JP7512545B1 - Ink composition for shrink labels, laminates and packaging materials - Google Patents

Abstract

[Problem] To provide an ink composition for shrink labels capable of forming an ink layer that has excellent resistance to whitening in hot water, shrink suitability, and alkali release properties, a laminate comprising said ink layer, and a packaging material comprising said laminate. [Solution] An ink composition for shrink labels containing a urethane resin (A), a (meth)acrylic resin (B), and a rosin derivative (C), wherein the urethane resin (A) has a glass transition temperature of -60 to -20°C, the (meth)acrylic resin (B) has an acid value of less than 10 mgKOH/g, and the rosin derivative (C) has an acid value of 150 to 310 mgKOH/g. [Selected Figures] None

Description

The present invention relates to an ink composition for shrink labels, a laminate, and a packaging material.

Shrink labels are plastic films that have heat shrinkability, and the base film used for shrink labels is heat shrinkable polyester film, polystyrene film, polyolefin film, etc. Shrink labels are widely used for beverages, foods, daily necessities, etc. as labels and packaging materials to add design features and display product information, etc.
Shrink labels are wrapped around an object and then heated to cause them to thermally shrink and conform to the shape of the object, making them suitable for attachment to containers with complex shapes.

Typically, a shrink label is configured so that, when viewed from the viewing direction, a base film and an ink layer are disposed in this order.
As the ink composition for forming the ink layer, from the viewpoint of adhesion to the base film, a urethane-based ink is generally used for a heat-shrinkable polyester film, and an acrylic-based ink is generally used for a polystyrene film.

In order to improve the coating film properties such as heat resistance and abrasion resistance of an ink layer formed from a urethane-based ink (hereinafter also referred to as a "urethane-based ink layer"), a protective layer containing an acrylic resin (hereinafter also referred to as an "acrylic protective layer") may be provided on the urethane-based ink layer.
For example, Patent Document 1 discloses a shrink label which has a label base material, a printed layer containing a urethane resin (urethane-based ink layer) provided on at least one surface of the label base material, and a protective layer provided so as to cover at least a portion of the printed layer, wherein the protective layer is a layer (acrylic-based protective layer) formed by curing a curable composition layer containing a polyacrylic polyol resin and a curing agent, and the printed layer does not contain a constituent unit derived from the curing agent.

In recent years, there has been a demand for the reuse of plastic films as a measure to address environmental issues including the problem of microplastics.
However, when plastic films used in packaging materials are reused, if ink is attached to the plastic film, it will cause a deterioration in the hue of the recycled plastic film and a decrease in its physical properties. Therefore, it is preferable to remove the ink layer from the plastic film before reuse. Since the ink layer is often removed using an aqueous solution in which an alkaline agent, which is a release agent, is dissolved in water, the ink layer is required to have excellent alkaline release properties.

As an ink composition having alkali releasing properties, for example, Patent Document 2 discloses an organic solvent-based printing ink containing a polyurethane resin having an acid value of 15 to 70 mgKOH/g.
Furthermore, Patent Document 3 discloses a packaging material that includes, in this order, a first substrate, a primer layer for removing the first substrate, and a printed layer, in which the primer layer contains a cured product of a urethane resin and a polyisocyanate.

JP 2017-67928 A JP 2020-90627 A JP 2021-88408 A

However, in the shrink label described in Patent Document 1, although whitening during thermal shrinkage can be suppressed because the urethane ink layer does not contain a curing agent, the adhesion between the urethane print layer and the acrylic protective layer is insufficient. Therefore, when the shrink label described in Patent Document 1 is immersed in warm water, water may get between the urethane print layer and the acrylic protective layer, causing whitening.

The organic solvent-based printing ink described in Patent Document 2 is intended for printing on plastic substrates such as polyester substrates (PET), nylon substrates (NY), and polypropylene substrates (OPP), but is not intended for use in shrink labels and does not fully satisfy the shrink suitability required of an ink for shrink labels.
The packaging material described in Patent Document 3 has poor ink conformity when the film shrinks, and does not fully satisfy shrink suitability. In addition, a primer layer needs to be provided to impart alkali release properties, which increases the number of manufacturing steps when producing the packaging material.

The present invention aims to provide an ink composition for shrink labels that can form an ink layer that has excellent resistance to whitening in hot water, shrink suitability, and alkali release properties, a laminate that includes the ink layer, and a packaging material that includes the laminate.

The present invention has the following aspects.
[1] A shrink label ink composition containing a urethane resin (A), a (meth)acrylic resin (B), and a rosin derivative (C), wherein the urethane resin (A) has a glass transition temperature of -60 to -20°C, the (meth)acrylic resin (B) has an acid value of less than 10 mgKOH/g, and the rosin derivative (C) has an acid value of 150 to 310 mgKOH/g.
[2] The ink composition for a shrink label according to [1] above, wherein the (meth)acrylic resin (B) has a glass transition temperature of 30 to 80° C.
[3] The ink composition for shrink labels according to [1] or [2] above, wherein the content of the urethane resin (A) is 2 to 10 mass %, calculated as solid content, the content of the (meth)acrylic resin (B) is 0.5 to 5 mass %, calculated as solid content, the content of the rosin derivative (C) is 2 to 6 mass %, calculated as solid content, and the total content of the urethane resin (A), the (meth)acrylic resin (B), and the rosin derivative (C) is 5 to 15 mass %, calculated as solid content, relative to the total mass of the ink composition for shrink labels.
[4] The ink composition for a shrink label according to any one of [1] to [3] above, further comprising a (meth)acrylic resin (D), the (meth)acrylic resin (D) having an acid value of 40 to 100 mg KOH/g, and the content of the (meth)acrylic resin (D) relative to the total mass of the ink composition for a shrink label, calculated as solid content, is 0.1 to 2 mass%.
[5] The ink composition for a shrink label according to any one of [1] to [4] above, further comprising silica (F).
[6] The ink composition for a shrink label according to any one of [1] to [5] above, which is for gravure printing.
[7] A laminate comprising a plastic film and an ink layer provided on one surface of the plastic film, the ink layer being a layer formed using the shrink label ink composition described in any one of [1] to [6] above.
[8] A packaging material comprising the laminate according to [7] above.

The present invention provides an ink composition for shrink labels that can form an ink layer that is excellent in hot water whitening resistance, shrink suitability, and alkali release properties, a laminate that includes the ink layer, and a packaging material that includes the laminate.

FIG. 1 is a cross-sectional view illustrating a schematic example of a laminate of the present invention.

The present invention will be described in detail below. The following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to these embodiments. The present invention can be implemented in various forms without departing from the spirit of the present invention.
In the present invention, the contents of the urethane resin (A), the (meth)acrylic resin (B), the rosin derivative (C), the (meth)acrylic resin (D), and the cellulose resin (E) in the ink composition for shrink labels are each expressed as amounts calculated on a solids basis (also referred to as "non-volatile content basis").
"Solid content" refers to the components contained in the ink composition for shrink labels excluding volatile media such as organic solvents, i.e., non-volatile components, and is the component that will ultimately form the ink layer. Specifically, it was measured in accordance with JIS K 5601-1-2:2008.
In addition, in this specification, the term "ink layer" refers to an ink coating film formed from the ink composition for shrink labels of the present invention.
In addition, in this specification, the term "(meth)acrylic" is meant to include both the terms "acrylic" and "methacrylic".
In addition, in this specification, the term "to" indicating a range of values means that the values before and after it are included as the lower and upper limits. For example, A to B is equivalent to A or more and B or less.

In this specification, "hot water whitening" means that whitening occurs when the ink layer is immersed in hot water, and "resistance to hot water whitening" means the ability to resist hot water whitening. Hot water whitening may occur at the interface between the ink layer and the protective layer even when the ink layer is in contact with the protective layer and the surface of the ink layer is protected by the protective layer and not exposed, if the adhesion between the ink layer and the protective layer is insufficient. In particular, when the ink layer is in contact with a layer containing a (meth)acrylic resin and immersed in hot water, if the adhesion between the ink layer and the layer containing a (meth)acrylic resin is insufficient, whitening tends to occur at the interface between them.
Here, "warm water" means water at a temperature of 35 to 60°C.

In addition, in this specification, "shrinkability" refers to the ability of the ink layer to resist cracking when a laminate having an ink layer (such as a shrink label) is heated and thermally shrunk while in contact with an object.
When attaching a shrink label to an object, first, with the printed surface (ink layer) on the inside, the edges of the shrink labels are overlapped by a few millimeters to 1 cm, and then melted and pressed with a solvent or the like to form the shrink label into a cylindrical shape. This is then placed over the object, and heated to cause thermal shrinkage, thereby attaching the shrink label to the object. At this time, a large amount of pressure is applied to the overlapping parts of the shrink label, so if there is an ink layer in the overlapping parts of the shrink label, cracks will occur in the ink layer at that location, which is a problem known as edge cracking. In this specification, "shrink suitability" is an evaluation item that indicates the degree to which this edge cracking occurs.

In addition, in this specification, "alkali releasability" means the ability of the ink layer to be detached (removed) from a plastic film by swelling, dissolution, erosion, or the like due to an alkaline aqueous solution in which an alkaline agent (detachment agent) is dissolved in water.
Examples of the alkaline agent include sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonia, and sodium carbonate.

[Ink composition for shrink labels]
[0023] The ink composition for a shrink label according to one embodiment of the present invention (hereinafter simply referred to as the "ink composition") contains the following urethane resin (A), (meth)acrylic resin (B), and rosin derivative (C).
In addition to the urethane resin (A), the (meth)acrylic resin (B), and the rosin derivative (C), the ink composition preferably further contains one or more selected from the following (meth)acrylic resin (D), cellulose resin (E), and silica (F).
The ink composition may further contain components (optional components) other than the urethane resin (A), the (meth)acrylic resin (B), the rosin derivative (C), the (meth)acrylic resin (D), the cellulose resin (E), and the silica (F) as necessary, within a range that does not impair the effects of the present invention. For example, the ink composition typically further contains an organic solvent.

<Urethane resin (A)>
The urethane resin (A) may be a reaction product (polyurethane) obtained by polymerizing a polyisocyanate and a polyol. In particular, a thermoplastic polyurethane soluble in an organic solvent, which will be described later, is preferred.
These urethane resins (A) may be used alone or in combination of two or more.

Polyurethane can be produced by a conventional method. For example, a urethane prepolymer, which is a reaction product of polyisocyanate and polyol, can be reacted with a chain extender and a reaction terminator as necessary to produce the urethane resin (A).

A polyisocyanate is a compound having two or more isocyanate groups in one molecule.
The polyisocyanate may be a diisocyanate compound.
Examples of diisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4-diphenylether diisocyanate, 2-nitrodiphenyl-4,4-diisocyanate, 2,2-diphenylpropane-4,4-diisocyanate, 3,3-dimethyldiphenylmethane-4,4-diisocyanate, 4,4-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthyl diisocyanate, aromatic diisocyanates such as naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, and 3,3-dimethoxydiphenyl-4,4-diisocyanate; aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated diphenylmethane diisocyanate.
These polyisocyanates may be used alone or in combination of two or more kinds.

A polyol is a compound having two or more hydroxyl groups in one molecule.
Examples of the polyol include polyester polyol, polycarbonate polyol, and polyether polyol.
These polyols may be used alone or in combination of two or more kinds.

Examples of the polyester polyol include polyester polyols and polyesteramide polyols obtained by a dehydration polycondensation reaction between a polyvalent carboxylic acid and a polyhydric alcohol or a secondary or tertiary amine.
Specific examples of polyvalent carboxylic acids include polycarboxylic acids such as succinic acid, adipic acid, sebacic acid, azelaic acid, terephthalic acid, isophthalic acid, orthophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, hexahydroorthophthalic acid, naphthalenedicarboxylic acid, and trimellitic acid; and acid esters or acid anhydrides of these polycarboxylic acids.
These polyvalent carboxylic acids may be used alone or in combination of two or more kinds.

Specific examples of polyhydric alcohols include low molecular weight alcohol compounds such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanedimethanol, ethylene oxide or propylene oxide adduct of bisphenol A, trimethylolpropane, glycerin, and pentaerythritol; and low molecular weight amino alcohol compounds such as monoethanolamine and diethanolamine.
These polyhydric alcohols may be used alone or in combination of two or more kinds.

Specific examples of secondary or tertiary amines include low molecular weight amine compounds such as hexamethylenediamine, xylylenediamine, and isophoronediamine.
These secondary or tertiary amines may be used alone or in combination of two or more kinds.

In addition, as the polyester polyol, for example, a lactone-based polyester polyol obtained by ring-opening polymerization of cyclic ester (lactone) monomers such as ε-caprolactone and γ-valerolactone using a low molecular weight alcohol compound and a low molecular weight amino alcohol compound as an initiator can be used.

Examples of polycarbonate polyols include those obtained by the dehydrochlorination reaction of low molecular weight alcohol compounds used in the synthesis of polyester polyols with phosgene; and those obtained by the transesterification reaction of these low molecular weight alcohol compounds with carbonates such as diethylene carbonate, dimethyl carbonate, diethyl carbonate, and diphenyl carbonate.

Examples of polyether polyols include polyoxyethylene polyols, polyoxypropylene polyols, polytetramethylene ether polyols, and polyoxyethylene polyoxypropylene polyols, which are obtained by ring-opening polymerization of alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide, and tetrahydrofuran, etc., using low molecular weight alcohol compounds, low molecular weight amine compounds, and low molecular weight amino alcohol compounds, and phenols, etc., used in the synthesis of polyester polyols, as initiators. Further examples include polyester ether polyols using the above-mentioned polyester polyols and polycarbonate polyols as initiators.

As the chain extender, a compound having two or more functional groups (such as amino groups and hydroxyl groups) capable of reacting with an isocyanate group in one molecule can be used.
Specific examples of chain extenders include diamine compounds such as ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, hexamethylenediamine, isophoronediamine, and 2-ethylaminoethylamine; polyamine compounds such as diethylenetriamine and triethylenetetramine; low molecular weight diol compounds such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, and triethylene glycol; aminoethylethanolamine, and aminopropylethanolamine.
These chain extenders may be used alone or in combination of two or more.

Examples of the reaction terminator include monoalkylamines such as n-propylamine and n-butylamine; dialkylamines such as di-n-butylamine; alkanolamines such as monoethanolamine and diethanolamine; and monoalcohols such as methanol and ethanol.
These reaction terminators may be used alone or in combination of two or more kinds.

The glass transition temperature of the urethane resin (A) is −60 to −20° C., preferably −58 to −25° C., and more preferably −55 to −30° C. When the glass transition temperature of the urethane resin (A) is equal to or higher than the lower limit, the blocking resistance, heat resistance, and shrinkability of the ink layer are improved. When the glass transition temperature of the urethane resin (A) is equal to or lower than the upper limit, the shrinkability of the ink layer and its adhesion to a substrate film (such as a plastic film described below) are improved.
The glass transition temperature of the urethane resin (A) is a value determined by differential scanning calorimetry (DSC) in accordance with the provisions of JIS K 7121: 2012. Specifically, the glass transition temperature is determined from the intersection of the baseline and the tangent to the endothermic curve in a curve (DSC curve) obtained by heating 10 mg of the urethane resin (A) from −100° C. to 160° C. at a rate of 20° C./min using a differential scanning calorimeter.

The weight average molecular weight of the urethane resin (A) is preferably 10,000 to 120,000, more preferably 20,000 to 110,000, and particularly preferably 30,000 to 100,000. When the weight average molecular weight of the urethane resin (A) is equal to or greater than the lower limit, the blocking resistance and heat resistance of the ink layer are improved. When the weight average molecular weight of the urethane resin (A) is equal to or less than the upper limit, the shrinkability of the ink layer is further improved. In addition, when the ink composition contains, for example, a pigment (G) described below, the pigment dispersibility is improved.
The weight average molecular weight of the urethane resin (A) is a value calculated in terms of standard polystyrene by gel permeation chromatography (GPC).

The amine value of the urethane resin (A) is preferably 0.1 to 5 mgKOH/g, more preferably 0.2 to 3 mgKOH/g, and particularly preferably 0.3 to 1 mgKOH/g. When the amine value of the polyurethane resin (A) is equal to or greater than the lower limit, the adhesion of the ink layer to the substrate film is improved. When the amine value of the urethane resin (A) is equal to or less than the upper limit, the printability of the ink composition and the blocking resistance of the ink layer are improved.
The amine value is the amount of potassium hydroxide, equivalent to hydrochloric acid, required to neutralize all basic nitrogen (primary, secondary and tertiary amines) contained in 1 g of a sample, expressed in milligrams.
The amine value of the urethane resin (A) is a value determined by neutralization titration using hydrochloric acid in accordance with the provisions of JIS K 7237:1995.

The storage modulus (E'; dynamic storage modulus) of the urethane resin (A) at a temperature of 100°C and a frequency of 11 Hz is preferably 0.1 to 10 MPa, more preferably 0.1 to 8 MPa, and particularly preferably 0.1 to 5 MPa. When the storage modulus of the urethane resin (A) is equal to or less than the above upper limit, the shrinkability of the ink layer and its adhesion to the base film are further improved.
The storage modulus of the urethane resin (A) is a value obtained by measuring the dynamic viscoelasticity of a dry film of the urethane resin (A) (a film-like sample having a film thickness of 20 μm) using a dynamic viscoelasticity measuring device at a temperature of 100° C. and a frequency of 11 Hz.

<(Meth)acrylic resin (B)>
The (meth)acrylic resin (B) is a (meth)acrylic acid ester-based polymer obtained by polymerizing a monomer component containing a (meth)acrylic acid ester as a polymerizable monomer, and contains a structural unit derived from a (meth)acrylic acid ester as a main structural unit.

Examples of the (meth)acrylic resin (B) include homopolymers of (meth)acrylic acid esters, copolymers of multiple types of (meth)acrylic acid esters, copolymers of (meth)acrylic acid esters and other polymerizable monomers copolymerizable with (meth)acrylic acid esters, urethane-modified resins or silicone-modified resins obtained by modifying these homopolymers or copolymers with urethane or silicone, etc. These are also collectively referred to as "acrylic resins".
These (meth)acrylic resins (B) may be used alone or in combination of two or more.

The (meth)acrylic acid ester is not particularly limited, and examples thereof include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; (meth)acrylic acid aralkyl esters such as benzyl (meth)acrylate; (meth)acrylic acid aryl esters such as phenyl (meth)acrylate and naphthyl (meth)acrylate; and (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate.
These (meth)acrylic acid esters may be used alone or in combination of two or more kinds.

The other polymerizable monomer is not particularly limited as long as it is copolymerizable with the (meth)acrylic acid ester, and examples thereof include styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, and derivatives thereof; unsaturated carboxylic acid-based monomers such as (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acrylamide, methacrylamide, acrylonitrile, and methacrylonitrile.
These other polymerizable monomers may be used alone or in combination of two or more kinds.

The acid value of the (meth)acrylic resin (B) is less than 10 mgKOH/g, preferably 9 mgKOH/g or less, more preferably 8 mgKOH/g or less. If the acid value of the (meth)acrylic resin (B) is less than the upper limit, the water resistance and hot water whitening resistance of the ink layer are improved.
Although there is no particular restriction on the lower limit of the acid value of the (meth)acrylic resin (B), for example, the acid value of the (meth)acrylic resin (B) is preferably 1 mgKOH/g or more.
The acid value is the amount of potassium hydroxide, expressed in milligrams, required to neutralize acid groups, such as carboxy groups, contained in 1 g of a sample.
The acid value of the (meth)acrylic resin (B) is a value measured in accordance with the neutralization titration method specified in JIS K 0070:1992.

The glass transition temperature of the (meth)acrylic resin (B) is preferably 5 to 100° C., more preferably 30 to 80° C., and particularly preferably 40 to 70° C. When the glass transition temperature of the (meth)acrylic resin (B) is equal to or higher than the lower limit, the heat resistance and shrinkability of the ink layer are further improved. When the glass transition temperature of the (meth)acrylic resin (B) is equal to or lower than the upper limit, the hot water whitening resistance and shrinkability of the ink layer are further improved.
The glass transition temperature of the (meth)acrylic resin (B) is a value determined by the same method as for the glass transition temperature of the urethane resin (A).

The weight average molecular weight of the (meth)acrylic resin (B) is preferably 10,000 to 150,000, more preferably 20,000 to 140,000, and particularly preferably 30,000 to 130,000. When the weight average molecular weight of the (meth)acrylic resin (B) is equal to or greater than the above lower limit, the heat resistance and blocking resistance of the ink layer are improved. When the weight average molecular weight of the (meth)acrylic resin (B) is equal to or less than the above upper limit, the shrinkability and adhesion of the ink layer to the substrate film are further improved.
The weight average molecular weight of the (meth)acrylic resin (B) is a value determined by the same method as for the weight average molecular weight of the urethane resin (A).

<Rosin Derivative (C)>
Examples of the rosin derivative (C) include rosin modified maleic acid resin, rosin modified fumaric acid resin, rosin modified phenol resin, rosin ester, hydrogenated rosin, polymerized rosin, and terpene phenol resin.
These rosin derivatives (C) may be used alone or in combination of two or more kinds.

The acid value of the rosin derivative (C) is 150 to 310 mgKOH/g, preferably 160 to 280 mgKOH/g, and more preferably 170 to 250 mgKOH/g. When the acid value of the rosin derivative (C) is equal to or higher than the lower limit, the alkali releasability of the ink layer is improved. When the acid value of the rosin derivative (C) is equal to or lower than the upper limit, the water resistance and hot water whitening resistance of the ink layer are improved.
The acid value of the rosin derivative (C) is a value determined by the same method as for the acid value of the (meth)acrylic resin (B).

The softening point of the rosin derivative (C) is preferably 80 to 200° C., more preferably 90 to 190° C., and particularly preferably 100 to 180° C. When the softening point of the rosin derivative (C) is equal to or higher than the lower limit, the blocking resistance, heat resistance, and shrink suitability of the ink layer are improved. When the softening point of the rosin derivative (C) is equal to or lower than the upper limit, the adhesion of the ink layer to the substrate film is improved.
The softening point of the rosin derivative (C) is a value determined by the ring and ball method in accordance with JIS K 5601-2-2:1999.

<(Meth)acrylic resin (D)>
When the ink composition further contains a (meth)acrylic resin (D) in addition to the above-mentioned urethane resin (A), (meth)acrylic resin (B), and rosin derivative (C), the alkali releasability of the ink layer is further improved.
The (meth)acrylic resin (D) is a (meth)acrylic acid ester-based polymer obtained by polymerizing a monomer component containing a (meth)acrylic acid ester as a polymerizable monomer, and contains a structural unit derived from a (meth)acrylic acid ester as a main structural unit.

Examples of the (meth)acrylic resin (D) include homopolymers of (meth)acrylic acid esters, copolymers of multiple types of (meth)acrylic acid esters, copolymers of (meth)acrylic acid esters and other polymerizable monomers copolymerizable with (meth)acrylic acid esters, urethane-modified resins or silicone-modified resins obtained by modifying these homopolymers or copolymers with urethane or silicone, etc. These are also collectively referred to as "acrylic resins".
These (meth)acrylic resins (D) may be used alone or in combination of two or more.

Examples of the (meth)acrylic acid ester include the (meth)acrylic acid esters exemplified above in the description of the (meth)acrylic resin (B).
Examples of the other polymerizable monomer include the other polymerizable monomers exemplified above in the description of the (meth)acrylic resin (B).
The (meth)acrylic acid ester and the other polymerizable monomer may each be used alone or in combination of two or more kinds.

The acid value of the (meth)acrylic resin (D) is 40 to 100 mgKOH/g, preferably 50 to 95 mgKOH/g, and more preferably 60 to 90 mgKOH/g. When the acid value of the (meth)acrylic resin (D) is equal to or greater than the lower limit, the alkali release property of the ink layer is further improved. When the content of the (meth)acrylic resin (D) is equal to or less than the upper limit, the water resistance and hot water whitening resistance of the ink layer are further improved.
The acid value of the (meth)acrylic resin (D) is a value determined by the same method as for the acid value of the (meth)acrylic resin (B).
In addition, since the acid value of the (meth)acrylic resin (D) is higher than the acid value of the (meth)acrylic resin (B), in the present invention, the (meth)acrylic resin (B) is also referred to as the "low acid value (meth)acrylic resin (B)" and the (meth)acrylic resin (D) is also referred to as the "high acid value (meth)acrylic resin (D)."

The glass transition temperature of the (meth)acrylic resin (D) is preferably 5 to 100° C., more preferably 30 to 80° C., and particularly preferably 40 to 70° C. When the glass transition temperature of the (meth)acrylic resin (D) is equal to or higher than the lower limit, the blocking resistance, heat resistance, and adhesion to the base film of the ink layer are improved. When the glass transition temperature of the (meth)acrylic resin (D) is equal to or lower than the upper limit, the shrink suitability of the ink layer is further improved.
The glass transition temperature of the (meth)acrylic resin (D) is a value determined by the same method as for the glass transition temperature of the urethane resin (A).

The weight average molecular weight of the (meth)acrylic resin (D) is preferably 10,000 to 100,000, more preferably 15,000 to 90,000, and particularly preferably 20,000 to 80,000. When the weight average molecular weight of the (meth)acrylic resin (D) is equal to or greater than the above lower limit, the water resistance and heat resistance of the ink layer are improved. When the weight average molecular weight of the (meth)acrylic resin (D) is equal to or less than the above upper limit, the compatibility of the (meth)acrylic resin (D) with the urethane resin (A), the (meth)acrylic resin (B), and the rosin derivative (C) is improved.
The weight average molecular weight of the (meth)acrylic resin (D) is a value determined by the same method as for the weight average molecular weight of the urethane resin (A).

<Cellulose resin (E)>
When the ink composition further contains a cellulose resin (E) in addition to the above-mentioned urethane resin (A), (meth)acrylic resin (B), and rosin derivative (C), the blocking resistance and shrink suitability of the ink layer are further improved.
As the cellulose resin (E), cellulose, cellulose derivatives in which some of the hydroxyl groups of cellulose are substituted with other groups, etc. can be used. Among these, cellulose derivatives are preferred.

Examples of the cellulose resin (E) include nitrocellulose (nitro group substituted products); lower acyl group substituted products such as cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate; lower alkyl group substituted products such as methyl cellulose and ethyl cellulose; aralkyl group substituted products such as benzyl cellulose; and cellulose derivatives having a hydroxyalkyl group such as hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxymethylpropyl cellulose.
These cellulose resins (E) may be used alone or in combination of two or more kinds.

<Silica (F)>
When the ink composition further contains silica (F) in addition to the above-mentioned urethane resin (A), (meth)acrylic resin (B), and rosin derivative (C), the blocking resistance of the ink layer is improved.
Silica (F) may be a natural product or a synthetic product.
Examples of synthetic products include silica obtained by dry processes such as the combustion method and the arc method; and silica obtained by wet processes such as the precipitation method and the gel method.
The silica (F) may be crystalline or non-crystalline.
The silica (F) may be aqueous or hydrophilic.
These silicas (F) may be used alone or in combination of two or more.

The average particle size of silica (F) is preferably 0.01 to 200 μm, more preferably 0.1 to 150 μm, and particularly preferably 1 to 100 μm. When the average particle size of silica (F) is equal to or greater than the lower limit, the blocking resistance of the ink layer is improved. When the average particle size of silica (F) is equal to or less than the upper limit, the storage stability, transparency, and printability of the ink composition are improved.
The average particle size of silica (F) is a particle size at a volume-based cumulative frequency of 50% (median size: D50) calculated from the volume-based particle size distribution measured by a laser diffraction/scattering method, and is also referred to as the volume-based average particle size.

<Optional ingredients>
Examples of the optional components include an organic solvent, a pigment (G), and other additives.
These optional components may be used alone or in combination of two or more.

Examples of the organic solvent include aromatic organic solvents such as toluene and xylene; aliphatic hydrocarbon organic solvents such as cyclohexane and methylcyclohexane; ketone organic solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester organic solvents such as ethyl acetate, n-propyl acetate, isopropyl acetate, and isobutyl acetate; alcohol organic solvents such as methanol, ethanol, n-propanol, isopropanol, and n-butanol; and glycol ether organic solvents such as ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether.
These organic solvents may be used alone or in combination of two or more.

Among the above, the organic solvent is preferably an organic solvent that does not substantially contain aromatic organic solvents such as toluene or xylene (a non-toluene organic solvent or a non-xylene organic solvent). That is, from an environmental standpoint, it is preferable that the ink composition is a non-toluene type or a non-xylene type ink composition that does not substantially contain toluene or xylene.
Here, "substantially not contained" means that, except for those that are unintentionally contained, they are not actively blended into the ink composition.

The organic solvent preferably contains at least one selected from the group consisting of ester-based organic solvents, ketone-based organic solvents, and alcohol-based organic solvents.
The content of the ester-based organic solvent in the organic solvent is preferably 5 to 80 mass % relative to the total mass of the organic solvent. The content of the ketone-based organic solvent in the organic solvent is preferably 5 to 90 mass % relative to the total mass of the organic solvent. The content of the alcohol-based organic solvent in the organic solvent is preferably 0 to 50 mass % relative to the total mass of the organic solvent.

The ink composition may contain the pigment (G), or may substantially not contain the pigment (G).
An ink composition containing the pigment (G) is also particularly called a "color ink composition." An ink composition that does not substantially contain the pigment (G) is also particularly called a "colorless ink composition" or "medium."

Examples of the pigment (G) include extender pigments, inorganic pigments, and organic pigments.
Specific examples of the extender pigment include silica, barium sulfate, kaolin, clay, calcium carbonate, and magnesium carbonate.
Specific examples of inorganic pigments include white pigments such as titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, and silica; black pigments such as carbon black and iron black; and inorganic pigments of various colors such as aluminum particles, mica, bronze powder, chrome vermilion, yellow lead, cadmium yellow, cadmium red, ultramarine, Prussian blue, red iron oxide, yellow iron oxide, and zinc oxide.
Specific examples of organic pigments include organic pigments of various types, such as soluble azos, insoluble azos, azos, phthalocyanines, halogenated phthalocyanines, anthraquinones, anthanthrones, dianthraquinonyls, anthrapyrimidines, perylenes, perinones, quinacridones, thioindigo, dioxazines, isoindolinones, quinophthalones, azomethine azos, flavanthrones, diketopyrrolopyrroles, isoindolines, and indanthrones.
These pigments (G) may be used alone or in combination of two or more kinds.

Examples of the additives include pigment derivatives, lubricants, release agents, anti-settling agents, UV absorbers, antioxidants, antistatic agents, leveling agents, thickeners, defoamers, plasticizers, dispersants, stabilizers, waxes, and the like.
These additives may be used alone or in combination of two or more.

<Content>
The content of the urethane resin (A) is preferably 2 to 10 mass %, more preferably 2.3 to 9.5 mass %, and particularly preferably 2.5 to 9 mass %, based on the total mass of the ink composition, calculated as solid content. If the content of the urethane resin (A) is equal to or greater than the lower limit, the ink layer's shrinkability and adhesion to the substrate film are further improved. If the content of the urethane resin (A) is equal to or less than the upper limit, the ink layer's hot water whitening resistance, blocking resistance, and alkali release properties are further improved.

The content of (meth)acrylic resin (B) is preferably 0.5 to 5 mass %, more preferably 0.6 to 4 mass %, and particularly preferably 0.7 to 3 mass %, based on the total mass of the ink composition, calculated as solid content. If the content of (meth)acrylic resin (B) is equal to or greater than the lower limit, the affinity between the ink layer and the protective layer described below is improved, and the adhesion between the ink layer and the protective layer is improved, resulting in improved resistance to hot water whitening of the ink layer. If the content of (meth)acrylic resin (B) is equal to or less than the upper limit, the storage stability of the ink composition is improved. In addition, the alkali release property, shrink suitability, and adhesion to the base film of the ink layer are improved.

The content of the rosin derivative (C), calculated as solid content, is preferably 2 to 6 mass %, more preferably 2.5 to 5.5 mass %, and particularly preferably 3 to 5 mass %, of the total mass of the ink composition. If the content of the rosin derivative (C) is equal to or greater than the lower limit, the alkali release properties of the ink layer are further improved. If the content of the rosin derivative (C) is equal to or less than the upper limit, the water resistance, hot water whitening resistance, blocking resistance, shrink suitability, and adhesion to the base film of the ink layer are further improved.

The total content of the urethane resin (A), the (meth)acrylic resin (B), and the rosin derivative (C), calculated as solid content, is preferably 5 to 15% by mass, more preferably 6 to 14.5% by mass, and particularly preferably 7 to 14% by mass, based on the total mass of the ink composition. If the total content of the urethane resin (A), the (meth)acrylic resin (B), and the rosin derivative (C) is equal to or greater than the lower limit, the storage stability of the ink composition is improved. Furthermore, if the ink composition contains a pigment (G), the pigment dispersibility is improved. In addition, the shrinkability of the ink layer and its adhesion to the substrate film are further improved. If the total content of the urethane resin (A), the (meth)acrylic resin (B), and the rosin derivative (C) is equal to or less than the upper limit, the heat resistance, blocking resistance, and hiding power of the ink layer are improved.

The content of (meth)acrylic resin (D) is preferably 0.1 to 2 mass%, more preferably 0.2 to 1.5 mass%, and particularly preferably 0.3 to 1 mass%, based on the total mass of the ink composition, calculated as solid content. If the content of (meth)acrylic resin (D) is equal to or greater than the lower limit, the alkali release properties of the ink layer are improved. If the content of (meth)acrylic resin (D) is equal to or less than the upper limit, the compatibility of the urethane resin (A), the (meth)acrylic resin (B), and the rosin derivative (C) with the (meth)acrylic resin (D) is improved. In addition, the water resistance of the ink layer is improved.

The content of cellulose resin (E) is preferably 0.5 to 10 mass %, more preferably 1 to 8 mass %, and particularly preferably 1.5 to 6 mass %, calculated as solid content, relative to the total mass of the ink composition. If the content of cellulose resin (E) is equal to or greater than the lower limit, the blocking resistance and shrink suitability of the ink layer are further improved. If the content of cellulose resin (E) is equal to or less than the upper limit, the alkali release properties of the ink layer are further improved.

The content of silica (F) is preferably 0.1 to 2 mass%, more preferably 0.1 to 1 mass%, and particularly preferably 0.1 to 0.5 mass%, based on the total mass of the ink composition. If the content of silica (F) is equal to or greater than the lower limit, the blocking resistance of the ink layer is further improved. If the content of silica (F) is equal to or less than the upper limit, the transparency and printability of the ink composition are improved.

The content of the organic solvent is preferably 10 to 95% by mass, more preferably 20 to 90% by mass, and particularly preferably 30 to 85% by mass, based on the total mass of the ink composition. If the content of the organic solvent is equal to or greater than the lower limit, the fluidity of the ink composition is improved. If the content of the organic solvent is equal to or less than the upper limit, the drying property of the ink layer is improved.

The content of the pigment (G) is not particularly limited as long as it is set to an amount sufficient to ensure the coloring power, etc., of the ink composition, but is preferably, for example, 1 to 80% by mass relative to the total mass of the solids in the ink composition.

<Production Method>
The ink composition of the present embodiment can be obtained by dissolving or dispersing, for example, the urethane resin (A), the (meth)acrylic resin (B), the rosin derivative (C), and, as necessary, one or more of the (meth)acrylic resin (D), the cellulose resin (E), the silica (F), and any optional components other than the organic solvent, in an organic solvent so that each component is present in a desired amount.
The method for mixing the components is not particularly limited, and the components can be mixed by various methods.

<Action and effect>
The ink composition of the present embodiment described above contains the above-mentioned urethane resin (A), (meth)acrylic resin (B), and rosin derivative (C), and is therefore capable of forming an ink layer that is excellent in hot water whitening resistance, shrink suitability, and alkali release property.

As described above, even if the ink layer is in contact with the protective layer and the surface of the ink layer is protected by the protective layer and is not exposed, if the adhesion between the ink layer and the protective layer is insufficient, whitening may occur at the interface between them. In particular, if the ink layer is in contact with a layer containing a (meth)acrylic resin and the adhesion between the ink layer and the layer containing a (meth)acrylic resin is insufficient, whitening is likely to occur at the interface between them.
However, the ink layer formed from the ink composition of the present embodiment has excellent adhesion to a protective layer, particularly to a layer containing a (meth)acrylic resin, and therefore can suppress whitening when immersed in hot water not only when the surface of the ink layer is exposed, but also when the ink layer is provided in contact with a protective layer, particularly to a layer containing a (meth)acrylic resin.

<Applications of ink composition>
The ink composition of the present embodiment is suitable as an ink for shrink labels, but is particularly suitable as an ink for printing on the surface of a base film such as a plastic film (if an optional layer is formed on the surface of the base film, on the surface of this optional layer) by gravure printing or flexographic printing. In particular, it is suitable as an ink for printing on the surface of a base film or the surface of the optional layer by gravure printing. In other words, the ink composition of the present embodiment is suitable for gravure printing.
In particular, if the ink composition contains the pigment (G), it can be used as a color ink. If the ink composition does not substantially contain the pigment (G), it can be used as a colorless ink or medium.
The ink composition may be used as it is as ink, or a dilution obtained by diluting the ink composition with an organic solvent or the like may be used as ink.

[Laminate]
An example of a laminate according to an embodiment of the present invention is shown in Fig. 1. Note that the dimensional ratio in Fig. 1 is different from the actual one for the sake of convenience of explanation.
The laminate 10 in FIG. 1 is a printed matter comprising a plastic film 11 which is a base film, and an ink layer 12 provided on one surface of the plastic film 11 .
When the laminate 10 is attached to an object as a shrink label, the plastic film 11 is attached on the outer side of the ink layer 12, that is, the ink layer 12 is attached on the inner side (the side in contact with the object).

<Plastic film>
Examples of the plastic film 11 include polyester films such as polyethylene terephthalate (PET), amorphous polyethylene terephthalate (A-PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polylactic acid; polyolefin films such as polyethylene (PE) and polypropylene (PP); polystyrene (PS) films; and polyvinyl chloride films.
These plastic films 11 may be used alone or in combination of two or more kinds.

The plastic film 11 may have a single layer structure or a laminated structure. That is, the plastic film 11 may be a single layer film or a laminated film. When the plastic film 11 is a laminated film, it may be configured with two or more films of the same type laminated together, or with two or more films of different types laminated together.

The thickness of the plastic film 11 is preferably 10 to 80 μm, more preferably 15 to 70 μm, and particularly preferably 20 to 60 μm.

<Ink layer>
In the illustrated laminate 10 , the ink layer 12 is provided on one surface of the plastic film 11 .
The ink layer 12 is a layer formed using the ink composition of the present invention described above, and is also called an ink coating film.
The thickness of the ink layer 12 is preferably from 0.1 to 5 μm, more preferably from 0.3 to 4 μm, and particularly preferably from 0.5 to 3 μm.

<Method of manufacturing laminate>
The method for producing the laminate 10 of this embodiment includes a step of forming an ink layer 12 on one surface of a plastic film 11 using the ink composition of this embodiment.
In the method for producing the laminate 10 of this embodiment, for example, the ink composition of the present invention is applied onto one surface of a plastic film 11 and dried to form an ink layer 12 .
The ink composition of the present invention may be applied to one surface of the plastic film 11 and dried to form the ink layer 12, and then the ink composition of the present invention may be further applied (overcoated).

The method for applying the ink composition is not particularly limited, and known application methods such as gravure printing, flexographic printing, brush application, gravure coater method, die coater method, bar coater method, spray coating method, flow coating method, dip coating method, spin coating method, and curtain coating method can be used. Among these, gravure printing and flexographic printing are suitable because they have excellent drying properties and are compatible with high-speed printing. Among these, gravure printing is particularly preferred because of its excellent tone reproducibility.

The drying method is not particularly limited as long as it can remove the organic solvent contained in the ink composition coated on one side of the plastic film 11, and may be natural drying or forced drying such as reduced pressure drying, pressurized drying, heat drying, or air drying.
When drying is performed by heating, the drying temperature is preferably from 30 to 60°C, more preferably from 35 to 55°C.

<Action and effect>
The laminate of the present embodiment described above has an ink layer formed on one side of the plastic film using the ink composition of the present invention, and therefore has excellent shrink suitability, and the ink layer is less likely to whiten even when immersed in warm water. Furthermore, since the ink layer has excellent alkali release properties, when reusing a used laminate, the ink layer can be easily removed from the plastic film, and deterioration of the hue and physical properties of the recycled plastic film can be suppressed.

<Applications>
The laminate 10 of the present embodiment can be used as various types of labels, such as plastic labels to be attached to containers used for storing beverages, foods such as prepared dishes and bento boxes, daily necessities such as cosmetics, and the like, and is particularly suitable as a shrink label.

<Other embodiments>
The laminate is not limited to the above-described embodiment.
For example, in the case of the laminate 10 shown in Fig. 1, the ink layer 12 is provided over the entirety of one surface of the plastic film 11, but the ink layer 12 may also be provided over a portion of one surface of the plastic film 11. In this case, another layer may be provided in the region of one surface of the plastic film 11 where the ink layer 12 is not provided.

In addition, a protective layer may be provided on at least one of the surface of the ink layer 12 opposite the plastic film 11 and the other side of the plastic film 11 (i.e., the surface opposite the ink layer 12).
Furthermore, an optional layer (also called an “intermediate layer”) may be provided between the plastic film 11 and the ink layer 12 .

An example of the protective layer is a layer formed from a varnish composition.
The varnish composition is not particularly limited and any known composition can be used. One example is a composition containing a binder resin and a solvent.
Examples of the binder resin include (meth)acrylic resin, urethane resin, polyester resin, polyamide resin, vinyl chloride-vinyl acetate copolymer resin, cellulose resin, epoxy resin, and olefin resin. Among these, (meth)acrylic resin is preferred. Examples of the (meth)acrylic resin include homopolymers of (meth)acrylic acid esters; copolymers of multiple (meth)acrylic acid esters; copolymers of (meth)acrylic acid esters and other polymerizable monomers copolymerizable with (meth)acrylic acid esters; and urethane-modified or silicone-modified resins obtained by modifying these homopolymers or copolymers with urethane or silicone. In addition, a layer formed from a varnish composition containing a (meth)acrylic resin is also referred to as a "layer containing a (meth)acrylic resin" or an "acrylic protective layer".
Examples of the solvent include water, organic solvents, mixed solvents of water and organic solvents, etc. Examples of the organic solvent include the organic solvents exemplified above in the description of the ink composition of the present invention.

[Packaging materials]
The laminate of the present invention can be used, for example, as a packaging material. Specifically, the laminate of the present invention is wrapped around a container or the like used for storing beverages, foods, daily necessities, etc., and then the laminate is heat-shrunk by heating and attached to the container, thereby forming a packaging material for soft packaging (soft packaging package) for beverages, foods, daily necessities, etc.
Here, "soft packaging" refers to packaging material made of a flexible material, i.e., a flexible package.
The packaging material of the present invention is used for packaging, for example, beverages, foods, medicines, quasi-drugs, cosmetics, detergents, chemicals, and the like.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.
Examples 15 to 20 are reference examples.

[Ingredients used]
As the urethane resin (A), the compound shown below was used.
A-1: Sanprene, manufactured by Sanyo Chemical Industries, Ltd.; glass transition temperature: −50° C.
A-2: Sanprene, manufactured by Sanyo Chemical Industries, Ltd.; glass transition temperature: −38° C.
A-3: Manufactured by Pelnox Corporation, product name "Pelurethane", glass transition temperature: -70°C.
A-4: Sanretan, manufactured by Sanyo Chemical Industries, Ltd.; glass transition temperature: 15° C.

As the (meth)acrylic resin (B), the compound shown below was used.
B-1: Taisei Fine Chemical Co., Ltd., trade name "Acrit", acid value: 1.3 mg KOH/g, glass transition temperature: 66°C.
B-2: Manufactured by Mitsubishi Chemical Corporation, trade name "Dianal", acid value: 7.8 mg KOH / g, glass transition temperature: 48 ° C.
B-3: Taisei Fine Chemical Co., Ltd., trade name "Acrit", acid value: 2.5 mg KOH/g, glass transition temperature: 24°C.
B-4: Mitsubishi Chemical Corporation, trade name "Dianal", acid value: 3.3 mg KOH / g, glass transition temperature: 97 ° C.
B-5: Taisei Fine Chemical Co., Ltd., trade name "Acrit", acid value: 26.5 mg KOH/g, glass transition temperature: 37°C.
B-6: Taisei Fine Chemical Co., Ltd., trade name "Acrit", acid value: 100 mg KOH/g, glass transition temperature: 80°C.
B-7: Taisei Fine Chemical Co., Ltd., trade name "Acrit", acid value: 12.9 mg KOH/g, glass transition temperature: 67°C.

As the rosin derivative (C), the compound shown below was used.
C-1: Harima Chemical Group Co., Ltd., product name "Halima", acid value: 190 mg KOH/g, softening point: 160°C.
C-2: Arakawa Chemical Industries, Ltd., trade name "Marquid", acid value: 305 mg KOH/g, softening point: 150°C.
C-3: Arakawa Chemical Industries, Ltd., trade name "Marquid", acid value: 100 mg KOH/g, softening point: 100°C.
C-4: Harima Chemical Group Co., Ltd., trade name "Harie Star", acid value: 8 mg KOH / g, softening point: 80 ° C.
C-5: Arakawa Chemical Industries, Ltd., trade name "Pine Crystal", acid value: 320 mg KOH/g, softening point: 120°C.

As the (meth)acrylic resin (D), the compound shown below was used.
D-1: Manufactured by BASF Japan Ltd., product name "JONCRYL JDX-C3000A", acid value: 85 mg KOH / g, glass transition temperature: 65 ° C.

As the cellulose resin (E), the compound shown below was used.
E-1: Nitrocellulose (manufactured by Kimia Corporation, product name "RS1/16", type and viscosity symbol: H1/8).

As silica (F), the compound shown below was used.
F-1: Tosoh Silica Corporation, product name "Nipsil E220A", average particle size: 1.5 μm.

As the pigment (G), the compound shown below was used.
G-1: Product name "Titanix JR-701", manufactured by Teika Corporation.
G-2: Manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., product name "Seika First Yellow 2270".
G-3: Product name "Seika First Carmine 3870" manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.
G-4: Product name "Leonor Blue FG7351" manufactured by Toyo Color Co., Ltd.
G-5: Manufactured by Columbia Chemical Company, trade name "Laven 450".

A mixed solvent of n-propyl acetate: methyl ethyl ketone: isopropanol = 2:2:1 (mass ratio) was used as the organic solvent.

As optional components other than the pigment (G) and the organic solvent, the compounds shown below were used.
Wax: Mitsui Chemicals, Inc., product name "HIWAX 320MP".
Defoaming agent: BYK Corporation, product name "BYK-1752".

[Evaluation method]
<Evaluation of Adhesion>
After cellophane tape (manufactured by Nichiban Co., Ltd.) was applied to a portion of the surface of the ink layer of the laminate (I), the cellophane tape was quickly peeled off, and the condition of the ink layer remaining on the base film (plastic film) was visually inspected, and the adhesion of the ink layer to the base film (plastic film) was evaluated according to the following evaluation criteria.
5: The ratio of the area of the peeled ink layer to the area of the cellophane tape adhered thereto is less than 10%.
4: The ratio of the area of the peeled ink layer to the adhesive area of the cellophane tape is 10% or more and less than 20%.
3: The ratio of the area of the peeled ink layer to the adhesive area of the cellophane tape is 20% or more and less than 50%.
2: The ratio of the area of the peeled ink layer to the adhesive area of the cellophane tape is 50% or more and less than 80%.
1: The ratio of the area of the peeled ink layer to the area of the cellophane tape was 80% or more.

<Evaluation of hot water whitening resistance>
The laminate (II) was immersed in water (warm water) at 40° C. in a closed container and allowed to stand for 24 hours. The degree of whitening after leaving was visually confirmed, and the resistance to hot water whitening was evaluated according to the following evaluation criteria.
5: Almost no whitening was observed compared with the laminate (II) before immersion in warm water.
4: Slight whitening compared with the laminate (II) before immersion in warm water.
3: Slight whitening compared with the laminate (II) before immersion in warm water.
2: Compared with the laminate (II) before immersion in warm water, there is obvious whitening.
1: Significant whitening occurs as compared with the laminate (II) before immersion in warm water.

<Evaluation of shrink suitability>
A plain, unprinted heat-shrinkable PET film (manufactured by Mitsubishi Chemical Corporation, product name "Hishipet LX-21S", thickness: 40 μm) was cut into 1 cm wide strips. One end of the cut film was fixed to the mouth of a mayonnaise bottle, and the other end was fixed to the bottom of the mayonnaise bottle with cellophane tape (manufactured by Nichiban Co., Ltd.). Following this procedure, strips of film were fixed to four separate locations per mayonnaise bottle.
Next, the laminate (I) was formed into a cylindrical shape using a stapler with the ink layer facing inward, and placed over the mayonnaise bottle with the above-mentioned strip-shaped film fixed thereto. The laminate was then immersed in 85°C water for 20 seconds to cause thermal shrinkage, and then immediately cooled. The ink layer was visually inspected for cracks at the points that had been in contact with the strip-shaped film, and the shrink suitability was evaluated according to the following evaluation criteria.
5: No cracks were observed in the ink layer at any of the four points in contact with the rectangular film.
4: A crack was observed in the ink layer at one point where the strip of film was in contact.
3: Cracking of the ink layer was observed in two places where it came into contact with the rectangular film.
2: Cracking of the ink layer was observed in three places where the strip-shaped film was in contact.
1: Cracking of the ink layer was observed in all four places that came into contact with the rectangular film.

<Evaluation of alkali release properties>
The laminate (I) was cut into a piece of 3 cm x 3 cm. The cut laminate (I) was immersed in an aqueous sodium hydroxide solution (concentration of sodium hydroxide: 1.5% by mass) at 80°C and stirred for 10 minutes. The laminate (I) was then removed from the aqueous sodium hydroxide solution and washed with water. The state of the ink layer was then visually inspected, and the alkali release property was evaluated according to the following evaluation criteria.
5: The ratio of the area of the ink layer from which the ink has detached to the total area of the ink layer is 100%.
4: The ratio of the area of the detached ink layer to the total area of the ink layer is 80% or more and less than 100%.
3: The ratio of the area of the ink layer from which the ink has detached to the total area of the ink layer is 50% or more and less than 80%.
2: The ratio of the area of the detached ink layer to the total area of the ink layer is 20% or more and less than 50%.
1: The ratio of the area of the ink layer from which the ink has detached to the total area of the ink layer is less than 20%.

<Evaluation of Blocking Resistance>
Immediately after production, two sheets of the laminate (I) were overlapped so that the surface of the ink layer side (printed surface) of the laminate (I) was in contact with the surface of the plastic film (heat-shrinkable PET film) side (non-printed surface) of the laminate (I), and a load of 7 kg/ ^cm2 was applied and stored for 20 hours in a thermostatic chamber at 25° C. Thereafter, the two sheets of the laminate (I) were peeled away from each other, and the blocking resistance was evaluated according to the evaluation criteria shown below.
5: The ratio of the area of the ink layer that has transferred to the non-printed surface to the total area of the ink layer is less than 10%.
4: The ratio of the area of the ink layer that has transferred to the non-printed surface to the total area of the ink layer is 10% or more and less than 20%.
3: The ratio of the area of the ink layer that has transferred to the non-printed surface to the total area of the ink layer is 20% or more and less than 50%.
2: The ratio of the area of the ink layer that has transferred to the non-printed surface to the total area of the ink layer is 50% or more and less than 80%.
1: The ratio of the area of the ink layer that has transferred to the non-printed surface to the total area of the ink layer is 80% or more.

[Examples 1 to 23, Comparative Examples 1 to 9]
<Preparation of Ink Composition>
According to the composition shown in the table, the urethane resin (A), the (meth)acrylic resin (B), the rosin derivative (C), the (meth)acrylic resin (D), the cellulose resin (E), the silica (F), the pigment (G), the wax, the defoaming agent, and the organic solvent were mixed, and the resulting mixture was kneaded with a paint shaker to obtain an ink composition.

<Preparation of Laminate>
(Preparation of Laminate (I))
The ink composition was diluted with a mixed solvent (n-propyl acetate:methyl ethyl ketone:isopropanol=2:2:1 (mass ratio)) to prepare a diluted solution so that the viscosity at 25°C, as measured using a Zahn cup #3, would be 16 seconds.
As the base film (plastic film), a heat-shrinkable PET film (manufactured by Mitsubishi Chemical Corporation, product name "Hishipet LX-21S", thickness: 40 μm) having one side subjected to a corona discharge treatment was used.
Using a gravure printing machine equipped with a Helio 175 lines/inch gravure engraving plate (manufactured by Matsuo Sangyo Co., Ltd., product name "K Printing Proofer"), the diluted solution was printed on the treated surface of the heat-shrinkable PET film, and the resulting film was dried at 20°C for 5 minutes to form an ink layer, thereby obtaining a laminate (I) which was a printed matter in which the ink layer was laminated on the heat-shrinkable PET film.
The obtained laminate (I) was evaluated for adhesion, shrinkability, alkali release property, and blocking resistance. The results are shown in Tables 1 to 4.

(Preparation of Laminate (II))
The ink composition was diluted with a mixed solvent (n-propyl acetate:methyl ethyl ketone:isopropanol=2:2:1 (mass ratio)) to prepare a diluted solution so that the viscosity at 25°C, as measured using a Zahn cup #3, would be 16 seconds.
As the base film (plastic film), a heat-shrinkable PET film (manufactured by Mitsubishi Chemical Corporation, product name "Hishipet LX-21S", thickness: 40 μm) having one side subjected to a corona discharge treatment was used.
A (meth)acrylic resin (manufactured by Taisei Fine Chemical Co., Ltd., product name "Acrylate", glass transition temperature: 66°C, acid value: 1.3 mgKOH/g) previously diluted with an organic solvent to an appropriate viscosity was applied to the treated surface of the heat-shrinkable PET film, and dried at 20°C for 5 minutes to form a layer containing the (meth)acrylic resin.
Next, using a gravure printing machine equipped with a Helio 175 line/inch gravure engraving plate (manufactured by Matsuo Sangyo Co., Ltd., product name "K Printing Proofer"), the diluted solution was printed on the layer containing the (meth)acrylic resin, and dried at 20°C for 5 minutes to form an ink layer, thereby obtaining a laminate (II) which is a printed matter in which a layer containing the (meth)acrylic resin and an ink layer are laminated in this order on a heat-shrinkable PET film.
The obtained laminate (II) was evaluated for resistance to whitening in hot water, and the results are shown in Tables 1 to 4.

The amounts of each component other than the organic solvent in the table are calculated as solids. A blank space in the table means that the component is not included (amount: 0% by mass). The "balance" in the table is the total amount of all organic solvents included in the ink composition, adjusted so that the total amount (% by mass) of all components included in the ink composition is 100% by mass.

As is clear from the results in Tables 1 to 4, the ink layers obtained from the ink compositions obtained in the respective Examples were excellent in hot water whitening resistance, shrinkability, and alkali release properties. They also had excellent adhesion to plastic films and blocking resistance.
The hot water whitening resistance was evaluated using the laminate (II), but a similar tendency was observed even when a laminate in which an ink layer and a layer containing a (meth)acrylic resin were laminated in that order on a heat-shrinkable PET film was used.

On the other hand, as is clear from the results in Table 4, the ink layer formed from the ink composition obtained in Comparative Example 1 using the urethane resin (A-3) having a glass transition temperature of -70°C was poor in shrinkability and blocking resistance.
The ink layer formed by the ink composition obtained in Comparative Example 2 using the urethane resin (A-4) having a glass transition temperature of 15° C. was poor in shrinkability and adhesion to the substrate film.
The ink layer formed from the ink composition obtained in Comparative Example 3 using the (meth)acrylic resin (B-5) having an acid value of 26.5 mgKOH/g was poor in hot water whitening resistance.
The ink layer formed by the ink composition obtained in Comparative Example 4 using the (meth)acrylic resin (B-6) having an acid value of 100 mgKOH/g was poor in hot water whitening resistance and shrink suitability.
The ink layer formed from the ink composition obtained in Comparative Example 5 using the (meth)acrylic resin (B-7) having an acid value of 12.9 mgKOH/g was poor in hot water whitening resistance.
The ink layer formed from the ink composition obtained in Comparative Example 6, which used the rosin derivative (C-3) having an acid value of 100 mgKOH/g, was poor in alkali releasability.
The ink layer formed from the ink composition obtained in Comparative Example 7, which used the rosin derivative (C-4) having an acid value of 8 mgKOH/g, was poor in alkali releasability.
The ink layer formed from the ink composition obtained in Comparative Example 8, which used the rosin derivative (C-5) having an acid value of 320 mgKOH/g, was poor in hot water whitening resistance.
The ink layer formed from the ink composition obtained in Comparative Example 9, which did not contain the rosin derivative (C), was poor in alkali releasability.

[Application example]
The ink composition prepared in Example 5 was diluted with a mixed solvent (n-propyl acetate:methyl ethyl ketone:isopropanol=2:2:1 (mass ratio)) so that the viscosity at 25°C, measured using a Zahn cup #3, would be 16 seconds, to prepare a diluted solution (indigo ink).
Separately, the ink composition prepared in Example 1 was diluted with a mixed solvent (n-propyl acetate:methyl ethyl ketone:isopropanol=2:2:1 (mass ratio)) so that the viscosity at 25°C, measured using a Zahn cup #3, would be 16 seconds, to prepare a diluted solution (white ink).
As the base film (plastic film), a heat-shrinkable PET film (manufactured by Mitsubishi Chemical Corporation, product name "Hishipet LX-21S", thickness: 40 μm) having one side subjected to a corona discharge treatment was used.
Using a gravure printing machine equipped with a Helio 175 lines/inch gravure engraving plate (manufactured by Matsuo Sangyo Co., Ltd., product name "K Printing Proofer"), indigo ink was printed on the treated surface of the heat-shrinkable PET film and dried at 40°C for 5 seconds to form a first ink layer.
Next, white ink was printed on the first ink layer using a gravure printing machine equipped with a Helio 175 lines/inch gravure engraving plate (manufactured by Matsuo Sangyo Co., Ltd., product name "K Printing Proofer") and dried at 40°C for 5 seconds to form a second ink layer.
Next, a (meth)acrylic resin (manufactured by Taisei Fine Chemical Co., Ltd., product name "Acrylate", glass transition temperature: 66°C, acid value: 1.3 mgKOH/g) previously diluted with an organic solvent to an appropriate viscosity was applied onto the second ink layer and dried at 40°C for 5 seconds to form a layer containing a (meth)acrylic resin, thereby obtaining a laminate (III) which is a printed matter in which the first ink layer, the second ink layer, and the layer containing a (meth)acrylic resin are laminated in this order on the heat-shrinkable PET film.
The obtained laminate (III) was used to evaluate adhesion and blocking resistance, and it was confirmed that the first ink layer and the second ink layer had excellent adhesion to the base film and blocking resistance.
Separately, the laminate (III) was wrapped around a mayonnaise bottle and immersed in 85°C water for 20 seconds to cause thermal shrinkage, and the shrinkability and hot water whitening resistance were evaluated. It was confirmed that the first ink layer and the second ink layer had excellent shrinkability and hot water whitening resistance.
Thereafter, the laminate (III) was peeled off from the mayonnaise bottle, and the alkali releasability was evaluated. It was confirmed that the first ink layer and the second ink layer were excellent in alkali releasability.
From the above results, it was confirmed that the laminate (III) had no problems in use.

The ink composition of the present invention can form an ink layer that has excellent hot water whitening resistance, shrink suitability, and alkali release properties, and is useful as an ink for gravure printing.

10 Laminate 11 Plastic film 12 Ink layer

Claims (7)

An ink composition for a shrink label, comprising a urethane resin (A), a (meth)acrylic resin (B), and a rosin derivative (C),
The glass transition temperature of the urethane resin (A) is −60 to −20° C.,
The (meth)acrylic resin (B) has an acid value of less than 10 mgKOH/g,
The rosin derivative (C) has an acid value of 150 to 310 mgKOH/g;
1. An ink composition for shrink labels, wherein the content of the urethane resin (A) is 2 to 10 mass %, calculated as solid content, the content of the (meth)acrylic resin (B) is 0.5 to 5 mass %, calculated as solid content, the content of the rosin derivative (C) is 2 to 6 mass %, calculated as solid content, and the total content of the urethane resin (A), the (meth)acrylic resin (B), and the rosin derivative (C) is 5 to 15 mass %, calculated as solid content, relative to the total mass of the ink composition for shrink labels. The ink composition for shrink labels according to claim 1, wherein the glass transition temperature of the (meth)acrylic resin (B) is 30 to 80°C. Further containing a (meth)acrylic resin (D),
The (meth)acrylic resin (D) has an acid value of 40 to 100 mgKOH/g,
2. The ink composition for a shrink label according to claim 1, wherein the content of the (meth)acrylic resin (D) is 0.1 to 2 mass % in terms of solid content, based on the total mass of the ink composition for a shrink label. The ink composition for shrink labels according to claim 1, further containing silica (F). The ink composition for a shrink label according to any one of claims 1 to 4 , which is for gravure printing. A laminate comprising a plastic film and an ink layer provided on one surface of the plastic film,
A laminate, wherein the ink layer is a layer formed using the ink composition for a shrink label according to claim 5 . A packaging material comprising the laminate according to claim 6 .

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