Stock material or miscellaneous articles – Hollow or container type article – Shrinkable or shrunk
Reexamination Certificate
2002-01-25
2003-12-16
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Shrinkable or shrunk
C428S034900, C428S480000, C525S437000, C525S444000, C528S308000
Reexamination Certificate
active
06663928
ABSTRACT:
FILED OF INVENTION
The present invention relates to heat-shrinkable polyester films and particularly to heat-shrinkable polyester films suitable for label use. More specifically, it relates to heat-shrinkable polyester films for full labels on bottles, particularly for full labels on polyethylene terephthalate (PET) bottles, which will cause only rare occurrence of wrinkles, shrinkage spots and strains by heat shrinkage.
BACKGROUND OF THE INVENTION
For heat-shrinkable films, particularly heat-shrinkable films for labels on the barrels of bottles, there have mainly been used films made of polyvinyl chloride, polystyrene or other resins. However, for polyvinyl chloride, the evolution of a chlorine-containing gas in its incineration for disposal has become a problem, and for polyethylene, there is a problem that printing is difficult. Further, in the collection and recycling of PET bottles, labels of resins other than PET, such as polyvinyl chloride or polyethylene, should be separated. Therefore, attention has been paid to heat-shrinkable polyester films involving these problems.
In recent years, for recycling of PET bottles, colored bottles are not suitable for reuse, and therefore, many alternative plans have been studied. Among them is a method of using a non-colored bottle and allowing a colored label to shrink over the bottle.
However, when used as full labels on bottles, the conventional heat-shrinkable films may sometimes cause a problem in shrinkage finish. In the case of full labels on narrow-mouthed bottles having a large difference in bottle diameter between the mouths and the barrels, particularly such as beverage bottles, the conventional heat-shrinkable films exhibit insufficient shrinkage at the upper neck portions of the bottles. The heat-shrinkable films to be used for full labels on such bottles should have heat-shrinkage characteristics such as high shrinkability.
Thus in the case of full label use on bottles, the conventional heat-shrinkable films have insufficient performance.
For example, the films disclosed in JP 2000-169601 A exhibit high shrinkage, but have not yet reached a level requiring shrinkage finish.
SUMMARY OF THE INVENTION
The present invention, which can solve the above problems, has been made for the purpose of providing heat-shrinkable polyester films for full labels on bottles, particularly for full labels on PET bottles, which films are particularly used for full labels on PET bottles requiring excellent finish in appearance and will cause only rare occurrence of wrinkles, shrinkage spots and strains by shrinkage.
Thus the present invention is directed to heat-shrinkable polyester films, each having a heat shrinkability of 5-60% after treatment in hot water at 70° C. for 5 seconds and 65-95% after treatment in hot water at 85° C. for 5 seconds, both in the main shrinkage direction of the film, and 10% or lower after treatment in hot water at 85° C. for 5 seconds in a direction perpendicular to the main shrinkage direction of the film, the heat-shrinkage stress in the main shrinkage direction of the film being 13 MPa or smaller, and the film haze being lower than 10%, thereby attaining the above purpose.
DETAILED DESCRIPTION OF THE INVENTION
The dicarboxylic acid components constituting polyesters used in the present invention may include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and o-phthalic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid; and alicyclic dicarboxylic acids.
When aliphatic dicarboxylic acids (e.g., adipic acid, sebacic acid, decanedicarboxylic acid) are contained, their contents may preferably be lower than 3 mol %. For heat-shrinkable polyester films obtained by the use of polyesters containing these aliphatic dicarboxylic acids at 3 mol % or higher, their film stiffness in the high-speed fitting is insufficient.
The polyesters may preferably contain no three or more functional polycarboxylic acids (e.g., trimellitic acid, pyromellitic acid, their anhydrides). For heat-shrinkable polyester films obtained by the use of polyesters containing these polycarboxylic acids, their desired high shrinkability can hardly be attained.
The diol components constituting the polyesters used in the present invention may include aliphatic diols such as ethylene glycol, propanediol, butanediol, neopentyl glycol and hexanediol; alicyclic diols such as 1,4-cyclohexanedimethanol; and aromatic diols.
The polyesters used in the heat-shrinkable polyester films of the present invention may preferably be those having glass transition temperatures (Tgs) adjusted to 60-75° C. by the incorporation of at least one diol of 3-6 carbon atoms (e.g., propanediol, butanediol, neopentyl glycol, hexanediol).
For the purpose of obtaining heat-shrinkable polyester films exhibiting particularly excellent shrinkage finish, neopentyl glycol may preferably be used as one of the diol components.
The polyesters may preferably contain neither diols of 8 or more carbon atoms (e.g., octanediol), nor three or more functional polyhydric alcohols (e.g., trimethylolpropane, trimethylolethane, glycerin, diglycerin). For heat-shrinkable polyester films obtained by the use of polyesters containing these diols or polycarboxylic acids, their desired high shrinkability can hardly be attained.
The polyesters may preferably contain none of diethylene glycol, triethylene glycol, and polyethylene glycol, if possible. In particular, diethylene glycol may easily be formed as a by-product component in the polymerization of polyesters and therefore may easily be contained in the polyesters. For the polyesters used in the present invention, the diethylene glycol contents may preferably be lower than 4 mol %.
For the heat-shrinkable films of the present invention, polyesters meeting the above conditions may be used alone, or two or more such polyesters may be used in admixture.
When two or more polyesters are used in admixture, the acid component contents and the diol component contents of the mixed polyesters refer to the contents, relative to the total amount of all acid components and the total amount of all diol components, respectively, both of which are contained in the mixed polyesters, independently of whether or not transesterification has been carried out after the mixing.
The mode for using two or more polyesters in admixture may include, for example, the following cases:
1. PET/copolymerized PES
2. copolymerized PES/copolymerized PES
3. PET/copolymerized PES/copolymerized PES
Further, to improve the self-lubricating properties of heat-shrinkable polyester films, inorganic lubricants such as titanium dioxide, fumed silica, kaolin and calcium carbonate; or organic lubricants such as long-chain fatty acid esters may preferably be added. The heat-shrinkable polyester films of the present invention may further contain, if necessary, additives such as stabilizers, colorants, antioxidants, defoamers, antistatic agents and ultra-violet light absorbers.
For the heat-shrinkable polyester films of the present invention, amorphous polyesters may preferably be incorporated to attain high shrinkability. In addition to amorphous polyesters, polyester elastomers may preferably be incorporated at 5-24 wt %, more preferably at 10-24 wt %, still more preferably at 15-24 wt %, and particularly preferably 17-24 wt %. When the amounts of polyester elastomers are lower than 5 wt %, low temperature shrinkability is hardly expressed, and therefore, failures in shrinkage, such as wrinkles, will easily occur. In contrast, when the amounts of polyester elastomers are higher than 24 wt %, high shrinkability is hardly expressed, and therefore, failures in shrinkage, such as insufficient shrinkage at the necks of bottles, will easily occur.
Further, it has also been found that shrinkage stress in the shrinkage by heating may easily be reduced by the incorporation of polyester elastomers. Not too great amounts of amorphous polyesters incorporated bring about an easy reduction of shrinkage
Ito Hideki
Nagano Hiroshi
Tabota Norimi
Chen Vivian
Toyo Boseki Kabushiki Kaisha
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