JP2005173611A - Shrinkable label for plastic bottle and plastic bottle with shrinkable label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shrinkable label made of a polyester by which a liquid level of a content does not rise or the content does not overflow from a container mouth at the time of opening a stopper even when the shrinkable label is attached onto a square-shaped plastic vessel with a pressure reducing panel. <P>SOLUTION: The shrinkable label for a square-shaped plastic bottle with the pressure reducing panel is made of the polyester having 40 to 80% coefficient of thermal contraction in a direction X when treated at 90°C for 10 seconds and ≤10 MPa maximum shrinkage stress in the direction X when treated at 90°C for 10 seconds. The shrinkable label is put on the square-shaped plastic bottle with the pressure reducing panel as to cover a pressure reducing panel part and then is attached thereon by thermal shrinkage by steam. Thereby the plastic bottle with the shrinkable label in which the liquid level does not rise at the time of opening the stopper can be manufactured. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a shrink label for a square plastic bottle having a decompression panel, a plastic bottle with a shrink label in which a shrink label is attached to a square PET bottle having a decompression panel, and a method for producing the same.

  As a plastic bottle such as a PET (PET) bottle (polyethylene terephthalate bottle) for beverages such as coffee, a rectangular bottle having a polygonal shape such as a substantially square cross section has been recently used. Among these square plastic bottles, the bottles that are filled with the contents in a hot state absorb the reduced pressure on the side of the bottle so that the bottle does not deform even if the inside is in a reduced pressure state after cooling after capping, A concave decompression panel is provided for relaxation.

  However, when a polyester shrink label usually used for such a square bottle is attached to cover the decompression panel, the label presses the bottom of the recess of the decompression panel during heat shrinkage, and as a result, when the lid of the bottle is opened, There is a problem that the liquid level of the contents (inline) rises or the contents overflow from the mouth. In particular, this phenomenon often occurs recently because the thickness of the bottle has been reduced. When a shrink label other than polyester is used, the phenomenon is hardly observed, and when the bottle is opened, the reduced pressure is released and the bottle slightly swells outward, so that the liquid level of the contents slightly decreases.

  From the viewpoint of the consumer, the fact that the liquid level of the contents is lowered at the time of opening can be said to be evidence that the liquid level is surely sealed before opening, so the phenomenon that the liquid level rises as described above is not very preferable. Moreover, if the contents overflow, hands and clothes will be soiled.

Accordingly, an object of the present invention is to provide a polyester shrink label in which the liquid level of the contents does not rise or the contents do not overflow from the mouth even when attached to a rectangular plastic container having a decompression panel. There is.
Another object of the present invention is to provide a rectangular plastic with a shrink label that prevents the liquid level of the contents from rising or overflowing from the mouth when opening, even if a polyester shrink label is attached to cover the decompression panel. It is to provide a bottle and a method for producing the bottle.

  As a result of intensive studies to achieve the above object, the present inventors have used a polyester shrink label having a specific shrinkage characteristic. Even when the decompression panel portion is covered and attached to a square plastic bottle having a decompression panel, The present inventors have found that the liquid level of the contents can be prevented from rising or the contents can be spilled at the time of opening, and the present invention has been completed.

  That is, the present invention is a polyester shrink label having a heat shrinkage rate of 40 to 80% in one direction X when treated at 90 ° C. for 10 seconds, and the direction X when treated at 90 ° C. for 10 seconds. Provided is a shrink label for a square plastic bottle with a decompression panel, characterized in that the maximum shrinkage stress does not exceed 10 MPa.

The present invention also provides a plastic bottle with a shrink label, wherein the above-mentioned shrink label is attached to a square plastic bottle having a decompression panel so as to cover the decompression panel portion.
The present invention further provides a plastic bottle with a shrink label, characterized in that a square plastic bottle having a decompression panel is covered with the shrink label so as to cover the decompression panel portion and is thermally contracted by steam. Provide law.

According to the shrink label of the present invention, since it has a specific heat shrinkage characteristic, even when it is attached to a square plastic container having a decompression panel, the liquid level of the contents rises or the contents are not sealed when opened. Can be prevented from overflowing.
According to the square plastic bottle with the shrink label of the present invention, since the decompression panel is covered with the shrink label having the specific heat shrinkage characteristic, the liquid level of the content rises or the content overflows from the mouth when opening. Can be prevented.
According to the production method of the present invention, such a square plastic bottle with a shrink label can be efficiently produced.

  Hereinafter, the present invention will be described in detail with reference to the drawings as necessary. FIG. 1 is a schematic view showing an example of a process for attaching the shrink label 1 of the present invention to a square plastic bottle 2.

  The shrink label 1 is made of a polyester film, has a thermal shrinkage rate of 40 to 80% in one direction X when treated at 90 ° C. for 10 seconds, and the maximum in the direction X when treated at 90 ° C. for 10 seconds. The shrinkage stress does not exceed 10 MPa.

  The polyester includes 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, 2,2 Alicyclic diols such as 4,4-tetramethyl-1,3-cyclobutanediol; 2,2-bis (4′-β-hydroxyethoxydiphenyl) propane, bis (4′-β-hydroxyethoxyphenyl) sulfone, etc. Examples thereof include ethylene oxide adducts of bisphenol compounds 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 includes oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid; monocarboxylic acids such as benzoic acid and benzoylbenzoic acid; polyvalent carboxylic acids such as trimellitic acid; It may contain structural units such as monohydric alcohols such as alkylene glycol monomethyl ether; polyhydric alcohols such as glycerin, pentaerythritol and trimethylolpropane.

  In the preferred polyester of the present invention, terephthalic acid and ethylene glycol are used as the main components of the dicarboxylic acid component and the diol component, respectively, and isophthalic acid, phthalic acid, adipic acid, sebacic acid, 1,10-decane are used as copolymerization components. Copolyesters using diol components such as dicarboxylic acids such as dicarboxylic acids, diethylene glycol, neopentyl glycol, polyalkylene glycol, and 1,4-cyclohexanedimethanol are included.

  In such a copolyester, the proportion of terephthalic acid in the total dicarboxylic acid component constituting the polyester is generally 50 mol% or more (for example, about 50 to 99 mol%), preferably 70 mol% or more (70 to 97 mol). %). If the proportion of terephthalic acid is too small, the strength and solvent resistance of the film tend to be lowered. Further, in order to improve the heat shrinkability of the film, it is preferable to use an aliphatic dicarboxylic acid as the dicarboxylic acid component, for example, about 1 to 25 mol% of the entire dicarboxylic acid component constituting the polyester.

  The proportion of ethylene glycol in the entire diol component constituting the polyester is generally 40 mol% or more, preferably 50 mol% or more. If the proportion of ethylene glycol is too small, the strength and solvent resistance of the film tend to be lowered.

  The polyester can be produced by a known method such as a method of directly reacting a dicarboxylic acid component and a diol component, or a method of transesterifying an ester of a dicarboxylic acid component and a diol component.

  The shrink label 1 of the present invention may be composed of a single polyester or a mixture of two or more polyesters. Examples of a mixture of two or more polyesters include, for example, a blend polymer of polybutylene terephthalate (PBT), polyethylene terephthalate (PET), and polyethylene terephthalate containing an alicyclic diol such as cyclohexanedimethanol as a glycol component. Can be mentioned. In this blend polymer, the proportion of polybutylene terephthalate (PBT) is 5 to 40% by weight, preferably about 10 to 35% by weight, and the proportion of polyethylene terephthalate (PET) is 30 to 75% by weight, preferably 35 to 70%. The ratio of polyethylene terephthalate containing an alicyclic diol such as cyclohexanedimethanol as a glycol component is about 10 to 40% by weight, preferably about 15 to 35% by weight.

  The shrink label 1 of the present invention may be composed of either a single layer film or a multilayer film, and an overcoat layer may be provided on the surface for preventing damage or the like.

  The shrink label 1 of the present invention can be produced by forming by a known method such as an extrusion method or a calendering method, then stretching, and printing on at least one surface of the obtained film.

  Stretching can be performed by either a tenter method or a tube method. The stretching treatment is performed at an appropriate temperature in consideration of the glass transition temperature of the polyester constituting the film, and is 1.5 to 8 times in the direction corresponding to the circumferential direction of the container [usually the width direction (TD direction)], preferably It is performed by stretching about 4 to 5 times. In addition, if necessary, the stretching process can be performed at a low stretching ratio (for example, about 1.5 times or less) also in a direction [normally the length direction (MD direction)] orthogonal to the above direction. Moreover, after extending | stretching, the heat setting which normally passes a heating zone at about 60-90 degreeC for about 1-10 seconds is performed. The film thus obtained has an orientation in the main stretching direction and exhibits a large heat shrinkability in this direction.

  Printing can be performed by a conventional printing method such as gravure printing. The shrink label 1 of the present invention is cut into a long strip having a desired width after printing, and is rounded into a cylindrical shape so that the main stretching direction is a circumferential direction, for example, with the printing surface on the inside, and both ends are bonded. After bonding with an agent or the like, it is cut into a desired length as necessary and used as a cylindrical shrink label. The thickness of the shrink label 1 is generally about 25 to 70 μm, preferably about 40 to 50 μm.

  In the shrink label 1 of the present invention, the heat shrinkage rate when treated at 90 ° C. for 10 seconds is 40 to 80% in one direction X (direction corresponding to the circumferential direction of the container), preferably 65 to 75%. . When the heat shrinkage rate is less than 40%, the shrinkage is insufficient when the rectangular plastic bottle having the decompression panel portion is mounted, and the decompression panel portion cannot be tightly packed. Moreover, when the said heat shrinkage rate exceeds 80%, since a distortion arises in a label, it is unpreferable.

  The heat shrinkage ratio is, for example, the types and composition ratios of the dicarboxylic acid component and the diol component in the raw material polyester constituting the shrink label 1 (particularly, the ratio of the aliphatic dicarboxylic acid component), stretching conditions (stretching temperature, stretch ratio). Etc.), heat setting conditions (temperature, time, etc.) and the like can be appropriately adjusted within the above range.

  In the shrink label 1 of the present invention, the maximum shrinkage stress in the direction X when treated at 90 ° C. for 10 seconds is less than 10 MPa (for example, 2 MPa or more and less than 10 MPa), preferably less than 7 MPa (for example, 4 MPa or more, 7 MPa Less). When the maximum shrinkage stress exceeds 10 MPa, the shrink label 1 has a force to fasten the bottle 2, particularly the decompression panel portion 3, when it is attached to the square plastic bottle 2 with the decompression panel portion filled with the contents at a high temperature. It is too large, and the inside of the bottle is rather pressurized even after cooling. For this reason, when the bottle is opened, the liquid level in the bottle rises or the contents overflow from the mouth of the bottle. In contrast, when a shrink label having a maximum shrinkage stress of less than 10 MPa is attached to a hot-filled square plastic bottle 2 with a decompression panel, the shrink label 1 does not excessively tighten the bottle 2. Therefore, after cooling, the inside of the bottle is slightly depressurized due to a decrease in the volume of liquid and air in the bottle and dissolution of the air into the liquid, and the liquid level decreases when the bottle is opened.

  The maximum shrinkage stress is, for example, the molecular weight and crystallinity of the polyester constituting the film, the types and composition ratios of the dicarboxylic acid component and the diol component in the polyester, the stretching ratio during the stretching process, the temperature and time of the heat set, etc. Can be set within the above range by appropriately selecting.

 The square plastic bottle 2 is not particularly limited as long as it is a plastic bottle having a flat portion on the side (body) and provided with the decompression panel 3. A plastic bottle having a decompression panel 3 on four sides can be mentioned. As the material of the bottle, any material may be used as long as it has heat resistance enough to withstand hot filling (temperature 80 to 90 ° C.), and typical examples thereof include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Examples include polyester. The shape of the decompression panel 3 is not particularly limited as long as it can absorb the reduced pressure and suppress the deformation of the bottle. However, the decompression panel 3 has a substantially rectangular concave shape with a slightly raised convex portion at the center. There are many cases.

  The plastic bottle with the shrink label of the present invention is, for example, supplied with the shrink label 1 of the present invention formed into a cylindrical shape to an automatic label mounting device, cut into a required length, and then filled with the normal contents. It can be manufactured by continuously fitting the rectangular plastic bottle 2 having the decompression panel 3 including the decompression panel portion, and applying heat shrinkage by heating. The shrinkage of the shrink label 1 fitted to the bottle 2 may be performed by any known method. However, for example, a steam tunnel of about 80 to 100 ° C. is used because the temperature is evenly transmitted to improve the finish of the label. It is preferable to heat shrink by passing.

  In addition, when excessive stress is applied to the decompression panel provided in the lower half of the decompression panel formed on the plastic bottle, the level of rise in the liquid level is particularly large at the time of opening the plug. In particular, it is useful for coating a decompression panel formed in the lower half of such a bottle.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited by these Examples. The thermal shrinkage rate and the maximum shrinkage stress were measured by the following methods.

(Heat shrinkage)
The thermal contraction rate when the base film was immersed in hot water at 90 ° C. for 10 seconds was determined by the following formula. The direction X indicates the main stretching direction (width direction).
Thermal contraction rate (%) = [{(original length in direction X) − (length after immersion in direction X)} / (original length in direction X)] × 100

(Maximum shrinkage stress)
The base film is cut out so that the distance between chucks is 5 cm and the width is 3 cm, set in a tension detector, then immersed in hot water at 90 ° C. for 10 seconds, the contraction stress generated is measured, and the maximum value in between is maximum contraction Stress (MPa) was used.

Example A copolyester having terephthalic acid and ethylene glycol as the main components of a dicarboxylic acid component and a diol component is extruded, stretched 4.5 times in the width direction (TD direction), and heat set at 70 ° C. for 3 seconds. To make a base film having a thickness of 50 μm. One surface of this base film was subjected to gravure printing with a design consisting of eight colors using a reactive urethane-based ink, and then wound into a roll shape, as shown in Table 1, with four different heat shrinkage characteristics. Shrink labels (A, B, C and D) were obtained. In addition, the component composition of the base film of these four types of shrink labels is as follows.
Shrink label A: Blend polymer of 15 parts by weight of PBT, 65 parts by weight of PET, and 20 parts by weight of PET-G (polyethylene terephthalate containing cyclohexanedimethanol as a glycol component) (unidirectional stretch ratio is 4.5 to 6 times)
Shrink label B: Blend polymer of 20 parts by weight of PBT, 50 parts by weight of PET, and 30 parts by weight of PET-G (drawing ratio in one direction is 4.5 to 6 times)
Shrink label C: Blend polymer of 30 parts by weight of PBT, 40 parts by weight of PET, and 30 parts by weight of PET-G (drawing ratio in one direction is 4.5 to 6 times)
Shrink label D: Polyethylene terephthalate containing neopentyl glycol as glycol component (stretch ratio in one direction is 4.5-6 times)
After slitting the roll-shaped shrink label to a predetermined width to form a plurality of roll-shaped products, each roll-shaped product is rewound and rolled into a cylindrical shape so that the width direction of the base film is the circumferential direction. The parts were welded by heat to obtain a continuous cylindrical shrink label. The shrink label continuum is supplied to an automatic label mounting device, cut into each label, and hot filled with coffee (temperature 85 ° C.). As shown in FIG. 1, it was externally fitted to a 500 ml PET bottle and passed through a steam tunnel (temperature of 90 ° C.) and thermally contracted.
The coffee-filled PET bottles with the shrink labels are stored in the refrigerator (temperature 5 ° C.) and then taken out and opened. The change in the liquid level of the coffee at this time is visually observed and evaluated according to the following criteria. did. The results are shown in Table 1.
○: The liquid level was lowered.
X: The liquid level was constant or increased.

It is the schematic which shows an example of the process of mounting | wearing the square plastic bottle with the shrink label of this invention.

Explanation of symbols

1 Shrink label
2 Square plastic bottle
3 Depressurization panel

Claims (3)

  A polyester shrink label having a thermal shrinkage rate of 40 to 80% in one direction X when treated at 90 ° C. for 10 seconds, wherein the maximum shrinkage stress in the direction X when treated at 90 ° C. for 10 seconds is 10 MPa. Shrink label for square plastic bottle with decompression panel, characterized by not exceeding.   A plastic bottle with a shrink label, characterized in that the shrink label according to claim 1 is attached to a square plastic bottle having a decompression panel so as to cover the decompression panel portion. A method for producing a plastic bottle with a shrink label, comprising: mounting a shrink label according to claim 1 on a square plastic bottle having a decompression panel so as to cover the decompression panel portion and heat shrinking with steam.

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