Heat-shrinkable polyester film and packaging

Abstract

The invention provides a heat-shrinkable polyester film of which the longitudinal direction is the main shrinkage direction, which has a high shrinkage ratio in the main shrinkage direction, which isinsusceptible to wrinkles, etc., when used as a label because the difference between the shrinkage ratios at high temperatures and at low temperatures is small, and which undergoes few reductions in shrinkage ratio at low temperatures over time. As a solution, a heat-shrinkable polyester film is characterized by satisfying requirements (1)-(4) below: (1) the hot water shrinkage ratio is 40% or higher in the film main shrinkage direction when the film is immersed in 98 DEG C water for 10 seconds; (2) the difference between the hot water shrinkage ratio in the main shrinkage direction when the film is immersed in 70 DEG C water for 10 seconds and the aforementioned hot water shrinkage ratio in the main shrinkage direction at 98 DEG C is 0-20%; (3) ethylene terephthalate is the main constituent component, and the amount of diethylene glycol (DEG) components is 10-25 mol% out of 100 mol% of polyhydric alcohol components in the entire polyester resin that constitutes the film; (4) the difference between the hot water shrinkage ratio in the main shrinkage direction when the film is immersed in 70 DEG C water for 10 seconds after the film is aged for 28 days at a temperature of 40 DEG C and relative humidity of 85% and the hot water shrinkage ratio under similar conditions before the film is aged is 0-5%.

Description

technical field [0001] The present invention relates to a heat-shrinkable polyester film and a package. Specifically, it is suitable for use as a label for beverage bottles, has a high shrinkage rate in the longitudinal direction, and has a small difference between high temperature and low temperature shrinkage rates. A heat-shrinkable polyester film that is less likely to wrinkle when the label is used, and whose shrinkage rate at low temperatures is small over time, and a package using the label. Background technique [0002] In recent years, in applications such as label packaging, cap seals, integrated packaging, etc., which take into account the protection of glass bottles, PET bottles, etc. and the display of products, they are made of polyvinyl chloride resin, polystyrene resin, polyester resin, etc. High-quality stretched films (so-called heat-shrinkable films) have been widely used. Among such heat-shrinkable films, polyvinyl chloride-based films have problems such...

AI Technical Summary

Problems solved by technology

Among such heat-shrinkable films, polyvinyl chloride-based films have problems such as low heat resistance, generation of hydrogen chloride gas during incineration, or the cause of dioxins, etc.

In addition, polystyrene-based films have the following problems: poor solvent resistance, ink with a special composition must be used for printing, and they must be incinerated at high temperatures, and a large amount of black smoke is produced with a foul smell during incineration

However, it can be seen that when the above-mentioned monomers are used, the decrease in the low-temperature shrinkage rate due to time is remarkable

When the film is stored for a long time after film production, it loses low-temperature shrinkability, so it is believed that wrinkles are likely to occur when the shrinkage is completed

In order to suppress the decrease of low-temperature shrinkage rate due to time, storage at low temperature is required, and the cost increases

[0006] In addition, in Patent Document 2, by using 1,4-butanediol as a polyol component, the glass transition temperature of the film is lowered and the low-temperature shrinkage property is improved, but it is known that the use of 1,4-butanediol reduces the high-temperature shrinkage. From the viewpoint of shrinkage completion, it is considered that the shrinkage will become insufficient, which is not preferable.

In addition, it can be seen that when 1,4-butanediol is used, the decrease in low-temperature shrinkage rate due to time is also large, which is not preferable.

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