Method for manufacturing paper packaging material, coating composition, and paper laminate

Abstract

To provide a method for producing a paper-made packaging material with improved heat seal strength from a paint composition containing an aqueous dispersion of an ethylene-acrylic acid copolymer, the paint composition, and a paper-made laminate having heat sealing properties.SOLUTION: The present invention relates to a method for producing a paper-made packaging material, in which a paint composition is formed using isopropyl alcohol as a diluent of an ethylene-acrylic acid copolymer water dispersion, and a heat seal layer is formed from the paint composition to obtain a paper-made laminate.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a paper packaging material, a coating composition, and a paper laminate. More specifically, the present invention relates to a method for producing a paper packaging material having heat-sealing properties, a coating composition, and a paper laminate having heat-sealing properties. [Background technology]

[0002] In recent years, as there has been a growing demand to move away from plastic in response to environmental concerns, there has been a demand in the food packaging industry to switch from plastic to paper.

[0003] However, since packaging materials made of paper alone do not have heat-sealing properties, techniques for imparting heat-sealing properties to paper substrates for the purpose of sealing the contents and processing the packaging materials have been investigated.

[0004] One known method for imparting heat sealability to paper packaging materials is to laminate a sealant film having heat sealability, such as a carbon-containing polypropylene (CPP) film or a linear low-density polyethylene (LLDPE) film, onto the paper substrate.

[0005] However, the above-mentioned sealant film requires a certain thickness in order to function as a film, and in a situation where there is a demand for a shift from plastic to paper, its contribution to reducing the amount of plastic is small, making it an undesirable embodiment.

[0006] Therefore, as an alternative means of imparting heat-sealing properties to paper packaging materials, which is expected to reduce the amount of plastic used compared to the method of applying a sealant film, a method has been proposed in which a paint is applied to the paper base material to form a heat-sealing layer.

[0007] For example, Patent Document 1 describes a moisture-proof paper in which a heat-sealing layer is formed by applying a coating liquid containing an inorganic layered compound and an ethylene-acrylic copolymer and exhibiting water vapor barrier properties and heat-sealing properties to a paper substrate. In the examples, the coating liquid is prepared by adding an aqueous dispersion of an ethylene-acrylic copolymer to an aqueous dispersion of an inorganic layered compound, and further adding a modified polyamide resin, an aqueous ammonia solution, and dilution water.

[0008] As disclosed in Non-Patent Document 1, it is known that the viscosity of an aqueous alcohol solution changes depending on the molar fraction of the alcohol, and that the viscosity depends non-linearly on the molar fraction of the alcohol. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2020-190063 A [Non-patent literature]

[0010] [Non-Patent Document 1] The microscopic viscosity of water-alcohol binary solvents studied by ultrafast spectroscopy utilizing diffusive phenyl ring rotation of malachite green as a probe,Y.Nagasawa,Y.Nakagawa,A.Nagafuji,T.Okada,and H. Miyasaka,Journal of Molecular Structure,735-736C,p.217-223(2005) Summary of the Invention [Problem to be solved by the invention]

[0011] According to the method described in Patent Document 1, a paper packaging material having heat sealability can be produced without using a plastic sealant film. However, the method is still not satisfactory for products that require a higher heat seal strength.

[0012] The present invention has been made in view of the above-mentioned background, and an object of the present invention is to provide a method for producing a paper packaging material with improved heat seal strength from a coating composition containing an ethylene-acrylic acid copolymer aqueous dispersion, the coating composition, and a paper laminate having heat sealability. [Means for solving the problem]

[0013] The present inventors have conducted extensive research to solve the above problems. As a result, they have found that the heat seal strength of the resulting paper packaging material can be improved by forming a coating composition using isopropyl alcohol as a diluent for an ethylene-acrylic acid copolymer aqueous dispersion and forming a heat seal layer from the coating composition, and have completed the present invention. That is, the present invention is as follows.

[0014] Aspect 1 A method for producing a paper packaging material having a paper base material and a heat seal layer, comprising: an aqueous dispersion of an ethylene-acrylic acid copolymer; Isopropyl alcohol, applying to the paper substrate a coating composition comprising The viscosity of the coating composition is equal to or greater than the viscosity of a composition identical to the coating composition except that it does not contain the isopropyl alcohol. A method for manufacturing paper packaging materials. Aspect 2 2. The method for producing a paper packaging material according to claim 1, wherein the ethylene-acrylic acid copolymer is an ethylene-methacrylic acid copolymer. Aspect 3 A method for producing a paper packaging material according to aspect 1 or 2, wherein the paper base material is kraft paper. Aspect 4 The method for producing a paper packaging material according to any one of Aspects 1 to 3, wherein the ratio of the isopropyl alcohol in the coating composition is 5 to 60 parts by mass per 100 parts by mass of water constituting the coating composition. Aspect 5 5. The method for producing a paper packaging material according to aspect 4, wherein the ratio of the isopropyl alcohol in the coating composition is 15 to 40 parts by mass per 100 parts by mass of water constituting the coating composition. Aspect 6 A coating composition for forming a heat seal layer on a paper substrate, comprising: an aqueous dispersion of an ethylene-acrylic acid copolymer; Isopropyl alcohol, Including, The viscosity of the coating composition is equal to or greater than the viscosity of a composition identical to the coating composition except that it does not contain the isopropyl alcohol. Paint composition. Aspect 7 7. The coating composition of claim 6, wherein the ethylene-acrylic acid copolymer is an ethylene-methacrylic acid copolymer. Aspect 8 8. The coating composition of claim 6 or 7, wherein the paper substrate is kraft paper. Aspect 9: A coating composition according to any one of aspects 6 to 8, wherein the ratio of the isopropyl alcohol in the coating composition is 5 to 60 parts by mass per 100 parts by mass of water constituting the coating composition. Aspect 10 A coating composition according to aspect 9, wherein the ratio of the isopropyl alcohol in the coating composition is 15 to 40 parts by mass per 100 parts by mass of water constituting the coating composition. Aspect 11 A paper substrate; A heat seal layer formed from the coating composition according to any one of aspects 6 to 10; A paper laminate comprising: Aspect 12 12. The paper laminate according to claim 11, which is a packaging material. Effect of the Invention

[0015] According to the method for producing a paper packaging material of the present invention, a paper packaging material having excellent heat seal strength can be produced.

[0016] Furthermore, the paper laminate of the present invention is a laminate of a paper base material having excellent heat seal strength.

[0017] Therefore, the paper packaging material obtained by the paper packaging material manufacturing method of the present invention and the paper laminate of the present invention can be used to produce various packages with excellent heat seal strength by thermally welding the heat seal layers together or between the heat seal layers and other materials. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 《Paint composition》 The coating composition of the present invention is a coating composition used for forming a heat seal layer on a paper substrate, and contains an aqueous dispersion of an ethylene-acrylic acid copolymer and isopropyl alcohol. The coating composition only needs to contain the ethylene-acrylic acid copolymer, water, and isopropyl alcohol as essential components, and may contain other components as necessary.

[0019] The viscosity of the coating composition of the present invention is equal to or greater than the viscosity of the same coating composition except that it does not contain isopropyl alcohol.

[0020] <Water dispersion of ethylene-acrylic acid copolymer> The aqueous dispersion of the ethylene-acrylic acid copolymer is a dispersion of the ethylene-acrylic acid copolymer in water as a medium. The form of the dispersion of the ethylene-acrylic acid copolymer is not particularly limited, but may be, for example, an emulsion dispersion.

[0021] The ethylene-acrylic acid copolymer is a copolymer of ethylene and a (meth)acrylic monomer. Here, (meth)acrylic means methacrylic acid and acrylic acid. The ethylene-acrylic acid copolymer used in the present invention may contain a small amount of other monomers copolymerizable with ethylene and the (meth)acrylic monomer.

[0022] Examples of the (meth)acrylic acid monomer include (meth)acrylic acid and its alkyl esters. The number of carbon atoms in the alkyl group of the ester moiety of the (meth)acrylic acid alkyl ester may be 1 or more, and may be 8 or less, 6 or less, or 4 or less.

[0023] As the acrylic monomer of the ethylene-acrylic acid copolymer used in the present invention, acrylic acid or methacrylic acid is preferred, with methacrylic acid being particularly preferred.

[0024] Examples of the ethylene-acrylic acid copolymer include ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl acrylate copolymer, and ethylene-butyl methacrylate copolymer, etc. In the present invention, one or more of these may be used.

[0025] As the ethylene-acrylic acid copolymer used in the present invention, among others, an ethylene-acrylic acid copolymer or an ethylene-methacrylic acid copolymer is preferable, and an ethylene-methacrylic acid copolymer is particularly preferable.

[0026] As the aqueous dispersion of ethylene-methacrylic acid copolymer, a commercially available product can be used, for example, Aquatex (registered trademark) AC-3100 (Japan Coating Resins Co., Ltd.).

[0027] Ethylene-methacrylic acid copolymer is a resin that exhibits heat sealability. It also has excellent adhesion to paper. Therefore, in the present invention, a paper packaging material having excellent adhesion between the paper base material and the heat seal layer can be realized.

[0028] <Isopropyl alcohol> Isopropyl alcohol, which is a component of the coating composition, is a secondary alcohol having three carbon atoms and is also called 2-propanol.

[0029] The viscosity of the coating composition of the present invention is equal to or greater than the viscosity of a composition identical to the coating composition except that it does not contain isopropyl alcohol, i.e., the viscosity of the coating composition of the present invention is increased by the addition of isopropyl alcohol as a component of the coating composition.

[0030] As disclosed in Non-Patent Document 1, it is known that the viscosity of an alcohol aqueous solution changes depending on the molar fraction of the alcohol, and that the viscosity depends non-linearly on the molar fraction of the alcohol.

[0031] The viscosity of aqueous solutions of ethanol (EtOH), propanol (1-PrOH), and isopropyl alcohol (2-PrOH) reaches a maximum when the mole fraction of alcohol is around 0.2 to 0.3. This is thought to be due to "hydrophobic hydration," that is, when alcohol forms clusters in the aqueous solution, water molecules form hydrogen bonds around the alcohol molecules that have gathered together due to hydrophobic interactions to form a cage-like structure.

[0032] When the alcohol concentration increases beyond a molar fraction of 0.2 to 0.3, the viscosity of the aqueous alcohol solution decreases.

[0033] The coating composition of the present invention changes its viscosity depending on the concentration of isopropyl alcohol due to the phenomenon described above, by adding isopropyl alcohol to water, which is the medium for the aqueous dispersion of the ethylene-acrylic acid copolymer. As the amount of isopropyl alcohol added increases, the viscosity rises and approaches a maximum value, and when the concentration of isopropyl alcohol exceeds the maximum value, the viscosity of the coating composition decreases.

[0034] The coating composition of the present invention has a viscosity equal to or higher than that of the same composition as the coating composition except that it does not contain isopropyl alcohol, and therefore can improve the heat seal strength of the heat seal layer formed by applying the coating composition onto a paper substrate. This is believed to be because the increased viscosity of the coating composition suppresses the penetration of the coating composition into the paper substrate, i.e., the substrate into which the coating composition is easily permeated, and as a result, a heat seal layer of appropriate thickness can be formed on the paper substrate. In addition, isopropanol used to increase the viscosity is also preferable in that it can be easily removed together with water by evaporation after the coating composition is applied.

[0035] (Composition of isopropyl alcohol and water in paint composition) In the medium constituting the coating composition, the composition of isopropyl alcohol and water is not particularly limited, so long as the ratio is such that the viscosity of the coating composition is greater than the viscosity of a composition identical to the coating composition except that it does not contain isopropyl alcohol.

[0036] The ratio of isopropyl alcohol in the coating composition may be, for example, 5 to 60 parts by mass per 100 parts by mass of water constituting the coating composition.

[0037] The proportion of isopropyl alcohol in the paint composition may be 8 mass% or more, 10 mass% or more, 12 mass% or more, 15 mass% or more, 18 mass% or more, 20 mass% or more, 25 mass% or more, or 30 mass% or more, and may be 55 mass% or less, 50 mass% or less, 45 mass% or less, 40 mass% or less, 37 mass% or less, 35 mass% or less, 33 mass% or less, or 30 mass% or less, relative to 100 mass parts of water that constitutes the paint composition.

[0038] In particular, the ratio of isopropyl alcohol in the coating composition may be 15 to 40 parts by mass per 100 parts by mass of water constituting the coating composition.

[0039] (Ethylene in paint composition a Acrylic acid copolymer composition Ethylene in coating compositions a The composition of the acrylic acid copolymer is not particularly limited as long as it is contained in an amount that allows the coating composition to be evenly applied onto the paper substrate, and may be, for example, 30 to 50% by mass in terms of solid content.

[0040] <<Method for manufacturing paper packaging material>> The method for producing a paper packaging material of the present invention is a method for producing a paper packaging material comprising a paper substrate and a heat seal layer. The heat seal layer is formed by applying the above-mentioned coating composition to the paper substrate. In the present invention, the coating composition contains an aqueous dispersion of an ethylene-acrylic acid copolymer and isopropyl alcohol, and the viscosity of the coating composition is made higher than the viscosity of a composition identical to the coating composition except that it does not contain isopropyl alcohol.

[0041] <Paper base material> The paper base material used in the present invention is not particularly limited as long as it is made by bonding plant fibers or other fibers. Among them, those containing plant-derived pulp as the main component can satisfy the demand for environmental friendliness.

[0042] Examples of the paper substrate used in the present invention include fine paper, medium-quality paper, lightly coated paper, coated paper, one-sided glossy paper, bleached or unbleached kraft paper, etc. Among them, kraft paper is preferred because it has sufficient strength when used for packaging purposes and can be appropriately impregnated with a coating composition containing an aqueous dispersion of an ethylene-acrylic acid copolymer and isopropyl alcohol.

[0043] <Method of applying coating composition> The method for producing a paper packaging material of the present invention includes applying a coating composition to a paper substrate, thereby producing a paper packaging material comprising a paper substrate and a heat seal layer.

[0044] The method for applying the coating composition to the paper substrate is not particularly limited, and any known method can be used, such as a method using a coating device such as an air knife coater, a blade coater, a gravure coater, a roll coater, a reverse roll coater, a bar coater, or a spray coater.

[0045] The amount of the coating composition applied to the paper substrate is not particularly limited and can be appropriately set depending on the application. In order to impart sufficient heat sealability, for example, the coating film should have a dry mass of 2 g / m 2 The coating amount is 3 g / m2 in terms of dry weight when the coating is formed. 2 More than 4g / m 2 More than 5g / m 2 More than 8g / m 2 More than 10g / m 2 It may be more than that.

[0046] <Paper laminate> The paper laminate of the present invention includes a paper substrate and a heat seal layer formed from the coating composition of the present invention. The heat seal layer is formed by applying the coating composition of the present invention to the paper substrate, and includes an ethylene-acrylic acid copolymer.

[0047] <Paper base material> The paper base material constituting the paper laminate of the present invention is the same as the paper base material that can be applied to the above-mentioned method for producing a paper packaging material of the present invention.

[0048] <Heat seal layer> The heat seal layer in the paper laminate of the present invention is formed from the coating composition of the present invention and contains an ethylene-acrylic acid copolymer.

[0049] <Other layers> The paper laminate of the present invention may have other layers as long as it contains a paper substrate and a heat seal layer formed from the coating composition of the present invention as essential layers. The other layers are not particularly limited, and examples thereof include a barrier layer for imparting barrier properties against oxygen and water vapor, a reinforcing layer for reinforcing strength, and an adhesive layer for bonding between layers.

[0050] In the paper laminate of the present invention, any layer other than the essential constituent layers of the paper substrate and the heat seal layer containing an ethylene-acrylic acid copolymer can be disposed, for example, between the paper substrate and the heat seal layer, or on the outside of the paper substrate.

[0051] Examples of the barrier layer include layers made of ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC), nylon (NY), or polyacrylonitrile (PAN), which exhibit a function of blocking gases such as oxygen and water vapor.

[0052] Examples of materials for the reinforcing layer include paper, synthetic paper, nonwoven fabric, etc. These may be coated with an adhesive to provide adhesion to adjacent layers.

[0053] Examples of adhesive layers for bonding layers include layers made of ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), and ionomer.

[0054] The resins constituting the other layers may be one type or a blend of two or more types. In addition, additives for imparting functionality, etc. may be blended as necessary.

[0055] (Printing layer) The paper laminate of the present invention may have a printed layer on the side of the paper substrate opposite to the heat seal layer. The printed layer may have a known structure, for example, a layer containing a resin and a pigment.

[0056] (Other layer stacking methods) In the paper laminate of the present invention, the method for laminating layers other than the paper base material and the heat seal layer is not particularly limited, and any known method can be used, such as dry lamination, hot melt lamination, extrusion lamination, and sandwich lamination.

[0057] <Applications of paper laminates> The use of the paper laminate of the present invention is not particularly limited. It can be used for various purposes that require heat sealability, for example, as a packaging material. In particular, when it is applied to food packaging that requires heat sealability, it can satisfy environmental requirements because it is a paper packaging material. EXAMPLES

[0058] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0059] <Material> In the examples and comparative examples, the following materials were prepared as materials constituting layers.

[0060] (1)Paper base material Single-sided glazed bleached kraft paper (OK Blizzard 60g / m 2 (manufactured by Oji Materia Co., Ltd.) (2) Water dispersion of ethylene-acrylic acid copolymer Water-dispersed ethylene Meta Acrylic acid copolymer emulsion (Aquatex (registered trademark) AC-3100, manufactured by Japan Coating Resins Co., Ltd., solid content = 44.5 mass%, viscosity = 220 mPa s, pH = 4.7) (3) Isopropyl alcohol Isopropyl alcohol (manufactured by Taishin Chemical Co., Ltd.) (4) Methanol 100% (manufactured by Taishin Chemical Co., Ltd.)

[0061] <Example 1> (Preparation of coating composition) Water-dispersed ethylene Meta A coating composition was prepared by adding 10 parts by mass of isopropyl alcohol (manufactured by Taishin Chemical Co., Ltd.) to 100 parts by mass of acrylic acid copolymer emulsion (Aquatex (registered trademark) AC-3100, manufactured by Japan Coating Resins Co., Ltd.) and thoroughly stirring using a stirrer.

[0062] The viscosity of the resulting coating composition was 280 mPa s. The solid content of the ethylene-acrylic acid copolymer was 40.5 mass %, and the ratio of isopropyl alcohol to 100 mass parts of water constituting the coating composition was 18.0 mass parts.

[0063] (Preparation of paper laminate) Single-sided glazed bleached kraft paper (OK Blizzard 60g / m 2 The coating composition obtained above was applied to a paper substrate (manufactured by Oji Materia Co., Ltd.) and dried to obtain a paper laminate comprising a paper substrate and a heat seal layer. The coating amount of the coating composition was 3.5 g / m2 in terms of dry mass. 2 The coating was carried out using a gravure printing multi-proofing machine (Gravure Proof Multi, Nissho Gravure) with a 130 line 38μ gravure plate set at an operating speed of 40 m / min.

[0064] <Example 2> Water-dispersed ethylene MetaA coating composition was prepared by adding 20 parts by mass of isopropyl alcohol (manufactured by Toyo Ink Co., Ltd.) to 100 parts by mass of an acrylic acid copolymer emulsion (Aquatex (registered trademark) AC-3100, Japan Coating Resin Co., Ltd.), and the coating amount of the coating composition was 3.6 g / m2 in terms of dry mass. 2 Except for the above, a coating composition was formed and a paper laminate was produced in the same manner as in Example 1.

[0065] The viscosity of the resulting coating composition was 460 mPa s. The solid content of the ethylene-acrylic acid copolymer was 37.1 mass %, and the ratio of isopropyl alcohol to 100 mass parts of water constituting the coating composition was 36.0 mass parts.

[0066] <Example 3> Water-dispersed ethylene Meta A coating composition was prepared by adding 30 parts by mass of isopropyl alcohol (manufactured by Toyo Ink Co., Ltd.) to 100 parts by mass of an acrylic acid copolymer emulsion (Aquatex (registered trademark) AC-3100, Japan Coating Resin Co., Ltd.), and the coating amount of the coating composition was 3.5 g / m2 in terms of dry mass. 2 Except for the above, a coating composition was formed and a paper laminate was produced in the same manner as in Example 1.

[0067] The viscosity of the resulting coating composition was 840 mPa s. The solid content of the ethylene-acrylic acid copolymer was 34.2 mass%, and the ratio of isopropyl alcohol to 100 mass parts of water constituting the coating composition was 54.1 mass parts.

[0068] <Evaluation> (Heat seal strength measurement) The heat seal layers of the paper laminate obtained above were placed facing each other and heat sealed to each other under the following conditions. Equipment used: Seal tester TP-701-B (Tester Industry) Seal width: 20mm Bar thickness: 10mm Sealing pressure: 0.23MPa Sealing temperature: 120℃ and 140℃ Seal time: 0.5 seconds

[0069] Next, the heat-sealed samples were subjected to interlayer peeling and the interlayer strength of the peeled surface was measured. A Strograph VGS05E (Toyo Seiki) was used as the measuring device for the measurement, and the maximum peel strength at a peel length of 10 mm was calculated when the samples were peeled at 180° under conditions of 300 mm / min and a peel length of 10 mm. The measurement was performed in an environment of 23°C and 60 RH%. The measurement results are shown in Table 1.

[0070] <Comparative Example 1> Water-dispersed ethylene Meta An acrylic acid copolymer emulsion (Aquatex (registered trademark) AC-3100, Japan Coating Resin) was used as is without dilution to prepare a coating composition, and the coating amount of the coating composition was 4.8 g / m2 in terms of dry mass. 2 A paper laminate was produced in the same manner as in Example 1 except for the above, and the heat seal strength was measured.

[0071] The viscosity of the coating composition was 220 mPa·s, and the solid content of the ethylene-acrylic acid copolymer was 44.5 mass %. The results are shown in Table 1.

[0072] <Comparative Examples 2 to 4> (Preparation of coating composition) Water-dispersed ethylene Meta A coating composition was prepared by adding the amount of water shown in Table 1 to 100 parts by mass of an acrylic acid copolymer emulsion (Aquatex (registered trademark) AC-3100, Japan Coating Resin) and thoroughly stirring the mixture using a stirrer.

[0073] (Preparation of paper laminate) The obtained coating composition was applied to a one-sided glazed bleached kraft paper (OK Blizzard 60 g / m 2 A paper laminate was obtained by applying the coating amount shown in Table 1 to a sheet of paper (manufactured by Oji Materia Co., Ltd.) and drying it. Then, in the same manner as in Example 1, the heat seal strength of the obtained paper laminate was measured.

[0074] The viscosity of the resulting coating composition, the coating amount of the coating composition, and the heat seal strength are shown in Table 1.

[0075] [Table 1]

Claims

1. A method for producing a paper packaging material having a paper base material and a heat seal layer, comprising: an aqueous dispersion of an ethylene-acrylic acid copolymer; Isopropyl alcohol, applying to the paper substrate a coating composition comprising The viscosity of the coating composition is equal to or greater than the viscosity of a composition identical to the coating composition except that it does not contain the isopropyl alcohol; The paper base material is kraft paper, The solid content concentration of the ethylene-acrylic acid copolymer in the coating composition is 30 to 50 mass%; and The ratio of the isopropyl alcohol in the coating composition is 15 to 40 parts by mass relative to 100 parts by mass of water constituting the coating composition. A method for manufacturing paper packaging materials.

2. The method for producing a paper packaging material according to claim 1, wherein the ethylene-acrylic acid copolymer is an ethylene-methacrylic acid copolymer.

3. A coating composition for forming a heat seal layer on a paper substrate, comprising: an aqueous dispersion of an ethylene-acrylic acid copolymer; Isopropyl alcohol, Including, The viscosity of the coating composition is equal to or greater than the viscosity of a composition identical to the coating composition except that it does not contain the isopropyl alcohol; The paper base material is kraft paper, The solid content concentration of the ethylene-acrylic acid copolymer in the coating composition is 30 to 50 mass%; and The ratio of the isopropyl alcohol in the coating composition is 15 to 40 parts by mass relative to 100 parts by mass of water constituting the coating composition. Paint composition.

4. The coating composition of claim 3, wherein the ethylene-acrylic acid copolymer is an ethylene-methacrylic acid copolymer.

5. A paper substrate; A heat seal layer formed from the coating composition according to claim 3 or 4; A paper laminate comprising:

6. The paper laminate according to claim 5, which is a packaging material.

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