JP2022171128A - Heat-shrinkable multilayer film - Google Patents

Abstract

To provide a heat-shrinkable multilayer film having higher resistance to skin whitening while maintaining rigidity.SOLUTION: A heat-shrinkable multilayer film includes a base material, an intermediate layer and a surface layer. The base material has a first side and a second side, and contains a thermoplastic resin. The intermediate layer is laminated to at least one of the first side and the second side of the base material. The surface layer is laminated on the intermediate layer, and contains a thermoplastic resin. The intermediate layer contains 50 mass% or more and 90 mass% or less of a cyclic olefin resin, and 5 mass% or more and 35 mass% or less of a petroleum resin. A thickness of the surface layer is 10% or less of a thickness of the resin constituting the entire heat-shrinkable multilayer film.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to heat shrinkable multilayer films.

Patent Literature 1 discloses a heat-shrinkable multilayer film. The heat-shrinkable multilayer film disclosed in Patent Document 1 contains a resin (A) having an alicyclic structure in the molecule, an outermost layer having a thickness of 1 μm or less, and a thermoplastic resin other than (A) ( and an intermediate layer containing B). Examples of the thermoplastic resin (B) include petroleum resins. According to Patent Document 1, this provides a heat-shrinkable multilayer film having a large shrinkage rate when heated and excellent sebum-whitening properties.

JP 2004-276516 A

According to Patent Document 1, the layer made of the thermoplastic resin (B) preferably contains 70% by weight or more and 100% by weight or less of the thermoplastic resin (B) in the total resin components constituting the layer. However, if the petroleum resin is contained in the above range, the toughness and rigidity of the heat-shrinkable multilayer film may be lowered. Patent document 1 does not consider this point.

SUMMARY OF THE DISCLOSURE An object of the present disclosure is to provide a heat-shrinkable multilayer film that is more resistant to blanching while maintaining stiffness.

A heat-shrinkable multilayer film according to the first aspect comprises a substrate, an intermediate layer, and a surface layer. The substrate has a first side and a second side and contains a thermoplastic resin. The intermediate layer is laminated to at least one of the first side and the second side of the substrate. The surface layer is laminated on the intermediate layer and contains a thermoplastic resin. The intermediate layer contains 50% by mass or more and 90% by mass or less of a cyclic olefin resin and 5% by mass or more and 35% by mass or less of a petroleum resin. The thickness of the surface layer is 10% or less of the thickness of the resin constituting the entire heat-shrinkable multilayer film.

A heat-shrinkable multilayer film according to the second aspect is the heat-shrinkable multilayer film according to the first aspect, wherein the intermediate layer further contains 30% by mass or less of an ethylene-based resin.

A heat-shrinkable multilayer film according to the third aspect is the heat-shrinkable multilayer film according to the first aspect or the second aspect, wherein the surface layer contains a cyclic olefin resin.

A heat-shrinkable multilayer film according to a fourth aspect is a heat-shrinkable multilayer film according to any one of the first aspect to the third aspect, wherein the intermediate layer contains 10% by mass or more and 30% by mass or less of petroleum resin. contains.

A heat-shrinkable multilayer film according to a fifth aspect is the heat-shrinkable multilayer film according to any one of the first aspect to the fourth aspect, wherein an intermediate layer is laminated on each of the first surface and the second surface of the substrate. , a surface layer is laminated on each intermediate layer.

A heat-shrinkable label according to the sixth aspect includes the heat-shrinkable multilayer film according to any one of the first to fifth aspects.

From the above viewpoints, it is possible to provide a heat-shrinkable multilayer film that maintains rigidity and has a higher resistance to skin whitening.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows an example of the heat-shrinkable multilayer film which concerns on one Embodiment. BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows an example of the heat-shrinkable multilayer film which concerns on one Embodiment.

An embodiment of the heat-shrinkable multilayer film 100 according to the present disclosure will be described below. The heat-shrinkable multilayer film 100 comprises a sheet-like substrate 1 having a first surface and a second surface, an intermediate layer 2 laminated on at least one of the first surface and the second surface of the substrate 1, and a surface layer 3 laminated on the intermediate layer 2 . Therefore, as shown in FIG. 1, the heat-shrinkable multi-layer film 100 has an aspect in which the intermediate layers 2 are laminated on both sides of the base material 1, and the surface layer 3 is laminated on each intermediate layer 2, and as shown in FIG. Second, the intermediate layer 2 is laminated on one surface of the substrate 1, and the surface layer 3 is laminated on the intermediate layer 2. Each member will be described in detail below. In addition, what formed each material into a film may be called a film.

<1. Substrate>
The base material 1 contains a thermoplastic resin. The thermoplastic resin may contain, for example, a propylene-based resin and a petroleum resin. This will be explained below.

<1-1. Propylene resin>
As the propylene-based resin, a binary or ternary random copolymer containing propylene as a main component and an α-olefin as a copolymer component is preferable from the viewpoint of exhibiting heat shrinkability. Specifically, the α-olefin is preferably composed of ethylene, 1-butene, 1-hexene, 1-octene, etc., and may contain two or more kinds of α-olefins. The ratio of α-olefin as a copolymer component is preferably 1 to 10 mol %. Also, the propylene-based resin may be a mixture of different propylene-α-olefin random copolymers.

Examples of commercially available propylene-based resins as described above include Adsyl (manufactured by Basell), Novatec (manufactured by Japan Polypropylene Corporation), and the like.

The deflection temperature under load (0.45 MPa) of the propylene-based resin is preferably 110° C. or less, more preferably 90° C. or less. When the propylene-based resin is a mixed resin containing two or more propylene-based resins having different deflection temperatures under load, the deflection temperature under load of the propylene-based resin is determined by the deflection temperature under load and the blending ratio (weight ratio) means the apparent deflection temperature under load calculated by summing the products.

The substrate 1 preferably contains 65% by mass or more and 90% by mass or less, and preferably 70% by mass or more and 85% by mass or less, of the propylene-based resin based on 100% by mass of the resin component constituting the substrate 1. is more preferable.

<1-2. Petroleum Resin>
Petroleum resins are C5 fractions and C9 fractions produced by pyrolysis of naphtha, resins obtained by polymerizing mixtures thereof, and hydrogenated products thereof. Among these, from the viewpoint of suppressing softening of the film at 100 ° C. or less and ensuring transparency and rigidity, a hydrogenated alicyclic hydrocarbon resin having a partially or completely hydrogenated alicyclic structure is used. preferable. In addition, it is also possible to use a product obtained by purifying and polymerizing a single component or a plurality of components in the C5 fraction or C9 fraction.

Examples of commercially available petroleum resins as described above include Imarve (manufactured by Idemitsu Kosan), Alcon (manufactured by Arakawa Chemical Industries), and Regalite (manufactured by Eastman).

The softening point of the petroleum resin is preferably 100° C. or higher and 150° C. or lower, and more preferably 120° C. or higher and 130° C. or lower. When the softening point of the petroleum resin is within the above range, the heat shrinkability can be kept within a favorable range.

The base material 1 preferably contains 10% by mass or more and 35% by mass or less of the petroleum resin with respect to 100% by mass of the resin component constituting the base material 1, and contains 15% by mass or more and 30% by mass or less. is more preferred. When the content is within this range, high shrinkability and high rigidity can be imparted to the heat-shrinkable multilayer film. Moreover, when the content of the petroleum resin is equal to or less than the above upper limit, it is possible to suppress a decrease in elongation at low temperatures and separation between layers.

<1-3. Thickness>
The thickness of the substrate 1 is, for example, preferably 50% or more and 90% or less, and preferably 60% or more and 84% or less, with respect to the thickness of the resin constituting the entire heat-shrinkable multilayer film 100. More preferably, it is 70% or more and 80% or less.

<2. Intermediate layer>
The intermediate layer 2 mainly contains cyclic olefin resin and petroleum resin. Moreover, in addition to this, an ethylene-based resin can be further contained.

<2-1. Cyclic olefin resin>
Cyclic olefin-based resins can increase the heat shrinkage rate and the stretchability during production of the heat-shrinkable multilayer film 100 . A cyclic olefin copolymer (COC) is preferable as the cyclic olefin resin. A cyclic olefin copolymer is obtained, for example, by copolymerizing an α-olefin and a cyclic olefin.

Cyclic olefins are not particularly limited, and examples include norbornene, 6-methylnorbornene, 6-ethylnorbornene, 5-propylnorbornene, 6-n-butylnorbornene, 1-methylnorbornene, 7-methylnorbornene, 5,6-dimethyl Examples include norbornene and derivatives thereof, such as norbornene, 5-phenylnorbornene, 5-benzylnorbornene, and the like. Tetracyclododecene, 8-methyltetracyclo-3-dodecene, 8-ethyltetracyclo-3-dodecene, 5,10-dimethyltetracyclo-3-dodecene, etc., and tetracyclododecene and derivatives thereof may also be mentioned. .

Examples of commercially available cyclic olefin resins as described above include APEL (manufactured by Mitsui Chemicals, Inc.), TOPAS COC (manufactured by Polyplastics), and ZEONOR (manufactured by Nippon Zeon Co., Ltd.).

The number average molecular weight of the cyclic olefin resin measured by GPC (gel permeation chromatography) is preferably 1,000 or more, and preferably 1,000,000 or less. By setting the content within the above range, film formation becomes easier.

The glass transition temperature of the cyclic olefin resin is preferably 20°C or higher and 130°C or lower, more preferably 50°C or higher and 100°C or lower. When the glass transition temperature is 20° C. or higher, the heat resistance of the film surface is good, and the occurrence of blocking between containers on the mounting line can be suppressed, and the natural shrinkage rate is in a good range. be able to. When the glass transition temperature is 130° C. or lower, the lateral heat shrinkage rate can be sufficiently increased.

The density of the cyclic olefin resin is preferably 1000 kg/m ³ or more and 1050 kg/m ³ or less, more preferably 1010 kg/m ³ or more and 1040 kg/m ³ or less.

The intermediate layer 2 preferably contains 50% by mass or more and 90% by mass or less, and preferably 55% by mass or more and 85% by mass or less of the cyclic olefin resin based on 100% by mass of the resin component constituting the intermediate layer 2. more preferably 60% by mass or more and 80% by mass or less. When the content of the cyclic olefin resin is within the above range, the heat-shrinkable multilayer film 100 can have good rigidity, heat-shrinkability and transparency.

<2-2. Ethylene resin>
Examples of ethylene-based resins include branched low-density polyethylene resins, linear low-density polyethylene resins, ethylene-vinyl acetate copolymers, ionomer resins, and mixtures thereof. Also, copolymers of ethylene and α-olefins are mentioned. α-olefins include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. The above copolymer may be a random copolymer or a block copolymer. In particular, the intermediate layer 2 preferably contains linear low-density polyethylene resin.

Commercially available linear low-density polyethylene resins such as those described above include Evolue (manufactured by Prime Polymer Co., Ltd.), Yumerit (manufactured by Ube Maruzen Polyethylene Co., Ltd.), Novatec, and the like. Commercially available low-density polyethylene resins include Sumikasen (manufactured by Sumitomo Chemical Co., Ltd.) and Novatec (manufactured by Japan Polyethylene Co., Ltd.).

The intermediate layer 2 preferably contains 3% by mass or more and 30% by mass or less, and preferably 5% by mass or more and 25% by mass or less, of the ethylene resin based on 100% by mass of the resin component constituting the intermediate layer 2. It is more preferable to contain 8% by mass or more and 20% by mass or less. When the content of the ethylene-based resin is within the above range, it is possible to preferably suppress skin whitening of the cyclic olefin-based resin and improve the skin whitening resistance of the heat-shrinkable multilayer film 100 .

<2-3. Petroleum Resin>
As the petroleum resin, the petroleum resin already described in the description of the base material 1 can be used. The intermediate layer 2 may contain the same petroleum resin as the substrate 1, or may contain a different petroleum resin. The intermediate layer 2 preferably contains 5% by mass or more and 35% by mass or less, and preferably 10% by mass or more and 30% by mass or less, of the petroleum resin with respect to 100% by mass of the resin component constituting the intermediate layer 2. is more preferable, and it is even more preferable to contain 15% by mass or more and 25% by mass or less.

<2-4. Thickness>
The thickness of the intermediate layer 2 is, for example, preferably 5% or more and 25% or less, and preferably 8% or more and 20% or less, with respect to the thickness of the resin constituting the entire heat-shrinkable multilayer film 100. More preferably, it is 10% or more and 15% or less.

<3. Surface layer>
The surface layer 3 contains a thermoplastic resin. As the thermoplastic resin, for example, a styrene-based resin, a polyester-based resin, an ethylene-based resin, a cyclic olefin-based resin, or a mixture of at least one of these can be used. Moreover, the surface layer 3 may further contain fine particles. By including such fine particles, the surface layer 3 can be made uneven. Thereby, the fine particles function as an anti-blocking agent, and the blocking strength of the heat-shrinkable multilayer film 100 can be reduced. This will be explained below.

<3-1. Styrene-based resin>
As the styrene-based resin, for example, a styrene-butadiene copolymer and a hydrogenated styrene-based thermoplastic elastomer can be used. Examples of commercially available styrene-based resins include CLEAREN (manufactured by Denka Co., Ltd.).

<3-2. Polyester resin>
The polyester-based resin is not particularly limited, but glycol-modified polyethylene terephthalate is preferable.

<3-3. Ethylene resin>
Ethylene-based resins include linear low-density polyethylene resins, branched low-density polyethylene resins, ethylene-vinyl acetate copolymers, ionomer resins, or mixtures thereof. In addition, commercially available products include those already exemplified in the description of the intermediate layer.

<3-4. Cyclic olefin resin>
The details of the cyclic olefin resin are as described above. When a cyclic olefin resin is used for the surface layer 3, glossiness is increased and surface properties can be improved. Furthermore, in this embodiment, since the intermediate layer 2 also contains the cyclic olefin resin, the use of the cyclic olefin resin for the surface layer 3 improves the interlaminar adhesive strength with the intermediate layer 2 .

<3-5. fine particles>
The fine particles contained in the surface layer 3 can be either organic fine particles or inorganic fine particles. As the organic fine particles, organic fine particles such as acrylic resin fine particles, styrene resin fine particles, styrene-acrylic resin fine particles, urethane resin fine particles, and silicone resin fine particles can be used. These may or may not be crosslinked, but are preferably crosslinked in order to increase the heat resistance of the fine particles. Among them, from the viewpoint of compatibility with the cyclic olefin resin, acrylic resin fine particles are preferable, and polymethyl methacrylate crosslinked fine particles are more preferable. In addition, among the above organic fine particles, commercially available products include Techpolymer (manufactured by Sekisui Plastics Co., Ltd.), Fine Sphere (manufactured by Nippon Paint Co., Ltd.), Ganz Pearl (manufactured by Aika Kogyo Co., Ltd.), Art Pearl (Negami Kogyo company) and the like.

Examples of inorganic fine particles that can be used include silica, zeolite, and alumina.

The content of the fine particles is preferably 0.01 parts by weight or more and 0.10 parts by weight or less, more preferably 0.03 parts by weight or more and 0.03 parts by weight or more, with respect to 100 parts by weight of the resin component constituting the surface layer 3 . 08 parts by weight or less is more preferable.

<3-6. Thickness>
The thickness of the surface layer 3 is preferably 0.1% or more and 10% or less, and 0.3% or more and 8% or less, with respect to the thickness of the resin constituting the entire heat-shrinkable multilayer film 100. is more preferably 0.5% or more and 3% or less. By setting the thickness of the surface layer 3 within the above range, it is possible to improve the sebum whitening resistance of the heat-shrinkable multilayer film 100 .

<4. Thickness of heat-shrinkable multilayer film>
The thickness of the entire heat-shrinkable multilayer film of the present invention is preferably 15 μm or more and 50 μm or less, more preferably 20 μm or more and 45 μm or less, and even more preferably 25 μm or more and 40 μm or less.

<5. Other Ingredients>
The base material 1, the intermediate layer 2, and the surface layer 3 may optionally contain antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, and fluorescent brighteners. Additives such as agents and coloring agents may be contained.

<6. Heat Shrink Performance of Heat Shrinkable Multilayer Film>
The heat-shrinkable multilayer film 100 is immersed in warm water at 70°C for 10 seconds, then immersed in water at 20°C for 10 seconds, and then taken out. The heat shrinkage in the main shrinkage direction (TD direction) is 5% or more. preferably 30% or less. Further, after being immersed in hot water at 80°C for 10 seconds and then immersed in water at 20°C for 10 seconds, the heat shrinkage rate in the main shrinkage direction when taken out is preferably 30% or more and 60% or less. is preferred. Further, after being immersed in hot water at 90°C for 10 seconds and then immersed in water at 20°C for 10 seconds, the heat shrinkage rate in the main shrinkage direction when taken out is preferably 50% or more and 70% or less. is preferred. Further, after being immersed in hot water at 98°C for 10 seconds and then immersed in water at 20°C for 10 seconds, the heat shrinkage rate in the main shrinkage direction when taken out is preferably 60% or more and 80% or less. is preferred.

When the heat shrinkage ratio is within the above range, heat shrinkage corresponding to a relatively wide temperature range becomes possible, and it can be suitably used as a heat shrinkable multilayer film.

<7. Young's modulus of heat-shrinkable multilayer film>
The heat-shrinkable multilayer film 100 is not limited to this, but is used as a base film for a label or a packaging material that is formed into a tubular shape with the main shrinkage direction as the circumferential direction, and is attached to a container such as a PET bottle, a metal can, or the like. can be For this reason, the heat-shrinkable multilayer film 100 is required to have a certain degree of rigidity so that the tubular body of the label or packaging material does not break or collapse when attached to the container. The Young's modulus of the heat-shrinkable multilayer film 100 in the direction perpendicular to the main shrinkage direction (MD direction) preferably exceeds 1.3 (GPa). Moreover, the Young's modulus in the main shrinkage direction of the heat-shrinkable multilayer film 100 preferably exceeds 1.6 (GPa).

<8. Method for producing a heat-shrinkable multilayer film>
The method of manufacturing the heat-shrinkable multilayer film 100 is not particularly limited, but a method of forming each layer simultaneously by coextrusion is preferred. When the co-extrusion method is co-extrusion using a T-die, the lamination method may be a feed block method, a multi-manifold method, or a combination of these methods.

Specifically, as a method for producing the heat-shrinkable multilayer film 100, for example, the raw materials constituting the base material 1, the intermediate layer 2, and the surface layer 3 are put into an extruder, and formed into a sheet by a die. A method of extruding, cooling and solidifying with a take-up roll, and then uniaxially or biaxially stretching may be mentioned. As the stretching method, for example, a roll stretching method, a tenter stretching method, or a combination thereof can be used. The stretching temperature varies depending on the softening temperature of the resin constituting the heat-shrinkable multilayer film 100, the shrinkage properties required for the heat-shrinkable multilayer film 100, etc., but is preferably 65°C or higher, and preferably 70°C. It is more preferably 120° C. or less, and more preferably 115° C. or less.

The draw ratio in the main shrinkage direction varies depending on the resin constituting the heat-shrinkable multilayer film 100, the drawing means, the drawing temperature, etc., but is preferably 3 times or more, more preferably 4 times or more, and 7 times or less. Preferably, 6 times or less is more preferable.

<9. Applications of the heat-shrinkable multilayer film>
The heat-shrinkable multilayer film 100 is excellent in heat-shrinkability, rigidity, transparency, and resistance to skin whitening. For this reason, the application of the heat-shrinkable multilayer film 100 is not particularly limited. Such a heat-shrinkable label can be obtained by appropriately cutting the printed heat-shrinkable multilayer film 100 into strips, for example. Both ends of the heat-shrinkable label are overlapped and sealed with a solvent, and the cylinder-shaped label is placed over a container and heat is applied through a shrink tunnel to obtain a container with the heat-shrinkable label attached. . As exemplified here, a heat-shrinkable label comprising the heat-shrinkable multilayer film according to the present disclosure is also one of the present disclosure.

<10. Features>
According to the heat-shrinkable multilayer film 100 of the present embodiment, the thickness of the surface layer 3 is 0.1% or more and 10% or less with respect to the thickness of the resin constituting the entire heat-shrinkable multilayer film 100, and the intermediate layer 2 contains an appropriate amount of petroleum resin. As a result, it is possible to prevent the part touched by the human hand from whitening due to sebum after heat shrinkage and adversely affecting the appearance. In addition, petroleum resin tends to lower the toughness and rigidity of the heat-shrinkable multilayer film. , the overall toughness and stiffness can be maintained.

Hereinafter, embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to these examples.

<1. Preparation of Examples and Comparative Examples>
Heat-shrinkable multilayer films according to Examples 1 to 9 and Comparative Examples 1 to 3 were produced as follows. Examples 1 to 9 and Comparative Examples 1 to 3 had a five-layer structure shown in FIG.

By using the components shown in Table 1 as the raw materials constituting the base material, the intermediate layer, and the surface layer, and mixing them in the ratios shown in Table 1, the base materials according to Examples 1 to 9 and Comparative Examples 1 to 3 , an intermediate layer, and a raw material composition constituting a surface layer were obtained. The raw material of the base material was common to Examples 1 to 9 and Comparative Examples 1 to 3, but the thicknesses were different. Apel APL6509T (manufactured by Mitsui Chemicals, Inc.) was used as the cyclic olefin resin for the surface layer and intermediate layer. Evolue SP1020 (manufactured by Prime Polymer Co., Ltd.) was used as the ethylene-based resin for the intermediate layer in Examples 1 to 8 and Comparative Examples 1 to 3. On the other hand, for the intermediate layer according to Example 9, no ethylene-based resin was used. Alcon P125 (manufactured by Arakawa Chemical Industries, Ltd.) was used as the petroleum resin for the intermediate layer and base material. The antiblocking agent was common to Examples 1-9 and Comparative Examples 1-3.

Subsequently, the raw material composition constituting the base material, intermediate layer, and surface layer was extruded using another extruder, the base material at a barrel temperature of 180 ° C., the intermediate layer at a barrel temperature of 210 ° C., and the surface layer at a barrel temperature of 210 ° C. The mixture was melted at 210°C, extruded from a T-die, cooled and solidified with a roll cooled to 30°C to prepare an unstretched sheet. After stretching this by 1.3 times in the MD direction with a roll type stretching machine, it is stretched by 5 times in the TD direction with a tenter type stretching machine at a temperature of 110 ° C., and each layer has a thickness shown in Table 1. It is heat-shrunk to a thickness of 40 μm. A flexible multilayer film was prepared. The "thickness (%) of the surface layer with respect to the total thickness" shown in Table 1 is the thickness (%) of the resin that constitutes one surface layer with respect to the thickness of the resin that constitutes the entire heat-shrinkable multilayer film. be.

表面層、中間層、及び基材を構成する各材料の単位は、質量％である。また、アンチブロッキング剤の単位は、質量部である。

The unit of each material constituting the surface layer, intermediate layer, and base material is % by mass. Moreover, the unit of the antiblocking agent is parts by mass.

<2. Evaluation>
Examples 1 to 9 and Comparative Examples 1 to 3 were evaluated as follows.

<2-1. Haze>
Samples of the same size were cut out from the heat-shrinkable multilayer films of Examples 1-9 and Comparative Examples 1-3, and the haze (%) was measured according to JIS K7136.

<2-2. Sebum Whitening Resistance>
A mixed reagent consisting of 50% by mass of oleic acid, 40% by mass of stearyl palmitate, and 10% by mass of squalene as a sebum equivalent is applied to both the front and back sides of a sample cut out from a heat-shrinkable multilayer film, and left at a temperature of 40 ° C. for 30 minutes. did. After that, the haze (%) was measured based on JIS K7136 and compared with the haze before application of the mixed reagent. Level 1, level 2, and level 3 were evaluated in this order for hazes with a smaller degree of increase from the haze before application of the mixed reagent. That is, level 1 indicates relatively high sebum whitening resistance, level 2 indicates acceptable sebum whitening resistance, and level 3 indicates unsatisfactory sebum whitening resistance.

<2-3. Thermal shrinkage>
A size of 100 mm long x 100 mm wide (the TD direction of the film is the vertical direction and the MD direction is the horizontal direction) from an arbitrary point on each of the heat-shrinkable multilayer films of Examples 1 to 9 and Comparative Examples 1 to 3. Three samples for measurement were cut out. Each sample for measurement was immersed in warm water for 10 seconds, and then immersed in water at 20° C. for 10 seconds. The length L1 in the TD direction and the length L2 in the MD direction of the measurement sample after being removed from the water are measured, and the thermal shrinkage rate for each direction is calculated according to the following formula, and the average of the three samples value was calculated.
Thermal shrinkage rate (%) = {(100-Ln) / 100} x 100 (n = 1, 2)
Hot water of 70° C., 80° C., 90° C., and 98° C. was used, and the thermal shrinkage rate was calculated for each of them.

<2-4. Natural Shrinkage>
100 mm long x 100 mm wide (the TD direction of the film is the vertical direction and the MD direction is the horizontal direction) from an arbitrary portion of each of the heat-shrinkable multilayer films of Examples 1 to 9 and Comparative Examples 1 to 3. A sample for thickness measurement was cut out. These were allowed to stand in a low-temperature thermostat (IL-82, manufactured by Yamato Scientific Co., Ltd.) adjusted to 40° C. for 7 days, and the natural shrinkage rate was calculated according to the same formula as the thermal shrinkage rate.

<2-5. Young's modulus>
250 mm long x 5 mm wide (the MD direction of the film is the vertical direction, and the TD direction is the horizontal direction) from an arbitrary portion of each of the heat-shrinkable multilayer films according to Examples 1 to 9 and Comparative Examples 1 to 3. A sample for thickness measurement and a sample for measurement with a size of 250 mm long×5 mm wide (where the TD direction of the film is the longitudinal direction and the MD direction is the transverse direction) were cut out. Using a measurement sample and a strograph (VE-1D manufactured by Toyo Seiki Seisakusho Co., Ltd.), the Young's modulus (GPa) in the MD and TD directions was measured according to ASTM D882.

<2-6. Tensile elongation at break>
40 mm long x 10 mm wide (the MD direction of the film is the vertical direction, and the TD direction is the horizontal direction) from an arbitrary portion of each of the heat-shrinkable multilayer films according to Examples 1 to 9 and Comparative Examples 1 to 3. A sample for thickness measurement was cut out. A sample for measurement was set in a strograph (VE-1D manufactured by Toyo Seiki Seisakusho), and the tensile elongation at break was measured according to JISK-6732. The air temperature during the measurement was 5° C., and the drawing speed was 100 mm/min. The tensile elongation at break (toughness) was evaluated as "acceptable" if it was ruptured at 100% or more, and as "fail" if it was ruptured at less than 100%.

<2-7. Blocking>
From an arbitrary portion of each of the heat-shrinkable multilayer films of Examples 1 to 9 and Comparative Examples 1 to 3, a 100 mm long x 30 mm wide (the TD direction of the film is the vertical direction, and the MD direction is the horizontal direction). Two samples for thickness measurement were cut out. Next, the two measurement samples were made to overlap each other with an area of 40 mm long×30 mm wide. Subsequently, this overlapping measurement sample was sandwiched between two glass plates, and a weight of 5 kg was placed on the overlapped portion of the sample. The sample thus set was placed in a constant temperature bath at 40° C. and left for 48 hours. After that, the sample taken out from the constant temperature bath is set in a peeling tester (Peeling Tester HEIDON-17 manufactured by Shinto Kagaku Co., Ltd.), pulled at 180 ° at a tensile speed of 200 mm / min, and peel adhesion in which the two samples peel. The strength was taken as the blocking strength. The blocking strength was evaluated as "acceptable" if it was 2000 g/cm or less, and as "impossible" if it exceeded 2000 g/cm.

<2-8. Interlayer adhesive strength>
From an arbitrary portion of each of the heat-shrinkable multilayer films according to Examples 1 to 9 and Comparative Examples 1 to 3, a size of 100 mm long × 10 mm wide (the TD direction of the film is the vertical direction, and the MD direction is the horizontal direction). A sample for thickness measurement was cut out. The measurement sample was set in a peeling tester (Peeling TESTER HEIDON-17, manufactured by Shinto Kagaku Co., Ltd.) and peeled in a 180 degree direction at a tensile speed of 500 mm / min. It was measured. The evaluation of the interlayer adhesion strength is "good" if the interlayer peeling is at the interface between the base material and the intermediate layer, and if the interlayer peeling is at the interface between the surface layer and the intermediate layer, 0.20 N / 10 mm or more is "acceptable". "

<2-9. Evaluation result>
The evaluation results are as follows.

According to the above results, it was confirmed that Examples 1 to 9 had no problem in terms of production in terms of rigidity represented by Young's modulus and had sebum whitening resistance. According to Example 8, even if the content of the ethylene-based resin in the intermediate layer is relatively high, there is no problem with the rigidity and sebum-whitening resistance, as in the other examples. It was confirmed that there were no manufacturing problems in terms of hardness, blocking, and interlayer adhesion strength. In addition, according to Example 9, even if the intermediate layer does not contain an ethylene resin, there are no manufacturing problems in terms of rigidity, sebum whitening resistance, shrinkage rate, tensile elongation at break, blocking, and interlayer adhesion strength. was confirmed. On the other hand, Comparative Example 1, in which the content of the petroleum resin in the intermediate layer is small, resulted in poor sebum-whitening resistance. On the other hand, in Comparative Example 2, in which the content of the petroleum resin in the intermediate layer was high, the Young's modulus and tensile elongation at break were inferior, and it was confirmed that the stiffness and toughness were lowered. In Comparative Example 3, it is considered that the sebum-whitening resistance deteriorated due to the large thickness ratio of the surface layer. The surface layers of Examples 6 and 7 do not contain a cyclic olefin resin. For this reason, it is considered that the interlayer adhesion strength between the surface layer and the intermediate layer was weaker than in the other examples, although within the allowable range.

1 base material 2 intermediate layer 3 surface layer

Claims (6)

a substrate having a first surface and a second surface and containing a thermoplastic resin;
an intermediate layer laminated on at least one of the first surface and the second surface of the base material;
a surface layer laminated on the intermediate layer and containing a thermoplastic resin;
with
The intermediate layer contains 50% by mass or more and 90% by mass or less of a cyclic olefin resin and 5% by mass or more and 35% by mass or less of a petroleum resin,
The thickness of the surface layer is 10% or less of the thickness of the resin constituting the entire heat-shrinkable multilayer film.
Heat-shrinkable multilayer film. The intermediate layer further contains 30% by mass or less of an ethylene-based resin,
The heat-shrinkable multilayer film according to claim 1. The surface layer contains a cyclic olefin resin,
The heat-shrinkable multilayer film according to claim 1 or 2. The intermediate layer contains 10% by mass or more and 30% by mass or less of the petroleum resin.
The heat-shrinkable multilayer film according to any one of claims 1 to 3. The intermediate layers are respectively laminated on the first surface and the second surface of the base material,
The surface layer is laminated on each intermediate layer,
The heat-shrinkable multilayer film according to any one of claims 1 to 4. A heat-shrinkable label comprising the heat-shrinkable multilayer film according to any one of claims 1 to 5.

Images