Paper substrate for foamed heat insulation cup and foamed heat insulation paper container

Abstract

To provide a paper substrate for a foamed heat insulation cup having excellent foamability, molding processability, and strength.SOLUTION: A paper substrate for a foamed heat insulation cup includes a base paper which is a multilayer paper of at least two layers and a water-soluble resin layer provided at least on one side of the base paper, wherein the multilayer paper is assembled with an outermost layer positioned on the side of the water-soluble resin layer and another layer which is one layer other than the outermost layer, a fiber roughness of a raw material obtained by disintegration of the outermost layer (outermost layer) is larger than a fiber roughness of a raw material obtained by disintegration of the other layer (other layer), a disintegration freeness degree of the raw material obtained by disintegration of the outermost layer (outermost layer) is larger than a disintegration freeness degree of the raw material obtained by disintegration of the other layer (other layer), and the disintegration freeness degree (other layer) is 200-500 mlCSF.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a foamed insulating paper base for a cup and a foamed insulating paper container. [Background technology]

[0002] Insulated containers are used in fast food restaurants, convenience stores, vending machines, etc. as containers for hot drinks such as coffee, green tea, black tea, or soup, as well as for instant ramen noodles in cups, etc. Generally, such insulated containers are made of expanded polystyrene (EPS), which has excellent insulating properties. In recent years, environmental issues such as plastic waste and global warming have led to a growing trend toward using less petroleum and less plastic, and it is desirable to reduce the amount of resin materials derived from fossil resources and non-biodegradable resin materials used as much as possible. Under these circumstances, it is also desirable to reduce the amount of plastic used in thermal insulation containers.

[0003] Patent Document 1 discloses a technique for imparting heat insulating properties to a paper container consisting of a container body member and a bottom plate member by laminating a low-melting thermoplastic resin film onto the outer wall surface of the container body member and heating the film to foam the thermoplastic resin film into irregularities using the vapor pressure of moisture contained in the paper substrate. Patent Document 2 also proposes a method for producing a sheet for a heat-insulating paper container having an excellent foaming property (heat insulating property) in which a foamed thermoplastic resin layer is laminated on at least one side of a paper substrate, and the paper substrate is surface-treated with a surface treatment agent containing a water-soluble polymer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 57-110439 [Patent Document 2] JP 2012-206384 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a foamed heat-insulating paper container using a paper base material, the moisture in the paper base material is heated and evaporated, and the water vapor generated is used to foam a thermoplastic resin layer to form a foamed layer, and the air in the foamed layer imparts heat insulation. In order to further foam the thermoplastic resin layer and improve the heat insulation, it is preferable that there are appropriate voids in the paper base material so that water vapor can easily pass through. Papermaking fibers with high fiber coarseness are rigid and do not easily get crushed during papermaking, so they can produce base paper with moderate voids and excellent foaming properties. On the other hand, paper made from papermaking fibers with high fiber coarseness has poor moldability because the fibers are rigid and do not easily bend (when molding a cup, the top curl part at the top of the cup does not easily take the expected shape, wrinkles are easily formed, etc.). In addition, paper made from papermaking fibers with high fiber coarseness has low strength because the contact area between fibers is small and few hydrogen bonds are formed, so it is easily deformed when made into a container and heavy objects such as liquids are put in it, and there is a concern that the contents may leak. An object of the present invention is to provide a paper base material for a foamed insulating cup that is excellent in foamability, moldability and strength. [Means for solving the problem]

[0006] The means for solving the problems of the present invention are as follows. 1. A multi-layered paper having a base paper of two or more layers and a water-soluble resin layer on at least one side of the base paper, the multi-layered paper having an outermost layer located on the water-soluble resin layer side and another layer being any one layer other than the outermost layer, the fiber coarseness (outermost layer) of the raw material obtained by defibrating the outermost layer is greater than the fiber coarseness (other layer) of the raw material obtained by defibrating the other layer, The paper base material for a foamed insulating cup is characterized in that the maceration freeness (outermost layer) of the raw material obtained by maceration of the outermost layer is higher than the maceration freeness (other layers) of the raw material obtained by maceration of the other layers, and the maceration freeness (other layers) is 200 to 500 ml CSF. 2. The paper base material for a foamed insulating cup according to 1., wherein the fiber roughness (outermost layer) is 50.0 to 70.0 μg / m. 3. The paper base material for a foamed insulating cup according to 1 or 2, characterized in that the fiber roughness (other layer) is 45.0 to 65.0 μg / m. 4. The paper base material for a foamed insulating cup according to any one of 1. to 3., wherein the macerated freeness (outermost layer) is 250 to 580 ml CSF. 5. The paper base material for a foamed insulating cup according to any one of 1. to 4., characterized in that the basis weight ratio between the outermost layer and the other layer (outermost layer / other layer) is 0.5 or more and less than 1.1. 6. The paper base material for a foamed insulating cup according to any one of 1. to 5., wherein the blending ratio of papermaking broken in the other layer is 20 to 80 mass %. 7. The paper base material for a foamed insulating cup according to any one of 1. to 6., wherein the amount of fine fibers in the raw material obtained by defibrating the other layer is 15 to 35 mass %. 8. Basis weight: 190~380g / m 2 8. The paper base material for a foamed insulating cup according to any one of 1. to 7., 9. At least one of the body member and the bottom plate member is made of foamed insulating paper; The foamed insulating paper container has a foamed insulating cup paper base material described in any one of 1. to 8. and a foamed layer made of a thermoplastic resin formed on a water-soluble resin layer of the foamed insulating cup paper base material. Effect of the Invention

[0007] The foamed heat-insulating paper base material for a foamed heat-insulating cup of the present invention has excellent foamability because the outermost layer has many voids and water vapor can easily pass through, and a foamed heat-insulating paper container with excellent heat insulation can be obtained. The foamed heat-insulating paper base material for a foamed heat-insulating cup of the present invention has a layer other than the outermost layer that has a lower fiber roughness and contains fibers that are more easily crushed than the outermost layer, and therefore has excellent moldability and strength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (Foam insulation cup paper base material) The foamed heat-insulating cup paper substrate (hereinafter also referred to as paper substrate) of the present invention has a base paper which is a multi-layer paper of two or more layers, and a water-soluble resin layer on at least one side of the base paper, The multilayer paper has an outermost layer located on the water-soluble resin layer side and another layer which is any one layer other than the outermost layer, The fiber coarseness (outermost layer) of the raw material from which the outermost layer has been defibrated is greater than the fiber coarseness (other layers) of the raw material from which the other layers have been defibrated, The maceration freeness (outermost layer) of the raw material obtained by maceration of the outermost layer is greater than the maceration freeness (other layers) of the raw material obtained by maceration of the other layers, and the maceration freeness (other layers) is 200 to 500 ml CSF.

[0009] Fiber coarseness is the mass (μg) per 1 m of fiber. Fiber coarseness can be determined using an image analyzer such as a Fiber Tester manufactured by ABB Ltd. or a Fractionator manufactured by Valmet Ltd. In this specification, the expression "A to B" (A and B are numerical values) means a numerical range including the values ​​of A and B, that is, A or more and B or less.

[0010] (base paper) The base paper used in the present invention is a multi-layer paper having two or more layers. The base paper has a water-soluble resin layer on at least one side, and the base paper, which is a multi-layer paper, has the outermost layer on the water-soluble resin layer side and another layer which is any one layer other than the outermost layer. The base paper used in the present invention has at least two or more paper layers, the outermost layer and the other layer, and may further have any optional layer. The number of paper layers of the base paper (multi-layer paper) is not limited, and can be, for example, 2 to 5 layers. From the viewpoint of simplifying the manufacturing process, 4 layers or less is preferable, and 3 layers or less is more preferable.

[0011] In the present invention, the fiber coarseness of the raw material from which the outermost layer of the multilayer paper is defibrated (the outermost layer) is greater than the fiber coarseness of the raw material from which the other layers are defibrated (the other layers). By satisfying this relationship between the outermost layer and the other layers, the base paper of the present invention has excellent water vapor permeability, moldability, and strength. The fiber coarseness (outermost layer) is preferably from 50.0 to 70.0 μg / m, and more preferably from 54.0 to 66.0 μg / m. The fiber coarseness (other layer) is preferably 45.0 to 65.0 μg / m, and more preferably 50.0 to 60.0 μg / m. The fiber roughness (outermost layer) is preferably at least 0.1 μg / m greater than the fiber roughness (other layers), and more preferably at least 2.0 μg / m greater.

[0012] In the present invention, the maceration freeness (outermost layer) of the raw material from which the outermost layer has been macerated is greater than the maceration freeness (other layers) of the raw material from which the other layers have been macerated, and the maceration freeness (other layers) is 200 to 500 ml CSF. The freeness of the macerated pulp (outermost layer) is preferably 250 to 580 mlCSF, and more preferably 300 to 550 mlCSF. The freeness of the macerated mixture (other layer) is 200 to 500 ml CSF, preferably 230 to 450 ml CSF. The maceration freeness (outermost layer) is preferably 30 ml CSF or more higher than the maceration freeness (other layers), and more preferably 50 ml CSF or more higher.

[0013] The papermaking fibers contained in each layer of the multi-layer paper may be one or more of the following: bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood pulp (NUKP), chemical pulp such as sulfite pulp, mechanical pulp such as stone grind pulp and thermomechanical pulp, papermaking broken obtained by redisintegrating unused base paper such as scraps and defective products generated during the manufacture of other base paper, deinked pulp, waste paper pulp, non-wood fibers obtained from kenaf, bamboo, hemp, etc. One may select one with the desired fiber coarseness, or two or more may be blended to obtain the desired fiber coarseness. Among these, chemical pulp and papermaking broken, which are less likely to be mixed with foreign matter, are preferred, and LBKP and NBKP are preferred as chemical pulps. Incidentally, papermaking broken is a raw material that is commonly used in manufacturing sites, and has a lower freeness compared to virgin pulp.

[0014] In order to adjust the fiber coarseness, freeness, and amount of fine fibers to appropriate values, to provide appropriate gaps between the fibers, and to improve foaming properties during molding, the outermost layer preferably contains 0 to 20% by mass of N-material (coniferous pulp) relative to the total papermaking fibers contained in the outermost layer. If the N-material content is more than 20% by mass, the paper becomes difficult to bend during molding, and molding processability is poor. As mentioned above, the expression "0 to 20% by mass" means a numerical range including 0, and means that it is an optional material and does not need to be included (0% by mass).

[0015] In order to adjust the fiber coarseness, freeness, and amount of fine fibers of the other layer to appropriate values ​​and to improve processing suitability and strength suitability, it is preferable that the N-material content of the total papermaking fibers contained in the other layer is 0 to 5 mass % and the papermaking broken content is 20 to 80 mass %. In order to improve the strength suitability, it is preferable that the amount of fine fibers in the defibrated raw material of the other layer is 15 to 35 mass %. Note that fine fibers are fibers having a fiber length of 0.2 mm or less, and can be determined by the above-mentioned fiber tester manufactured by ABB Corporation. It is more preferable that the amount of fine fibers is 20 to 35 mass %.

[0016] A multilayer paper has at least two layers, an outermost layer and an other layer, and the outermost layer and the other layer need only satisfy the above-mentioned relationship between fiber coarseness and disintegration freeness. For example, it may have two or more other layers, or it may have an optional layer that does not fall under the category of the other layer. When there are two or more other layers that satisfy the relationship with the outermost layer, it is preferable that the fiber coarseness of the other layers decreases with increasing distance from the outermost layer. It is also preferable that the macerated freeness of the other layers decreases with increasing distance from the outermost layer. When an optional layer not corresponding to the other layers is included, the fiber coarseness and defibration freeness of the raw material obtained by defibrating the optional layer are not particularly limited, and the arrangement of the optional layer is also not particularly limited.

[0017] The multi-layer paper preferably has a starch layer between the paper layers. The starch layer can be formed by spraying an aqueous starch solution onto at least one surface of the opposing paper layers before the paper layers of the multi-layer paper are laid together. The multi-layer paper having a starch layer between the paper layers has improved interlayer adhesion and is less likely to delaminate during processing. As the starch, known ones can be used. For example, one or more of cationic starch, dicarboxylate starch, urea phosphate ester starch, etherified starch, acetylated starch, oxidized starch, etc. can be used, with cationic starch and oxidized starch being preferred.

[0018] In the present invention, the method for producing the multi-layer paper is not particularly limited, and for example, a paper stock containing papermaking fibers, optional fillers, and internal chemicals is prepared for each layer, and the multi-layer paper can be produced using a multi-layer paper machine. As the multi-layer paper machine, any known paper machine capable of multi-layer papermaking can be used without any particular limitation, such as a Fourdrinier wet paper machine, a twin-wire paper machine, a Yankee paper machine, a cylinder paper machine, or a cylinder short wire combination paper machine. In addition, if necessary, a surface treatment can be performed using external chemicals.

[0019] The basis weight of the multi-layer paper is 190g / m 2 More than 380g / m 2 A basis weight of 190 g / m is preferred. 2 If the foaming rate is less than 380 g / m, the foaming rate may be insufficient due to insufficient moisture, and the container may feel hot when held by hand. 2 If it exceeds this limit, problems such as a decrease in the moldability of the container may occur. 2 More preferably, 220 g / m 2 More preferably, 360 g / m 2 Less than 340 g / m is more preferable. 2 The following is even more preferred:

[0020] The sum of the basis weight of the outermost layer and other layers is 130g / m 2 More than 285g / m 2The sum of the basis weights of the outermost layer and other layers is preferably within this range, which makes it easy to achieve foaming properties and thickness suitable for the paper base material of the foamed insulating cup paper base material. The sum of the basis weights of the outermost layer and other layers is preferably within this range. 2 More preferably, 150 g / m 2 More preferably, 270 g / m 2 Less than 250 g / m is more preferable. 2 The following is even more preferred:

[0021] The basis weight ratio between the outermost layer and the other layer (outermost layer / other layer) is preferably 0.50 or more and less than 1.1. If this basis weight ratio is less than 0.50, the permeability of water vapor is not improved significantly, and if it is 1.1 or more, fold cracks are likely to occur. This basis weight ratio is more preferably 0.55 or more, even more preferably 0.60 or more, more preferably 1.05 or less, and even more preferably 1.0 or less.

[0022] (Water-soluble resin layer) The paper substrate of the present invention is provided with a water-soluble resin layer on the outermost layer of the base paper, which is a multilayer paper. The multilayer paper has an uneven surface, but the water-soluble resin layer forms a thick film in the large gap areas where moisture is easily released and a thin film in the small gap areas where moisture is difficult to release, thereby reducing the in-plane variation in water vapor release. Therefore, the paper substrate provided with the water-soluble resin layer can foam the thermoplastic resin layer more uniformly. The water-soluble resin forming the water-soluble resin layer is not particularly limited as long as it is a water-soluble polymer having film-forming properties, and one or more of starches such as starch, oxidized starch, processed starch, etc., polyvinyl alcohols such as fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, modified polyvinyl alcohol, etc., cellulose ethers such as hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, acetyl cellulose, etc., polyacrylamide, etc. may be used. Furthermore, the water-soluble resin layer may contain, as necessary, a water-resistant agent, a paper strength agent, a sizing agent, etc.

[0023] The method for forming the water-soluble resin layer is not particularly limited, and the layer can be formed by a known coater such as a rod coater, a bar coater, a blade coater, an air knife coater, a roll coater, a reverse roll coater, a curtain coater, a slot die coater, a gravure coater, a champlex coater, a brush coater, a slide bead coater, a calendar size press, a gate roll size press, a two-roll or metering blade type size press coater, a bill blade coater, a short dwell coater, a gate roll coater, a nip coater using a calendar, etc. When the water-soluble resin layer is formed, the coater may be either a multi-layer papermaking machine or an on-machine / off-machine type.

[0024] The coating amount (solid content) of the water-soluble resin layer is 0.1 g / m per side. 2 More than 3.0g / m 2 In order to uniformly treat the surface of the paper substrate with such a low coating weight, it is necessary to treat the surface with a coating liquid of low concentration and low viscosity, and it is necessary to maintain the voids in the paper substrate without collapsing them, so it is preferable to use a two-roll size press coater or a gate roll coater.

[0025] (Unfoamed layer) The paper base material for the foamed heat-insulating cup of the present invention has an unfoamed layer made of a thermoplastic resin provided on the water-soluble resin layer. This unfoamed layer foams with water vapor generated from the moisture in the paper base material, thereby becoming a foamed layer, which is a heat-insulating layer. The thermoplastic resin forming the unfoamed layer is not particularly limited as long as it can be laminated and foamed, and both crystalline and non-crystalline thermoplastic resins can be used. Examples of crystalline resins include polyolefin resins such as polyethylene, polypropylene, and polymethylpentene, polyester resins, polyamide, polyacetal, and PPS resin. Examples of non-crystalline resins include polystyrene, polyvinyl chloride, ABS resin, acrylic resin, modified PPE, polycarbonate, polyurethane, polyvinyl acetate, and non-crystalline polyethylene terephthalate (PET). These thermoplastic resins may be used in a single layer of a single resin, or in multiple layers of a single or multiple resins, but a single layer is preferable from the viewpoint of foamability.

[0026] The thermoplastic resin used in the unfoamed layer of the present invention is preferably polyethylene because of its excellent suitability for extrusion lamination and foaming properties. Polyethylene is generally classified into low density polyethylene (density: 0.880 to 0.925 g / cm 3 , melting point: 55℃~120℃), medium density polyethylene (density: 0.925~0.940g / cm 3 , melting point: 115-130℃), high density polyethylene (density: 0.940-0.970g / cm 3 and melting point: 125 to 140° C. In the present invention, low-density polyethylene is preferred because it has particularly excellent suitability for extrusion lamination and foaming property.

[0027] The thickness of the unfoamed layer is preferably 30 μm or more and 80 μm or less. If the thickness of the unfoamed layer is less than 30 μm, a foamed layer of sufficient thickness may not be formed, and if the thickness of the unfoamed layer is more than 80 μm, uniform foaming may be difficult. The unfoamed layer may be one layer or may be composed of two or more layers. When the unfoamed layer is composed of two or more layers, it is preferable that the total thickness of all the unfoamed layers is within the above range.

[0028] (Water vapor barrier layer) A water vapor barrier layer can be formed on the side (innermost layer) opposite the outermost layer of the paper base material. The water vapor barrier layer acts as a lid when the foam layer is formed. The water vapor barrier layer prevents water vapor generated in the multilayer paper from leaking out from the water vapor barrier layer side, allowing most of the water vapor to be ejected from the outermost layer side, making foaming more efficient. The water vapor barrier layer is not particularly limited as long as it prevents leakage (passage) of water vapor. Examples of the water vapor barrier layer include a non-foamed thermoplastic resin layer made of a thermoplastic resin having a higher melting point than the thermoplastic resin forming the unfoamed layer, and a water vapor barrier coating layer containing a water vapor barrier resin and, if necessary, a pigment.

[0029] The lamination method of the unfoamed layer made of thermoplastic resin and the non-foamed thermoplastic resin layer is not particularly limited, and various methods such as extrusion lamination, wet lamination, dry lamination, etc. may be appropriately used for lamination, but the extrusion lamination method is preferred because it provides good adhesion between the paper substrate and the thermoplastic resin. The extrusion lamination method is a method in which a thermoplastic resin is extruded in the form of a molten resin film from a T-die onto a paper substrate, and pressed and bonded while being cooled between a cooling roll and a nip roll facing the same.

[0030] The operating conditions of the extrusion lamination method, i.e., the melting temperature of the thermoplastic resin, lamination speed, etc., may be appropriately set depending on the type of thermoplastic resin and the apparatus used, and are not particularly limited, but in general, the melting temperature is about 200 to 350° C., and the lamination speed is about 50 to 200 m / min. In addition, it is preferable to use a nip roll with a hardness of 70 degrees or more (JIS K-6253), and to perform pressing and bonding by the cooling roll and the opposing nip roll at a linear pressure of 15 kgf / cm or more. Furthermore, in the present invention, when unfoamed layers are laminated, an adhesive resin layer may be sandwiched between the unfoamed layers in order to improve the adhesion between the unfoamed layers, or corona treatment, ozone treatment, or the like may be performed in order to improve the adhesion between the paper base material and the unfoamed layer.

[0031] · Foam insulation paper container A foamed heat-insulating paper container can be made by molding a container using the foamed heat-insulating cup paper base material of the present invention, and then heating the foamed layer to foam the unfoamed layer. The shape of the foamed heat-insulating paper container of the present invention is not particularly limited, but a cup shape having at least a body member and a bottom plate member is preferable. The foamed heat-insulating paper container of the present invention has a unique texture due to the foamed outer surface forming fine irregularities, and can also be used as a packaging container for small items and gifts that do not require heat insulation.

[0032] The method for forming the cup-shaped container having the body member and the bottom plate member is not particularly limited, and can be performed by a known method. The foamed heat-insulating cup paper base material of the present invention can be used for at least one of the body member and the bottom plate member, but is preferably used for the body member that is easily touched by hands, and more preferably used for both the body member and the bottom plate member. EXAMPLES

[0033] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The fiber coarseness and fine fiber content of papermaking fibers were measured using an ABB fiber tester. Canadian Standard Freeness (CSF) was measured in accordance with JIS P8121.

[0034] ·Papermaking fibers For the outermost layer, various LBKPs with different fiber coarseness and beating degree were used. For the other layers, a mixture of the above-mentioned various LBKPs and papermaking broken (average fiber length 0.70-0.76 mm, average fiber width 17.0-17.9 μm, freeness 250-350 ml) was used.

[0035] (Examples and Comparative Examples) To 100 parts by mass of LBKP, a sizing agent (0.7% by mass of papermaking fiber), internally added starch (0.4% by mass of papermaking fiber), and PAM (0.1% by mass of papermaking fiber) were added to obtain an outermost layer paper material. A sizing agent (0.7% by mass of papermaking fiber) was added to 100 parts by mass of a mixed pulp of LBKP and papermaking broken to obtain a paper material for the middle layer (other layer). The outermost layer paper material was used for the innermost layer, and the paper layers were laminated while spraying starch between each layer to obtain a multi-layer paper consisting of three layers: innermost layer / middle layer (other layer) / outermost layer.

[0036] The resulting multilayer paper was coated with polyvinyl alcohol at 0.4 g / m on both sides using a two-roll size press coater. 2 A water-soluble resin layer was formed and the paper substrate was obtained. On one side of the paper substrate, a thermoplastic resin (low density polyethylene, melting point 108°C) was extruded at a melting temperature of 340°C to a thickness of 70μm, and this molten thermoplastic resin and the multilayer paper were pressed and bonded at a linear pressure of 15kgf / cm using a cooling roll and a nip roll with a hardness of 70°C to form an unfoamed layer. Also, a non-foamed thermoplastic resin (medium density polyethylene, melting point 128°C) was extrusion laminated on the other side of the paper substrate at a melting temperature of 320°C to a thickness of 40μm to form a water vapor barrier layer, and foamed heat insulating cup paper substrates in which the paper substrate of Examples 1 to 6 and Comparative Examples 1 to 4 was a multilayer paper were obtained. In addition, as Comparative Examples 5 and 6, a single-layer paper base material was obtained from the outermost layer paper material, and a single-layer paper base material for a foamed heat-insulating cup was obtained in the same manner as above.

[0037] The resulting foamed heat-insulating cup paper base material was subjected to the following measurements and evaluations. The results are shown in Table 1. <Fiber coarseness, fine fiber content, and freeness of defibrated raw material> The multilayer paper obtained was soaked in water at 20°C±5°C for at least 30 minutes, and then each paper layer was separated by hand. 25 g of bone dry pulp from each paper layer was diluted with water (20°C±5°C) to make a total of 1,200 g, and disintegrated in a Tappi disintegrator for 30 minutes to obtain a disintegrated raw material sample. The fiber coarseness and the amount of fine fibers of the obtained disintegrated raw material sample were measured using a fiber tester manufactured by ABB Ltd. In addition, the disintegrated freeness (Canadian standard freeness) of the obtained disintegrated raw material sample was measured in accordance with JIS P8121. <Effervescence (beauty)> A square test piece measuring 100 mm on a side was cut out from the obtained foamed insulating cup paper base material, and the unfoamed layer was foamed using hot air at a heating temperature of 115° C. for a heating time of 6 minutes to form a foamed layer. The surface of the foamed layer after foaming was visually observed, and the foamability (beauty) was evaluated according to the following criteria. : The foaming property is good and the foaming is particularly uniform. ◯: There is no problem with the foaming property, and the foaming is uniform. ×: Poor foaming property, and foaming is uneven.

[0038] <Processing suitability> The occurrence of molding defects (poor shape and wrinkles in the top curl part) when more than 1,000 cups (bottom diameter after body molding is 66 mm, top diameter 95 mm, height 107 mm. Bottom plate part is 68 mm in diameter (fitted and sealed 10 mm from the bottom of the body part). Top curl part is molded into a circle with a diameter of 3 mm and then sealed) using a foam insulation cup paper base material as the body and bottom plate parts were molded were evaluated. ⊚: Almost no molding defects occur during molding (less than 0.3%). ○: The incidence of molding defects during molding is low (less than 1.0%). ×: Molding defects often occur during molding (1.0% or more).

[0039] <Strength suitability> The unfoamed layer of the cups molded for the processing suitability evaluation was foamed using hot air at a heating temperature of 115°C for 6 minutes to produce foamed insulating paper containers. Hot water of 80°C or higher was poured into 10 of these containers up to 80% of the depth, and the condition of the containers after 1 minute was evaluated by touch according to the following criteria. ◎: All containers maintained their shape well and showed almost no deformation when lifted by hand. ◯: All containers maintained their shape and were slightly deformed when lifted by hand, but this did not pose a problem for practical use. ×: The container may deform significantly when lifted by hand, and the contents may leak.

[0040] [Table 1]

[0041] The foamed heat-insulating cup paper base materials obtained in Examples 1 to 6 of the present invention were excellent in foamability, processability, and strength. The foamed heat-insulating cup paper base material obtained in Comparative Examples 1 and 4 had poor foaming properties. In Comparative Example 1, the fiber roughness (outermost layer) was smaller than the fiber roughness (other layers), making it difficult for water vapor to pass through the outermost layer. In Comparative Example 4, both the fiber roughness (outermost layer) and the fiber roughness (other layers) had small values, so there were fewer voids overall and water vapor was less likely to pass through. The foamed heat-insulating cup paper base material obtained in Comparative Example 2 had poor processability. This was because the fibers used in the outermost layer and other layers in Comparative Example 2 were highly coarse and very stiff. The foamed insulating cup paper base materials obtained in Comparative Examples 2 and 3 were inferior in strength suitability. This is believed to be due to the high freeness (other layers) and the insufficient strength of the other layers. The foamed heat-insulating cup paper base material obtained in Comparative Example 5 was inferior in processability and strength. This is thought to be because Comparative Example 5 was a single-layer paper, and the fiber coarseness was large and the paper was very stiff. In addition, the freeness was large, and the strength of the other layers was insufficient. The foaming property of the paper base material for foamed heat-insulating cups obtained in Comparative Example 6 was poor. This is probably because Comparative Example 6 was a single-layer paper, and the fiber coarseness was small, making it difficult for water vapor to pass through the paper layer.

Claims

1. A multi-layered base paper having two or more layers and a water-soluble resin layer on at least one side of the base paper, The multilayer paper has an outermost layer located on the water-soluble resin layer side, and another layer which is any one layer other than the outermost layer, the fiber coarseness (outermost layer) of the raw material obtained by defibrating the outermost layer is greater than the fiber coarseness (other layer) of the raw material obtained by defibrating the other layer, The paper base material for a foamed insulating cup is characterized in that the macerated freeness of the raw material obtained by macerating the outermost layer (outermost layer) is greater than the macerated freeness of the raw material obtained by macerating the other layers (other layers), and the macerated freeness (other layers) is 200 to 500 ml CSF.

2. The paper base material for a foamed heat-insulating cup according to claim 1, characterized in that the fiber roughness (outermost layer) is 50.0 to 70.0 μg / m.

3. The foam insulation cup paper base material according to claim 1, characterized in that the fiber roughness (other layer) is 45.0 to 65.0 μg / m.

4. The paper base material for a foamed heat-insulating cup according to claim 1, characterized in that the macerated freeness (outermost layer) is 250 to 580 ml CSF.

5. 2. The paper substrate for a foamed insulating cup according to claim 1, wherein the basis weight ratio (outermost layer / other layer) between the outermost layer and the other layer is 0.5 or more and less than 1.

1.

6. The foamed heat-insulating cup paper base material according to claim 1, characterized in that the papermaking broken content in the other layer is 20 to 80 mass %.

7. 2. The paper base material for a foamed heat-insulating cup according to claim 1, wherein the amount of fine fibers in the raw material obtained by defibrating the other layer is 15 to 35% by mass.

8. Basis weight: 190-380g / m ２ The foam insulating cup paper substrate according to claim 1,

9. At least one of the body member and the bottom plate member is made of foamed heat insulating paper; The foamed insulating paper comprises a foamed insulating cup paper base material according to any one of claims 1 to 8, and a foamed layer made of a thermoplastic resin formed on a water-soluble resin layer of the foamed insulating cup paper base material. A foamed insulating paper container.

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