Coating agent and laminate

Abstract

To provide a coating agent that exhibits excellent coatability and film-formability to base materials such as paper or nonwoven fabric, which are easy to be impregnated with the coating agent, and forms a resin layer that is to exhibit excellent heat sealability, waterproofness, and oil resistance.SOLUTION: A coating agent contains an acid-modified polyolefin resin, at least one selected from urethane resin, acrylic resin and hydroxy group-containing compound, and an aqueous medium.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a coating agent that has excellent coatability and film-forming properties and that forms a resin layer that has excellent heat-sealability, waterproofness, and oil resistance. [Background technology]

[0002] Conventionally, aqueous adhesives for paper containing polyolefin resins have been known. For example, the aqueous adhesive for paper disclosed in Patent Document 1 is suitable as an adhesive between paper and various thermoplastic resin films. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-213233 A Summary of the Invention [Problem to be solved by the invention]

[0004] In light of the recent marine plastic problem, the use of paper, instead of thermoplastic resin films, has been promoted as a material for packaging materials, disposable food containers, etc. When using paper as such a material, the aqueous coating agent applied to the paper is required to have excellent coatability and film-forming properties. However, the aqueous paper adhesive disclosed in Patent Document 1 sometimes has insufficient coatability and film-forming properties, and the resin layer formed from this adhesive sometimes has insufficient heat sealability, waterproofness, and oil resistance. In view of the problems of the conventional techniques as described above, an object of the present invention is to provide a coating agent which has excellent coatability and film-forming properties for substrates such as paper or nonwoven fabric into which the coating agent is easily absorbed, and which forms a resin layer which has excellent heat sealability, waterproofness, and oil resistance. [Means for solving the problem]

[0005] Means for Solving the Problems The present inventors conducted intensive research to solve the above problems, and as a result, discovered that a coating agent comprising an aqueous coating agent containing an acid-modified polyolefin resin and one or more types selected from a urethane resin, an acrylic resin, and a hydroxyl group-containing compound solves the above problems, thereby completing the present invention. That is, the gist of the present invention is as follows.

[0006] (1) A coating agent comprising an acid-modified polyolefin resin, at least one member selected from the group consisting of a urethane resin, an acrylic resin and a hydroxyl group-containing compound, and an aqueous medium. (2) The coating agent according to (1), characterized in that the content of the urethane resin and / or acrylic resin is more than 10 parts by mass and not more than 100 parts by mass per 100 parts by mass of the acid-modified polyolefin resin. (3) A laminate comprising a paper base material and a resin layer, A laminate, wherein the resin layer comprises an acid-modified polyolefin resin and at least one selected from the group consisting of a urethane resin, an acrylic resin and a hydroxyl group-containing compound. (4) A packaging material comprising the laminate described in (3) above. (5) A paper container comprising the laminate described in (3) above. Effect of the Invention

[0007] The coating agent of the present invention is composed of an acid-modified polyolefin resin blended with one or more resins selected from urethane resins, acrylic resins, and hydroxyl group-containing compounds, and therefore has excellent coatability and film-forming properties for substrates that are easily penetrated by the coating agent, such as paper or nonwoven fabric, and the formed resin layer also has excellent heat sealability, waterproofness, and oil resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention will be described in detail below. The coating agent of the present invention contains an acid-modified polyolefin resin, one or more resins selected from a urethane resin, an acrylic resin, and a hydroxyl group-containing compound, and an aqueous medium.

[0009] <Acid-modified polyolefin resin> The acid-modified polyolefin resin constituting the coating agent of the present invention is preferably a copolymer containing an acid-modified component and an olefin component as copolymerization components. By modifying the polyolefin resin with an acid, the coating agent of the present invention has improved film-forming properties and coatability onto a substrate.

[0010] The acid-modified component is preferably an unsaturated carboxylic acid component, and is introduced by an unsaturated carboxylic acid or its anhydride. Specific examples of the unsaturated carboxylic acid component include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, etc., as well as half esters and half amides of unsaturated dicarboxylic acids. Among these, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferred, and acrylic acid and maleic anhydride are particularly preferred.

[0011] The content of the acid-modified component in the acid-modified polyolefin resin is not particularly limited, but is preferably 1 to 40 mass%, more preferably 1 to 30 mass%, and even more preferably 2 to 20 mass%. If the content of the acid-modified component is less than 1 mass%, the acid-modified polyolefin resin may not be stably dispersed in an aqueous medium, and if it exceeds 40 mass%, the resin layer formed may have poor waterproofing.

[0012] Examples of the olefin component constituting the acid-modified polyolefin resin include alkenes having 2 to 6 carbon atoms, such as ethylene, propylene, isobutylene, 1-butene, 1-pentene, and 1-hexene, and mixtures of these can also be used. Among these, alkenes having 2 to 4 carbon atoms, such as ethylene, propylene, isobutylene, and 1-butene, are preferred, and ethylene is more preferred.

[0013] From the viewpoint of improving waterproof property and oil resistance, the content of the olefin component in the acid-modified polyolefin resin is preferably 50% by mass or more, and more preferably 70% by mass or more.

[0014] The acid-modified polyolefin resin preferably contains a (meth)acrylic acid ester component for the reason of improving adhesion to the substrate. The content of the (meth)acrylic acid ester component in the acid-modified polyolefin resin is preferably 0.5 to 40 mass%, more preferably 1 to 35 mass%, further preferably 3 to 30 mass%, particularly preferably 5 to 25 mass%, and most preferably 10 to 25 mass%.

[0015] Examples of the (meth)acrylic acid ester component include esters of (meth)acrylic acid and alcohols having 1 to 30 carbon atoms, and among them, from the viewpoint of easy availability, esters of (meth)acrylic acid and alcohols having 1 to 20 carbon atoms are preferred. Specific examples of such compounds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. A mixture of these may be used. Among these, from the viewpoint of improving adhesion to the substrate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl acrylate, and octyl acrylate are more preferred, ethyl acrylate and butyl acrylate are more preferred, and ethyl acrylate is particularly preferred. Note that "(meth)acrylic acid" means "acrylic acid or methacrylic acid".

[0016] The acid-modified polyolefin resin may contain other components in an amount of about 10% by mass or less of the acid-modified polyolefin resin in addition to the above components. Examples of other components include alkenes and dienes having more than 6 carbon atoms, such as 1-octene and norbornenes, maleic acid esters, such as dimethyl maleate, diethyl maleate, and dibutyl maleate, (meth)acrylic acid amides, alkyl vinyl ethers, such as methyl vinyl ether and ethyl vinyl ether, vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl versatate, as well as vinyl alcohol obtained by saponifying vinyl esters with a basic compound, etc., 2-hydroxyethyl acrylate, glycidyl (meth)acrylate, (meth)acrylonitrile, styrene, substituted styrene, carbon monoxide, and sulfur dioxide, and mixtures of these may also be used.

[0017] The acid-modified component constituting the acid-modified polyolefin resin may contain an N-substituted amide structure in which the hydroxyl group of the carboxyl group is substituted with an N,N-dimethylamino group, an N,N-diethylamino group, or the like.

[0018] Examples of the acid-modified polyolefin resin include ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid-maleic anhydride copolymer, acid-modified polyethylene, acid-modified polypropylene, acid-modified ethylene-propylene resin, acid-modified ethylene-butene resin, acid-modified propylene-butene resin, acid-modified ethylene-propylene-butene resin, and ethylene-(meth)acrylic acid ester-unsaturated carboxylic acid copolymer obtained by further modifying these acid-modified resins with acrylic ester or the like. Among them, ethylene-(meth)acrylic acid-maleic anhydride copolymer is preferable. Furthermore, the acid-modified polyolefin resin may be chlorinated in the range of 5 to 40 mass%.

[0019] As the acid-modified polyolefin resin, commercially available products such as the Bondine series manufactured by Arkema, the Bestplast series manufactured by Evonik Japan, the Primacol series manufactured by Dow Chemical Company, the Umex series manufactured by Sanyo Chemical Industry Co., Ltd., the Admar series manufactured by Mitsui Chemicals, Inc., and the Toyotack series manufactured by Toyobo Co., Ltd. can be used. In addition, commercially available water-based products can also be used, such as the Superclone series manufactured by Nippon Paper Chemicals Co., Ltd., the Zaixen series manufactured by Sumitomo Seika Chemicals Co., Ltd., the Chemipearl series manufactured by Mitsui Chemicals, and the Hardlen series manufactured by Toyobo Co., Ltd.

[0020] <Urethane resin, acrylic resin, hydroxyl group-containing compound> The coating agent of the present invention must contain at least one type selected from the group consisting of urethane resins, acrylic resins, and hydroxyl group-containing compounds. The coating agent of the present invention contains one or more selected from urethane resins, acrylic resins, and hydroxyl group-containing compounds, thereby improving the surface coatability and film-forming properties of substrates such as paper or nonwoven fabric into which the coating agent is easily absorbed. In addition, the resin layer formed from the coating film can be ensured to have a sufficient thickness, and furthermore, the coating agent has excellent heat sealability, waterproofness, and oil resistance. Furthermore, the coating agent of the present invention can adjust its viscosity by containing a hydroxyl group-containing compound, which makes it difficult for the coating agent to penetrate into the substrate and ensures a sufficient thickness of the coating film.

[0021] The coating agent of the present invention contains a urethane resin and / or an acrylic resin as a resin component other than the acid-modified polyolefin resin, and thus can form a resin layer that is superior in waterproofness and oil resistance compared to when other resins such as polyester resin are contained. The glass transition temperature of the urethane resin and the acrylic resin is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 30°C or higher.

[0022] When the coating agent contains a urethane resin and / or an acrylic resin, the content thereof is preferably more than 10 parts by mass relative to 100 parts by mass of the acid-modified polyolefin resin. More preferably, the content is more than 10 parts by mass and not more than 100 parts by mass, even more preferably, it is 12 to 70 parts by mass, and even more preferably, it is 13 to 60 parts by mass. If the content of the urethane resin and / or the acrylic resin is 10 parts by mass or less, the coating agent may have poor film formation and the formed resin layer may have poor heat sealability, and if the content exceeds 100 parts by mass, the coating agent may have poor coatability.

[0023] Examples of the hydroxyl group-containing compound include celluloses such as carrageenan, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose, polysaccharides such as xanthan gum, guar gum, pectin, and modified starch, and polyvinyl alcohol. Among these, carboxymethyl cellulose and polysaccharides are preferred because the viscosity of the coating agent can be easily controlled, and polysaccharides are more preferred because a resin layer having excellent oil resistance is formed.

[0024] When the coating agent contains a hydroxyl group-containing compound, the content is preferably 0.1 to 10 parts by mass, and more preferably 0.2 to 5 parts by mass, relative to 100 parts by mass of the acid-modified polyolefin resin. If the content of the hydroxyl group-containing compound is less than 0.2 parts by mass, the viscosity of the coating agent cannot be sufficiently controlled, and the formed resin layer may have poor heat sealability, whereas if the content exceeds 5 parts by mass, the stability of the coating agent may decrease.

[0025] The coating agent of the present invention preferably contains a urethane resin and / or an acrylic resin in combination with a hydroxyl group-containing compound in order to further improve the waterproofness and oil resistance of the resin layer that is formed.

[0026] <Aqueous medium> The aqueous medium constituting the paper coating agent of the present invention is water or a liquid mainly composed of water, and may contain a basic compound and a hydrophilic organic solvent. When the aqueous medium contains a hydrophilic organic solvent, the coating agent exhibits the effect of improving the wettability to the substrate, and improving the coatability and film-forming property.

[0027] In order to impart appropriate wettability to the substrate, the content of the hydrophilic organic solvent is preferably 1 to 50 mass % relative to the total amount of the aqueous medium, more preferably 3 to 30 mass %, and even more preferably 5 to 25 mass %.

[0028] Examples of hydrophilic organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol, 1-ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, and cyclohexanol; ketones such as methyl ethyl ketone, methyl isobutyl ketone, ethyl butyl ketone, and cyclohexanone; ethers such as tetrahydrofuran and dioxane; ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, and 3-methoxy acetate. Examples of the glycol derivatives include esters such as butyl, methyl propionate, ethyl propionate, diethyl carbonate, and dimethyl carbonate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and ethylene glycol ethyl ether acetate; and further, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 3-methoxy-3-methyl-1-butanol, methoxybutanol, acetonitrile, dimethylformamide, dimethylacetamide, diacetone alcohol, ethyl acetoacetate, 1,2-dimethylglycerin, 1,3-dimethylglycerin, and trimethylglycerin.

[0029] Examples of basic compounds include ammonia, triethylamine, N,N-dimethylethanolamine, isopropylamine, aminoethanol, dimethylaminoethanol, diethylaminoethanol, ethylamine, diethylamine, isobutylamine, dipropylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, sec-butylamine, propylamine, n-butylamine, 2-methoxyethylamine, 3-methoxypropylamine, 2,2-dimethoxyethylamine, monoethanolamine, morpholine, N-methylmorpholine, N-ethylmorpholine, pyrrole, and pyridine.

[0030] <Additives> The coating agent of the present invention may contain additives such as other polymers and crosslinking agents in order to further improve the performance depending on the purpose. The other polymers are not particularly limited, and examples thereof include polyvinyl acetate, ethylene-vinyl acetate copolymers, polyvinyl chloride, polyvinylidene chloride, styrene-maleic acid resins, styrene-butadiene resins, butadiene resins, acrylonitrile-butadiene resins, poly(meth)acrylonitrile resins, (meth)acrylamide resins, chlorinated polyethylene resins, chlorinated polypropylene resins, tackifier resins such as modified nylon resins and rosin, phenolic resins, silicone resins, and epoxy resins, and a mixture of two or more of these may be used as necessary.

[0031] The crosslinking agent is not particularly limited, and examples thereof include a crosslinking agent having self-crosslinking properties, a compound having a plurality of functional groups in the molecule that react with a carboxyl group, a metal having a polyvalent coordination site, etc. Specifically, an isocyanate compound, a melamine compound, a urea compound, an epoxy compound, a carbodiimide compound, an oxazoline group-containing compound, a zirconium salt compound, a silane coupling agent, etc. are preferred. In addition, a plurality of these crosslinking agents may be used at the same time.

[0032] The content of the crosslinking agent is preferably 0.01 to 80 parts by mass, more preferably 0.1 to 50 parts by mass, and even more preferably 0.5 to 30 parts by mass, relative to 100 parts by mass of the acid-modified polyolefin resin. If the content of the crosslinking agent is less than 0.01 part by mass, the performance of the formed resin layer tends not to improve, and if it exceeds 80 parts by mass, performance such as processability may decrease.

[0033] The coating agent of the present invention may further contain various agents, such as a leveling agent, an antifoaming agent, an anti-popping agent, a pigment dispersant, an ultraviolet absorbing agent, a weather resistance agent, and a flame retardant, if necessary.

[0034] <Coating agent> The coating agent of the present invention contains the above-mentioned acid-modified polyolefin resin, one or more compounds selected from urethane resins, acrylic resins and hydroxyl group-containing compounds, and an aqueous medium, and it is preferable that the acid-modified polyolefin resin is dispersed in the aqueous medium. The content of the resin component in the coating agent of the present invention can be appropriately selected depending on the coating conditions, the desired thickness and performance of the coating film, etc., and is not particularly limited. From the viewpoint of maintaining an appropriate viscosity and exhibiting good film-forming properties, however, it is preferably 1 to 60 mass%, more preferably 3 to 55 mass%, even more preferably 5 to 50 mass%, and particularly preferably 10 to 45 mass%. In order to suppress penetration into the substrate, the viscosity of the coating agent of the present invention is preferably 5 to 3000 mPa·s, more preferably 10 to 2000 mPa·s, and even more preferably 50 to 1500 Pa·s. If the coating agent has a viscosity of less than 5 mPa·s, it may be difficult to apply the coating agent, and if the viscosity exceeds 3000 mPa·s, it may also be difficult to apply the coating agent.

[0035] The coating agent of the present invention has excellent coatability and film-forming properties for substrates that are easily permeated, such as paper or nonwoven fabric, and can be uniformly applied to the substrate surface by a known coating method, such as gravure roll coating, reverse roll coating, wire bar coating, lip coating, air knife coating, curtain flow coating, spray coating, dip coating, brush coating, etc., and then subjected to a heat treatment for drying, thereby forming a uniform resin layer in close contact with the substrate surface. As the heating device, a normal hot air circulation type oven, an infrared heater, etc. may be used. The heating temperature and heating time are appropriately selected taking into consideration economic efficiency, etc.

[0036] The coating agent of the present invention has excellent coatability and is therefore capable of forming a resin layer with a sufficient thickness by a single coating step. In addition, since the coating agent of the present invention has excellent film-forming properties, it is possible to suppress problems such as cracking and coating defects (uncoated areas occurring when coating a substrate), and to obtain a resin layer with excellent waterproofing and oil resistance. Furthermore, even when the formed resin layer is curved, problems such as cracking and coating defects are suppressed. Furthermore, since the resin layer formed from the coating agent of the present invention is excellent in both heat sealability and blocking resistance, the laminate described below has improved processability during molding.

[0037] <Laminate> The laminate of the present invention is formed by laminating a paper substrate and a resin layer, and the resin layer contains an acid-modified polyolefin resin and one or more selected from a urethane resin, an acrylic resin, and a hydroxyl group-containing compound. The resin layer can be obtained by applying the coating agent of the present invention to the paper substrate and drying it.

[0038] The resin layer constituting the laminate of the present invention has a thickness of preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm, and even more preferably 1 to 20 μm. A resin layer formed so as to have a thickness within the above range has excellent thickness uniformity.

[0039] In order to adjust the thickness of the resin layer, it is preferable to use a coating agent having a concentration suitable for the desired thickness in addition to appropriately selecting the coating device and its operating conditions. The concentration of the coating agent can be adjusted by the composition of the materials used during preparation, or it may be adjusted by appropriately diluting or concentrating a coating agent that has already been prepared.

[0040] The paper substrate constituting the laminate of the present invention is manufactured by intertwining natural fibers such as plant fibers, and examples thereof include fine paper, medium quality paper, recycled paper, art paper, craft paper, roll paper, processed base paper, cloth paper, cardboard, corrugated cardboard, etc. The paper substrate may be surface-treated, and for example, the surface may be imparted with barrier properties, design properties, etc.

[0041] In order to impart required performance to the laminate of the present invention, a substrate such as a nonwoven fabric, or a layer such as a sealant layer, a printing layer, or a topcoat layer may be provided on the paper substrate surface or the resin layer surface of the laminate. Examples of methods for providing these substrates and layers include known methods such as dry lamination via an adhesive layer, thermal lamination, heat sealing, and extrusion lamination. Examples of the adhesive include one-liquid type urethane adhesives, two-liquid type urethane adhesives, epoxy adhesives, and aqueous dispersions of acid-modified polyolefin resins. The coating agent of the present invention may be used as the adhesive.

[0042] <Packaging materials, paper containers> The laminate of the present invention can be used as a packaging material or a molding material for paper containers. The laminate of the present invention can be molded by folding or rolling into a cylindrical shape, overlapping the ends, and heat sealing, since the resin layer has excellent heat sealability. Furthermore, since the resin layer is formed from a coating agent with excellent film-forming properties, the occurrence of cracks and the like is suppressed even when the laminate is folded or rolled into a cylindrical shape, and even if the resin layers of the laminate overlap and come into contact with each other during processing, the occurrence of blocking is suppressed, which means that the laminate has excellent moldability. Since the resin layer of the laminate of the present invention has excellent moldability, food packaging materials and paper containers for containing food molded using the laminate of the present invention have excellent waterproof and oil resistance. The form of the paper container is not particularly limited, and examples thereof include paper packaging, paper plates, paper cups, etc. Paper cups are manufactured by folding the bottom, fixing the joint, forming pleats, and rolling and gluing the upper end, and the resin layer formed by the coating agent of the present invention can follow such shapes and can be heat-sealed well. EXAMPLES

[0043] The present invention will be described in detail below with reference to examples, although the present invention is not limited to these. Various characteristics were measured or evaluated by the following methods.

[0044] 1. Melting point and glass transition temperature 10 mg of the resin was used as a sample and measured using a DSC (differential scanning calorimetry) device (PerkinElmer, DSC7) at a temperature rise rate of 10° C. / min.

[0045] 2. Viscosity of coating agent The rotational viscosity at a temperature of 25° C. was measured using a digital viscometer (DV2T, manufactured by Brookfield).

[0046] 3. Coating ability on paper substrate The thickness of the resin layer of the laminate was measured using a gauge sensor (GS-3813B, manufactured by Ono Sokki Co., Ltd.), and the coatability was evaluated according to the following criteria. ○: Resin layer thickness is 5 μm or more △: Resin layer thickness is 3 μm or more and less than 5 μm ×: Resin layer thickness is less than 3 μm

[0047] 4.Film forming property The surface of the resin layer of the laminate was observed at a magnification of 200 times using an electron microscope (a tabletop scanning electron microscope manufactured by Thermo Fisher Scientific), and the film-forming properties were evaluated according to the following criteria. ○: No cracks or uncoated areas on the paper base △: Cracks, some uncoated areas on the paper base (not across the entire surface) ×: Cracks and uncoated areas on the paper base material are present over the entire surface.

[0048] 5. Heat sealability (bonding strength) The coating agent was applied to the paper substrate using a bar coater (No. 20) and then dried. The coated surfaces were then bonded together and heat-sealed for 5 seconds at a temperature of 150°C and a pressure of 0.2 MPa. The bonded surfaces of the bonded paper substrates were then peeled off in a 180° direction, and the heat-sealability was evaluated according to the following criteria. ○: Adhesion is sufficient, and the paper is not damaged when peeled off. △: Adhered but can be easily peeled off ×: Not bonded

[0049] 6. Waterproof Water containing 0.3% by mass of blue pigment (EP-700 Blue GA, manufactured by Dainichi Seika Chemicals Co., Ltd.) was dropped onto the resin layer surface of the laminate, and after 5 minutes, the surface was wiped off. The degree of coloring of the paper at that time was visually confirmed, and the waterproofness was evaluated according to the following criteria. ◎: No traces of water droplets ○: There are very few water droplets ×: Water droplets (water has penetrated)

[0050] 7.Oil resistance The kit test was conducted according to the following method based on JAPAN TAPPI T599cm-02 paper pulp test method. Test solutions (kit numbers 1 to 12) in which castor oil, toluene and n-heptane were mixed in different volume ratios were dropped onto the resin layer surface of the laminate. If spots were formed due to penetration of the oil droplets 15 seconds after dropping, the sample was judged as failing. The highest kit number that did not produce spots was regarded as the oil resistance of that sample, and the oil resistance was evaluated according to the following criteria. ◎: Oil resistance 10 or higher ○: Oil resistance level 8~9 △: Oil resistance level 5~7 ×: Oil resistance level 4 or less

[0051] 8. Blocking resistance The resin layer surfaces of the laminates were brought into contact with each other and left to stand for one day under a load of 1 MPa in an atmosphere of 25° C. After that, the samples were peeled off and the blocking resistance was evaluated according to the following criteria. ◎: No blocking (no peeling resistance or peeling noise) ○: No force is required to peel off, but there is a peeling sound △: Requires force to peel off (not adhered) ×: Adhered

[0052] The following materials were used as the coating agent raw materials and the paper base material. 1. Acid-modified polyolefin resin Preparation of aqueous dispersion of acid-modified polyolefin resin (E-1) Using a stirrer equipped with a sealable pressure-resistant glass container with a heater, 100 g of acid-modified polyolefin resin (ethylene-ethyl acrylate-maleic anhydride copolymer, maleic anhydride 2 mass%, melting point 105°C, glass transition temperature less than 0°C), 100 g of isopropanol, 4.0 g of triethylamine, and 296 g of distilled water were charged into the glass container and heated to 120°C with stirring, thereby obtaining a milky white polyolefin resin aqueous dispersion E-1 (solids concentration approximately 20 mass%, viscosity 60 mPa s, isopropol ratio in aqueous medium 25 mass%).

[0053] Preparation of aqueous dispersion of acid-modified polyolefin resin (E-2) To 200 g of the acid-modified polyolefin resin aqueous dispersion (E-1), 100 g of water and 2.0 g of dimethylethanolamine were added, and then 102 g of the solvent was removed under reduced pressure using an evaporator to obtain an acid-modified polyolefin resin aqueous dispersion (E-2, solids concentration approximately 20% by mass, viscosity 15 mPa·s) in which the isopropanol ratio in the aqueous medium was less than 1% by mass.

[0054] 2. Urethane resin Urethane resin emulsion: Mitsui Chemicals, Takelac W-6010, solid content concentration 30% by mass, glass transition temperature 90°C

[0055] 3. Acrylic resin Acrylic resin A emulsion: DSM, NeoCryl A-6092, solid content 43% by mass, glass transition temperature 56°C Acrylic resin B emulsion: DSM, NeoCryl A-1092, solid content 49% by mass, glass transition temperature 9°C

[0056] 4. Hydroxyl group-containing compounds CMC: Carboxymethylcellulose, Nippon Paper Industries, Sunrose F350HC Polysaccharides: Xanthan gum, manufactured by Danisco Japan, GRINDSTED Xanthan J PVA: Polyvinyl alcohol solution, 10% by weight solution of JMR-10L manufactured by Nippon Vinyl Polyvinyl Alcohol Co., Ltd. (solvent: water / isopropanol (weight ratio 40 / 60))

[0057] 5.Paper base material Made by Nippon Paper Industries, weight 230g / m 2

[0058] Example 1 To 100 g of the acid-modified polyolefin resin aqueous dispersion (E-2), 20 g of the urethane resin emulsion (solid content mass ratio 100 / 30) and 7 g of isopropanol (isopropanol ratio in the aqueous medium 7% by mass) were added to prepare a coating agent. The prepared coating liquid was applied onto a paper substrate using a bar coater (No. 20) and dried for 30 seconds in a hot air dryer set at 110°C to form a resin layer and produce a laminate.

[0059] Examples 2 to 15, Comparative Examples 1 to 3 The types of the acid-modified polyolefin resin aqueous dispersion, the urethane resin, the acrylic resin, and the hydroxyl group-containing compound were changed, and the mass ratio of each solid content was changed, as shown in Table 1. In addition, the amount of isopropanol in the aqueous medium was added so as to obtain the ratio shown in Table 1, to prepare a coating agent, and a laminate was prepared in the same manner as in Example 1.

[0060] Table 1 shows the compositions of the coating agents prepared in the examples and comparative examples, and the evaluation results of various properties.

[0061] [Table 1]

[0062] The coating agents obtained in Examples 1 to 15 had excellent paper coatability and film-forming properties, and the formed resin layers had excellent heat sealability, waterproofness, and oil resistance. In particular, in Examples 3 and 8, the types and contents of the urethane resin, acrylic resin, and hydroxyl group-containing compound were preferable, and as a result, the formed resin layer had even more excellent properties such as waterproofness and oil resistance.

[0063] In Comparative Examples 1 to 3, the aqueous dispersions of acid-modified polyolefin resins that did not contain any of urethane resin, acrylic resin, or hydroxyl group-containing compounds were inferior in coatability and film-forming properties on paper, and the formed resin layers were inferior to those of the Examples in all of the heat sealability, waterproofness, and oil resistance.

Claims

1. An acid-modified polyolefin resin; one or more selected from a urethane resin, an acrylic resin, and a hydroxyl group-containing compound; A coating agent comprising: an aqueous medium.

2. 2. The coating agent according to claim 1, wherein the content of the urethane resin and / or the acrylic resin is more than 10 parts by mass and not more than 100 parts by mass per 100 parts by mass of the acid-modified polyolefin resin.

3. A laminate comprising a paper base material and a resin layer, The resin layer comprises an acid-modified polyolefin resin, and one or more resins selected from the group consisting of urethane resins, acrylic resins, and hydroxyl group-containing compounds.

4. A packaging material comprising the laminate according to claim 3.

5. A paper container comprising the laminate according to claim 3.

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