Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-04-17
2003-04-15
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S601000, C524S604000, C524S605000, C528S272000
Reexamination Certificate
active
06548595
ABSTRACT:
FILED OF INVENTION
The present invention relates to heat-shrinkable thermoplastic resin films, particularly, to heat-shrinkable thermoplastic resin films suitable for use as indicator labels on the beverage bottles. More particularly, it relates to heat-shrinkable thermoplastic resin films for use as full labels to be fitted over the wide area on the barrels of bottles, particularly PET bottles, which cause only rare occurrence of wrinkles, shrinkage spots, and strains during heat shrinkage.
BACKGROUND OF THE INVENTION
For heat-shrinkable films, particularly heat-shrinkable films for use as labels to be fitted on the barrels of bottles, there have been mainly used films made of thermoplastic resins such as polyvinyl chloride, polystyrene or polyester.
In the case of PET bottles, colored bottles may sometimes be used for the protection of contents. However, alternative plans have been studied because colored bottles are not suitable for recycling. One of them involves using uncolored bottles and fitting colored labels over the whole surface of these bottles.
In general, bottles have complicated shapes and the variety of shapes. This may cause a problem of shrinkage finish when the conventional heat-shrinkable films are used as full labels. Particularly, in the case of narrow-mouthed bottles with a great difference in diameter between their barrels and mouths, such as beverage bottles, there is a problem that the conventional heat-shrinkable films may exhibit insufficient shrinkage at the necks of these bottles. Therefore, heat-shrinkable films for use as full labels on such bottles are required to have excellent heat-shrinkage characteristics such as high shrinkability.
As described above, the conventional heat-shrinkable thermoplastic resin films have not had satisfactory performance for use as full labels on the bottles.
SUMMARY OF THE INVENTION
Under these circumstances, the present inventors have extensively studied to provide heat-shrinkable thermoplastic resin films suitable for use as full labels on the bottles, particularly PET bottles, which have excellent heat-shrinkage characteristics and therefore cause only rare occurrence of wrinkles, shrinkage spots, and strains during heat shrinkage. As a result, they have found that such heat-shrinkable thermoplastic resin films can be obtained by the control of heat shrinkability after treatment in hot water.
Thus the present invention provides heat-shrinkable thermoplastic resin films wherein the heat shrinkability in the main shrinkage direction of the film is 5% to 60% after treatment in hot water at 70° C. for 5 seconds and 67% or higher after treatment in hot water at 85° C. for 5 seconds and the heat shrinkability in a direction perpendicular to the main shrinkage direction of the film is 10% or lower after treatment in hot water at 85° C. for 5 seconds, thereby completing the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides heat-shrinkable thermoplastic resin films which are suitably used as full labels, particularly on the PET bottles.
The thermoplastic resin may include, but are not particularly limited to, polyvinyl chloride, polystyrene, acrylic, and polyester resins.
In recent years, however, serious problems have been indicated that, for example, chlorine-containing gases will be evolved in the incineration of polyvinyl chloride for disposal and printing is difficult on polystyrene. Further, in the recycling of PET bottles, labels made of resins other than PET, such as polyvinyl chloride or polystyrene, should be separated from the PET bottles. For this reason, heat-shrinkable polyester films requiring no separation in the recycling are preferred.
The following will describe heat-shrinkable polyester films, in particular.
The dicarboxylic acid components, which are contained in the polyesters used in the present invention, may include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and orthophthalic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid; and alicyclic dicarboxylic acids.
The polyesters may preferably contain aliphatic dicarboxylic acids (e.g., adipic acid, sebacic acid, decanedicarboxylic acid) in amounts of smaller than 3 mol %. For heat-shrinkable polyester films obtained by the use of polyesters containing these aliphatic carboxylic acids in amounts of 3 mol % or greater, 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, the desired high shrinkability can hardly be attained.
The diol components, which are contained in the polyesters used in the present invention, may include aliphatic diols such as ethylene glycol, propane diol, 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 which have glass transition temperatures (Tg) adjusted to 60° C. to 75° C. by the incorporation of at least one diol of 3 to 6 carbon atoms (e.g., propanediol, butanediol, neopentyl glycol, hexanediol).
For the purpose of obtaining heat-shrinkable polyester films having particularly excellent shrinkage finish, neopentyl glycol may preferably be used as one of the diol components, more preferably in an amount of 16 wt % or greater. More preferably, butanediol is used in combination with the other diol components. This is because the use of low Tg components makes excellent shrinkability at low temperatures.
For the purpose of obtaining heat-shrinkable polyester films having high shrinkability, amorphous components may preferably be added in controlled amounts; for example, amorphous polymers such as neopentyl glycol copolymerized polyesters are added in greater amounts.
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 polymers containing these diols or polycarboxylic acids, the 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. The polyesters used in the present invention may 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, both of which are contained in these polyesters, independently of whether or not transesterification has been carried out after the mixing.
To improve the self-lubricating properties of the 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, when so required, additives such as stabilizers, colorants, antioxidants, defoamers, antistatic agents and ultraviolet light absorbers.
The above polyesters can be prepared by polymerization according to the conventional methods, for example, direct esterification method in which dicarboxylic acids are directly reacted with diols, or transesterification in which dimethyl dicarboxylates are reacted with diols. The polymerization may be carried out in batch or continuous manner.
For the heat-shrinkable thermoplastic resin films of the present invention,
Ito Hideki
Nagano Hiroshi
Tabota Norimi
Morrison & Foerster / LLP
Niland Patrick D.
Toyo Boseki Kabushiki Kaisha
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