JP5461801B2 - Multi-layer paperboard and cardboard sheet - Google Patents

Description

  The present invention relates to a corrugated cardboard sheet that is assembled into a corrugated cardboard case that is folded and used, for example, when collecting used paper on which confidential information or the like is described, and a multilayer used as an exterior, a core, or an interior It relates to paperboard. In particular, the present invention relates to a multilayer paperboard and a corrugated cardboard sheet which can be easily recycled as a used waste paper for each corrugated cardboard case without unpacking it while storing the collected confidential used paper.

  In the past, important documents such as important documents and confidential documents that were no longer needed at government offices, offices, etc. have been collected, and when discarding these documents, a large amount of documents are cut with a shredder, which is very time-consuming. . For this reason, many offices outsource the disposal of these documents to specialized processors.

  In this case, in order to immediately dissolve and incinerate the disposal documents carried by the delivery company to the disposal facility, both the disposal processor and the delivery company have prepared a complete information processing system, and information on the disposal documents is leaked. For example, various measures are taken such as preventing third parties from entering the transportation route of documents. As the packing container (container) at that time, a cardboard case, a cloth or a collection bag made of an opaque synthetic resin material is generally used. Then, the waste paper is melted and processed while being recycled, and the waste document is effectively reused. However, a collection bag made of a synthetic resin material is suitable for incineration, but it cannot be dissolved as it is. In the case of a cardboard case, it can be dissolved as it is, but the paper used in the case is manufactured with a cardboard sheet that is recycled from low-whiteness waste paper. It is processed as a raw material (WP), and confidential waste paper, which is a high quality waste paper, cannot be used effectively. Further, the disintegration property of a general corrugated cardboard sheet is worse than that of confidential waste paper, and there is a problem that fibers are damaged more than necessary. It is preferable that high-quality paper and PPC paper used for documents at offices are reused mainly for high-quality and medium-grade paper, as well as old flyer paper, white paper, and colored paper. .

  As an alternative to such a corrugated cardboard sheet, there is a white paperboard, but the processing suitability with a corrugator and the suitability for box making (cracking with a flap) are poor. In addition, using a large amount of bleached kraft pulp is wasteful from the viewpoint of economy and is not suitable from the viewpoint of effective use of resources.

Therefore, it is conceivable to use various types of paper as shown below as the base paper of the container when transporting used paper such as confidential used paper.
First, Patent Document 1 discloses a coated white ball in which a lot of used paper that is not subjected to deinking treatment is mixed in the back layer and a pigment is applied on the back surface. This white ball is said to have improved ink color development at the time of backside printing, excellent printability for surface printing, and excellent resistance to cracking of ruled lines. However, according to this coated white ball, a lot of used paper that does not undergo deinking treatment is blended in the back layer, so even if there is no problem in printing suitability, a corrugated cardboard case using these as base paper is used as a used paper raw material. When used, the back layer contains a lot of waste paper that does not undergo deinking treatment, so the whiteness of the recycled pulp is low, and the waste paper material used for high and medium grades is low white. There is a problem of dust, dust, etc., which becomes a factor of deteriorating the quality, and the corrugated cardboard case composed of such coated white balls and the collected confidential used paper cannot be processed at the same time.

  Patent Document 2 discloses a method for producing a paperboard having excellent resistance to ruled line cracking by adding a predetermined amphoteric surfactant to a pulp slurry. However, the paperboard produced by this production method has a problem that it is inferior in terms of tensile strength and compressive strength although it is excellent in resistance to ruled line cracking. There is a problem that the cardboard case made by using the paperboard manufactured by the manufacturing method of Patent Document 2 does not satisfy the strength as a corrugated cardboard case for collecting confidential used paper.

  Further, Patent Document 3 discloses a low-density coated paperboard having a predetermined range of density, print surface roughness, air permeability, and the like. This paperboard is said to be excellent in gravure printing suitability and ruled line cracking suitability. However, according to this paperboard, since it has a pigment coating layer in which latex is blended in the surface layer, in the case of a severe case of a corrugated cardboard structure, there is a problem that ruled cracks are likely to occur at the flap portion. Even when recycled as waste paper pulp, there is a problem that the coating layer portion is difficult to melt.

  Further, Patent Document 4 discloses a corrugated cardboard sheet in which at least one liner is stretched paper. According to this corrugated cardboard sheet, it is said that ruled line breakage can be prevented. However, this corrugated cardboard sheet is suitable for resistance to crease cracking because of its elongation, but the corrugated cardboard case for collecting recovered used paper requires compressive strength, so there is a problem that it is inferior in strength. I have it.

In the first place, Patent Documents 1 to 4 described above have not studied disaggregation for the purpose of reuse when assembled in a storage container. In addition, there is a high possibility that waste paper pulp with high whiteness will be obtained from used paper such as confidential documents that are high-quality waste paper, so that when the storage container is melted, the storage container does not cause a decrease in whiteness. Is desired. However, in Patent Documents 1 to 4, even if there is a reference to whiteness, it is from the viewpoint of printability and not from the viewpoint of reuse. In addition, the paperboards described in the literatures 1 to 4 are used for exterior and interior applications as cardboard cases, and when used as a core, stepping occurs in the bonding and box making process. Have problems such as.
JP 2000-192395 A Japanese Patent Laid-Open No. 2001-262496 JP 2002-105895 A JP 2001-105516 A

  The main problem to be solved by the present invention is to maintain confidentiality as a confidential waste paper collection container, so that it is easy to dismantle during the dissolution process even in an unpacked state while containing the confidential waste paper, Using this multilayer paperboard, the corrugated cardboard case made can maintain sufficient strength as a collection container, providing multilayer paperboard and corrugated sheet with excellent resistance to crease crease and printability. To provide a corrugated cardboard sheet that can be configured as a multilayer paperboard as an exterior, a core, and an interior, and that can be used for high-quality wastepaper while collecting and storing the top confidential wastepaper. is there. This multilayer paperboard is also to provide a combination paper that can be used for exterior, core and interior.

The present invention that has solved this problem is as follows.
[Invention of Claim 1]
Multilayer having at least a surface layer and a back surface layer used as at least one of an exterior, a core, and an interior of a corrugated cardboard sheet which is subjected to pasting and boxing processing and constitutes a corrugated cardboard case for collecting and storing used paper Paperboard,
The fiber blending ratio of the mechanical pulp determined by the discriminating method using C dyeing solution in accordance with the JIS P 8120 (1998) paper, the paperboard and the pulp-fiber composition test method of the multilayer paperboard is 3 to 30% by mass. Yes, the whiteness of the handmade paper prepared by adjusting the pulp obtained by disaggregating the multilayer paperboard by a method according to JIS P 8220 (1998) by a method according to JIS P 8222 (1998) is 75% or more, The basis weight is 80 to 220 g / m ² .
Multi-layer paperboard characterized by that.

[Invention of Claim 2]
A coating liquid containing a water-soluble resin is applied to at least one surface, and the Denison wax value defined in JIS P 8129 (1997) is 13A or more.
The multilayer paperboard according to claim 1.

[Invention of Claim 3]
The water-soluble resin is a styrene resin,
The raw material pulp of the surface layer contains 5 to 50% by weight of softwood pulp,
The multilayer paperboard according to claim 2.

[Invention of Claim 4]
The raw material pulp contains 3 to 20% by mass of an inorganic pigment,
The paper density is 0.51 to 1.10 g / cm ³ .
The multilayer paperboard according to any one of claims 1 to 3.

[Invention of Claim 5]
All of the exterior, the core, and the interior are composed of the multilayer paperboard according to any one of claims 1 to 4.
A cardboard sheet characterized by that.

  According to the present invention, it is easy to disintegrate during the dissolution treatment, can maintain a sufficient strength as a collection container, is excellent in crease resistance and printability, and collects and stores the upper confidential waste paper, Multi-layer paperboard and corrugated cardboard sheets that can be used for high-quality waste paper and can be used for exterior, core, and interior.

Next, an embodiment of the present invention will be described.
The multilayer paperboard of this embodiment (hereinafter, also referred to as “multilayer paperboard”) is used as a raw material, for example, waste paper is treated such as deinking or bleaching and disaggregated by a method in accordance with JIS P 8220 (1998). The whiteness based on JIS P 8141 (2001) of hand-made paper prepared by adjusting the obtained pulp according to JIS P 8222 (1998) is 75% or more, preferably 80% or more, more preferably 85% or more. The pulp and / or kraft pulp has a fiber blending ratio of 3 in the mechanical pulp measured based on the paper, paperboard and the color table by the C dyeing method according to the pulp-fiber composition test method specified in JIS-P8120 (1998). ~ 30 mass%, preferably 10-30 mass% of raw material pulp is used, and the object of the present invention is achieved by making this raw material paper. If the whiteness is less than 75%, there is a problem that the appearance of the pulp blended with the high-quality / medium-quality paper is impaired.

  The thickness of the multilayer paperboard is lower than that of a multilayer paperboard made from a raw pulp made of conventional corrugated cardboard. Therefore, by making the mechanical pulp 3% or more, preferably 3% or more and 30% or less, and more preferably 10% or more and 25% or less, the compression strength required as a used paper container such as a confidential used paper collection box can be obtained. A corrugated cardboard case made of the present multilayered paper while recovering and storing confidential waste paper can be secured, and when recycled as a waste paper pulp as a corrugated cardboard case, water easily penetrates and is suitable for solubility.

  The multilayer paperboard is preferably formed by applying and drying a coating solution containing a water-soluble resin on at least one side, preferably on both sides. As a result, even if used pulp containing ash as a main component, like magazine waste paper, the surface strength can be set to 13A or more in terms of Denison wax value, and it is necessary for printing suitability, pasting suitability, and transportation of contents. The generation of ruled line cracks can be suppressed while maintaining a high tensile strength.

Basis weight, when used as a cardboard sheet, the exterior (liner), interior (liner) may preferably be 80g / m ² ~220g / m ² so that it can also used as a center core, a 120~180g / m ² More preferably. When it is less than 80 g / m ² , it becomes difficult to satisfy the strength as a container for collecting recovered used paper when used for the exterior or interior of a corrugated cardboard sheet. On the other hand, if it exceeds 220 g / m ² , there is a problem that the dissolution time is remarkably long when the dissolution process is performed to recycle the corrugated cardboard case as a confidential used paper collection container. In particular, the multilayer paperboard is particularly suitable for producing a corrugated cardboard sheet and a corrugated cardboard case having the same base paper for the exterior, interior, and core by setting the basis weight to 120 to 180 g / m ² .

  The multilayer paperboard is composed of, for example, a plurality of layers produced by a method such as combining 2 to 7 layers of wet paper. Therefore, it has at least a front surface layer and a back surface layer. The aforementioned coating liquid may be applied only to the front surface layer, or may be applied to the back surface layer.

  The surface layer is 20 to 95% by weight of pulp with a whiteness of 75% or more that has been deinked or bleached in the pulp material, 3 to 30% by weight of mechanical pulp, 2 to 92% by weight of kraft pulp bleached from hardwood, and softwood It is preferable that the pulp is blended in the range of 5 to 50% by weight.

  Since softwood pulp has the property of having a long fiber length and excellent tensile strength, by blending this, the effects of tensile strength, rupture strength, and crease resistance required as a container are recognized. The blending amount of the softwood pulp is preferably 10 to 50% by weight, and more preferably 30 to 50% by weight. When the blending amount of the softwood pulp is less than 5% by weight, there is a problem that ruled line cracking is likely to occur when the base paper configuration of the container is severe, and when it exceeds 50% by weight, it is advantageous from the viewpoint of strength. The problem of inferior printability arises.

  In addition, the multilayer paperboard may contain an inorganic pigment in an amount of 3 to 20% by weight, preferably 5 to 15% by weight, and more preferably 5 to 10% by weight. An effect such as bulkiness is recognized by blending the inorganic pigment.

Then, using a soft calender, calender overlaid several phases of metal roll such as a hard chilled mineral etc., to adjust the paper density ^{0.51g / cm 3 ~1.10g / cm 3} . If it is less than 0.51 g / cm ³ , the irregularities on the surface of the coating layer formed by applying the coating liquid to the surface layer or the like become large, which causes printing blurring. On the other hand, when it exceeds 1.10 g / cm ³ , there is a problem that flexibility is lowered and ruled line cracking occurs.

  In the multilayer paperboard, the used waste paper material that can be used is not particularly limited. For example, examples include cuts, damaged paper, and widened waste paper that occurs in bookbinding / printing factories / cutting offices, etc., unprinted or printed waste paper such as white, white, medium white, white loss, etc. In addition, waste paper pulp obtained by deinking and bleaching these waste paper can be used as a raw material pulp. In addition, high quality paper, high quality coated paper, medium quality paper, medium quality coated paper, reprinted paper, lithographic, relief, intaglio printing, electrophotographic method, thermal method, thermal transfer method, pressure sensitive recording method, ink jet recording method, carbon Waste paper printed with paper, waste paper written with water-based, oil-based ink, pencil, etc., pulp (DIP) obtained by deinking waste paper such as newspaper waste paper, paper sludge, paper mill waste water scum, and the like can be used. In other words, the White Paper, Cream White, Ruled White, Card, White, Medium White, White Manila, Imitation, Color, Kent, White Art, Beverage Pack, Office Paper, Special Cutting, separate upper cutting, medium antique, Kent Manila, newspaper, miscellaneous tea, cut tea, plain tea, miscellaneous tea, craft corrugated cardboard, corrugated cardboard, wamp, upper mount, mount, ball, etc. can be used. Among them, old white paper such as upper white, cream upper white, ruled white, card, special white, imitation, color, Kent, white art, beverage pack, office paper, etc., has high whiteness and is made of deinked pulp. The whiteness is preferred because it is easy to ensure 75% or more.

  In addition to virgin chemical pulp (hardwood bleached kraft pulp, softwood bleached kraft pulp, pulp obtained by chemically treating other fiber raw materials), wood or chips other than the above waste paper pulp, and mechanically soaked with chemicals The pulped chemiground pulp, chemimechanical pulp, and chips may be digested until they become slightly soft, and then virgin pulp such as semichemical pulp pulped with a refiner may be contained.

  In this multilayer paperboard, it is desirable that the coating solution applied to the surface layer or the like is coated with a water-soluble resin having good paper permeability and good film forming properties. The water-soluble resin can be applied by a transfer coating method such as a gate roll.

The coating amount is usually preferably 0.1 to 10 g / m ² . More preferably, 0.2 to 5.0 g / m ² is preferable. The multilayer paperboard preferably uses a water-soluble resin described in detail below, has excellent tensile strength, suppresses the occurrence of ruled line cracks, and can improve printability. When producing a corrugated cardboard case, the compressive strength as a corrugated cardboard case, the suitability for corrugating as a core base paper, and further, the cardboard case should have an appropriate dissolution and disaggregation property in the step of dissolving the cardboard case as it is. it can.

  As the water-soluble resin of the coating liquid to be applied to the present multilayer paperboard, styrene resin is preferably used, for example, “Polymalon 351S” manufactured by Arakawa Chemical Industries, Ltd. is preferably used. When a styrene-based resin is used, the water-based ink has good fillability, and the printability of flexographic printing and gravure printing is good and preferable. Styrenic resins are preferable in that they are resistant to heat and have excellent wear resistance on a hot plate in the process of bonding corrugated cardboard sheets.

  The styrene resin has a molecular weight of 20,000 to 100,000, preferably 50,000 to 100,000. When the molecular weight is less than 20,000, the viscosity of the resin decreases, and therefore, when coated, the raw material pulp is easily absorbed by the surface layer formed by papermaking, and the effect of styrene resin coating is difficult to obtain. . On the other hand, when the molecular weight exceeds 100,000, the viscosity becomes too high, leading to troubles such as coating unevenness.

  In this multilayer paperboard, SBR (styrene butadiene rubber) having a Tg (glass transition temperature) of −20 ° C. or more and 50 ° C. or less can be suitably used as a latex to be blended in the coating solution. If Tg is less than −20 ° C., the latex is soft at low temperatures and easily melts. Therefore, there is a possibility that stains may occur on the dryer, calender, etc. On the other hand, if it exceeds 50 ° C., it is formed on the surface such as the surface layer. The coating layer becomes hard, cushioning properties are lost, and printability is deteriorated. Examples of the SBR latex include trade name PA5036: manufactured by Japan A & L Co., Ltd. (Tg = 1 ° C.), and trade name JSR0589: manufactured by Japan JSR Corporation (Tg = 0 ° C.).

By using such a Tg-20 to 50 ° C. latex and a styrene-based resin, printability and ruled line cracking can be prevented even at a coating amount as small as 0.5 to 2.0 g / m ^2. it can.

  Moreover, it is preferable that the coating liquid of this form contains an organic pigment. As the organic pigment, true sphere or hollow PP (plastic pigment) has an effect of preventing unevenness on the surface of the multilayer paperboard, is softer than the inorganic pigment, and solves the problem of cracking of the coating layer.

  The particle diameter of the organic pigment is preferably 2 μm or more and 15 μm or less. When the particle diameter of the organic pigment is less than 2 μm, the thickness of the coating layer becomes too thin when the multilayer paperboard coated with the coating solution is calendered, and the cushioning property of the coating layer is reduced. This may cause printing blur during flexographic printing and gravure printing. On the other hand, if the particle diameter exceeds 15 μm, the coating layer becomes thick, and the coating layer is not easily crushed and cannot be flattened when calendered.

As described above, when the coating solution contains an organic pigment, when the coating amount is less than 0.1 g / m ² , the thickness of the coating layer is reduced when the multilayer paperboard is used for exterior and interior. Since the ink tends to be absorbed by the surface layer and the like, the print gloss is lowered. Further, when the present multilayer paperboard is used as a core, the frictional resistance of the surface is increased, and in the processing of the corrugated cardboard sheet, the suitability for stepping deteriorates and stepping is likely to occur. On the other hand, when the coating amount exceeds 0.8 g / m ² , when this multilayer paperboard is used as an exterior, the ink is not absorbed at all by the surface layer and the adhesive strength of the ink is lowered. In addition, since the water absorbability tends to deteriorate, the dissolution rate is remarkably deteriorated when the cardboard case using the multilayer paperboard is melted, resulting in a problem that the melt treatment efficiency is lowered. . Therefore, while using this multi-layer paperboard as an exterior, interior, and core paper, it has sufficient strength as a corrugated cardboard case, and it can be unpacked using a corrugated cardboard case as a container for confidential used paper. Thus, the present multilayer paperboard can be provided which can be efficiently dissolved as it is.

  In addition, by adding starch as a water-soluble resin to the coating liquid of this embodiment, the tensile strength is excellent, the occurrence of ruled line cracking can be suppressed, and the printability can be improved. When manufacturing a sheet and a cardboard case, the cardboard case can have a compressive strength, suitability for corrugating as a core base paper, and appropriate dissolution and disintegration in the step of dissolving the cardboard case as it is. .

  As the starch blended in the present coating solution, a modified starch having a molecular weight of less than 3 million, preferably from 2.3 million to 2.9 million is suitable. The form in which the starch is provided to the paper manufacturer is a solid material, and generally the higher the starch molecular weight, the slower the solid starch dissolves in the aqueous system. In addition, starch having a particularly high molecular weight exhibits a very high sensitivity to shearing, which causes a problem that handling and quality control become difficult. Therefore, when starch is used, it is necessary to dissolve the starch in an aqueous solution in advance. However, if the starch has a molecular weight of 3 million or more, it is necessary to perform strong mixing in order to ensure complete dissolution. There is. However, when such a strong mixing operation is performed, the high molecular weight starch exhibits high sensitivity to shearing, so that high molecular weight characteristics cannot be obtained. In the finally obtained starch dispersion, The starch cannot be uniformly dispersed. For this reason, the starch used for this multilayer paperboard has a molecular weight of less than 3 million. However, even if the molecular weight of the starch is less than 3 million, if the molecular weight is too low, even if it is applied to the front and back surfaces of the base paper including at least the front surface layer and the back surface layer, the viscosity is low and the film thickness is poor. For this reason, it does not stop on the surface of the base paper, and it becomes easy to penetrate into the paper, so that the surface strength tends to be inferior. Therefore, it is more preferable to use starch having a molecular weight of 2.3 million or more.

  Examples of such starch include various known ones such as oxidized starch, cationized starch, carboxymethylated starch, pregelatinized starch, phosphate esterified starch, urea phosphate-modified starch, and unmodified starch. Or 2 or more types can be mixed and used. In addition, since these starch raw materials are not particularly limited, for example, various known raw material starches such as tapioca starch, potato starch, sweet potato starch, wheat starch, sago starch, rice starch, and corn starch are used alone. Or 2 or more types can be mixed and used.

  Among these starches, it is preferable to use phosphoric acid-modified starch, particularly phosphate esterified starch and / or urea phosphoric acid-modified starch. In the case of phosphoric acid esterified starch, it is preferable to use phosphoric acid-modified starch in which the binding rate of phosphoric acid is 0.1 to 10% by weight as phosphoric acid H3PO4 per solid content of phosphoric acid esterified starch. . Phosphoric acid-modified starch has a low increase in viscosity even at a high concentration, and is excellent in coatability. In addition, since it has moderate permeability into the base paper, it must have adequate water permeability while maintaining the tensile strength, bonding suitability, and printability required for corrugated cardboard sheets and cardboard cases. Can do.

The starch used in the multilayer paperboard is a value analyzed by colorimetric determination of starch by the phenol-sulfuric acid method, and the starch is 2.5 to 10 g / m ² in the base paper, preferably 3.0. It is preferable to apply the coating on the front and back surfaces of the base paper with a coating facility so as to contain ˜5 g / m ² . Thus, the multilayer paperboard is made so that the basis weight is 80 to 220 g / m ² , particularly 120 to 180 g / m ² , and the density is 0.50 to 0.70 g / cm ^3. This multi-layer paperboard can be used as a core base paper while maintaining the tensile strength, bonding suitability, and printability required for exterior base paper and interior base paper as corrugated cardboard cases. Can be used for all base paper configurations, exteriors, interiors, and cores in corrugated cardboard sheets and cardboard cases.

The starch content in the base paper is such that the starch has a coating solution concentration of 35% or more and a viscosity at a temperature of 40 ° C. of 85 cp or less, preferably 10 to 80 cp, more preferably 30 to 75 cp. It becomes easier to apply so that the amount is 2.5 g / m ² or more. Thereby, while maintaining the tensile strength, bonding suitability, and printing suitability required for the exterior base paper, interior base paper as a corrugated cardboard sheet or corrugated cardboard case, it can have the ability to be processed as a core base paper, It is possible to provide the multilayer paperboard that can be used for all base paper configurations, exteriors, interiors, and cores in corrugated sheets and corrugated cardboard cases using the multilayer paperboard.

In addition, in this multilayer paperboard for exterior and interior use, if the starch content is less than 2.5 g / m ² , the compressive strength, bonding suitability, and printability required for corrugated cardboard sheets and cardboard cases are maintained. However, it becomes difficult to improve bonding and boxing suitability. On the other hand, when the starch content exceeds 10 g / m ² , the coating layer becomes hard, the ruled line cracking resistance is inferior, and the water permeability deteriorates, so that the solution treatment efficiency tends to deteriorate.

  In addition to the water-soluble resin, polyvinyl alcohol (PVA), polyacrylamide (PAM), and the like can be used as the coating liquid within a range that does not affect the effects of the present invention. Further, for example, a lubricant, a sizing agent, a filler dispersant, a pH adjuster, a thickener, a fluidity improver, an antifoaming agent, an antifoaming agent, a release agent, a penetrating agent, a coloring dye, a coloring pigment, an ultraviolet absorber, Various known additives such as antioxidants, antiseptics, antibacterial agents, water-proofing agents, and fluorescent quenchers may be added alone or in admixture of two or more.

  However, as the coating amount increases and the starch content in the surface layer and the like increases, the flexibility tends to decrease and the paper becomes stiff. It tends to get worse. There is also a problem that the generation of paper dust increases. Therefore, it is preferable to apply a non-wax lubricant on the coating layer.

  As the lubricant, those mainly composed of fluororesin (solid, powder, fibrous, etc.) are used. In addition, liquid type lubricants can be used in combination with silicone oil, synthetic oil such as fluorine oil, animal oil such as squalane oil, vegetable oil such as rapeseed oil, safflower oil, sesame oil, coconut oil, mineral oil, etc. Any means for obtaining lubricity is effective, but in view of long-term stability, it is desirable to use a synthetic oil such as silicone oil or fluorine-based oil. Silicone oils include methylphenyl oil, fluorosilicone oil, dimethyl silicone oil, modified silicone oils such as polyether, fluorine, epoxy, and alcohol. Although there are some differences in effect, they can be used almost as a lubricant. . Examples of the fluorine-based oil include fluorocarbon oil and perfluoroether oil.

Moreover, a higher fatty acid metal salt such as calcium stearate and an aqueous dispersion of low molecular weight polyethylene can be preferably used. Among these, liquid hydrocarbon oils, higher fatty acids, higher alcohols, higher fatty acid sulfated oils, aliphatic phosphate esters, polyalkylene glycols or derivatives thereof, aqueous dispersions thereof, paraffin wax, microcrystalline wax, etc. Oil wax or the like can be used. However, petroleum wax has a low effect of suppressing the generation (dust generation) of paper dust, so that the basis weight is 80 to 220 g / m ² , particularly 120 to 180 g / m ² , and it is used for exteriors, interiors, and cores. In the present multilayer paperboard having the same weight as the base paper, it is particularly preferable to use a non-wax-based lubricant. By applying the above-mentioned lubricant and water-soluble resin to at least one side of the multilayer paper, the multilayer paperboard can be used as a base paper for the exterior, interior, and core of the cardboard case. Can do.

  This multi-layer paperboard is a coating liquid containing the above-mentioned water-soluble resin in a film transfer type coating equipment in which wet paper is formed in a headbox equipped with a mechanism capable of adjusting the concentration of raw pulp in the width direction. Can be applied to the front and back surfaces of wet paper and dried.

  In high-speed papermaking at 700 m / min or higher, the coating solution is preferably applied to the base paper at a concentration of 1.0 to 2.5%. When the concentration is less than 1.0%, mist is generated particularly in the gate roll, and the surrounding facilities may be soiled. In addition, it is difficult to apply a necessary amount of coating liquid, and an excessive drying capacity is required, resulting in a problem that the operability is lowered. On the other hand, if the concentration exceeds 2.5%, the viscosity becomes high, so that the paper is taken off during coating, paper breakage occurs, and a running trouble occurs, resulting in a problem of reduced operability.

  Further, when the multilayer paperboard is used as an exterior or interior of a corrugated cardboard sheet, the JAPAN TAPPI No. in disaggregated pulp disaggregated according to JIS-P8220. The weight average fiber length (hereinafter simply referred to as “weight average fiber length”) measured according to No. 52 is 1.20 to 1.50 mm, more preferably 1.30 to 1.40 mm. Thereby, irrespective of the compounding quantity of a used paper pulp, the tensile strength required for conveyance of contents, such as used paper, pasting suitability, and printing suitability can be kept constant. Moreover, since it can prevent that the amount of short fibers increases, generation | occurrence | production of paper dust can be suppressed. Furthermore, the paper thickness decrease in the subsequent head box and the press part is reduced, and it is possible to form a paper layer with a good formation, that is, with less uneven thickness.

  In the above, when the weight average fiber length is less than 1.20 mm, it is difficult to keep the tensile strength, the bonding suitability, and the printing suitability necessary for transporting the contents such as waste paper as short as possible. Since the amount of fibers increases, paper dust is likely to be generated. On the other hand, when the weight average fiber length exceeds 1.50 mm, the yield is lowered by the classification process in the manufacturing process, and problems occur in terms of resource saving and cost, and the formation is deteriorated.

Next, the manufacturing method of this multilayer paperboard is demonstrated, referring FIG. 1 (schematic diagram of an example of the implementation equipment which forms this multilayer paperboard).
In this equipment, paper stock is ejected from a head box 1 equipped with a mechanism capable of adjusting the concentration of raw material pulp in the width direction, and a paper layer is formed while dispersing pulp fibers in the wire part 2, and a shoe press 3 The wet paper is then dried by the pre-dryer part 5. Next, using the size press 6, the above-described coating solution is applied to the front and back surfaces of the wet paper. After application, in the after-dryer part 7, the wet paper having the coating liquid applied on the front and back surfaces is dried, subjected to a canreder process by the calendar device 8, wound by the winder 9, and the basis weight is 80 to 220 g / m ^2. In particular, the present multilayer paperboard can be used as a cardboard case having a basis weight of 120 to 180 g / m ² and can be used as a base paper for exterior, interior, and core.

  As a head box 1 equipped with a mechanism capable of adjusting the concentration of raw pulp in the width direction, a module jet head box (manufactured by VOITH), a concept IV-MH head box (manufactured by Mitsubishi Heavy Industries, Ltd.), Optiflow head A box (manufactured by METSO), a BTF-dilution system (manufactured by Kawanoe Kikai Co., Ltd.), or the like can be used.

  In addition, when the head box 1 is not provided with a mechanism capable of adjusting the concentration of the raw material pulp in the width direction, the thickness difference due to the formation of the paper in the wire part becomes large, and the shoe press of the press part 4 described later. 3 cannot correct this thickness difference.

  The press part 4 in the paper making process of the multilayer paperboard is provided with a shoe press 3. In other words, press part 4 is also required to have a higher dewatering capacity as the paper machine speeds up. For this reason, it is preferable to provide the shoe press 3 having more dewatering ability than the conventional two-roll nip method.

  Further, as a result of intensive studies by the inventor, by providing the shoe press 3, it is possible to perform dewatering while suppressing a decrease in paper thickness, in addition to having high dewatering capability compared to the case of having a 2-roll nip press. I understood.

Thus, by combining the head box 1 and the shoe press 3 described above, the basis weight is 80 to 220 g / m ² , and particularly the basis weight is 120 to 180 g / m ^2, and the exterior used for corrugated cardboard sheets and cardboard cases, A multilayer paperboard having bonding suitability, step feeding suitability, ruled line cracking suitability, and printing suitability that can also be used as a base paper for interiors and cores can be obtained.

  As such a shoe press 3, a Shimbelt S press (manufactured by METSO), Nipcoflex press (manufactured by VOITH), an extended nip press (manufactured by Mitsubishi Heavy Industries, Ltd.) or the like can be used. When the shoe press 3 is not used, even if the thickness difference of the paper can be reduced by the head box 1, the reduction in the paper thickness at the press becomes large. There is a possibility that the bonding suitability and the printing suitability cannot be maintained.

Thus, by using the head box 1 and the shoe press 3 in combination as described above, the paper thickness can be maintained and the decrease in the paper thickness can be reduced even when paper is made at a high speed of 800 m / min or more. , Thickness unevenness can be reduced. As a result, the multilayer paperboard for corrugated board sheets of the present invention can be obtained at a basis weight of 80 to 220 g / m ² , particularly 120 to 180 g / m ² .

  The wet paper of the present multilayer paperboard dried by the dryer part 5 is formed on the front and back surfaces of the wet paper of the present multilayer paperboard by the application equipment of the size press process after the wet paper is formed as described above. The applied coating solution is applied.

  As a method of coating the coating liquid on the front and back surfaces of the wet paper of the multilayer paperboard, a coating method such as a two-roll pound method, a film transfer method such as a gate roll size press or a rod metering size press is used. However, from the viewpoint that a uniform coating layer can be formed with a small coating amount, a gate roll size press is more preferable among the film transfer methods (transfer methods). In this way, by applying the coating liquid with the coating equipment using the film transfer method, the tensile strength, the bonding suitability, and the printing suitability necessary for transporting the contents such as waste paper can be improved.

It is preferable that the present multi-layer paperboard having the coating solution coated on both sides or one side thereof is not subjected to calendar treatment thereafter. As a result, the reduction in paper thickness due to pressing can be reduced, and the strength, bonding suitability, and printing suitability necessary for transporting contents such as waste paper can be maintained even with a low basis weight. Can do.
In other words, conventional paperboard for corrugated cardboard is subjected to calendering processing to improve printing suitability by reducing thick book unevenness, but the difference is not recognized by light printing at a low-grade level. In order to ensure the above, it is preferable not to perform calendar processing.

In addition, the multilayer paperboard formed as described above has a dusting paper dust amount (hereinafter referred to as 30-50 μm) in a vertical and horizontal cross section measured according to the Japanese translation of SEMI G97-0996 2001. It is simply referred to as “the amount of dusting paper dust” is 2000 pieces / m ³ or less, preferably 1200 to 1600 pieces / m ³ from the viewpoint of aesthetics and economy.

In the core base paper having a configuration similar to that of the multilayer paperboard, the dust generation paper dust amount exceeds 2000 / m ³ , and sometimes 3000 / m ³ or more. Thus, when the amount of dust generated paper dust exceeds 2000 / m ³ , paper dust is noticeable.

Note that the amount of dust-generating paper dust is 5 layers in the flow direction and 20 cm in the width direction, and 5 sheets of samples cut with a cutter are stacked, and the end face is separated 10 times in the glove box, and SEMI G67-0996 is used. In order, the amount of dust generated at the time of suction of 100 L (the number of generated paper dust) was measured with a particle counter and converted to 1 m ³ .

Further, when the basis weight is less than 140 g / m ² , the present multilayer paperboard has a tensile strength (longitudinal) of 3.0 kN / m or more and a compressive strength (lateral) of 95 N · m ² / g or more. When the amount is 140 g / m ² or more, the tensile strength (longitudinal) is 5.0 kN / m or more, and the compressive strength (horizontal) is 155 N · m ² / g or more. That is, the tensile strength is not less than 3.5 kN / m (breaking length: 3.0 km) defined by JIS-P3904, class C display rice basis weight of 120 g / m ² , and the compressive strength is 96 N · The target was m ² / g or more. As a result, when the basis weight is 80 to 220 g / m ² , particularly 120 to 180 g / m ² , in order to maintain confidentiality as a confidential waste paper collection container which is the subject of the present invention, Even in this state, it is easy to disintegrate during the dissolution process, and using this multi-layer paperboard, the cardboard case made can maintain sufficient strength as a collection container, and is suitable for folding resistance and printing. Providing multi-layer paperboard and corrugated cardboard sheets with excellent suitability, and also providing corrugated cardboard cases in which this multi-layer paperboard is configured as a base paper for the exterior, core, and interior, and recovering top confidential used paper Thus, it is possible to provide a corrugated cardboard case that can be used for high-quality waste paper while being stored.

This form of multi-layered paper making paperboard described above, for example, paper making the multilayer 180 g / m ² as a center core liner and 180 g / m ² as the multilayer paper making paperboard and interior liner 180 g / m ² as an exterior liner A cardboard sheet can be obtained by using paperboard. This corrugated cardboard sheet is a corrugated cardboard case which is a used paper container for storing used paper such as confidential used paper by bending. There is no particular limitation as to how the corrugated cardboard sheet is processed to obtain a corrugated cardboard case. For example, the corrugated cardboard sheet may be the same as a currently known corrugated cardboard case.

  In order to confirm the effect of the multilayer paperboard according to the present invention, the following various samples were prepared, and a test for evaluating the quality of each sample was performed. Note that the present embodiment does not limit the present invention, and it is needless to say that the configuration can be changed as appropriate without departing from the scope of the claims.

  Tables 1 and 2 show multilayer paperboards according to comparative examples for the purpose of making comparisons with these examples. It produced with such a structure. It should be noted that all the factors of each example and comparative example are not newly established individual lines, but are mainly test examples by a test plant.

[Example 1]
After blending NBKP 50% by weight, LBKP 25% by weight and mechanical pulp 25% by weight, the raw pulp is adjusted with a double disc refiner so that the Canadian standard freeness (according to JIS-P8121) is 400 cc. A slurry was prepared.

  Next, as the water-soluble resin, oxidized starch having a molecular weight of 2.9 million (SK-20 manufactured by Nippon Corn Starch Co., Ltd.) is used, and the concentration of the applied starch is adjusted to 2.0% to achieve the water-soluble resin. A coating solution was prepared.

  The raw material pulp slurry prepared as described above was put into a module jet head box (manufactured by VOITH) and the concentration was adjusted so that the concentration of the raw material pulp was 1.0% to form a single-layer wet paper. . Thereafter, the wet paper was dehydrated by a shoe press method and dried by a predryer. The paper making speed is 800 m / min.

Next, the above-mentioned water-soluble resin was applied to the front and back surfaces of the wet paper by a size press so that the starch content in the base paper was 2.7 g / m ^2, and dried, and the finished moisture was JIS- A multilayer having a range of 8.0 ± 1.5% defined by P3904, consisting of four layers, a basis weight of 100 g / m ² , a density of 0.57 g / cm ³ , and a paper thickness of 175 μm. Paperboard was obtained.

[Other Examples and Comparative Examples]
It produced and evaluated similarly to Example 1 except the conditions shown in Table 1 and Table 2. FIG. In addition, calcium stearate (Nopcoat C-104: manufactured by San Nopco Co., Ltd., solid content concentration 50%) was used as the lubricant, applied to an after drier with a sprayer, transferred and used.

  The “press system” in Table 2 is the format in the press part, and “S” in the table is a shoe press (wet paper transported by transport felt and press roll and press through an annular belt. “R” indicates a roll press (a mechanism for pressing in a gap formed between the rolls).

  In addition, “application type” in Table 2 indicates an application type when a water-soluble resin is applied to the front and back surfaces of a multilayer paperboard. “P” means a pound type (a method in which a liquid reservoir is provided between rolls and paper is applied), and “B” means a bill blade (a method in which paper is applied between a rubber-coated backing roll and a blade). "G" indicates a gate roll (a roll transfer coating method comprising six rolls).

  The “type of water-soluble resin” in Table 1 is the type of water-soluble resin applied to at least the surface layer of the multilayer paperboard, and “acid” in the table is “oxidized starch”. “Urine” means “urea phosphate-modified starch”, and “D” means “phosphate esterified starch”. “Styrene / latex” refers to trade name: Polymeral 351S (manufactured by Arakawa Chemical Industries, Ltd.). In this example, SK-20 manufactured by Nippon Corn Starch Co., Ltd. is used as the oxidized starch, and Starcoat # 16 manufactured by Nippon Food Chemical Co., Ltd. is used as the urea phosphated starch. SK-3000 manufactured by Nippon Corn Starch was used.

“Basis weight (g / m ² )” in Table 1 is the grammage of each sample all layers, that is, the entire multilayer paperboard for corrugated cardboard sheets, as described in JIS-P8124 “Paper and paperboard—basis weight”. It is a value measured in accordance with “Measuring method”.

“Density (g / cm ³ )” in Table 1 is a value calculated by measuring the basis weight and thickness of each sample. Moreover, in order to eliminate a measurement error, it is an average value obtained by measuring 10 samples from each sample. The thickness (μm) of each sample is a value measured based on JIS-P8118 (2006) “Paper and paperboard—Test method for thickness and density”.

Table 1 in the "coating weight (g / m ^2)" is the coating amount of starch as a main component of the water-soluble polymer (g / m ^2), the colorimetric analysis using the phenol-sulfuric acid method The value is determined using a calibration curve prepared with oxidized starch.

“Fiber length (mm)” in Table 1 is a weight average fiber length (mm), and after immersing about 25 g of a test piece cut to about 10 cm ² from each sample in 1 liter of water, The sample was disaggregated for 15 minutes using a TAPPI standard disaggregator, and the JAPAN TAPPI paper pulp test method No. 52 Value measured based on fiber length test method.

  Table 2 shows the results of quality evaluation for all of these Examples and Comparative Examples. This quality evaluation test was performed under environmental conditions of temperature 23 ± 2 ° C. and humidity 50 ± 2% in accordance with JIS-P8111.

  “Tensile strength longitudinal (kN / m)” in Table 2 is a value in the longitudinal direction measured according to JIS-P8113.

“Compressive strength lateral (N · m ² / g)” in Table 2 is a lateral value measured according to JIS-P8126.

  “Wax pick (A)” in Table 2 is a Denison wax value measured according to JIS-P8129 (1997).

“Dust generation amount (pieces / m ³ )” in Table 2 refers to SEMI G67-0996, the particle generation amount (number of generated paper dust) at the time of 100L suction is a particle counter (KONDA, manufactured by RION Co., Ltd.). -20 type), and the value converted to 1 m ³ .

  “Manufacturing cost” in Table 2 is based on the raw material cost, chemical use cost, and operation cost in Comparative Example 1, and the top five examples with the highest cost reduction ratio are ◎, the others are ○, and the cost is increased. What became became x.

“Adhesion suitability” in Table 2 is the result of evaluating the workability at the time of producing a corrugated cardboard case using the multilayer paperboard as the exterior, interior and core of the corrugated cardboard sheet.
(Double-circle): At the time of pasting, there was no jump, the exterior, interior, and the core could be pasted, and there was no sheet curvature.
○: Although stepping was recognized at the time of bonding, the sheet was generally good without warping.
Δ: Stepping occurred at the time of bonding, and the exterior, interior, and core could not be bonded.
X: At the time of bonding, stepping and step cracking occurred, and bonding could not be performed.

“Appropriate ruled line cracking resistance” in Table 2 was obtained by folding the corrugated cardboard case flap 180 ° using this multilayer paperboard and visually observing the top of the crease. The crack per 20 cm width was evaluated.
(Double-circle): The crack was not recognized.
A: Cracks with a width of less than 2 mm were less than 3 places.
Δ: There were three or more cracks with a width of less than 2 mm.
X: The crack exceeding 2 mm has generate | occur | produced continuously.

“Disaggregation” in Table 2 is solubility. Using this multi-layer paperboard, 2500 sheets of A4-sized used PPC used paper are packed in the cardboard case, and each cardboard case is used as it is. It melt | dissolved for 40 minutes, and the used paper pulp which melt | dissolved was confirmed visually.
A: Completely dissolved in 40 minutes. No undissolved material was observed.
○: Slightly undissolved pulp was observed.
Δ: Undissolved waste paper of 3 mm or more was observed.
X: There was clearly undissolved waste paper.

As can be seen from Table 2, the multilayer paperboard for corrugated cardboard sheets according to the present invention has a basis weight of 80 to 220 g / m ² , particularly 120 to 180 g / m ² , and is used for corrugated cardboard sheets. It can also be used as a core paper and maintains confidentiality as a confidential waste paper collection container, which is a problem.It is easy to disintegrate during the melting process even when unpacked with confidential waste paper stored. Using multilayer paperboard, the cardboard case made can maintain sufficient strength as a collection container, providing multilayer paperboard and corrugated sheet with excellent crease resistance and printability. We can provide corrugated cardboard sheets and corrugated cardboard cases made of paperboard as exterior, middle core, and interior base paper, and collect used confidential paper and store it as it is. That cardboard sheet, it is possible to provide a cardboard case.

  The multilayer paperboard of the present invention can also be used as a core base paper constituting a corrugated cardboard sheet, so that the corrugated cardboard sheet can be easily manufactured at a low cost with the same material. Although the manufacturing cost can be further reduced, the conventional commercially available front and back papers (paperboards) listed as comparative examples cannot be used as the core base paper, so they are different from the outer base paper, the core base paper, and the inner base paper. It is necessary to prepare varieties, which is complicated and increases the cost.

  The present invention relates to, for example, a corrugated cardboard sheet assembled into a corrugated cardboard case as a used paper container used when collecting used paper on which confidential information or the like is described, and a multilayer paperboard used as a liner or a core thereof As applicable. In addition, the recovered waste paper can be dissolved without being unpacked while being collected, and can be effectively recycled as used waste paper.

It is an example of the schematic diagram of the implementation equipment which forms the multilayer paperboard of this form.

  DESCRIPTION OF SYMBOLS 1 ... Head box, 2 ... Wire part, 3 ... Shoe press, 4 ... Press part, 5 ... Pre dryer part, 6 ... Size press, 7 ... After dryer part, 8 ... Calendar apparatus, 9 ... Winding machine.

Claims (5)

Multilayer having at least a surface layer and a back surface layer used as at least one of an exterior, a core, and an interior of a corrugated cardboard sheet which is subjected to pasting and boxing processing and constitutes a corrugated cardboard case for collecting and storing used paper Paperboard,
The fiber blending ratio of the mechanical pulp determined by the discriminating method using C dyeing solution in accordance with the JIS P 8120 (1998) paper, the paperboard and the pulp-fiber composition test method of the multilayer paperboard is 3 to 30% by mass. Yes, the whiteness of the handmade paper prepared by adjusting the pulp obtained by disaggregating the multilayer paperboard by a method according to JIS P 8220 (1998) by a method according to JIS P 8222 (1998) is 75% or more, The basis weight is 80 to 220 g / m ² .
Multi-layer paperboard characterized by that. A coating liquid containing a water-soluble resin is applied to at least one surface, and the Denison wax value defined in JIS P 8129 (1997) is 13A or more.
The multilayer paperboard according to claim 1. The water-soluble resin is a styrene resin,
The raw material pulp of the surface layer contains 5 to 50% by weight of softwood pulp,
The multilayer paperboard according to claim 2. The raw material pulp contains 3 to 20% by mass of an inorganic pigment,
The paper density is 0.51 to 1.10 g / cm ³ .
The multilayer paperboard according to any one of claims 1 to 3. All of the exterior, the core, and the interior are composed of the multilayer paperboard according to any one of claims 1 to 4.
A cardboard sheet characterized by that.

Images