8126: 2005.
• the ratio compressive strength is more preferably 175N ⁇ m 2 / g or more, more preferably 180N ⁇ m 2 / g or more.
• the use of the paperboard of the present invention is not particularly limited, and for example, it can be suitably used for corrugated board liners, medium-sized paperboard, paperboard for paper containers, paperboard for box making, paperboard for laminated interleaving paper, and the like. Of these, corrugated board liners are particularly preferred.
• the paperboard according to the present invention has three or more layers of paper, but is a combination of a long net paper machine, a twin wire paper machine, a circular net paper machine, a gap former, a hybrid former (on-top former), and the like.
• a known manufacturing (papermaking) method or papermaking machine using a paper machine or the like can be selected.
• the pH at the time of papermaking may be any of an acidic region (acidic papermaking), a pseudo-neutral region (pseudo-neutral papermaking), a neutral region (neutral papermaking), and an alkaline region (alkaline papermaking). Later, an alkaline agent may be applied to the surface of the paper layer.
• the paperboard of the present invention has a different composition of raw material pulp and the like for each layer, a paper material corresponding to each layer is prepared and papermaking is performed.
• the drainage degree (CSF) immediately after the mechanical treatment of the surface layer pulp and the back layer pulp is the drainage degree (CSF) immediately after the mechanical treatment of at least one layer of the middle layer pulp. Larger is preferred.
• the shaking device is a device that slides the breast roll of the wire part in the direction perpendicular to the flow direction of the paper material (also referred to as the machine width direction).
• the basis weight is made uniform (the formation is improved), so that the thin parts are reduced as compared with other parts which are the starting points of fracture, and the burst strength is improved.
• the strength of the paperboard can be improved by adjusting the papermaking conditions of each layer.
• the jet liquid is pulled by the wire and the pulp can be oriented in the papermaking direction (flow direction).
• the paperboard in which the pulp is oriented in the vertical direction (longitudinal direction) tends to have an improved specific burst strength.
• the J / W ratio is preferably 81% or more and 99% or less, and more preferably 84% or more and 98% or less.
• each layer is changed to increase the basis weight of the surface layer and / or the back layer, and the paper strength enhancer compounding ratio of each layer is adjusted to blend the paper strength enhancer into the surface layer and / or the back layer.
• the strength can be improved by increasing the number of layers in the middle layer or the like.
• the manufacturing (paper making) method and the paper making machine after the wire part are not particularly limited as long as the required strength and production efficiency of the paperboard are not impaired, and those used in a normal paper making machine can be used.
• the types of presses in the press part process of paper machines include, for example, straight-through presses, reverse presses, invar presses, twin bar presses, pickup presses, unipres, trinip presses, tiger event presses, shoe presses, mini shoe presses, etc.
• a known press device can be used, but not limited to.
• the pressing conditions are not particularly limited and can be appropriately set within the normal operating range, but the longer the pressing time, the easier it is for the fibers to bond with hydrogen and the strength of the paperboard is improved, which impairs the production efficiency. It is preferable to make low-speed papermaking within a range that does not exist.
• the type of dryer (drying device) in the dry part process of the paper machine is not particularly limited as long as it does not impair the production efficiency and the strength of the paperboard, and the hot air drying method used in a normal paper machine is not particularly limited.
• a known drying device such as a multi-cylinder cylinder drying method can be used, and the number of drying devices to be installed may be one, or two or more of a pre-dryer and an after-dryer may be installed. Further, the drying conditions are not particularly limited and can be appropriately set within a normal operating range.
• a coating liquid containing a surface treatment chemical such as a surface paper strength agent, a surface sizing agent, and a water repellent agent is applied.
• the method of applying the coating liquid is not particularly limited, and known devices such as a two-roll size press, a gate roll coater, a shim sizer, and a spray can be appropriately used.
• the calendar may be bypassed or processed within normal operating range.
• Example 1 The pulp used for each layer is shown below.
• a double conifer was used for the surface layer, and a double disc refiner was used for the middle layer and the back layer.
• the degree of drainage (CSF) at the outlets of the double conifier and the double disc refiner is shown as the degree of drainage (CSF) immediately after the mechanical treatment.
• Back layer 70% by weight of recycled corrugated paper pulp and 30% by weight of unbleached kraft pulp of softwood
• Middle layer 100% by weight of used corrugated paper pulp CSF 330 ml (back middle layer), 350 ml (front middle layer)
• Surface 100% by weight of unbleached kraft pulp CSF 500ml
• the internal paper force enhancer is 1.0% by weight based on the solid content for all layers, and the internal sizing agent (rosin type) is 0.45% by weight based on the solid content for the surface layer and the back layer.
• the paper material added so as to be in the order of the back layer (40% by weight), the middle layer (35% by weight in total), and the surface layer (25% by weight) in this order is a multi-layer paper machine so as to have a total of 150 g / m 2.
• Paperboard Papermaking machines were used to make paperboards, and a surface paper strength agent (PAM, external paper strength enhancer) was applied to the surface layer side at 0.1 g / m 2 in terms of solid content to obtain paperboard.
• This paperboard contains 63% by weight of used paper pulp and 37% by weight of kraft pulp with respect to the total pulp contained in the entire paper layer, and the front layer and the back layer contain all kraft pulp.
• the J / W ratios of the surface layer, the middle layer 2 layers, and the back layer were all set to 90%, and in the wire part, the shaking device was operated at the time of back layer papermaking.
• Back layer 85% by weight of recycled corrugated paper pulp and 15% by weight of unbleached kraft pulp of softwood CSF 540 ml
• Middle layer 100% by weight of used corrugated paper pulp CSF 350 ml (back middle layer), 460 ml (front middle layer)
• Surface 100% by weight of unbleached kraft pulp CSF 500ml
• Back layer 100% by weight of used corrugated paper pulp CSF 390 ml
• Middle layer 100% by weight of used corrugated paper pulp CSF 330 ml (back middle layer), 380 ml (front middle layer)
• Surface 100% by weight of unbleached kraft pulp CSF 500ml
• Back layer 85% by weight of recycled corrugated paper pulp and 15% by weight of unbleached kraft pulp of softwood CSF 390 ml
• Middle layer 100% by weight of used corrugated paper pulp CSF 330 ml (back middle layer), 380 ml (front middle layer)
• Surface 100% by weight of unbleached kraft pulp CSF 500ml
• Example 3 The amount of other chemicals used, the weight ratio of the paper layer, and the operating conditions were the same as in Example 3, and paperboard was obtained by using a multi-layer paperboard machine to make a total of 160 g / m 2.
• This paperboard contains 68% by weight of used paper pulp and 32% by weight of kraft pulp with respect to the total pulp contained in the entire paper layer, and the front layer and the back layer contain all kraft pulp.
• Example 5 The pulp composition, the amount of chemicals added, and the operating conditions were the same as in Example 4, except that the internal paper force enhancer (PAM) was added so that the solid content was 0.85% by weight in all layers, and the total was A paperboard was obtained by laminating together using a multi-layer paperboard machine so as to have a concentration of 160 g / m 2.
• PAM internal paper force enhancer
• Example 6 The pulp composition, the amount of chemicals added, and the operating conditions were the same as in Example 4, except that the internal paperboard force enhancer (PAM) was added so that the solid content was 0.9% by weight in all layers, and the total was A paperboard was obtained by laminating together using a multi-layer paperboard machine so as to have a concentration of 160 g / m 2.
• PAM internal paperboard force enhancer
• Example 7 The pulp composition, the amount of chemicals added, and the operating conditions were the same as in Example 4, except that the internal paper force enhancer (PAM) was added so that the solid content was 0.5% by weight in all layers, and the total was After making together using a multi-layer paperboard machine so as to be 160 g / m 2, a paperboard was obtained.
• PAM internal paper force enhancer
• Example 8 The pulp used for each layer is shown below.
• Back layer 70% by weight of recycled corrugated paper pulp and 30% by weight of unbleached kraft pulp of softwood CSF 390 ml
• Middle layer 100% by weight of used corrugated paper pulp CSF 330 ml (back middle layer), 380 ml (front middle layer)
• Surface 100% by weight of unbleached kraft pulp CSF 500ml
• This paperboard contains 63% by weight of used paper pulp and 37% by weight of kraft pulp with respect to the total pulp contained in the entire paper layer, and the front layer and the back layer contain all kraft pulp.
• the J / W ratio of the surface layer is 90%
• the J / W ratio of the middle two layers is 97%
• the J / W ratio of the back layer is 97.5%
• a shaking device is used when making the back layer. Activated.
• the internal paper strength enhancer is 0.1% by weight based on the solid content for all layers, and the internal sizing agent (rosin-based) is 0.5% by weight based on the solid content for the surface layer.
• the paper material added to the back layer (40% by weight), the middle layer is 2 layers (40% by weight in total), and the surface layer (20% by weight) is added in this order to a total of 160 g / m 2.
• the paper was squeezed together using a machine to obtain a paperboard.
• This paperboard contains 82% by weight of used paper pulp and 18% by weight of kraft pulp with respect to the total pulp contained in the entire paper layer, and the front layer and the back layer contain all kraft pulp.
• the J / W ratio of the surface layer was 90%, the J / W ratio of the middle layer 2 layers and the back layer was 95%, and in the wire part, the shaking device was operated at the time of back layer papermaking.

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