Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
2001-04-10
2002-05-07
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S333000, C428S338000, C428S339000, C428S346000, C428S347000, C428S480000
Reexamination Certificate
active
06383627
ABSTRACT:
FILED OF INVENTION
The present invention relates to, heat-shrinkable polyester films and more particularly to heat-shrinkable polyester films which have frosted glass like appearances without being printed or processed and to heat-shrinkable polyester films which can prevent the contents of a vessel fitted therewith from being deteriorated by ultraviolet light and have good shrinkage finish and particularly cause only rare occurrence of wrinkles, shrinkage spots, or other defects. These films are suitable for labels, particularly for labels of great product value.
BACKGROUND OF THE INVENTION
Frosted glass bottles have been mainly used as sake bottles for gifts, but their use has been unavoidably reduced in the recent movement toward the recycling of bottles. Frosted glass bottles have been therefore replaced by transparent glass bottles fitted with labels made of heat-shrinkable films. For these labels, heat-shrinkable films made of thermoplastic resins such as polyvinyl chloride and polystyrene have been mainly used; 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. Therefore, heat-shrinkable polyester films have attracted considerable attention. The conventional heat-shrinkable polyester films have been finished to have frosted glass like appearances by printing or processing, which are, however, unfavorable to industrial use because of their high cost and long delivery time.
For heat-shrinkable films used as labels, particularly on the barrel of bottles, those films made of thermoplastic resins such as polyvinyl chloride and polystyrene have been mainly used; however, as described above, 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 thermoplastic resins other than PET should be separated from the PET bottles. Therefore, heat-shrinkable polyester films have also attracted considerable attention as those which can solve such problem.
In recent years, the case has been increasing where heat-shrinkable labels are used for the purpose of protecting the content of a vessel fitted therewith from being deteriorated by ultraviolet light. The ultraviolet light cut type heat-shrinkable films made of polyvinyl chloride have been used so far; however, for the above reason, there has been a great demand for ultra-violet light cut type heat-shrinkable films made of other materials. The specific cut properties may vary depending upon the contents of a vessel fitted with these films. In the case of food or beverage, cut properties in the long wavelength region, particularly at 380 nm and at 400 nm, are important because the contents will cause a change in quality or will become colored by ultraviolet light in the long wavelength region, i.e., at wavelengths of 360 to 400 nm.
The conventional heat-shrinkable polyester films, however, have no ultraviolet light cut properties in the above long wavelength region.
SUMMARY OF THE INVENTION
Under these circumstances, the present inventors have intensively studied to solve the above-described problems in the prior art and to develop heat-shrinkable polyester films having frosted glass like appearances and heat-shrinkable polyester films having ultraviolet light cut properties in the long wavelength region. As a result, they have found that this purpose can be attained by the control of total light transmittance, haze and 45-degrees specular gloss, and by the control of light transmittance at specific wave-lengths and haze, respectively, thereby completing the present invention.
Thus the present invention provides a heat-shrinkable polyester film, which exhibits a total light transmittance of 80% to 90% and a haze of 15% to 60%, both in a thickness of 50 &mgr;m, and further exhibits a 45-degrees specular gloss of 70% or lower (also referred to hereinafter as the first heat-shrinkable polyester film(s) of the present invention).
The present invention further provides a heat-shrinkable polyester film, which exhibits a light transmittance of 0% to 20% at a wavelength of 380 nm and of 0% to 60% at a wavelength of 400 nm, and further exhibits a haze of 15% or lower (also referred to hereinafter as the second heat-shrinkable polyester film(s) of the present invention).
DETAILED DESCRIPTION OF THE INVENTION
The following will describe the first heat-shrinkable polyester films of the present invention, which have frosted glass like appearances without being printed or processed.
The first heat-shrinkable polyester films of the present invention may preferably be prepared from polyester compositions containing polyesters, which are composed of dicarboxylic acid components and diol components, and polyester elastomers.
For the dicarboxylic acid components in the polyesters, conventional dicarboxylic acids can be used alone or in combination, including aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphtha-lenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, sebacic acid and decanedicarboxylic acid; and alicyclic dicarboxylic acids. For the diol components in the polyesters, conventional diols can be used alone or in combination, including ethylene glycol, propylene glycol, triethylene glycol, butylene glycol, diethylene glycol, neopentyl glycol, 1,4-cylcohexanedimethanol, and ethylene oxide adducts of tetramethylene glycol.
The polyester elastomers used in the present invention refer to polyester block copolymers composed of high melting point crystalline polyester segments (hard segments) and low melting point soft polymer segments (soft segments) having molecular weights of 400 or higher. Polyester elastomers containing polylactones (e.g., poly-&egr;-caprolactone) as the soft segments are particularly preferred.
The polyester compositions as the base material may further contain, if necessary, additives such as stabilizers, colorants, antioxidants and anti-static agents.
The present inventors have found that frosted glass like appearances can be rendered to films by the formation of undulation or large projections on their surface. More particularly, the gloss of films can be removed by the formation of projections on their surface, which are in size equal to or larger than a certain constant value depending upon the kind of lubricating fine particles. For example, the gloss of films can be controlled by adjusting the size of projections on their surface with lubricating fine particles made of an inorganic or organic compound, having an average particle diameter of 2 to 15 &mgr;m, in an amount of 0.1 to 10 wt %, preferably 0.5 to 5 wt %.
The present inventors have also found that the transparency of films can be obtained by optimizing the size and shape of lubricating fine particles. More particularly, lubricating fine particles larger in average particle diameter have a tendency to make a further improvement in the transparency of films containing the same amount of lubricating fine particles, although the reason for such tendency is not clear.
The lubricating fine particles used for rendering frosted glass like appearances may include conventional inert foreign particles such as those made of kaolin, clay, calcium carbonate, silicon dioxide, calcium terephthalate, aluminum oxide, titanium oxide, calcium phosphate or carbon black; and internal particles made of high melting point organic compounds insoluble in the film formation from molten polyester resins, or cross-linked polymers, or formed in the polyesters by metal compound catalysts used in the polyester polymerization. In particular, spherical particles of cross-linked polymers may preferably be used because the gloss and transparency of films can be obtained at the same time.
The present inventors have employed the total light transmittance, haze, and 45-degrees specular gloss of
Anami Tetsuya
Hashimoto Masatoshi
Nagano Hiroshi
Tabota Norimi
Acquah Samuel A.
Morrison & Foerster / LLP
Toyo Boseki Kabushiki Kaisha
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