JP2537391B2 - Printed material for low-temperature shrinkable label and PET container heat-shrinkable to form a label - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low-temperature shrinkable label print or the like, which is used as a label by printing a printing ink composition on a low-temperature shrinkable polystyrene film, heat-shrinking the same. is there.

<Prior Art and Its Problems> Today, as various containers in the fields of liquid foods, cosmetics, etc., paper containers, steel cans, aluminum cans, glass containers, plastic containers, etc. are used while making the most of their respective characteristics. The surfaces of these various containers are printed to display the contents. Among the various containers described above, the paper container has extremely high printing efficiency because it is molded after necessary printing is performed. However, in the case of other containers, since it is molded in a special shape in advance, the normal printing method cannot be applied, and a label print is attached, or a special printing method such as the screen method or the octopus printing method is used. Or, a special method for cans is used and printed directly on molded containers. However, these methods have very low work efficiency or are not suitable for high-mix low-volume production.

Therefore, in recent years, so-called shrink wrapping has been widely used in which a uniaxially stretched film is used as a material to be printed, and a cylindrical printed matter is attached to the container surface by heat shrinkage to form a label.

Conventionally, as a film for this application, a vinyl chloride film has been mainly used, but since a large amount of chlorine gas is generated during the incineration process, which is becoming a pollution problem, a uniaxially stretched polystyrene film for the purpose of devinyl chloride. (OP
The number of heat shrink labels using S) is increasing.

On the other hand, the problem of glass container damage or recycling,
Due to the so-called can pollution problem of steel cans and aluminum cans, plastics, especially polyester (PE
T) The popularity of containers is remarkable. When used in a glass container, etc., there is no special restriction even if the film has a high heat shrink temperature, but the conventional OPS is used as the label of the PET container, and the PET container itself is thermally deformed when heat shrinks, so for PET containers Uses a low temperature shrink type OPS that can be installed at lower temperatures.

This type of low temperature shrinkage type OPS has significantly lower solvent resistance than conventional OPS for glass containers. For example, when printing ink for OPS for glass containers is printed on low-temperature shrinkage type OPS, the film deteriorates due to solvent attack, and shrinkage over time, film strength reduction (elongation / tensile strength), cracks, etc. occur and it can be used. It disappeared.

Therefore, it is necessary to design a solvent composition that does not deteriorate the film, that is, an alcohol-rich ink, in the printing ink for low-temperature shrinkage type OPS. Is significantly reduced, resulting in pigment dispersibility,
It deteriorated the stability of the ink over time and printability such as sowing, doctor breakage, and swimming.

Therefore, the present invention is intended to provide a low-temperature shrinkable label printed matter or the like using the low-temperature shrinkable polystyrene film printing ink composition which does not have the above-mentioned problems.

<Means for Solving the Problems> That is, according to the present invention, a low temperature heat-shrinkable polystyrene film is provided with a pigment, an alkyl ester of an aliphatic alcohol having a side chain of 3 to 8 carbon atoms and (meth) acrylic acid 50 to 95.
% By weight, solution polymerization of a monomer mixture consisting of 5 to 25% by weight of a hydroxyalkyl ester of (meth) acrylic acid and 0 to 45% by weight of another vinyl monomer,
Acrylic resin having a molecular weight of 30,000 to 100,000, hydroxyl value of 20 to 110, glass transition temperature (Tg) of 35 to 65 ° C, 50 to 95% by weight, cellulose resin, 5 to 25% by weight, and a resin compatible with them 0 to A printed product for a low-temperature shrinkable label, which comprises printing a printing ink composition mainly composed of a resin consisting of 45% by weight (solid content ratio) and an organic solvent containing at least 50% by weight of a lower alcohol having 1 to 4 carbon atoms. It is also intended to provide a low-temperature heat-absorption label printed matter (claim 2) in which the alkyl ester as the reaction component of the acrylic resin of the printing ink composition is isobutyl methacrylate. Furthermore, the present invention provides the low-temperature shrinkable label print according to claim 1 or 2 with PE.
An object of the present invention is to provide a PET container (Claim 3) mounted on a T container by heat shrinkage.

Hereinafter, the printing ink composition for heat-shrinkable polystyrene film according to the present invention will be described in more detail.

First, the low-temperature shrinkable polystyrene flume, which is the printing medium used in the low-temperature heat-shrinkable label printed matter according to the present invention, will be described.

Shrink film is obtained by treating an unstretched film with various stretching devices and imparting a well-balanced shrinkage ratio in the vertical and horizontal directions.In the case of a shrinkable polystyrene film used for shrink labels, the normal temperature is about 90 to 130 ° C. The uniaxially stretched OPS that shrinks in the past has been used. The low-temperature shrinkable polystyrene film that is particularly targeted in the present invention has a temperature at the time of 45% shrinkage of 10 to 20 ° C. lower than that of the conventional OPS, and was set to match the heat resistance of the PET container. It is a thing.

This low-temperature shrinkable polystyrene film is significantly inferior in solvent resistance to conventional OPS, and is easily attacked by aromatic hydrocarbon-based and ester-based solvents that have been widely used as ink solvents in the past, and alcohol-based. It requires the use of a large amount of solvent. Examples of typical low-temperature shrinkage OPSs that are commercially available include Asahi Kasei's Sun Veil, CI Kasei's EPS-35, and Mitsubishi Plastics' TS-164.

Now, the ink of the present invention applied to the above film is a printing ink composition mainly composed of a pigment, a resin and an organic solvent, and mainly contains a mixture of a specific acrylic resin and a cellulose resin and a lower alcohol. It is characterized by using an organic solvent.

First, as the specific acrylic resin, monomers 50 to 95 which are esterified products of (meth) acrylic acid such as isobutyl methacrylate and a side chain alcohol having 3 to 8 carbon atoms are used.
An acrylic resin obtained by solution polymerization of a monomer mixture consisting of 5% by weight, 5 to 25% by weight of a monomer which is a hydroxyalkyl ester of (meth) acrylic acid, and 0 to 45% by weight of another vinyl monomer can be used.

Specific examples of the esterified product of (meth) acrylic acid and a side chain alcohol having 3 to 8 carbon atoms include isopropyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, and 2-ethylhexyl methacrylate.

These ester compounds are 50 to 95% by weight in the monomer component.
It is necessary to contain.

In addition, specific examples of the monomer corresponding to the hydroxyalkyl ester having 3 to 8 carbon atoms include 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and hexylene. Examples thereof include (meth) acrylic acid esters of glycol, and it is necessary to use 5 to 25% by weight in the monomer component. In addition, vinyl monomers other than the above can be used in combination, if necessary, and can be used in the range of 0 to 45% by weight in the monomer components. Examples of these vinyl monomers include esters of (meth) acrylic acid other than the above, for example, esters having a linear alkyl group such as methyl, ethyl, n-propyl, n-butyl, hexyl, decyl and lauryl. You can do it.

Further, at least one of unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, α, β unsaturated dicarboxylic acids such as itaconic acid, fumaric acid and maleic acid, N-methylol acrylamide and N-butoxymethyl acrylamide. An acrylic acid amide derivative containing an N-substituted methylol group, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate,
Aminoalkyl esters of (meth) acrylic acid such as dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate and dipropylaminopropyl (meth) acrylate, acrylic acid or methacrylic acid of glycols such as diethylene glycol and dipropylene glycol. Examples thereof include mono- or diesters. Among these exemplified vinyl monomers, those containing, as a main component, a monomer mixture containing isobutyl methacrylate and 2-hydroxyethyl methacrylate as essential components are preferable.

The desired acrylic resin can be obtained by solution polymerization of the above vinyl monomer mixture by a conventional method.

As the molecular weight of the acrylic resin, it is necessary to be in the range of 30,000 to 100.000, if it is less than the above range, the coating properties such as blocking property and adhesiveness become insufficient, and if it exceeds the above range, the solubility and the cellulose resin It becomes a problem in terms of compatibility. The hydroxyl value of the acrylic resin is 20 to 110.
It is also necessary to be within the above range, and if it is less than the above range, the compatibility with the cellulose resin becomes insufficient, and if it exceeds the above range, there is a problem in hot water resistance of the coating film.

Further, among the above-mentioned monomer components, when the ratio of the alkyl ester having a side chain is decreased, the solubility and compatibility with the cellulose resin become problematic, and when the ratio of the hydroxyalkyl ester exceeds the above range, the water resistance is increased. Is insufficient.

Further, the glass transition temperature (Tg) of the acrylic resin obtained from the above monomer is preferably in the range of 35 to 65 ° C, and when Tg is low, problems such as blocking occur, and when it is high, shrinkage follow-up with the film is followed. The property is insufficient and the printed surface tends to be distorted.

Next, examples of the cellulose resin which is another resin component include nitrocellulose, cellulose acetate propionate, and cellulose acetate butyrate.

The mixing ratio (solid content ratio) of the acrylic resin and the cellulose resin needs to be in the above range. When the ratio of the acrylic resin is small, the adhesiveness to the film, the shrinkage followability, and the ratio When the amount is large, problems occur in terms of blocking, pigment dispersibility, ink fluidity, and the like.

Further, one of the essential components, the organic solvent, needs to contain at least 50% by weight of a lower alcohol having 1 to 4 carbon atoms in the solvent component. Specific examples of the alcohol include methyl, ethyl, propyl, isopropyl,
Examples include alcohols such as butyl, s-butyl, t-butyl.

In addition, ethyl acetate, which has been used as a solvent for inks from the past, such as butyl acetate, toluene,
Solvents such as aromatics such as xylene, aliphatics such as hexane, and ketones such as methyl ethyl ketone can be used in combination.

Incidentally, when the use of the lower alcohol is below a specific range, the film is eroded, and the film is bleached / turbid,
Problems such as reduction in strength (elongation, tensile strength), cracks and the like occur.

Other materials used for the ink of the present invention include colorants selected from organic and inorganic pigments, rosin esters compatible with the above resins, resins such as alkylphenols,
Furthermore, as an additive, a plasticizer such as a fatty acid ester,
Watts, such as polyethylene and amide, antistatic agent,
Various activators such as pigment dispersants can be used.

When the printing ink according to the present invention is produced, it can be produced by using the above-mentioned various materials and various conventionally used dispersing / kneading machines.

As a printing method, with respect to the target film, it is possible to obtain a desired printed matter with a gravure or flexographic printing machine, and when using the obtained printed matter as a label or the like, tubing by means such as solvent sealing, It can be used as a shrink label by attaching it to a PET container or a glass container and then heating it to a shrinking temperature to heat-shrink the OPS film and bring it into close contact with the container.

When a PET container is used as the container, it is necessary to use a low temperature shrinkage type OPS as the film.

Hereinafter, the ink composition according to the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

<Examples> Acrylic resin production examples 1 to 15 According to the formulations shown in Table-1, acrylic resins are solution polymerized by a conventional method using a predetermined amount (weight ratio) of each monomer to produce. Regarding the obtained Resins 1 to 8 and Comparative Resins 1 to 7, the glass transition temperature and the hydroxyl value of each were added in the table, the compatibility with nitrocellulose when the solvent composition was different, and the heat resistance Aqueous property was evaluated and is also noted in the table. The methods for evaluating compatibility and hot water resistance will be described later.

As can be seen from the evaluation results in Table 1, Resins 1 to 8 obtained in Production Examples were excellent in compatibility with solvent systems rich in alcohol and hot water resistance. However, the comparative resins had problems in any of the above performances.

Mixing evaluation test with cellulose Using the resin 2 obtained in the acrylic resin production example, the adhesiveness to the OPS film and the pigment dispersibility in a solvent system containing 65% alcohol according to the ratio (solid content) shown in Table-2. And hot water resistance were evaluated, and the results are added to Table 2. The evaluation method will be described later.

As shown in Table-2, if the specified mixing ratio is exceeded,
It can be seen that the adhesiveness, pigment dispersibility, and hot water resistance are not sufficient.

Examples 1 to 4 and Comparative Examples 1 to 4 Resin 2, Resin 3, Resin 5 obtained in the acrylic resin production example
Resin 7 (Examples 1 to 4) and Comparative Resin 1, Comparative Resin 3,
12 parts by weight (solid content) of each of Comparative Resins 5 to 6 (Comparative Examples 1 to 4), 10 parts by weight of phthalocyanine pigment, 3 parts by weight of nitrified cotton (solid content), 2 parts by weight of plasticizer (acetate tributyl citrate). , 1 part by weight of polyethylene wax, 65 pairs of isopropyl alcohol and ethyl acetate as a solvent
71 parts by weight of a mixed solvent having a ratio of 35 is used to produce a gravure ink by kneading and dispersing in a conventional manner. In Comparative Examples 1 to 3 and 6, a mixed solvent having the above solvent composition, in which the resins were not compatible and the ratio of isopropyl alcohol and ethyl acetate was 35:65, which was the reverse ratio, was used. Each of the obtained inks was printed on the OPS with a gravure printing machine, and the degree of erosion of the film, adhesiveness, re-dissolvability,
The hot water resistance was evaluated and the results are shown in Table 3.

Evaluation method Compatibility: Acrylic resin and nitrified cotton are mixed in a ratio of 80:20 in each solvent, and evaluated by the stability of the resin solution and the degree of turbidity of the coating film.

Hot water resistance: resin solution or ink is made by Asahi Kasei OPS
After coating the film and sun veils and drying, put it into a PET container in tube form and heat it at 80 ° C for 15 minutes.
Evaluate based on the degree of transfer of resin or ink to PET containers and the degree of chalking of the coating film.

Adhesiveness: As an OPS film, Asahi Kasei's sun veils are used, a resin solution or ink is applied, and adhesiveness is evaluated by peeling cellophane tape.

Pigment dispersibility: The pigment dispersion is evaluated based on the color developability of the pigment, the gloss of the coating film and the dispersion stability.

Corrosion: Ink is applied to Asahi Kasei OPS film and sun veils and dried with hot air, and then the film is evaluated for scratches.

Re-dissolvability: Ink is applied to a stainless steel plate, dried, and immersed in the mixed solvent used for each ink to evaluate the solubility of the ink coating film.

In the above evaluation, in order of excellence,
Differentiated as ⊚, ○, Δ, and ×.

<Effects> As described above in Examples and the like, the low temperature shrinkable polystyrene film ink according to the present invention has sufficient printability without causing deterioration of the film when applied to the low temperature shrinkable OPS. It can be seen that the ink is excellent as a shrink label ink.

Further, the ink of the present invention can be sufficiently applied to the comparatively high temperature shrinkage OPS used for conventional glass containers and the like.

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Claims (3)

(57) [Claims] 1. A low-temperature shrinkable polystyrene film, a pigment,
50 to 95% by weight of an alkyl ester of an aliphatic alcohol having a side chain of 3 to 8 carbon atoms and (meth) acrylic acid,
Hydroxyalkyl ester of (meth) acrylic acid 5
Molecular weight 3 obtained by solution polymerization of a monomer mixture consisting of 25% by weight and 0 to 45% by weight of other vinyl monomers.
0,000-100,000, hydroxyl value 20-110, glass transition temperature (T
g) 50-95% by weight of acrylic resin in the range of 35-65 ° C,
It is mainly composed of a resin consisting of 5 to 25% by weight of a cellulose resin and a resin compatible with them of 0 to 45% by weight (solid content ratio) and an organic solvent containing at least 50% by weight of a lower alcohol having 1 to 4 carbon atoms. A low-temperature shrinkable label print, which is characterized by printing a printing ink composition. 2. The low-temperature shrinkable label printed matter according to claim 1, wherein the alkyl ester is isobutyl methacrylate as a reaction component of the acrylic resin of the printing ink composition. 3. A PET container in which the low-temperature shrinkable label printed matter according to claim 1 or 2 is heat-shrinked and mounted on a PET container.