Stock material or miscellaneous articles – Hollow or container type article – Shrinkable or shrunk
Reexamination Certificate
2001-10-02
2002-10-01
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Shrinkable or shrunk
C428S034900, C428S480000, C525S419000, C525S420000, C525S425000, C525S437000, C525S444000, C528S308000, C528S308600
Reexamination Certificate
active
06458437
ABSTRACT:
FILED OF INVENTION
The present invention relates to heat-shrinkable polyester films, and more particularly, it relates to heat-shrinkable polyester films suitable for full labels on bottles, particularly full labels on PET bottles, which exhibit, when used for full labels on bottles, good shrinkage finish involving only rare occurrence of wrinkles, shrinkage spots, strains and shrinkage failure during heat shrinkage, and which exhibit a low decrease in low temperature shrinkability after a lapse of time.
BACKGROUND OF THE INVENTION
For heat-shrinkable films, particularly used as labels on the barrels of bottles, films made of polyvinyl chloride or polystyrene have mainly been employed. However, polyvinyl chloride films have recently raised a serious problem on the evolution of chlorine-containing gases in the incineration for disposal, whereas polystyrene films have a serious problem on the difficulty of printing. Further, in the collection and recycling of PET bottles, labels made of resins other than PET, such as polyvinyl chloride or polystyrene, should be separated from the bottles. Therefore, considerable attention has been drawn to heat-shrinkable polyester films having no such problems.
In recent years, since colored bottles are not suitable for regeneration in regard to the recycling of PET bottles, alternative plans have been studied. Among them is a method of employing colored bottles and allowing colored labels to shrink over these bottles.
However, when used for full labels on bottles, since these bottles have complicated shapes in great variety, the conventional heat-shrinkable films may cause a serious problem on the shrinkage finish. In particular, for full labels on narrow-mouthed bottles, such as beverage bottles, having a great difference in diameter between their barrels and mouths, the conventional heat-shrinkable films may cause shrinkage failure at the necks of the bottles. Therefore, heat-shrinkable films used for full labels on such bottles should have excellent heat-shrinkage characteristics including high shrinkability. Further, the conventional heat-shrinkable films may require a change in the conditions of shrinkage finish by a decrease in low temperature shrinkability during storage before shrinkage, or they may exhibit poor shrinkage in some cases.
As described above, the conventional heat-shrinkable polyester films have insufficient performance for full labels on bottles.
SUMMARY OF THE INVENTION
The present invention, which can solve the above problems, has been made to provide heat-shrinkable polyester films suitable for full labels on bottles, particularly full labels on PET bottles, which exhibit, when used for full labels on bottles, good shrinkage finish involving only rare occurrence of wrinkles, shrinkage spots, strains and shrinkage failure during heat shrinkage, and which exhibit a low decrease in low temperature heat shrinkability after a lapse of time.
Thus the present invention provides heat-shrinkable polyester films each having: a heat shrinkability of 30-60% after treatment in hot water at 70° C. for 5 seconds and of 65% or higher after treatment in hot water at 85° C. for 5 seconds, both in the main shrinkage direction, and of 10% or lower after treatment in hot water at 85° C. for 5 seconds in a direction perpendicular to the main shrinkage direction; a heat shrinkability after storage at 25° C. for one month of 25% or higher after treatment in hot water at 70° C. for 5 seconds in the main shrinkage direction; and a thickness distribution of 6% or lower, thereby solving the above problems.
DETAILED DESCRIPTION OF THE INVENTION
The heat-shrinkable polyester films of the present invention are preferably produced from polyester compositions containing polyesters and polyester elastomers, which polyesters are composed of dicarboxylic acid components and diol components as constituent components. The polyester compositions preferably contain polyesters at 50-95 wt % and polyester elastomers at 5-50 wt %, more preferably at 5-20 wt %, and most preferably at 5-10 wt %. The reasons for this are that: when the amounts of polyester elastomers are higher than 50 wt %, there is a tendency for heat-shrinkable films to hardly have shrinkability required for close adhesion to vessels, which is not preferred; and when the amounts of polyester elastomers are lower than 5 wt %, heat-shrinkable films can hardly attain low temperature shrinkability and can easily cause shrinkage at a higher speed, so that there is a tendency for heat-shrinkable films to have deteriorated shrinkage finish involving the occurrence of wrinkles and strains during shrinkage, which is also not preferred.
The dicarboxylic acid components constituting the polyesters used in the present invention may include aromatic dicarboxylic acids terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and ortho-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 in the polyesters, their amounts may preferably be lower than 3 mol %. For heat-shrinkable polyester films obtained from the polyesters containing these aliphatic dicarboxylic acids at 3 mol % or higher, their film stiffness in the high-speed fitting is insufficient.
Further, the polyesters preferably contain no three or more functional polycarboxylic acids (e.g., trimellitic acid, pyromellitic acid, their anhydrides). For heat-shrinkable polyester films obtained from the polyesters containing these polycarboxylic acids, their high shrinkability required 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 preferably have glass transition temperatures (Tg) adjusted to 60-75° C. by incorporation of at least one selected from diols containing 3-6 carbon atoms (e.g., propanediol, butanediol, neopentyl glycol, hexanediol).
For heat-shrinkable polyester films exhibiting particularly excellent shrinkage finish, the use of neopentyl glycol as one of the diol components is preferred.
The polyesters preferably contain neither diols containing 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 from the polymers containing these diols or polyhydric alcohols, their high shrinkability required can hardly be attained.
The polyesters 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. The polyesters used in the present invention preferably contain diethylene glycol in amounts of smaller than 4 mol %.
When two or more polyesters are used in admixture, the amounts of acid components and the amounts of diol components are relative to the total amount of all acid components and the total amount of all diol components, respectively, both of which are contained in these polyesters, independently of whether or not transesterification has been carried out after the mixing.
To the heat-shrinkable polyester films of the present invention, there may preferably be added, for the purpose of improving their self-lubricating properties, inorganic lubricants such as titanium dioxide, fumed silica, kaolin and calcium carbonate; or organic lubricants such as long-chain fatty acid esters, and there may further be added, if necessary, additives such as stabilizers, colorants, antioxidants, defoamers, antistatic agents and ultraviolet light absorbers.
All the above polyesters can be prepared by polymerization according
Ito Hideki
Nagano Hiroshi
Tabota Norimi
Chen Vivian
Kenyon & Kenyon
Toyo Boseki Kabushiki Kaisha
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