JP4961266B2 - Multilayer paperboard and packaging container using this paperboard - Google Patents

Description

  The present invention relates to multilayer paperboard, and more specifically, has excellent heat insulation, heat retention and cold insulation, and is suitable for printing, corrugated sheet, corrugated packaging container, interior packaging container, etc. The present invention relates to a multilayer paperboard excellent in suitability and recycling, and a packaging container using this multilayer paperboard.

  Styrofoam made by inflating polystyrene raw material with a foaming agent such as butane is mainly used for packaging materials and cushioning materials for fresh products that require heat insulation, heat insulation, and cold insulation, and insulation materials for construction. It has been used in large quantities because of its good properties, low cost and light weight.

  However, the foamed polystyrene has a problem that the load on the environment is large at the time of disposal. That is, if this styrene foam is disposed of by incineration, the incinerator is damaged because of the high combustion calories, and it becomes a pollutant such as black smoke and harmful substances, causing air pollution. On the other hand, when the polystyrene foam is disposed of by landfill treatment, it is bulky and hardly decomposable, so that it remains in the soil as it is, thereby shortening the life of the landfill disposal site. In addition, although separate collection and recycling of polystyrene foam are being studied, a fundamental measure has not yet been established from the viewpoint of recovery and recycling costs.

  On the other hand, paper has a low calorie calorie, generates less smoke and harmful substances due to combustion, and is easily decomposable. For this reason, attempts have been made to develop paper having heat insulating properties and heat retaining properties instead of polystyrene foam.

  Various types of foamed paper using foamable microcapsules that foam by heat have been proposed as paper having heat insulating properties, heat retaining properties, and cold retaining properties. This foamable microcapsule is one in which a low-boiling agent such as butane gas is enclosed in a fine particle outer shell of a thermoplastic synthetic resin such as a copolymer of methacrylic acid and styrene, a copolymer of acrylonitrile and styrene, or vinylidene chloride. Yes, the outer shell is softened by heating, and a low-boiling solvent such as butane gas is vaporized and expanded to form a microballoon that is a hollow closed cell (see, for example, Patent Document 1 and Patent Document 2). .

  Examples of the method for imparting foamable microcapsules (also referred to as “thermally foamable particles”) to paper by heat include an internally added papermaking method in which paper is made by mixing thermally foamable particles with pulp raw materials, and paper. A method of spraying thermally foamable particles onto wet wet paper that retains a large amount of water during the manufacturing process, and impregnating with an impregnating liquid comprising foamable microcapsules and rubber latex and / or synthetic resin emulsion by a wet impregnation method. The method can be used. As described above, a method for producing a low-density paper is disclosed in which the paper can be made to have a low density by applying the thermally foamable particles to the paper and then heating the paper (Patent Document 3, Patent Document 4, Patent). Reference 5).

  However, all the papers having thermally expandable particles described in Patent Documents 3 to 5 are foamed with thermally expandable particles such as expandable microcapsules, and the entire paper layer is porous, and the microcapsules are expanded. As a paper used for packaging containers for heat insulation and heat insulation, microballoons hinder the bond between pulp fibers and greatly reduce the paper strength and peel strength between paper layers, and are easily peeled off, torn or torn. Is not suitable.

  Moreover, in the paper which has the heat-expandable particle | grains described in patent document 3 and patent document 4, although a foamable microcapsule is mixed with raw material pulp and paper-making is carried out, a foamable microcapsule stays physically in a pulp fiber form. Therefore, the yield on the paper machine wire is very poor, and there is a problem that an expensive foamable microcapsule must be excessively mixed with the raw material pulp.

  Therefore, as a material having a heat insulating effect other than the foamable microcapsule, there is a heat insulating paint currently used for architectural purposes, and a hollow ceramic is frequently used as a raw material of the paint. This paint is a paint for paint that is thickly applied to walls and roofs with brushes or sponge rollers, etc., so it has high thixotropy, and a resin with high viscosity such as a thickener is used to make the paint. Yes. Therefore, since such a paint has a too high viscosity, it cannot be applied or printed by a coating machine or a printing machine of a paper machine.

  In order to obtain a higher heat insulating effect, the hollow inorganic particles preferably have a high porosity. However, when the porosity is high, the particle size of the hollow inorganic particles also increases, and the larger the particle size, the higher the thixotropy of the paint.

  Further, by using hollow inorganic particles having a small particle diameter and a low porosity and mixing a large amount of resin as a binder, a paint having low viscosity and low thixotropy can be obtained. However, since such a paint has a low blending amount of hollow inorganic particles and a low porosity, a sufficient film thickness can be obtained when this paint is applied or printed with a coating machine or a printing machine of a paper machine. There was a problem that the heat insulation effect could not be obtained.

  In addition, when it passes through coating equipment or a printing machine many times and a coating material is applied to paper many times, the thickness of a coating film can be increased and the heat insulation effect can be acquired. However, since the coating or printing process is repeated many times, the cost for this process increases. Moreover, considering that the amount of energy consumption used in this process increases, it is considered that the use of polystyrene foam has less environmental impact.

  Also, as shown in Patent Document 6, a method for obtaining water resistance and oil resistance by applying ceramic fine powder and acrylic resin to paper has been proposed. However, since the content of the ceramic fine powder in the paint is small, it is considered that the heat insulation effect cannot be obtained. In addition, hollow inorganic particles having a large particle diameter have poor dispersibility and high thixotropy, so when hollow inorganic particles are dispersed in a binder such as water or styrene / butadiene copolymer latex (SBR), an aqueous solution is used during stirring. Although it is in the form of a solid, it will solidify as soon as stirring is stopped. For this reason, coating or printing with a coating machine or a printing machine of a papermaking facility is impossible. Furthermore, Patent Document 6 does not disclose any details such as the combination of ceramic and resin.

  Moreover, although there is no prior art document, it is also conceivable to obtain foamed paper by applying a coating solution containing thermally foamable particles on the paper surface on or off machine.

  However, the foamed paper in which the coating liquid containing thermally foamable particles is coated on the paper surface is too slippery on the paper surface due to foaming of the thermally foamable particles. For this reason, at the time of corrugated board manufacture, it is possible that a heat | fever foaming layer will be taken by the hotplate of a corrugator machine, or a foaming agent may burst at the temperature of a hotplate, and a foaming layer may lose | disappear.

  In addition, as described above, since the heat-expandable particles alone are not fixed on the paper, the coating liquid composed of the heat-expandable particles and the binder is applied to the paper surface by a coating machine, and then heated to heat-expandable particles. Must be foamed. However, since this method uses a binder, the appropriate foaming of the thermally foamable particles is inhibited by the binder, and therefore, the heat insulation and heat retaining effects that are manifested by appropriately foaming the thermally foamable particles. It becomes difficult to obtain.

  Further, when the content of the heat-foamable particles is increased, there is a problem that the cost of the foamed paper is increased and the surface strength and printability of the paper are lowered by the heat-foamable particles.

  Furthermore, since the coating amount of the coating liquid containing thermally foamable particles on the paper surface is limited to a certain amount or less, the coating amount of thermally foamable particles is limited, and the coating layer Since the thickness of the film is thin, it is considered that it is inferior to the above-described internal addition method and impregnation method in terms of heat insulating properties and heat retaining properties, so that it has not been put into practical use.

Japanese Examined Patent Publication No. 42-26524 Japanese Patent Publication No. 44-7344 JP-A-5-339898 JP-A-10-88495 JP-A-8-226097 Japanese Patent No. 2736731

  The present invention has been made in view of the above-described circumstances, and the object of the present invention is a multi-layered plant pulp fiber having a recyclability, easy processability and easy incineration when the product is discarded as a main raw material. It is intended to provide a paperboard obtained by coating a paperboard with a heat-insulating and heat-retaining coating solution, and a packaging container using the multilayer paperboard.

The object of the present invention is to provide a coating layer on at least one surface of a base paper by applying a coating liquid containing hollow inorganic particles having an average particle diameter of 2 to 90 μm, a moisture-proofing agent, and a binder. After applying the working solution, by performing a flattening treatment, the smoothness is set to 12 to 360 seconds, and the coating solution further contains organic hollow particles and / or silica particles, and the coating solution. The content of the hollow inorganic particles in all the particles therein is 15% or more and 95% or less, and the content of each of the moisture-proofing agent and the binder is the solid weight of all particles in the coating liquid. This is achieved by providing a multilayer paperboard characterized by being 3 parts by weight or more and 50 parts or less as 100 parts by weight.

Further, the above object of the present invention is more effective by providing a multilayer paperboard characterized in that the coating amount of the coating layer is 2 g / m ² or more and 60 g / m ² or less in terms of solid weight. Is achieved.

  Furthermore, the above object of the present invention can be achieved more effectively by providing a packaging container using the multilayer paperboard described above.

  According to the multilayer paperboard of the present invention, a coating layer is applied by applying a coating liquid containing at least hollow inorganic particles having an average particle diameter of 2 to 90 μm, a moisture-proofing agent, and a binder on at least one side of the base paper. Since it is provided, it has excellent heat insulation and heat retention. Furthermore, it is excellent in printability, corrugated sheet, corrugated packaging container, interior packaging container, etc.

In addition, when the coating amount of the coating layer is 2 g / m ² or more and 60 g / m ² or less in terms of solid weight, the heat insulating effect is improved, the cold insulation and the heat retaining properties are further improved, and the ruled line cracking is prevented. Can do.

  Hereinafter, the multilayer paperboard according to the present invention will be described in detail by taking as an example a case where the base paper is composed of three paper layers, a surface layer, an intermediate layer, and a back layer. The multilayer paperboard according to the present invention is not limited to the following embodiments, and it goes without saying that the configuration can be changed as appropriate without departing from the scope of the claims.

  The multilayer paperboard according to the present invention (hereinafter referred to as “main paperboard”) is a base paper made up of three paper layers: a surface layer, a back layer, and a single middle layer disposed between the front and back layers. The coating layer is provided by applying a coating liquid containing hollow inorganic particles and a moisture-proofing agent to at least one surface of the base paper.

  As the hollow inorganic particles contained in the coating liquid applied to the present paperboard, an inorganic pigment obtained by hollow-molding an inorganic material such as silicon, aluminum, titanium, calcium, or magnesium by a method such as firing is used. Examples of such hollow inorganic particles include hollow silica particles, hollow alumina particles, and hollow magnesium particles. Specific examples include “Senolite M-732C”, “SZ-3”, “DH” manufactured by Sakai Kogyo Co., Ltd., “Z-60” manufactured by Tokai Kogyo Co., Ltd., and “X-100”. Etc. can be used.

  Such hollow inorganic particles preferably have an average particle size of 2 μm or more and 90 μm or less, and more preferably an average particle size of 4 μm or more and 40 μm or less. When the average particle diameter exceeds 90 μm, when the coating liquid containing hollow inorganic particles is applied to the surface (at least one side) of the base paper of this paperboard, the surface irregularities increase and the occurrence of printing defects increases. Since the particles are large, there is a problem that even if a large amount of binder is added, the particles are difficult to adhere to the surface of the base paper, and it becomes difficult to obtain a predetermined surface strength. On the other hand, if the average particle diameter is less than 2 μm, the void ratio of the hollow inorganic particles becomes small, and the desired heat insulation of the present paperboard cannot be obtained, so it is necessary to increase the coating amount of the coating liquid. However, when coating or printing is performed with a coating machine or printing machine of a papermaking facility, it is necessary to perform coating or printing many times, resulting in problems such as high costs and increased environmental impact. To do. The average particle diameter in the present invention is the number n obtained by actually measuring the coating layer surface with an n number of 60 in a scanning electron micrograph and excluding 5 measured values (10 measured values in total) of the maximum value and the minimum value. The average value of 50 is shown.

  Further, the coating liquid applied to the paperboard also contains a moisture-proof agent. Thereby, when this paperboard is processed and used for a packaging container, since heat | fever passage between the inner side and the outer side of a packaging container is suppressed, heat insulation can be improved.

  As the moisture-proofing agent, trade names “Ultrasol D400” manufactured by Gantz Kasei Co., Ltd., “Brighton FC115” and “Brighton FC3062” manufactured by Sakata Inx Co., Ltd. Commercially available products such as “-670” can be used alone or in admixture of two or more.

  The content of the moisture-proofing agent is preferably 3 parts or more and 50 parts or less in terms of solid weight, with the solid weight of all particles in the coating solution being 100 parts by weight. When the content of the moisture-proof agent is less than 3 parts, the moisture-proof effect is low, so when the board is processed into, for example, a packaging container, the passage of steam inside and outside of the packaging container increases, and the desired insulation of the board is achieved. It is difficult to obtain an effect. On the other hand, when the content of the moisture-proof agent exceeds 50 parts, the concentration of particles such as hollow inorganic particles in the coating liquid becomes low, so that it is difficult to obtain a desired heat insulating effect of the present paperboard.

  Moreover, it is preferable that the coating liquid applied to the present paperboard contains organic hollow particles and / or silica particles. Thereby, the surface strength of the present paperboard can be improved, the occurrence of ruled line cracks can be prevented, and the coating layer can be easily provided. In addition, since the organic hollow particles have a hollow structure and the silica particles have a porous structure, the use of a coating liquid containing organic hollow particles and / or silica particles can lower the density of the coating layer. Can do. Furthermore, since organic hollow particles are elastic, they prevent the hollow inorganic particles and silica particles from being destroyed when the hollow inorganic particles and silica particles are applied by a paper machine and then calendered. The cushioning property can be given to the coating layer. Therefore, the synergistic effect that the heat insulating property and printability of the present paperboard can be further improved is obtained.

  Examples of the organic hollow particles include hollow polymer fine particles having voids inside and having a highly crosslinked polymer, and examples thereof include hollow spherical plastic pigments. As such organic hollow particles, specifically, trade name “MH5055” manufactured by Nippon Zeon Co., Ltd., trade name “Grossdale” manufactured by Mitsui Chemicals, Inc., or the like may be used alone or in combination. it can.

Silica particles (SiO ₂ ), also called silicic anhydride, are the same inorganic material as the hollow inorganic particles, and are inexpensive because they exist mainly in nature, and are suitable for dispersion of the hollow inorganic particles because the particle diameter is small. Yes. Examples of the silica particles include quartz, scale silica, stishovite, cristobalite, corsite, and jasper.

  In addition, in order to obtain a coating liquid having low thixotropy containing hollow inorganic particles having an average particle diameter of 2 μm or more and 90 μm or less as described above, the average particle diameter of the organic hollow particles is 0.05 μm or more and 10 μm. The average particle diameter of the silica particles is preferably 0.1 μm or more and 10 μm or less. In this way, organic hollow particles and silica particles having an average particle size smaller than that of the hollow inorganic particles are contained, and a commercially available dispersant such as “Demol MS” manufactured by Kao Corporation is added. By disposing, it is possible to disperse the hollow inorganic particles and to prevent the bonding between the inorganic particles, which is a factor that increases thixotropy. That is, the thixotropy of the coating liquid can be lowered and noniotropic can be achieved.

  When the average particle diameter of the organic hollow particles is less than 0.05 μm, the cushioning property of the coating layer formed by coating the coating liquid cannot be obtained, and the printability is inferior. After coating the coating solution at, when passing through the calendar, the hollow inorganic particles begin to be destroyed, so that the heat insulation is reduced. On the other hand, when the average particle diameter of the organic hollow particles exceeds 10 μm, the distance between adjacent hollow inorganic particles becomes too large, so that the heat insulating property is lowered.

  Further, if the average particle size of the silica particles is less than 0.1 μm, the distance between the hollow inorganic particles becomes small, so that the thixotropy of the coating liquid cannot be lowered, and the coating machine or printing machine of the papermaking equipment May cause problems in coating or printing. On the other hand, when the average particle diameter of the silica particles exceeds 10 μm, the distance between adjacent hollow inorganic particles becomes too large, so that the heat insulating effect is lowered.

  In addition, the content of the hollow inorganic particles, the organic hollow particles, and / or the silica particles in all the particles in the coating liquid is 15% or more and 95% or less of the hollow inorganic particles, and the organic hollow particles and / or silica. The particles are 5% or more and 85% or less.

  When the solid weight content of the hollow inorganic particles in all the particles in the coating liquid is less than 15%, the content of the hollow inorganic particles is too small, so that the desired heat insulating effect of the present paperboard cannot be obtained. On the other hand, when the solid weight content of the hollow inorganic particles exceeds 95%, the content of the organic hollow particles and / or silica particles in the coating liquid decreases, so that the distance between adjacent hollow inorganic particles is too short. For this reason, the thixotropy of the coating liquid cannot be lowered, and there may be a problem in coating or printing with a coating machine or a printing machine of a papermaking facility.

  Moreover, since the concentration and viscosity of the coating liquid can be easily adjusted by using solid hollow inorganic particles, organic hollow particles, and silica particles, a larger amount can be obtained by one coating or printing. This coating liquid can be applied, so that the cost of the paperboard can be reduced and the paperboard can be more easily manufactured.

  The coating liquid applied to the base paper of the present paperboard contains a binder for adhering the above-described particles to the surface of the base paper. As such a binder, for example, various known materials such as vinyl acetate, acrylic, polyvinyl alcohol (PVA), styrene / butadiene copolymer latex (SBR), starch, and polyacrylamide (PAM) can be used.

  The binder content is preferably 3 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the solid weight of all particles in the coating liquid. When the binder content is less than 3 parts, particles in the coating liquid such as hollow inorganic particles are difficult to adhere to the paper surface, and the surface strength of the paperboard is reduced. On the other hand, when the content of the binder exceeds 50 parts, the effect of the binder reaches a peak, and the manufacturing cost of the coating liquid increases, and accordingly, the manufacturing cost of the present paperboard also increases.

  Furthermore, the binder preferably has a glass transition temperature (Tg) of −50 to 30 ° C., more preferably −30 to 20 ° C. Since such a binder has a soft property, it is possible to improve the folding suitability of the present paperboard and to reduce the viscosity at the time of application of the coating liquid. Further, after drying, an appropriate effect of improving the surface strength can be obtained, so that the processing suitability of the paperboard is further improved.

  Moreover, you may add a thickener and a dispersing agent as an auxiliary agent to a coating liquid in order to improve the dispersibility of an organic hollow particle and a silica particle.

It is preferable to adjust the viscosity of the coating liquid to 20 to 1000 cps at a B-type viscometer 20 rpm and 50 to 500 cps at 60 rpm because of excellent coating suitability in a coating method described later.
The coating amount of the above-described coating solution is preferably at one side dsb weight is 2 g / m ² or more 60 g / m ² or less. Thereby, while being able to improve the printability of this paperboard, surface strength can be improved, generation | occurrence | production of a ruled line crack can be decreased.

When the coating amount of the coating liquid is less than 2 g / m ² , the coating layer is thin, so that the heat insulating property of the paperboard is remarkably lowered and the surface of the coating layer is also roughened. It becomes easy to do. On the other hand, when the coating amount of the coating liquid exceeds 60 g / m ² , the coating layer is too thick, and thus the coating layer is easily broken, and the ruled line is formed even when the paperboard is processed into a packaging container or the like. Cracks are likely to occur.

  The coating liquid can be applied to at least one side of the base paper by a known coating means such as a bar coater, a rod coater, or an air knife. Moreover, it can also print by well-known printing means, such as a gravure printing machine and a flexographic printing machine. Among these, a bar coater, a rod coater, an air knife and the like are particularly preferable because they can easily apply a predetermined amount of the coating liquid of the present invention.

  Moreover, it is preferable to perform a calendar process on the base paper in the previous step of applying the coating liquid. As a result, the surface of the base paper becomes dense and the coating liquid can be efficiently retained on the surface of the base paper, so that the present paperboard can be made more excellent in heat insulating effect.

  In addition, when a coating solution is applied in the paper making process, a calendar process is performed, and if the smoothness of the paperboard is 12 to 360 seconds, preferably 22 to 360 seconds, more preferably 56 to 360 seconds, high printability. Can be obtained.

  In addition, it is preferable that the calendar process performed after apply | coating a coating liquid is a soft calendar process which can improve printability, suppressing the fall of paper thickness rather than the calendar process using a steel roll. That is, in order for the present paperboard to have both excellent heat insulation and printability, it is necessary to prevent the hollow inorganic particles in the coating layer from being destroyed.

  Below, the base paper of this paperboard is demonstrated.

  As described above, the base paper of the present paperboard is composed of three paper layers including a front layer, a back layer, and a single middle layer disposed between the front and back layers.

  The main purpose of this paperboard is to be processed and used for packaging containers such as cardboard packaging containers and interior packaging containers with excellent heat insulation and heat retention used for transportation, storage and protection. It is necessary to have excellent strength for bonding and box making and suitable strength as a packaging container.

  Therefore, the surface layer of this paperboard (1) prevents cracking of ruled lines during processing into cardboard packaging containers, interior packaging containers, etc., (2) has high surface strength, transports, stores and protects the contents. (3) It is a layer having a role of having coating suitability for a coating liquid containing hollow inorganic particles and a moisture-proofing agent, and (4) ensuring printability.

  Examples of surface pulp include hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), softwood unbleached kraft pulp (NUKP), and hardwood semi-bleached kraft pulp (LSBKP) Chemical pulp such as softwood semi-bleached kraft pulp (NSBKP), hardwood sulfite pulp, softwood sulfite pulp, stone grand pulp (SGP), pressurized stone grand pulp (PGW), refiner grand pulp (RGP), thermo grand pulp (TGP) ), Chemi-Grand Pulp (CGP), Crushed Wood Pulp (GP), Thermomechanical Pulp (TMP) Waste paper, Kent waste paper, imitation Chemically or mechanically from disaggregated waste paper pulp, disaggregated / deinked waste paper pulp, or disaggregated / deinked / bleached waste paper pulp, or non-wood fibers such as kenaf, hemp, straw, etc. Various well-known pulps such as the pulp produced in the above can be used.

  Among these raw material pulps, LBKP, NBKP, LUKP, NUKP, or upper white waste paper, Kent waste paper, in order to achieve the balanced and efficient achievement of the role of the surface layer of the present paperboard, various quality characteristics as the bookboard, etc. It is preferable to use waste paper pulp manufactured from waste tea paper and kraft envelope waste paper.

  Moreover, it is preferable to contain 5-70 mass% of conifer kraft pulp (NKP) in the raw material pulp of the surface layer, and further, when the content of NKP is 25-70 mass%, the rupture strength is improved and ruled line cracks are caused. Since it can prevent effectively, it is more preferable.

  In addition, if the content of NKP in the raw material pulp of the surface layer is less than 5% by mass, the content of NKP with a long fiber length and a thick fiber decreases, so that the bursting strength is reduced, and ruled line cracks occur during box making. It tends to occur. On the other hand, if the content of NKP exceeds 70% by mass, it causes variations in strength due to unevenness in texture and a decrease in appearance. In addition, when the coating liquid containing the hollow inorganic particles is applied, the coating liquid penetrates very much into the surface of the base paper, so that a coating layer having heat insulating properties and heat retaining properties can be efficiently used. There is also a possibility that the problem that it cannot be formed will occur.

  Furthermore, the freeness of the raw material pulp is preferably 280 to 530 cc, more preferably 320 to 430 cc. In addition, freeness is the value which measured the freeness by the Canadian standard freeness tester based on JIS-P8121, after disintegrating the sample by the standard breaker based on JIS-P8220. (The same applies hereinafter).

  That is, when the freeness of the raw material pulp of the surface layer is less than 280 cc, the fiber length of the raw material pulp is shortened, so that the burst strength is reduced, and ruled line cracks and square cracks are likely to occur during box making. On the other hand, if the freeness exceeds 530 cc, the fiber length is long and the coating liquid containing the hollow inorganic particles will permeate the surface layer excessively. There is also a possibility that the problem that it cannot be formed may occur.

  Although it is possible to increase the coating amount of the coating liquid, excessive coating reduces the production efficiency and increases the amount of expensive hollow inorganic particles. There is a risk of cost increase.

  Next, the raw material composition of the middle layer and the back layer of the present paperboard will be described.

  As the raw material pulp for the middle layer and the back layer of the base paper of the present paperboard, various known pulps can be used as in the case of the surface layer. Among them, in particular, as with the surface layer, LBKP, NBKP, LUKP, NUKP, in order to efficiently achieve various quality characteristics such as improvement in bursting strength and compression strength, which are the roles of the back layer of the present paperboard, in a balanced manner. It is preferable to use LSBKP, NSBKP, or waste paper pulp produced from tea waste paper or kraft waste paper. In addition, when selecting raw material pulp, it is preferable to mix | blend as much waste paper pulp as possible from the reduction of the energy unit and the load given to an environment.

  Moreover, it is preferable to contain 10-80 mass% of NKP in the raw material pulp in the middle layer and the back layer of this paperboard, and when the content of NKP is 40-60 mass%, the bursting strength is improved. In addition, it is possible to effectively prevent the occurrence of ruled line cracks and square cracks when processing the packaging container of the present paperboard.

  Further, the freeness of the raw material pulp of the middle layer and the back layer is preferably 280 to 480 cc in order to effectively prevent the occurrence of rupture, ruled line cracking, square cracking, etc. during container packaging processing as with the surface layer. In order to prevent a decrease in tensile strength, it is more preferable to set it to 300 to 440 cc.

  Used paper pulp includes tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, corrugated cardboard paper, Kamihaku waste paper, Kent waste paper, imitation waste paper, and old paper waste paper, etc.・ Deinked waste paper pulp or disaggregation / deinking / bleached waste paper pulp can be used.

Moreover, although the basic weight of this paperboard is not specifically limited, For example, 70-1000 g / m < ² > is preferable and it is more preferable in it being 140-700 g / m < ² >. In addition, this basic weight is the value of the basic weight measured based on JIS-P8113. If the basis weight is less than 70 g / m ² , there is a concern that poor coating suitability and poor printing suitability may occur during the production of the paperboard. On the other hand, if the basis weight exceeds 1000 g / m ² , it is not preferable because the thickness of the paperboard is too thick and it becomes difficult to wind.

  The papermaking method for the present paperboard is not particularly limited, and any of an acidic papermaking method, a neutral papermaking method, and an alkaline papermaking method may be used. Also, the paper machine is not particularly limited, and various known paper machines such as a long net paper machine, a twin wire paper machine, a circular net paper machine, and a short net combination machine can be used. .

  Since the multilayer paperboard according to the present invention formed as described above is excellent in heat insulation and heat retention without bonding paperboard and foamed paper, for example, the process can be simplified.

Specifically, using a heat insulation / condensation test chamber as shown in FIG. 1 based on JIS-A1420 (insulation performance testing method for residential insulation and components), one sample is set in the condensation test chamber, Low temperature when the test room conditions are constant temperature and humidity room temperature 30 ± 2 ° C, heating box temperature 40 ± 2 ° C, low temperature room temperature -20 ± 2 ° C, and the surface temperature of the paper is measured inside the low temperature room The surface temperature of the indoor paper can be suppressed to 0 ° C or lower, preferably -3 ° C or lower, more preferably -7 ° C or lower. Also, JIS-Z0208 (dry packing material amount of moisture permeability test method - cup method -) according to, was measured standing condition as 40 ℃ × 90% RH moisture permeability may be less than 1000g ^/ m 2 ^/ 24h .

  In addition, because it has excellent surface strength, it was impossible to use conventional foamed paper due to its weak surface strength. It was used for transportation, storage, and protection. It can be used for a packaging container such as a packaging container, and problems such as ruled line cracking do not occur even when used for such a packaging container.

  As described above, the present paperboard has been described with respect to the case where the paper layer is composed of the three paper layers of the front layer, the back layer, and the middle layer. However, the present invention is not limited to such a paperboard, and for example, the surface layer, the two layers A paperboard having four paper layers as the middle layer and the back layer, or a paperboard having five or more paper layers by increasing the number of middle layers may be used.

  In order to confirm the effect of the multilayer paperboard according to the present invention, various samples as described below were prepared, and tests for evaluating the quality of these samples were performed. In addition, in a present Example, the numerical value which shows a mixing | blending, a density | concentration, etc. is a numerical value based on the weight of a solid content or an active ingredient. Moreover, since the pulp, chemicals, and the like shown in this embodiment are merely examples, it goes without saying that the present invention is not limited by these embodiments and can be appropriately selected.

  The production conditions for each sample are shown below. Unless otherwise specified, the raw material composition, drainage, chemical addition conditions, etc. of the surface layer, middle layer (3 layers), and back layer are the same.

［基紙の製造］
＜１＞表層
針葉樹晒クラフトパルプ（ＮＢＫＰ）３０質量％と、広葉樹晒クラフトパルプ（ＬＢＫＰ）３０質量％と、上質古紙パルプ４０質量％とを配合した後に、離解フリーネスを３８０ｃｃに調整した原料パルプに、硫酸バンド４質量％、サイズ剤（近代化学工業株式会社製Ｒ５０）を固形分として０．３質量％添加して表層用の原料スラリーを調整した。なお、「離解フリーネス（ｃｃ）」は、各試料を約３ｃｍ^２の大きさに裁断して約２５ｇの重さの試験片とし、この試験片を１リットルの水に２４時間浸漬した後、ＪＩＳ−Ｐ８２２０に準拠して標準離解機で１５分間離解処理し、試験片が完全に離解していることを目視で確認した後、ＪＩＳ−Ｐ８１２１に準拠してカナダ標準濾水度試験機にて測定した濾水度の値である（以下、同様）。
＜２＞中層（１）
ケント古紙パルプ６０質量％と上質古紙パルプ４０質量％とを配合した後に、離解フリーネスを３５０ｃｃに調整した原料パルプに、硫酸バンド４質量％、サイズ剤（近代化学工業株式会社製Ｒ５０）を固形分として０．３質量％添加して原料スラリーを調整した。
＜３＞中層（２）、（３）及び裏層
地券古紙パルプ１００質量％を、離解フリーネス２８０ｃｃに調整し、硫酸バンド４質量％、サイズ剤（Ｒ５０）を固形分として０．３質量％添加して原料スラリーを調整した。

[Manufacture of base paper]
<1> Surface layer After blending 30% by weight of softwood bleached kraft pulp (NBKP), 30% by weight of hardwood bleached kraft pulp (LBKP), and 40% by weight of high-quality waste paper pulp, the raw pulp with adjusted disintegration freeness to 380cc Then, 4% by mass of a sulfuric acid band and 0.3% by mass of a sizing agent (R50 manufactured by Modern Chemical Industry Co., Ltd.) were added as a solid content to prepare a raw material slurry for the surface layer. The “disaggregation freeness (cc)” is obtained by cutting each sample into a size of about 3 cm ² to prepare a test piece having a weight of about 25 g, and immersing the test piece in 1 liter of water for 24 hours, and then JIS. -Measured with a Canadian standard freeness tester in accordance with JIS-P8121, after visually confirming that the test piece was completely disaggregated in accordance with JIS-P8121. The freeness value obtained (the same applies hereinafter).
<2> Middle layer (1)
After blending 60% by weight of Kent waste paper pulp and 40% by weight of high-quality waste paper pulp, 4% by weight of sulfuric acid band and sizing agent (R50 manufactured by Modern Chemical Industry Co., Ltd.) are added to the raw pulp whose disintegration freeness is adjusted to 350cc. As a raw material slurry was prepared by adding 0.3% by mass.
<3> Middle layer (2), (3) and back layer 100% by mass of old paper pulp is adjusted to 280 cc of disaggregation freeness, and 4% by mass of sulfuric acid band and 0.3% by mass of sizing agent (R50) as solid content The raw material slurry was adjusted by adding.

Using these raw material slurries, the surface layer, the middle layer (1), the middle layer (2), the middle layer (3) and the back layer of the five paper layers are combined with an ultra former (manufactured by Kobayashi Manufacturing Co., Ltd.). The coating amount of the surface layer is 30 g / m ² , the coating amount of the middle layer (1) is 40 g / m ² , the middle layer (2), the middle layer (3), and the back layer are adjusted according to the coating amount of the coating liquid, and the entire board 5 layers of base paper having a basis weight of 220 g / m ² was obtained by ultra Yankee former papermaking. The basis weight was measured in accordance with “Paper and paperboard—basis weight measurement method” described in JIS-P8142.

[Adjustment of coating solution]
The coating liquid that is applied to at least the surface of the surface of the base paper thus formed to form a coating layer will be described. That is, as shown in Table 1, 24 types of coating liquids according to the present invention and 5 types of coating liquids were prepared for comparative examination of the present invention. In addition, "%" in a table | surface all shows solid weight%.

“A” to “L” and “a”, “b” in Table 1 indicate the types of hollow inorganic particles, organic hollow particles, and silica particles contained in the coating liquid, and are as follows.
[Hollow inorganic particles]
(A) Average particle diameter of 1.5 μm (manufactured by Tokai Industry Co., Ltd.)
(B) Average particle size 2.0 μm (manufactured by Tokai Kogyo Co., Ltd.)
(C) Average particle size 90 μm (manufactured by Tokai Kogyo Co., Ltd.)
(D) Average particle size 92 μm (manufactured by Tokai Kogyo Co., Ltd.)
(A) Average particle size 4 μm (manufactured by Tokai Kogyo Co., Ltd.)
(B) Average particle diameter of 40 μm (Tokai Kogyo Co., Ltd.)

[Organic hollow particles]
(E) Average particle size 0.05 μm (Mitsui Chemicals)
(F) Average particle size 0.1 μm (Mitsui Chemicals)
(G) Average particle diameter of 10 μm (Mitsui Chemicals)
(H) Average particle size 11 μm (Mitsui Chemicals)

[Silica particles]
(I) Average particle size 0.03 μm (Okutama Kogyo Co., Ltd.)
(J) Average particle size 0.05 μm (Okutama Kogyo Co., Ltd.)
(K) Average particle size 10 μm (Okutama Kogyo Co., Ltd.)
(L) Average particle size 11 μm (Okutama Kogyo Co., Ltd.)

[Binder]
SBR Smarttex, Tg-5 ° C, solid content 50% (Nippon A & L Co., Ltd.)

[Moisture-proofing agent]
OP670, Tg-10 ° C., solid content 40% (manufactured by Yushi Co., Ltd.)

Such hollow inorganic particles, organic hollow particles, silica particles, a binder, and a desiccant were blended as shown in Table 1 to prepare a coating liquid in which the total solid concentration was adjusted to 65%.

[Coating liquid coating on multilayer paperboard]
On one side of the base paper obtained as described above, the coating liquid prepared as described above was applied on the on-machine bar coater installed in the paper machine with the coating amount shown in Table 1 as the solid weight per side. Apply.

  After that, it was dried with an after dryer having a dryer cylinder surface temperature of about 100 ° C., and then the smoothness was adjusted as shown in Table 2 by adjusting the linear pressure with a soft calender. Example 24 and Comparative Examples 2 to 5) were obtained.

Further, as Comparative Example 1, PVA (JF17 manufactured by Nihon Vinegar Bipovar Co., Ltd.) on a single side of the base paper with an on-machine rod coater installed in a paper machine, in the same manner as ordinary paperboard, 0.5 g in solid weight per side. After coating / m ² , the dryer was dried with an after dryer having a dryer cylinder surface temperature of about 100 ° C., and then subjected to a linear pressure as shown in the attached table with a soft calender to obtain a multilayer paper-insulated paperboard.

  In Table 1, “viscosity (cps)” is the viscosity of the coating solution, which is a value measured using a B-type viscometer at 20 rpm and 60 rpm. The viscosity value measured at a rotation speed of 20 rpm is higher than the viscosity value measured at 60 rpm, and the greater this difference, the higher the thixotropy.

  Table 2 shows the results of the basis weight, the heat insulation test, and the test for evaluating the surface strength of all the examples and comparative examples.

  Unless otherwise specified, this evaluation test was conducted under environmental conditions of a temperature of 23 ° C. ± 1 ° C. and a humidity of 50 ± 2% in accordance with JIS-P8111.

  In addition, “surface temperature (° C.)” in Table 2 refers to a heat insulation test based on JIS-A1420 (a heat insulation performance test method for residential heat insulation materials and components) in order to evaluate the heat insulation properties of paperboard. Using a heat insulation / condensation test chamber as shown in Fig. 1, one sample is set in the condensation test chamber, and the test chamber conditions are a constant temperature and humidity room temperature of 3 ° C ± 2 ° C, a heating box temperature of 40 ± 2 ° C, and a low temperature room temperature. The surface temperature of the paper was measured at −20 ± 2 ° C. inside the low temperature room.

  The “smoothness (seconds)” is a value measured according to JIS-P8119.

  “Printability” means that the standard tack grade ink used in the IGT printability tester stipulated in JIS-P8129 is used, and when printing is performed using the KRK Universal Printability Tester manufactured by Kumagaya Riki Kogyo Co., Ltd. It is evaluated whether or not. The evaluation criteria were divided into four stages: “no blurring” marked with “◎”, “substantially no blurring” marked with “◯”, “slightly blurring” marked with “Δ”, and “many blurring” marked with “×”.

“Moisture permeability” is measured and evaluated according to JIS-Z0208 (moisture-proof packaging material amount of moisture permeability test method-cup method) with the standing condition set at 40 ° C. × 90% RH. The evaluation criteria, ◎ "moisture permeability of less than 1000g ^/ m 2 ^/ 24h" in the mark, ○ "moisture permeability of 1000g ^/ m 2 ^/ 24h more than 1500g ^/ m less than 2 / 24h" in the mark, △ "moisture permeability of the mark 1500g ^/ m 2 ^/ 24h or more 2000 g ^/ m less than 2 / 24h "," moisture permeability × mark was 4 out of 2000g ^/ m 2 ^/ 24h or more. "

  “Surface strength (A)” was evaluated as a paperboard used for a packaging container based on the value of the surface strength measured according to JIS-P8129. The evaluation criteria are 4 with “Surface strength is 14A or more” marked with ◎, “Surface strength is 13A to 11A” with ◯, “Surface strength is 10A to 8A” with △, and “Surface strength is less than 7A”. Staged.

  The “ruled line cracking test” is a method in which folding is repeated 10 times with a MIT testing machine of a folding resistance test method, and the method of cracking the fold formed on the coated surface is evaluated. The evaluation criteria are: “A crack in the coating layer has not occurred”, “A crack in the coating layer has hardly occurred” in a circle, “A crack in the coating layer has occurred in a triangle” However, there were no problems in practical use ”, and“ x ”indicates“ there are many cracks in the coating layer ”.

  “Cost” is an evaluation of the cost of manufacturing the paperboard according to each of the examples and comparative examples, and the evaluation criteria are “inexpensive” marked with ○, “normal” marked with △, It was three stages of “expensive”.

表２に示すように、本発明に係る多層抄き板紙、すなわち実施例１〜実施例２４に係る多層抄き板紙は品質評価に優れることが分かる。すなわち、本発明に係る多層抄き板紙は、断熱性・保温性に優れるので、断熱性及び保温性を要する包装容器に好適に用いることができ、また表面強度等にも優れるので、包装容器等に加工しても罫線割れが発生しにくいことが分かる。

As shown in Table 2, it can be seen that the multilayer paperboard according to the present invention, that is, the multilayer paperboard according to Examples 1 to 24, is excellent in quality evaluation. That is, the multilayer paperboard according to the present invention is excellent in heat insulation and heat retention, and therefore can be suitably used for packaging containers that require heat insulation and heat retention, and also has excellent surface strength, etc. It can be seen that cracking of the ruled line hardly occurs even when processed into a shape.

It is the schematic of the heat insulation and dew condensation test room based on JIS-A1420 (The heat insulation performance test method of a heat insulating material for a house and a structural material).

Claims (3)

On at least one side of the base paper, after applying a coating layer by applying a coating liquid containing at least hollow inorganic particles having an average particle diameter of 2 to 90 μm, a moisture-proofing agent, and a binder, and applying the coating liquid, By performing the flattening treatment, the smoothness is set to 12 to 360 seconds, and the coating liquid further contains organic hollow particles and / or silica particles, and the above-mentioned in all the particles in the coating liquid. The content of the hollow inorganic particles is 15% or more and 95% or less, and the content of each of the moisture-proofing agent and the binder is 3 parts or more when the solid weight of all particles in the coating liquid is 100 parts by weight. Multi-layer paperboard, characterized in that it is 50 parts or less. The multilayer paperboard according to claim 1, wherein the coating amount of the coating layer is 2 g / m ² or more and 60 g / m ² or less in terms of solid weight.   A packaging container using the multilayer paperboard according to any one of claims 1 and 2.

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