JP2855734B2 - Heat shrinkable film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat-shrinkable film, specifically, a container,
Covering or bundling some or all of the caps, shoulders, body, etc. of the above containers for the purpose of protection, binding, labeling, etc. of bottles, cans, sticks, etc. (hereinafter simply referred to as containers). The present invention relates to a heat-shrinkable film used for a packaging material.

[Prior Art] Heat shrink wrapping is a method in which, for example, a product is relatively roughly cylindered with a tubular or bag-shaped heat-shrinkable film, and then the film is heated and shrunk to bring the film into close contact with the outer peripheral surface of the product. In addition, since a beautiful package appearance can be obtained relatively easily even in the case of packaging containers having irregular shapes, the demand for the heat-shrinkable film is expected to further increase in the future as a material suitable for automation.

However, in the case where the heat-shrinkable film is printed to form a tubular body and is attached as an annular label to a shoulder portion of, for example, a plastic bottle, the following problems occur.
In the labeling of a plastic bottle or the like, first, intermittent label printing is performed on one side of a sheet-like heat-shrinkable film at regular intervals, and then the sheet-like heat-shrinkable film is printed on a transparent portion where no printing is applied. Then, each unit label is cut off individually, and both sides of the label are attached to form a tube [so that a non-printed portion (transparent portion) is left circumferentially at both ends of the tube]. It is performed by covering the plastic bottle at a predetermined position and thermally shrinking it. However, at present, as shown in FIG. 3, the transparent portions remaining at the upper and lower ends of the label are curled inward and bent to deteriorate the appearance. .

[Problems to be Solved by the Invention] The present invention has been made in view of such circumstances, and is made of a heat-shrinkable film as a material, and is formed by printing with a transparent portion left at an end. Another object of the present invention is to provide a heat-shrinkable film in which a transparent portion at an end of the heat-shrinkable label does not bend in a bag-shaped heat-shrinkable label.

[Means for Solving the Problems] The present invention solves the above-mentioned problems. A tubular or bag-shaped heat-shrinkable film having a non-printed portion left at the open end thereof is printed. In the heat-shrinkable film, at least one of and / or both surfaces of the non-printed portion is subjected to non-orientation or orientation relaxation treatment with an organic solvent.

[Effects] The inventors of the present invention have made intensive studies and have found that curl generated during heat shrinkage is caused by a difference in heat shrinkage speed between a non-printed portion and a printed portion. It was decided to do. Therefore, a description will be given below with reference to FIGS. 4 and 5.

When printing is performed on the heat-shrinkable film, the printing portion where the printing ink is laminated receives the reinforcing effect of the printing ink, and the printing ink itself does not show heat shrinkage. Causes a difference in thermal behavior. That is, a portion having a high shrinking speed [hereinafter referred to as a transparent portion (4)] and a portion having a low shrinking speed [hereinafter referred to as a printed portion (5)] are formed on the same label formed from the heat-shrinkable film. Becomes Therefore, in FIG. 4, the state of the label after the elapse of the heat contraction time sec is that the transparent portion (4) has contracted earlier as shown in FIG. A serious bend will occur.

Therefore, the present inventors have proposed a transparent part (4) and a printed part (5).
As a result of repeated studies in a direction to minimize the difference in the shrinkage speed of the transparent portion (4), if at least a part of the transparent portion (4) is subjected to a non-orientation or orientation relaxation treatment using an organic solvent, the shrinkage speed of the transparent portion (4) is reduced. It has been found that it is possible to suppress the breakage after heat shrinkage. This reduces the degree of orientation of the polymer chains by partially dissolving or swelling the surface of the film that has been oriented by the stretching process with an organic solvent, thereby suppressing the shrinkage rate of the transparent portion (4). It is considered possible. In the present invention, since it is sufficient that the shrinking speed of the transparent portion (4) can be suppressed by the end of the heat shrinkage, the transparent portion (4) is earlier than the printed portion (3) during the heat shrinkage by treating with a non-volatile organic solvent. May be signaled to ease the orientation.

The type of the heat-shrinkable film in the present invention is not limited, and may be any organic solvent-soluble or swellable film. For example, a polyamide film,
A heat-shrinkable film such as a polyethylene film, a polypropylene film, a polystyrene film, a polyvinyl chloride film, a polyvinyl chloride film, a polyester film and a rubber hydrochloride film is applicable.

The organic solvent applicable to the present invention is not particularly limited as long as it can dissolve or swell the heat-shrinkable film, and examples thereof include methyl ethyl ketone, cyclohexanone, and the like.
Examples include benzyl alcohol, methyl acetate, ethyl acetate, amyl acetate, dioxane, tetrahydrofuran, benzene, toluene, xylene, cresol, and halogenated hydrocarbons such as carbon tetrachloride and ethane tetrachloride.
These organic solvents can be used alone or as a mixed solvent.

As shown in the embodiment in FIG. 2, the application position of the organic solvent may be such that the orientation of the heat-shrinkable film can be reduced by applying the organic solvent to at least a part of the transparent portion. May be applied.

[Example] Printing was performed on one side of a heat-shrinkable polyester film having a heat-shrinkage ratio of 50%, and a label having 1.5 mm transparent portions at both upper and lower ends was prepared, thereby obtaining a cylindrical comparative test piece.

Next, on the printing surface side of the label, about 2 mm from the upper and lower ends (1.5 mm for the transparent part and 0.5 mm for the upper end of the printed part), a mixed solvent of ethyl acetate and methyl ethyl ketone (mixing ratio 70/3)
(0 volume ratio) was applied at 8 g / m ² and dried to obtain a cylindrical test piece of the present invention.

The test piece was placed on a glass bottle, heated at 155 ° C. for 4 seconds, and thermally shrunk. Then, the curl of the transparent portion was checked. The curl of the transparent portion was evaluated by visual inspection, and if any bend was observed at one end in the circumferential direction, it was determined that the curl occurred. The results are shown in Table 1.

On the other hand, before forming into a cylindrical shape, the above label is heated at 140 ° C., and the heat shrinkage ratio of the transparent portion and the printed portion after 1 second, 2 seconds, and 4 seconds after the start of heat shrinkage is calculated. The measurement was carried out by the following method, and the difference between the two thermal shrinkage rates was determined. The results are shown in Table 2.

[Thermal shrinkage] When the label is formed in a cylindrical shape, the length in the circumferential direction is measured, and when the length before heating is l ₁ and the length after heat shrinking is l ₂ , Was defined as the heat shrinkage (%).

In the embodiment, since the heat shrinkage speeds of the printed portion and the transparent portion are substantially equal, the difference in the heat shrinkage between 1 second and 2 seconds after the start of the heat shrinkage is small, and no curl is observed at the upper and lower ends of the label. On the other hand, in the comparative example, since the difference in the thermal shrinkage rate between 1 second and 2 seconds after the start of the thermal shrinkage is large, breakage occurs at several places along the circumferential direction.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to prevent the transparent portion, which has been generated when labeling a bottle, from being folded into the inside, thereby improving the aesthetic appearance of the product and increasing its commercial value. Could be raised.

[Brief description of the drawings]

FIG. 1 is a reference cross-sectional view of a heat-shrinkable film showing a main embodiment of the present invention, FIG. 2 is a reference cross-sectional view of a heat-shrinkable film showing an embodiment other than FIG. 1, and FIG. Reference external view showing the curl state when labeling a heat-shrinkable film, FIG. 4 is a graph showing the difference in heat shrinkage rate between a transparent part and a printed part, and FIG. FIG. DESCRIPTION OF SYMBOLS 1 ... Heat-shrinkable film, 2 ... Printing ink 3 ... Organic solvent application part 4, ... Transparent part 5 ... Printing part

Claims (1)

(57) [Claims] 1. A tubular or bag-shaped heat-shrinkable film having a non-printed portion left at an open end of the tubular or bag-shaped heat-shrinkable film, wherein at least one of the non-printed portions is provided. A heat-shrinkable film, wherein one side and / or both sides are subjected to non-orientation or orientation relaxation treatment with an organic solvent.