WO2018180598A1

WO2018180598A1 - Heat-shrink film

Info

Publication number: WO2018180598A1
Application number: PCT/JP2018/010468
Authority: WO
Inventors: 裕一郎勘坂; 琢磨金子; 秀太弓削; 正浩渡邉
Original assignee: タキロンシーアイ株式会社
Priority date: 2017-03-29
Filing date: 2018-03-16
Publication date: 2018-10-04
Also published as: TWI756389B; JPWO2018180598A1; TW201843221A; UY37663A; JP6934936B2; AR111191A1

Abstract

Provided is a polystyrene heat-shrink film having enhanced film stability during storage, compared with conventional polystyrene heat-shrink films, while still being provided with an excellent shrink finish, ease of separation at perforations, and ease of adhesion. The present invention is a heat-shrink film containing a polystyrene resin. The heat-shrink film has: a thermal shrinkage of 15% or less in a main shrinkage direction when being immersed in 70°C water for 10 seconds; a thermal shrinkage of 60% or more in the main shrinkage direction when being immersed in 98°C water for 10 seconds; an Elmendorf tear strength within the range of 3-10 N/mm in the main shrinkage direction; an Elmendorf tear strength within the range of 10-20 N/mm in a direction orthogonal to the main shrinkage direction; a shrinkage stress of 4.0 N/mm² or less in the main shrinkage direction when being left at 85°C for five minutes; and a shrinkage factor of 1.5% or less in the main shrinkage direction when being left at 40°C for seven days.

Description

Heat shrinkable film

The present invention relates to a heat shrinkable film.
This application claims priority based on Japanese Patent Application No. 2017-064407 for which it applied to Japan on March 29, 2017, and uses the content here.

Heat-shrinkable films are widely used as shrink wrapping containers and shrink labels. Generally, the heat-shrinkable film is cut along perforations provided on the film in advance, and is discarded and recycled separately from the container.
The heat-shrinkable film has shrinkability, printability, environmentally friendly material, strong film, and excellent shrinkage finish (for example, less wrinkles and shrinkage spots), sewing machine Excellent eye-opening properties, excellent wearability (for example, label tearing is less likely to occur during mounting), low natural shrinkage, and excellent film stability during storage (for example, storage It is required that the film does not easily wrinkle or change in dimensions.

Examples of heat-shrinkable films used for container shrink-wrapping and shrinkage labels include polyvinyl chloride-based heat-shrinkable films, polyester-based heat-shrinkable films, and polystyrene-based heat-shrinkable films (Patent Documents 1 and 2).
Polyvinyl chloride heat-shrinkable films are excellent in shrink finish, perforation opening and wearability, and have a low natural shrinkage ratio, but have problems such as the generation of toxic chlorine-containing gas during incineration. Polyester-based heat-shrinkable films are excellent in film stability during storage and waist strength, but have problems such as poor shrinkage, perforation opening, and wearability.
Polystyrene heat-shrinkable film, on the other hand, is superior in shrink finish, perforation opening, and wearability compared to films using other materials described above, but has a high natural shrinkage rate and stability of the film during storage. Has a problem with sex.

JP 2006-044219 A JP 2012-031339 A

The present invention has been made in view of the above circumstances, and has excellent shrinkage finish, perforation opening, and wearability, while compared with conventional polystyrene heat-shrinkable films. An object of the present invention is to provide a polystyrene-based heat-shrinkable film having improved film stability.

The embodiment of the present invention has the following aspects.
[1] A heat-shrinkable film containing a polystyrene-based resin, which has a heat shrinkage rate of 15% or less when immersed in water at 70 ° C. for 10 seconds and is immersed in water at 98 ° C. for 10 seconds. When soaked, the thermal shrinkage rate in the main shrinkage direction is 60% or more, the Elmendorf tear strength in the main shrinkage direction is in the range of 3 to 10 N / mm, and the Elmendorf tear strength in the direction orthogonal to the main shrinkage direction is 10 The shrinkage stress in the main shrinkage direction is 4.0 N / mm ² or less when left at 85 ° C. for 5 minutes, and the main shrinkage direction when left at 40 ° C. for 7 days. A heat-shrinkable film having a shrinkage rate of 1.5% or less.
[2] The heat-shrinkable film is formed by being stretched in the main shrinkage direction after extrusion, and the stretching has a preheating temperature of 100 ° C. or higher, a stretching temperature and a heat setting temperature of 90 ° C. or higher, and a stretching ratio of 4 The heat-shrinkable film according to [1], which is stretched to be 9 or more.

The heat-shrinkable film of the present invention has an excellent shrink finish, perforation opening, and wearability, while improving the stability of the film during storage compared to conventional polystyrene heat-shrinkable films. Yes.

The heat-shrinkable film of the present invention (hereinafter also referred to as “this film”) contains a polystyrene resin.

(Polystyrene resin)
The polystyrene resin may be any known one used for the production of heat-shrinkable films, such as styrene-butadiene copolymer, styrene-butadiene-styrene copolymer, styrene-ethylene-butadiene-styrene copolymer, Polystyrene thermoplastic elastomers such as styrene-vinyl / polyisoprene-styrene copolymer; styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate Examples thereof include impact-resistant styrene resins such as copolymers and styrene-phenyl methacrylate copolymers. Among these, 1 type may be used independently and 2 or more types may be used.

(Other resins)
This film may contain a resin other than the polystyrene-based resin as another resin as long as the effects of the present invention are not impaired. As other resin, the well-known thing used for the use of manufacture of a heat-shrinkable film may be sufficient. Examples of other resins include olefin resins (such as propylene resins), polyester resins, and acrylic resins. One of these other resin components may be used alone, or two or more thereof may be used.

(Content of resin component)
When the total mass of all resins constituting the film is 100%, the content of the polystyrene resin is preferably 50 to 100% by mass, and more preferably 80 to 100% by mass.

(Heat shrinkable film)
When this film is immersed in water at 70 ° C. for 10 seconds, the heat shrinkage rate in the main shrinkage direction (hereinafter also referred to as “heat shrinkage rate 1”) is 15% or less, and 5 to 15%. Is more preferable, and 7 to 12% is more preferable. If the thermal shrinkage rate 1 is 15% or less, the film shrinks normally by a normal steam tunnel, and wrinkles, shrinkage spots, etc. are prevented, and the shrinkage finish is good.

When this film is immersed in water at 98 ° C. for 10 seconds, the heat shrinkage rate in the main shrinkage direction (hereinafter also referred to as “heat shrinkage rate 2”) is 60% or more and 60 to 80%. Is more preferable, and 65 to 75% is more preferable. When the heat shrinkage ratio 2 is 60% or more, the shrinkage is excellent, and it is possible to mount on various containers, and it is possible to prevent mounting trouble due to insufficient shrinkage.
When this film is immersed in water at 100 ° C. for 10 seconds, the heat shrinkage rate in the main shrinkage direction (hereinafter also referred to as “heat shrinkage rate 3”) is 60% or more, and 60 to 80%. Is more preferable, and 65 to 75% is more preferable. When the heat shrinkage ratio 3 is 60% or more, the shrinkage is excellent, and it is possible to mount on various containers, and it is possible to prevent mounting trouble due to insufficient shrinkage.
The difference (Δ ₂₃ ) between the heat shrinkage rate 2 and the heat shrinkage rate 3 is preferably within ± 1%. If delta ₂₃ is within 1% ±, it is possible to mount to various containers, a mounting trouble due to shrinkage shortage can be further prevented.

In the present invention, “thermal shrinkage” is a value measured at 70 ± 0.5 ° C., 98 ± 0.5 ° C., and 100 ± 0.5 ° C. according to JIS Z1709.

The Elmendorf tear strength of the main shrinkage direction (hereinafter also referred to as “TD direction”) of the film is in the range of 3 to 10 N / mm, preferably in the range of 3 to 8 N / mm. / Mm is more preferable. If the Elmendorf tear strength in the MD direction is in the range of 3 to 10 N / mm, the perforation is excellent. Here, “excellent perforation opening” means, for example, when a label using this film is separated by a perforation provided along a direction perpendicular to the main shrinkage direction of the label. It means that the label can be easily peeled off from the container without tearing the label.

The Elmendorf tear strength of the film in the direction orthogonal to the main shrinkage direction (hereinafter also referred to as “MD direction”) is in the range of 10 to 20 N / mm, and preferably in the range of 10 to 17 N / mm. More preferably, it is in the range of 10 to 14 N / mm. If the Elmendorf tear strength in the TD direction is in the range of 10 to 20 N / mm, the perforation is excellent.

In the present invention, “Elmendorf tear strength” is a value obtained by dividing a value measured in the MD direction and the TD direction by the thickness of the film according to JIS K7128-2.

This film, when left at 85 ° C. 5 min, main shrinkage direction of the shrinkage stress is at 4.0 N / mm ² or less, preferably 3.5 N / mm ² or less, 3.0 N / mm More preferably, it is ² or less. If the shrinkage stress in the main shrinkage direction is 4.0 N / mm ² or less, the label can be prevented from breaking from the perforation when the label using this film is attached to a container or the like. Excellent.

In the present invention, the term “shrinkage stress” refers to a sample piece having a length in the main shrinkage direction of 80 mm and a width of 25 mm in an oven at 85 ° C. in a state where the sample piece is held on a chuck equipped with a load cell at a distance of 50 mm between chucks. It is the maximum stress per unit cross-sectional area measured when it is put in and left for 5 minutes.

When this film is left at 40 ° C. for 7 days, the shrinkage in the main shrinkage direction (hereinafter also referred to as “natural shrinkage”) is 1.5% or less and 1.2% or less. Preferably, it is 1.0% or less. If the natural shrinkage is 1.5% or less, shrinkage during storage can be reduced, and the film during storage is less likely to wrinkle or change in dimensions, and the stability of the film during storage is excellent.

The natural shrinkage rate is a shrinkage rate in the main shrinkage direction when a sample having a length of 500 mm in the main shrinkage direction is left at 40 ° C. for 7 days, and is a value calculated by the following formula (I).
Natural shrinkage [%] = {[(500) − (length after standing [mm])] / (500)} × 100 (I)

The present film may be a single layer film made of polystyrene resin, or may be a multilayer film having an outermost layer made of polystyrene resin and another layer made of polystyrene resin and another resin. The film may be a transparent film or an opaque film or a colored film such as white from the viewpoint of printability.
The heat-shrinkable film may contain additives such as a filler, a stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, and a lubricant.

In the case of a single layer film, the thickness of the film is preferably 20 to 80 μm, more preferably 40 to 60 μm.

In the case of a multilayer film, the thickness of the outermost layer of this film is preferably 2 to 8 μm, more preferably 4 to 6 μm, and the total thickness of other layers is preferably 18 to 78 μm, more preferably 16 to 54 μm. .

(Example of use)
The heat-shrinkable film is not particularly limited, but is mainly used as a label for a bottle container. When using as a label, in order to improve the designability, the heat shrinkable film may be printed.
As a method for attaching a label made of a heat-shrinkable film to a bottle container, for example, the heat-shrinkable film is cut into a predetermined length, and the ends of the cut film are joined to form a cylindrical body, An example is a method in which a bottle container is inserted into a cylindrical body and then heated to shrink.

(Method for producing heat-shrinkable film)
This film can be obtained by a known method (T-die method, inflation method or the like, in the case of a multilayer film, a coextrusion method thereof). For example, but not limited to this, the material is extruded in a flat shape or a tube shape from a die heated to 160 to 240 ° C., and the resulting unstretched product has a main shrinkage direction (TD direction) and Biaxial stretching is preferably performed in an orthogonal direction (MD direction). In this case, sequential biaxial stretching in the MD direction and TD direction may be used, or simultaneous biaxial stretching may be used.
In addition, it is preferable to perform extending | stretching of TD direction at 3 processes, a preheating process, an extending process, and a heat setting process.
The film of this embodiment is stretched at a preheating temperature of 100 ° C. or higher, a stretching temperature and a heat setting temperature of 90 ° C. or higher, and a draw ratio of 4.9 or higher in the step of performing the stretching process in the TD direction of the production. It is preferable to do so. By performing the stretching step under these conditions, the natural shrinkage rate of the film can be set to an appropriate value.

(Function and effect)
As described above, the heat-shrinkable film of the present invention satisfies the above-mentioned physical property values, so that it has an excellent shrink finish, perforation opening, and wearability, while having a conventional polystyrene heat-shrinkability. Compared to the film, the stability of the film during storage is improved.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by the following description.
The measurement of each physical property value of the heat-shrinkable film in the examples and the evaluation of each evaluation item were performed according to the following description and criteria.

(Heat shrinkage)
According to JIS Z1709, 70 ± 0.5 ° C. (measurement temperature of “heat shrinkage rate 1”), 98 ± 0.5 ° C. (measurement temperature of “heat shrinkage rate 2”) and 100 ± 0.5 ° C. (“ The heat shrinkage rate of the heat-shrinkable film at a measurement temperature of 3 ”was measured.

(Elmendorf tear strength)
In accordance with JIS K7128-2, the tear force was measured in the MD direction and TD direction of the heat-shrinkable film, and calculated by dividing each by the thickness of the heat-shrinkable film.

(Shrinkage stress)
For a sample piece having a length in the main shrinkage direction of 80 mm and a width of 25 mm, the maximum value of stress measured when left for 5 minutes at 85 ° C. was defined as shrinkage stress.

(Natural shrinkage)
A sample having a length of 500 mm in the main shrinkage direction of the heat-shrinkable film was allowed to stand at 40 ° C. for 7 days, and then the length of the sample was measured and calculated by the following formula (I).
Natural shrinkage [%] = {[(500) − (length after standing [mm])] / (500)} × 100 (I)

A cylindrical body in which the heat-shrinkable film is cut into a predetermined width and length, and the ends of the cut heat-shrinkable film are joined to each other so that the main shrinkage direction of the heat-shrinkable film is the circumferential direction. Created a label. Then, after inserting a bottle container in this cylindrical body, the label was mounted | worn by making it heat-shrink. The appearance of the label after heat shrinkage was visually observed to evaluate shrinkage finish and wearability.

(Shrink finish)
The presence or absence of wrinkles and shrinkage spots on the label after heat shrinkage was determined by visual observation, and evaluated according to the following criteria.
○: Wrinkles and contraction spots are not generated.
X: Wrinkles or shrinkage spots are generated.

(Mountability)
The presence or absence of rupture on the label after heat shrinkage was determined by visual observation, and evaluated according to the following criteria.
○: No rupture occurred.
X: Rupture has occurred.

(Perforation opening)
A label of the above-described cylindrical body in which perforations were previously provided in a direction perpendicular to the main contraction direction was attached to the bottle container. However, the perforations were formed by putting holes having a length of 1 mm at intervals of 4 mm, and two perforations were provided in the direction of the perforation (MD direction) over a width of 20 mm and a length of 200 mm. Thereafter, the perforation of the label was torn with a fingertip, and it was determined whether the label was torn along the perforation provided in the MD direction.
○: The label was torn along the perforation.
X: The label was not torn along the perforation, or the label was torn in a direction other than the TD direction.

(Stability of film during storage)
After the heat-shrinkable film was stored at 40 ° C. for 7 days, the presence or absence of wrinkles and dimensional changes on the heat-shrinkable film was visually determined, and the stability of the film during storage was evaluated according to the following criteria.
○: No wrinkle or dimensional change occurs compared to the conventional product.
X: Wrinkles or dimensional changes occur in the same way as conventional products.

<Example 1>
(Raw material for polystyrene heat-shrinkable film)
The polystyrene-based heat-shrinkable film of the examples described below has a three-layer structure composed of the following components.
For the intermediate layer of the polystyrene-based heat-shrinkable film, a mixture of SBC (A) and SBC (B), which is a styrene-butadiene copolymer, was used as a raw material.
For both outer layers of the polystyrene heat-shrinkable film, a mixture of a styrene-butadiene copolymer (SBC (A)) and an impact-resistant polystyrene resin (referred to as “HiPS” in Table 1) was used as a raw material.
Table 1 shows the Vicat softening point and melt mass flow rate (referred to as “MFR” in Table 1) of each component, and the component ratio of each layer.

(Manufacture of polystyrene heat-shrinkable film)
The raw materials of the polystyrene heat-shrinkable film were mixed in the blending amounts shown in Table 1 and coextruded from a three-layer die kept at 200 ° C. to obtain a three-layer polystyrene film original. The thickness of both outer layers of this film original was 34 μm, and the thickness of the intermediate layer was 270 μm. Next, this film original fabric was stretched 1.35 times in the MD direction at 85 ° C. to obtain a stretched film made of polystyrene resin having a thickness of 250 μm. Furthermore, after pre-heating the film that has been stretched in the MD direction at 105 ° C. for 10 seconds, the film was stretched 5.00 times in the TD direction at 98 ° C., and then kept at 97 ° C. for about 15 seconds. Then, a polystyrene heat-shrinkable film was obtained.

<Comparative Example 1>
A polystyrene heat-shrinkable film was obtained in the same manner as in Example 1 except that the stretching conditions were changed as shown in Table 2.

<Comparative Example 2>
(Raw material for polyester heat-shrinkable film)
The polyester-based heat-shrinkable film of Comparative Example 2 described below has a single-layer structure and is a polyester-based resin (referred to as “polyester (A)” in Table 1) that is P-SF manufactured by SK Chemical Company. A mixture of silica gel master batches (referred to as “silica gel MB” in Table 1) which is EPM7E-325 manufactured by Sumika Color was used as a raw material.
Table 1 shows the glass transition point (referred to as “Tg” in Table 1) and intrinsic viscosity (referred to as “IV” in Table 1) and the component ratio of the components constituting the film of the polyester A used.

(Manufacture of polyester heat-shrinkable film)
The raw materials of the polyester heat-shrinkable film were mixed in the blending amounts shown in Table 1, and extruded from a die kept at 260 ° C., to obtain a polyester film original fabric having a single-layer structure having a thickness of 200 μm. A polyester heat-shrinkable film was obtained in the same manner as in Example 1 except that this single-layer structure film was used and the stretching conditions were changed as shown in Table 2.

About the heat-shrinkable film obtained in each example, the result of having measured each physical-property value by said method is shown in Table 3.
In addition, Table 4 shows the results of evaluation based on the above criteria for each evaluation item.

As shown in Tables 3 and 4, the polystyrene heat-shrinkable film of Example 1 is more stable during storage than the polystyrene heat-shrinkable film of Comparative Example 1 in which the natural shrinkage rate exceeds 1.5%. Improved.
The polyester heat-shrinkable film of Comparative Example 2 using the polyester-based resin was inferior to the heat-shrinkable film of Example 1 in shrink finish, wearability, and perforation opening.

Claims

A heat-shrinkable film containing a polystyrene resin,
The heat shrinkage rate in the main shrinkage direction when immersed in water at 70 ° C. for 10 seconds is 15% or less,
The heat shrinkage rate in the main shrinkage direction when immersed in water at 98 ° C. for 10 seconds is 60% or more,
Elmendorf tear strength in the main contraction direction is in the range of 3-10 N / mm,
The Elmendorf tear strength in the direction perpendicular to the main contraction direction is in the range of 10-20 N / mm,
The shrinkage stress in the main shrinkage direction when left at 85 ° C. for 5 minutes is 4.0 N / mm 2 or less,
A heat-shrinkable film having a shrinkage ratio in the main shrinkage direction of 1.5% or less when left at 40 ° C. for 7 days.
The heat-shrinkable film is formed by stretching in the main shrinkage direction after extrusion, and the stretching has a preheating temperature of 100 ° C. or more, a stretching temperature and a heat setting temperature of 90 ° C. or more, and a stretching ratio of 4.9 or more. The heat-shrinkable film according to claim 1, which is stretched so that