JP7543991B2 - Water-based overcoat agent, laminate for packaging material, packaging material - Google Patents

Description

One embodiment of the present invention relates to an aqueous overcoat agent. Another embodiment of the present invention relates to a laminate for packaging materials and a packaging material using the laminate.

Examples of packaging materials include flexible packaging packages and packaging bags that use film substrates such as polyester film, nylon film, and polyolefin film. The film substrates of these packaging materials usually have a printing layer using ink to provide design, aesthetics, and product information. Printing of ink onto film substrates can be broadly divided into front printing, where printing is done directly on the front side of the substrate film, and back printing, where ink is printed on the back side of the substrate film.

When producing a packaging bag with a reverse printing configuration, the printing layer is sandwiched (laminated) between a film substrate and a thermoplastic substrate having heat sealability, called a sealant. In other words, since the outermost layer of the packaging bag is the film substrate, the printing layer can be seen through the film substrate. Furthermore, with a reverse printing configuration (hereinafter also referred to as a laminated laminate), the physical properties of the film substrate itself, which is the outermost layer of the packaging bag, are effectively utilized. Therefore, compared to a front printing configuration in which the outermost layer of the packaging bag is a printing layer, a reverse printing configuration has the characteristic that high gloss and scratch resistance can be easily obtained.

However, the method of producing packaging bags with reverse printing requires applying ink to a film substrate to form a printed layer, and then laminating another film on top of the printed layer, which requires many steps and is time-consuming. Furthermore, due to the large number of steps, various properties such as adhesion between the film substrate and the printed layer and delamination (floating) are often insufficient. This requires the use of adhesives or additional lamination steps, and improvements are desired in terms of production efficiency and production costs.

On the other hand, when producing packaging bags using a front-side printing configuration, the printed layer is placed on the outermost side. Therefore, the printed layer can be directly observed, but it has a poorer gloss than a back-side printing configuration in which the printed layer can be observed through the film substrate. Furthermore, front-side printing configurations often have poorer scratch resistance and heat resistance (Patent Document 1).

Therefore, in order to achieve high gloss and heat resistance even in packaging bags with a surface-printed configuration, a method of forming a transparent protective layer on the surface of the surface-printed layer using an overcoat agent has been investigated. This method is expected to make it possible to impart gloss and scratch resistance to the same extent as a laminated body without going through the complicated manufacturing process required for a laminated body.

Amide resin-based overcoat agents (Patent Document 2) and polylactic acid-based overcoat agents (Patent Document 3) have been proposed. However, no matter which overcoat agent is used to form a transparent protective layer on the surface of the printed layer, the print does not reach a fully satisfactory level in terms of properties such as gloss and heat resistance when compared with a laminate.

In particular, in the bag-making process that typically forms packaging bags, a process is required in which the printed materials are overlapped and pressed between a high-temperature tool to heat-seal the substrates (to perform heat sealing). When forming a packaging bag with the above-mentioned surface-printing configuration, for example, ink is applied to the surface of a substrate that does not have heat-sealing properties to form a printed layer, while another substrate that has heat-sealing properties is laminated to the back surface of the substrate, and the other substrate that has heat-sealing properties is placed opposite the substrate to perform the heat-sealing process (Patent Document 4). In this process, the tool of the heat-sealing machine is at a high temperature, and in a printed material in which a surface protective layer is formed on the surface of the printed layer, the transparent protective layer is in direct contact with the high-temperature tool. Therefore, the heat-sealed portion of the transparent protective layer is easily deteriorated by heat, and it is difficult to obtain a sufficient gloss.

JP 2019-119824 A JP 2016-079306 A JP 2003-147265 A JP 2000-153582 A

As described above, in packaging materials with a surface printing configuration, it is desired to improve the gloss of the transparent protective layer, especially the gloss of the heat-sealed portion. In addition, from the viewpoint of the use of the packaging material such as a packaging bag, it is preferable that the transparent protective layer has excellent kneading resistance. Therefore, there is a need for an overcoat agent that can form a surface protective layer that is excellent in heat resistance, can easily obtain a desired gloss, and has excellent kneading resistance. In particular, in recent years, there is a demand for reducing the use of organic solvents from the viewpoint of environmental load, and therefore there is an increasing need for an aqueous overcoat agent.
In this situation, one embodiment of the present invention provides an aqueous overcoat agent that is excellent in heat resistance, can improve the gloss of the heat-sealed portion, and can form a surface protective layer that is excellent in kneading resistance.

As a result of extensive research into overcoat agents for forming a surface protective layer, the inventors discovered that the above problems could be solved by using a specific binder resin, and thus completed the present invention. That is, the present invention relates to the following embodiments. However, the present invention is not limited to the following embodiments, and includes various embodiments.

One embodiment of the present invention relates to an aqueous overcoat agent containing at least a binder resin for forming a transparent protective layer on a print layer provided on at least a portion of the surface of a sealant substrate. In the aqueous overcoat agent, the binder resin contains an aqueous (meth)acrylic resin, and the content of the aqueous (meth)acrylic resin is 40% by mass or more based on the total mass of the solid content in the binder resin, and the proportion of ring structures contained in the binder resin is 0.5 to 30% by mass.

In the above embodiment, the acid value of the aqueous (meth)acrylic resin is preferably 150 mg KOH/g or less.
The glass transition temperature (Tg) of the binder resin is preferably 100° C. or lower.

The binder resin further contains a polyester resin, and the ratio of the content of the aqueous (meth)acrylic resin to the content of the polyester resin is preferably 95:5 to 40:60.

The binder resin preferably contains at least one of an aqueous (meth)acrylic resin containing a ring structure and an aqueous polyester resin containing a ring structure, and an aqueous (meth)acrylic resin that does not contain a ring structure.

The aqueous overcoat agent of the above embodiment preferably further contains a phosphate ester surfactant.

Another embodiment of the present invention relates to a laminate for a packaging material having a sealant substrate, a printed layer provided on at least a portion of a surface of the sealant substrate, and a transparent protective layer provided on the printed layer, wherein the transparent protective layer is formed using the aqueous overcoat agent of the above embodiment.
In the above embodiment, the gloss value (60°) of the surface on the transparent protective layer side is preferably 70 or more.

Another embodiment of the present invention relates to a packaging material using a laminate for packaging materials having a sealant substrate, a printed layer provided on at least a portion of the surface of the sealant substrate, and a transparent protective layer provided on the printed layer, the packaging material having a joint formed by heat sealing the sealant substrate.

According to one embodiment of the present invention, it is possible to provide an aqueous overcoat agent that has excellent heat resistance, can improve the gloss of heat-sealed parts, and can form a surface protective layer that has excellent kneading resistance. In addition, by using this aqueous overcoat agent, it is possible to provide a laminate for packaging materials that can exhibit excellent gloss in packaging materials having heat-sealed parts such as packaging bags.

1 is a schematic cross-sectional view showing an example of the structure of a laminate for packaging material according to one embodiment of the present invention. 1 is a schematic cross-sectional view showing an example of the structure of a laminate for packaging material according to one embodiment of the present invention. 1 is a schematic diagram showing an example of the structure of a packaging material according to one embodiment of the present invention. FIG.

The following describes in detail an embodiment of the present invention. However, the following description of the embodiment or requirements is merely an example of how the present invention can be implemented, and the present invention is not limited to these details as long as it does not exceed the gist of the invention.

<1> Aqueous overcoat agent One embodiment relates to an aqueous overcoat agent containing at least a binder resin. This overcoat agent contains an aqueous solvent such as water or a mixture of water and an organic solvent, and can be suitably used to form a transparent protective layer on a printed layer provided on at least a part of the surface of a sealant substrate. That is, the transparent protective layer is preferably provided as the outermost layer of a surface-printed structure.
In this specification, surface printing is defined as a case where, when printing is performed on a substrate such as a paper substrate or a plastic substrate, the printing ink and the aqueous overcoat agent are printed on the substrate in that order, and the printed pattern can be confirmed from the printed surface. The transparent protective layer formed from the aqueous overcoat agent becomes the outermost layer of the printed matter. Each material constituting the aqueous overcoat agent will be described below.

(Binder resin)
In the above aqueous overcoat agent, the binder resin means a resin that is a main component contained in the overcoat agent, and is a component that forms a film. In the above embodiment, the binder resin contains at least an aqueous (meth)acrylic resin, and the content of the aqueous (meth)acrylic resin may be 40 mass% or more based on the total mass of the solid content in the binder resin. In addition, the binder resin preferably contains a ring structure, and the ratio of the ring structure contained in the binder resin is preferably 0.5 to 30 mass% based on the total mass of the resin.

In one embodiment, the glass transition temperature (Tg) of the binder resin is preferably 100°C or less from the viewpoint of resistance to kneading. The Tg of the binder resin may more preferably be 0 to 85°C, and even more preferably be 5 to 60°C.

(Water-based (meth)acrylic resin)
The aqueous (meth)acrylic resin may be soluble in the aqueous solvent constituting the aqueous overcoat agent (i.e., water-soluble) or water-dispersible. In one embodiment, the aqueous (meth)acrylic resin may be in any of the following forms: emulsion type resin, self-water-dispersible resin, alkali-soluble resin, and hydrosol type resin. In one embodiment, the aqueous (meth)acrylic resin is preferably an emulsion type resin.

The aqueous (meth)acrylic resin may be a polymer or copolymer obtained by polymerizing a monomer component mainly composed of (meth)acrylic acid and/or (meth)acrylate. Hereinafter, the aqueous (meth)acrylic resin may be referred to as an aqueous (meth)acrylic resin.
Here, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid". "(meth)acrylate" refers to both "acrylate" and "methacrylate". As a monomer component constituting the aqueous (meth)acrylic resin, an ethylenically unsaturated monomer having an acid group other than (meth)acrylic acid may be further used.

Examples of the (meth)acrylate include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, behenyl acrylate, trimethylcyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; and aromatic (meth)acrylates such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate;
Heterocyclic (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and oxetane (meth)acrylate; alkoxypolyalkylene glycol (meth)acrylates such as methoxypolypropylene glycol (meth)acrylate and ethoxypolyethylene glycol (meth)acrylate;
Examples of the compound include N-substituted (meth)acrylamides such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, diacetone(meth)acrylamide, and acryloylmorpholine; amino group-containing (meth)acrylates such as N,N-dimethylaminoethyl(meth)acrylate and N,N-diethylaminoethyl(meth)acrylate; and nitriles such as (meth)acrylonitrile.

In one embodiment, the monomer components constituting the aqueous (meth)acrylic resin may further contain, in addition to (meth)acrylic acid and/or (meth)acrylate, a carboxyl group-containing ethylenically unsaturated monomer and/or an ethylenically unsaturated monomer other than these monomers. Examples of the carboxyl group-containing ethylenically unsaturated monomer include itaconic acid, maleic acid, fumaric acid, and crotonic acid.
Examples of the ethylenically unsaturated monomer include styrene-based monomers such as styrene and α-methylstyrene, and vinyl-based monomers such as vinyl acetate and vinyl chloride. Among these, it is preferable to use styrene-based monomers, which can easily obtain excellent gloss.

In one embodiment, the aqueous (meth)acrylic resin may be a copolymer of (meth)acrylic acid and/or (meth)acrylate with a styrene-based monomer. More specifically, the aqueous (meth)acrylic resin may be an emulsion resin obtained by copolymerization of (meth)acrylic acid, (meth)acrylate, and styrene. The emulsion resin may be prepared according to a method known in the art. For example, the emulsion resin may be prepared by carrying out emulsion polymerization under conditions in which the monomer components are emulsified in a micellar form and dispersed in water. For example, the emulsion polymerization may be carried out in the presence of ammonium persulfate and sodium metabisulfite. After the emulsion polymerization, a basic compound such as aqueous ammonia may be added to adjust the acid value of the resin, if necessary.

Specific examples of monomer combinations constituting an aqueous (meth)acrylic resin (aqueous (meth)acrylic resin) include, but are not limited to, acrylic acid/styrene/n-butyl methacrylate/2-ethylhexyl acrylate, acrylic acid/methyl methacrylate/1,4-cyclohexanedimethanol monoacrylate/n-butyl methacrylate/2-ethylhexyl acrylate, acrylic acid/styrene/n-butyl methacrylate, methacrylic acid/methyl methacrylate/styrene, acrylic acid/styrene/n-butyl methacrylate/2-ethylhexyl acrylate, etc.

In one embodiment, the aqueous (meth)acrylic resin may be neutralized to improve its solubility or dispersibility in aqueous solvents. For example, after acid groups such as carboxyl groups are introduced during the synthesis of the resin, some or all of the acid groups can be neutralized to increase hydrophilicity. The neutralization of the carboxyl groups can be carried out using amines such as triethylamine or other basic compounds.

In one embodiment, the content of the aqueous (meth)acrylic resin may be preferably 40% by mass or more based on the total mass of the binder resin. The content may be more preferably 50% by mass or more, and even more preferably 60% by mass or more. In one embodiment, the content of the aqueous (meth)acrylic resin may be 100% by mass.

In one embodiment, the ratio of the ring structure contained in the binder resin is preferably 0.5 to 30% by mass from the viewpoint of obtaining a desired gloss, more preferably 1 to 25% by mass, and further preferably 5 to 20% by mass.
The above-mentioned "ring structure" may be an aromatic ring, an aliphatic ring, or a heterocyclic ring, and means only the moiety constituting the ring, and does not include the substituent. The ring structure may be a pyranose group.
The "proportion of ring structure" refers to the proportion of the total mass of only ring structures such as aromatic rings, aliphatic rings, and heterocyclic rings based on the total mass of the binder resin (solid content). The solid content refers to the total mass of non-volatile components. The specific proportion is calculated based on the monomers that constitute the binder resin. For example, in the case of styrene, only the benzene ring portion is a ring structure, and the benzene ring portion is calculated as the mass of the ring structure.

To form the (meth)acrylic resin having the above ring structure, for example, an acrylic monomer having an aromatic ring can be used. Specific examples include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate. In addition, a styrene monomer such as styrene or α-methylstyrene can be used in combination with an acrylic monomer to form a (meth)acrylic resin having the above ring structure.

Acrylic monomers and styrene monomers having an aromatic ring can be referred to as aromatic monomers. When these aromatic monomers are used, it is easy to improve the gloss value of the transparent protective layer formed from the overcoat agent. In one embodiment, the transparent protective layer preferably contains 5 to 80% by mass of structural units derived from aromatic monomers, based on the total mass of the transparent protective layer, and more preferably contains 20 to 60% by mass.

In one embodiment, the acid value of the aqueous (meth)acrylic resin may be preferably 150 mgKOH/g or less. The acid value is more preferably 5 to 120 mgKOH/g, and even more preferably 5 to 100 mgKOH/g. When the acid value of the aqueous (meth)acrylic resin is within the above range, it is easy to obtain water resistance.

In one embodiment, the weight average molecular weight of the aqueous (meth)acrylic resin is preferably 5,000 to 2,000,000. The weight average molecular weight is more preferably 10,000 to 1,800,000, and even more preferably 15,000 to 1,600,000. When the weight average molecular weight of the aqueous (meth)acrylic resin is within the above range, it is easy to obtain heat resistance. The weight average molecular weight can be easily adjusted by a method well known in the art. For example, the weight average molecular weight can be easily adjusted to the desired weight average molecular weight by measuring the viscosity during resin synthesis.

In one embodiment, when the aqueous (meth)acrylic resin is an emulsion type resin, the weight average molecular weight of the aqueous (meth)acrylic resin may be preferably 50,000 to 2,000,000. The weight average molecular weight is more preferably 80,000 to 1,800,000, and further preferably 100,000 to 1,600,000.
The acid value may be preferably 150 mgKOH/g or less, more preferably 5 to 120 mgKOH/g, and even more preferably 5 to 100 mgKOH/g.

In one embodiment, the aqueous (meth)acrylic resin preferably includes both an "aqueous (meth)acrylic resin not containing a ring structure" and an "aqueous (meth)acrylic resin containing a ring structure". In this case, the (meth)acrylic resin including both preferably satisfies the requirements for the content of the ring structure and the weight average molecular weight.
The mass ratio of the "(meth)acrylic resin not containing a ring structure" to the "(meth)acrylic resin containing a ring structure" is preferably 90:10 to 20:80, and more preferably 70:30 to 30:70. In such an embodiment, it is preferable that the mixture containing both of the (meth)acrylic resins satisfies the requirements for acid value, glass transition temperature, and weight average molecular weight described above.

As described above, when (meth)acrylic resins containing a ring structure/not containing a ring structure are used in combination, the ring structure in the "(meth)acrylic resin containing a ring structure" is as described above. That is, the ring structure may be an aromatic ring, an aliphatic ring, or a heterocyclic ring. The ring structure is preferably an aromatic ring or an aliphatic ring, and more preferably has an aromatic ring.

In one embodiment, the "(meth)acrylic resin containing a ring structure" may be as follows. Based on the total mass of the resin, the ring structure is preferably contained in an amount of 3 to 70 mass%, and more preferably 5 to 60 mass%. The weight average molecular weight of the resin is preferably 5,000 to 500,000. The weight average molecular weight is more preferably 10,000 to 500,000, and even more preferably 50,000 to 300,000. The acid value of the resin is preferably 1 to 300 mgKOH/g, and more preferably 5 to 250 mgKOH/g. The glass transition temperature of the resin is preferably 15 to 150°C, and more preferably 20 to 120°C.

When (meth)acrylic resins containing/not containing a ring structure are used in combination as described above, in one embodiment, the "(meth)acrylic resin not containing a ring structure" preferably has the same weight average molecular weight as described above. The weight average molecular weight of the resin is preferably 500,000 to 2,000,000, and more preferably 1,000,000 to 1,800,000. The acid value of the resin is preferably 1 to 60 mgKOH/g, and more preferably 5 to 40 mgKOH/g. The glass transition temperature of the resin is preferably -10 to 50°C, and more preferably 0 to 40°C.

In one embodiment, the binder resin may further contain other resins in addition to the above-mentioned aqueous (meth)acrylic resin. Examples of resins that can be used include at least one selected from the group consisting of aqueous polyester resins, polyamide resins, vinyl chloride-vinyl acetate copolymer resins, and the like, rosin resins, polyvinyl butyral resins, aqueous urethane resins, aqueous maleic acid resins, and polyvinyl alcohol. In one embodiment, it is preferable that the binder resin further contains an aqueous polyester resin.

(Water-based polyester resin)
The aqueous polyester resin is not particularly limited and is appropriately produced by a known method. The aqueous polyester resin may have solubility (i.e., water solubility) or water dispersibility in the aqueous solvent constituting the aqueous overcoat agent. The aqueous polyester resin preferably has a ring structure similar to the aqueous (meth)acrylic resin described above. The ring structure is preferably an aromatic ring and/or an alicyclic ring. The content of the ring structure in the aqueous polyester resin is preferably 1 to 80 mass %, more preferably 10 to 50 mass %, based on the total mass of the resin. The aqueous polyester resin may be, for example, a polyester resin obtained by reacting a polyhydric alcohol with an acid component containing a polycarboxylic acid using a known esterification polymerization reaction, or an alkyd resin.

The weight average molecular weight of the aqueous polyester resin is preferably 500 to 100,000, and more preferably 2,000 to 50,000. When an aqueous polyester resin having the above weight average molecular weight is used, adhesion, blocking resistance, and work efficiency in the ink printing process are improved, and excellent printability can be easily obtained.

The polyhydric alcohol constituting the aqueous polyester resin may be, for example, an alicyclic polyhydric alcohol, specific examples of which include 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, spiroglycol, and isosorbide.
The polyhydric alcohols can be used alone or in combination of two or more kinds. Monofunctional alcohols such as cyclohexanol, cyclohexaneethanol, 4-tert-butylcyclohexanol, menthol, 2-ethyl-4-(2,2,3-trimethyl-3-cyclopentenyl)-2-buten-1-ol, 4-isopropylcyclohexanol, and 2-(tert-butyl)cyclohexanol can also be used in combination.

The polyhydric alcohol constituting the aqueous polyester resin may be an aromatic polyhydric alcohol. Specific examples include 1,4-benzenedimethanol, 1,3-bis(2-hydroxyethoxy)benzene, 1,2-bis(2-hydroxyethoxy)benzene, 1,4-bis(2-hydroxyethoxy)benzene, hydroquinone, 2,2-bis(4-β-hydroxyethoxyphenyl)propane, etc. These may be used alone or in combination of two or more.

The polybasic carboxylic acid constituting the aqueous polyester resin may be a dibasic acid. The dibasic acid may be, for example, an alicyclic dibasic acid, and specific examples include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,1-cyclopentanediacetic acid, and decahydro-1,4-naphthalenedicarboxylic acid.

The dibasic acid constituting the aqueous polyester resin may be an aromatic dibasic acid.
Specific examples include phthalic acid, isophthalic acid, terephthalic acid, 1,2-phenylene diacetic acid, 1,3-phenylene diacetic acid, 1,4-phenylene diacetic acid, and 4-(carboxymethyl)benzoic acid, etc. These can be used alone or in combination of two or more.

As a monomer component constituting the above-mentioned aqueous polyester resin, a polyhydric alcohol having no ring structure or a dibasic acid having no ring structure can also be used.

Examples of polyhydric alcohols that do not have an alicyclic structure include, but are not limited to, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,2-pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, and pentaerythritol.

Dibasic acids without a ring structure are not particularly limited, but examples thereof include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. If necessary, monobasic acids such as formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, and linoleic acid may be used in combination.

Acid anhydrides may be further used as an acid component during the esterification polymerization reaction. Although not particularly limited, examples include succinic anhydride, methyl succinic anhydride, 2,2-dimethyl succinic anhydride, butyl succinic anhydride, isobutyl succinic anhydride, hexyl succinic anhydride, octyl succinic anhydride, dodecenyl succinic anhydride, phenyl succinic anhydride, glutaric anhydride, 3-allyl glutaric anhydride, 2,4-dimethyl glutaric anhydride, 2,4-diethyl glutaric anhydride, butyl glutaric anhydride, and hexyl glutaric anhydride. Maleic anhydride, 2-methylmaleic anhydride, 2,3-dimethylmaleic anhydride, butylmaleic anhydride, pentylmaleic anhydride, hexylmaleic anhydride, octylmaleic anhydride, decylmaleic anhydride, dodecylmaleic anhydride, 2,3-dichloromaleic anhydride, phenylmaleic anhydride, 2,3-diphenylmaleic anhydride, itaconic anhydride, citraconic anhydride, phthalic anhydride, 4-methylphthalic anhydride, dimer -acid, 1,2,3,6-tetrahydrophthalic anhydride, 3-methyl-1,2,3,6-tetrahydrophthalic anhydride, 4-methyl-1,2,3,6-tetrahydrophthalic anhydride, 3-methyl-1,2,3,6-tetrahydrophthalic anhydride, 4-methyl-1,2,3,6-tetrahydrophthalic anhydride, methylbutenyl-1,2,3,6-tetrahydrophthalic anhydride, chlorendic anhydride, head acid anhydride, biphenyl dicarboxylic anhydride, non Examples include water hymic acid, endomethylene-1,2,3,6-tetrahydrophthalic anhydride, methyl-3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride, 1-cyclopentene-1,2-dicarboxylic anhydride, methylcyclohexene dicarboxylic anhydride, trimellitic anhydride, 1,8-naphthalenedicarboxylic anhydride, and octahydro-1,3-dioxo-4,5-isobenzofurandicarboxylic anhydride.

In one embodiment, when the binder resin contains an aqueous (meth)acrylic resin and an aqueous polyester resin, the ratio (A:B) of the content (A) of the aqueous (meth)acrylic resin to the content (B) of the aqueous polyester resin is preferably 95:5 to 40:60. The ratio is more preferably 85:15 to 50:50, and even more preferably 80:20 to 60:40.

In one embodiment, the binder resin preferably contains at least one of an aqueous (meth)acrylic resin containing a ring structure and an aqueous polyester resin containing a ring structure, and an aqueous (meth)acrylic resin that does not contain a ring structure.

(Additives)
The overcoat agent of the above embodiment may further contain various additives known in the art. For example, in the production of the overcoat agent, additives such as a wetting agent, an adhesion assistant, a leveling agent, an antifoaming agent, an antistatic agent, a viscosity modifier, a chelating crosslinking agent, a trapping agent, and an antiblocking agent, wax components other than those mentioned above, and a silane coupling agent can be used as necessary.

In one embodiment, the overcoat agent preferably contains a surfactant, and more preferably contains a phosphate ester surfactant. The phosphate ester surfactant may be a polyoxyethylene alkyl ether phosphate ester. In one embodiment, the phosphate ester surfactant may be a mixture of a monoester, a diester, and a trace amount of a triester, as represented by the following structural formula:

In the above structural formula, n is an integer of 1 or more, preferably 1 to 10. The above mixture that can be used as a phosphate ester surfactant is also available as a commercial product. For example, there is a product called "Phosphanol RS-610" manufactured by Toho Chemical Industry Co., Ltd.

In the aqueous overcoat agent of the above embodiment, the content of the phosphate ester surfactant may be preferably 0.05 to 2 mass% based on the total solid content of the overcoat agent. The content may more preferably be 0.1 to 1 mass%, and even more preferably be 0.2 to 0.8 mass%.

In one embodiment, the overcoat agent preferably contains a wax. The wax may be polyethylene, and may be available as a commercially available product. For example, the product name of Chemipearl W500 manufactured by Mitsui Chemicals, Inc. may be mentioned.
In the aqueous overcoat agent of the above embodiment, the wax content may be preferably 0.05 to 2 mass % based on the total solid content of the overcoat agent, more preferably 0.1 to 1 mass %, and even more preferably 0.2 to 0.8 mass %.

(solvent)
The overcoat agent of the above embodiment contains an aqueous solvent. The aqueous solvent contains at least water and may contain a water-soluble organic solvent as necessary.
Examples of organic solvents that can be used include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and n-propyl alcohol; glycols such as ethylene glycol and propylene glycol; and glycol ethers such as butyl cellosolve, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether.
In one embodiment, the weight ratio of water to the water-soluble organic solvent is preferably 90:10 to 60:40.

<2> Packaging Material Laminate One embodiment relates to a packaging material laminate having a sealant substrate, a printed layer provided on at least a part of the surface of the sealant substrate, and a transparent protective layer provided on the printed layer. The transparent protective layer can be formed using the overcoat agent of the embodiment. The sealant substrate may be a substrate having heat sealability, or a substrate not having heat sealability, on which a sealant layer (a substrate having heat sealability) is provided. In one embodiment, the packaging material laminate may be a laminate in which a heat seal layer and a transparent protective layer are laminated at least via a printed layer, and the presence of the heat seal layer makes it suitable for use in the manufacture of packaging bags.

Figures 1 and 2 are schematic cross-sectional views showing examples of the structure of a laminate for packaging materials. As shown in Figure 1, in one embodiment, the laminate for packaging materials has a sealant substrate (a heat-sealable substrate 10), a printed layer 20, and a transparent protective layer 30, in that order. Also, as shown in Figure 2, in one embodiment, the laminate for packaging materials has a sealant substrate (a substrate 50 that does not have heat-sealability, and a heat-sealable layer 40), a printed layer 20, and a transparent protective layer 30, in that order. Although not particularly limited, as shown in Figure 1, the laminate is preferably in a form having a heat-sealable substrate 10, a printed layer 20, and a transparent protective layer 30, in that order.

In the laminate of the above embodiment, the substrate is preferably a plastic substrate. The printing layer is formed by printing ink. The printing ink preferably contains a binder resin, a pigment, a solvent, and, if necessary, additives. The melting point of the heat seal layer is preferably 50 to 180°C.

In one embodiment, the total thickness of the laminate excluding the print layer and the transparent protective layer is preferably 5 to 40 μm, and more preferably 5 to 35 μm. When adjusted to such a thickness, it is possible to design the film thickness to be thinner than that of conventional laminates.

The melting point of the transparent protective layer may be preferably 60 to 220° C. The melting point of the transparent protective layer is higher than the melting point of the heat seal layer, and the difference therebetween is preferably 10 to 170° C.
When the melting point is adjusted to the above range, the heat sealability is good even if the film thickness is thinner than that of conventional laminates, and the occurrence of poor appearance due to heat during heat sealing can be easily suppressed. As a result, it is possible to easily provide a packaging material with high gloss and excellent design. The transparent protective layer having the above preferred melting point can be formed by using the overcoat agent of the above embodiment.

The configuration of the laminate for packaging material of the above embodiment will be described in more detail below.
(Transparent protective layer)
In the laminate for packaging material of the above embodiment, the gloss value of the transparent protective layer (overcoat layer) is preferably 70 or more, and more preferably 80 or more. Here, the gloss value means a gloss value measured under the conditions of an incident angle of 60° and a receiving angle of 60°. The gloss value can be measured, for example, using a Micro-TRI-glossmeter manufactured by BYK-Gardner.
In one embodiment, the melting point of the transparent protective layer is preferably 60 to 220° C., and more preferably 90 to 200° C. In one embodiment, the thickness of the transparent protective layer is preferably 0.5 to 10 μm, and more preferably 1 to 6 μm.

The transparent protective layer is formed by applying the overcoat agent of the above embodiment described above. The overcoat agent can be applied by a known printing method. For example, gravure printing, flexographic printing, and microgravure printing are possible, with gravure printing being preferred.

In the gravure printing method, an overcoat agent is applied to the recesses that form the image areas engraved on the surface of a cylindrical cylinder, and after the overcoat agent on the non-image areas is scraped off with a metal plate called a doctor, the overcoat agent remaining in the recesses of the cylinder is transferred onto the printing film to form a coating layer. The amount of overcoat agent applied can be controlled by the depth of the recesses in the cylinder.
The overcoat agent may be applied to the printed layer multiple times, taking into consideration the film properties such as drying after application, gloss of the coating film, scratch resistance, high-temperature hot water resistance, etc. The application amount and number of applications can be appropriately selected as the form of use of the overcoat agent.

The applied overcoat agent is preferably dried at a temperature of 40 to 80°C. If necessary, the resulting print can be left to stand at room temperature to 40°C for 1 to 10 days to become a print (laminate) with a tough overcoat layer.

(Printing layer)
The print layer can be formed using a printing ink. The printing ink preferably contains, but is not limited to, a urethane resin, a polyamide resin, an acrylic resin, a vinyl chloride-vinyl acetate copolymer resin, a nitrocellulose resin, a chlorinated polypropylene resin, an ethylene-vinyl acetate copolymer resin, a vinyl acetate resin, a polyester resin, an alkyd resin, a rosin resin, a rosin-modified maleic acid resin, a ketone resin, a cyclized rubber, a chlorinated rubber, a butyral, a petroleum resin, or the like as a binder resin.
Among them, a printing ink containing at least one selected from the group consisting of a urethane resin, a polyamide resin, an acrylic resin, a vinyl chloride-vinyl acetate copolymer resin, and a nitrocellulose resin is more preferable. In particular, a printing ink containing a urethane resin is even more preferable. When a printing ink containing a urethane resin is used, excellent adhesion to a film-like plastic substrate can be easily obtained.

The urethane resin can be obtained by known methods, such as those disclosed in JP-A-62-153366, JP-A-62-153367, JP-A-1-236289, JP-A-2-64173, JP-A-2-64174, and JP-A-2-64175. Specifically, first, a polyol and a diisocyanate are reacted in a ratio that results in an excess of isocyanate groups to obtain a prepolymer having terminal isocyanate groups. Next, the obtained prepolymer can be produced by a two-stage method in which a chain extender and/or a reaction terminator are reacted in a suitable solvent, or a one-stage method in which a polyol, a diisocyanate, a chain extender, and/or a reaction terminator are reacted at once in a solvent. Of these methods, the two-stage method is preferred to obtain a uniform urethane resin.

The printing ink may contain additives. Examples of additives include pigment dispersants, leveling agents, defoamers, leveling agents, waxes, trapping agents, plasticizers, infrared absorbers, ultraviolet absorbers, anti-blocking agents, antistatic agents, and flame retardants.

As the pigment contained in the printing ink, any of the C.I. pigments described in the Color Index that can be used in printing inks or paints can be used. Examples include color pigments such as titanium oxide, red iron oxide, Prussian blue, ultramarine blue, carbon black, and graphite, and extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. Furthermore, examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo chelate pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments. The content of these pigments can be 0.5 to 50% by weight based on the total mass of the printing ink.

The solvent used in the printing ink preferably contains a solvent from the viewpoint of wetting and spreading on the substrate and drying properties. The solvent may be the same as the solvent used in the overcoat agent. In one embodiment, known alcohol-based organic solvents, ketone-based organic solvents, ester-based organic solvents, aliphatic hydrocarbon-based organic solvents, and alicyclic hydrocarbon-based organic solvents can be used as the solvent for the printing ink. In one embodiment, taking into consideration the solubility of the urethane resin and the resin used in combination, and drying properties during printing, it is preferable to use a mixture of the above organic solvents to form an organic solvent-based printing ink. Here, "organic solvent-based printing ink" means an ink containing an organic solvent that is not mainly composed of water.

Printing inks can be produced by known methods of dispersing pigments in solvents using resins and solvents. For example, a pigment dispersion is produced by dispersing a pigment in a solvent using a urethane resin, a co-resin, a dispersant, etc., and resins and additives are further blended into the resulting pigment dispersion as necessary. Specific examples of dispersing machines used in the dispersion process include sand mills, gamma mills, and other dispersing machines using bead mills.

(Sealant Base Material)
The sealant substrate is preferably a substrate made of plastic. In one embodiment, the sealant substrate is preferably a plastic substrate having heat-sealing properties. In this manner, when the sealant substrate is a plastic substrate having heat-sealing properties, the substrate itself functions as a heat-sealing layer.
In another embodiment, the sealant substrate is preferably a plastic substrate having a heat seal layer on a substrate having no heat sealability. In this embodiment, when a heat seal layer is provided on a substrate having no heat sealability, the heat seal layer may be provided on a part of the substrate or on the entire substrate.

The melting point of the plastic substrate or heat seal layer, which is a substrate itself having heat sealability, is preferably 50 to 180° C. The melting point is more preferably 60 to 160° C., and even more preferably 70 to 140° C.
The thickness of the sealant substrate is preferably 5 to 40 μm, and more preferably 10 to 35 μm. Here, the thickness of the sealant substrate means the thickness of the substrate when the substrate itself has heat-sealability. In another embodiment, the thickness of the sealant substrate means the sum of the thickness of the substrate not having heat-sealability and the thickness of the heat-seal layer provided on the substrate.

When a substrate that does not have heat sealability is used, the sealant substrate is preferably a substrate (laminate) in which a heat seal layer is laminated onto a substrate that does not have heat sealability, and the substrate is coated by printing or the like, or is melt coated or laminated by other lamination methods. From the viewpoint of reducing the thickness of such a laminate, it is preferable to apply coating or melt coating. The configuration of the laminate as the sealant substrate is arbitrary, but in the laminate for packaging materials, at least the surface opposite to the surface having the printing layer and the overcoat layer should have a laminate structure of the sealant substrate. The heat seal layer may be a single layer or a multilayer.

As mentioned above, when a plastic substrate with heat sealability is used, after applying an overcoat agent to form a transparent protective layer, bags can be easily made without the need for post-processing, which has the advantage of simplifying the manufacturing process of the package.

(When the substrate has heat sealability, and the substrate itself is a heat seal layer)
In the case where the substrate has heat-sealability, the heat-seal layer is made of a heat-sealable resin. The heat-sealable resin may be any resin that can melt and fuse to each other within the above temperature range.
For example, the film or sheet-like substrate is preferably a resin film or sheet-like substrate made of one or more of acid-modified polyolefin resins obtained by modifying polyolefin resins such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-propylene copolymer, methylpentene polymer, polyethylene, and polypropylene with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, and other resins.
The above-mentioned resin film or sheet-like substrate can be used in a single-layer or multi-layer form. In addition, a barrier material against oxygen, water vapor, etc. may be provided on the surface. The barrier material may be, for example, a vapor-deposited film of a metal such as aluminum, silicon oxide, or aluminum oxide, or an inorganic oxide.

(Substrate without heat sealability)
The substrate having no heat sealability is preferably a plastic substrate obtained by stretching the plastic substrate exemplified below. The stretching is preferably uniaxial or biaxial.
Suitable examples of the plastic substrate include polypropylene and other polyolefin substrates, polyethylene terephthalate, polylactic acid and other polyester substrates, polystyrene substrates, polystyrene-based resins such as AS resin and ABS resin, polycarbonate substrates, polyamide substrates, polyvinyl chloride substrates, various substrates such as polyvinylidene chloride, cellophane substrates, paper substrates, and aluminum foil substrates, or film- or sheet-shaped substrates made of composite materials thereof.

The surface of the above substrate may be coated with a metal oxide by vapor deposition and/or polyvinyl alcohol. For example, GL-AE manufactured by Toppan Printing Co., Ltd., in which aluminum oxide is vapor-deposited on the substrate surface, and IB-PET-PXB manufactured by Dai Nippon Printing Co., Ltd., can be used. Furthermore, if necessary, substrates treated with additives such as antistatic agents and ultraviolet protection agents, or substrates whose surfaces have been corona-treated or low-temperature plasma-treated can also be used.

(Plastic substrate having a heat seal layer on a substrate not having heat sealability)
In the configuration example of the plastic substrate having a heat seal layer on a substrate having no heat sealability, the substrate having no heat sealability may be a biaxially oriented substrate (polypropylene (OPP), polyethylene terephthalate (PET), nylon (Ny), polylactic acid (PLA), etc.). A heat seal layer (HS) can be formed on such a substrate to form a plastic substrate. Specific examples of the heat seal agent constituting the heat seal layer include polyethylene, polypropylene, and copolymer resins thereof, as well as copolymer resins of polyethylene and/or polypropylene with vinyl acetate or other monomers. In this case, the heat seal layer can be obtained by applying a heat seal agent to the plastic substrate having a heat seal agent layer.

The "substrate without heat sealability" may be a multi-layer substrate in which multiple types of plastic substrates are laminated. Examples of the multi-layer substrate include PET/aluminum (Al)/HS, PET/NY/HS, NY/PET/HS, PET/AL/NY/HS, and PET/NY/Al/HS. An anchor coating agent and an adhesive may be used to form the multi-layer substrate.

As described above, in a plastic substrate having a heat seal layer, the surface on which the ink-based printing layer is to be printed may be subjected to corona treatment, frame treatment, plasma treatment, or the like. If the surface to be printed has been subjected to the above treatments, this is preferable because it easily improves the adhesion of the ink-based printing layer to the substrate.

The laminate for packaging material of the above embodiment is constructed by printing a printing ink and an overcoat agent in that order on a plastic substrate (which may also serve as a heat seal layer). As the printing method, gravure printing, flexographic printing, screen printing, and other printing methods can be applied.

One embodiment relates to a method for producing a laminate for packaging materials. This method includes a step of applying a water-based printing ink onto a film substrate to form a printing layer, a step of applying an overcoat agent onto the printing ink layer to form an overcoat layer, and a step of applying or melt-coating a heat seal layer onto the surface of the plastic substrate that does not have the printing ink layer, if the plastic substrate does not have heat sealability.

<3> Packaging material The laminate for packaging material of the above embodiment can be suitably used to form packaging materials such as flexible packaging packages and packaging bags. For example, a packaging bag can be formed by cutting the laminate for packaging material to a predetermined size and heat sealing the edges of the heat seal layers together. The heat sealing temperature is preferably 50 to 250°C, more preferably 80 to 180°C. The pressure during heat sealing may be 1 to 5 kg/ ^cm2 , etc.

Figure 3 is a schematic diagram showing an example of the structure of a packaging material (packaging bag), and is a schematic diagram showing an example of a packaging bag B formed using a packaging material laminate A having a sealant substrate 10, a printed layer 20, and a transparent protective layer 30 formed using an overcoat agent. As shown in Figure 3, the sealant substrates 10 of the packaging material laminate A face each other, and the edges of each are heat-sealed (reference symbol 30a).

In producing a packaging bag, one packaging bag laminate may be folded and the edges may be heat sealed, or two or more packaging bag laminates may be heat sealed. The packaging bag may also be one in which all openings are heat sealed after the contents are packaged. This packaging bag can be widely used as a packaging bag for food, medicine, etc. In addition, since the front-printed configuration exhibits excellent resistance to high-temperature hot water, it is also suitable for applications requiring high resistance in the conventional reverse-printed configuration.

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples, and various modifications are possible. In the present invention, the terms "parts" and "%" refer to parts by mass and % by mass unless otherwise noted.

The weight average molecular weight and acid value of the resin described below are values obtained by the following measurement methods.
(Weight average molecular weight)
The weight average molecular weight (Mw) was measured by gel permeation chromatography (GPC) and calculated using polystyrene as a standard substance under the following measurement conditions.
GPC device: Showa Denko Shodex GPC-104
Columns: The following columns were used in series connection:
Showa Denko Shodex LF-404 x 2 Showa Denko Shodex LF-G x 2
Detector: RI (differential refractometer)
Measurement conditions: column temperature 40°C
Eluent: tetrahydrofuran Flow rate: 0.3 mL/min (acid value)
The acid value of a resin is defined as the number of milligrams of potassium hydroxide required to neutralize the acidic groups present in 1 gram of fat or oil, and is a value obtained according to JIS K0070.

<1> Synthesis of binder resin <1-1> Synthesis of polyurethane resin for printing ink [Synthesis Example 1] (Preparation of urethane resin PU1 solution)
150 parts of polyester polyol (PMPA) having a number average molecular weight of 1,000 obtained by reacting adipic acid with 3-methyl-1,5-pentanediol, 50 parts of polypropylene glycol (PPG700) having a number average molecular weight of 700, 103.4 parts of isophorone diisocyanate (IPDI), and 75.8 parts of ethyl acetate (ethyl acetate) were reacted at 80° C. for 4 hours under a nitrogen stream to obtain a resin solution of a terminal isocyanate urethane prepolymer.
Next, the resin solution of the isocyanate-terminated urethane prepolymer previously prepared was gradually added at 40° C. to a solution obtained by mixing 44.6 parts of isophorone diamine (IPDA) and 736.2 parts of a mixed solvent of ethyl acetate/isopropanol (IPA) = 50/50 (mass ratio), to obtain a polyurethane resin solution PU1 (solid content 30%).

<1-2> Synthesis of binder resin for overcoat agent [Synthesis Example 2] (Preparation of aqueous acrylic resin A solution)
57.9 parts of water, 1.8 parts of acrylic acid, 34.0 parts of n-butyl methacrylate, and 6.2 parts of 2-ethylhexyl acrylate were charged into a reactor, gradually heated to 60°C with stirring under a nitrogen stream, and 0.1 parts of ammonium persulfate were added to carry out the reaction. The reaction was carried out for 120 minutes or more, and after the viscosity was confirmed, the reaction was stopped and the mixture was removed from the reactor to obtain a solution of aqueous acrylic resin A.
The glass transition temperature of the aqueous acrylic resin A was 5° C. as a result of DSC measurement. The acid value was 33.0 mg KOH/g. The weight average molecular weight was 1,530,000. The aqueous acrylic resin A is an emulsion type resin and does not have an aromatic ring structure in the resin.

[Synthesis Example 3] (Preparation of a solution of aqueous acrylic resin B)
57.7 parts of water, 0.3 parts of acrylic acid, 17.6 parts of styrene, 18.0 parts of n-butyl methacrylate, and 6.1 parts of 2-ethylhexyl acrylate were charged into a reactor, and the remainder was charged into a dropping can. While stirring under a nitrogen stream, the reactor was gradually heated to 42°C, and 0.1 parts of ammonium persulfate and 0.1 parts of sodium metabisulfite were added to start the reaction. While gradually heating to 48°C, the dropper residue and the residues of ammonium persulfate and sodium metabisulfite were simultaneously dropped over 80 minutes, and the reaction was carried out at 60°C for more than 1 hour. After checking the viscosity, 0.1 parts of 28% ammonia water was added at a temperature of 40°C or less to obtain a solution of aqueous acrylic resin B.
The glass transition temperature of the aqueous acrylic resin B was 27° C. as a result of DSC measurement. The acid value was 6.0 mg KOH/g. The weight average molecular weight was 100,000. The aqueous acrylic resin B is an emulsion type resin, and contains 24.4% by mass of an aromatic ring structure based on the total mass of the resin.

[Synthesis Example 4] (Preparation of aqueous acrylic resin C solution)
57.8 parts of water, 2.1 parts of acrylic acid, 14.4 parts of methyl methacrylate, 4.4 parts of 1,4-cyclohexanedimethanol monoacrylate, 12.6 parts of n-butyl methacrylate, and a part of 8.4 parts of 2-ethylhexyl acrylate were charged in a reaction vessel, and the remainder was charged in a dropping vessel. While stirring under a nitrogen stream, the reaction vessel was gradually heated to 42°C, and 0.1 parts of ammonium persulfate and 0.1 parts of sodium metabisulfite were added to start the reaction. While gradually heating to 48°C, the drop vessel residue and the residues of ammonium persulfate and sodium metabisulfite were simultaneously dropped over 80 minutes, and the reaction was carried out at 60°C for more than 1 hour. After checking the viscosity, 0.1 parts of 28% ammonia water was added at a temperature of 40°C or less to obtain a solution of aqueous acrylic resin C.
The glass transition temperature of the aqueous acrylic resin C was 20° C. as a result of DSC measurement. The acid value was 39 mg KOH/g. The weight average molecular weight was 150,000. The aqueous acrylic resin C is an emulsion type resin, and contains 6.2% by mass of an alicyclic structure based on the total mass of the resin.

[Synthesis Example 5] (Preparation of a solution of aqueous acrylic resin D)
57.7 parts of water, 13.0 parts of acrylic acid, 16.8 parts of styrene, and a portion of 12.2 parts of n-butyl methacrylate were charged into a reactor, and the remainder was charged into a dropping can. The reactor was gradually heated to 42°C while stirring under a nitrogen stream, and a portion of 0.1 parts of ammonium persulfate and 0.1 parts of sodium metabisulfite was added to start the reaction. The dropping can residue and the residues of ammonium persulfate and sodium metabisulfite were simultaneously dropped over 80 minutes while gradually heating to 48°C, and the reaction was carried out at 60°C for 1 hour or more. After checking the viscosity, 0.1 parts of 28% ammonia water was added at a temperature of 40°C or less to obtain a solution of aqueous acrylic resin D.
The glass transition temperature of the aqueous acrylic resin D was 73° C. as a result of DSC measurement. The acid value was 240 mg KOH/g. The weight average molecular weight was 250,000. The aqueous acrylic resin D is an emulsion type resin, and contains 29.3% by mass of an aromatic ring structure based on the total mass of the resin.

[Synthesis Example 6] (Preparation of a solution of aqueous acrylic resin E)
57.7 parts of water, 3.5 parts of methacrylic acid, 23.8 parts of methyl methacrylate, and a part of 14.7 parts of styrene were charged into a reactor, and the remainder was charged into a dripping can. The reactor was gradually heated to 42°C while stirring under a nitrogen stream, and 0.1 parts of ammonium persulfate and 0.1 parts of sodium metabisulfite were added to start the reaction. While gradually heating to 48°C, the dripping can residue and the residues of ammonium persulfate and sodium metabisulfite were simultaneously dripped over 80 minutes, and the reaction was carried out at 60°C for more than 1 hour. After checking the viscosity, 0.1 parts of 28% ammonia water was added at 40°C or less to obtain a solution of aqueous acrylic resin E.
The glass transition temperature of the aqueous acrylic resin E was 108° C. as a result of DSC measurement. The acid value was 54 mg KOH/g. The weight average molecular weight was 250,000. The aqueous acrylic resin E is an emulsion type resin, and contains 25.9% by mass of an aromatic ring structure based on the total mass of the resin.

[Synthesis Example 7] (Preparation of aqueous acrylic resin F solution)
57.7 parts of water, 3.0 parts of acrylic acid, 33.7 parts of styrene, 2.6 parts of n-butyl methacrylate, and 2.7 parts of 2-ethylhexyl acrylate were charged into a reactor, and the remainder was charged into a dropping tank. While stirring under a nitrogen stream, the reactor was gradually heated to 42°C, and 0.1 parts of ammonium persulfate and 0.1 parts of sodium metabisulfite were added to start the reaction. While gradually heating to 48°C, the drop tank residue and the residues of ammonium persulfate and sodium metabisulfite were simultaneously dropped over 80 minutes, and the reaction was carried out at 60°C for more than 1 hour. After checking the viscosity, 0.1 parts of 28% ammonia water was added at a temperature of 40°C or less to obtain a solution of aqueous acrylic resin F.
The glass transition temperature of the aqueous acrylic resin F was 73° C. as a result of DSC measurement. The acid value was 54 mg KOH/g. The weight average molecular weight was 200,000. The acrylic resin F is an emulsion type resin, and contains 56.3% by mass of an aromatic ring structure based on the total mass of the resin.

[Synthesis Example 8] (Preparation of a solution of aqueous polyester resin A)
31.3 parts of terephthalic acid, 31.3 parts of isophthalic acid, 14.0 parts of ethylene glycol, and 23.4 parts of neopentyl glycol were charged into a reactor, and while stirring under a nitrogen stream, the mixture was gradually heated to 160 to 240°C to carry out an esterification reaction. The reaction was carried out at 240°C for one hour or more, and after the acid value reached 15 or less, the pressure in the reactor was gradually reduced to 1 to 2 Torr. After checking the viscosity, the reaction was stopped and the mixture was removed from the reactor, and a solution of aqueous polyester resin A was obtained.
The glass transition temperature of the aqueous polyester resin A was 53° C. as a result of DSC measurement. The acid value was 0.2 mg KOH/g. The weight average molecular weight was 50,000. The polyester resin A was an emulsion type resin, and contained 36.1% by mass of an aromatic ring structure based on the total mass of the resin.

The compositions of the binder resin solutions for overcoat prepared above are shown in Table 1.

<2> Production of printing ink [Production Example 1] (Production of printing ink R1)
As a binder resin, 30 parts of urethane resin solution PU1, 5 parts of vinyl chloride-vinyl acetate copolymer resin, 1 part of chlorinated polypropylene resin, 2 parts of polyethylene wax, 10 parts of indigo pigment, and 52 parts of a solution of MEK/NPAC/IPA = 40/40/20 (mass ratio) were mixed and dispersed in a bead mill for 15 minutes to obtain printing ink R1.

[Production Examples 2 and 3] (Production of Printing Inks R2 and R3)
Printing inks R2 and R3 were obtained in the same manner as in Production Example 1, except that the raw materials and blending ratios were changed to those shown in Table 2.

Details of the raw materials listed in Table 2 are as follows.
(Binder resin)
Urethane resin solution PU1 (prepared in Synthesis Example 1, solid content 30% by mass)
Vinyl chloride-vinyl acetate copolymer resin (Nissin Chemical Industry Co., Ltd., Solvine TAO, solid content 30% by mass, ethyl acetate solution)
Rosin maleic acid resin: rosin modified maleic acid resin. Arakawa Chemical Industry Co., Ltd., Malkid No. 5, solid content 30 mass%, ethyl acetate solution, softening point 145°C, hydroxyl value 0 mgKOH/g
Polyamide resin: A polyamide resin containing 50% by mass or more of structural units derived from dimer acid made from oleic acid and linoleic acid as raw materials, and having an amine value of 3.5 mgKOH/g. Weight average molecular weight: 6,000, solid content: 30% by mass, IPA solution.
Cellulose resin: Nitrocellulose. Solid content 30% by mass, ethyl acetate/IPA solution, nitrogen content 11.5-12.2%, polymerization degree 35-45, hydroxyl value 175 mgKOH/g
Chlorinated polypropylene resin (manufactured by Nippon Paper Industries Co., Ltd., 370M, chlorine content 30%, solid content 50% by mass)
(wax)
Polyethylene wax (Mitsui Chemicals, Hiwax 320P, average particle size 2.5 μm)
(Pigment)
Indigo pigment (C.I. Pigment Blue 15:4)
Titanium oxide (Teika Co., Ltd., Titanix JR-808)
(Crosslinking Agent)
Chelate crosslinking agent (Matsumoto Fine Chemical Co., Ltd., Orgatics TC-750)
(solvent)
A solution of methyl ethyl ketone (MEK)/n-propyl acetate (NPAC)/isopropyl alcohol (IPA) = 40/40/20 (mass ratio)

<3> Preparation of overcoat agent and production of laminate (printed matter) for packaging material [Example 1]
(Preparation of overcoat agent S1)
65.8 parts of a solution of aqueous acrylic resin A (solid content 42% by mass), 28.0 parts of a solution of aqueous acrylic resin B (solid content 42% by mass), 0.5 parts of a phosphoric acid ester (Phosphanol RD-720 manufactured by Toho Chemical Industry Co., Ltd., solid content 96%), and 0.5 parts of a wax (Chemipearl WF640 manufactured by Mitsui Chemicals, Inc.) as other raw materials, and 5.2 parts of water were mixed and stirred for 30 minutes with a disper to obtain an overcoat agent S1 with a solid content of 40%.

(Production of printed matter using printing ink R2 and overcoat agent S1)
The printing ink R2 and overcoat agent S1 prepared above were each diluted with ethyl acetate to a viscosity of 15 seconds at 25° C. in a Zahn cup #3 (manufactured by Rigo Co., Ltd.).
The diluted printing ink R2 was applied to a 30 μm thick heat-sealable polypropylene (HSOPP) film using a gravure printing machine equipped with a gravure plate having a plate depth of 35 μm at a printing speed of 40 m/min and a dryer temperature of 60° C. to obtain a printed film.
Next, the diluted overcoat agent S1 was applied to the surface of the printed film prepared above having the printed layer using a gravure printing machine equipped with a gravure plate with a plate depth of 35 μm, at a printing speed of 40 m/min and a dryer temperature of 60° C., to obtain a printed matter having a configuration of plastic substrate/printed layer/transparent protective layer.

[Examples 2 to 19]
(Preparation of overcoat agents S2 to S19, SS1 to SS4)
Overcoat agents S2 to S19 and SS1 to SS4 were obtained in the same manner as in Example 1, except that the raw materials and compounding ratios were changed as shown in Table 3.
(Production of printed matter using various printing inks and overcoats)
Using the printing inks and overcoat agents prepared above, printed matter according to Examples 2 to 19 was produced in the same manner as in Example 1, in accordance with the combinations shown in Table 3.

[Comparative Examples 1 to 4]
(Preparation of overcoat agents SS1 to SS4)
Overcoat agents SS1 to SS4 were obtained in the same manner as in Example 1, except that the raw materials and compounding ratios were changed to those shown in Table 4.
(Production of printed matter using various printing inks and overcoats)
Using the printing inks and overcoat agents prepared above, printed matter according to Comparative Examples 1 to 4 was produced in the same manner as in Example 1, in accordance with the combinations shown in Table 4.

<4> Evaluation of Characteristics The prints produced using the overcoat agents obtained in the above Examples and Comparative Examples were evaluated as described below. The evaluation results are shown in Tables 3 and 4, respectively.

<Gloss>
The gloss value was measured from the transparent protective layer side of the printed matter produced in the above Examples and Comparative Examples using a Micro-TRI-glossmeter manufactured by BYK-Gardner, Inc., at an incident angle of 60° and an acceptance angle of 60°. The evaluation criteria are as follows. Evaluations A and B are in the range where there is no problem in practical use.
(Evaluation Criteria)
A (excellent): Gloss value is 80 or more.
B (Acceptable): Gloss value is 70 or more and less than 80.
C (unacceptable): Gloss value is less than 70.

<Gloss of heat-sealed area>
The printed matter produced in the above examples and comparative examples was cut into pieces of 3 cm x 13 cm, and the glossy side of an aluminum foil (thickness 30 μm) cut to the same size was placed on the printed side of the printed matter. The aluminum foil was pressed with a pressure of 2 x 9.8 N/ ^cm2 at 150°C for 1 second using a heat sealer manufactured by Sentinel, and the gloss value was measured at an incidence angle of 60° and a receiving angle of 60° from the printed layer or transparent protective layer when the aluminum foil was peeled off using a Micro-TRI-glossmeter manufactured by BYK-Gardner. The evaluation criteria are as follows. Evaluations A and B are in the range where there is no problem in practical use.
(Evaluation Criteria)
A (excellent): Gloss value is 60 or more.
B (Acceptable): Gloss value is 40 or more and less than 60.
C (unacceptable): Gloss value is less than 40.

<Heat resistance>
The printed matter produced in the above examples and comparative examples was cut into a size of 3 cm x 13 cm, and the glossy side of an aluminum foil (thickness 30 μm) cut to the same size was placed on the printed side of the printed matter. The aluminum foil was pressed with a pressure of 2 x 9.8 N/ ^cm2 at 150°C for 1 second using a Sentinel heat sealer, and the peeling of the printed layer or transparent protective layer when the aluminum foil was peeled off was visually judged. The evaluation criteria are as follows. Evaluations A and B are in the range where there is no problem in practical use.
(Evaluation Criteria)
A (Excellent): The printed layer did not peel off at all at a seal bar temperature of 150° C., and there was no peel resistance between the printed layer and the aluminum foil.
B (Fair): The printed layer does not peel off at all at a seal bar temperature of 150°C, but there is peel resistance between the printed layer and the aluminum foil.
C (unacceptable): A part of the printed layer peels off at a seal bar temperature of 150°C.

(Kneading resistance)
The printed matter produced in the above-mentioned Examples and Comparative Examples was kneaded 30 times with both hands and evaluated according to the following evaluation criteria. Evaluations A and B are in the range where there is no problem in practical use. The measurement conditions were a test piece of 100 mm square.
(Evaluation Criteria)
A (Excellent): No peeling or lifting of the ink film. B (Fair): Some peeling or lifting of the ink film is observed, but no peeling. C (Unacceptable): Some peeling of the ink film is observed.

(Abrasion resistance)
The coating strength of each of the prints produced in the above Examples and Comparative Examples was measured using a Gakushin-type friction fastness tester manufactured by Tester Sangyo Co., Ltd. The evaluation criteria are as follows. Evaluations A and B are in the range where there are no practical problems. The measurement conditions were: test piece 20 mm wide, load 500 g, 100 reciprocations, against Kanakin No. 3.
(Evaluation Criteria)
A (Excellent): No peeling of the ink film B (Fair): The area of the ink film that has peeled off is 10% or more but less than 30% C (Fail): The entire ink film has peeled off

<Reference Example 1: Evaluation of only surface-printed prints of printing ink>
Each of the printing inks R2 was diluted with a mixed solvent of ethyl acetate/IPA (mass ratio 70/30) so that the ink would last for 15 seconds at 25° C. in a Zahn cup #3 (manufactured by Rigo Co., Ltd.).
The diluted printing ink R3 was applied to a 30 μm thick OPP film using a gravure printing machine equipped with a gravure plate with a plate depth of 35 μm at a printing speed of 40 m/min and a dryer temperature of 60° C., to obtain a printed matter A1 with a surface print configuration.
The print A1 having the surface printing structure was subjected to various evaluations in the same manner as described above. The results were gloss: C, gloss of the heat-sealed portion: C, heat resistance: A, kneading resistance: B, and abrasion resistance: B.

Reference Example 2: Evaluation of Laminated Body
Each of the printing inks R2 was diluted with a mixed solvent of ethyl acetate/IPA (mass ratio 70/30) so that the ink would last for 15 seconds at 25° C. in a Zahn cup #3 (manufactured by Rigo Co., Ltd.).
The diluted printing ink R2 was applied to a 30 μm thick OPP film using a gravure printing machine equipped with a gravure plate with a plate depth of 35 μm at a printing speed of 40 m/min and a dryer temperature of 60° C., to obtain a printed matter A2.
Next, using a dry laminator, a dry laminating adhesive (TM-340V/CAT-29B manufactured by Toyo-Morton) was applied onto the printed layer of printed matter A2, and then it was laminated with CPP (unstretched polypropylene film, thickness 25 μm) at a line speed of 40 m/min, to obtain a laminated body B1 laminated in the order of OPP substrate/printed layer/adhesive layer/CPP substrate.
The laminate B1 was evaluated in the same manner as above. The results were gloss: B, adhesion: A, heat resistance: A, blocking resistance: A, kneading resistance: A, and abrasion resistance: A. The gloss was evaluated from the OPP substrate side.

The above evaluation results show that by using an overcoat agent according to an embodiment of the present invention, the gloss of the printed layer can be improved to the same level as a laminate laminated with a film, and good adhesion and heat resistance can be achieved in the surface printing configuration of flexible packaging. The obtained printed matter was also good in terms of odor.

10: Substrate having heat sealability 20: Printed layer 30: Transparent protective layer 30a: Heat seal portion
40 Substrate not having heat sealability 50 Heat seal layer A Laminate for packaging material B Packaging material (packaging bag)

Claims (10)

A laminate for packaging materials, comprising a sealant substrate, a printed layer provided on at least a portion of a surface of the sealant substrate, and a transparent protective layer formed on the printed layer by using an aqueous overcoat agent,
The aqueous overcoat agent contains at least a binder resin,
The binder resin comprises an aqueous (meth)acrylic resin,
a content of the aqueous (meth)acrylic resin is 40% by mass or more, and a ratio of a ring structure contained in the binder resin is 0.5 to 30% by mass, based on the total mass of solids in the binder resin. 2. The laminate for packaging materials according to claim 1, wherein the aqueous (meth)acrylic resin has an acid value of 150 mg KOH/g or less. 3. The laminate for packaging materials according to claim 1, wherein the binder resin has a glass transition temperature (Tg) of 100° C. or lower. The laminate for packaging materials according to any one of claims 1 to 3, wherein the binder resin further contains a polyester resin, and a ratio of a content of the aqueous (meth) acrylic resin to a content of the polyester resin is 95:5 to 40:60. The laminate for packaging materials according to any one of claims 1 to 4, wherein the binder resin comprises at least one of an aqueous (meth)acrylic resin containing a ring structure and an aqueous polyester resin containing a ring structure, and an aqueous (meth) acrylic resin not containing a ring structure. The laminate for packaging materials according to any one of claims 1 to 5, further comprising a phosphate ester surfactant. 7. The laminate for packaging materials according to claim 1, wherein the aqueous overcoat agent does not contain a synthetic wax in which a polyolefin wax is coated with a fluororesin. The laminate for packaging materials according to any one of claims 1 to 7 , wherein the gloss value (60°) of the surface on the transparent protective layer side is 60 or more. 3. A packaging material using the laminate for packaging materials according to claim 1 or 2 , comprising a sealant base material, a printed layer provided on at least a portion of the surface of the sealant base material, and a transparent protective layer formed on the printed layer using an aqueous overcoat agent, the packaging material having a joint formed by heat sealing the sealant base material. An aqueous overcoat agent for forming a transparent protective layer on a printed layer provided on at least a portion of a surface of a sealant substrate, the aqueous overcoat agent including at least a binder resin ,
The binder resin comprises an aqueous (meth)acrylic resin ,
the content of the aqueous (meth)acrylic resin is 40% by mass or more based on the total mass of the solid content in the binder resin, and the ratio of a ring structure contained in the binder resin is 0.5 to 30% by mass ,
A water-based overcoat agent that does not contain synthetic wax and is made by coating a polyolefin wax with a fluororesin .

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