JP7742755B2 - Liquid printing inks, printed materials, and integrated packaging films - Google Patents

Description

The present invention relates to a liquid printing ink that can be used as a gravure ink or flexographic ink for flexible packaging.

The method of accumulating canned drinks, plastic bottled drinks, paper carton drinks, etc. using heat-shrinkable film (accumulated packaging film), which is inexpensive and easy to dispose of, instead of traditional cardboard, has become widely adopted, and is now used to accumulating not only beverages but also a variety of individually packaged items. Such accumulating packaging film is printed with liquid printing inks such as gravure ink and flexographic ink to give the items visibility, aesthetic appeal, and functionality.

Printing on cumulative packaging film is usually done on the inside of the film to ensure visibility is not impaired during distribution. However, in order to preserve the advantages of low cost and easy disposal, the printed surface is usually not protected, and the printed surface is packaged in direct contact with the items being cumulatively packaged. Furthermore, cumulative packaging film is a heat-shrinkable film that shrinks when heated to allow the items to be cumulatively packaged. Therefore, sometimes the ink printed on the cumulative packaging film can transfer to the items when heated, when the film shrinks, or during distribution.

Furthermore, in recent years, there has been a demand for biomass packaging materials, and printing inks used on packaging materials are also being required to use biomass materials rather than 100% petroleum-derived materials. There is a growing movement to use biomass materials to improve poor adhesion to film, which can cause color transfer, insufficient blocking properties, and even printability itself.

The heat-shrinkable films used in integrated packaging films are made from polyolefin resins such as polyethylene resins and polypropylene resins, ester resins, and polystyrene resins. Liquid printing inks containing polyurethane resin and a specific amount of chlorinated polypropylene resin (B) are known as inks with particularly excellent adhesion to polyolefin resin films (see, for example, Patent Document 1). However, even with these inks, there are cases where sufficient adhesion or heat-blocking resistance cannot be achieved when printed on integrated packaging films. Furthermore, these inks do not take into account the possibility of using biomass raw materials for improvement.

See JP 2019-38897 A

The problem that this invention aims to solve is to provide a liquid printing ink that is particularly suitable for use with integrated packaging film, that maintains its resistance to plate fogging while providing excellent adhesion to the heat-shrinkable film used in integrated packaging film, as well as improved crumpling resistance, scratch resistance, and heat blocking resistance, and that is improved using biomass raw materials.

As a result of extensive research to solve the above-mentioned problems, the inventors discovered that the above problems could be solved by using a liquid printing ink containing polyurethane resin and rosin-based acid resin as the main binder resins and an organic solvent, and that the ink contains specific amounts of rosin-based acid resin and polysaccharides relative to the total solids content of the ink, thereby completing the present invention.

That is, the present invention relates to a liquid printing ink containing a polyurethane resin and a rosin-based acid resin as main binder resins and an organic solvent, which liquid printing ink is characterized by satisfying the following:
(1) The ink contains 2.0 to 10.0% by mass of a rosin-based acid resin based on the total solid content of the ink.
(2) The ink contains 2.0 to 10.0% by mass of polysaccharides based on the total solid content of the ink.

In other words, the present invention relates to a liquid printing ink in which the polysaccharide is one or more selected from the group consisting of carrageenan, galactomannan, xanthan gum alginate, pectin, cellulose, cellulose derivatives, carboxymethylcellulose (CMC), starch, starch derivatives, and corn starch.

That is, the present invention relates to a liquid printing ink that further contains a chlorinated polyolefin resin.

That is, the present invention relates to printed matter printed with the liquid printing ink.

In other words, the present invention relates to an integrated packaging film printed with the liquid printing ink.

The liquid printing ink of the present invention maintains its resistance to plate fogging while also exhibiting excellent adhesion, rubbing resistance, scratch resistance, and heat blocking resistance, particularly to heat-shrinkable films such as polyolefin resin films. Stacked packaging films printed with the liquid printing ink of the present invention can be distributed without color transfer to stacked items.

Furthermore, polysaccharides are natural raw materials, and can contribute to the movement to improve them using biomass raw materials.

(Definition of words)
In the present invention, the liquid printing ink refers to a liquid ink, such as gravure ink or flexographic ink, that is applied to a printing method using a printing plate, and is preferably gravure ink or flexographic ink. The liquid printing ink of the present invention does not contain any active energy curable component, i.e., is an active energy ray non-reactive liquid ink.
In the present invention, all "parts" refer to "parts by mass,""total amount of ink" refers to the total amount of ink including all volatile components such as organic solvents, and "total amount of ink solids" refers to the total amount of only non-volatile components, excluding volatile components.

(binder resin)
The binder resin used in the present invention essentially comprises a polyurethane resin and a rosin-based resin.

(Polyurethane resin)
The polyurethane resin is not particularly limited as long as it is a polyurethane resin obtained by reacting a polyol with a polyisocyanate. Examples of the polyol include various known polyols commonly used in the production of polyurethane resins, and one or more of these may be used in combination. Examples include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, and dipropylene glycol. Saturated or unsaturated low molecular weight polyols (1) such as ethylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, and pentaerythritol; and mixtures of these low molecular weight polyols (1) with sebacic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, and trimellitic acid. polyester polyols (2) obtained by dehydration condensation or polymerization of polycarboxylic acids such as methyl acrylate, pyromellitic acid, or their anhydrides; polyester polyols (3) obtained by ring-opening polymerization of cyclic ester compounds, for example, lactones such as polycaprolactone, polyvalerolactone, and poly(β-methyl-γ-valerolactone); polycarbonate polyols (4) obtained by reacting the low-molecular-weight polyols (1) or the like with, for example, dimethyl carbonate, diphenyl carbonate, ethylene carbonate, or phosgene; polybutadiene glycols (5); glycols (6) obtained by adding ethylene oxide or propylene oxide to bisphenol A; and acrylic polyols (7) obtained by copolymerizing, in one molecule, one or more hydroxyethyl groups, hydroxypropyl acrylate, hydroxybutyl acrylate, or the like, or the corresponding methacrylic acid derivatives, with, for example, acrylic acid, methacrylic acid, or an ester thereof.

Examples of polyisocyanates include various known aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates commonly used in the production of polyurethane resins. For example, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1-methyl-2,4-phenylene diisocyanate, 1-methyl-2,6-phenylene diisocyanate, 1-methyl-2,5-phenylene diisocyanate, 1-methyl-2,6-phenylene diisocyanate, 1-methyl-3,5-phenylene diisocyanate, 1-ethyl-2,4-phenylene diisocyanate, 1-isopropyl-2,4-phenylene diisocyanate, 1,3-dimethyl-2,4-phenylene diisocyanate, and 1,3-dimethyl-4,6-phenylene diisocyanate. anate, 1,4-dimethyl-2,5-phenylene diisocyanate, diethylbenzene diisocyanate, diisopropylbenzene diisocyanate, 1-methyl-3,5-diethylbenzene diisocyanate, 3-methyl-1,5-diethylbenzene-2,4-diisocyanate, 1,3,5-triethylbenzene-2,4-diisocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 1-methyl-naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, naphthalene-2,7-diisocyanate, 1, Aromatic polyisocyanates such as 1-dinaphthyl-2,2'-diisocyanate, biphenyl-2,4'-diisocyanate, biphenyl-4,4'-diisocyanate, 3-3'-dimethylbiphenyl-4,4'-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, and diphenylmethane-2,4-diisocyanate; tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, and 1,3-cyclopentylene diisocyanate. Aliphatic or alicyclic polyisocyanates such as 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,3-di(isocyanatomethyl)cyclohexane, 1,4-di(isocyanatomethyl)cyclohexane, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, 2,2'-dicyclohexylmethane diisocyanate, and 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate can be used. These polyisocyanates can be used alone or in combination of two or more. Among these, these diisocyanate compounds can be used alone or in combination of two or more.

A chain extender can also be used. Examples of chain extenders include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, and dicyclohexylmethane-4,4'-diamine. Also usable are amines having a hydroxyl group in the molecule, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropyldiamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. These chain extenders can be used alone or in combination of two or more.

In addition, monovalent active hydrogen compounds can also be used as end-capping agents for the purpose of terminating the reaction. Examples of such compounds include dialkylamines such as di-n-butylamine, and alcohols such as ethanol and isopropyl alcohol. Furthermore, when it is particularly desired to introduce carboxyl groups into the polyurethane resin, amino acids such as glycine and L-alanine can be used as reaction terminators. These end-capping agents can be used alone or in combination of two or more.

The polyurethane resin can be produced by a known method, specifically by reacting a polyol, a polyisocyanate, a chain extender, and, if necessary, a monovalent active hydrogen compound. For example, a polyester polyol and a co-polyol are reacted with a diisocyanate compound in a ratio that results in an excess of isocyanate groups to obtain a prepolymer with terminal isocyanate groups. The resulting prepolymer is then reacted with a chain extender and/or a terminal blocking agent in a suitable solvent, i.e., an ester solvent commonly used in liquid inks, such as ethyl acetate, propyl acetate, or butyl acetate; a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone; an alcohol solvent such as methanol, ethanol, isopropyl alcohol, or n-butanol; a hydrocarbon solvent such as toluene, xylene, methylcyclohexane, or ethylcyclohexane; or a mixture of these solvents. Alternatively, the polyurethane resin can be produced by a single-stage method in which the polyester polyol, the co-polyol, the diisocyanate compound, the chain extender, and/or the terminal blocking agent are all reacted together in a suitable solvent. Of these methods, the two-stage method is preferred for obtaining a uniform polyurethane resin. Furthermore, when producing a polyurethane resin using the two-stage method, it is preferable to react the chain extender and/or end-capping agent so that the total amino group equivalent ratio (equivalent ratio) is 1/0.9 to 1.3. If the equivalent ratio of isocyanate groups to amino groups is less than 1/1.3, the chain extender and/or end-capping agent may remain unreacted, causing the polyurethane resin to yellow or emitting an odor after printing.

The weight-average molecular weight of the polyurethane resin obtained in this manner is preferably in the range of 10,000 to 100,000, more preferably in the range of 15,000 to 95,000. If the weight-average molecular weight of the polyurethane resin is 10,000 or more, the blocking resistance of the resulting ink composition and the strength and oil resistance of the printed film are less likely to decrease, and if it is 100,000 or less, the viscosity of the resulting ink composition does not become too high, and the gloss of the printed film is easily maintained.
The amount of polyurethane resin used in the liquid ink composition of the present invention is preferably 10 to 70% by mass, more preferably 15 to 50% by mass, based on the total amount of the ink.

(rosin-based resin)
The rosin-based resin used in the present invention can be any rosin and/or rosin derivative commonly used in printing inks, without any particular limitations. Specifically, rosin or rosin derivatives include rosins or carboxyl group-containing derivatives thereof. Examples of rosins include gum rosin, wood rosin, tall oil rosin, disproportionated rosin, hydrogenated rosin, and polymers thereof. Examples of rosin derivatives include carboxyl group-containing derivatives such as rosin derivatives to which unsaturated carboxylic acids such as maleic acid, fumaric acid, itaconic acid, and crotonic acid have been added.
The amount of rosin resin added is preferably 2.5 to 10% by mass, more preferably 5.0 to 10% by mass, based on the ink solid content.

In the present invention, it is preferable to use a rosin-modified maleic acid resin, which is a maleic acid derivative of rosin, or a rosin-modified fumaric acid resin, which is a fumaric acid derivative of rosin. The rosin-modified maleic acid resin or rosin-modified fumaric acid resin used in the present invention is not particularly limited, and any known rosin-modified maleic acid resin or rosin-modified fumaric acid resin can be used. The rosin-modified maleic acid resin or rosin-modified fumaric acid resin preferably has an acid value of 25 mg KOH/g or more and 320 mg KOH/g or less, and particularly preferably has an acid value of 100 mg KOH/g or more and 320 mg KOH/g or less.
The amount of the rosin-modified maleic acid resin or rosin-modified fumaric acid resin added is preferably 2.5 to 10% by mass, more preferably 5 to 10% by mass, based on the ink solids.

Commercially available rosin-based resins include Marquid No. 1, 2, 5, 6, 8, 31, 32, 33, 34, and 3002 manufactured by Arakawa Chemical Industries, Ltd., and Harima Chemicals Co., Ltd.'s Harimac R-80, T-80, R-100, M-453, M-130A, 135GN, 145P, and R-120AH, and Haritac 4851, 4821, 4740, and 28JA.

In the present invention, there are no particular limitations on the binder resin other than the blending of the polyurethane resin and the rosin resin in predetermined amounts, and known binder resins can also be used in combination. Examples of such binder resins include cellulose resins such as chlorinated polyolefin resins, nitrocellulose, and cellulose resins such as cellulose acetate propionate (CAP) and cellulose acetate butyronate (CAB), polyamide resins, acrylic resins, vinyl resins such as vinyl chloride-vinyl acetate copolymer resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, and polyvinyl chloride resins, polyester resins, alkyd resins, ketone resins, cyclized rubbers, chlorinated rubbers, butyral, and petroleum resins.
Among these, it is preferable to use a chlorinated polyolefin resin in combination.

(chlorinated polyolefin resin)
The chlorinated polyolefin resin used in the present invention is not particularly limited as long as it is a polyolefin resin in which at least a portion of the hydrogen atoms are substituted with chlorine atoms. The weight-average molecular weight of the chlorinated polyolefin is preferably 5,000 to 100,000, more preferably 5,000 to 70,000, and even more preferably 7,000 to 50,000. Furthermore, in order to improve adhesion to substrates, the chlorine content of the chlorinated polyolefin resin is preferably 25 to 45% by mass. Furthermore, from the viewpoint of solubility in organic solvents, the chlorine content is more preferably 26 to 43% by mass. Here, the chlorine content refers to the mass % content of chlorine atoms per 100% by mass of the chlorinated polyolefin resin. Furthermore, from the viewpoint of a balance with blocking resistance, the chlorinated polyolefin resin is contained in an amount of 1 to 30% by mass, preferably 2 to 20% by mass, of the ink solids.

Chlorinated polyolefin resins have flexible alkyl groups in their branched structure, making them flexible even at low temperatures and contributing to improved substrate adhesion. There are no particular restrictions on the structure of the polyolefin resin in chlorinated polyolefin resins. For example, resins containing homopolymers or copolymers of α-olefin-based unsaturated hydrocarbons such as polypropylene, poly-1-butene, and poly-4-methyl-1-pentene are preferred. Among these, chlorinated polypropylene resins containing a polypropylene structure (i.e., a chlorinated polypropylene structure) are particularly preferred.

(cellulose resin)
Examples of cellulose-based resins include cellulose acetate propionate, cellulose acetate butyrate and other cellulose ester resins, nitrocellulose (also known as soluble cellulose), hydroxyalkyl cellulose, carboxyalkyl cellulose, etc. The cellulose ester resin preferably has an alkyl group, and examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, a hexyl group, etc., and the alkyl group may further have a substituent.
Of the above, cellulose acetate propionate, cellulose acetate butyrate, and nitrocellulose are preferred as cellulose-based resins. Nitrocellulose is particularly preferred. The molecular weight is preferably a weight-average molecular weight of 5,000 to 200,000, more preferably 10,000 to 50,000. Furthermore, the glass transition temperature is preferably 120°C to 180°C. When used in combination with the polyurethane resin (A) of the present invention, improvements in blocking resistance, scratch resistance, and other physical properties of the ink film can be expected.
Nitrocellulose (nitrocellulose) is preferably obtained as a nitric acid ester by reacting natural cellulose with nitric acid to replace three hydroxyl groups in the six-membered ring of the anhydroglucopyranose group in the natural cellulose with nitric acid groups.

The use of nitrocellulose (nitrocellulose) provides high dispersibility in pigments, making it particularly suitable for use as a surface printing coating agent, as it can improve the strength of the printing ink film. The nitrocellulose (nitrocellulose) preferably has a nitrogen content of 10 to 13% by mass and an average degree of polymerization of 30 to 500, and more preferably a nitrogen content of 10 to 13% by mass and an average degree of polymerization of 45 to 290.

The amount of nitrocellulose (nitrocellulose) added is 0.1 to 5.0% by mass of the ink solids, preferably 0.5 to 2.0% by mass.

(Polyamide resin)
The polyamide resin is, for example, a thermoplastic polyamide soluble in an organic solvent, obtainable by polycondensation of a polybasic acid and a polyamine. In particular, a polyamide resin containing a reaction product of an acid component containing a polymerized fatty acid and/or a dimer acid with an aliphatic and/or aromatic polyamine is preferred, and further, a polyamide resin containing a portion of primary and secondary monoamines is preferred.
Polybasic acids used as raw materials for polyamide resins include, but are not limited to, adipic acid, sebacic acid, azelaic acid, phthalic anhydride, isophthalic acid, suberic acid, glutaric acid, fumaric acid, pimelic acid, oxalic acid, malonic acid, succinic acid, maleic acid, terephthalic acid, 1,4-cyclohexyldicarboxylic acid, trimellitic acid, dimer acid, hydrogenated dimer acid, and polymerized fatty acid. Among these, polyamide resins containing a structure derived from dimer acid or polymerized fatty acid as the main component (50% by mass or more in the polyamide resin) are preferred. Here, polymerized fatty acid refers to fatty acids obtained by the cyclization reaction of unsaturated fatty acids, and includes monobasic fatty acids, dimerized polymerized fatty acids (dimer acids), trimerized polymerized fatty acids, and the like. Fatty acids constituting dimer acids or polymerized fatty acids include those derived from natural oils such as soybean oil, palm oil, and rice bran oil, with those derived from oleic acid and linoleic acid being preferred.
The polybasic acid may be used in combination with a monocarboxylic acid, such as acetic acid, propionic acid, lauric acid, palmitic acid, benzoic acid, or cyclohexanecarboxylic acid.

Examples of polyamines include polyamines and primary or secondary monoamines. Examples of polyamines used in polyamide resins include aliphatic diamines such as ethylenediamine, propylenediamine, hexamethylenediamine, and methylaminopropylamine, and aliphatic polyamines such as diethylenetriamine and triethylenetetramine. Examples of alicyclic polyamines include cyclohexylenediamine and isophoronediamine. Examples of aromatic aliphatic polyamines include xylylenediamine, and examples of aromatic polyamines include phenylenediamine and diaminodiphenylmethane. Examples of primary and secondary monoamines include n-butylamine, octylamine, diethylamine, monoethanolamine, monopropanolamine, diethanolamine, and dipropanolamine.
The amount of polyamide resin added is 0.1 to 5.0% by mass, preferably 0.5 to 2.0% by mass, based on the ink solid content.

(acrylic resin)
The acrylic resin is not particularly limited as long as it is a copolymer of polymerizable monomers whose main component is a (meth)acrylic acid ester. Examples of polymerizable monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso-octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, iso-nonyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and phenoxyethyl (meth)acrylate. The polymerization method is also not particularly limited, and those obtained by known methods such as bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization can be used.
The weight average molecular weight of the acrylic resin is preferably in the range of 5,000 to 200,000, and more preferably in the range of 10,000 to 100,000.
The amount of acrylic resin added is 0.1 to 5.0% by mass, preferably 0.5 to 2.0% by mass, based on the ink solid content.

(polyester resin)
The polyester resin is not particularly limited as long as it is a polyester resin obtained by reacting an alcohol with a carboxylic acid using a known esterification polymerization reaction.
Examples of the alcohol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,2-pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, pentaerythritol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, spiroglycol, and isosorbide. These may be used alone or in combination of two or more. Among these, polyfunctional alcohols are preferred.
Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, linoleic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, and 1,4-cyclohexanedicarboxylic acid. These may be used alone or in combination of two or more. Among these, polyfunctional carboxylic acids are preferred.
The weight average molecular weight of the polyester resin is preferably 500 to 6000, more preferably 1400 to 5500. The amount of polyester resin added is 0.1 to 5.0% by mass, and preferably 0.5 to 2.0% by mass, based on the ink solid content.

(vinyl resin)
The vinyl resin used in the present invention may be a copolymer of a compound having a vinyl group, and representative copolymers include copolymers using vinyl chloride or vinyl acetate.
Examples of vinyl chloride resins include polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride-styrene copolymer, vinyl chloride-isobutylene copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-styrene-maleic anhydride terpolymer, vinyl chloride-styrene-acrylonitrile copolymer, vinyl chloride-butadiene copolymer, vinyl chloride-isoprene copolymer, vinyl chloride-chlorinated propylene copolymer, vinyl chloride-vinyl chloride Examples of vinyl chloride resins include vinyl chloride-based resins such as ethylene-vinyl acetate terpolymer, vinyl chloride-maleic acid ester copolymer, vinyl chloride-methacrylic acid ester copolymer, vinyl chloride-acrylonitrile copolymer, and vinyl chloride-various vinyl ether copolymers, as well as blends thereof and other chlorine-free synthetic resins such as acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl (meth)acrylate copolymer, blends with polyester, block copolymers, graft copolymers, etc. These vinyl chloride resins may be a mixture of two or more types, or may be a mixture with other synthetic resins.

Vinyl acetate resins are vinyl acetate monomers alone or copolymers of vinyl acetate monomers with polymerizable unsaturated monomers. Examples of unsaturated monomers include long-chain (meth)acrylic monomers such as alkyl (meth)acrylate monomers (e.g., n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate); hydroxyl group-containing (meth)acrylic monomers such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 1,4-butanediol mono(meth)acrylate, and (poly)ethylene glycol mono(meth)acrylate; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; vinyl monomers such as styrene, acrylonitrile, and vinyl chloride; and ethylene. These may be used alone or in combination of two or more.

The molecular weight of the vinyl resin is preferably a weight-average molecular weight of 5,000 to 100,000, and more preferably 10,000 to 70,000.

Among these, vinyl chloride resins which are homopolymers of the vinyl chloride monomer, vinyl acetate resins which are homopolymers of vinyl acetate monomer, and vinyl chloride-vinyl acetate copolymer resins obtained by copolymerizing the vinyl chloride monomer, vinyl acetate monomer, and, if necessary, vinyl alcohol or the like are preferred.
The vinyl chloride-vinyl acetate copolymer resin is not particularly limited as long as it is a copolymer of vinyl chloride and vinyl acetate. From the viewpoint of solubility in organic solvents, it is also preferable for it to contain hydroxyl groups derived from a vinyl alcohol structure. The hydroxyl value is preferably 20 to 200 mg KOH/g. The glass transition temperature is preferably 50 to 90°C.
In the vinyl chloride-vinyl acetate copolymer resin, the vinyl acetate monomer-derived structure is preferably 1 to 30 mass % and the vinyl chloride monomer-derived structure is preferably 70 to 95 mass % based on 100 mass % of the solid content, which improves solubility in organic solvents and further improves adhesion to substrates, coating properties, scratch resistance, etc.
The amount of vinyl resin added is 0.1 to 5.0% by mass, preferably 0.5 to 2.0% by mass, based on the ink solid content.

(hardening agent)
A curing agent may be used in combination with the binder resin. The curing agent may be any of those commonly used in organic solvent-based gravure inks, but the most commonly used are isocyanate-based curing agents.
The amount of the isocyanate compound added is preferably in the range of 0.3% by mass to 10.0% by mass, more preferably 1.0% by mass to 7.0% by mass, based on the solid content of the liquid printing ink, from the viewpoint of curing efficiency.
The total amount of binder resin is preferably in the range of 0.15 to 50% by mass, and most preferably in the range of 1 to 40% by mass, based on the ink solid content.

(polysaccharide)
The liquid printing ink of the present invention must contain 2.0 to 10.0% by mass of polysaccharides based on the total solid content of the ink.
Examples of polysaccharides used in the liquid printing ink of the present invention include carrageenan, galactomannan, xanthan gum alginate, pectin, cellulose, cellulose derivatives, carboxymethylcellulose (CMC), starch, starch derivatives, corn starch, etc. These may be used alone or in combination as appropriate. It is preferable to use raw materials called starch, starch derivatives, or corn starch, even though they are inexpensive. Starch is found in most plants, and any starch can be used in the present application without any particular limitations. Representative types and raw materials include corn starch (corn), potato starch (potato), sweet potato starch (sweet potato), tapioca starch (cassava), sago starch (sago palm), and rice starch (rice).

Furthermore, if the content of the polysaccharide in the total solid content of the ink is 2% by mass or more, it is possible to maintain higher abrasion resistance while maintaining substrate adhesion, scratch resistance, and blocking resistance, while if the content of the polysaccharide in the total solid content of the ink is 10% by mass or less, it tends to be possible to suppress a decrease in substrate adhesion.
The polysaccharide content is preferably 2 to 10% by mass, and most preferably 6 to 10% by mass, based on the total solid content of the ink.

(wax)
It is also preferable to add wax to the liquid printing ink of the present invention. As the wax, it is preferable to use a polyolefin wax or a fatty acid amide wax, which are well known in the field of liquid printing inks. The amount of wax added is not particularly limited and may be within a known range, but the total amount of wax is usually contained in the range of 0.1 to 20% by mass based on the total solids content of the ink.

Examples of polyolefin waxes include oxidized polyethylene wax and oxidized polypropylene wax. The polyolefin wax content is preferably 0.5 to 16% by mass, more preferably 1 to 10% by mass, and most preferably 1 to 5% by mass, based on the total solids content of the ink.

Fatty acid amide waxes include saturated fatty acid amides such as stearic acid amide and palmitic acid amide, unsaturated fatty acid amides such as erucic acid amide, substituted amides, and aromatic amides. Among these, the combined use of saturated fatty acid amides and unsaturated fatty acid amides is preferred as it further improves adhesion and scratch resistance, and a specific example is the combined use of palmitic acid amide and erucic acid amide. The fatty acid amide wax is preferably contained in an amount of 0.5 to 16% by mass, more preferably 1 to 10% by mass, and most preferably 1 to 5% by mass, based on the total solids content of the ink.

(organic solvent)
The organic solvent used in the liquid printing ink of the present invention is not particularly limited, and examples thereof include aromatic hydrocarbon organic solvents such as toluene, xylene, Solvesso #100, Solvesso #150, etc.; aliphatic hydrocarbon organic solvents such as hexane, methylcyclohexane, heptane, octane, decane, etc.; and various ester organic solvents such as methyl acetate, ethyl acetate, isopropyl acetate, normal propyl acetate, butyl acetate, amyl acetate, ethyl formate, butyl propionate, etc. Examples of water-miscible organic solvents include alcohols such as methanol, ethanol, propanol, butanol, and isopropyl alcohol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, and glycol ethers such as ethylene glycol (mono- and di-)methyl ether, ethylene glycol (mono- and di-)ethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono- and di-)methyl ether, diethylene glycol (mono- and di-)ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono- and di-)methyl ether, propylene glycol (mono- and di-)methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol (mono- and di-)methyl ether. These can be used alone or in combination of two or more.

In addition, from the perspective of both work hygiene during printing and the harmfulness of packaging materials, it is preferable to use ethyl acetate, propyl acetate, isopropanol, normal propanol, etc., and to avoid the use of aromatic solvents such as toluene or ketone-based solvents such as methyl ethyl ketone.

(Coloring agent)
The liquid printing ink of the present invention can be used as a varnish for adjusting the density of ink that does not contain a colorant or as an overprint varnish, or as an ink containing a colorant that is used in design printing, etc., for the purpose of imparting cosmetic properties, etc., including a colorant.
The colorant is preferably a pigment, and examples thereof include inorganic pigments and organic pigments used in general inks, paints, recording agents, etc. Examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo pigments, phthalocyanine pigments, halogenated phthalocyanine pigments, anthraquinone pigments, anthanthrone pigments, dianthraquinonyl pigments, anthrapyrimidine pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, dioxazine pigments, isoindolinone pigments, quinophthalone pigments, azomethine azo pigments, flavanthrone pigments, diketopyrrolopyrrole pigments, isoindoline pigments, indanthrone pigments, and carbon black pigments. Other examples include carmine 6B, lake red C, permanent red 2B, disazo yellow, pyrazolone orange, carmine FB, cromophtal yellow, cromophtal red, phthalocyanine blue, phthalocyanine green, dioxazine violet, quinacridone magenta, quinacridone red, indanthrone blue, pyrimidine yellow, thioindigo bordeaux, thioindigo magenta, perylene red, perinone orange, isoindolinone yellow, aniline black, diketopyrrolopyrrole red, and daylight fluorescent pigments. Both non-acid-treated and acid-treated pigments can be used. Specific examples of preferred organic pigments are listed below.

Examples of black pigments include C.I. Pigment Black 1, C.I. Pigment Black 6, C.I. Pigment Black 7, C.I. Pigment Black 9, and C.I. Pigment Black 20.

Examples of indigo pigments include C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, C.I. Pigment Blue 15:5, C.I. Pigment Blue 15:6, C.I. Pigment Blue 16, C.I. Pigment Blue 17:1, C.I. Pigment Blue 22, C.I. Pigment Blue 24:1, C.I. Pigment Blue 25, C.I. Pigment Blue 26, C.I. Pigment Blue 60, C.I. Pigment Blue 61, C.I. Pigment Blue 62, C.I. Examples of pigments include C.I. Pigment Blue 63, C.I. Pigment Blue 64, C.I. Pigment Blue 75, C.I. Pigment Blue 79, and C.I. Pigment Blue 80.

Examples of green pigments include C.I. Pigment Green 1, C.I. Pigment Green 4, C.I. Pigment Green 7, C.I. Pigment Green 8, C.I. Pigment Green 10, and C.I. Pigment Green 36.

Examples of red pigments include C.I. Pigment Red 1, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 4, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 8, C.I. Pigment Red 9, C.I. Pigment Red 10, C.I. Pigment Red 11, C.I. Pigment Red 12, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 17, C.I. Pigment Red 18, C.I. Pigment Red 19, C.I. Pigment Red 20, C.I. Pigment Red 21, C.I. Pigment Red 22, C.I. Pigment Red 23, C.I. Pigment Red 31, C.I. Pigment Red 32, C.I. Pigment Red 38, C.I. Pigment Red 41, C.I. Pigment Red 43, C.I. Pigment Red 46, C.I. Pigment Red 48, C.I. Pigment Red 48:1, C.I. Pigment Red 48:2, C.I. Pigment Red 48:3, C.I. Pigment Red 48:4, C.I. Pigment Red 48:5, C.I. Pigment Red 48:6, C.I. Pigment Red 49, C.I. Pigment Red 49:1, C.I. C.I. Pigment Red 49:2, C.I. Pigment Red 49:3, C.I. Pigment Red 52, C.I. Pigment Red 52:1, C.I. Pigment Red 52:2, C.I. Pigment Red 53, C.I. Pigment Red 53:1, C.I. Pigment Red 53:2, C.I. Pigment Red 53:3, C.I. Pigment Red 54, C.I. Pigment Red 57, C.I. Pigment Red 57:1, C.I. Pigment Red 58, C.I. Pigment Red 58:1, C.I. Pigment Red 58:2, C.I. Pigment Red 58:3, C.I. Pigment Red 58:4, C. C.I. Pigment Red 60:1, C.I. Pigment Red 63, C.I. Pigment Red 63:1, C.I. Pigment Red 63:2, C.I. Pigment Red 63:3, C.I. Pigment Red 64:1, C.I. Pigment Red 68, C.I. Pigment Red 68, C.I. Pigment Red 81:1, C.I. Pigment Red 83, C.I. Pigment Red 88, C.I. Pigment Red 89, C.I. Pigment Red 95, C.I. Pigment Red 112, C.I. Pigment Red 114, C.I. Pigment Red 119, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 136, C.I. Pigment Red 144, C.I. Pigment Red 146, C.I. Pigment Red 147, C.I. Pigment Red 149, C.I. Pigment Red 150, C.I. Pigment Red 164, C.I. Pigment Red 166, C.I. Pigment Red 168, C.I. Pigment Red 169, C.I. Pigment Red 170, C.I. Pigment Red 171, C.I. Pigment Red 172, C.I. Pigment Red 175, C.I. Pigment Red 176, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 179, C.I. Pigment Red 180, C.I. Pigment Red 181, C.I. Pigment Red 182, C.I. Pigment Red 183, C.I. Pigment Red 184, C.I. Pigment Red 185, C.I. Pigment Red 187, C.I. Pigment Red 188, C.I. Pigment Red 190, C.I. Pigment Red 192, C.I. Pigment Red 193, C.I. Pigment Red 194, C.I. Pigment Red 200, C.I. Pigment Red 202, C.I. Pigment Red 206, C.I. Pigment Red 207, C.I. Pigment Red 208, C.I. Pigment Red 209, C.I. Pigment Red 210, C.I. Pigment Red 211, C.I. Pigment Red 213, C.I. Pigment Red 214, C.I. Pigment Red 216, C.I. Pigment Red 215, C.I. Pigment Red 216, C.I. Pigment Red 220, C.I. Pigment Red 221, C.I. Pigment Red 223, C.I. Pigment Red 224, C.I. Pigment Red 226, C.I. Pigment Red 237, C.I. Pigment Red 238, C.I. Pigment Red 239, C.I. Pigment Red 240, C.I. Pigment Red 242, C.I. Pigment Red 245, C.I. Pigment Red 247, C.I. Pigment Red 248, C.I. Pigment Red 251, C.I. Pigment Red 253, C.I. Pigment Red 254, C.I. Pigment Red 255, C.I. Pigment Red 256, C.I. Pigment Red 257, C.I. Pigment Red 258, C.I. Pigment Red 260, C.I. Pigment Red 262, C.I. Pigment Red 263, C.I. Pigment Red 264, C.I. Examples of pigments include C.I. Pigment Red 266, C.I. Pigment Red 268, C.I. Pigment Red 269, C.I. Pigment Red 270, C.I. Pigment Red 271, C.I. Pigment Red 272, and C.I. Pigment Red 279.

Examples of purple pigments include C.I. Pigment Violet 1, C.I. Pigment Violet 2, C.I. Pigment Violet 3, C.I. Pigment Violet 3:1, C.I. Pigment Violet 3:3, C.I. Pigment Violet 5:1, C.I. Pigment Violet 13, C.I. Pigment Violet 19 (γ-type, β-type), C.I. Pigment Violet 23, C.I. Pigment Violet 25, C.I. Pigment Violet 27, C.I. Pigment Violet 29, C.I. Pigment Violet 31, C.I. Pigment Violet 32, C.I. Pigment Violet 36, C.I. Pigment Violet 37, C.I. Examples include C.I. Pigment Violet 38, C.I. Pigment Violet 42, and C.I. Pigment Violet 50.

Examples of yellow pigments include C.I. Pigment Yellow 1, C.I. Pigment Yellow 3, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, Pigment Yellow 17, C.I. Pigment Yellow 24, C.I. Pigment Yellow 42, C.I. Pigment Yellow 55, C.I. Pigment Yellow 62, C.I. Pigment Yellow 65, C.I. Pigment Yellow 74, C.I. Pigment Yellow 83, C.I. Pigment Yellow 86, C.I. Pigment Yellow 93, C.I. Pigment Yellow 94, C.I. Pigment Yellow 95, C.I. Pigment Yellow 109, C.I. Pigment Yellow 110, C.I. Pigment Yellow 117, C.I. Pigment Yellow 120, Pigment Yellow 125, C.I. Pigment Yellow 128, C.I. Pigment Yellow 129, C.I. Pigment Yellow 137, C.I. Pigment Yellow 138, C.I. Pigment Yellow 139, C.I. Pigment Yellow 147, C.I. Pigment Yellow 148, C.I. Pigment Yellow 150, C.I. Pigment Yellow 151, C.I. Pigment Yellow 153, C.I. Pigment Yellow 154, C.I. Pigment Yellow 155, C.I. Pigment Yellow 166, C.I. Pigment Yellow 168, C.I. Examples of suitable pigments include C.I. Pigment Yellow 174, C.I. Pigment Yellow 180, C.I. Pigment Yellow 185, and C.I. Pigment Yellow 213.

Examples of orange pigments include C.I. Pigment Orange 5, C.I. Pigment Orange 13, C.I. Pigment Orange 16, C.I. Pigment Orange 34, C.I. Pigment Orange 36, C.I. Pigment Orange 37, C.I. Pigment Orange 38, C.I. Pigment Orange 43, C.I. Pigment Orange 51, C.I. Pigment Orange 55, C.I. Pigment Orange 59, C.I. Pigment Orange 61, C.I. Pigment Orange 64, C.I. Pigment Orange 71, and C.I. Pigment Orange 74.

Examples of brown pigments include C.I. Pigment Brown 23, C.I. Pigment Brown 25, and C.I. Pigment Brown 26.

Among these, preferred pigments include C.I. Pigment Black 7 as a black pigment,
Indigo pigments include C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, C.I. Pigment Blue 15:6,
C.I. Pigment Green 7 as a green pigment,
Red pigments include C.I. Pigment Red 57:1, C.I. Pigment Red 48:1, C.I. Pigment Red 48:2, C.I. Pigment Red 48:3, C.I. Pigment Red 146, C.I. Pigment Red 242, C.I. Pigment Red 185, C.I. Pigment Red 122, C.I. Pigment Red 178, C.I. Pigment Red 149, C.I. Pigment Red 144, C.I. Pigment Red 166,
As purple pigments, C.I. Pigment Violet 23, C.I. Pigment Violet 37,
Yellow pigments include C.I. Pigment Yellow 83, C.I. Pigment Yellow 14, C.I. Pigment Yellow 180, C.I. Pigment Yellow 139,
Orange pigments include C.I. Pigment Orange 38, C.I. Pigment Orange 13, C.I. Pigment Orange 34, and C.I. Pigment Orange 64.
It is preferable to use at least one or two or more selected from this group.

Inorganic pigments include white inorganic pigments such as titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, lithopone, antimony white, and gypsum. Among inorganic pigments, titanium oxide is particularly preferred. Titanium oxide exhibits a white color and is preferable in terms of coloring power, hiding power, chemical resistance, and weather resistance. From the standpoint of printing performance, titanium oxide that has been treated with silica and/or alumina is preferred.

Non-white inorganic pigments include, for example, aluminum particles, mica, bronze powder, chrome vermilion, yellow lead, cadmium yellow, cadmium red, ultramarine, Prussian blue, red iron oxide, yellow iron oxide, iron black, and zircon. Aluminum is available in powder or paste form, but it is preferable to use it in paste form for ease of handling and safety reasons. Whether leafing or non-leafing aluminum is used can be selected appropriately based on brightness and density.

The pigment is preferably contained in an amount sufficient to ensure the concentration and coloring power of the liquid printing ink, i.e., 1 to 60% by mass of the total mass of the ink, or 10 to 90% by mass in terms of the weight ratio of solids in the ink. These pigments can be used alone or in combination of two or more types.

The liquid printing ink of the present invention may further contain, if necessary, an extender pigment, a leveling agent, an antifoaming agent, a plasticizer, an infrared absorbing agent, an ultraviolet absorbing agent, an aromatic agent, a flame retardant, and the like.
For example, if an appropriate amount of silica is added as the extender pigment, the abrasion resistance tends to be further improved.

The liquid printing ink of the present invention can be produced by dissolving and/or dispersing a binder resin, pigment, etc. in an organic solvent. Specifically, a pigment dispersion is produced by dispersing a pigment in an organic solvent with a binder resin, and the resulting pigment dispersion can then be blended with other compounds, etc., as necessary, to produce the ink.

The particle size distribution of the pigment in the pigment dispersion can be adjusted by appropriately adjusting the size of the grinding media of the disperser, the packing ratio of the grinding media, the dispersion treatment time, the discharge speed of the pigment dispersion, the viscosity of the pigment dispersion, etc. As the disperser, a commonly used one, for example, a roller mill, a ball mill, a pebble mill, an attritor, a sand mill, etc. can be used.
If the ink contains air bubbles or unexpectedly large particles, these will degrade the quality of the printed matter, so it is preferable to remove them by filtration, etc. Any conventional filter can be used.

The viscosity of the ink produced by the above method is preferably in the range of 10 mPa·s or more from the viewpoint of preventing sedimentation of the pigment and adequately dispersing it, and 1,000 mPa·s or less from the viewpoint of workability during ink production and printing. The above viscosity is measured at 25°C using a B-type viscometer manufactured by Tokimec Co., Ltd.
The viscosity of the ink can be adjusted by appropriately selecting the types and amounts of raw materials used, binder resins, pigments, organic solvents, etc. The viscosity of the ink can also be adjusted by adjusting the particle size and particle size distribution of the pigments in the ink.

(Printed matter and laminates)
A printed material can be obtained by printing the liquid printing ink of the present invention onto any substrate. The substrate used in the present invention is not particularly limited, and may be a paper or plastic substrate commonly used in gravure and flexographic printing, or a flexible packaging substrate used in food packaging. Examples of paper include fine paper used for printing packaging materials for cosmetics, beverages, pharmaceuticals, toys, and equipment, as well as kraft paper, pure white roll paper, glassine paper, parchment paper, Manila cardboard, white cardboard, coated paper, art paper, construction paper, tissue paper, cardboard, polyethylene-coated paper, and various synthetic papers.

Examples of film substrates include films and laminates made of polyamide resins such as nylon 6, nylon 66, and nylon 46; polyester resins such as polyethylene terephthalate (hereinafter sometimes referred to as PET), polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate; biodegradable resins such as polyhydroxycarboxylic acids such as polylactic acid, aliphatic polyester resins such as poly(ethylene succinate) and poly(butylene succinate); thermoplastic resins such as polyolefin resins such as polypropylene and polyethylene, polyimide resins, polyarylate resins, and mixtures thereof. Among these, films made of polyethylene terephthalate (PET), polyester, polyamide, polyethylene, and polypropylene are preferred. These substrate films may be unstretched or stretched, and their manufacturing method is not limited. The thickness of the substrate film is also not particularly limited, but is typically in the range of 1 to 500 μm.
The printing surface of the substrate film is preferably subjected to a corona discharge treatment, and may be vapor-deposited with aluminum, silica, alumina, or the like.

It is also preferable to use a film made from a material containing biomass-derived components as the film substrate. Biomass films are commercially available from various companies, and you can also use sheets such as those listed in the list of certified biomass products published by the Japan Organics Recycling Association.

Specific well-known films are made from biomass-derived ethylene glycol. Biomass-derived ethylene glycol is made from ethanol (biomass ethanol) produced from biomass. For example, biomass-derived ethylene glycol can be obtained by converting biomass ethanol into ethylene oxide using a conventional method, or by producing ethylene glycol. Commercially available biomass ethylene glycol may also be used; for example, biomass ethylene glycol available from India Glycoal Limited is suitable.

Alternatively, products made from biomass materials classified by the biomass plastic content specified in ISO 16620 or ASTM D6866 are also on the market. Radioactive carbon-14C exists in the atmosphere at a rate of 1 in 1012 particles, and this rate is the same for atmospheric carbon dioxide, so this rate remains the same even in plants that fix this carbon dioxide through photosynthesis. For this reason, the carbon in plant-derived resins contains radioactive carbon-14C. In contrast, the carbon in fossil fuel-derived resins contains almost no radioactive carbon-14C. Therefore, by measuring the concentration of radioactive carbon-14C in the resin using an accelerator mass spectrometer, the proportion of plant-derived resin in the resin, i.e., the biomass plastic content, can be determined. Examples of plant-derived low-density polyethylene, which is a biomass plastic with a biomass plastic content of 80% or more, preferably 90% or more as specified by ISO 16620 or ASTM D6866, include Braskem products under the trade names "SBC818," "SPB608," "SBF0323HC," "STN7006," "SEB853," and "SPB681," and films made from these materials can be suitably used.

For example, as an alternative to conventional polyethylene terephthalate films made from petroleum-based raw materials, films containing biomass polyesters and biomass polyethylene terephthalates, which have biomass-derived ethylene glycol as the diol unit and fossil fuel-derived dicarboxylic acids as the dicarboxylic acid units, are known.
The dicarboxylic acid units of the biomass polyester are derived from fossil fuels, and aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and derivatives thereof can be used without limitation.
Furthermore, the copolymer polyester may be one in which, in addition to the above diol component and dicarboxylic acid component, a copolymerization component is added as a third component, such as a bifunctional oxycarboxylic acid, or at least one polyfunctional compound selected from the group consisting of a trifunctional or higher functional polyhydric alcohol, a trifunctional or higher functional polycarboxylic acid and/or anhydride thereof, and a trifunctional or higher functional oxycarboxylic acid, in order to form a crosslinked structure.

Furthermore, for example, as an alternative to conventional polyolefin films using petroleum-based raw materials, biomass polyolefin films such as biomass polyethylene films containing polyethylene resins made from biomass-derived ethylene glycol and biomass polyethylene-polypropylene films are also known.
The polyethylene-based resin is not particularly limited except that the biomass-derived ethylene glycol is used as part of the raw material, and examples thereof include an ethylene homopolymer and a copolymer of ethylene and an α-olefin containing ethylene as the main component (an ethylene-α-olefin copolymer containing 90% by mass or more of ethylene units), and these may be used alone or in combination of two or more.
The α-olefin constituting the copolymer of ethylene and α-olefin is not particularly limited, and examples thereof include α-olefins having 4 to 8 carbon atoms such as 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene. Known polyethylene resins such as low-density polyethylene resin, medium-density polyethylene resin, and linear low-density polyethylene resin can be used.
Among these, from the viewpoint of making it even more difficult for damage such as holes or tears to occur even when films rub against each other, linear low-density polyethylene resin (LLDPE) (a copolymer of ethylene and 1-hexene or a copolymer of ethylene and 1-octene) is preferred, and linear low-density polyethylene resin having a density of 0.910 to 0.925 g/cm is more preferred.

Films and sheets containing starch, a biomass raw material, and polylactic acid are also known. These can be selected and used appropriately depending on the application.

The biomass film may be a laminate of multiple biomass films or a laminate of a conventional petroleum-based film and a biomass film. These biomass films may be unstretched or stretched, and their manufacturing method is not limited. The thickness of the base film is also not particularly limited, but is usually in the range of 1 to 500 μm.
The printing surface of the substrate film is preferably subjected to a corona discharge treatment, and may be vapor-deposited with aluminum, silica, alumina, or the like.

(accumulated packaging film)
The liquid printing ink of the present invention is particularly suitable as a printing ink for heat-shrinkable films used as integrated packaging films.
Examples of resins used for heat-shrinkable films include one or a mixture of two or more selected from polyester resins such as polyethylene terephthalate resins and polylactic acid resins, polyolefin resins such as polyethylene resins and polypropylene resins, and thermoplastic resins such as polystyrene resins, polyvinyl chloride resins, and polyamide resins. Of these, resin films of polyester resins, polyolefin resins, polystyrene resins, etc. are often used from the viewpoint of shrink properties, etc. The liquid printing ink of the present invention has particularly good adhesion to polyolefin resins, so polyolefin resin films are preferred, and polyethylene resins and polypropylene resins are particularly preferred.
In addition, biomass polyester resin films such as biomass polyethylene terephthalate resin films using the aforementioned biomass polyethylene terephthalate resins, etc., and biomass polyolefin resin films such as biomass polyethylene resin films using the aforementioned biomass polyethylene resins, etc., may also be used and are preferred.
The heat-shrinkable film may be a single-layer film or a multi-layer film having a plurality of layers. In the case of a multi-layer film, the back surface may include a heat-sealable layer.

The thickness of the heat-shrinkable film is not particularly limited, but from the standpoints of strength, rigidity, shrink properties, economy, etc., it is preferably 5 to 120 μm, more preferably 7 to 100 μm, and particularly preferably 10 to 80 μm. The heat-shrinkable film is preferably transparent (colorless and transparent or colored and transparent) so that the printed layer of the liquid printing ink of the present invention can be seen through it, and colorless and transparent is more preferred.

In order to achieve good heat shrinkability, heat-shrinkable films are preferably stretched in at least one direction (uniaxial stretching), and biaxial stretching is particularly preferred. The stretching temperature varies depending on the type of resin that makes up the film, but is, for example, 60 to 130°C. The stretching ratio is preferably about 2 to 8 times in the main stretching direction for uniaxially stretched films, and in both one direction and the other direction perpendicular to that direction for biaxially stretched films. Stretching methods that can be used include roll, tenter, and tube methods.

The heat shrinkage rate of the heat-shrinkable film is 20% or more in the main stretching direction for uniaxially stretched films, and 20% or more in both directions (one direction and the other direction) for biaxially stretched films, preferably 30 to 80%, and particularly preferably 40 to 80% (heat treatment conditions: immersion in 90°C warm water for 10 seconds). For uniaxially stretched films, the heat shrinkage rate in the direction perpendicular to the main stretching direction is preferably -3 to 15%, more preferably -1 to 10%, and particularly preferably -1 to 5% (heat treatment conditions: same as above).

If necessary, an ink-receptive layer may be provided on the heat-shrinkable film to facilitate printing.
As described above, the liquid printing ink of the present invention can improve adhesion and blocking resistance even on biaxially oriented polypropylene film that has not been subjected to corona discharge treatment, thereby making it possible to maximize the effects of the present invention.

The present invention will be explained in more detail using examples. Hereinafter, all "parts" and "%" are based on mass.

(Polyurethane resin)
As the polyurethane resin, "Product name: Burnock ECL-341, weight average molecular weight 85,000" manufactured by DIC Corporation was used.

(chlorinated polypropylene resin)
As the chlorinated polypropylene resin, "Superchlorine 360T, chlorine content 60%" manufactured by Nippon Paper Chemicals Co., Ltd. was used.

(rosin resin)
The rosin resin used was "Product name: Marquid 31, weight average molecular weight 1200" manufactured by Arakawa Chemical Industries, Ltd.

Example 1
A white liquid printing ink was prepared by adding a mixed solvent of methyl ethyl ketone, ethyl acetate, isopropyl alcohol, and n-propyl acetate to 7.5 parts of the polyurethane resin solids, 1.8 parts of chlorinated polypropylene resin solids, 2.5 parts of rosin resin solids, 31 parts of titanium oxide, 3 parts of starch as a polysaccharide, 1 part of polytetrafluoroethylene wax TF9205 (manufactured by 3M Japan Ltd.), 0.6 parts of a polyolefin wax compound, and 0.6 parts of a fatty acid amide compound, and kneading the mixture using a Mighty Mill (manufactured by Inoue Seisakusho Co., Ltd.).

Examples 2 to 4
According to the formulation in Table 1, a white liquid printing ink was prepared in the same manner as in Example 1.

Comparative Examples 1 to 3
White liquid printing inks were prepared in the same manner as in Example 1, except that the starch and/or rosin resin shown in Table 2 was not added.

[Manufacturing method for film prints Part 1]
White monochrome printing The viscosity of each white liquid printing ink was adjusted to 16 seconds (25°C) using a Zahn cup #3 (manufactured by Rigo Co., Ltd.) with a mixed solvent (ethyl acetate: isopropyl alcohol: methyl ethyl ketone: propyl acetate = 1:1:1:1 by mass ratio), and then printed on substrate 1: biaxially oriented polypropylene film (hereinafter referred to as OPP film, thickness 15 μm) that had not been subjected to corona discharge treatment using a gravure proofing machine equipped with a gravure gradation plate engraved to a plate depth of 35 μm, and dried at 40°C to obtain a print.
Indigo/white overprinting (1) The viscosity of the accumulated indigo liquid printing ink was adjusted to 16 seconds (25°C) with ethyl acetate using a Zahn cup #3 (manufactured by Rigo Co., Ltd.), and then printed onto substrate 1: biaxially oriented polypropylene film (hereinafter referred to as OPP film, thickness 15 μm) that had not been subjected to corona discharge treatment using a gravure proofing machine equipped with a gravure gradation plate engraved to a plate depth of 35 μm, and dried at 40°C to obtain a print.
(2) On the indigo print obtained in (1), the viscosity of each white liquid printing ink was adjusted to 16 seconds (25°C) with ethyl acetate using a Zahn Cup #3 (manufactured by Rigo Co., Ltd.), and then printed using a gravure proofing machine equipped with a gravure gradation plate engraved to a plate depth of 35 μm, and dried at 40°C to obtain a print.

[Manufacturing method for film prints, part 2]
White monochrome printing The viscosity of each white liquid printing ink was adjusted to 16 seconds (25°C) using a Zahn cup #3 (manufactured by Rigo Co., Ltd.) with a mixed solvent (ethyl acetate: isopropyl alcohol: methyl ethyl ketone: propyl acetate = 1:1:1:1 by mass ratio), and then printed on substrate 2: Kohjin Bio Polyset (biomass shrink film, 15 μm thick, manufactured by Kohjin Film & Chemicals Co., Ltd.) using a gravure proofing machine equipped with a gravure gradation plate engraved to a plate depth of 35 μm, and dried at 40°C to obtain a print.
Indigo/white overprinting (1) The viscosity of the accumulated indigo liquid printing ink was adjusted to 16 seconds (25°C) with ethyl acetate using a Zahn cup #3 (manufactured by Rigo Co., Ltd.), and then printed on substrate 2: Kohjin Bio Polyset (biomass shrink film, 15 μm thick, manufactured by Kohjin Film & Chemicals Co., Ltd.) using a gravure proofing machine equipped with a gravure gradation plate engraved to a plate depth of 35 μm, and dried at 40°C to obtain a print.
(2) On the indigo print obtained in (1), the viscosity of each white liquid printing ink was adjusted to 16 seconds (25°C) with ethyl acetate using a Zahn Cup #3 (manufactured by Rigo Co., Ltd.), and then printed using a gravure proofing machine equipped with a gravure gradation plate engraved to a plate depth of 35 μm, and dried at 40°C to obtain a print.

[Adhesion]
Using the white liquid printing inks shown in Tables 1 and 2, monochrome white and indigo/white prints obtained by the film print manufacturing method were left to stand for 24 hours to produce prints.
Next, cellophane tape (manufactured by Nichiban Co., Ltd.) was applied to the printed surface, and the tape was quickly peeled off, and the condition of the printed surface was visually evaluated.
(Evaluation criteria)
◯: The printed film did not peel off from the film at all.
Δ: Less than 30% of the area of the printed film peeled off from the film.
x: 70% or more of the area of the printed film peeled off from the film.

[Kneading resistance]
Using the white liquid printing inks shown in Tables 1 and 2, monochrome white and blue/white prints obtained by the film print manufacturing method were left to stand for 24 hours to produce prints.
Next, the ink surfaces were rubbed back and forth five times, and the state of ink absorption was visually evaluated.
(Evaluation criteria)
◯: The printed film did not peel off from the film at all.
Δ: Less than 30% of the area of the printed film peeled off from the film.
x: 70% or more of the area of the printed surface peeled off from the film.

[Scratch resistance]
Using the white liquid printing inks shown in Tables 1 and 2, monochrome white and blue/white prints obtained by the film print manufacturing method were left to stand for 24 hours to produce prints.
Next, the ink surface was rubbed with a fingernail 20 times and the state of ink absorption was visually evaluated.
(Evaluation criteria)
◯: The printed film did not peel off from the film at all.
Δ: Less than 30% of the area of the printed film peeled off from the film.
x: 70% or more of the area of the printed surface peeled off from the film.

[Heat blocking resistance]
Using the white liquid printing inks shown in Tables 1 and 2, monochrome white and blue/white prints obtained by the film print manufacturing method were left to stand for 24 hours to produce prints.
Next, a polystyrene sheet, which is intended to be a container for collecting the printed surface, is pressed onto the printed surface using a heat seal bar at a pressure of 0.1 MPa for 1 second, and the degree of ink absorption is confirmed.
Test temperature: 100°C
(Evaluation criteria)
◯: No ink is absorbed by the polystyrene sheet.
△: 25% or more of the ink is absorbed by the polystyrene sheet.
x: 50% or more of the ink is absorbed by the polystyrene sheet.

[Plate fogging]
The white liquid printing inks shown in Tables 1 and 2 were adjusted to 16 seconds (25°C) using a Zahn Cup #3 (manufactured by Rigo Co., Ltd.) with a 50/50 ethyl acetate/isopropyl alcohol mixed organic solvent, and printed on the treated surface of Substrate 1: biaxially oriented polypropylene film (thickness: 15 μm) that had been corona discharge-treated on one side using an MD-type gravure printing press (manufactured by Fuji Machine Co., Ltd.) equipped with a laser gravure plate with a plate depth of 30 μm. The degree of smearing (plate fogging) in the non-printed highlight areas was visually evaluated when printing was performed at a printing speed of 200 m/min with a gravure plate circumference of 600 mmφ.
(Evaluation criteria)
○: No staining at all on non-printed areas.
△: There is a little dirt on the non-printed part.
×: Staining is noticeable in the non-printed areas.

Tables 1 and 2 show the formulations of the white liquid printing inks and the evaluation results of the prints obtained by the first and second methods of producing film prints.
In addition, all values in the table indicate the mass of the solid content.
Also, blank spaces indicate that the ink is not blended. "Indigo x White" indicates an overprint of indigo and white.

The liquid printing ink of the present invention maintains its plate fogging resistance while also providing excellent adhesion, crumpling resistance, scratch resistance, and heat blocking resistance to heat-shrinkable films used in integrated packaging films.

Claims (5)

A liquid printing ink containing a polyurethane resin and a rosin-based acid resin as main binder resins and an organic solvent, characterized in that the liquid printing ink satisfies the following:
(1) The ink contains 2.0 to 10.0% by mass of a rosin-based acid resin based on the total solid content of the ink.
(2) The ink contains 2.0 to 10.0% by mass of polysaccharides based on the total solid content of the ink.
(3) The polysaccharide is at least one selected from the group consisting of carrageenan, galactomannan, xanthan gum alginate, pectin, starch, starch derivatives, and corn starch. 2. The liquid printing ink according to claim 1, wherein the rosin-based acid resin is contained in an amount of 5.0 to 10.0% by mass based on the total solid content of the ink. The liquid printing ink according to claim 1 or 2, which contains a chlorinated polyolefin resin. A printed matter printed with the liquid printing ink described in any one of claims 1 to 3. A film for integrated packaging printed with the liquid printing ink described in any one of claims 1 to 3.