JP2002326324A - Ultraviolet absorbing polystyrenic resin heat-shrinkable film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultraviolet absorbing polystyrenic resin heat-shrinkable film sufficiently having ultraviolet absorbability, reducing the surface staining of a casting drum and good in the adhesion with printing ink. SOLUTION: The ultraviolet absorbing polystyrenic resin heat-shrinkable film is obtained by at least unidirectionally stretching a film raw material having a three-layered structure characterized in that both outer layers comprise a polystyrenic resin compounded with 0.05-0.50 wt.% of an ultraviolet absorber and 0.003-0.05 wt.% of an unsaturated fatty acid amide type lubricant and an intermediate layer comprising a polystyrenic resin compounded with 0.40-5.0 wt.% of the ultraviolet absorber and the compounding amount of the ultraviolet absorber of the intermediate layer is made larger than that of both outer layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable polystyrene resin film used for heat-shrinkable labels attached to various containers and the like, and more particularly to protection of contents of containers and the like and weather resistance of the film itself. The present invention relates to a heat-shrinkable ultraviolet-absorbing polystyrene resin film containing an ultraviolet absorbent (hereinafter, referred to as a UV agent) in order to increase the heat resistance.

[0002]

2. Description of the Related Art Conventionally, as a heat-shrinkable film of an ultraviolet ray absorbing type, there is a single-layer film in which a UV agent is blended. At the same time, the surface of the casting drum is stained, and a film having good transparency cannot be formed. Therefore, it is necessary to frequently clean the casting drum, and there is a problem that productivity is lowered. There is also a problem that the adhesion of the printing ink is reduced due to the blowing of the UV agent onto the film surface.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultraviolet absorbing agent, to suppress sublimation and volatilization of a UV agent, to reduce contamination on the surface of a casting drum, and to improve transparency and productivity. An object of the present invention is to provide an excellent ultraviolet ray absorbing polystyrene resin heat shrinkable film.

[0004]

SUMMARY OF THE INVENTION The present inventors have developed an intermediate layer containing a large amount of an ultraviolet absorber in a polystyrene resin and a specific amount of an ultraviolet absorber and a specific amount of an unsaturated fatty acid amide-based lubricant in the polystyrene resin. It has been found that the above-mentioned object can be achieved by forming a three-layer structure of both surface layers in which is blended, thereby completing the present invention.

[0005] That is, the present invention provides two types of three-layer structure.
Layer or a three-layer and three-layer polystyrene resin heat-shrinkable film, 0.05 to 0.50% by weight of an ultraviolet absorber and 0.5% of an unsaturated fatty acid amide were added to both outer layers of the polystyrene resin.
It is compounded in the range of 0.3 to 0.15% by weight, and is mixed with the polystyrene resin of the intermediate layer in the range of 0.40 to 5.0% by weight of the ultraviolet absorber. Provided is a heat-shrinkable UV-absorbing polystyrene resin film obtained by stretching a raw film of a co-extruded film in at least one direction so as to have a three-layer structure in which an intermediate layer is increased.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The polystyrene resin used for the heat-shrinkable UV-absorbing polystyrene resin film of the present invention includes a styrene-butadiene-styrene type block copolymer, a styrene-butyl (meth) acrylate copolymer, a transparent
High impact polystyrene, GP polystyrene, styrene
One or a mixture of two or more butadiene-based thermoplastic elastomers can be used, and those having a styrene-butadiene-styrene block copolymer as a main component can be preferably used.

The ultraviolet absorber (UV) used in the present invention
Agent) is, for example, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5
Benzotriazoles such as -chlorobenzotriazole, 2-hydroxybenzophenone, 2,4-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4- Conventional UV absorbers such as benzophenones such as methoxybenzophenone and salicylates such as pt-butyl-phenyl salicylate can be used. It is also possible to use a hindered amine light stabilizer in combination.

[0008] The unsaturated fatty acid amide-based lubricant used in both surface layers is a reaction of an unsaturated monofatty acid and an amine, and typical examples thereof include erucamide and oleic amide. In addition to the above unsaturated fatty acid amide lubricants, saturated fatty acid amide lubricants such as stearamide, behenic amide and bisamide lubricants such as ethylene bis stearamide, ethylene bis erucamide, ethylene bis oleic acid amide Can be used in combination with a smaller amount than the unsaturated fatty acid amide-based lubricant as long as the printability is not impaired. Further, the above lubricant can be contained to such an extent that the printability of both surface layers is not impaired.

The amount of the UV agent blended in the intermediate layer of the heat-shrinkable polystyrene resin film of the present invention is 0.4 to 5% by weight, preferably 0.5 to 3% by weight.
More preferably, it is in the range of 0.7 to 2.5% by weight.
If the content of the UV agent is too small, the effect of protecting the contents of the container is small, and if it is too large, the film is colored and the transparency is reduced.

The amount of the UV agent blended in both surface layers of the heat-shrinkable UV-absorbing polystyrene resin film of the present invention is 0.05 to 0.50% by weight, preferably 0.07 to 0.5% by weight.
0.45% by weight, more preferably 0.10 to 0.40%
% By weight. The compounding amount of the unsaturated fatty acid amide-based lubricant used in combination with the above UV agent is in the range of 0.03 to 0.15% by weight, preferably 0.04 to 0.12% by weight. When used together within the range of the compounding amount, a film with less stain on the casting drum, excellent transparency, and good adhesion of the printing ink can be obtained. If the content of the above-mentioned UV agent or unsaturated fatty acid amide-based lubricant is small, the surface layer may be deteriorated by ultraviolet rays, the impact resistance or the slipperiness may be reduced, and the film may be broken. Sublimation of unsaturated fatty acid amide-based lubricants,
The volatilization increases and the productivity decreases and the adhesion of the printing ink also deteriorates.

The total thickness of the heat-shrinkable UV-absorbing polystyrene resin film of the present invention is, for example, 20 to 100 μm.
m, preferably in the range of 25 to 80 μm. Further, the ratio of the thickness of the intermediate layer, which is responsible for the main ultraviolet absorbing ability, is preferably in the range of 50 to 90% of the total thickness.

The raw film of the heat-shrinkable UV-absorbing polystyrene resin film of the present invention can be produced by, for example, a coextrusion method. Specifically, a polystyrene resin composition forming the intermediate layer and a polystyrene resin composition forming both surface layers are melt-extruded using a plurality of extruders equipped with T-die to form a three-layer structure. And cooled by a casting drum. The heat-shrinkable UV-absorbing polystyrene-based resin film of the present invention can be obtained by stretching this raw film. This stretching treatment is preferably performed by a tenter method. If necessary, the film is stretched in the longitudinal direction (extrusion direction), for example, about 1.0 to 1.5 times, and then 3 to 6 times, preferably in the transverse direction (width direction). It is stretched 4.0 to 5.6 times.

[0013]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Evaluation Method) 1. Stain on Casting Drum Stain on the drum after continuous casting for 8 hours on a mirror-finished casting drum was evaluated according to the following criteria. ：: Mirror surface with almost no stain due to UV agent. Δ: The mirror surface of the drum is slightly cloudy, but has little effect on the transparency of the film. X: The UV agent adhered white on the drum, and the transparency of the film was poor.

2. Ultraviolet Transmittance The heat-shrinkable film having a thickness of 40 μm produced was measured with an ultraviolet-visible spectrophotometer (V-570, manufactured by JASCO Corporation), and the transmission at a wavelength of 380 nm serving as a measure for cutting off ultraviolet rays was performed. The percent was measured and this was taken as the UV transmittance. 10 for normal use
% Or less, there is an ultraviolet cut effect.

3. Adhesiveness of printing ink One side of the heat-shrinkable film having a thickness of 40 μm,
A white ink for polystyrene (manufactured by Sakata Inx) was mixed with a mixed solvent of isopropyl alcohol and ethyl acetate (3:
The film was diluted in 1), printed on a film with a metering bar by a conventional method, and dried to obtain a printed layer. After sticking a cellophane tape having a width of 18 mm to the print layer by finger pressure, the print layer was rapidly peeled off, and the peeling state of the print layer was evaluated according to the following criteria. A: There is no peeling of the printed layer at all. ：: peeling of the printed layer is less than 10%. Δ: The peeling of the printed layer is 10% or more and less than 20%. X: The peeling of the printing layer is 20% or more.

4. Weather Resistance The heat-shrinkable film having a thickness of 40 μm was subjected to sunshine weather o-meter (60 ° C., under humid conditions).
After irradiation for 00 hours, changes in the appearance of the film were evaluated according to the following criteria. ：: No change in appearance such as transparency and coloring. Δ: Transparency is slightly inferior. X: The film becomes whitish and the transparency is reduced.

Examples 1 to 3 and Comparative Examples 1 and 2 A styrene-butadiene-styrene type block copolymer (butadiene unit content: 17% by weight, glass transition temperature: 73 ° C.) was used for both surface layers and intermediate layers (each layer). Is used for the surface layer / intermediate layer / surface layer = 10/80/10), and the UV agent is a benzotriazole-based (manufactured by Kyodo Yakuhin,
Viosorb 550) and an unsaturated fatty acid amide-based lubricant using erucamide (manufactured by NOF CORPORATION). Both surface layers and an intermediate layer were supplied to each extruder according to the formulation shown in Table 1, and at 200 ° C. The sheet was melted, laminated into two types of three layers by coextrusion, and cooled with a casting drum having a surface temperature of 25 ° C. to obtain a sheet having a thickness of 200 μm. The sheet was continuously fed into a tenter and stretched 5 times in the transverse direction at 90 ° C. to a thickness of 40 μm (surface layer / intermediate layer / surface layer = 4 μm / 3
2 μm / 4 μm) was obtained.

[0019]

[Table 1]

In Examples 1 to 3 of the present invention, there was no stain on the casting drum, and the printing ink adhesion and the weather resistance were good. Further, the ultraviolet transmittance at a wavelength of 380 μm was remarkably low at 1 to 4%, showing good ultraviolet cutting performance. On the other hand, Comparative Example 1 in which a UV agent was added only to the intermediate layer
In the weather resistance test, the film surface layer deteriorated,
It became a whitish film. Further, in Comparative Example 2 having both surface layers to which a large amount of the UV agent was added, the casting drum was so dirty that continuous production was difficult, and the printing ink adhesion was weak and the film was easily peeled off.

Comparative Example 3 The procedure of Example 2 was repeated except that the unsaturated fatty acid amide lubricant used in both surface layers was replaced by a bisamide lubricant, ethylenebisstearamide (manufactured by Kao Corporation). A heat-shrinkable film having a thickness of 40 μm (surface layer / intermediate layer / surface layer = 4 μm / 32 μm / 4 μm) was obtained in the same manner as in Example 2. Table 2 shows the evaluation of this film.

Comparative Example 4 In Example 2, except that the unsaturated fatty acid amide lubricant used in both surface layers was replaced by a saturated fatty acid amide lubricant stearamide (manufactured by Nippon Kasei Co., Ltd.). A heat-shrinkable film having a thickness of 40 μm (surface layer / intermediate layer / surface layer = 4 μm / 32 μm / 4 μm) was obtained in the same manner as in Example 2. Table 2 shows the evaluation of this film.

[0023]

[Table 2]

Comparative Example 5 In the above Example 2, except that the amount of the unsaturated fatty acid amide-based lubricant erucamide (manufactured by NOF Corporation) used in both surface layers was 0.01% by weight. 40 μm thick (surface layer / intermediate layer / surface layer = 4) in the same manner as in Example 2.
(μm / 32 μm / 4 μm). However, the film was poor in slipperiness and wrinkled during winding, and could not be satisfactorily wound.

As shown in Table 2, in Comparative Examples 3 and 4, as compared with Example 2, dirt on the casting drum was observed, and the printing ink adhesion was weak, and the printing ink was easily peeled off.

[0026]

The heat-shrinkable UV-absorbing polystyrene resin film of the present invention comprises a polystyrene-based resin containing an intermediate layer containing a large amount of UV-absorbing agent and a polystyrene-based resin having a specific amount of an ultraviolet-absorbing agent and a specific amount of unsaturated material. By having a three-layer structure of both surface layers containing a fatty acid amide-based lubricant,
A heat-shrinkable film can be obtained in which the ultraviolet rays can be prevented from penetrating into the contents of a container or the like mounted as a label, the surface of the casting drum is less contaminated, and the adhesion of the printing ink is good.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) B29K 25:00 B29K 25:00 F term (Reference) 3E086 AB01 AD16 BA04 BA15 BA25 BA33 BB23 BB67 CA40 4F100 AK12A AK12B AK12C AK73A AK73B AK73C AL02A BA16 BA27 CA07A CA07C CA19A CA19C DA01 EH20 EJ37 GB16 JA03 JD09 JL06 JL09 4F210 AA13 AB06 AB07 AE01 AG01 QC01 QC05 QG01 QG18

Claims (2)

[Claims] In a heat-shrinkable polystyrene resin film of two or three layers having a three-layer structure, an ultraviolet absorbent is added to both outer layers of the polystyrene resin in an amount of 0.05 to 0.5.
50% by weight and unsaturated fatty acid amide lubricant 0.03 to
0.15% by weight, the UV absorber is mixed with the polystyrene resin of the intermediate layer in the range of 0.40 to 5.0% by weight, and the compounding amount of the UV absorber is from the outer layer to the outer layer. A heat-shrinkable ultraviolet-absorbing polystyrene resin film, characterized in that a raw film of a co-extruded film is subjected to stretching treatment in at least one direction so as to form a three-layer structure having more layers. 2. The heat-shrinkable UV-absorbing polystyrene resin film according to claim 1, wherein the ratio of the thickness of the intermediate layer is in the range of 50 to 90% of the total thickness.