Laminate for paper containers and method for manufacturing the same

Abstract

The present invention aims to provide a laminate for paper containers that is excellent in crease resistance, alcohol resistance, adhesion, and blocking resistance. [Solution] The above problem is solved by a laminate for paper containers having a heat seal layer, a paper substrate, a printing layer, and a surface protection layer in that order, wherein the basis weight of the paper substrate is 100 g / m². 2 The above is resolved by a laminate in which the printed layer contains a urethane resin (A) and the surface protective layer contains a cellulose resin (B) and an alkyd resin (C), or by a laminate in which the molecular weight distribution (Mw / Mn) of the alkyd resin (C) is 5 to 20.

Description

[Technical Field]

[0001] The present invention relates to a laminate for paper containers and a method for manufacturing the same. [Background technology]

[0002] In recent years, it has become common for product packaging and other wrapping materials to be printed for decoration and surface protection. Furthermore, the design, aesthetic appeal, and sense of luxury of printed materials can stimulate consumer purchasing intent, and therefore have significant industrial value.

[0003] Traditionally, laminate packaging materials using plastic film have been primarily used for packaging. For example, Patent Document 1 describes an invention relating to a laminate packaging material consisting of a base material, a printing layer, an adhesive layer, and a sealant layer, in which biomass resin is used in the printing layer and the adhesive layer. However, laminate packaging materials use a large amount of plastic film made from petroleum-derived materials, and from the viewpoint of reducing plastic waste, environmental responsibility, and carbon neutrality, there is a desire to switch to paper (paper-based packaging materials), and technological development is underway.

[0004] In particular, when paper packaging materials are used for paper containers, they are deformed under pressure using a jig during the molding process, creating creases (fold lines). At this time, the resin coating, such as the printed layer, must be durable enough to withstand the deformation stress (crease resistance). Furthermore, with the increasing use of disinfectant alcohol as a measure against infectious diseases, paper containers are required to be alcohol-resistant.

[0005] For example, Patent Document 2 describes a packaging material having polyethylene resin, a paper substrate, a printing layer containing nitrocellulose resin, and a surface protective layer containing nitrocellulose resin. However, since the surface protective layer does not contain alkyd resin, there are concerns that its alcohol resistance and crease resistance will be reduced. Patent Document 3 describes a packaging material having a polyethylene base material, a printing layer containing urethane resin, and a surface protective layer containing nitrocellulose resin and alkyd resin. However, this invention relates to plastic packaging materials and does not mention paper packaging materials. Therefore, there is a concern that the entire packaging material is soft, and when a jig is pressed against it, the packaging material may deform excessively, reducing its crease resistance. Patent Document 4 describes a packaging material having a polypropylene substrate, a printing layer containing urethane resin, and a surface protective layer containing nitrocellulose resin and polyester resin. However, this invention relates to plastic packaging materials and does not mention paper packaging materials, and since the surface protective layer does not contain alkyd resin, there are concerns that its alcohol resistance and crease resistance will be reduced. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-051796 [Patent Document 2] Japanese Patent Publication No. 2020-055171 [Patent Document 3] Japanese Patent Publication No. 2021-165023 [Patent Document 4] Japanese Patent Publication No. 2021-138856 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to provide a laminate for paper containers that is excellent in crease resistance, alcohol resistance, adhesion, and blocking resistance. [Means for solving the problem]

[0008] As a result of diligent research into the aforementioned problems, the inventors have found that the above problems can be solved by using the laminate described below, and have thus come to present invention.

[0009] That is, the present invention relates to a laminate for a paper container having a heat-sealing layer, a paper base material, a printing layer, and a surface protection layer in this order, where the basis weight of the paper base material is 100 g / m 2 or more, the printing layer contains a urethane resin (A), and the surface protection layer contains a cellulose-based resin (B) and an alkyd resin (C).

[0010] That is, the present invention relates to the laminate, wherein the molecular weight distribution (Mw / Mn) of the alkyd resin (C) is 5 to 20.

[0011] That is, the present invention relates to the laminate, wherein the solid content mass ratio of the cellulose-based resin (B) and the alkyd resin (C) in the surface protection layer is 15:85 to 85:15.

[0012] That is, the present invention relates to the laminate, wherein the printing layer further contains at least one selected from the group consisting of a cellulose-based resin (B'), a vinyl-based resin, and an acrylic resin.

[0013] That is, the present invention relates to the laminate, wherein the urethane resin (A) contains a polyether-derived structure and / or a polyester-derived structure.

[0014] That is, the present invention relates to the laminate, wherein the total content of the cellulose-based resin (B) and the alkyd resin (C) in the surface protection layer is 50% by mass or more in 100% by mass of the surface protection layer.

[0015] That is, the present invention relates to the laminate, wherein the total mass ratio of the urethane resin (A) contained in the printing layer and the alkyd resin (C) contained in the surface protection layer is 10 to 40% by mass in 100% by mass of the total of the printing layer and the surface protection layer.

[0016] That is, the present invention relates to the laminate, which further includes an anchor coat layer between the paper base material and the printing layer.

[0017] In other words, the present invention relates to the laminate comprising polyethylene resin.

[0018] In other words, the present invention relates to a laminate in which the 60-degree gloss value of the surface protective layer, measured by the method described in JIS Z 8741:1997, is 15 to 45.

[0019] In other words, the present invention relates to the laminate for use in sake pack containers.

[0020] In other words, the present invention relates to a method for manufacturing a laminate for paper containers having a heat seal layer, a paper substrate, a printing layer, and a surface protection layer in this order, The basis weight of the aforementioned paper substrate is 100 g / m². 2 That's all. A step of forming the heat seal layer by coating one surface of the paper substrate with molten heat sealable resin, A step of forming the printed layer by printing a printing ink containing urethane resin (A) onto one side of the paper substrate, The present invention relates to a method for manufacturing a laminate, comprising the step of applying an overcoat agent containing a cellulose resin (B) and an alkyd resin (C) onto the printed layer to form the surface protective layer. [Effects of the Invention]

[0021] The present invention provides a laminate for paper containers that is excellent in crease resistance, alcohol resistance, adhesion, and blocking resistance. [Modes for carrying out the invention]

[0022] The embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is merely an example of embodiments of the present invention, and the present invention is not limited to these contents unless it exceeds the gist of the invention.

[0023] In the following explanation, "parts" refers to "parts by mass" unless otherwise specified, and "%" refers to "percentage by mass". In the following description of the present invention, "printing ink" refers to an ink containing pigments and other colorants for forming a printed layer, and "overcoat agent" refers to a coating agent that does not contain pigments and other colorants for forming a surface protective layer. However, this does not mean that small amounts of colorants that may have been unintentionally mixed in are excluded.

[0024] <Laminate for paper containers> The present invention relates to a laminate for paper containers having, in this order, a heat-seal layer, a paper substrate, a printing layer, and a surface protection layer, wherein the basis weight of the paper substrate is 100 g / m². 2 The above is characterized in that the printed layer contains a urethane resin (A), and the surface protective layer contains a cellulose resin (B) and an alkyd resin (C). Other layers, such as known layers including a barrier layer, may be present on the outside of the laminate or between each layer. Furthermore, from the viewpoint of improving adhesion, it is preferable to have an anchor coat layer between the paper substrate and the printed layer. The laminate for paper containers of the present invention is preferably used as a packaging material for liquids, and more preferably as a packaging material for sake cartons.

[0025] This invention relates to a paper substrate with a basis weight of 100 g / m². 2 In summary, by including a urethane resin (A) in the printing layer and a cellulose-based resin (B) and alkyd resin (C) in the surface protection layer, excessive deformation when creases (fold lines) are applied can be suppressed, the adhesion between each layer between the paper substrate, the printing layer, and the surface protection layer can be improved, and both flexibility and toughness of the coating film in the printing layer and the surface protection layer can be achieved, resulting in good resistance to creases, alcohol, adhesion, and blocking.

[0026] In particular, when the present invention is used as a packaging material for alcoholic beverages, it is common to fill the packaging container formed using the packaging material with 2 liters or more of alcoholic beverages. Therefore, the basis weight of the paper base material used in the present invention is 100 g / m². 2 It is preferable that the basis weight is 100 g / m². 2If the basis weight is less than 100 g / m², it will not be able to support the weight of the filled alcoholic beverages and will not be able to maintain the shape of the packaging container. 2 Therefore, since the total weight of the laminate of the present invention increases, a higher level of blocking resistance than usual is required. Furthermore, when forming sake packs, there is a process of applying pressure to the packaging material using a jig and folding the packaging material. In this process, the higher the basis weight of the paper base material, the more effectively excessive deformation of the laminate when folded can be suppressed. Also, the better the adhesion between each layer in the paper base material, the printed layer, and the surface protection layer, as well as the better the flexibility and toughness of the printed layer and the surface protection layer, the more effectively crack formation in the printed layer and / or the surface protection layer can be suppressed. In addition, as mentioned above, the present invention also exhibits excellent alcohol resistance. The present invention can solve the above-mentioned problems and can be suitably used as packaging material for sake cartons. However, the above description does not limit the use of the present invention to packaging material for sake cartons.

[0027] The gloss value of the surface protective layer is preferably 15 to 45, more preferably 20 to 40, and even more preferably 20 to 30. When the gloss value of the surface protective layer is within the above range, a good balance is achieved between the toughness and flexibility of the coating film, which tends to improve alcohol resistance, crease resistance, adhesion, and blocking resistance. The above gloss values ​​are 60-degree gloss values ​​(Gs(60)) measured in accordance with JIS Z 8741:1997. Note that the above gloss values ​​are different from the gloss (mirror reflection) of metal layers such as the aluminum vapor-deposited layer on the inside of the packaging material.

[0028] As an example of an embodiment of the laminate of the present invention that satisfies the gloss value of the surface protective layer described above, the basis weight of the paper substrate is 150 to 500 g / m². 2 It is preferable that the following conditions be met. Paper substrates are aggregates of paper fibers and have slight irregularities on their surface, so using a paper substrate tends to reduce the gloss value. On the other hand, resin films such as polyethylene films have a high degree of surface smoothness, so they tend to significantly improve the gloss value. The coating weight of the printed layer is 0.1 to 12 g / m².2 is preferably 0.3 to 7.2 g / m 2 is more preferably so. Further, the coating amount of the surface protective layer is 0.1 to 10 g / m 2 is preferably 0.5 to 7 g / m 2 is more preferably so. In addition, the laminate of the present invention preferably further has an anchor coat layer. Since a coating film with high smoothness can be formed by having a large coating amount of the printing layer and the surface protective layer and further having an anchor coat layer, the tendency to satisfy the gloss value increases. The total mass ratio of the urethane resin (A) contained in the printing layer and the alkyd resin (C) contained in the surface protective layer is preferably 10 to 40% by mass, more preferably 12 to 35% by mass in the total 100% by mass of the printing layer and the surface protective layer. The higher the total mass ratio of the urethane resin (A) contained in the printing layer and the alkyd resin (C) contained in the surface protective layer, the better the leveling property during printing and the higher the tendency to satisfy the gloss value.

[0029] <Configuration of the laminate> As an example of the configuration of the laminate of the present invention, the following can be preferably cited. In the following examples, " / " means the boundary of each layer. (1) Heat seal layer / Paper substrate / Printing layer / Surface protective layer (2) Heat seal layer / Paper substrate / Anchor coat layer / Printing layer / Surface protective layer (3) Heat seal layer / Barrier layer / Paper substrate / Printing layer / Surface protective layer (4) Heat seal layer / Barrier layer / Paper substrate / Anchor coat layer / Printing layer / Surface protective layer Note that the configuration of the laminate is not limited to the above.

[0030] <Paper substrate> Paper substrates can be selected from various types depending on the application, including medium-grade paper, fine-grade paper, newsprint, cardboard, art paper, cast paper, kraft paper, and coated paper. Among these, from the perspective of the aesthetic appearance of the laminate, paper with at least one side being highly smooth, such as coated paper, is desirable. The paper thickness can be freely selected according to the rigidity (stiffness) of the laminate required for the final application, but the basis weight of the paper substrate should be 100 g / m². 2 The above is the case, 150-500g / m 2 Preferably, it is 300-450 g / m². 2 It is more preferable that the basis weight of the paper substrate is within the above range. When the basis weight of the paper substrate is within the above range, the crease resistance tends to improve. The density of the paper substrate is 0.6~1.1 g / m². 2 It is preferable that this be the case.

[0031] <Print layer> The printed layer contains urethane resin (A). Preferably, the printed layer also contains a colorant. Because urethane resin (A) has high flexibility and cohesiveness, the printed layer containing urethane resin (A) is flexible, and adhesion is particularly good when the printed layer is in contact with the anchor coat layer. The printed layer is formed by printing the printing ink using a general printing method and then drying it. Various printing methods can be used to form the printed layer, but from the standpoint of productivity, gravure printing or flexographic printing is preferable, and gravure printing is particularly preferable. The coating amount of the printed layer is 0.1 to 12 g / m². 2 Preferably, the amount is 0.3 to 7.2 g / m². 2 It is more preferable that the amount be 0.5 to 3.6 g / m 2 It is particularly preferable that the following conditions are met. The content of urethane resin (A) in the printed layer is preferably 3 to 40% by mass, more preferably 4 to 20% by mass, and even more preferably 5 to 15% by mass, based on 100% by mass of the printed layer. When the content of urethane resin (A) in the printed layer is within the above range, adhesion and crease resistance tend to improve.

[0032] <Urethane resin (A)> The urethane resin (A) is synthesized from various polyols and polyisocyanates, and may contain components such as chain extenders. There are no particular restrictions on the polyol used in the urethane resin (A), but from the viewpoint of preventing gelation during synthesis and solubility during ink formation and printing, it is preferable that it contains 50% by mass or more of a diol component, and more preferably 90% by mass or more. Specifically, as raw material polyols, high molecular weight diols such as polyester polyols, polyether polyols, polycarbonate diols, and polycaprolactone diols can be used, as well as low molecular weight diols such as ethylene glycol, propylene glycol, and neopentyl glycol, and dimer diols extracted from vegetable oils. Among these, polyester polyols and / or polyether polyols are preferred, and polyester polyols are more preferred.

[0033] While any common polyisocyanate can be used as the isocyanate in the synthesis of urethane resin (A), a bifunctional isocyanate is preferable, similar to polyols. Specifically, common isocyanates such as isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, xylene diisocyanate, toluene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, hydrogenated toluene diisocyanate, and 1,5-pentane diisocyanate can be used.

[0034] The urethane resin (A) may contain chain extenders, end-terminators, or reactive functional groups as needed. Examples of chain extenders include polyamines such as isophorone diamine and ethylenediamine. Examples of end-terminators include secondary amines such as diethylamine and dibutylamine. Examples of substances containing reactive functional groups include hydroxyamines such as amino alcohols.

[0035] The weight-average molecular weight (Mw) of the urethane resin (A) is preferably 10,000 to 100,000, and more preferably 20,000 to 80,000. When the weight-average molecular weight (Mw) of the urethane resin (A) is within the above range, the crease resistance, adhesion, and blocking resistance tend to improve. The glass transition temperature of the urethane resin (A) is preferably -40 to 40°C, and more preferably -20 to 0°C. When the glass transition temperature of the urethane resin (A) is within the above range, the crease resistance, adhesion, and blocking resistance tend to improve. The amine value of the urethane resin (A) is preferably 3 mg KOH g or less, and more preferably 0 to 1 mg KOH / g or less.

[0036] The printing layer may contain a resin in addition to the urethane resin (A). Various resins can be used as the combined resin, but from the viewpoint of adhesion to the layers it comes into contact with, such as the paper substrate, anchor coat layer, and surface protective layer, and abrasion resistance, it is preferable that it be at least one selected from the group consisting of cellulose-based resins (B') such as nitrocellulose resin, vinyl-based resins such as vinyl chloride-vinyl acetate copolymer resin, and acrylic resin, more preferably cellulose-based resin (B') and / or vinyl chloride-vinyl acetate copolymer resin, and even more preferably cellulose-based resin (B'). The mass ratio of the total mass of the urethane resin (A) to the combined resin is preferably urethane resin (A) / total mass of combined resin = 90 / 10 to 10 / 90, and more preferably 50 / 50 to 20 / 80. When the mass ratio of the total mass of the urethane resin (A) to the combined resin is within the above range, alcohol resistance and crease resistance tend to improve. The content of the combined resin in the printed layer is preferably 10 to 80% by mass, and more preferably 30 to 60% by mass, based on 100% by mass of the printed layer. When the content of the combined resin in the printed layer is within the above range, alcohol resistance and crease resistance tend to improve.

[0037] <Cellulose-based resin (B') contained in the printing layer> Cellulose resin (B') is a resin obtained by esterification or nitration of cellulose resins derived from non-edible plants such as wood fibers and cotton. Examples include cellulose acetate resin, cellulose acetate butyrate resin, cellulose acetate butyrate resin, cellulose acetate propionate resin, and nitrocellulose resin. From the viewpoint of heat resistance and gloss, nitrocellulose resin is preferred. These may be used individually or in combination of two or more.

[0038] The cellulose resin (B') is preferably such that its viscosity, measured in accordance with JIS K 6703-1995, satisfies at least one of the following conditions (1) to (3). The viscosity is the time it takes for a steel ball to fall through the isopropanol solution of the cellulose resin (steel ball fall time (seconds)). (1) The viscosity at a solution concentration of 12.2% by mass is 1.5 to 16 seconds. (2) The viscosity at a solution concentration of 20% by mass is 3 to 40 seconds. (3) The viscosity at a solution concentration of 25% by mass is 0.1 to 22 seconds. In particular, the viscosity of the cellulose resin (B') is preferably such that it satisfies the above condition (3). In the above condition (3), the viscosity at a solution concentration of 25% by mass is preferably 0.3 to 15 seconds, and more preferably 0.5 to 9 seconds.

[0039] The weight-average molecular weight (Mw) of the cellulose resin (B') is preferably 5,000 to 200,000, more preferably 8,000 to 100,000, and even more preferably 10,000 to 80,000. When the weight-average molecular weight (Mw) of the cellulose resin (B') is within the above range, there is a tendency for alcohol resistance, crease resistance, and blocking resistance to improve. Furthermore, the glass transition temperature of the cellulose resin (B') is preferably 90°C to 200°C, more preferably 115°C to 180°C, and particularly preferably 140°C to 160°C. When the glass transition temperature of the cellulose resin (B') is within the above range, there is a tendency for alcohol resistance, crease resistance, and blocking resistance to improve.

[0040] Examples of commercially available cellulose resins (B') include those manufactured by NOBEL (DHX3-5, DHX5-10, DHX8-13).

[0041] <Vinyl resin> Vinyl resins include structures formed by polymerizing monomers containing a vinyl group. Examples of vinyl resins include vinyl chloride resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-acrylic copolymer resin, and polyvinyl acetal resin. Vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-acrylic copolymer resin, and polyvinyl acetal resin are preferred, and vinyl chloride-vinyl acetate copolymer resin is more preferred.

[0042] The weight-average molecular weight (Mw) of the vinyl resin is preferably 10,000 to 100,000, more preferably 30,000 to 70,000. When the weight-average molecular weight (Mw) of the vinyl resin is within the above range, alcohol resistance and crease resistance tend to improve. The glass transition temperature of the vinyl resin is preferably 50 to 90°C, more preferably 55 to 85°C, and even more preferably 65 to 80°C. When the glass transition temperature of the vinyl resin is within the above range, alcohol resistance and crease resistance tend to improve. The hydroxyl value of the vinyl resin is preferably 10 to 200 mgKOH / g, more preferably 20 to 150 mgKOH / g, and even more preferably 30 to 100 mgKOH / g. When the hydroxyl value of the vinyl resin is within the above range, alcohol resistance tends to improve.

[0043] (Vinyl chloride-acrylic copolymer resin) Vinyl chloride-acrylic copolymer resins mainly consist of copolymers of vinyl chloride and acrylic monomers, where the acrylic monomer is a monomer having an acrylic group or a methacrylic group, and preferably contains an acrylic monomer having a hydroxyl group. (Hereinafter, "acrylic" may be referred to as "(meth)acrylic.") Vinyl chloride-acrylic copolymer resins may be produced by block copolymerization or random copolymerization of vinyl chloride and acrylic monomers, or by graft copolymerization in which acrylic monomers are grafted onto the side chains of polyvinyl chloride. The acrylic monomers that can be used can be referred to in the section on <Acrylic Resins> below.

[0044] For the vinyl chloride-acrylic copolymer resin, commercially available products such as Solvine Type A series (manufactured by Shin-Etsu Chemical Co., Ltd.) can be used.

[0045] (Vinyl chloride-vinyl acetate copolymer resin) A vinyl chloride-vinyl acetate copolymer resin can be any resin in which at least vinyl chloride and vinyl acetate are copolymerized. Commercially available vinyl chloride-vinyl acetate copolymer resins such as the Solvine C-type series (manufactured by Shin-Etsu Chemical Co., Ltd.) can be used.

[0046] (Polyvinyl acetal resin) Polyvinyl acetal resins are obtained by reacting polyvinyl alcohol with butyraldehyde and / or formaldehyde to form an acetal ring, and preferably, polyvinyl butyral resin having a butyral ring as the acetal ring. Commercially available polyvinyl acetal resins such as the S-Lec BL series (manufactured by Sekisui Chemical Co., Ltd.) can be used.

[0047] <Acrylic resin (excluding those containing monomers with vinyl groups)> Acrylic resin is a resin containing constituent units derived from acrylic monomers. However, it excludes those containing monomers having vinyl groups. It is preferable that the acrylic resin has carboxyl groups or other acidic groups. The glass transition temperature of the acrylic resin is preferably 40 to 110°C, and more preferably 60 to 90°C. When the glass transition temperature of the acrylic resin is within the above range, the blocking resistance tends to improve. The weight-average molecular weight (Mw) of the acrylic resin is preferably 5,000 to 100,000, and more preferably 8,000 to 40,000. When the weight-average molecular weight (Mw) of the acrylic resin is within the above range, the blocking resistance tends to improve.

[0048] Examples of monomers having an unsaturated double bond that include the (meth)acrylic monomer include alkyl ester compounds of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, and lauryl (meth)acrylate. (meth)acrylamide derivatives containing at least one N-substituted methylol group, such as N-methylol(meth)acrylamide, Aminoalkyl esters of (meth)acrylic acid such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, dipropylaminopropyl (meth)acrylate, etc. (Meth)acrylic acid mono or diesters of glycols such as diethylene glycol and dipropylene glycol, Styrene, styrene derivatives such as α-methylstyrene, Hydroxyalkyl ester compounds of (meth)acrylic acid such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate. Examples include acrylic acid and methacrylic acid. The acrylic resin is preferably one having carboxyl groups and / or hydroxyl groups, and if the acrylic resin has hydroxyl groups, it is preferable that it contains a hydroxyalkyl ester compound of (meth)acrylic acid as a monomer constituting the acrylic resin.

[0049] Examples of commercially available acrylic resins used in printing layers include the Dianaal series (manufactured by Mitsubishi Rayon Co., Ltd.) and the ACRYDIC series (manufactured by DIC Corporation).

[0050] <Coloring agent> The colorants used in printing inks are preferably pigments. There are no particular restrictions on the pigments, and organic or inorganic pigments commonly used in inks can be used. The colorant content in the printing layer is preferably 10 to 50% by mass, and more preferably 20 to 40% by mass, of 100% by mass of the printing layer.

[0051] <Organic pigments> Examples of organic pigments include organic compounds and organometallic complexes, such as soluble azos, insoluble azos, azos, phthalocyanines, halogenated phthalocyanines, anthraquinones, anthancersones, dianthaquinonyls, anthrapyrimidines, perylenes, perinones, quinacridones, thioindigos, dioxazines, isoindolinones, quinophthalones, azomethine azos, flavanthrons, diketopyrrolopyrroles, isoindolines, indanthrones, and carbon blacks. Other examples include carmine 6B, lake red C, permanent red 2B, disazo yellow, pyrazolone orange, carmine FB, chromophthal yellow, chromophthal red, phthalocyanine blue, phthalocyanine green, dioxazine violet, quinacridone magenta, quinacridone red, indanthrone blue, pyrimidine yellow, thioindigobordeaux, thioindigomagenta, perylene red, perinone orange, isoindolinone yellow, aniline black, diketopyrrolopyrrole red, and daylight fluorescent pigments.

[0052] <Inorganic pigments> Examples of inorganic pigments include titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, aluminum particles, mica, bronze powder, chrome vermilion, lead yellow, cadmium yellow, cadmium red, ultramarine, Prussian blue, red iron oxide, yellow iron oxide, iron black, titanium dioxide, and zinc oxide. Aluminum, such as kaolin, clay, and magnesium carbonate, is available in leafing or non-leafing types, but the non-leafing type is preferred.

[0053] <Additives contained in the printing layer> The printed layer may contain additives such as defoamers and crosslinking agents as needed. For example, it may contain any additives such as plasticizers, defoamers, amide waxes, hydrocarbon waxes, and chelating agents, and it is preferable to contain at least one selected from the group consisting of plasticizers, hydrocarbon waxes, and chelating agents.

[0054] <Plasticizer> Plasticizers, even in small amounts, promote the volatility of organic solvents, impart flexibility to the printed layer, and enhance adhesion to the paper substrate due to their high affinity with sizing agents. The plasticizer content in the printed layer is preferably 0.1 to 20% by mass, and more preferably 1 to 10% by mass, based on 100% by mass of the total mass of the printed layer. When the plasticizer content in the printed layer is within the above range, adhesion and blocking resistance tend to improve. The solid content ratio of urethane resin (A) to plasticizer in the printed layer is preferably urethane resin (A):plasticizer = 99:1 to 60:40, and more preferably 90:10 to 70:30. When the solid content ratio of urethane resin (A) to plasticizer in the printed layer is within the above range, crease resistance, adhesion, and blocking resistance tend to improve. As a plasticizer, one that has excellent compatibility with cellulose resin (B') and other resin components contained in the printing layer, and has low volatility, is preferably used. For example, it is preferable to include at least one selected from citrate esters, phthalates, phosphate esters, trimetates, aliphatic dibasic acid esters, glycol ethers, sulfonamides, and castor oil.

[0055] Examples of citrate esters include acetyltrialkyl citrates such as triethyl citrate, acetyltriethyl citrate, tri-n-butyl citrate, acetyltri-n-butyl citrate, and acetylhexyl acetylcitrate. The alkyl group preferably has 2 to 12 carbon atoms, with acetyltri-n-butyl citrate and acetyltriethyl citrate being more preferred. Examples of phthalate esters include dialkyl phthalates such as bis(2-ethylhexyl) phthalate, diisononyl phthalate, diisodecyl phthalate, and diundecyl phthalate. The alkyl group preferably has 2 to 12 carbon atoms, with diisononyl phthalate and diisodecyl phthalate being more preferred. Examples of phosphate esters include tricresyl phosphate, triphenyl phosphate, tributyl phosphate, and other phosphate esters, with tributyl phosphate being preferred. Examples of trimetate esters include trialkyl trimetates such as tri-2-ethylhexyl trimetate, trioctyl trimetate, and triisononyl trimetate. The alkyl group preferably has 2 to 12 carbon atoms, with tri-2-ethylhexyl trimetate being more preferred. As for the aliphatic dibasic acid ester, it is preferable that the alkyl group contained in the aliphatic dibasic acid ester has 2 to 12 carbon atoms, and it is more preferable that it is a fatty acid dialkyl ester. Examples of fatty acid dialkyl esters include adipic acid esters and sebacate acid esters, and it is preferable that they are bis(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis(2-ethylhexyl) sebacate, diisononyl sebacate, diisodecyl sebacate, and bis(2-ethylhexyl) maleate. Examples of glycol ethers include diethylene glycol monobutyl ether and diethylene glycol monoethyl ether, and it is preferable that the boiling point is 125°C or higher, more preferably 150°C or higher, and even more preferably 190°C to 250°C. Examples of sulfonamides include N-butylbenzenesulfonamide and N-ethyltoluenesulfonamide.

[0056] <Chelating agent> The printed layer preferably further contains a chelating agent. Preferred chelating agents include, for example, titanium chelate and zirconium chelate. Examples of titanium chelates include titanium alkoxides such as tetraisopropyl titanate, tetran-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, tetramethyl titanate, and tetrastearyl titanate, as well as triethanolamine titanate, titanium acetylacetate, titanium tetraacetylacetonate, tetraisopropoxytitanium, titanium ethylacetoacetate, titanium lactate, octylene glycol titanate, n-butyl phosphate titanium, and propanediokistitanium bis(ethylacetylacetate). Examples of zirconium chelates include zirconium propionate and zirconium acetylacetate. From the viewpoint of blocking properties, it is preferable that the chelating agent does not generate acetylacetone after the crosslinking reaction. The chelating agent content in the printed layer is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass, based on 100% by mass of the total mass of the printed layer. When the chelating agent content in the printed layer is within the above range, the blocking resistance tends to improve.

[0057] <Hydrocarbon wax> The printed layer preferably contains hydrocarbon wax. The hydrocarbon wax is preferably hydrocarbon wax particles with a hardness (penetration) of 0.5 to 12. Examples of hydrocarbon waxes include polyethylene wax, Fischer-Tropsch wax, paraffin wax, microstarin wax, and polypropylene wax. Among these, hydrocarbon wax containing polyethylene wax and / or paraffin wax is preferred, and hydrocarbon wax containing paraffin wax is more preferred. The hydrocarbon wax content in the printed layer is preferably 1 to 20% by mass, and more preferably 5 to 15% by mass, based on 100% by mass of the total mass of the printed layer. When the hydrocarbon wax content in the printed layer is within the above range, the blocking resistance tends to improve.

[0058] <Printing Ink> The printing ink contains a colorant, a urethane resin (A), and an organic solvent, and may further contain the additives mentioned above. The printing ink can be obtained by stirring and mixing the colorant, urethane resin (A), and organic solvent, then dispersing the pigment using a known bead disperser, for example, the Mighty Mill (MHG-5) manufactured by Inoue Seisakusho Co., Ltd., and finally adding the organic solvent and additives as appropriate and stirring and mixing. From the viewpoint of pigment dispersibility and workability, the viscosity of the printing ink at 25°C is preferably 50 to 1,000 mPa·s. The solid content of the printing ink is preferably 20 to 60% by mass.

[0059] <Organic solvents contained in printing inks> Examples of organic solvents that can be used in printing inks include hydrocarbon-based solvents such as methylcyclohexane and ethylcyclohexane; ketone-based solvents such as acetone, methyl ethyl ketone (MEK), and methyl isobutyl ketone; ester-based solvents such as ethyl acetate, n-propyl acetate, and butyl acetate; and alcohol-based solvents such as methanol, ethanol, propanol, isopropanol (IPA), and butanol. The organic solvent may be selected appropriately considering the reduction of the amount of solvent remaining in the film after printing, and one type may be used alone or two or more types may be mixed. The content of the organic solvent is preferably 30 to 95% by mass, more preferably 50 to 90% by mass, and particularly preferably 70 to 85% by mass, based on 100% by mass of the printing ink.

[0060] Gravure printing Gravure version In gravure printing, the gravure plate is a cylindrical metal plate into which recesses of each color are formed by engraving, etching, or laser. There are no restrictions on the use of engraving or laser, and the settings can be arbitrarily determined according to the design. Line screen resolutions ranging from 80 to 250 are used as appropriate, with higher line screens allowing for finer printing.

[0061] Gravure printing press In a gravure printing press, one printing unit is equipped with the gravure plate and doctor blade. There are multiple printing units, and each unit has an oven drying unit. Printing is performed by rotary press using a roll printing method. The type of plate and doctor blade are selected as appropriate, and can be chosen according to the specifications.

[0062] <Surface protective layer> The surface protective layer is characterized by containing a cellulose-based resin (B) and an alkyd resin (C). The surface protective layer can be formed with an overcoat agent containing a cellulose-based resin (B) and an alkyd resin (C). Various printing methods such as gravure printing and flexographic printing, as well as various coating methods such as roll coating, can be used for applying the overcoat agent. From the viewpoint of productivity, gravure printing and roll coating methods are preferable, and processing can be performed simultaneously with the formation of the printed layer. The film thickness of the surface protective layer is 0.1 to 10 g / m². 2 Preferably, it is 0.5 to 7 g / m 2 It is more preferable that the amount be 1-3 g / m 2 It is even more preferable that it be within the range of [a certain range]. The content of cellulose resin (B) in the surface protective layer is preferably 25 to 80% by mass, more preferably 35 to 70% by mass, and even more preferably 45 to 65% by mass, based on 100% by mass of the surface protective layer. When the content of cellulose resin (B) in the surface protective layer is within the above range, there is a tendency for good alcohol resistance, crease resistance, adhesion, and blocking resistance. The content of alkyd resin (C) in the surface protective layer is preferably 5 to 80% by mass, more preferably 15 to 60% by mass, and even more preferably 25 to 45% by mass, based on 100% by mass of the surface protective layer. When the content of alkyd resin (C) in the surface protective layer is within the above range, there is a tendency for good alcohol resistance, crease resistance, adhesion, and blocking resistance. The solid content ratio of the cellulose resin (B) to the alkyd resin (C) in the surface protective layer is preferably 15:85 to 85:15, more preferably 30:70 to 80:20, and even more preferably 40:60 to 70:30. When the solid content ratio of the cellulose resin (B) to the alkyd resin (C) is within the above range, alcohol resistance, crease resistance, adhesion, and blocking resistance tend to be good. Furthermore, the total mass ratio of cellulose-based resin (B) and alkyd resin (C) in the surface protective layer is preferably 50% by mass or more, and more preferably 70% by mass or more, of 100% by mass of the surface protective layer. When the total content of cellulose-based resin (B) and alkyd resin (C) in the surface protective layer is within the above range, alcohol resistance and blocking resistance tend to be good.

[0063] <Cellulose resin (B)> Cellulose resin (B) can be derived from the contents of <Cellulose resin (B') contained in the printing layer> as described in <Printing layer>. The weight-average molecular weight (Mw) of the cellulose resin (B) is preferably 5,000 to 200,000, more preferably 8,000 to 100,000, and even more preferably 10,000 to 80,000. When the weight-average molecular weight (Mw) of the cellulose resin (B) is within the above range, there is a tendency for alcohol resistance, crease resistance, adhesion, and blocking resistance to improve. Furthermore, the glass transition temperature of the cellulose resin (B) is preferably 90°C to 200°C, more preferably 115°C to 180°C, and particularly preferably 140°C to 160°C. When the glass transition temperature of the cellulose resin (B) is within the above range, there is a tendency for alcohol resistance, crease resistance, adhesion, and blocking resistance to improve.

[0064] <Alkyd resin (C)> Alkyd resin (C) can be obtained, for example, by the method described in Japanese Patent Publication No. 58-108224, and includes resins obtained by condensation polymerization of a carboxylic acid compound and a fatty acid (or animal or vegetable oil) with an alcohol compound, and resins obtained by reacting an animal or vegetable oil or its fatty acid monoester with a carboxylic acid compound, followed by an esterification reaction of the alcohol compound. As an example of a synthesis method for obtaining the alkyd resin (C) used in the present invention, a carboxylic acid compound, a fatty acid, an alcohol compound, and reflux xylene are mixed, the temperature is raised to 180°C over several hours, the temperature is maintained at 180°C for 2 hours, and then the temperature is raised again to 210°C over several hours to obtain the alkyd resin (C). The reflux xylene contained in the obtained alkyd resin (C) can be removed by heating under reduced pressure. The method of obtaining the alkyd resin (C) that can be used in the present invention is not limited to the above. Commercially available products include the Arakid series manufactured by Arakawa Chemical Corporation.

[0065] Embodiments that satisfy the molecular weight distribution (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of the alkyd resin (C) used in the present invention will be described. When using the above synthesis method, the heating rate up to 180°C is preferably 30 to 150°C / hour, as a smaller heating rate improves the uniformity of the temperature within the system, thus increasing the tendency to satisfy the above molecular weight distribution. Furthermore, in the above synthesis method, the heating rate up to 210°C is preferably 1 to 30°C / hour, as a smaller heating rate improves the uniformity of the temperature within the system, thus increasing the tendency to satisfy the molecular weight distribution. In the above synthesis method, the stirring speed is preferably 100 to 1000 rpm, as a larger stirring speed improves the uniformity of the raw material composition within the system, thus increasing the tendency to satisfy the molecular weight distribution. Moreover, in the above synthesis method, known reaction catalysts such as dibutyltin oxodes can be used, and the inclusion of a reaction catalyst reduces the amount of unreacted raw materials, thus increasing the tendency to satisfy the molecular weight distribution.

[0066] The alkyd resin (C) used in the present invention preferably has a hydroxyl value of 5 to 200 mgKOH / g, more preferably 20 to 150 mgKOH / g. When the hydroxyl value of the alkyd resin (C) is within the above range, alcohol resistance is improved. The weight-average molecular weight (Mw) of the alkyd resin (C) is preferably 500 to 100,000, more preferably 2,000 to 70,000, and even more preferably 10,000 to 50,000. When the weight-average molecular weight (Mw) of the alkyd resin (C) is within the above range, alcohol resistance, crease resistance, and adhesion tend to improve. The molecular weight distribution (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of the alkyd resin (C) is preferably 5 to 20, more preferably 10 to 19, and even more preferably 13 to 17. When the molecular weight distribution of the alkyd resin (C) is within the above range, alcohol resistance, crease resistance, adhesion, and blocking resistance tend to improve. The acid value of the alkyd resin (C) is preferably 0.1 to 20 mg KOH / g, more preferably 1 to 10 mg KOH / g, and even more preferably 3 to 7 mg KOH / g. When the acid value of the alkyd resin (C) is within the above range, adhesion and crease resistance tend to improve.

[0067] The carboxylic acid compound used in the alkyd resin (C) is preferably a polybasic acid such as a dibasic acid, and suitable dibasic acids include aromatic carboxylic acids (including anhydrides) and alicyclic carboxylic acids (including anhydrides). Among these, aromatic carboxylic acids (including anhydrides) are preferred, and suitable compounds include phthalic anhydride, phthalic acid, isophthalic acid, and terephthalic acid.

[0068] Suitable alcohol compounds used in the alkyd resin (C) include alicyclic alcohols, aromatic alcohols, and alcohols without a cyclic structure, and the same as above can be suitably used. Among these, the use of alcohols without a cyclic structure is preferred, and suitable examples of such alcohols include dihydric alcohol compounds such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,5-hexanediol, 2,5-hexanediol, cyclohexanedimethanol, and nepenthyl glycol. Examples of trivalent or higher alcohol compounds include (mono, di, or tri)glycerin, (mono, di, or tri)trimethylolethane, (mono, di, or tri)trimethylolpropane, (mono, di, or tri)trimethylolalkane, (mono, di, or tri)pentaerythritol, and aliphatic polyhydric alcohols such as sorbitol.

[0069] Examples of the above-mentioned animal and vegetable oils include hemp seed oil, linseed oil, hackberry oil, oyster oil, olive oil, cocoa oil, kapok oil, kaya oil, mustard oil, apricot kernel oil, tung oil, kukui oil, walnut oil, poppy oil, sesame oil, safflower oil, radish seed oil, soybean oil, tahini oil, camellia oil, corn oil, rapeseed oil, niger oil, rice bran oil, palm oil, castor oil, sunflower oil, grape seed oil, henbit oil, pine seed oil, cottonseed oil, coconut oil, peanut oil, and dehydrated castor oil. Among these, soybean oil is preferred.

[0070] The above fatty acids may be mixed fatty acids, and suitable examples of fatty acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, palmitic acid, and stearic acid. Among these, from the viewpoint of the flexibility of the coating film, long-chain fatty acids with 12 or more carbon atoms, such as oleic acid, are preferred.

[0071] The above fatty acid monoesters include alkyl esters formed from the above fatty acids and alcohols, and suitable examples of alcohols include alcohols such as methanol, ethanol, propanol, isopropanol, butanol, and isobutanol.

[0072] <Additives contained in the surface protective layer> The additives included in the surface protective layer can be the same as those described in the <Additives included in the printing layer> section above. In particular, from the viewpoint of crease resistance and blocking resistance, it is preferable to include hydrocarbon wax and / or a chelating agent. The chelating agent content in the surface protective layer is preferably 0.1 to 15% by mass, and more preferably 1 to 8% by mass, based on 100% by mass of the surface protective layer. When the chelating agent content in the surface protective layer is within the above range, the crease resistance and blocking resistance tend to improve. The hydrocarbon wax content in the surface protective layer is preferably 0.1 to 15% by mass, and more preferably 1 to 8% by mass, based on 100% by mass of the surface protective layer. When the hydrocarbon wax content in the surface protective layer is within the above range, the blocking resistance tends to improve.

[0073] The total mass ratio of the urethane resin (A) contained in the printing layer and the alkyd resin (C) contained in the surface protection layer is preferably 10 to 40% by mass, more preferably 12 to 35% by mass, and even more preferably 15 to 25% by mass, out of 100% by mass of the total of the printing layer and the surface protection layer. When the total mass ratio of the urethane resin (A) contained in the printing layer and the alkyd resin (C) contained in the surface protection layer is such that a good balance between the toughness and flexibility of the printing layer and the surface protection layer is achieved, and thus alcohol resistance, crease resistance, adhesion, and blocking resistance tend to improve.

[0074] <Overcoat agent> The overcoat agent can be obtained by mixing and stirring a cellulose resin (B), an alkyd resin (C), and an organic solvent, and may contain any additives. From the viewpoint of workability, the viscosity of the overcoat agent at 25°C is preferably 50 to 1,000 mPa·s. The organic solvent contained in the overcoat agent can be determined by referring to the information described above under <Organic Solvents Contained in Printing Inks>. The solid content ratio of the overcoat agent is preferably 10 to 50% by mass.

[0075] <Heat seal layer> The heat seal layer is provided on the opposite side of the printed layer from the paper substrate and is used to bond the container during box making. It is formed by coating it with molten heat-sealable resin. The composition of the heat seal layer is not particularly limited as long as sufficient heat sealability is obtained during box making. Various heat-sealable resins can be used, such as polyolefin resins like polyethylene and polypropylene, ionomer resins, and acrylic resins. From the viewpoint of blocking resistance, it is preferable to include polyethylene resin. Various methods can also be used to create the heat seal layer, such as melt extrusion lamination, dry lamination, and heat-seal lacquer coating. The thickness of the heat seal layer is preferably 10 μm to 300 μm, more preferably 20 μm to 200 μm.

[0076] <Anchor Coat Layer> The laminate of the present invention preferably further has an anchor coat layer. The anchor coat layer is located between the paper substrate and the printing layer, and when printing ink to form the printing layer, it suppresses the penetration of printing ink into the paper substrate and improves the film-forming properties of the printing layer, which tends to improve adhesion, crease resistance, and blocking resistance. The resin included in the anchor coat layer can be polyethylene resin, polypropylene resin, rosin resin, styrene-acrylic copolymer resin, styrene-maleic acid copolymer resin, maleic acid resin, polyvinyl alcohol resin, starch resin, casein resin, vinyl acetate resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, urethane resin, acrylic resin, epoxy resin, polysaccharide ester, styrene-butadiene copolymer resin, or other styrene elastomer resins. One of these may be used alone, or two or more may be used in any proportion. Among these, polyethylene resin is preferred from the viewpoint of adhesion. The thickness of the anchor coat layer is preferably 1 to 50 μm, and more preferably 5 to 30 μm. The method for forming the anchor coat layer can be adapted from the description of the <heat seal layer> described above.

[0077] <Barrier layer> The packaging material of the present invention may further have a barrier layer. The position of the barrier layer is not limited, but it is preferably placed between the paper substrate layer and the heat seal layer. The barrier layer preferably contains an inorganic compound such as aluminum, alumina, or silica, and the purity of the inorganic compound is preferably 99% or higher, and more preferably 99.9% or higher. Aluminum may be used as aluminum foil, or an aluminum film may be formed by vapor deposition or the like. The thickness of the barrier layer is preferably 0.01 to 10 μm. The method for forming the barrier layer is not particularly limited, but for example, one method is to laminate aluminum foil to a paper substrate or the like using a known lamination method such as dry lamination. Alternatively, an inorganic compound layer can be formed on a paper substrate or the like using a known method such as vacuum deposition or sputtering. Furthermore, one method is to form a laminate on a known resin film such as polyethylene terephthalate film, on which a barrier layer has been formed using a known method such as vacuum deposition or sputtering, and then laminate that laminate to a paper substrate or the like using a known lamination method such as dry lamination. Vacuum deposition is performed using methods such as high-frequency induction heating, direct current heating, and electron beam heating, at temperatures of 1200-1500°C and 10-1 ~10 -2 The process is carried out under conditions of approximately Pa. Before vacuum deposition, the material to be deposited can undergo adhesion-enhancing treatment, such as corona discharge treatment on the surface. The sputtering method is 10 -1 ~10 -2 This is carried out by introducing an inert gas such as Ar under conditions of approximately Pa and applying a voltage load.

[0078] <Method for manufacturing laminates> The present invention relates to a method for manufacturing a laminate for a paper container having a heat seal layer, a paper substrate, a printed layer, and a surface protection layer in that order, and is characterized by comprising the steps of: applying a molten heat sealable resin to one surface of the paper substrate to form the heat seal layer; printing a printing ink containing a urethane resin (A) to one surface of the paper substrate to form the printed layer; and applying an overcoat agent containing a cellulose resin (B) and an alkyd resin (C) to the printed layer to form the surface protection layer. In the manufacturing method of the laminate, the heat-seal layer and the printed layer can be formed in any order. It is preferable to form the printed layer on the surface of the paper substrate that does not have a heat-seal layer after forming the heat-seal layer. Although the surface protection layer can be processed after the printed layer, it is desirable that the printed layer and the surface protection layer be processed in the same process using a printing press capable of applying multiple printing inks or overcoats, and that they be processed simultaneously. One example is a method in which polyethylene resin is laminated to the uncoated surface of single-sided coated paper by an extrusion lamination method to form a heat-seal layer, and then the printed layer and surface protection layer are created in the same process by gravure printing.

[0079] <Measurement of weight-average molecular weight (Mw) and number-average molecular weight (Mn)> The weight-average molecular weight (Mw) and number-average molecular weight (Mn) were measured under the following conditions. • Standard substance: polyethylene glycol • GPC device: Showa Denko Shodex GPC-104 • Column: Showa Denko Shodex LF-404 • Detector: RI (Differential Refractometer) • Column temperature: 35℃ • Eluent: Tetrahydrofuran ·Flow rate: 3mL / min

[0080] <Measuring amine titer> In this invention, the amine value is the number of milligrams of potassium hydroxide equivalent to the amount of hydrochloric acid required to neutralize the amino groups contained in 1 g of resin. The amine value was measured by the following method. Weigh 5-10 g of the sample accurately (S: mass of solids in g). Add 25 mL of toluene and 25 mL of n-butanol to the weighed sample and dissolve thoroughly. Add 30 mL of methanol and perform potentiometric titration with a 0.1 mol / L hydrochloric acid solution (f: titer). The amine value can be determined using the titration volume (A: mL) and the following formula (Equation 1).

[0081] (Formula 1) Amine value = (A × f × 0.1 × 56.108) / S [mgKOH / g]

[0082] <Measurement of Acid Value> In this invention, the acid value is the number of milligrams of potassium hydroxide required to neutralize the acidic groups contained in 1 g of resin solids, and was measured in accordance with JIS K0070.

[0083] <Measurement of hydroxyl value> In this invention, the hydroxyl value is calculated by acetylating the hydroxyl groups in the resin with an excess acetylating reagent, back-titrating the remaining acid with an alkali, and then converting the amount of hydroxyl groups in 1 g of resin to the number of mg of potassium hydroxide. This was measured in accordance with JIS K0070. [Examples]

[0084] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. It is not. Furthermore, in this invention, "parts" and "%" refer to "mass" unless otherwise noted. This represents "parts" and "mass %".

[0085] <Synthesis Example 1> Synthesis of Urethane Varnish PU1 In a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 21.89 parts of PMPA2000 (a polyester polyol, a condensate of 3-methyl-1,5-pentanediol with a number average molecular weight of 2000 and adipic acid, with a hydroxyl value of 56.1 mg KOH / g), 5.43 parts of IPDI (isophorone diisocyanate), 0.01 part of 2-ethylhexanoate tin(II), 8.99 parts of EtAc (ethyl acetate), and 7 parts of NPAc (n-propyl acetate) were charged. The mixture was reacted under a nitrogen stream at 90°C for 2 hours to obtain 43.32 parts of a solution of the terminal isocyanate prepolymer. Next, a mixture of 1.61 parts IPDA (isophorone diamine), 1.06 parts DBA (dibutylamine), 28.53 parts IPA (isopropyl alcohol), 18.48 parts ethyl acetate, and 7 parts NPAc was gradually added to the obtained solution of the terminal isocyanate prepolymer at room temperature. The mixture was then reacted at 50°C for 1 hour to obtain a polyurethane resin (urethane varnish PU1) with a solid content of 30%, a weight-average molecular weight (Mw) of 45,000, and an amine value of 0.26 mg KOH / g.

[0086] <Synthesis Examples 2 and 3> Synthesis of Urethane Resins PU2 and PU3 According to the formulations listed in Table 1, urethane varnishes PU2 and PU3 were obtained using the same procedure as in Synthesis Example 1. The raw materials used are as follows: PPG2000: Polypropylene glycol, number-average molecular weight = 2000 PCD2000: Polycarbonate diol, number-average molecular weight = 2000

[0087] [Table 1]

[0088] <Preparation of various varnishes> Commercially available industrial nitrated cotton (H1 / 8, manufactured by Inabata Sangyo Co., Ltd.), cellulose acetate propionate (CAP-482-0.5, manufactured by Daicel Corporation), solid acrylic resin (Dianal BR106, manufactured by Mitsubishi Chemical Corporation), solid vinyl chloride vinyl acetate resin (Solvine A, manufactured by Nisshin Chemical Industry Co., Ltd.), and solid polyester resin (Byron 300, manufactured by Toyobo Co., Ltd.) were dissolved in ethyl acetate to obtain nitrocellulose varnish, cellulose acetate propionate varnish, acrylic varnish, vinyl chloride vinyl acetate varnish, and polyester varnish, each with a solid content of 30%.

[0089] <Preparation of overcoat agent> Overcoat agent X1 was obtained by mixing 15.00 parts of alkyd varnish A1, 45.00 parts of nitrocellulose varnish, 22.90 parts of ethyl acetate, 12.00 parts of IPA, 1.60 parts of polyethylene wax (High Flat X7019, 100% solids), and 3.50 parts of titanium chelating agent (Orgatic TC100, 33% solids). Similarly, overcoat agents X2 to X18 were obtained according to Tables 2-1 and 2-2. The alkyd resin (C) used is as follows: Alkyd varnish A1: Soybean oil-based alkyd resin, Mw 40000, Mw / Mn = 15, solids content 60%, hydroxyl value = 55 mg KOH / g, acid value = 3.8 mg KOH / g, solvent: ethyl acetate Alkyd varnish A2: Soybean oil-based alkyd resin, Mw 34000, Mw / Mn = 3, solids content 60%, hydroxyl value = 53 mg KOH / g, acid value = 0.8 mg KOH / g, solvent: ethyl acetate Alkyd varnish A3: Soybean oil-based alkyd resin, Mw 35000, Mw / Mn = 8, solids content 60%, hydroxyl value = 55 mg KOH / g, acid value = 1.5 mg KOH / g, solvent: ethyl acetate Alkyd varnish A4: Soybean oil-based alkyd resin, Mw 36000, Mw / Mn = 11, solids content 60%, hydroxyl value = 52 mg KOH / g, acid value = 3.0 mg KOH / g, solvent: ethyl acetate Alkyd varnish A5: Soybean oil-based alkyd resin, Mw 42000, Mw / Mn = 18, solids content 60%, hydroxyl value = 55 mg KOH / g, acid value = 4.1 mg KOH / g, solvent: ethyl acetate Alkyd varnish A6: Soybean oil-based alkyd resin, Mw 45000, Mw / Mn = 22, solids content 60%, hydroxyl value = 57 mg KOH / g, acid value = 4.2 mg KOH / g, solvent: ethyl acetate

[0090] [Table 2-1]

[0091] [Table 2-2]

[0092] <Ink preparation> 25.00 parts nitrocellulose varnish, 11.00 parts red pigment (Toyo Color Co., Ltd. LIONOLRED5620, 100% solids), 13.00 parts ethyl acetate, and 8.0 parts IPA were placed in a 225cc mayonnaise bottle, 100g of 5mmφ glass beads were added, and the mixture was shaken with paint conditioner for 60 minutes to disperse and create a mill base. Next, 10.00 parts urethane varnish PU1, 4.0 parts nitrocellulose varnish, 14.00 parts ethyl acetate, 7.00 parts IPA, 4.00 parts polyethylene wax (Gifu Shellac Co., Ltd., High Flat X7019, 100% solids), 2.00 parts plasticizer (tributyl acetyl citrate, 100% solids), and 2.00 parts chelating agent (Matsumoto Fine Chemical Co., Ltd., Orgatic TC100, 33% solids) were added to the same container and mixed to obtain ink Y1. Inks Y2-9 were obtained using the formulations shown in Table 3 by the same procedure.

[0093] [Table 3]

[0094] <Example 1> Laminate P1 Paperboard (basis weight 400g / m²) 2 Polyethylene resin (Sumitomo Chemical Co., Ltd., Sumikasen L417) was coated onto one side of the paperboard using an extrusion lamination method, and an aluminum foil (7 μm thick) was laminated to the polyethylene resin to form a barrier layer. Furthermore, polyethylene resin (Sumitomo Chemical Co., Ltd., Sumikasen L417) was coated again using an extrusion lamination method to form a heat seal layer with a thickness of 30 μm. Subsequently, polyethylene resin (Sumitomo Chemical Co., Ltd., Sumikasen L417) was coated onto the side of the paperboard without the barrier layer using an extrusion lamination method to form an anchor coat layer with a thickness of 15 μm. Next, printing ink Y1 was printed onto the anchor coat layer by gravure printing, and then volatile components were removed in an in-line oven at 60°C to form a printed layer. Subsequently, overcoat agent X1 was printed onto the printed layer by gravure printing, and then volatile components were removed in an in-line oven at 60°C to form a surface protective layer and obtain laminate P1. The printing conditions at this time were set to 15 seconds using a Zahn cup #3 manufactured by Rigosha, the printing ink was diluted with a mixed solvent of ethyl acetate / IPA=7 / 3, and the overcoat agent was diluted with ethyl acetate alone, and printing was performed using a laser plate making system with a solid plate of 175 LPI and a plate depth of 35 μm.

[0095] <Examples 2-20, 22-24, Comparative Examples 1-9> Laminates P2-20, 22-24, and PP1-9 were obtained in the same manner as in Example 1, except that the overcoat agent, printing ink, and heat seal layer resin were changed as shown in Tables 4-1, 4-2, and 4-3.

[0096] <Example 21> Laminate P19 was obtained in the same manner as in Example 1, except that the resin of the anchor coat layer was changed to acrylic resin (Parapet G, manufactured by Kuraray Co., Ltd.).

[0097] <Example 25> Laminate P25 was obtained in the same manner as in Example 1, except that the resin of the heat seal layer was changed to EVA (ethylene vinyl acetate resin, manufactured by Mitsui Dow Polychemicals, Evaflex EV450).

[0098] <Comparative Example 10> Laminate PP10 was obtained in the same manner as in Example 1, except that the base material was changed to a chain-like low-density polyethylene film (thickness 30 μm).

[0099] The following physical property tests were performed on the resulting laminate.

[0100] (Alcohol-resistant) The surface of the laminate's protective layer was rubbed back and forth 30 times using a cotton swab dipped in a 75% ethanol aqueous solution, and the degree to which the printed layer was removed was evaluated. A, B, and C represent ranges that are practically acceptable. A: No removal of the printed layer from the cotton ball. B: Slight transfer of the printed layer is observed on the cotton ball, but the appearance of the laminate remains unchanged. C: Transfer of the printed layer to the cotton ball is observed, but the appearance of the laminate remains unchanged. D: Transfer of the printed layer to the cotton ball was observed, and the printed layer was slightly lost. E: Many print layers were transferred to the cotton ball, and the print layers disappeared.

[0101] (Crease resistance) The obtained laminate was cut into 100 mm squares, and with the heat-seal layer facing inward, the laminate was folded at a 90° angle so that folds could be formed in the areas with the heat-seal layer / barrier layer / paper substrate / anchor coat layer / printed layer / surface protection layer configuration. The appearance of the printed layer at the folded area was then visually evaluated. A, B, and C are within a range that is practically acceptable. For Example 22, which does not have an anchor coat layer, folds were formed in the areas with the heat-seal layer / barrier layer / paper substrate / printed layer / surface protection layer configuration, and the evaluation was performed accordingly. A: No cracks are visible in the printed layer. B: Some cracks are visible in the printed layer, but no peeling of the printed layer is observed. C: Cracks are visible in the printed layer, but no peeling of the printed layer is observed. D: Cracks are visible in the printed layer, and some peeling of the printed layer is observed. E: Cracks and peeling of the printed layer are visible.

[0102] (Adhesion) A piece of Nichiban cellophane tape (150mm long, 12mm wide) was applied to the protective surface layer of the laminate. After rubbing it five times with a thumb, the tape was slowly peeled off about halfway through the application area, and then rapidly peeled off. The degree of ink peeling was evaluated based on the area. A, B, and C represent ranges that are acceptable for practical use. A: No ink peeling in the areas where rapid peeling occurred. B: No ink peeling was observed in the areas where the peeling occurred slowly, but peeling was observed in areas where the peeling occurred rapidly, with an area percentage exceeding 0% and an area percentage of 25% or less. C: No ink peeling was observed in the areas where the peeling occurred slowly, but peeling exceeding 25% of the area was observed in the areas where the peeling occurred rapidly. D: In the areas where peeling occurred slowly, peeling was observed in areas exceeding 0% and less than 25% of the area. E: Peeling exceeding 25% area was observed in the slowly peeling portion.

[0103] (Blocking resistance) Two 40mm square pieces were cut from the resulting laminate. The heat-sealed layer of one packaging material piece and the surface protective layer of the other packaging material piece were completely overlapped. After being left to stand for 24 hours at 50°C and 80% RH under a load of 1 MPa, the two overlapping laminates were separated, and the peeling state of the printed layer was visually observed and evaluated according to the following criteria. Grades A, B, and C represent a range that is acceptable for practical use. A: No transfer of the printed layer to the heat seal layer. B: The amount of print layer transferred to the heat seal layer is greater than 0 area % and 10 area % or less. C: The amount of print layer transferred to the heat seal layer is greater than 10 area percent and 25 area percent or less. D: The amount of print layer transferred to the heat seal layer is greater than 25 area percent and less than or equal to 50 area percent. E: The amount of print layer transferred to the heat seal layer exceeds 50 area.

[0104] [Table 4-1]

[0105] [Table 4-2]

[0106] [Table 4-3]

[0107] [Table 4-4]

[0108] From the results above, Comparative Example 1 had poor alcohol resistance and blocking resistance because its surface protective layer contained urethane resin and alkyd resin (C) but did not contain cellulose resin (B). Comparative Example 2 had poor crease resistance because its surface protective layer contained acrylic resin and alkyd resin (C) but did not contain cellulose resin (B). Comparative Example 3 had poor crease resistance because its surface protective layer contained cellulose resin (B) and polyester resin but did not contain alkyd resin (C). Comparative Example 4 had poor alcohol resistance and blocking resistance because its surface protective layer contained only urethane resin. Comparative Example 5 had poor crease resistance and adhesion because its surface protective layer contained only acrylic resin. Comparative Example 6 had poor crease resistance because its surface protective layer contained only alkyd resin (C). Comparative Examples 7 and 8 had poor crease resistance and adhesion because their printing layers did not contain urethane resin (A). Comparative Example 9 had a paper substrate with a basis weight of 100 g / m². 2 Because the value was less than [value missing], the crease resistance was poor. Comparative Example 10 had poor crease resistance because the base material was polyethylene film. On the other hand, the example showed good alcohol resistance, crease resistance, adhesion, and blocking resistance because the surface protective layer contained a cellulose resin (B) and an alkyd resin (C), and the printed layer contained a urethane resin (A).

Claims

1. A laminate for paper containers having a heat-seal layer, a paper substrate, a printing layer, and a surface protection layer in this order, The basis weight of the aforementioned paper substrate is 100 g / m². ２ That's all. The printed layer comprises urethane resin (A), A laminate in which the surface protective layer comprises a cellulose resin (B) and an alkyd resin (C).

2. The laminate according to claim 1, wherein the molecular weight distribution (Mw / Mn) of the alkyd resin (C) in the surface protective layer is 5 to 20.

3. The laminate according to claim 1 or 2, wherein the solid content mass ratio of the cellulose resin (B) and the alkyd resin (C) in the surface protective layer is 15:85 to 85:

15.

4. The laminate according to claim 1 or 2, wherein the printed layer further comprises at least one selected from the group consisting of cellulose resin (B'), vinyl resin, and acrylic resin.

5. The laminate according to claim 1 or 2, wherein the urethane resin (A) in the printed layer includes a polyether-derived structure and / or a polyester-derived structure.

6. The laminate according to claim 1 or 2, wherein the total mass ratio of cellulose resin (B) and alkyd resin (C) in the surface protective layer is 50% by mass or more of 100% by mass of the surface protective layer.

7. The laminate according to claim 1 or 2, wherein the total mass ratio of the urethane resin (A) in the printing layer and the alkyd resin (C) in the surface protection layer is 10 to 40% by mass of the total mass of the printing layer and the surface protection layer.

8. The laminate according to claim 1 or 2, further comprising an anchor coat layer between the paper substrate and the printed layer.

9. The laminate according to claim 1 or 2, wherein the heat seal layer contains polyethylene resin.

10. The laminate according to claim 1 or 2, wherein the 60-degree gloss value of the surface protective layer, as measured by the method described in JIS Z 8741:1997, is 15 to 45.

11. The laminate according to claim 1 or 2, which is for use as a sake pack container.

12. A method for manufacturing a laminate for paper containers having a heat seal layer, a paper substrate, a printing layer, and a surface protection layer in this order, The basis weight of the aforementioned paper substrate is 100 g / m². ２ That's all. A step of forming the heat seal layer by coating one surface of the paper substrate with molten heat sealable resin, A step of forming the printed layer by printing a printing ink containing urethane resin (A) onto the other surface of the paper substrate, A method for manufacturing a laminate, comprising the step of applying an overcoat agent containing a cellulose resin (B) and an alkyd resin (C) onto the printed layer to form the surface protective layer.

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