Base paper for paper cups

Abstract

To provide base paper for a paper cup reduced in a use amount of plastics and excellent in processing aptitude.SOLUTION: The base paper for a paper cup includes at least one heat seal layer on at least one surface of a paper base material; the heat seal layer includes an ionomer; the heat seal layer has a dry coating amount of 2 to 10 g / m2 as a whole layer; the base paper for a paper cup has a basis weight of 80 g / m2 to 400 g / m2; and the base paper for a paper cup has a latitudinal Taber bending resistance (JIS P-8125-2)) of 1 to 10 mN / m.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a paper cup base paper with reduced plastic usage, and to a paper cup base paper with excellent processing suitability, particularly to a paper cup base paper with excellent heat sealability and top curl processing suitability. [Background technology]

[0002] In recent years, the problem of plastic waste has become more serious. It is said that the world's plastic production exceeds 400 million tons per year, of which a large amount is produced in the packaging container sector, which is the cause of plastic waste. Plastic does not decompose for a long time, and the waste turns into microplastics in the natural environment, causing serious damage to the ecosystem. The most commonly used plastics for packaging containers are polyethylene terephthalate (PET), which is used for drinking cups and bottles, and polyethylene (PE) and polypropylene (PP), which are used for plastic bags and container lamination. Ocean pollution is particularly severe, and it is said that the plastic waste is impossible to recover. In the future, it will be necessary for the global environment to reduce the use of plastics.

[0003] On the other hand, the use of biodegradable plastics that can be completely decomposed by microorganisms has been proposed around the world as a measure against plastic waste. Biodegradable plastics decompose in nature within a certain period of time, but until they decompose they are still waste, and unless their usage and disposal amounts are reduced, this cannot be said to be an immediate solution (see Patent Documents 1 and 2).

[0004] As an immediate countermeasure, for example, replacing plastic with paper has been proposed, and is widely used in paper cups. However, when processing paper into paper cups, a large amount of polyethylene or polypropylene is laminated as a heat sealant. The amount of plastic laminate varies depending on the product concept, but is generally 20 to 50 g / m. 2 and 300 g / m2 Therefore, even in paper cups where plastic has been replaced with paper, the amount of plastic used is still not sufficiently reduced, and there is an urgent need for a means to directly reduce the use of plastic. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-148444 A [Patent Document 2] JP 2013-141763 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a base paper for paper cups which can reduce the amount of plastic used and has, in particular, heat sealing properties and top curl processing suitability. [Means for solving the problem]

[0007] In the present invention, an ionomer is used to reduce the amount of polyethylene or polypropylene used in conventional plastic laminated paper (hereinafter sometimes abbreviated as polylaminated paper). That is, the base paper for paper cups according to the present invention is a base paper for paper cups having at least one heat seal layer on at least one surface of a paper base material, the heat seal layer containing an ionomer, and the coating amount of the heat seal layer is 2 to 10 g / m. 2 The laminated amount of polyethylene or polypropylene used in the heat seal layer of conventional polylaminated paper is 20 g / m 2Compared to the conventional method, which requires more than 10 ...

[0008] In the present invention, the Taber bending resistance (JIS P-8125-2) of the paper cup base paper in the lateral direction is 1 mN·m to 10 mN·m. Since the hot tack of ionomer is lower than that of polyethylene, if the Taber bending resistance exceeds 10 mN·m, poor adhesion occurs during heat sealing (even if the paper is bonded once, the bonded part peels off due to the rigidity of the paper). If it is less than 1 mN·m, the paper cup is too soft.

[0009] The basis weight is 80g / m 2 ~400g / m 2 This makes it difficult for top curl cracks to occur, particularly during processing of paper cups (including paper cups for ice cream).

[0010] The specific volume of the paper cup base paper is 0.8 to 1.8 cm 3 Within this range, it is possible to obtain paper with an appropriate bending resistance for paper cups, which in turn makes it difficult for top curl cracks to occur during processing of paper cups (including paper cups for ice cream).

[0011] It is preferable that the longitudinal tensile breaking elongation of the paper cup base paper (JIS P-8113) is 1% or more. Top curl cracking is likely to occur. This makes top curl cracking less likely to occur, especially during processing of paper cups (including paper cups for ice cream).

[0012] In the paper cup base paper of the present invention, it is preferable that the paper base material is made mainly of pulp, and the beating degree of the pulp is 350 to 420 ml CSF in Canadian Standard Freeness (JIS P 8121:1995 "Testing Method for Pulp Freeness") Within this range, paper with appropriate bending resistance for paper cups can be obtained, which makes it difficult for top curl cracks to occur, particularly during processing into paper cups (including paper cups for ice cream). Effect of the Invention

[0013] The present invention makes it possible to produce paper cup base paper with reduced plastic usage. The paper cup base paper of the present invention can reduce the adverse effects of plastic waste on the natural environment even if it is inappropriately released into the natural world as waste, and can help solve the plastic waste problem. The paper cup base paper of the present invention is excellent for use as, for example, paper cups for hot and iced drinks, food cups for ice cream, and food cups for hot snacks. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Next, the present invention will be described in detail with reference to the embodiments, but the present invention is not limited to these descriptions. Various modifications of the embodiments may be made as long as the effects of the present invention are achieved.

[0015] In this embodiment, the ionomer is a general term for synthetic resins in which polymers are aggregated by utilizing the cohesive force of metal ions, and is a resin in which acrylic acid or methacrylic acid is combined with ethylene or the like. That is, metal salts of ethylene-methacrylic acid copolymers, metal salts of ethylene-acrylic copolymers, metal salts of ethylene-urethane copolymers, metal salts of ethylene-fluorine polymer copolymers, etc. are all called ionomers. Examples of metals that form salts include alkali metal ions and alkaline earth metal ions, specifically, sodium, potassium, calcium, magnesium, and zinc ions. In the present invention, the ionomer is preferably a self-emulsifying emulsion of a metal salt of ethylene-methacrylic acid copolymer. A heat seal layer having sufficient heat seal strength can be provided even when the coating amount of the heat seal layer is relatively small.

[0016] In this embodiment, a heat seal layer can be provided by applying a coating liquid for a heat seal layer containing an ionomer emulsion to at least one side of a paper substrate and drying it. By using an ionomer emulsion, it is possible to control the coating amount to a relatively low level, and further, by using a water-based ionomer emulsion, VOC emissions are eliminated, thereby reducing the burden on the natural environment. The coating amount of the heat seal layer is 2 to 10 g / m2 in terms of solid content per side of the paper substrate. 2 and preferably 3 to 8 g / m 2 2g / m 2 If it is less than 10 g / m, sufficient heat seal strength cannot be obtained. Specifically, the heat seal strength will be less than 145 (gf / 4 mm). 2If it exceeds this value, the quality is excessive in terms of heat seal strength and the effect of reducing plastics is poor. In the paper cup base paper of the present invention, the heat seal layer is usually provided on the entire surface of the paper base material, not only on a part of the surface. In other words, it is preferable that the heat seal layer is provided so as to cover the entire surface of the paper base material, not only on the part required for adhesion by heat sealing, such as in a net, island, or line shape.

[0017] In addition to the ionomer emulsion, various auxiliaries may be added to the heat seal layer coating liquid. For example, viscosity adjusters, defoamers, leveling agents such as surfactants and alcohols, coloring pigments, coloring dyes, etc. However, the addition of these auxiliaries tends to reduce the heat seal strength, so it is preferable to add them in small amounts when they are added. In this embodiment, it is preferable that the heat seal layer coating liquid consists of only the ionomer emulsion.

[0018] The method for applying the coating liquid for the heat seal layer is not particularly limited, and any commonly used coating device can be used, such as an air knife coater, blade coater, gravure coater, rod blade coater, roll coater, reverse roll coater, bar coater, curtain coater, die slot coater, champlex coater, metering blade type size press coater, short dwell coater, spray coater, gate roll coater, lip coater, or other known coating devices.

[0019] In this embodiment, it is preferable that the heat seal layer is formed of two or more layers. By forming two or more layers, the air permeability of the paper cup base paper can be increased, and further, water repellency and oil repellency can be imparted, and properties similar to or close to those of plastic film laminated paper can be obtained. When the heat seal layer is two or more layers, it is preferable that the coating amount of the lowermost heat seal layer closest to the paper substrate is greater than the total coating amount of the other heat seal layers. This is because the air permeability of the paper cup base paper can be further improved, and the water repellency and oil repellency can be further improved.

[0020] The moisture content of the paper cup base paper is preferably 3% to 10%. If it is less than 3%, top curl cracking is likely to occur. If it exceeds 10%, the paper cup is too soft. The moisture content is preferably 4% to 9%. The moisture content can be adjusted by drying the paper cup base paper.

[0021] The specific volume of the paper cup base paper is 0.8 to 1.8 cm 3 If it is less than 0.8, the top curl is likely to break. If it is less than 0.8, the top curl is likely to break, and 3 If the specific volume of the paper cup base paper exceeds 0.9 to 1.7 cm3 / g, the paper cup base paper is too soft. 3 / g.

[0022] In addition, the paper cup base paper of the present invention has a basis weight of 80 g / m 2 ~400g / m 2 Preferably, the paper cup base paper has a basis weight of 180 g / m 2 ~300g / m 2 If the basis weight is within this range, top curl cracking will be eliminated, especially when processing paper cups (including paper cups for ice cream). 2 If the weight exceeds 80 g / m, the material becomes too rigid and the bending resistance increases too much, making it difficult to obtain sufficient adhesive strength during adhesive processing. 2 If it is less than this, the paper cup will not have the bending resistance or strength required.

[0023] The longitudinal tensile breaking elongation of the paper cup base paper (JIS P-8113) is 1% or more. If it is less than 1%, top curl cracking is likely to occur. It is preferably 1.2% or more. In the present invention, the longitudinal direction refers to the longitudinal direction (MD), and the transverse direction refers to the transverse direction (CD).

[0024] In this embodiment, the air permeability of the paper cup base paper is preferably more than 10,000 seconds. More preferably, it is 12,000 seconds or more, and even more preferably, it is 15,000 seconds or more. By making the air permeability of the paper cup base paper 10,000 seconds or more, the barrier property in terms of blocking air is further increased, and the water repellency and oil repellency are further improved. The method for making the air permeability of the paper cup base paper 10,000 seconds or more is not particularly limited, but can be achieved, for example, by using a paper base material with high air permeability. Furthermore, the air permeability of the paper cup base paper can be increased by increasing the smoothness of the surface to which the heat seal coating liquid is applied. This is because pinholes and cracks can be further reduced in the heat seal layer formed thereafter. For example, the smoothness of the surface to which the heat seal coating liquid is applied can be increased by providing a pigment coating layer and then performing a calendaring process or the like. In addition, coating two or more heat seal layers can also have the effect of increasing the air permeability. It is believed that the two-layer coating of the heat seal layer increases air permeability by covering minute pinholes and cracks in the first coating layer (lower layer) with the second coating layer (upper layer) applied on top of the first. Increasing the coating weight of the heat seal layer is also effective in improving air permeability. In terms of film formation of the heat seal layer, air permeability is easily improved by setting the drying temperature after coating of the heat seal layer coating liquid to a temperature above the melting point of the ionomer.

[0025] In this embodiment, the smoothness of the surface of the paper substrate to which the heat seal coating liquid is applied is preferably 10 seconds or more. More preferably, it is 20 seconds or more. The higher the smoothness of the paper substrate, the more uniform the thickness of the heat seal layer applied (fine irregularities are less likely to occur), and as a result, the heat seal strength is less likely to vary, and a uniform heat seal strength can be imparted to the flat surface. The method for increasing the smoothness of the paper substrate is not particularly limited, and examples thereof include calendaring using known calendaring devices such as super calendaring, gloss calendaring, shoe nip calendaring, and soft calendaring. In addition, paper to which the mirror surface of a Yankee dryer, such as one-sided gloss kraft paper, is also suitable as a paper substrate with high smoothness. Note that the heat seal layer may have pinholes or cracks that are invisible to the naked eye, but if they are to that extent, they do not adversely affect the heat sealability. In addition, a leveling agent for preventing pinholes can be added to the heat seal layer coating liquid as long as it does not impair the effects of the present invention.

[0026] The paper base material used in this embodiment is not particularly limited, and a known paper base material containing pulp as a main component can be used. As the pulp that is the main component of the paper base material, chemical pulp such as LBKP (hardwood bleached kraft pulp) and NBKP (softwood bleached kraft pulp), mechanical pulp such as GP (groundwood pulp), PGW (pressurized groundwood pulp), RMP (refiner mechanical pulp), TMP (thermo-mechanical pulp), CTMP (chemi-thermo-mechanical pulp), CMP (chemi-mechanical pulp), and CGP (chemi-ground pulp), wood pulp such as DIP (deinked pulp), and non-wood pulp such as kenaf, bagasse, bamboo, and cotton can be used. These can be used alone or mixed in any ratio. For example, 90 to 100 parts by mass of LBKP (hardwood bleached kraft pulp) can be used as the pulp. On the other hand, in order to minimize top curl cracking and increase strength and bending resistance, it is preferable to blend softwood pulp. For example, it is preferable to use 50 to 95 parts by mass of softwood pulp and 5 to 50 parts by mass of hardwood pulp in the total pulp. Only softwood pulp may be used. Synthetic fibers may be further blended within a range that does not impair the intended effect of the present invention. From the viewpoint of environmental conservation, ECF (Elemental Chlorine Free) pulp, TCF (Total Chlorine Free) pulp, waste paper pulp, and pulp obtained from plantation trees are preferable. For example, the appropriate beating degree of pulp is 200 to 700 mlCSF, for example, 250 to 520 mlCSF, or further 350 to 420 mlCSF in Canadian Standard Freeness (JIS P 8121:1995 "Test Method for Freeness of Pulp"). If the freeness is within this range, it is possible to obtain paper with appropriate bending resistance for use as a paper cup, which makes it less likely for top curl cracking to occur, particularly when processing paper cups (including paper cups for ice cream); on the other hand, if the freeness exceeds 700 ml CSF, the resulting paper may not have sufficient bending resistance and may be too soft for use as a paper cup.

[0027] The paper base material may contain a filler. Examples of the filler include light calcium carbonate, heavy calcium carbonate, talc, clay, kaolin, calcined clay, titanium dioxide, and aluminum hydroxide. The filler content in the paper base material is, for example, 1 to 30 parts by mass per 100 parts by mass of the dry mass of the pulp. For example, light calcium carbonate may be contained in an amount of 1 to 10 parts by mass per 100 parts by mass of the dry mass of the pulp.

[0028] In addition to the pulp and the filler, the paper base material may contain various known papermaking additives. Examples of papermaking additives include water-soluble polymers such as starch, sizing agents, internal paper strength enhancers such as wet paper strength enhancers, bulking agents, retention improvers, drainage improvers, coloring dyes, coloring pigments, fluorescent brighteners, fluorescent decolorizing agents, and pitch control agents. For example, it is preferable to include 0.1 to 1.0 parts by mass of a sizing agent, particularly a rosin sizing agent, and 0.1 to 1.0 parts by mass of starch, particularly a cationic starch, per 100 parts by mass of pulp. In addition, water-soluble polymers such as starch, polyvinyl alcohol, and polyacrylamide may be applied.

[0029] The method for making the paper base material is not particularly limited, and the paper base material can be produced by various paper machines such as a Fourdrinier paper machine, a multi-layer Fourdrinier paper machine, a cylinder paper machine, a multi-layer cylinder paper machine, a multi-layer Fourdrinier cylinder combination paper machine, a twin-wire paper machine, etc. In the present invention, the paper base material may be a single layer or multi-layer paper machine, or a laminate of multiple layers.

[0030] The paper substrate may have one or more coating layers other than the heat seal layer, for example, a pigment coating layer containing a pigment and an adhesive. The pigment in the pigment coating layer may be a known pigment used in the coating layer of a general printing coated paper, for example, calcium carbonate (heavy calcium carbonate, light calcium carbonate, etc.), kaolin (including clay), calcined clay, talc, magnesium carbonate, barium sulfate, calcium sulfate, titanium dioxide, zinc oxide, zinc sulfate, zinc carbonate, calcium silicate, aluminum silicate, magnesium silicate, diatomaceous earth, aluminum hydroxide, magnesium hydroxide, or other inorganic pigments, or acrylic, styrene, vinyl chloride, nylon itself, or organic pigments obtained by copolymerizing these (so-called plastic pigments). For example, a combination of 20 to 40 parts by mass of kaolin and 60 to 80 parts by mass of heavy calcium carbonate may be used as the pigment. The adhesive may be a known adhesive used in the coating layer of a general printing coated paper, for example, starches such as butadiene-based copolymer latex, crosslinking agent modified starch, oxidized starch, enzyme modified starch, esterified starch, etherified starch, cationic starch, amphoteric starch, gelatin, casein, soy protein, water-soluble polymers such as polyvinyl alcohol, vinyl acetate, ethylene vinyl acetate, polyurethane resin, acrylic resin, polyester resin, polyamide resin, and other synthetic resins. The blending ratio of the pigment and adhesive in the pigment coating layer is not particularly limited, but it is preferable to use 5 to 50 parts by weight of adhesive per 100 parts by weight of pigment. For example, the adhesive may be a combination of 1 to 5 parts by weight of phosphate esterified starch and 5 to 15 parts by weight of styrene butadiene latex per 100 parts by weight of pigment. The pigment coating layer may contain various auxiliaries within the range that does not impair the intended effect of the present invention, such as a viscosity regulator, a softener, a gloss imparting agent, a water resistance agent, a dispersant, a flow modifier, an ultraviolet absorber, a stabilizer, an antistatic agent, a crosslinking agent, a sizing agent, a fluorescent whitening agent, a colorant, a pH regulator, an antifoaming agent, a plasticizer, and a preservative. The coating amount of such a pigment coating layer is, for example, 2 to 40 g / m2 in terms of solid content per one side of the paper base material. 2In one embodiment of the paper cup base paper of the present invention, a heat seal layer may be provided on such a pigment coating layer, and in another embodiment, a heat seal layer may be provided on the surface of a paper base material having a pigment coating layer on only one side, the surface not having the pigment coating layer. EXAMPLES

[0031] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" refer to "parts by mass" and "% by mass", respectively, unless otherwise specified. The number of parts added is a value calculated as a solid content.

[0032] Example 1 (Preparation of paper substrate) A paper stock was prepared by adding 100 parts of hardwood bleached kraft pulp with a Canadian Standard Freeness of 400 mlcsf, 5 parts of light calcium carbonate (product name: TP-123, manufactured by Okutama Kogyo Co., Ltd.), 0.2 parts of cationic starch (product name: Neotack 40T, manufactured by Nippon Shokuhin Kako Co., Ltd.), and 0.5 parts of neutral rosin size (product name: Harsize AN-300, manufactured by Harima Kasei Co., Ltd.) and water, and the paper stock was made into a paper with a basis weight of 193 g / m using a fourdrinier multi-cylinder papermaking machine. 2 A base paper of 2 g / m2 was prepared. Oxidized starch (product name: SK-20, manufactured by Nippon Corn Starch Co., Ltd.) was applied to this base paper by a gate roll coater in a dry coating amount of 2 g / m2 on both sides. 2 Apply so that the thickness becomes 195 g / m2 and dry. 2 Thus, a paper substrate of 100 g was obtained.

[0033] (Production of base paper for paper cups) A water-based ionomer emulsion (product name: Chemipearl S-300, manufactured by Mitsui Chemicals, composition: metal salt of ethylene-methacrylic acid copolymer, self-emulsifying emulsion, average particle size by Microtrack method: 0.5 μm) was applied to one side of the paper substrate obtained above at a dry coating amount of 5 g / m 2 The sheet is then coated with an air knife coater so that the sheet has a weight of 200 g / m2 and dried to provide a heat seal layer. 2 The base paper for paper cups was produced. The moisture content was adjusted to 5%.

[0034] Example 2 A base paper for a paper cup was produced in the same manner as in Example 1, except that the pulp was 100 parts of unbleached softwood kraft pulp.

[0035] Example 3 A base paper for a paper cup was produced in the same manner as in Example 1, except that the pulp was changed to 40 parts of softwood kraft pulp and 60 parts of hardwood kraft pulp.

[0036] Example 4 A base paper for a paper cup was prepared in the same manner as in Example 1, except that the amount of cationic starch added was 0.8 parts.

[0037] Example 5 A base paper for a paper cup was prepared in the same manner as in Example 1, except that the Canadian Standard Freeness was changed to 600 cc.

[0038] Example 6 The same paper stock as in Example 1 was prepared as the paper base material, and the first layer was 80 g / m using a cylinder paper machine. 2 , 2nd layer 130g / m 2 , 3rd layer 83g / m 2 , and the basis weight is 293g / m 2 A base paper for a paper cup was prepared in the same manner as in Example 1, except that a paper base material of 2 We produced base paper for paper cups.

[0039] Example 7 A paper cup base paper was produced in the same manner as in Example 1, except that the moisture content of the paper cup base paper was set to 2.5%.

[0040] Comparative Example 1 On one side of the paper substrate prepared in Example 1, low-density polyethylene (Petrothene DLZ19A, manufactured by Tosoh Corporation) was applied in an amount of 30 g / m using an extrusion coater (melt extruder). 2 A heat seal layer was formed by laminating the two sheets so as to obtain a base paper for a paper cup.

[0041] Comparative Example 2 In the preparation of the paper base material of Example 1, 100 parts of softwood bleached kraft pulp with a Canadian Standard Freeness of 250 mlcsf, 5 parts of light calcium carbonate (product name: TP-123, manufactured by Okutama Kogyo Co., Ltd.), 0.6 parts of cationic starch (product name: Neotack 30T, manufactured by Nippon Shokuhin Kako Co., Ltd.), and 0.5 parts of neutral rosin size (product name: Harsize AN-300, manufactured by Harima Kasei Co., Ltd.) were mixed with water to prepare a paper stock, which was then used on a fourdrinier multi-cylinder papermaking machine to obtain a paper stock with a basis weight of 428 g / m 2 A base paper of 2 g / m2 was prepared. Oxidized starch (product name: SK-20, manufactured by Nippon Corn Starch Co., Ltd.) was applied to this base paper by a gate roll coater in a dry coating amount of 2 g / m2 on both sides. 2 Apply so that the thickness becomes 430 g / m2 and dry. 2 A base paper for a paper cup was prepared in the same manner as in Example 1, except that a paper base material of 2 We produced base paper for paper cups.

[0042] The base paper for paper cups obtained in each of the Examples and Comparative Examples was evaluated by the methods described below. The results are shown in Table 1.

[0043] moisture Measurements were performed in accordance with JIS P8127.

[0044] (2) Transverse Taber bending resistance Measurements were performed in accordance with JIS P-8125-2.

[0045] (3) Longitudinal tensile elongation at break Measurements were performed in accordance with JIS P-8113.

[0046] (4) Heat seal strength The obtained paper cup base paper was cut into two pieces with a width of 8 mm and a length of 15 cm, and the front and back sides of the paper cup base paper were overlapped and heat sealed under fixed conditions (adhesive width: 4 mm, temperature: 180°C, pressure: 0.4 MPa, pressing time: 0.5 seconds, pitch: 4 mm) using a heat sealing device (Palmec, model number: PTS-100). Next, the heat sealed sample was subjected to a peel strength test under fixed conditions (peel speed: 100 mm / min, peel length: 10 cm) using a peel strength tester (Shimadzu, model number: Autograph AGS-X) to measure the peel strength, which was determined as the heat seal strength (gf / 4 mm). The higher the value, the better.

[0047] (5) Paper cup processability 1 (cracking of top processing) Paper cups were produced at a speed of 100 cups per minute using a paper cup production machine (heat sealing was used for adhesion). The top curled portion was visually inspected for cracks and rated as follows. ⊚: No cracks at all, practical. Good: There are a few cracks, but it is still usable. △: Cracked and not usable. ×: The cracks are extremely noticeable and the product cannot be used.

[0048] (6) Paper cup processability 2 (side adhesion) Paper cups were produced at a speed of 100 cups per minute using a paper cup manufacturing machine (heat sealing for adhesion). The adhesiveness of the side adhesive was visually inspected and rated as follows. : Completely adhered and practical. ◯: There are some areas where the adhesion is slightly poor, but it is still usable. △: Peeling occurred and it was not practical to use. ×: Significant peeling, not usable. [Table 1]

[0049] In the present invention, examples 1 to 7 of the present invention were able to reduce the amount of plastic used and obtain base paper for paper cups with heat sealability and top curl processing suitability at the same level as polylaminated products. In contrast, when a paper base material with a large basis weight was used, sufficient side adhesion was not obtained due to high lateral Taber bending resistance (Comparative Example 2).

Claims

1. A base paper for paper cups having at least one heat seal layer on at least one surface of a paper base material, the paper base material being mainly composed of pulp, the beating degree of the pulp being 200 to 700 ml CSF in Canadian Standard Freeness (JIS P 8121: 1995 "Testing method for pulp freeness"), the heat seal layer containing an ionomer, and the dry coating amount of the heat seal layer being 2 to 10 g / m2 in total. ２ The paper cup base paper has a basis weight of 80 g / m ２ Up to 400 g / m ２ The paper cup base paper has a Taber bending resistance (JIS P-8125-2) in a lateral direction of 1 mN·m to 10 mN·m, and a moisture content of the paper cup base paper is 3% to 10%.

2. The specific volume of the paper for the paper cup is 0.8 to 1.8 cm ３ The paper cup base paper according to claim 1, characterized in that the viscosity of the paper cup base paper is 1 / g.

3. The paper cup base paper according to claim 1 or 2, characterized in that the paper cup base paper has a longitudinal tensile breaking elongation (JIS P-8113) of 1% or more.

4. The paper cup base paper according to any one of claims 1 to 3, characterized in that the paper base material is composed mainly of pulp, and the beating degree of the pulp is 250 to 520 ml CSF in terms of Canadian Standard Freeness (JIS P 8121:1995 "Testing method for freeness of pulp")

5. The paper cup base paper according to any one of claims 1 to 4, characterized in that the paper base material is mainly composed of pulp and contains only softwood pulp as the pulp, or contains 50 to 95 parts by mass of softwood pulp and 5 to 50 parts by mass of hardwood pulp among the total pulp.

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