JP2008163231A - Printing ink and plastic label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing ink composed of an acrylic resin and a cellulosic resin, having excellent leveling property to give good printability, having excellent long-term ink stability and exhibiting excellent properties such as adhesiveness to a plastic film, heat-resistance and antiblocking property. <P>SOLUTION: The printing ink comprises an acrylic resin, a cellulosic resin and a solvent containing a low-volatile solvent having a specific evaporation rate of 20-100 in an amount of 0.1-30 wt.% based on the total solvent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to printing inks and plastic labels.

  Currently, plastic bottles such as PET bottles and metal bottles such as bottle cans are widely used as containers for beverages such as tea and soft drinks. These containers are often equipped with plastic labels for display, decoration, and functionality. These plastic labels have decorativeness, workability (followability to containers), wide display area, etc. Due to its merit, shrink labels and stretch labels are widely used. Usually, printing ink is applied and printed on the surface of these labels for the purpose of imparting decorative properties such as letters and designs, and providing functionality such as scratch prevention and slipperiness.

  As these printing inks, printing inks made of cellulose resins such as acrylic resins and nitrocellulose are widely used (see, for example, Patent Documents 1 and 2). Alcohol is mainly used as a solvent for these printing inks, but in these alcohol solvents, cellulose resins such as nitrocellulose are relatively easy to precipitate, and the leveling property in the coating process is lowered, resulting in uneven coating. Had. On the other hand, methods such as using a mixture of components such as ethyl acetate in the solvent are known, but ethyl acetate is more volatile than alcohol and is used for long-term storage and long-time application. However, since only ethyl acetate is volatilized, the alcohol concentration of the solvent is increased, and the cellulose resin is precipitated, the problem remains that the ink stability is poor.

JP 2004-175858 A JP 2004-2111016 A

  Therefore, the object of the present invention is that printing ink comprising an acrylic resin and a cellulose resin has excellent leveling properties, and therefore has good printability, excellent long-term ink stability, and adhesion to a plastic film. It is in providing the printing ink which shows the characteristic excellent also in the property, heat resistance, blocking resistance, etc. Another object of the present invention is to provide a plastic label using the printing ink.

  As a result of intensive studies to achieve the above object, the present inventors have formulated a specific amount of a low-volatile solvent having a specific specific evaporation rate as a solvent in a printing ink composed of an acrylic resin and a cellulose resin. It has been found that printing inks with improved printing suitability and ink stability, and also excellent adhesion to plastic films, heat resistance, blocking resistance, etc. and plastic labels using the printing inks can be obtained. Completed the invention.

  That is, the present invention includes an acrylic resin, a cellulose resin, and a solvent containing 0.1 to 30% by weight of a low volatile solvent having a specific evaporation rate of 20 to 100 with respect to the total solvent. A printing ink is provided.

  Furthermore, this invention provides the said printing ink whose weight average molecular weights of the said acrylic resin are 8000-50000, and whose glass transition temperature is 35-80 degreeC.

  Further, in the present invention, the cellulose resin is a nitrocellulose resin, and the blending ratio of the acrylic resin and the nitrocellulose resin (the former / the latter) is 50/50 to 95/5 (weight ratio). Provide printing ink.

  Furthermore, this invention provides the said printing ink which is an ink for gravure printing or a flexographic printing.

  Furthermore, the present invention provides a plastic label having a printed layer formed by applying and drying the above printing ink on at least one surface of a polyester plastic film or a polystyrene plastic film.

  Since the printing ink of the present invention adds a specific amount of a low-volatile solvent as a solvent, the evaporation rate of the ink solvent can be controlled and the precipitation of the cellulose-based resin can be suppressed. Printability is obtained. Furthermore, excellent adhesion to a plastic film, heat resistance, and blocking resistance can be obtained.

  Below, the printing ink and plastic label of this invention are demonstrated in detail.

  The printing ink of the present invention comprises an acrylic resin, a cellulose resin and a solvent as essential components.

Examples of the monomer component constituting the acrylic resin include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, Isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth ) (Meth) acrylic acid alkyl esters such as isononyl acrylate, (meth) acrylic acid decyl, and (meth) acrylic acid dodecyl [preferably (meth) acrylic acid C _1-12 alkyl ester and the like]; (meth) acrylic acid, Carboxyl group-containing polymerizable unsaturated compounds such as crotonic acid, itaconic acid, fumaric acid, maleic acid, etc. Anhydrous; 2-hydroxymethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, diethylene glycol mono (meth) acrylate, dipropylene glycol mono Examples include hydroxyl group-containing (meth) acrylic acid esters such as (meth) acrylate [preferably (meth) acrylic acid hydroxy C _1-8 alkyl ester and the like].

  In addition to the above, if necessary, (meth) acrylic acid cycloalkyl esters such as cyclohexyl (meth) acrylate; N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (Meth) acrylic acid amide derivatives such as (meth) acrylamide and N, N-diethyl (meth) acrylamide; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dimethylamino (Meth) acrylic acid dialkylaminoalkyl esters such as propyl (meth) acrylate and dipropylaminopropyl (meth) acrylate; styrene compounds such as styrene, vinyltoluene and α-methylstyrene; vinyl acetate, Vinyl esters such as vinyl pionate; Vinyl halides such as vinyl chloride; Vinyl ethers such as methyl vinyl ether; Cyano group-containing vinyl compounds such as (meth) acrylonitrile; Polymerizability of olefins and dienes such as ethylene and propylene Unsaturated compounds can also be used as monomer components.

  Acrylic resins can be used alone or in combination of two or more resins having different monomer compositions. For example, as acrylic resin, (i) carboxyl group and hydroxyl group-containing acrylic polymer, (ii) mixture of carboxyl group-containing acrylic polymer and hydroxyl group-containing acrylic polymer, (iii) carboxyl group and hydroxyl group A mixture of a non-group-containing acrylic polymer, a carboxyl group-containing acrylic polymer, and a hydroxyl group-containing acrylic polymer can be used.

  The weight average molecular weight of the acrylic resin is preferably 8000 to 50000, more preferably 20000 to 40000. When the weight average molecular weight is less than 8000, the heat resistance may be insufficient. On the other hand, when the weight average molecular weight exceeds 50,000, compatibility with the cellulose resin is lowered, the viscosity of the ink itself is increased, and the gravure printability may be lowered. In addition, the said weight average molecular weight means the value in acrylic resin total. Therefore, when two or more polymers having different monomer compositions are blended and used as the acrylic resin, a polymer having a weight average molecular weight outside the above range can be used, but the weight average molecular weight is within the above range. It is preferable to blend the polymers inside.

  The glass transition temperature (Tg) of the acrylic resin is preferably in the range of 35 to 80 ° C, more preferably 40 to 60 ° C. If the glass transition temperature is less than 35 ° C., the heat resistance of the printing layer may be reduced or blocking may occur easily. If the glass transition temperature exceeds 80 ° C., the solubility in a solvent may be reduced or the printability may be reduced. .

  The acid value of the acrylic resin is preferably 1 to 20 mg-KOH / g. When the acid value is larger, the adhesion tends to be higher. However, when the acid value exceeds 20 mg-KOH / g, the pigment may aggregate when used as a white printing ink to which a white pigment such as titanium oxide is added. is there. The hydroxyl value of the acrylic resin is preferably 0 to 10 mg-KOH / g. When the hydroxyl value exceeds 10 mg-KOH / g, the pigment may aggregate in the same manner as described above. In addition, said acid value and hydroxyl value each mean the value in acrylic resin total. When two or more kinds of polymers having different monomer compositions are blended and used as the acrylic resin, the acid value (or hydroxyl value) of the acrylic resin is the acid value (or hydroxyl value) of each polymer and each It can obtain | require by calculation from the weight ratio of a polymer.

  The solubility parameter (Sp value) of the acrylic resin is preferably 8.0 to 9.0 from the viewpoint of adhesion to the polyester film.

  Commercially available products may be used as the acrylic resin used in the present invention, such as “Alfon UP-1100” manufactured by Toagosei Co., Ltd., “Dianar BR116” manufactured by Mitsubishi Rayon Co., Ltd., etc. is there.

  Examples of the cellulose resin include nitrocellulose (nitrified cotton) resin, esterified cellulose resin esterified with carboxylic acid, and the like. Among these, a nitrocellulose resin is preferable.

  The nitrification degree of the nitrocellulose resin is preferably 10.7 to 11.4% from the viewpoint of ink stability.

  The average degree of polymerization of the nitrocellulose resin is preferably 45 to 95. If the average degree of polymerization is less than 45, the effect of adding nitrocellulose may be reduced and the heat resistance may be poor. If it exceeds 95, the viscosity of the printing ink may increase and the gravure printability may decrease.

  The esterified cellulose resin of the present invention is a resin obtained by esterifying cellulose with carboxylic acid. Examples of the carboxylic acid include acetic acid, butyric acid, propionic acid, acetic anhydride, and butyric anhydride. Specific examples of such esterified cellulose resins include cellulose acetate resin, cellulose acetate butyrate (CAB) resin, and cellulose acetate propionate (CAP) resin. Particularly preferred are cellulose acetate butyrate (CAB) resin and cellulose acetate propionate (CAP) resin. The esterified cellulose resin of the present invention does not include nitrate ester (nitrocellulose).

  The esterification degree of the esterified cellulose resin is preferably 41 to 56%. The degree of esterification means the ratio of esterified hydroxyl groups in the cellulose resin.

  12000-75000 is preferable and, as for the weight average molecular weight of esterified cellulose, More preferably, it is 20000-40000. If the weight average molecular weight is less than 12,000, the effect of adding esterified cellulose is small, and if it exceeds 75,000, the viscosity of the printing ink increases and the gravure printability may decrease.

  As the cellulose resin used in the present invention, a commercially available product may be used, and “LIG 1/2, 1/4, 1/8” (above, nitrocellulose resin) manufactured by Bergerac NC is available on the market. Is possible.

  In the printing ink of the present invention, the blend ratio of the acrylic resin and the cellulose resin (particularly the nitrocellulose resin) is preferably in the range of acrylic resin / cellulose resin (weight ratio) = 50/50 to 95/5, More preferably, it is 60 / 40-90 / 10. When this ratio is lower than 50/50 (there are many cellulose resins), the solubility in a solvent is lowered and the ink cannot be used as a printing ink, and is higher than 95/5 (there are many acrylic resins). , Blocking resistance, heat resistance and the like are insufficient.

  In the printing ink of the present invention, the ratio of the total amount of the acrylic resin and the cellulose resin to the total resin component (solid content) is usually 50% by weight or more, and preferably 65% by weight or more. In addition, although various thermoplastic resins or thermosetting resins can be used as the resin component other than the acrylic resin and the cellulose resin, a urethane resin or a styrene / maleic anhydride resin is preferable.

The solvent used in the printing ink of the present invention contains a low-volatile solvent having a specific evaporation rate of 20 to 100 as an essential component. The low volatility solvent is not particularly limited, but from the viewpoint of compatibility with the cellulose-based resin in the ink and leveling properties on the printed matter, specific evaporation from solvents such as glycol ethers and glycol ether esters. A solvent satisfying the above speed is preferably exemplified. Specific examples include propylene glycol monomethyl ether (including those produced from 1,2-propanediol and those produced from 1,3-propanediol), propylene glycol monomethyl ether acetate, and the like. Particularly preferred are propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate, and particularly preferred when nitrocellulose is used as the cellulosic resin. The specific evaporation rate refers to the evaporation rate of the solvent that evaporates from a unit area per unit time at 25 ° C., and is expressed as a percentage of the evaporation rate of the sample with respect to the evaporation rate of n-butyl acetate. As a specific measuring method, for example, two hooded chemical balances capable of supplying nitrogen gas are used. Place on a 10 cmφ petri dish containing 5C (9 cmφ), take n-butyl acetate on one side and 0.7 mL each on the other side, and supply nitrogen gas simultaneously at a flow rate of 30 NL / ml. The time until the weight reduction rate of the sample reaches 90% can be measured and calculated by the following formula. Specific evaporation rate (%) = T ₁ / T ₂ × 100
T ₁ : Time required for 90% weight loss of n-butyl acetate T ₂ : Time required for 90% weight loss of sample

  The content of the low-volatile solvent is from 0.1 to 30% by weight, preferably from 10 to 20% by weight, based on the whole solvent, from the viewpoints of ink stability and blocking resistance.

  Solvents other than the low-volatile solvent used in the printing ink of the present invention are not particularly limited, alcohol solvents; ester solvents; ketones such as methyl ethyl ketone and methyl isobutyl ketone; aromatic hydrocarbons such as toluene and xylene An aliphatic hydrocarbon such as hexane and octane; an alicyclic hydrocarbon such as cyclohexane and methylcyclohexane; a glycol such as ethylene glycol and propylene glycol, and the like, and a solvent having a specific evaporation rate exceeding 100 can be used. Among these, alcohol-based solvents and ester-based solvents are preferable, and mixed solvents of alcohol-based solvents and ester-based solvents are most preferable from the viewpoints of compatibility with resins and difficulty in swelling and dissolving plastic films. That is, the solvent used in the printing ink of the present invention is most preferably a mixed solvent composed of at least three types of solvents, alcohol solvents, ester solvents, and low volatility solvents.

  As the alcohol solvent, a lower alcohol having 1 to 4 carbon atoms is preferable. Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, isopropyl alcohol, propanol, isopropyl alcohol, butanol and the like, and isopropyl alcohol is particularly preferable.

  The content of the alcohol solvent is preferably 5 to 50% by weight, more preferably 10 to 45% by weight, based on the whole solvent. When the content of the alcohol solvent is less than 5% by weight, the polystyrene film may be deteriorated and dissolved, or the drying property may be deteriorated. If it exceeds wt%, the adhesion to the polyester film may be lowered.

  The ester solvent may be an ester solvent having a specific evaporation rate higher than 100, and specific examples thereof include ethyl acetate, butyl acetate, and propyl acetate. The content of the ester solvent with respect to the entire solvent is preferably 40 to 80% by weight, more preferably 50 to 75% by weight. If the ester solvent is less than 40% by weight, the solvent attack force on the polyester film may be reduced, and sufficient adhesion to the polyester film may not be obtained. When used in a film, the polystyrene film may be dissolved. In this invention, the effect of the adhesive improvement with respect to a polyester-type film is acquired by mixing an ester-type solvent in a solvent.

  The content of the total solvent of the present invention with respect to the entire printing ink is 20 to 70% by weight, although it varies depending on the presence or absence of the colorant and the type.

  Coloring agents such as dyes and pigments are added to the printing ink of the present invention as necessary, for example, when white ink or color ink is used. Of these, organic and inorganic color pigments are preferably used. Examples of the pigment used include white pigments such as titanium oxide (titanium dioxide), indigo (blue) pigments such as copper phthalocyanine blue, red pigments such as condensed azo pigments, yellow pigments such as azo lake pigments, carbon black, Aluminum flakes, mica (mica), etc. can be selected and used according to the application. In addition, extender pigments such as alumina, calcium carbonate, barium sulfate, silica, and acrylic beads can also be used as pigments for the purpose of adjusting gloss.

  The average particle diameter of the pigment (when forming an aggregate, the particle diameter of the aggregate, so-called secondary particle diameter) is, for example, 0.01 to 1 μm, preferably 0.1 to 0.5 μm. Preferably it is 0.2-0.5 micrometer. If the average particle size is less than 0.01 μm, the decorative property may be insufficient. If it exceeds 1 μm, so-called “plate fog” (printing failure due to defective ink scraping of portions other than the image area on the plate) during gravure printing. ) May occur. The content of the pigment can be arbitrarily designed depending on the type of pigment and the concentration of the target color, but is preferably about 0.1 to 60% by weight, more preferably 1 to 40% by weight based on the total weight of the printing ink. %.

  When the printing ink of the present invention is used as a white printing ink, any of rutile type (tetragonal high temperature type), anatase type (tetragonal low temperature type), and brookite type (orthorhombic crystal) may be used. However, for example, titanium oxide particles “Taipeke Series” manufactured by Ishihara Sangyo Co., Ltd., titanium oxide “JR Series” manufactured by Teika Co., Ltd., and the like are available. In addition, the content of titanium oxide in the white printing ink of the present invention is preferably 20 to 60% by weight, more preferably 30 to 50%, based on the total weight of the printing ink, from the viewpoint of concealability and suppression of coarse protrusion formation. % By weight.

  Moreover, the printing ink of the present invention may contain a lubricant as required. Examples of the lubricant herein include various waxes such as polyolefin wax such as polyethylene wax, fatty acid amide, fatty acid ester, paraffin wax, polytetrafluoroethylene (PTFE) wax and carnauba wax. Furthermore, additives other than the above, such as lubricants, anti-settling agents, plasticizers, dispersion stabilizers, matting agents, fillers, antioxidants, ultraviolet absorbers, antistatic agents and the like may be included as necessary. .

  The printing ink of the present invention is produced by mixing the acrylic resin, cellulose resin, solvent and pigment. When other additives are used, they are mixed at the same time. The mixing can be carried out using a known and common mixing method, and is not particularly limited. , Sand mills, ball mills, bead mills, line mills, kneaders and the like are used. The mixing time (retention time) during mixing is preferably 10 to 120 minutes. The obtained ink composition may be used after filtration, if necessary.

  The viscosity (23 ± 2 ° C.) of the printing ink of the present invention is not particularly limited. For example, when it is applied by gravure printing, it is preferably 10 to 2000 mPa · s, more preferably 20 to 500 mPa · s. is there. When the viscosity exceeds 2000 mPa · s, the gravure printability may be lowered, and “decrease” or the like may occur, and the decorating property may be lowered. On the other hand, when the viscosity is less than 10 mPa · s, the storage stability may be deteriorated, for example, the pigment or the additive may easily settle. The viscosity of the printing ink can be controlled by the type of binder resin, the amount added, the thickener, the thickener, and the like. In the present specification, “viscosity” is JIS Z unless otherwise specified, using an E-type viscometer (conical plate-type rotational viscometer) under the conditions of 23 ± 2 ° C. and cylinder rotation speed of 50 rotations. The value measured according to 8803 is meant.

  Cellulosic resins such as nitrocellulose used in the printing ink of the present invention generally have a property of being easily precipitated in an organic solvent (particularly a solvent having a high alcohol content). Therefore, when the resin is used by dissolving in a general alcohol solvent and ester solvent mixed solvent, the ester solvent in the mixed solvent (for example, Ethyl acetate) volatilizes earlier than alcoholic solvents (for example, isopropyl alcohol), resulting in a change in composition such as an increase in the alcohol concentration of the solvent and precipitation of the cellulose resin, resulting in poor ink stability and long time It had a problem that it could not be used. On the other hand, in the present invention, since a low-volatile solvent is used in the mixed solvent, the low-volatile solvent is difficult to volatilize even when used for a long time. (Sudden increase in concentration, etc.) hardly occur and the precipitation of the cellulose resin is suppressed, so that the ink stability is improved and the printing ink is suitable for long-time use (long run). Also, when printing ink is applied, leveling defects such as coating unevenness due to precipitation of the cellulose-based resin in the drying process are improved.

  The printing ink of the present invention has high ink stability and good adhesion to a plastic film. Particularly when it contains a lower alcohol, an ester solvent, a low volatility solvent, a polyester film, polystyrene Since it exhibits good adhesiveness to any of the system films, it is preferably used as a printing layer for plastic labels. In particular, it is preferably used as a combined ink for forming a printing layer by gravure printing or flexographic printing on polyester-based and polystyrene-based plastic films.

  By applying the printing ink of the present invention to at least one surface of a plastic film (substrate film), and heating and drying to remove the solvent, a printing layer made of the printing ink of the present invention is formed, thereby forming a plastic label. Is obtained. Since the printing ink of the present invention has excellent adhesion to a plastic film, the printing layer can be provided on the surface layer of the plastic film without any other layers.

  The kind of the plastic film used for the plastic label of the present invention is not particularly limited, but can be appropriately selected from polyester-based films, polystyrene-based films and the like according to required physical properties, applications, costs, and the like.

  Examples of the polyester resin that forms the polyester film include various polyesters composed of a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 5-t-butylisophthalic acid, 4,4′-biphenyldicarboxylic acid, trans-3,3′-stilbene dicarboxylic acid, and trans-4,4. '-Stilbene dicarboxylic acid, 4,4'-dibenzyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2, 7-naphthalenedicarboxylic acid, 2,2,6,6-tetramethylbiphenyl-4,4′-dicarboxylic acid, 1,1,3-trimethyl-3-phenylindene-4,5-dicarboxylic acid, 1,2- Aromatic dicals such as diphenoxyethane-4,4′-dicarboxylic acid, diphenyl ether dicarboxylic acid, and substituted products thereof Acid; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, Aliphatic dicarboxylic acids such as heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, icosanedioic acid, docosanedioic acid, 1,12-dodecanedioic acid, and their substitutions; 1,4-decahydronaphthalenedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 2,6-decahydronaphthalenedicarboxylic acid, cis-1,4-cyclohexanedicarboxylic acid, trans-1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and these And alicyclic dicarboxylic acids such as substitution products thereof. These dicarboxylic acid components can be used alone or in combination of two or more.

  Examples of the diol component include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,2 -Dimethyl-1,3-propanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,8-octane Aliphatic acids such as diol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2,4-dimethyl-1,3-hexanediol, 1,10-decanediol, polyethylene glycol, polypropylene glycol Diol; 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4 Cycloaliphatic diols such as cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol; 2,2-bis (4′-β-hydroxyethoxydiphenyl) propane, bis (4′- Examples thereof include ethylene oxide adducts of bisphenol compounds such as β-hydroxyethoxyphenyl) sulfone and aromatic diols such as xylylene glycol. These diol components can be used alone or in combination of two or more.

  In addition to the above, the polyester-based resin includes oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid; monocarboxylic acids such as benzoic acid and benzoylbenzoic acid; and polyvalent carboxylic acids such as trimellitic acid. Structural units such as monohydric alcohols such as polyalkylene glycol monomethyl ether; polyhydric alcohols such as glycerin, pentaerythritol and trimethylolpropane may be included.

  The polyester resin used in the present invention is not particularly limited, but terephthalic acid is used as the dicarboxylic acid component, polyethylene terephthalate (PET) using ethylene glycol as the diol component, and 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component. Poly (ethylene-2,6-naphthalenedicarboxylate) (PEN) using ethylene glycol as the diol component, terephthalic acid as the dicarboxylic acid component, ethylene glycol as the diol component, 1,4- A copolymer polyester (CHDM copolymerized PET) using cyclohexanedimethanol (CHDM) as a copolymerization component and dicarboxylic acid-modified PET (modified with terephthalic acid as a main component and isophthalic acid and / or adipic acid) are preferable. From the viewpoint of cost, productivity, etc., PET is particularly preferable. Furthermore, diethylene glycol and neopentyl glycol may be copolymerized from the viewpoint of improving low temperature shrinkage.

  The polystyrene resin that forms the polystyrene film includes, for example, styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, p-isobutylstyrene, and pt-butyl as constituent monomers. The resin is not particularly limited as long as it is a resin containing one or more styrene monomers such as styrene and chloromethylstyrene and exhibiting film forming properties. Examples of such polystyrene resins include general polystyrene (GPPS), which is a homopolymer of styrene, a homopolymer or copolymer of styrene monomers; a mixture of polystyrene and synthetic rubber (for example, polybutadiene or polyisoprene), High impact polystyrene (HIPS) with styrene grafted on synthetic rubber; styrene monomer and conjugated dienes such as butadiene and isoprene, such as styrene-butadiene-styrene (SBS) block copolymer Styrene-conjugated diene copolymer that is a polymer (particularly a block copolymer); Styrene-polymerizable unsaturated carboxylic acid that is a copolymer of a styrene monomer and a (meth) acrylate monomer Acid ester copolymer; styrene-conjugated diene-polymerizable unsaturated carboxylic acid ester copolymer; A rubbery elastic material is dispersed in a continuous phase of a copolymer of a monomer and a (meth) acrylic acid ester monomer, and the copolymer is graft-polymerized on the rubbery elastic material. -High impact polystyrene (graft TIPS) etc. are mentioned.

  The plastic film may be a single-layer film or a laminated film in which a plurality of film layers are laminated according to required physical properties, applications, and the like. In the case of a laminated film, the surface layer resin to be printed is preferably a polyester resin or a polystyrene resin, and the non-printed layer may be a film layer made of a different resin. For example, a three-layer laminated film consisting of a central layer and a surface layer (inner layer, outer layer) or a five-layer laminated film having an adhesive layer between the central layer and the surface layer, where the central layer is a polyolefin resin such as polypropylene (PP) A film made of a polystyrene resin and having a surface layer made of a polyester resin or a polystyrene resin may be used. Moreover, you may use any of an unstretched film, a uniaxially oriented film, and a biaxially oriented film according to a required physical property, a use, etc. In particular, when the plastic label is a shrink label, a uniaxial or biaxially oriented film (shrink film) is often used, and in particular, either the film width direction or the longitudinal direction (the circumferential direction of the label). In general, a film that is strongly oriented in the direction (a film that is substantially uniaxially stretched in the width direction) is generally used.

  The plastic film can be produced by a conventional method such as melt film formation or solution film formation. It is also possible to use a commercially available plastic film. The surface of the plastic film may be subjected to conventional surface treatment such as corona discharge treatment or primer treatment, if necessary.

  The heat shrinkage rate (90 ° C., 10 seconds) of the plastic film is not particularly limited. For example, when the plastic label is used for a shrink label, the longitudinal direction is −3 to 15% from the viewpoint of shrink workability and the like. The width direction is preferably 20 to 80%.

  Commercially available products may be used as the plastic film of the present invention. For example, “S7042” (polyester film) manufactured by Toyobo Co., Ltd .; “BS55S” (polystyrene film) manufactured by CI Kasei Co., Ltd .; ) “DL” manufactured by Gunze Co., Ltd. and “HGS” manufactured by Gunze Co., Ltd. (a laminated film in which the surface layer is a polyester resin and the center layer is a polystyrene resin).

  The plastic label of the present invention varies depending on the type and physical properties of the plastic film as the base material, but it is a shrink label, an in-mold label, a tack label, a roll label (a wrap-type glued label), a thermal adhesive label, and a cap seal. Etc. can be used. Among these, it is particularly preferably used as a shrink label or a cap seal from the viewpoint of tough adhesiveness and good process followability.

  The plastic label is generally attached to a container and used as a labeled container. Such containers include, for example, soft drink bottles such as PET bottles, milk containers for home delivery, food containers such as seasonings, alcohol beverage bottles, pharmaceutical containers, containers for chemical products such as detergents and sprays, cups, etc. This includes noodle containers. Also, the material of the container includes plastic such as PET, glass, metal and the like. In addition, the said plastic label may be used for adherends other than a container.

[Manufacturing and processing plastic labels]
Production of a plastic label using the printing ink of the present invention, processing of the plastic label, and attachment to a container can be performed, for example, as follows. In addition, although an example of the shrink label which used the shrink film as a plastic film below is shown, this invention is not limited to this.

  By applying the printing ink of the present invention on at least one surface of the plastic film and drying, a printed layer can be provided to produce a plastic label. The above coating and drying process may be performed during the plastic film manufacturing process (dry coating, in-line coating) or after film formation (off-line coating). From the viewpoint of processability, off-line coating is preferred. Moreover, you may provide layers other than the printing layer of this invention as needed.

(Manufacture of plastic labels)
As a method for applying the printing ink on the plastic film, gravure printing, flexographic printing, or inkjet printing method is preferable from the viewpoint of cost, productivity, printing decoration, and the like, and gravure printing method is particularly preferable. Moreover, when heating and drying the applied ink layer, a general heating apparatus capable of heating in-line can be used. From the viewpoint of safety, a hot air heater or the like can be preferably used. The heating temperature is preferably 30 to 70 ° C., and particularly in the case of a shrink film, 40 to 60 ° C. is preferable from the viewpoint of drying efficiency and suppression of film deformation. In the case of forming a multilayer print layer, such as in the case of overprinting, the above-described application / drying process may be repeated.

  The long plastic label obtained as described above is slit into a predetermined width and wound into a roll to form a plurality of rolls.

(Processing of plastic labels)
While feeding one of the rolls, the long plastic label is formed into a cylindrical shape so that the width direction is the circumferential direction. Specifically, a long plastic label is formed into a cylindrical shape, and a solvent or adhesive such as tetrahydrofuran (THF) or the like (hereinafter referred to as “THF”) is formed on one side edge of the label in a band shape in the longitudinal direction. Adhesive, etc.) is applied to the inner surface, rolled into a cylindrical shape, and the adhesive, etc. application part is overlapped with the position of 5-10 mm from the other side edge part and adhered to the outer surface (center seal). A cylindrical plastic label continuous body is obtained to obtain a long cylindrical plastic label. In addition, it is preferable that the printing layer is not provided in the part which apply | coats said adhesive agent etc., and the part to adhere | attach.

  In the case where a perforation for label excision is provided, a perforation having a predetermined length and pitch is formed in the longitudinal direction. The perforation can be applied by a conventional method (for example, a method of pressing a disk-shaped blade having a cut portion and a non-cut portion repeatedly formed around it, a method using a laser, or the like). The process stage for perforating can be appropriately selected after the printing process and before and after the cylindrical processing process.

(Mounting on container)
Finally, after cutting the long cylindrical plastic label obtained above, it is attached to a predetermined container, and the label is contracted by heat treatment, and a container with a label is prepared by closely contacting the container. The above long cylindrical plastic label is supplied to an automatic label mounting device (shrink labeler), cut to the required length, and then externally fitted into a container filled with the contents, and a hot air tunnel or steam tunnel at a predetermined temperature is attached. Passed or heated with radiant heat such as infrared rays to cause heat shrinkage and adhere to the container to obtain a labeled container. Examples of the heat treatment include treatment with steam at 80 to 100 ° C. (passing through a heating tunnel filled with steam and steam).

[Methods for measuring physical properties and methods for evaluating effects]

(1) Printability The printing inks obtained in the examples and comparative examples were printed on one side of a polystyrene (OPS) film (manufactured by CI Kasei Co., Ltd., “BS55S”: thickness 50 μm) with 60 lines of engraving and a plate depth of 30 μm. The whole surface was subjected to gravure printing at a process speed of 300 m / min, and dried at 50 ° C. using a hot air dryer to obtain a plastic label sample (OPS). The thickness of the printed layer after drying was about 3 μm.
Further, on one side of a polyester (PET) -based shrink film (Toyobo Co., Ltd., “S7042”: thickness 45 μm), using a gravure plate with 60 engravings and a plate depth of 30 μm, a process speed of 300 m / min, Full-surface gravure printing was performed, and drying was performed at 50 ° C. using a hot air dryer to obtain a plastic label sample (PET). The thickness of the printed layer after drying was about 3 μm.
The formation state, printing plate and ink pan of the printed layer of the plastic label sample (OPS, PET) obtained above were observed visually. Printing suitability such as plate covering, doctor cut, ink, and skinning was judged according to the following criteria.
○: Plate cover, doctor cut, ink is removed, and there is no skinning.
Δ: Plate cover, doctor cut, ink is taken, and there is some skinning, but it can be used as printing ink.
X: Plate cover, doctor cut, ink is taken, there is skinning, and it cannot be used as printing ink.

(2) Adhesiveness (tape peeling test)
The test was performed according to JIS K 5600, except that no cross cuts were made on the grid. A cellophane adhesive tape (manufactured by Nichiban Co., Ltd., width 18 mm) was applied to the ink-printed surface of the plastic label sample (OPS, PET) obtained in the same manner as (1), and peeled in the direction of 90 degrees. In an area of 5 mm × 5 mm, the remaining area of the printed layer was observed and judged according to the following criteria.
○: The remaining area of the printing layer is 99% or more of the whole. Δ: The remaining area of the printing layer is 90% or more and less than 99%. X: The remaining area of the printing layer is less than 90% of the whole. Adhesion was judged.

(3) OPS Film Deterioration Inhibitory Property Ink was applied to a flat OPS film (manufactured by C-I Kasei Co., Ltd., “BS55S”: thickness 50 μm) by hand drawing with a bar coater (# 7). The film state at that time was evaluated according to the following criteria.
○: The film is flat or slightly curled.
×: The film is greatly curled or torn.

(4) Blocking resistance The ink printed surface and the non-printed surface of the plastic label sample (OPS, PET) obtained in the same manner as in (1) were superposed and pressurized for 420 seconds under conditions of a pressure of 10 MPa and room temperature. . Thereafter, the peel strength was measured by a T-type peel test (peel rate 200 mm / min) according to JIS K 6854-3, and evaluated according to the following criteria.
○: Both the OPS film and the PET film have no ink peeling and the peel strength is less than 0.1 N / 15 mm.
Δ: Ink does not peel at all, but at least one of the OPS film and the PET film has a peel strength of 0.1 N / 15 mm or more.
X: The ink peels off at least one of the OPS film and the PET film.

(5) Aggregation inhibiting property of pigment (titanium oxide) 100 g of ink was weighed in a polypropylene bottle and allowed to stand at room temperature for 24 hours. Thereafter, the result of scooping the bottom of the bottle with a spatula was evaluated according to the following criteria.
○: There is almost no precipitate.
X: Precipitate exists.

(6) Ink stability A dilute solvent consisting of 50% isopropyl alcohol and 50% ethyl acetate (both by weight) was added to the ink, and the time was adjusted to 17 seconds with Zahn Cup # 3. Further, a dilution solvent of 50% by weight of the initial ink weight was added to the ink. The state of the diluted ink was visually observed, and the viscosity was measured with Zahn Cup # 3. Evaluation was made according to the following criteria.
○: There is no problem of phase separation and viscosity increase, and it can be used as an ink.
Δ: Some phase separation and viscosity increase, but can be used as printing ink.
X: Phase separation and viscosity increase, and cannot be used as printing ink.

(7) Film layer thickness, printing layer thickness The film thickness was measured using a stylus type thickness gauge. The printed layer thickness was measured by using a three-dimensional microscope (VK8510 manufactured by Keyence Corporation) for the level difference between the portion provided with the printed layer (coated surface) and the portion not provided with the printed layer (non-coated surface).

  EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
As solids, acrylic resin (Mitsubishi Rayon Co., Ltd., “Dynar GR5679”, weight average molecular weight 30000, Tg 40 ° C.), nitrocellulose resin (manufactured by Bergerac NC, “LIG 1/2”, nitrification degree 10 0.7 to 11.4%, polymerization degree 80 to 95), pigment (manufactured by Teika Co., Ltd., titanium oxide “JR-800”), wax (“LANCO PP 1362D” manufactured by LUBRIZOL), ethyl acetate, isopropyl Alcohol and propylene glycol monomethylate (specific evaporation rate 71) were blended in the blending amounts shown in Table 1, and dispersed with a homodisper to obtain a printing ink (white printing ink). And the solvent content are mixed as 1: 1.

Examples 2, 3 and Comparative Examples 1-3
As shown in Table 1, printing ink was obtained in the same manner as in Example 1 except that the kind of the low-volatile solvent and the ratio of the solvent were changed.

  As can be seen from Table 1, printing inks (Examples) in which the content of the low-volatile solvent in the solvent is within the scope of the present invention are adhesiveness, detergency of polystyrene film deterioration, blocking resistance, and ink stability. It was excellent in printability and pigment aggregation inhibition. On the other hand, when a solvent that does not contain a low-volatile solvent is used (Comparative Example 1), the ink stability and printability are reduced, and when the content of the low-volatile solvent is large (Comparative Examples 2 and 3). Blocking resistance decreased.

Examples 4-6
As shown in Table 2, a printing ink was obtained in the same manner as in Example 1 except that an acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd.) having a different glass transition temperature (Tg) was used.

  As can be seen from Table 2, the printing inks (Examples) were excellent in adhesiveness, polystyrene film deterioration inhibition, blocking resistance, ink stability, printability, and pigment aggregation inhibition.

Examples 7-10
As shown in Table 3, printing inks were obtained in the same manner as in Example 1 except that acrylic resins having different weight average molecular weights (Mw) (Mitsubishi Rayon Co., Ltd.) were used.

  As can be seen from Table 3, the printing inks (Examples) were excellent in adhesion, polystyrene film deterioration inhibition, blocking resistance, printability, and pigment aggregation inhibition.

Examples 11-13, Comparative Example 4
As shown in Table 4, a printing ink was obtained in the same manner as in Example 1 except that the blending ratio of the acrylic resin and the nitrocellulose resin was changed.

  As can be seen from Table 4, printing inks (Examples) using acrylic resins and nitrocellulose resins are adhesive, polystyrene film deterioration inhibition, blocking resistance, ink stability, printability, and pigment aggregation inhibition. It was excellent in nature. On the other hand, when the nitrocellulose resin was not used (Comparative Example 4), the blocking resistance of the printed layer was lowered.

Examples 14 and 15
As shown in Table 5, a nitrocellulose resin having a polymerization degree of 55 to 70 (manufactured by Bergerac NC, “LIG 1/4”) and a nitrification degree of 11.5-12.2%. A printing ink was obtained in exactly the same manner as in Example 1, except that the resin was changed to a nitrocellulose resin (manufactured by Bergerac NC, “HIG 1/2”).
The obtained printing ink was excellent in adhesiveness, polystyrene film deterioration inhibition, blocking resistance, ink stability, printability, and pigment aggregation inhibition.

Claims (5)

  A printing ink comprising an acrylic resin, a cellulose resin, and a solvent containing 0.1 to 30% by weight of a low-volatile solvent having a specific evaporation rate of 20 to 100 with respect to the total solvent.   The printing ink according to claim 1, wherein the acrylic resin has a weight average molecular weight of 8000 to 50,000 and a glass transition temperature of 35 to 80 ° C.   The cellulosic resin is a nitrocellulose resin, and a blending ratio (the former / the latter) of the acrylic resin and the nitrocellulose resin is 50/50 to 95/5 (weight ratio). Printing ink.   The printing ink according to any one of claims 1 to 3, which is an ink for gravure printing or flexographic printing.   The plastic label which has a printing layer formed by apply | coating the printing ink of any one of Claims 1-4 to the at least single side | surface of a polyester-type plastic film or a polystyrene-type plastic film, and drying.