Paper container base paper

Abstract

To provide paper container base paper excellent in water resistance and heat sealing property. The paper has an under layer and a top layer on at least one side of a base paper, The under layer contains a first thermoplastic resin and a penetration inhibitor, and has a coating weight (dry mass) of 4 g / m 2 More than 10g / m 2 is as follows: the top layer comprises a second thermoplastic resin and a surfactant; The paper container base paper, wherein the penetration inhibitor is either polyvinyl alcohol (PVA) or polyethylene oxide (PEO), or both.

Description

[Technical Field]

[0001] The present invention relates to paper container base paper. [Background technology]

[0002] Paper container base paper having a heat seal layer on at least one surface of a base paper is used to form paper cups, paper plates, paper trays, etc. Furthermore, as such paper container base paper, one has been proposed in which the amount of plastic used is reduced by laminating only a coating layer without laminating a laminate layer. For example, Patent Document 1 proposes a paper cup base paper that has at least one heat seal layer on at least one surface of a paper base material whose main component is pulp, and the heat seal layer is a coating layer containing an ionomer, thereby reducing the amount of plastic used, having excellent recyclability, and being suitable for processing into three-dimensional paper containers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-040898 Summary of the Invention [Problem to be solved by the invention]

[0004] In paper container base paper in which the heat seal layer is formed from a coating layer, the coating layer must be highly uniform to improve heat sealability. One method for obtaining a highly uniform coating layer is to apply multiple coating layers. As each coating layer is applied, the unevenness of the coating layer surface is smoothed out, resulting in a smoother surface for the upper coating layer. Another method is to add a surfactant. The surfactant smooths the surface of the coating liquid, and the coating layer also becomes smooth after drying. Here, when paper cups were made using paper container base paper in which an under layer was formed by coating and a top layer containing a surfactant was formed on the under layer by coating, it was found that water sometimes seeped in from the end face of the body. Through extensive research, the inventors have discovered that this occurs because the surfactant in the top layer penetrates the under layer and reaches the base paper, reducing the water resistance of the base paper. The present invention has been made to solve the above problems, and has as its object to provide paper container base paper that is excellent in water resistance and heat sealability. [Means for solving the problem]

[0005] The means for solving the problems of the present invention are as follows. 1. A paper substrate having an under layer and a top layer on at least one side thereof, The under layer contains a first thermoplastic resin and a penetration inhibitor, and has a coating weight (dry mass) of 4 g / m 2 More than 10g / m 2 is as follows: the top layer comprises a second thermoplastic resin and a surfactant; The paper container base paper is characterized in that the penetration inhibitor is either polyvinyl alcohol (PVA) or polyethylene oxide (PEO), or both. 2. The paper container base paper described in 1., characterized in that the surfactant is a nonionic surfactant. 3. The paper container base paper according to 2., wherein the nonionic surfactant is an acetylene diol surfactant. 4. The paper container base paper according to any one of 1. to 3., wherein the first thermoplastic resin or the second thermoplastic resin contains either polylactic acid or PHBH, or both. 5. The paper container base paper according to 4., wherein the first thermoplastic resin or the second thermoplastic resin further contains EVA. 6. An underlayer containing a first thermoplastic resin and a penetration inhibitor is applied to one side of the base paper at a coating weight (dry mass) of 4 g / m 2 More than 10g / m 2A first coating process in which coating is performed as follows: a first drying step of drying the under layer; a second coating step of coating a top layer containing a second thermoplastic resin and a surfactant on the under layer; a second drying step of drying the top layer; in this order, The coating liquid in the first coating step contains either polyvinyl alcohol (PVA) or polyethylene oxide (PEO), or both, as a penetration inhibitor, and its water retention is 150 g / m 2 A method for producing paper container base paper, characterized by the following: 7. The first coating process is a post-metering coating method, 6. The method for manufacturing paper container base paper according to 6., wherein the second coating step is a pre-metered coating method. 8. The post-metering coating method is a bar coating method, 7. The method for producing paper container base paper according to 7., wherein the pre-metering coating method is a curtain coating method. [Effects of the Invention]

[0006] The paper container base paper of the present invention is resistant to liquid penetration from the edge of the base paper and has excellent water resistance. The paper container base paper of the present invention has a highly uniform top layer and excellent heat-sealing properties. [Brief explanation of the drawings]

[0007] [Figure 1] 1 shows images of test pieces of the paper container base paper obtained in Examples 1 and 4 and Comparative Example 1 after the Edgewick test. DETAILED DESCRIPTION OF THE INVENTION

[0008] The paper container base paper of the present invention has an under layer and a top layer on at least one side of a base paper, the under layer containing a first thermoplastic resin and a penetration inhibitor, and a coating weight (dry mass) of 4 g / m 2 More than 10g / m 2 is as follows: the top layer comprises a second thermoplastic resin and a surfactant; The penetration inhibitor is either polyvinyl alcohol (PVA), polyethylene oxide (PEO), or both.

[0009] Base paper In the present invention, the base paper is a sheet made of pulp, fillers, various auxiliaries, and the like. Pulp may be any of a variety of known pulps, including bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), bleached hardwood kraft pulp (LBKP), unbleached hardwood kraft pulp (LUKP), and sulfite pulp (SP) and other wood-based chemical pulps; ground pulp (GP), refiner ground pulp (RGP), stone ground pulp (SGP), chemi-ground pulp (CGP), semi-chemical pulp (SCP), thermomechanical pulp (TMP), and chemi-thermomechanical pulp (CTMP); non-wood pulp obtained from kenaf, bagasse, bamboo, hemp, straw, and the like; and recycled paper pulp obtained by removing the ink contained in recycled paper through a deinking process.

[0010] Among these, it is preferable to use chemical pulp made from wood fibers or mechanical pulp made from wood fibers, and it is more preferable to use chemical pulp made from wood fibers, for reasons such as the fact that they are less likely to be contaminated with foreign matter, are less likely to discolor over time when recycled as waste paper raw material, and have a high degree of whiteness, which results in a good surface appearance when printed, making them particularly valuable when used as packaging materials. It is also preferable to use a small amount of recycled paper pulp. Specifically, the ratio of chemical pulp to the total pulp is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and most preferably 100% by mass. It is also preferable that the ratio of recycled paper pulp to the total pulp is 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and most preferably 0% by mass.

[0011] Examples of fillers that can be used include inorganic fillers such as talc, kaolin, calcined kaolin, clay, heavy calcium carbonate, light calcium carbonate, white carbon, zeolite, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, barium sulfate, and calcium sulfate, and organic fillers such as urea-formalin resin, polystyrene resin, phenolic resin, and hollow microparticles. In the present invention, the base paper does not need to contain a filler, and it is preferable not to use a filler.

[0012] Examples of various auxiliaries include various internal sizing agents such as rosin, alkyl ketene dimer (AKD), and alkenyl succinic anhydride (ASA); various nonionic, cationic, and amphoteric retention aids, freeness improvers, paper strength improvers, various starches, polyacrylamide, urea resin, melamine resin, epoxy resin, polyamide resin, polyamide, polyamine resin, polyamine, polyethyleneimine, vegetable gum, polyvinyl alcohol, latex, polyethylene oxide, hydrophilic crosslinked polymer particle dispersions and derivatives or modified products thereof; basic aluminum compounds such as aluminum sulfate, aluminum chloride, sodium aluminate, basic aluminum chloride, and basic polyaluminum hydroxide; water-soluble aluminum compounds such as alumina sol that is easily decomposed in water; polyvalent metal compounds such as ferrous sulfate and ferric sulfate; silica sol, antifoaming agents, coloring dyes, coloring pigments, pH adjusters, pitch control agents, and slime control agents, and these can be appropriately selected and used as needed.

[0013] The surface of the base paper may be treated with various chemicals. Examples of chemicals include oxidized starch, hydroxyethyl etherified starch, enzyme-modified starch, polyacrylamide, polyvinyl alcohol, surface sizing agents, water-resistant agents, water-retention agents, thickeners, and lubricants. These may be used alone or in combination of two or more. Furthermore, these chemicals may be used in combination with pigments. Examples of pigments include inorganic pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, light calcium carbonate, mica, talc, titanium dioxide, barium sulfate, calcium sulfate, zinc oxide, silicic acid, silicates, colloidal silica, and satin white, as well as organic pigments such as solid, hollow, and core-shell pigments, which may be used alone or in combination of two or more.

[0014] The basis weight of the base paper is not particularly limited as long as it is within the range usable as base paper for paper containers. For example, 2 It is preferable that the weight is 150 g / m or more. 2 More preferably, it is 200 g / m or more. 2 The upper limit of the basis weight of the base paper is not particularly limited, but is preferably 500 g / m 2 Preferably, it is 450 g / m or less. 2 More preferably, it is 400 g / m or less. 2 It is even more preferable that:

[0015] The density of the base paper can be selected appropriately depending on the desired quality and handling properties, but is usually 0.5 g / cm 3 More than 1.0g / cm 3 The following are preferred: In the present invention, the base paper may be a paper consisting of only a single paper layer or a multi-layer paper having two or more paper layers. When the base paper is a multi-layer paper, the paper materials, basis weights, etc. of the paper layers may be the same or different.

[0016] The base paper manufacturing (papermaking) method and the type of papermaking machine are not particularly limited, and known manufacturing (papermaking) methods and papermaking machines can be selected, such as a Fourdrinier papermaking machine, a twin-wire papermaking machine, a cylinder papermaking machine, a gap former, a hybrid former (on-top former), and a multilayer papermaking machine that combines these. Furthermore, the pH during papermaking may be in the acidic range (acidic papermaking), pseudo-neutral range (pseudo-neutral papermaking), neutral range (neutral papermaking), or alkaline range (alkaline papermaking), and after papermaking in the acidic range, an alkaline agent may be applied to the surface of the paper base material. Furthermore, when treating the surface of a paper substrate with a chemical, the method of surface treatment is not particularly limited, and known coating devices such as a rod metering size press, a pond type size press, a gate roll coater, a spray coater, a blade coater, and a curtain coater can be used.

[0017] Underlayer, top layer The under layer and the top layer cooperate to exhibit heat-sealability. The underlayer contains a first thermoplastic resin and a penetration inhibitor, and has a coating weight (dry mass) of 4 g / m 2 More than 10g / m 2 and the penetration inhibitor is either polyvinyl alcohol (PVA), polyethylene oxide (PEO), or both. The top layer includes a second thermoplastic resin and a surfactant.

[0018] By making the under layer satisfy the above-described configuration, it is possible to prevent the surfactant contained in the top layer from penetrating the under layer and reaching the base paper, and it is possible to prevent a decrease in water resistance due to the surfactant contained in the top layer. In addition to the thermoplastic resin, the penetration inhibitor contained in the under layer, and the surfactant contained in the top layer, the under layer and the top layer may contain various auxiliaries that are blended into coating solutions in the papermaking field, such as thickeners, dispersants, water retention agents, antifoaming agents, water resistance agents, pH adjusters, UV absorbers, metal salts, lubricants, coloring dyes, pigments, etc. The under layer may also contain a surfactant, and the top layer may also contain a penetration inhibitor.

[0019] The first and second thermoplastic resins may be any known heat-sealable resin without any particular limitations. Examples include polylactic acid (PLA), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polybutylene succinate (PBS), polyvinyl acetate (PVAc), polyvinyl chloride (PVC), ethylene-vinyl acetate resin (EVA), polyolefin resin, acrylic resin, ethylene-acrylic resin, styrene-acrylic resin, and modified versions thereof. One or more of these may be used. The first and second thermoplastic resins may be the same or different. Among these, a biodegradable resin is preferred, PLA or PHBH is more preferred, and PHBH is even more preferred. The biodegradable resin is a resin that can be decomposed by microorganisms into at least water and carbon dioxide, and has an aerobic biodegradability of 50% or more in 6 months, as measured according to ISO-14855-2 (2018). When the underlayer contains PLA or PHBH and EVA, the dry mass ratio (total of 100) of PLA or PHBH:EVA is preferably 50:50 to 99:1 from an environmental perspective, more preferably 70:30 to 99:1, and even more preferably 80:20 to 99:1.

[0020] The under layer contains a penetration inhibitor selected from PVA, PEO, or both. PEO is preferred as a penetration inhibitor because it is effective in smaller amounts and improves adhesion to the top layer. PEO with a viscosity-average molecular weight of 1.1 million to 3.8 million is more preferred, and PEO with a viscosity-average molecular weight of 1.7 million to 2.2 million is even more preferred. The top layer contains a surfactant. The surfactant may be any of anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants, and may be used alone or in combination of two or more. Specific examples of surfactants include silicone-based surfactants, fluorine-based surfactants, alcohol-based surfactants, alkylphenol-based surfactants, ethylene oxide / polyethylene oxide copolymer-based surfactants, acetylene-based surfactants having an acetylene group, acetylene diol-based surfactants having an acetylene group and two hydroxyl groups, alkyl sulfonic acid-based surfactants and dialkyl sulfonic acid-based surfactants having an alkyl group and sulfonic acid, ester-based surfactants, amide-based surfactants, amine-based surfactants, alkyl ether-based surfactants, phenyl ether-based surfactants, sulfate ester-based surfactants, and phenol-based surfactants. Among these, alcohol-based surfactants and acetylene diol-based surfactants are preferred because they can reduce dynamic surface tension with a small amount and are less likely to generate bubbles, with acetylene diol-based surfactants being more preferred.

[0021] The coating amount of the undercoat per side is 4 g / m2 in dry weight. 2 More than 10g / m 2 The coating weight of the underlayer on one side is 4 g / m2 in dry weight. 2 This provides excellent protection against the penetration of surfactants. 2 Above this value, the penetration prevention effect is insufficient, and material costs, energy costs, etc. increase. When PVA is included as a penetration inhibitor, the coating amount of PVA included in the underlayer per side is 0.1 g / m2 in dry mass. 2 More than 0.5g / m 2 When PEO is contained as a penetration inhibitor, the coating amount of PEO contained in the under layer per side is preferably 0.005 g / m2 in terms of dry mass. 2 More than 0.1g / m 2 The following is preferred: When both PVA and PEO are contained, the coating weight of each is preferably within the above range.

[0022] The coating amount per side of the top coat is 10 g / m2 in dry weight. 2 More than 40g / m 2 The coating weight per side is preferably 10 g / m2 or less in dry weight. 2 By using a film having a thickness of 40 g / m or more, excellent heat sealing properties can be exhibited. 2 Above this temperature, the heat sealability is almost saturated and hardly improves any further, and the energy cost and time required for drying increase. The coating amount of surfactant contained in the top layer per side is 0.01 g / m2 in dry mass. 2 More than 0.2g / m 2 The following is preferred:

[0023] The coating method for the under layer and the top layer is not particularly limited, and they can be coated using known coating devices and coating systems. Examples of coating devices include blade coaters, bar coaters, air knife coaters, curtain coaters, spray coaters, roll coaters, reverse roll coaters, size press coaters, and gate roll coaters. Among these, it is preferable to coat the under layer using a post-metering coating method and the top layer using a pre-metering coating method, and it is more preferable to coat the under layer using a bar coating method and the top layer using a curtain coating method. Coating using the post-metering coating method evens out the surface of the coating liquid, forming a flat surface. Coating on top of this using the pre-metering coating method produces a very flat and uniform coating layer.

[0024] The underlayer, top layer, and any optional coating layers are layered in sequence by completing the coating and drying of each layer before coating and drying the next layer. Coating can be done offline, where one layer is coated on the paper surface unwound from the roll, dried, and then wound up on the roll, and this series of steps is repeated to layer all the coating layers. Alternatively, it can be done online, where all layers are layered at once on the paper surface unwound from the roll. In the online method, the coating and drying steps for each layer are simply lined up as a set in the direction the paper runs. The coating system may be either aqueous coating using a solvent such as water or solvent-based coating using a solvent such as an organic solvent, but aqueous coating is preferred from the viewpoint of safety and hygiene. In the case of aqueous coating, a water-dispersible resin or a water-soluble resin is used as the thermoplastic resin, and therefore the heat-sealable coating layer is preferably a coating layer of a water-dispersible resin or a water-soluble resin.

[0025] The coating liquid that forms the underlayer has a water retention of 150 g / m 2 The water retention of a coating solution is a value that indicates how easily the coating solution is absorbed into paper. The lower the water retention value, the less easily the coating solution is absorbed into paper, and the higher the water retention value, the more easily the coating solution is absorbed into paper. 2 A coating solution with a water retention of 125g / m or less is less absorbed by the paper and therefore tends to remain on the surface of the base paper, making it suitable for forming a thick coating layer. 2 Less than 110 g / m 2 Less than 100 g / m is more preferable. 2 More preferably, 90 g / m 2 Even more preferably, 80 g / m 2 Even more preferably, 70 g / m 2 Even more preferably, 60 g / m 2 Even more preferably, 50 g / m 2 Even more preferably, 40 g / m 2 Even more preferably, 30 g / m 2 The lower limit of the water retention is not particularly limited, but it is more preferable to set it below 20 g / m because it will take a long time to dry. 2 More than this is preferable.

[0026] ·Paper paper The paper container base paper of the present invention has excellent water resistance and can be suitably used for applications in which it comes into contact with liquids. For example, it can be used as rods for supporting food such as dumplings, frankfurters, and frozen desserts; edible utensils such as spoons, forks, skewers, toothpicks, and chopsticks; stirring rods such as stirrers and spatulas; food sheets such as paper linings, paper plates, and paper cups; and it is particularly suitable for use in paper cups. [Example]

[0027] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, parts and % in the examples represent parts by mass and % by mass, respectively. (Evaluation method) Water retention The water retention of the undercoat coating solution was measured using an AA-GWR Water Retention Meter Digital Model 250 (Kaltec Scientific). Measurements were taken at 30°C, 50 kPa pressure, 40 seconds, and a liquid volume of 20 ml using the specified film (filter) "AA-GWR Test Filters (Kaltec Scientific), GWR420." The smaller the value, the higher the dynamic water retention. Edgwick The edge wick value is an index of the liquid permeability from the edge of the paper substrate, and can be measured by the following method. A 30mm x 50mm sample was cut from the paper substrate, and water-resistant tape was attached to the front and back of this sample to create a test specimen that liquid would not penetrate from the front and back. The mass of the test specimen before immersion was measured. The test specimen was immersed in a food coloring solution (23°C) prepared by dissolving food coloring in water, and after leaving it for 1 hour, the liquid adhering to the front and back surfaces was thoroughly wiped off, and the change in mass (unit: g) of the test specimen before and after immersion was measured and evaluated. The test specimens after the test in Examples 1 and 4 and Comparative Example 1 are shown in Figure 1. Edgewick value (g) = mass of test piece after immersion (g) - mass of test piece before immersion (g)

[0028] ·Bending resistance The bottom part of the paper cup is made by hand using a POM draw die and draw punch. Conditions: The sample evaluation surface was placed on the draw die side, the clearance between the draw die and the draw punch was 250 μm, drawing was performed, and a paper cup bottom part with a bottom surface diameter of 600 mm and a skirt length of approximately 5 mm was produced. Next, a 2% brilliant blue dye solution adjusted to a surface tension of 29.6 mN / m using Tipol Eight (a surfactant) was applied to the bottom bend and bottom surface, left to stand for 30 seconds, then wiped off with a JK wiper, and the penetration was evaluated according to the following criteria: A rating of 5 to 3 means there is no problem in practical use. 5: No penetration. 4: Penetration into the surface of the top layer and the base paper layer was confirmed in less than 5% of the bent area. 3: Penetration into the surface of the top layer and the base paper layer was confirmed in 5% to less than 30% of the bent area. 2: Penetration into the surface of the top layer and the base paper layer was confirmed in 30% to less than 70% of the bent area. 1: Penetration into the surface of the top layer and the base paper layer was confirmed in more than 70% of the bent area.

[0029] Adhesion Using a cutter blade, make an X-shaped cut to a depth of 1 mm or less on the surface of the top layer, and peel it outward from the center of the X (the intersection), resulting in a triangular sheet. The surface of the top layer was peeled off by hand from the cut at the intersection, and the feeling of force felt when peeling and the state after peeling were visually confirmed (if the base paper layer, under layer, and top layer are all sufficiently adhered, material breakage occurs, and if the adhesion between the base paper layer and under layer or between the under layer and top layer is weak, peeling occurs at the interface where adhesion is weak), and evaluated according to the following criteria. [Evaluation criteria] 5: Material failure occurs (the base paper is destroyed). 4: Partial failure occurs (base paper is destroyed). 3: There is a strong resistance, but no breakage occurs. 2: There is some resistance, but it can be easily peeled off. 1: Can be peeled off very easily without any resistance. ·Hot water resistance Hot water cobb60 was measured at two random points on the coating surface using the Cobb method in accordance with JIS P8140:1998 Paper and paperboard - Water absorption test method. The measurement was performed with water at 90°C and a contact time of 60 seconds. The average value of the two measurements was used as the hot water resistance value.

[0030] (material) paper base material Cup base paper: Nippon Paper Industries Co., Ltd., CUP-HD, basis weight 220 g / m 2 thermoplastic resin PHBH: Kaneka Corporation, mass average molecular weight 600,000 EVA: Sumika Chemtex Co., Ltd., Sumika Flex S-355HQ Penetration inhibitor PVA: Kuraray Co., Ltd., RS-2117 PEO: Sumitomo Seika Chemicals Co., Ltd., PEO-8, viscosity average molecular weight 1.7 million to 2.2 million surfactants Surfynol 440 (acetylene diol-based nonionic surfactant), manufactured by Nissin Chemical Industry Co., Ltd.

[0031] ·Paper container base paper manufacturing The thermoplastic resin and the penetration inhibitor were mixed and stirred in the parts by mass shown in Table 1 to obtain a coating liquid for an under layer having a solid content concentration of 49% by mass. The thermoplastic resin, penetration inhibitor, and surfactant were mixed and stirred in the parts by mass shown in Table 1 to obtain a top layer coating liquid with a solids concentration of 48% by mass. The coating liquid for the underlayer was applied to one side of the paper substrate and dried at 105°C for 1 minute. The coating liquid for the heat-sealable coating layer was applied to this coated side in a dry weight of 23 g / m 2 The paper was then dried at 105°C for 1 minute to obtain paper container base paper. The undercoating and top layer coating were each carried out using an actual coating machine at a coating speed of 100m / min.

[0032] [Table 1]

[0033] Comparative Example 1 is an example in which only a thermoplastic resin was applied as the under layer. Comparative Examples 2 and 3 are examples in which only a penetration inhibitor was applied as the under layer. Comparative Examples 1-3 confirmed that in order for the under layer to prevent the penetration of the surfactant in the top layer, the under layer must contain both a thermoplastic resin and a penetration inhibitor. In Comparative Examples 2 and 3, the under layer penetrated into the fiber surface of the uneven base paper or into the gaps between the fibers, preventing the penetration inhibitor from being uniformly distributed in the planar direction of the base paper surface. This is thought to have made it difficult for the penetration inhibitor to be uniformly distributed in the horizontal direction, resulting in the surfactant in the top layer penetrating. Compared with Comparative Example 1-3, Example 1-5 had a smaller Edge Wick value, and was able to prevent a decrease in water resistance due to penetration of the surfactant. In the Examples, the water retention of the undercoating liquid was high (the water retention value was small), so the underlayer was more likely to remain on the surface of the base paper and was dried in this state during the drying process. This is thought to have enabled the penetration inhibitor to be distributed more uniformly in the planar direction of the surface of the base paper like a wall, resulting in an effect of preventing penetration of the top layer coating liquid. It was also confirmed that the bending resistance and adhesion were equally good whether PEO or PVA was used as the penetration inhibitor.

Claims

1. An under layer and a top layer are provided on at least one side of a base paper; The under layer contains a first thermoplastic resin and a penetration inhibitor, and has a coating weight (dry mass) of 4 g / m ２ 10g / m or more ２ is as follows: the top layer comprises a second thermoplastic resin and a surfactant; The paper container base paper is characterized in that the penetration inhibitor is either polyvinyl alcohol (PVA) or polyethylene oxide (PEO), or both.

2. The paper container base paper according to claim 1, wherein the surfactant is a nonionic surfactant.

3. 3. The paper container base paper according to claim 2, wherein the nonionic surfactant is an acetylene diol surfactant.

4. The paper container base paper according to claim 3, wherein the first thermoplastic resin or the second thermoplastic resin contains either polylactic acid or PHBH, or both.

5. The paper container base paper according to claim 4, wherein the first thermoplastic resin or the second thermoplastic resin further comprises EVA.

6. An underlayer containing a first thermoplastic resin and a penetration inhibitor was coated on one side of the base paper in a coating amount (dry mass) of 4 g / m ２ 10g / m or more ２ A first coating step of coating as follows: a first drying step of drying the under layer; a second coating step of coating a top layer containing a second thermoplastic resin and a surfactant on the under layer; a second drying step of drying the top layer; in this order, The coating liquid in the first coating step contains either polyvinyl alcohol (PVA) or polyethylene oxide (PEO), or both, as a penetration inhibitor, and the water retention is 150 g / m ２ A method for producing paper container base paper, characterized by the following:

7. The first coating step is a post-metering coating method, The method for manufacturing paper container base paper according to claim 6, wherein the second coating step is a pre-metered coating method.

8. the post-metering coating method is a bar coating method, The method for manufacturing paper container base paper according to claim 7, wherein the pre-metering coating method is a curtain coating method.

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