JP2022169882A - Packaging material having flexographic printing layer, and method for producing packaging material - Google Patents

Abstract

To provide a packaging material having a flexographic printing layer which is excellent in laminate strength in extrusion lamination, heat seal strength and packaging material appearance.SOLUTION: A packaging material sequentially has a base material 1, a flexographic printing layer and a base material 2, where the flexographic printing layer satisfies the following (1) and (2). (1) The flexographic printing layer contains a nitrocellulose resin and an urethane resin in a mass ratio of 99:1 to 40:60, and a complex crosslinking agent. (2) The urethane resin contains an urethane resin (A) having a weight average molecular weight of 20,000 or more and 80,000 or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a packaging material having a flexographic printed layer and a method for manufacturing the packaging material.

In general, packaging materials are formed by providing a printed layer on a substrate, and bonding an adhesive layer and a sealant on the printed layer. Printing on plastic film, which is the base material that makes up packaging materials, is broadly divided into gravure printing and flexographic printing. The former is intaglio printing and the latter is letterpress printing, but in general, the amount of ink transferred from the plate to the film. is known to be less in the letterpress printing method. Because of this feature, it is necessary to set the pigment concentration in the flexo ink higher than that in the gravure ink, so a binder resin having good pigment dispersibility is selected. Urethane resins, nitrocellulose resins, polyamide resins, acrylic resins, and the like are often used as the binder resin, but nitrocellulose resins, which are excellent in dispersing pigments, are widely selected for the reasons described above.

Currently, the general method of creating packaging materials is the lamination method, which includes the extrusion lamination method and the dry lamination method. is used a lot. In such a packaging material, an anchor layer, a melt-adhesive polyolefin resin, and a sealant base material are laminated on the printed layer. Urethane resins are generally used because they can be applied to a wide range of plastic substrates in terms of adhesion to substrates. In particular, when a urethane resin chain-extended with a polyamine is used as a binder resin, it is known that adhesion to a substrate and lamination strength in extrusion lamination are improved (Patent Documents 1 and 2).

As shown in the above patent document, flexographic inks used for packaging materials manufactured by extrusion lamination may use a combination of nitrocellulose resin and urethane resin. When used in combination with a resin, there is a problem that the laminate strength also decreases.

Therefore, in terms of industrial use, a packaging material that uses flexographic ink using both a nitrocellulose resin and a urethane resin and has a good appearance and high lamination strength has not yet been achieved.

JP 2014-012753 A Japanese Patent Publication No. 2011-503334

An object of the present invention is to provide a packaging material having a flexographic print layer, which is excellent in lamination strength in extrusion lamination, heat seal strength, and appearance of the packaging material.

In view of the above problems, the present inventors have made intensive studies, and as a result, have found that the problems can be solved by using the packaging material described below, and have completed the present invention.

That is, the present invention relates to a packaging material having a substrate 1, a flexographic print layer, and a substrate 2 in sequence, wherein the flexographic print layer satisfies (1) and (2) below.
(1) The flexographic printing layer contains a nitrocellulose resin and a urethane resin in a mass ratio of 99:1 to 40:60, and a complex cross-linking agent.
(2) The urethane resin contains a urethane resin (A) having a weight average molecular weight of 20,000 or more and 80,000 or less.

The present invention also relates to the packaging material described above, further comprising a meltable polyolefin resin layer between the flexographic printing layer and the substrate 2 .

The present invention also provides the above packaging, wherein the surface of the flexographic printing layer opposite to the substrate 1 has at least one anchor layer selected from the group consisting of an imine anchor layer, a butadiene anchor layer and an isocyanate anchor layer. Regarding materials.

The present invention also relates to the above packaging material, wherein the urethane resin contains structural units derived from polyether.

The present invention also relates to the packaging material, wherein the urethane resin further contains a urethane resin (B) having a weight average molecular weight of 5000 or more and less than 20000.

The present invention also relates to the above packaging material, wherein the complex cross-linking agent is a titanium complex and/or a zirconium complex.

The present invention also provides a method for producing a packaging material having, in order, a base material 1, a flexographic printing layer, an anchor layer, a meltable polyolefin resin layer and a base material 2,
A step of flexographically printing an organic solvent-based flexographic ink on the base material 1 to form the flexographically printed layer,
The organic solvent-based flexographic ink contains a nitrocellulose resin and a urethane resin in a mass ratio of 99:1 to 40:60, and a complex cross-linking agent,
The present invention relates to a method for producing a packaging material, wherein the urethane resin contains a urethane resin (A) having a weight average molecular weight of 20,000 or more and 80,000 or less.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a packaging material having a flexographically printed layer which is excellent in lamination strength in extrusion lamination, heat seal strength, and appearance of the packaging material.

Embodiments of the present invention will be described in detail below with reference to examples. Not limited.

In the following description, organic solvent-based flexo ink may be abbreviated as "ink" or "flexo ink", but they have the same meaning. A printed layer formed with an organic solvent-based flexo ink is sometimes referred to as an "ink film", but it has the same meaning.

The packaging material of the present invention has substrate 1, flexographic printing layer and substrate 2 in sequence. Preferably, it has a meltable polyolefin resin layer and/or an anchor layer between the flexographic printing layer and the substrate 2 . The flexographic printing layer is formed by flexographic printing with organic solvent-based flexographic ink. The flexographic ink contains a nitrocellulose resin, a urethane resin, and a complex cross-linking agent.

The flexographic printing layer satisfies (1) and (2) below.
(1) The flexographic printing layer contains a nitrocellulose resin and a urethane resin in a mass ratio of 99:1 to 40:60, and a complex cross-linking agent.
(2) The urethane resin contains a urethane resin (A) having a weight average molecular weight of 20,000 or more and 80,000 or less.
If the mass ratio of the nitrocellulose resin and the urethane resin is within the above range, the laminate strength and other characteristics of the packaging material are improved, and the urethane resin contains the urethane resin (A) having a weight average molecular weight of 20,000 or more and 80,000 or less. , excellent heat seal strength.

A urethane resin refers to a resin having a urethane bond, may have a urea bond, and contains the urethane resin (A). The urethane resin functions as a binder resin. The urethane resin further contains a urethane resin (B), which will be described later, to improve extrusion lamination strength.

The binder resin containing the above urethane resin and nitrocellulose resin is desirably contained in a total amount of 10 to 25% by mass in the total amount of the ink. The total weight of the binder resin preferably contains 50 to 100% by weight of urethane resin and nitrocellulose resin in total, more preferably 70 to 100% by weight, more preferably 85 to 100% by weight, and 90 to 100% by weight. % by mass is particularly preferred.

The binder resin contains nitrocellulose resin and urethane resin at a mass ratio of 99:1 to 40:60, preferably 90:10 to 42:58, more preferably 80:20 to 45:55. At this mass ratio and combination, the laminate strength, heat seal strength, and appearance of the packaging material are excellent. The mass ratio is the same as the mass ratio of the nitrocellulose resin and the urethane resin in the flexographic printing layer.

<Urethane resin (A)>
The urethane resin (A) is a polyurethane resin having a urethane bond, and preferably has a urea bond in addition to the urethane bond ((poly)urethane urea resin). The urethane resin (A) may have a weight average molecular weight of 20,000 or more and 80,000 or less, preferably 30,000 or more and 70,000 or less, and more preferably 35,000 or more and 65,000 or less. The amine value of the urethane resin (A) is preferably 0.5 mgKOH/g or less, more preferably 0.3 mgKOH/g or less. It is also preferred if it does not have an amine value. This is because the appearance of the packaging material is excellent.

The structure of the urethane resin is not particularly limited, and it is appropriately produced by a known method. Preferred but not limited to these. Moreover, from the viewpoint of combined use with nitrocellulose resin, it is preferable that the terminal groups of the urethane resin are hydroxyl groups and/or alkyl groups. Examples of the method for producing the urethane resin include the method described in JP-A-2017-19991.

(polyol)
Suitable examples of polyols include polyester polyols, polyether polyols, polylactone polyols, polycarbonate polyols, polyolefin polyols, castor oil polyols, hydrogenated castor oil polyols, dimer diols, and hydrogenated dimer diols. More preferred are polyether polyols and/or polyester polyols. It is even more preferred to include a polyether polyol.

Examples of polyether polyols include polypropylene glycol, polyethylene glycol, polytetramethylene glycol, polytrimethylene glycol, and polyether polyols which are copolymers selected from these. The number average molecular weight of the polyether polyol is preferably 200-10,000, more preferably 200-7,000. The number-average molecular weight is calculated from the hydroxyl value with hydroxyl groups at the ends, and is determined by (Equation 1).
(Formula 1) Number average molecular weight of polyol = 1000 × 56.1 × valence of hydroxyl group / hydroxyl value

Examples of polyester polyols include condensates obtained by an esterification reaction between polybasic acids and diols.
The polybasic acid is preferably a dibasic acid, and examples of the dibasic acid include adipic acid, phthalic anhydride, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, and pimeline. acid, azelaic acid, sebacic acid, suberic acid, glutaric acid, 1,4-cyclohexyldicarboxylic acid, dimer acid, hydrogenated dimer acid and the like.
Diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,6-hexanediol and 1,8-octanediol. , 1,9-nonanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 3,3,5-trimethylpentanediol, 2,4-diethyl- 1,5-pentanediol, 1,12-octadecanediol, 1,2-alkanediol, 1,3-alkanediol, 1-monoglyceride, 2-monoglyceride, 1-monoglycerol ether, 2-monoglycerol ether, dimer diol , hydrogenated dimer diol and the like.

The diol is preferably a diol having a branched structure. A branched structure means a diol having an alkyl side chain in which at least one hydrogen atom of an alkylene group contained in the diol is substituted with an alkyl group. Examples thereof include propylene glycol, 1,3-butanediol, 2-methyl -1,3-propanediol, neopentyl glycol, 1,4-pentanediol, 3-methyl-1,5-pentanediol, 2,5-hexanediol, 2-methyl-1,4-pentanediol, 2, 4-diethyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl-1,8-octanediol, 2,2,4-trimethyl-1,3-pentane Diol, and 2,2,4-trimethyl-1,6-hexanediol are preferred. These are particularly preferred because they improve the solubility in organic solvents. A diol having a branched structure and a diol not having a branched structure may be used in combination.
These polyester polyols can be used alone or in combination of two or more. As the dibasic acid, sebacic acid and adipic acid are particularly preferred. A polyol having 3 or more hydroxyl groups and a polyvalent carboxylic acid having 3 or more carboxyl groups can also be used in combination.

The polyester polyol preferably has a number average molecular weight of 200 to 10,000, more preferably 200 to 7,000. The number average molecular weight can be determined by the above (Formula 1).

(polyisocyanate)
Examples of the polyisocyanate include various known aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates that are generally used in the production of urethane resins. These may be trimers to form an isocyanurate ring structure.
Aromatic diisocyanates include 1,5-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 4,4′-diphenyldimethylmethane diisocyanate, 4,4′-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyl diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate and the like.
Aliphatic diisocyanates include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and lysine diisocyanate.
Alicyclic diisocyanates include cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, and norbornane diisocyanate. , m-tetramethylxylylene diisocyanate, hydrogenated 4,4-diphenylmethane diisocyanate, and dimer diisocyanate obtained by converting the carboxyl group of dimer acid to an isocyanate group.
Among them, at least one selected from trimers of 4,4'-diphenylmethane diisocyanate (MDI), tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, bis(isocyanatomethyl)cyclohexane, hexamethylene diisocyanate, and hexamethylene diisocyanate. be. These polyisocyanates can be used alone or in combination of two or more.

(polyamine)
The polyamine is not particularly limited, and a diamine-based or polyfunctional amine-based polyamine can be used. In addition, 2-hydroxyethylethylenediamine, 2-hydroxyethylpropyldiamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypyro Polyamines having hydroxyl groups such as pyrethylenediamine, di-2-hydroxypyropyrethylenediamine, and di-2-hydroxypropylethylenediamine may also be used.
Polyamines having a molecular weight of 500 or less are preferred, and ethylenediamine, propylenediamine, hexamethylenediamine, pentamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, p-phenylenediamine and the like are preferably used.
These polyamines may be used singly or in combination of two or more.

(Regarding terminal groups of urethane resin)
The terminal groups in the urethane resin are, for example, if the structure of the urethane resin is a linear structure, both ends of the linear structure are called terminal groups, and if the structure of the urethane resin is a branched structure, the ends of the branches are also included. The terminal portion is also called a terminal group.
Although the terminal group is not particularly limited, the terminal group is preferably an alkyl group and/or a hydroxyl group. When the urethane resin has a hydroxyl group, the hydroxyl value of the urethane resin is preferably 0.1 to 35 mgKOH/g. , 0.5 to 20 mg KOH/g. When it has an alkyl group, it preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 5 carbon atoms. Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group and hexyl group.

As one embodiment, in order to introduce a hydroxyl group and an alkyl group at the terminal of a urethane resin, a polyol is reacted with a polyisocyanate to obtain a urethane prepolymer having a terminal isocyanate group. and using a polymerization terminator to introduce a terminal structure derived from the polymerization terminator.
When it is desired to introduce an alkyl group to the isocyanate end after the chain extension reaction, it is preferable to use a monoalcohol as a polymerization terminator. preferred. In addition, when it has multiple carbon atoms and structural isomers exist, those structural isomers are also included.
In order to introduce a hydroxyl group to the terminal of the urethane resin, it is preferable to use a diol or an amino alcohol as a polymerization terminator. Preferred examples include butanediol, and preferred aminoalcohols include 2-ethanolamine, 4-butanolamine, and 3-propanolamine, and aminoalcohols having 1 to 8 carbon atoms are preferred. In addition, when it has multiple carbon atoms and structural isomers exist, those structural isomers are also included.
In the case of reacting the polyol with the polyisocyanate, a method of obtaining an excess hydroxyl value of the polyol to obtain a urethane resin having terminal hydroxyl groups is also suitable.

<Urethane resin (B)>
The urethane resin (B) improves lamination strength and heat seal strength when used in combination with the urethane resin (A). The weight average molecular weight of the urethane resin (B) is 5,000 or more and less than 20,000. It is more preferably 10,000 or more and less than 20,000.
The amine value is preferably 0.5 mgKOH/g or less, more preferably 0.1 mgKOH/g or less. It is also preferred if it does not have an amine value. This is because the appearance of the packaging material is excellent.
When the urethane resin (A) and the urethane resin (B) are used together, the mass ratio may be 90:10 to 10:90, preferably 80:20 to 20:80, and 70:30 to 30. :70 is more preferred.
In order to obtain the urethane resin (B), the raw materials and production method used in the case of the urethane resin (A) can be used in the same manner.
The state in which the urethane resin (A) and the urethane resin (B) are used in combination means that the molecular weight distribution has peaks between 5,000 and less than 20,000 and between 20,000 and 80,000. . It is not excluded that the urethane resin (A) includes those having a molecular weight of less than 20,000 and that the urethane resin (B) includes those having a molecular weight of 20,000 or more.

(Complex cross-linking agent)
The complex cross-linking agent is preferably a titanium complex or a zirconium complex, and preferably has at least one selected from an alkoxy group, an alkyl group, an amino group, an acetyl group, and a phosphoric acid group.
The alkoxy group in the titanium complex preferably has 1 to 20 carbon atoms, more preferably 2 to 10 carbon atoms. Examples with alkoxy groups are titanium tetraisopropoxide, titanium tetra-normal butoxide, titanium butoxide dimer, titanium tetra-2-ethylhexoxide, titanium tetramethoxide, tetra(octadecyloxy)titanium, bis(2-ethylhexyl). oxy)bis(2-ethyl-3-oxohexyloxy)titanium, and the like. An alkoxy group is also preferred when it has an amino group.
The alkyl group preferably has 1 to 20 carbon atoms, more preferably 2 to 10 carbon atoms.
When the above alkoxy group further has an amino group, it preferably has 2 to 10 carbon atoms, more preferably 2 to 4 carbon atoms. acid), titanium diisopropoxybis(triethanolamine), and the like.
The phosphate group is a phosphate ester group and preferably has 2 to 10 carbon atoms, more preferably 2 to 4 carbon atoms. Examples of having a phosphate ester group include n-propyl phosphate Preferred examples include titanium, n-butyl phosphate titanium, and the like.
Preferred examples having an acetyl group include diisopropoxybis(ethylacetoacetate)titanium, diisopropoxybis(ethylacetoacetate)titanium, and the like. Among them, it is preferable to have an acetylacetonate group, and preferred examples include titanium diisopropoxybis(ethylacetoacetate), titanium diisopropoxybis(acetylacetonate), titanium tetraacetylacetonate, and the like.
As the zirconium complex, the same zirconium complex as described above, in which titanium is replaced with zirconium, is preferably used.

The content of the complex cross-linking agent is preferably 0.1 to 10% by mass, more preferably 0.5 to 7% by mass, or more preferably 0.5 to 4% by mass, based on the total mass of the flexographic ink. It is preferably contained in the total weight of the flexographic printing layer in an amount of 0.2 to 24% by weight, more preferably 0.9 to 17% by weight or 1 to 10% by weight. The use of these complex cross-linking agents enhances the adhesiveness of packaging materials to plastic substrates and surface-coated paper substrates. This is because the cross-linking function of the entire flexographic printing layer is exhibited.

(nitrocellulose resin)
The nitrocellulose resin is preferably obtained as a nitric acid ester obtained by reacting natural cellulose with nitric acid to replace three hydroxyl groups in the six-membered ring of the anhydride glucopyranose group in the natural cellulose with nitric acid groups. The weight average molecular weight is preferably 10,000 to 100,000, more preferably 10,000 to 80,000. It is preferable because the strength of the ink film is improved, the solubility in solvents, the low-temperature stability of the ink, and the compatibility with the combined resin are improved. Also, the nitrogen content is preferably 10.5 to 12.5% by mass.

<Other binder resin>
As the binder resin, resins other than the above urethane resins and nitrocellulose resins may be used in combination. Examples include polyolefin resins, ethylene-vinyl acetate copolymer resins, polyester resins, acrylic resins, polyamide resins, urethane-acrylic resins, and styrene resins. , styrene-acrylic acid resin, styrene-maleic acid resin, maleic anhydride resin, maleic acid resin, vinyl acetate resin, rosin resin, rosin-modified maleic acid resin, cycloolefin resin, alkyd resin, polyvinyl chloride resin, terpene resin, Phenol-modified terpene resins, ketone resins, cyclized rubbers, chlorinated rubbers, butyral, petroleum resins, silicone resins and modified resins thereof can be mentioned. These resins can be used alone or in combination of two or more. The content thereof is preferably 10% by mass or less, preferably 5% by mass or less, relative to 100% by mass of the solid content of the binder resin. more preferred.

<Organic solvent>
The flexographic ink for forming the flexographic printing layer preferably contains an organic solvent. As the organic solvent, an alcohol-based organic solvent, an ester-based organic solvent, a glycol-based organic solvent, or the like can be appropriately used, and a mixed solvent is preferable. The organic solvent preferably contains 25 to 65% by mass of solids in the total amount of the flexographic ink. Ethanol, isopropyl alcohol, n-propyl alcohol and the like are preferable as the alcohol-based organic solvent, and ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate and the like are preferable as the ester-based organic solvent. Ethylene glycol mono-n-butyl ether, propylene glycol monopropyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether and the like are preferable as the glycol ether organic solvent.

(pigment)
The flexographic printing layer preferably contains a pigment, but the pigment used is not particularly limited. Any of organic pigments, inorganic pigments, and extender pigments can be used as the pigment, but inorganic pigments containing titanium oxide, and extender pigments such as silica, barium sulfate, kaolin, clay, calcium carbonate, and magnesium carbonate can be used. is preferred. Among organic pigments, it is preferable to use those composed of organic compounds and organometallic complexes.
In one embodiment, when a white pigment such as titanium oxide is included, it is preferably 40 to 90% by mass, more preferably 50 to 80% by mass in the total mass of the flexographic printing layer. When organic pigments or other chromatic pigments other than white pigments are included, the total weight of the flexographic printing layer is preferably 10 to 60% by mass, more preferably 20 to 50% by mass. .
In order to make the content of the pigment in the flexographic printing layer as described above, when a white pigment such as titanium oxide is included, it is preferably 20 to 50% by mass in the total mass of flexographic ink (100% by mass). , 25 to 45% by mass. In addition, when organic pigments or other chromatic pigments other than white pigments are included, the total weight of the flexo ink (100% by weight) is preferably 5 to 25% by weight, and 8 to 20% by weight. It is still preferred to have

(organic pigment)
Examples of the above organic pigments include, but are not limited to, soluble azo, insoluble azo, azo, phthalocyanine, halogenated phthalocyanine, anthraquinone, anthrone, dianthraquinonyl, and anthrapyrimidine pigments. , perylene type, perinone type, quinacridone type, thioindigo type, dioxazine type, isoindolinone type, quinophthalone type, azomethineazo type, flavanthrone type, diketopyrrolopyrrole type, isoindoline type, indanthrone type, carbon black type, etc. pigments.

The hue of the organic pigment is preferably at least one selected from the group consisting of black pigments, indigo pigments, green pigments, red pigments, purple pigments, yellow pigments, orange pigments and brown pigments. Furthermore, at least one or two or more selected from the group consisting of black pigments, indigo pigments, red pigments, and yellow pigments are preferred. Specific examples of organic pigments include C.I. I. Indicate by number.
Preferably C.I. I. Pigment Red 57:1, C.I. I. Pigment Red 48:1, C.I. I. Pigment Red 48:2, C.I. I. Pigment Red 48:3, C.I. I. Pigment Red 146, C.I. I. Pigment Red 242, C.I. I. Pigment Yellow 83, C.I. I. Pigment Yellow 14, C.I. I. Pigment Orange 38, C.I. I. Pigment Orange 13, C.I. I. Pigment Yellow 180, C.I. I. Pigment Yellow 139, C.I. I. Pigment Red 185, C.I. I. Pigment Red 122, C.I. I. Pigment Red 178, C.I. I. Pigment Red 149, C.I. I. Pigment Red 144, C.I. I. Pigment Red 166, C.I. I. Pigment Violet 23, C.I. I. Pigment Violet 37, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15:1, C.I. I. Pigment Blue 15:2, C.I. I. Pigment Blue 15:3, C.I. I. Pigment Blue 15:4, C.I. I. Pigment Blue 15:6, C.I. I. Pigment Green 7, C.I. I. Pigment Orange 34, C.I. I. Pigment Orange 64, C.I. I. Pigment Black 7, and it is preferable to use one or more of them.

Inorganic pigments include titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, aluminum particles, mica (mica), bronze powder, chromium vermillion, yellow lead, cadmium yellow, cadmium red, and ultramarine blue. , Prussian blue, red iron oxide, yellow iron oxide, iron black, etc. There are leafing type and non-leafing type aluminum, but non-leafing type is preferred.

<Titanium oxide pigment>
In the present invention, the titanium oxide pigment may have any of anatase, rutile, and brookite crystal structures. Among them, rutile-type titanium oxide is preferably used because of its good pigment dispersibility. In the industrial production of titanium oxide, rutile ore or ilmenite ore (FeTiO3) is used as a raw material. There are two main production methods, the chlorine method and the sulfuric acid method, and either method may be used.
In addition, since the printability is improved, the titanium oxide pigment is preferably surface-treated. In particular, those surface-treated with at least one metal selected from Si, Al, Zn, Zr and their oxides are preferred.

In addition, it preferably has an oil absorption of 14 to 35 ml/100 g, more preferably 17 to 32 ml/100 g, as measured by the method specified in JIS K5101. Also, the average particle size (median particle size) measured by a transmission electron microscope is preferably 0.2 to 0.3 μm. Also, the total content of the titanium oxide pigment is preferably 10 to 60% by weight, more preferably 10 to 45% by weight, based on 100% by weight of the ink. Also, a plurality of kinds of titanium oxide pigments may be used in combination.
In the flexographic ink of the present invention, other inorganic pigments and organic pigments can be used in combination with the titanium oxide pigment.

(Isocyanate curing agent)
The flexographic printing layer can further contain an isocyanate curing agent. As the isocyanate-based curing agent, polyisocyanates and modified compounds thereof can be used. Specifically, biuret, isocyanurate and adduct of polyisocyanate are suitable.

<Method for producing organic solvent-based flexographic ink>
The above flexographic ink can be produced by a known method. For example, a pigment dispersion obtained by dissolving and/or dispersing a nitrocellulose resin and a pigment in an organic solvent, a urethane resin and a complex crosslinking agent, and an organic solvent. can be produced by mixing Common dispersing machines are used for the production of pigment dispersions. For example, roller mills, ball mills, pebble mills, attritors, bead mills (sand mills, gamma mills, etc.) can be used. Among them, production using a bead mill dispersing machine such as a sand mill is preferable.

The viscosity of the flexographic ink produced by the above method is preferably in the range of 40 to 500 cps at 25° C. with a Brookfield viscometer in order to accommodate high-speed printing (50 to 400 m/min). More preferably 50 to 400 cps. This viscosity range corresponds to a viscosity of about 9 seconds to 50 seconds with a Zahn cup #4. The viscosity of the flexographic ink composition can be adjusted by appropriately selecting the types and amounts of raw materials used, for example, the amounts of organic pigments, binder resins, organic solvents, and the like.

<Formation of flexographic printing layer>
In the packaging material of the present invention, the printed layer obtained by the flexographic printing method has the characteristics of low film thickness and high density, excellent reproducibility of fine characters and sharp color reproduction, and less solvent discharge during printing. Compared to gravure printing, it is less and effective from the viewpoint of environmental consideration. Flexographic printing is a printing method in the field of packaging material printing, and is letterpress printing. The method of forming the flexographic printing layer may be performed by a known method. For example, ink is supplied from the ink supply part to the anilox roll by a doctor chamber method, a two-roll method, an ink fountain method, etc., and then a resin or rubber printing plate is formed. Ink is transferred to the raised portions of the plate, and the ink is transferred to the printing material passing between the impression cylinder to form a flexographic printing layer.
Examples of the plate include a photosensitive resin plate utilizing ultraviolet curing with a UV light source or an elastomer material plate using a direct laser engraving system. Regardless of the method of forming the image area of the flexographic plate, a plate having a screening ruling of 75 lpi or more is used.
As the anilox roll, a ceramics anilox roll with cell engraving, a chrome-plated anilox roll, or the like can be used. In order to obtain a printed matter having excellent dot reproducibility, an anilox roll having a ruling number of 5 times or more, preferably 6 times or more the plate ruling used in printing is used. For example, when the plate line number to be used is 75 lpi, an anilox roll of 375 lpi or more is required, and when the plate line number is 150 lpi, an anilox roll of 750 lpi or more is required. Regarding the anilox capacity, the anilox roll has a capacity of 1 to 10 cc/m ³ , preferably 2 to 9 cc/m ³ .
In order to obtain the properties of the packaging material of the present invention, it is preferable to use a plate of 80 to 175 lpi and an anilox roll of 200 to 1400 lpi for the flexographic printing layer. As for the shape of the obtained flexographic printing layer, the film thickness is preferably 0.5 to 7 μm, more preferably 1 to 6 μm.

<Fusible polyolefin resin layer>
It is preferred to have an adhesive layer between the flexographic printing layer and the substrate 2 . As the adhesive layer, a meltable polyolefin resin layer is preferable.
The meltable polyolefin resin layer contains a meltable polyolefin resin. The meltable polyolefin resin is a thermoplastic polyolefin resin that is used in a molten state during lamination. The polyolefin resin is in a molten state at 280° C. to 360° C., and is laminated so as to be arranged between the flexographic printing layer on the base material 1 (on the anchor layer if it has an anchor layer) and the base material 2. be. Further, the thickness of the meltable polyolefin resin layer in the laminate is preferably adjusted to 10 to 50 μm. Polyolefins include, for example, low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, etc., and preferably have a melting point of 90°C to 200°C.
In order to obtain the properties of the packaging material of the present invention, the meltable polyolefin resin layer preferably melts at 300 to 350° C. and has a thickness of 10 to 50 μm.

<Base material 1>
The substrate 1 preferably has a wettability index of 30 to 60 dyne/cm on the surface to be flexographically printed (the surface in contact with the printed layer). More preferably, it is 35 to 55 dyne/cm. The wetness index is a value measured by the method described in JISK6768 using a wetness index standard solution.
The substrate 1 that can be used for the printed matter of the present invention includes, for example, polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate, polycarbonate and polylactic acid; polystyrene resins such as polystyrene, AS resin and ABS resin; Examples include film-like substrates made of vinyl chloride, polyvinylidene chloride, cellophane, paper, aluminum, or composite materials thereof. In addition, a vapor deposition substrate obtained by vapor-depositing an inorganic compound such as silica, alumina, or aluminum on a polyethylene terephthalate or nylon film may also be used, and the vapor-deposited surface may be coated with polyvinyl alcohol or the like.
The base material 1 is preferably treated for easy adhesion so that the wetting index of the surface in contact with the flexographic printing layer is within the above range. The easy-adhesion treatment includes, for example, corona discharge treatment, ultraviolet/ozone treatment, plasma treatment, oxygen plasma treatment, primer treatment, and the like. For example, in corona discharge treatment, hydroxyl groups, carboxyl groups, carbonyl groups, and the like appear on the substrate. Since hydrogen bonding can be used, the ink preferably contains a compound having a functional group such as a hydroxyl group or an amino group.

<Base material 2>
The substrate 2 may be the same as the substrate 1 and may be the same or different. Among them, unstretched polyethylene, unstretched polypropylene, nylon substrates, aluminum foil substrates, aluminum deposition substrates and the like are preferable. Those having heat sealability such as unstretched polyethylene and unstretched polypropylene are preferable.

<Packaging material>
The packaging material of the present invention is obtained by extrusion lamination. Preferably, it is a packaging material having a base material 1, a flexographic printing layer, a meltable polyolefin resin layer (for example, a low-density polyethylene resin layer) and a base material 2 in this order. Furthermore, a form having an anchor layer is preferred. The laminated structure of the packaging material of the present invention is listed below, but is not limited to the following.
Biaxially oriented propylene film/Flexographic printing layer/Low density polyethylene resin layer/Unoriented polyethylene film Biaxially oriented propylene film/Flexographic printing layer/Anchor layer/Low density polyethylene resin layer/Unoriented polyethylene film Biaxially oriented propylene film/Flexographic Printed layer/anchor layer/low-density polyethylene resin layer/unstretched polypropylene film biaxially-stretched propylene film/flexographic print layer/anchor layer/low-density polypropylene resin layer/unstretched polyethylene film polyethylene terephthalate film/flexographic print layer/anchor layer/ Low-density polyethylene resin layer/Unstretched polyethylene film Polyethylene terephthalate film/Flexographic printing layer/Anchor layer/Low-density polyethylene resin layer/Unstretched polypropylene film

<Anchor layer>
The anchor layer includes any anchor layer selected from the group consisting of imine anchor layers, butadiene anchor layers and isocyanate anchor layers. The anchor layer is formed by applying an anchor agent, and specific examples include polyethyleneimine for the imine anchor layer, modified polybutadiene for the butadiene anchor layer, and polyurethane composed of polyol and polyisocyanate for the isocyanate anchor layer. , but not limited to.
The anchor layer is formed in a solid state by coating the flexographic printing layer with the above-described anchor agent diluted with a solvent such as water or an organic solvent, and then evaporating and drying the solvent in a dryer. The resulting anchor layer preferably has a coating amount of 0.002 to 4 g/m ² , more preferably 0.01 to 0.6 g/m ² .

<Method for manufacturing packaging material>
In the packaging material of the present invention, the organic solvent-based flexographic ink is printed on the substrate 1 to form a flexographic printing layer, the anchor layer is applied on the flexographic printing layer, and the meltable polyolefin resin is added at 280 to 360. ° C. and coated on the anchor layer of the base material 1/flexographic printing layer/anchor layer thus prepared, and at the same time, the base material 2 is continuously pressure-bonded to bond them together. That is, it has substrate 1/flexographic printing layer/anchor layer/meltable polyolefin resin layer/substrate 2 in this order. An intermediate layer may be further provided between the meltable polyolefin resin layer and the substrate 2. For example, a polyamide substrate (nylon substrate) layer or a polyester substrate layer is preferable, and a polyester substrate on which aluminum is vapor-deposited is preferable. It is preferably a material layer. These are laminated via the meltable polyolefin resin layer in the same manner as described above. However, the present invention is not limited to these.

<Packaging bag made of packaging material>
In the packaging material of the present invention, by selecting a base material having heat-sealing properties as the base material 2, parts of the packaging material can be bonded together to form a bag, thereby obtaining a packaging bag. Specifically, the resulting packaging material is cut to a suitable size, folded into a bag so that the base material 2 of the cut packaging material is on the inside, and the edges are thermally crimped (heat-sealed). ) to obtain a packaging bag.

EXAMPLES The present invention will be described in detail below with reference to examples, but the following embodiments are merely examples of the present invention, and the present invention is not limited to these examples. Parts and % in the present invention represent parts by mass and % by mass unless otherwise specified.

(hydroxyl value)
It was measured according to the method described in JISK0070.

(amine value)
The amine value was obtained in mg of potassium hydroxide equivalent to the equivalent of hydrochloric acid required to neutralize the amino groups contained in 1 g of the resin according to JIS K0070 according to the following method.
0.5 to 2 g of the sample was accurately weighed (sample solid content: Sg). 50 mL of a mixed solution of methanol/methyl ethyl ketone=60/40 (mass ratio) was added to the accurately weighed sample to dissolve the sample. Bromophenol blue was added to the resulting solution as an indicator, and the resulting solution was titrated with a 0.2 mol/L ethanolic hydrochloric acid solution (potency: f). The point at which the color of the solution changed from green to yellow was defined as the end point, and the titration amount (AmL) at this time was used to determine the amine value by the following (formula 2).
(Formula 2) Amine value = (A x f x 0.2 x 56.108) / S [mgKOH/g]

(Weight average molecular weight)
The weight-average molecular weight was obtained by measuring the molecular weight distribution using a GPC (gel permeation chromatography) device (HLC-8220 manufactured by Tosoh Corporation) and obtaining the converted molecular weight using polystyrene as a standard substance. Measurement conditions are shown below.
Column: The following columns were connected in series and used.
TSKgel SuperAW2500 manufactured by Tosoh Corporation
TSKgel SuperAW3000 manufactured by Tosoh Corporation
TSKgel SuperAW4000 manufactured by Tosoh Corporation
TSKgel guard column SuperAWH manufactured by Tosoh Corporation
Detector: RI (differential refractometer)
Measurement conditions: Column temperature 40°C
Eluent: Tetrahydrofuran Flow rate: 1.0 mL/min <Preparation of urethane resin (A)>

[Synthesis Example 1] (Synthesis of urethane resin P1-1)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet tube was charged with 40% of polyether polyol A (a polyether polyol having a number average molecular weight of 3,000, which is polypropylene glycol "PPG"). 3 parts, 4.4 parts of 4,4′-diphenylmethane isocyanate (hereinafter also abbreviated as “MDI”), and 20 parts of ethyl acetate were charged and reacted at 75° C. for 1 hour under a nitrogen stream to obtain a prepolymer having an isocyanato group at its end. A solution containing After cooling the resulting prepolymer solution to 40° C., 0.3 part of isophoronediamine (hereinafter also abbreviated as “IPDA”) was gradually added dropwise over 60 minutes, and then reacted at 40° C. for 1 hour. Further, 12 parts of 2-propanol (hereinafter also abbreviated as “IPA”) was gradually added dropwise and reacted at 70° C. for 1 hour to obtain a urethane resin P1-1 solution having a weight average molecular weight of 50,000 and a solid content of 45.0% by mass. .

[Synthesis Example 2] (Synthesis of urethane resin P1-2)
Urethane resin P1 having a weight average molecular weight of 35,000 and a solid content of 45.0% by mass was prepared in the same manner as in Synthesis Example 1 except that the amount of polyether polyol A was changed to 39.5 parts and the amount of MDI was changed to 5.2 parts. A -2 solution was obtained.

[Synthesis Example 3] (Synthesis of urethane resin P1-3)
Synthesis except that polyether polyol A was polyester polyol A (polyester polyol having a number average molecular weight of 2,000, which is "PMPA" which is a condensation product of adipic acid and 3-methyl-1,5-pentanediol) A urethane resin P1-3 solution having a weight average molecular weight of 50,000 and a solid content of 45.0% by mass was obtained in the same manner as in Example 1.

[Synthesis Example 4] (Synthesis of urethane resin P2-1)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet tube was charged with 69.0 ml of polyether polyol B (a polyester polyol having a number average molecular weight of 2,000, which is polypropylene glycol "PPG"). 6.0 parts of MDI and 10 parts of ethyl acetate were charged and reacted at 75°C for 1 hour under a nitrogen stream. A urethane resin P2-1 solution of 75.0% by mass was obtained.

[Comparative Synthesis Example 1] (Synthesis of urethane resin PP1)
A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas inlet tube was charged with polyester polyol A (“PMPA” which is a condensate of adipic acid and 3-methyl-1,5-pentanediol). 190 parts of 1,4-butanediol (hereinafter also abbreviated as “1,4-BD”), isophorone diisocyanate (hereinafter also abbreviated as “IPDI”) 64 .1 part and 66.0 parts of ethyl acetate were charged and reacted at 80° C. for 4 hours under a nitrogen stream to obtain a solution containing a prepolymer having terminal isocyanato groups. Next, 14.87 parts of isophoronediamine (hereinafter also abbreviated as "IPDA") and 584.9 parts of a mixed solvent of ethyl acetate/IPA = 50/50 (mass ratio) were mixed, and the above prepolymer solution was gradually added at 40°C. and reacted at 80° C. for 1 hour to obtain a urethane resin PP1 solution having a weight average molecular weight of 100,000, an amine value of 6.0 mgKOH/g and a solid content of 30.0% by mass.

[Ink Production Example 1] (Production of flexographic ink C1)
13 parts of Lionol blue FG-7400-G (C.I. Pigment Blue 15:4 manufactured by Toyocolor Co., Ltd.), which is a phthalocyanine indigo pigment, and a nitrocellulose resin solution ((DHX4-6: Inabata Sangyo) 43 parts / ethyl acetate 30 26 parts of ethanol/23 parts of ethanol/4 parts of IPA), 14 parts of IPA, and 7 parts of ethyl acetate are stirred and mixed, and the pigment is dispersed in a bead mill (using zirconia beads). %), 14 parts of IPA, 10.5 parts of ethyl acetate, and 1.5 parts of titanium n-butyl phosphate were stirred and mixed to obtain flexographic ink C1.

[Ink Production Examples 2 to 6] (Production of flexographic inks C2 to C6)
Flexographic inks C2 to C6 were obtained in the same manner as in Production Example 1, except that the raw materials and usage ratios shown in Table 1-1 were used. In addition, the numerical value in a table|surface represents the total value of each component.

[Ink Comparative Production Example 1] (Production of flexographic ink CC1)
13 parts of Lionol blue FG-7400-G (C.I. Pigment Blue 15:4 manufactured by Toyocolor Co., Ltd.), which is a phthalocyanine indigo pigment, and a nitrocellulose resin solution ((DHX4-6: Inabata Sangyo) 43 parts / ethyl acetate 30 26 parts of ethanol/23 parts of ethanol/4 parts of IPA), 14 parts of IPA, and 7 parts of ethyl acetate are stirred and mixed, and the pigment is dispersed in a bead mill (using zirconia beads). ), 14 parts of IPA, 10.5 parts of ethyl acetate, and 1.5 parts of n-butyl phosphate titanium were stirred and mixed to obtain flexographic ink CC1.

[Ink Comparative Production Examples 2 to 5] (Production of flexographic inks CC2 to CC5)
Flexo inks CC2 to CC5 were obtained in the same manner as in Comparative Production Example 1, except that the raw materials and usage ratios shown in Table 1-2 were used. In addition, the numerical value in a table|surface represents the total value of each component.

[Ink Production Example 7] (Production of flexographic ink W1)
35 parts of titanium oxide Tipaque PFR210 (manufactured by Ishihara Sangyo Co., Ltd.), nitrocellulose resin solution ((DHX4-6: Inabata Sangyo) 43 parts / ethyl acetate 30 parts / ethanol 23 parts / IPA 4 parts) 17 parts, IPA 11 parts of ethyl acetate and 7 parts of ethyl acetate were stirred and mixed, and the pigment was dispersed with a bead mill (using zirconia beads). 10 parts of IPA, 5.5 parts of ethyl acetate, and 1.5 parts of n-butyl phosphate titanium were stirred and mixed to obtain flexographic ink W1.

[Ink Production Examples 8-14] (Production of flexographic inks W2-8)
Flexographic inks W2 to W8 were obtained in the same manner as in Production Example 4, except that the raw materials and usage ratios shown in Table 2-1 were used. In addition, the numerical value in a table|surface represents the total value of each component.

[Ink Comparative Production Example 6] (Production of flexographic ink WW1)
35 parts of titanium oxide Tipaque PFR210 (manufactured by Ishihara Sangyo Co., Ltd.), nitrocellulose resin solution ((DHX4-6: Inabata Sangyo) 43 parts / ethyl acetate 30 parts / ethanol 23 parts / IPA 4 parts) 17 parts, IPA 11 parts of ethyl acetate and 7 parts of ethyl acetate were stirred and mixed, and the pigment was dispersed with a bead mill (using zirconia beads). 1.5 parts of titanium acid ester were stirred and mixed to obtain flexographic ink WW1.

[Ink Comparative Production Examples 7 to 10] (Production of flexographic inks WW2 to WW10)
Flexographic inks WW2 to WW10 were obtained in the same manner as in Comparative Production Example 6, except that the raw materials and usage ratios shown in Table 2-2 were used. In addition, the numerical value in a table|surface represents the total value of each component.

The following substrates 1 were used in the following examples and comparative examples.
・ PET film: E5100 #15 manufactured by Toyobo Co., Ltd., film thickness 15 μm
・ OPP film: FOR-BT #20 manufactured by Futamura Chemical Co., Ltd., double-sided corona discharge treated polypropylene film film thickness 20 μm

The following anchoring agents were used and adjusted in the following examples and comparative examples.
Polyethyleneimine anchor coating agent: 400 parts of EL420 manufactured by Toyo-Morton Co., Ltd., 2800 parts of methanol, and 800 parts of water were mixed and used.
Isocyanate-based anchoring agent: 540 parts of EL540 manufactured by Toyo-Morton Co., Ltd., 80 parts of CAT-RT32 manufactured by Toyo-Morton Co., Ltd., and 3380 parts of ethyl acetate were mixed and used.
• Butadiene-based anchoring agent: 500 parts of EL451 manufactured by Toyo-Morton Co., Ltd. and 4500 parts of methanol were mixed and used.

The following meltable polyolefin resin layers were used in the following examples and comparative examples.
・ Molten polyethylene (also referred to as exPE): Novatec AC-600 manufactured by Japan Polychem Co., Ltd.
・ Molten polypropylene (also referred to as exPP): Novatec FL02A manufactured by Japan Polychem Co., Ltd.

The following substrates 2 were used in Examples and Comparative Examples.
・ L-LDPE film: TUX-FCD # 40 manufactured by Mitsui Chemicals Tohcello, film thickness 40 μm
・CPP film: ZK207#60 manufactured by Toray Industries, Inc., film thickness 60 μm

(Example A1)
[Production of packaging material a1]
The viscosity of flexo ink C1 was diluted with a mixed solvent of n-propyl alcohol/n-propyl acetate = 70/30 so that the viscosity in Zahn cup #4 (manufactured by Rigosha) was 16.0 seconds (at 25°C). , using a flexographic proofing machine equipped with a flexographic plate (150 LPI) and an anilox roll (1200 LPI, 3.0 cc/m ³ ), at a speed of 50 m / min, PET film (E5100 # 15, manufactured by Toyobo Co., Ltd.), which is a plastic substrate ) and dried at 40 to 50° C. to form a flexographic print layer.
After that, a solution with a solid content of 1% (weight ratio) was obtained by diluting a polyethyleneimine anchor coating agent (EL420, manufactured by Toyo-Morton Co., Ltd.) with a solvent consisting of methanol/water = 70/30 for printed matter having a flexographic printing layer. It is applied to the printed material, passed through a dryer at 60 ° C to evaporate the methanol and water in the anchor coating agent and dried, melted polyethylene resin (Novatec AC-600, manufactured by Japan Polychem Co., Ltd.) with an extrusion laminator, and further the base material A packaging material a1 was obtained by laminating the sealant L-LDPE (TUX-FCD, manufactured by Mitsui Chemicals Tohcello, Inc.) corresponding to 2.

(Examples A2 to A9)
[Production of packaging materials a2 to a9]
Packaging materials a2 to a9 were prepared in the same manner as in Example A1, except that the flexographic inks C1 to C6, the base film, the anchoring agent, the meltable polyolefin resin layer, and the base material 2 listed in Table 3-1 were used. Obtained.

(Comparative Examples A1 to A5)
[Production of packaging materials aa1 to aa5]
Packaging materials aa1 to aa5 were prepared in the same manner as in Example A1 except that the flexographic inks CC1 to CC5, the base film, the anchoring agent, the meltable polyolefin resin layer, and the base material 2 listed in Table 3-2 were used. Obtained.

(Example B1)
[Production of packaging material b1]
The viscosity of flexographic ink W1 was diluted with a mixed solvent of n-propyl alcohol/n-propyl acetate = 70/30 so that the viscosity in Zahn cup #4 (manufactured by Rigosha) was 16.0 seconds (at 25°C). , using a flexographic proofing machine equipped with a flexographic plate (150 LPI) and an anilox roll (1200 LPI, 3.0 cc/m ³ ) at a speed of 50 m/min. and dried at 40 to 50° C. to form a flexographic printing layer. After that, a solution with a solid content of 1% (weight ratio) was obtained by diluting a polyethyleneimine anchor coating agent (EL420, manufactured by Toyo-Morton Co., Ltd.) with a solvent consisting of methanol/water = 70/30 for printed matter having a flexographic printing layer. It is applied to the printed material, passed through a dryer at 60 ° C to evaporate the methanol and water in the anchor coating agent and dried, melted polyethylene resin (Novatec AC-600, manufactured by Japan Polychem Co., Ltd.) with an extrusion laminator, and further the base material A packaging material b1 was obtained by laminating the sealant L-LDPE (TUX-FCD, manufactured by Mitsui Chemicals Tohcello, Inc.) corresponding to 2.

(Examples B2 to B11)
[Production of packaging materials b2 to b11]
Packaging materials b2 to b11 were prepared in the same manner as in Example B1, except that the flexographic inks W1 to W8, base film, anchoring agent, meltable polyolefin resin layer, and base material 2 listed in Table 4-1 were used. Obtained.

(Comparative Examples B1 to B5)
[Production of packaging materials bb1 to bb5]
Packaging materials bb1 to bb5 were prepared in the same manner as in Example B1, except that the flexographic inks WW1 to WW5, the base film, the anchoring agent, the meltable polyolefin resin layer, and the base material 2 shown in Table 4-2 were used. Obtained.

[Characteristic evaluation]
The packaging materials a1 to a9, aa1 to aa5, b1 to b11, and bb1 to bb5 obtained in the above Examples and Comparative Examples were evaluated for their properties as described below.

<Appearance of packaging material>
Observe and evaluate the discoloration, color development, and appearance of the printed part of the packaging material.
〇: Good condition ×: Poor condition

<Laminate strength>
The resulting packaging material using flexo ink and the printed portion were cut to a width of 15 mm, and the ink surface and the substrate surface were peeled off, and then the peel strength (laminate strength) was measured using a 201 universal tensile tester manufactured by Intesco. did.
[Evaluation criteria]
5. Tensile strength is 1.0 N / 15 mm or more (good)
4. Tensile strength is less than 0.6N/15mm, 1.0N/15mm (practical)
3. Tensile strength is less than 0.4N/15mm, 0.6N/15mm (slightly poor)
2. Tensile strength is less than 0.2N/15mm, 0.4N/15mm (defective)
1. Tensile strength is less than 0.2N/15mm (extremely poor)
Note that 5 and 4 are within a practically acceptable range.

<Heat seal strength>
The obtained laminate was cut into a width of 15 mm, and the sealant surfaces were put together and heat-bonded with a single-acting heat sealer under the conditions of a sealing temperature of 160°C, a sealing time of 1.0 seconds, and a sealing pressure of 0.2 MPa. The peel strength (heat seal strength) was measured with a 201 universal tensile tester manufactured by Intesco.
[Evaluation criteria]
5. Tensile strength is 4.0 N / 15 mm or more (good)
4. Tensile strength is 2.5 N/15 mm or more and less than 4.0 N/15 mm (good)
3. Tensile strength is 1.5 N/15 mm or more and less than 2.5 N/15 mm (practical level)
2. Tensile strength is 1.0 N/15 mm or more and less than 1.5 N/15 mm (defective)
1. Tensile strength is less than 1.0 N/15 mm (extremely poor)
Note that 5, 4, and 3 are within a practically acceptable range.

From the above results, the packaging materials corresponding to the examples of the present invention can obtain high lamination strength in extrusion lamination, and furthermore, it is possible to provide packaging materials excellent in heat seal strength and packaging material appearance. became. Among them, Examples A1, A7, B1 and B9 using flexographic inks C1 and W1 are particularly excellent in lamination strength and heat seal strength. In contrast, Comparative Examples A1 and B1 using a urethane resin having a terminal amine structure, and Comparative Examples A4, A5, B4 and B5 in which the ratio of the urethane resin to the nitrocellulose resin was out of range were inferior in packaging material appearance. Also, Comparative Examples A1, A2, B1, and B2, in which the weight-average molecular weight of the urethane resin was exceeded, and Comparative Examples A3, B3, in which no complex cross-linking agent was used, had low lamination strength.

Claims (7)

A packaging material having a substrate 1, a flexographic printing layer, and a substrate 2 in sequence, wherein the flexographic printing layer satisfies (1) and (2) below.
(1) The flexographic printing layer contains a nitrocellulose resin and a urethane resin in a mass ratio of 99:1 to 40:60, and a complex cross-linking agent.
(2) The urethane resin contains a urethane resin (A) having a weight average molecular weight of 20,000 or more and 80,000 or less. 2. The packaging material according to claim 1, further comprising a meltable polyolefin resin layer between the flexographic printing layer and the substrate 2. 3. The flexographic printing layer according to claim 1 or 2, which has at least one anchor layer selected from the group consisting of an imine anchor layer, a butadiene anchor layer and an isocyanate anchor layer on the surface opposite to the substrate 1 of the flexographic printing layer. packaging material. The packaging material according to any one of claims 1 to 3, wherein the urethane resin contains structural units derived from polyether. The packaging material according to any one of claims 1 to 4, wherein the urethane resin further contains a urethane resin (B) having a weight average molecular weight of 5000 or more and less than 20000. The packaging material according to any one of claims 1 to 5, wherein the complex cross-linking agent is a titanium complex and/or a zirconium complex. A method for producing a packaging material sequentially having a base material 1, a flexographic printing layer, an anchor layer, a meltable polyolefin resin layer and a base material 2,
A step of flexographically printing an organic solvent-based flexographic ink on the base material 1 to form the flexographically printed layer,
The organic solvent-based flexographic ink contains a nitrocellulose resin and a urethane resin in a mass ratio of 99:1 to 40:60, and a complex cross-linking agent,
A method for producing a packaging material, wherein the urethane resin contains a urethane resin (A) having a weight average molecular weight of 20,000 or more and 80,000 or less.