JP2017137063A - Heat-shrinkable film and heat-shrinkable package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable film that can be easily opened without using scissors or a cutting tool, and has excellent designability.SOLUTION: A heat-shrinkable film has an MD direction and a TD direction, an opening mark part formed by holes and/or slits is provided, Elmendorf tear strength in the TD direction which is measured in the state where the film does not have the opening mark part is 1 N or less, a plurality of holes and/or slits are formed on the opening mark part at least in two rows along the MD direction, the length of the opening mark part in the TD direction is 5 to 20 mm, and the opening mark part is formed inside both side edge parts along the MD direction of the heat-shrinkable film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat-shrinkable film and a heat-shrinkable package that can be used for packaging applications, for example.

  Conventionally, canned beverages, plastic bottle beverages, paper-packed beverages and the like have been transported in a form that is easy to circulate in units of 24 cans, 6 bottles, etc., and have been opened at retail stores and arranged in stores. However, there is a problem that a large amount of cardboard must be disposed after unpacking. In recent years, there are increasing cases in which consumers purchase cardboards at mass merchandise stores and take them home, and the disposal of cardboards at home is also a problem.

  In view of the above problems, a method of collecting and packaging products with a heat-shrinkable film that is inexpensive and easy to discard has been proposed. For example, Patent Document 1 states that “a polyethylene-based multilayer film is stretched at a stretching ratio of 3.0 times or more in both MD (flow direction) and TD (vertical direction) by biaxial stretching and then heated to 60 to 100 ° C. by hot roll treatment. A polyethylene-type heat-shrinkable multilayer film for integrated packaging obtained by stretching 1.1 to 3.0 times MD at a temperature of 5 "is disclosed. When producing a heat-shrinkable package using such a heat-shrinkable film, it can be produced by, for example, sleeve-wrapping an article to be packaged with a heat-shrinkable film and then heat-shrinking.

  Patent Document 2 states that “in a shrink film package in which an article to be packaged is wrapped with a heat-shrinkable film (1), the film (1) is on a straight line aligned in multiple rows over the entire surface. There is disclosed a “shrink film packaging body” characterized in that a material having a large number of holes (2) is used (claim 1).

JP 2011-116033 A JP 2012-35877 A

  In the above-mentioned sleeve packaging, since a so-called sleeve opening (substantially circular opening) remains in the heat shrink package, the film is often broken by hooking or tearing a finger on the sleeve opening at the time of opening. For this reason, the sleeve mouth becomes thicker than other parts due to shrinkage, and it is difficult to break when the sleeve mouth is wrinkled by hot air during heat shrinkage. Is often done. Such a decrease in openability is significant when a highly viscous polyethylene resin is used. However, if a bag or blade is used to open a heat-shrink package using a heat-shrinkable film, the product that is the contents may be damaged or injured. Therefore, in order to guide the opening direction, there is a case where a perforation is formed so as to be easily cut along the perforation. However, in this case, it has not been an effective means in mail order sales, etc., in which the packages are not the same. In addition, the technique disclosed in Patent Document 2 can improve the openability regardless of the position and direction by drilling a large number of holes over the entire film surface. Therefore, there is a problem that the production efficiency is poor and the design of the appearance is also lowered.

  The present invention has been made in view of the above, and an object of the present invention is to provide a heat-shrinkable film that can be easily opened without using a scissors or a knife, and that is excellent in design. To do.

  As a result of intensive studies to achieve the above object, the present inventor has provided a tear mark having a specific tear strength and a hole and / or slit formed at a predetermined portion of the heat shrink film. Thus, the inventors have found that the above object can be achieved and have completed the present invention.

That is, the present invention includes, for example, the subject matters described in the following sections.
Item 1. A heat shrink film having an MD direction and a TD direction,
An opening mark formed by a hole and / or a notch is provided,
The Elmendorf tear strength in the TD direction measured in a state without the opening mark portion is 1 N or less,
The opening mark portion is formed by arranging a plurality of holes and / or notches along the MD direction,
The said opening mark part is a heat-shrink film currently formed inside the both ends along the MD direction of the said heat-shrink film.
Item 2. The heat-shrinkable film according to Item 1, wherein the plurality of holes and / or notches are formed in at least two rows along the MD direction.
Item 3. Item 3. The heat-shrinkable film according to Item 1 or 2, wherein the opening mark portion has a length in the TD direction of 5 to 20 mm.
Item 4. The side ends have side edges along the MD direction,
A blank area set with a length exceeding at least 30 mm from each of the side edges toward the TD direction is provided,
The heat-shrinkable film according to any one of Items 1 to 3, wherein the opening mark portion is provided with the margin area therebetween.
Item 5. A plurality of the opening mark portions are provided,
Item 5. The heat shrinkable film according to any one of Items 1 to 4, wherein each of the opening mark portions is arranged along the MD direction with a predetermined interval therebetween.
Item 6. The heat-shrinkable film according to any one of Items 1 to 5, wherein the opening mark portion has a display portion that guides the opening in the TD direction.
Item 7. Item 7. The heat-shrinkable film according to any one of Items 1 to 6, which is formed of a resin containing a polyolefin-based resin containing a cyclic olefin and / or an ionomer.
Item 8. Item 8. The heat shrinkable film according to Item 7, wherein the polyolefin resin includes a polyethylene resin.
Item 9. A heat shrink package using the heat shrink film according to any one of items 1 to 8.

  Since the heat-shrinkable film of the present invention has an opening mark portion formed by a hole and / or a cut at a predetermined location, for example, when used as a packaging film, it does not need to use a bag or a knife. It can be easily opened and is also excellent in design.

It is a schematic plan view which shows an example of embodiment of the heat shrink film of this invention. It is a schematic plan view which shows the other example of the heat shrink film of this invention. It is a schematic plan view which shows the other example of the heat shrink film of this invention. It is a schematic plan view which shows the other example of the heat shrink film of this invention. It is a schematic plan view which shows the other example of the heat shrink film of this invention. It is a schematic plan view which shows the other example of the heat shrink film of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a plan view showing an example of an embodiment of the heat shrink film A. FIG.

  The heat shrink film A of this embodiment is formed to have an MD direction and a TD direction. In the present specification, the MD direction and the TD direction of the heat-shrinkable film A are indicated by arrows a and b in the drawing, respectively. Hereinafter, they are expressed as MD direction a and TD direction b.

  The MD direction a and the TD direction b here are, for example, when the heat shrink film A is manufactured by an inflation method, the film winding direction is the MD direction a, and the MD direction a and the heat shrink film A The direction perpendicular to the surface is the TD direction b.

  The heat-shrinkable film A of this embodiment is provided with an opening mark portion 12 formed with holes and / or cuts 2 and has an Elmendorf tear strength in the TD direction b measured in a state where the opening mark portion 12 is not provided. The opening mark part 12 is formed by arranging a plurality of holes and / or cuts 4 along the MD direction a, and the opening mark part 12 is along the MD direction a of the heat shrink film A. It is formed inside the both ends.

  Hereinafter, the aspect of the heat-shrink film A of embodiment of FIG. 1 is demonstrated further more concretely.

  Each side end portion along the MD direction of the heat-shrinkable film A has side end sides 17 extending along the MD direction. The pair of side edges 17 are usually formed in parallel with the MD direction.

  The opening mark portion 12 is formed by a hole and / or a notch 2. That is, the unsealing mark part 12 may be formed only with a hole, may be formed only with a notch, and may be formed with both a hole and a notch. In the present specification, the hole is denoted by reference numeral 2b (that is, the hole 2b), and the notch is denoted by reference numeral 2a (that is, the notch 2a), and the notch 2a and the hole 2b. Are collectively referred to as holes and / or notches 2.

  Both the cut 2a and the hole 2b can be formed through the heat-shrinkable film A.

  The shape of the hole 2b in plan view is not particularly limited, and examples thereof include a circle, an ellipse, and a polygon. For example, when the hole 2b is formed in a circular shape, the diameter may be 0.5 to 2 mm, and preferably 0.5 to 1 mm.

  The shape of the notch 2a is not particularly limited, and can be formed in a straight line shape, a curved line shape, or the like. Alternatively, the cut 2a may be formed by bending, and examples thereof include an L shape and a V shape. The cut 2a may be a perforation, for example. The overall length of the cut 2a can be 1 to 20 mm, and is preferably 1 to 10 mm.

  In the embodiment of FIG. 1, the unsealing mark portion 12 is oriented so that the linear cut 2a is parallel to the MD direction a.

  A plurality of holes and / or notches 2 are formed on the surface of the heat shrink film A, and are formed along the MD direction. Thereby, the opening mark part 12 is formed.

  The plurality of holes and / or notches 2 may be formed in at least two rows along the MD direction. Specifically, in the embodiment of FIG. 1, the notches 2a are formed in at least two rows over the entire length along the MD direction a, whereby the opening mark portions 12 are formed over the entire length in the MD direction a.

  The interval (that is, the pitch) between adjacent holes and / or notches 2 along the MD direction a is not particularly limited. Similarly, the interval (that is, the pitch) between adjacent holes and / or notches 2 along the TD direction b is not particularly limited. The intervals between adjacent holes and / or notches 2 may be all equal or may not be equal.

  Since the heat-shrinkable film A has the opening mark portion 12, for example, the heat-shrinkable film A is easily torn in the TD direction by tearing the opening mark portion 12 in one or both sides in the TD direction. Therefore, when the heat shrink film A is used as a packaging application, the contents can be easily taken out by tearing the opening mark portion 12. Specifically, the film is torn into a tape shape by making a hole with a finger using the space formed between the product inside the package and the mount, and pinching and pulling the heat shrink film A. Thereby, it becomes possible to easily take out the product as the contents without damaging it.

  In the embodiment of FIG. 1, the opening mark portion 12 is formed over the entire length of the heat shrink film A in the MD direction a.

  The width D of the unsealing mark portion 12, that is, the length in the TD direction b of the unsealing mark portion 12 is not particularly limited, but may be 5 to 20 mm, for example. In this case, the strength of the heat-shrinkable film A is not easily lowered, and the design is not easily lowered. Moreover, when the heat-shrinkable film A is used for packaging, it can be opened more easily. It becomes possible to do.

  In the heat-shrinkable film A of this embodiment, the opening mark part 12 is formed inside the both end parts along the MD direction a. That is, the opening mark part 12 is formed inside the end part on the side end side 17 side. Thus, when the heat shrink film A is used as a packaging application, the opening can be easily performed. As long as the opening mark portion 12 is inside the end portion on the side end side 17 side, the arrangement location is not particularly limited, but it is preferably formed in a region exceeding a certain length from the side end side 17. .

  For example, as shown in FIG. 1, a blank area 11 set at a constant distance L from the side edge 17 of the heat shrink film A toward the TD direction b is provided, and the unsealing mark portion 12 is separated by the blank area 11. Is preferably provided. In this case, when the heat shrink film A is used as a packaging application, the opening operation becomes easier.

  Said distance L can be 30 mm or more, for example. By having a blank area set with a length exceeding at least 30 mm from each of the side edges 17 and 17 in the TD direction, it is possible to avoid an area where the shrinkage is greatest and the film thickness is increased. The ease of work is further improved. The distance L is more preferably 40 mm or more.

  In particular, it is preferable that the opening mark portion 12 is provided so as to span the central portion in the TD direction of the heat shrink film A. In this case, when the heat shrink film A is used for packaging, the opening operation is easy. In addition, the heat shrink film A is excellent in design.

  The heat-shrinkable film A has an Elmendorf tear strength in the TD direction measured in a state where the opening mark portion 12 is not provided, of 1 N or less. In this case, the tearability in the TD direction is improved, so that the opening operation is further facilitated. The Elmendorf tear strength is more preferably 0.1 to 0.8N. The tear strength as used in this specification means the value measured by the Elmendorf method based on JISK7128-2. In addition, the Elmendorf tear strength in the MD direction is not limited, but is preferably 0.1 to 2N, and more preferably 2 to 5N. By setting the Elmendorf tear strength within the above range, the heat-shrinkable film A has an excellent binding force and can be easily torn and taken out the contents.

  As a modification of the embodiment of FIG. 1, it can be an I-shaped or an inverted H-shaped cut. The tear directionality in the TD direction b is stabilized by making the cut into an I-shape or an inverted H-shape.

  FIG. 2 shows another embodiment of the heat shrink film A of the present embodiment. In this embodiment, the unsealing mark portion 12 is formed by providing a plurality of straight cuts 2a as in the embodiment of FIG. 1, but the direction of the straight cuts 2a is the embodiment of FIG. Is different. Specifically, in the embodiment of FIG. 1, a plurality of linear notches 2a are arranged in parallel with the MD direction a, whereas in the embodiment of FIG. The notches 2a are arranged so as to be orthogonal to the MD direction a, that is, parallel to the TD direction b. In this case, when the heat-shrinkable film A is used for packaging and is opened, the heat-shrinkable film A can be easily opened with respect to the TD direction.

  In addition, in the heat-shrink film A of embodiment of FIG. 2, except the point from which the direction of the linear notch 2a differs as mentioned above, it is the same as that of the structure of the heat-shrink film A which concerns on embodiment of FIG. .

  FIG. 3 shows another embodiment of the heat shrink film A of this embodiment. In this embodiment, the heat-shrinkable film A is provided with a plurality of opening mark portions 12, and each opening mark portion 12 (that is, the plurality of opening mark portions 12) is spaced apart along the MD direction a. However, it is arrange | positioned over MD direction a full length. About another structure, it is the same as that of the structure of the heat-shrink film A which concerns on embodiment of FIG. The interval between the opening mark portions 12 adjacent in the MD direction a is not particularly limited.

  FIG. 4 shows another embodiment of the heat shrink film A of the present embodiment. In this embodiment, as in the embodiment of FIG. 3, a plurality of opening mark portions 12 are provided, and each opening mark portion 12 is arranged over the entire length in the MD direction a with a predetermined interval along the MD direction a. Yes.

  In the embodiment of FIG. 4, the unsealing mark portion 12 has a linear cut 2 a, and in particular, the direction of some of the straight cuts 2 a is parallel to the MD direction a, and the other partial straight lines The direction of the notch 2a is parallel to the TD direction b. Thus, by providing one straight cut 2a and the other straight cut 2a so as to be orthogonal, it becomes easier to make a hole with a finger, and the reliability of tearing in the TD direction b is improved. Therefore, it can be opened more easily. The configuration of the heat-shrinkable film A in the embodiment of FIG. 4 is the same as the configuration of the heat-shrinkable film A in the embodiment of FIG. 3 except that the opening mark portion 12 is formed as described above. is there.

  In addition, as a further modification of the embodiment of FIG. 4, a notch configuration in which the opening mark portion 12 is bent into a “<” character and / or a “>” character may be used. In this case, since it becomes easier to tear in the TD direction more reliably, it can be opened more easily.

  FIG. 5 shows another embodiment of the heat shrink film A of the present embodiment. In this embodiment, as in the embodiment of FIG. 3, a plurality of opening mark portions 12 are provided, and each opening mark portion 12 is arranged over the entire length in the MD direction a with a predetermined interval along the MD direction a. Yes. Further, the opening mark portion 12 is formed not by the notch 2a but by the hole 2b. The configuration of the heat-shrinkable film A in the embodiment of FIG. 5 is the same as the configuration of the heat-shrinkable film A in the embodiment of FIG. 3 except that the opening mark portion 12 is formed as described above. is there.

  FIG. 6 shows another embodiment of the heat shrink film A of this embodiment. In this embodiment, as in the embodiment of FIG. 3, a plurality of opening mark portions 12 are provided, and each opening mark portion 12 is arranged over the entire length in the MD direction a with a predetermined interval along the MD direction a. Yes.

  In particular, in the embodiment of FIG. 6, the opening mark part 12 has a display part 20 that guides the user to open in the TD direction b. Specifically, in the heat-shrinkable film A of FIG. 6, the unsealing mark portion 12 is formed such that a plurality of cuts 2a are arranged in parallel with the TD direction b, and the plurality of cuts 2a as a whole are in the TD direction b. Simulates an arrow indicating both directions. As a result, when the heat shrink film A is to be torn starting from the opening mark portion 12, the opening mark portion 12 is visually recognized as the display portion 20, so that the heat shrink film A is naturally heated in the TD direction b. It becomes possible to guide the shrink film A to tear. Therefore, when the heat-shrinkable film A is used as a packaging application, it can be easily opened, and the heat-shrinkable film A can be peeled off in a tape shape.

  The heat-shrinkable film of each of the embodiments described above can be used for applications in which the object to be packaged is heat-shrinked after being sleeve-wrapped. When wrapping the sleeve, the wound sleeve method in which the heat shrink film is wrapped around the packaged object, or the heat shrink film drawn from the two raw rolls is heat-sealed and then placed in front of the packaged object. There is a front-and-back sealing method in which the object to be packaged is pressed into a curtain-shaped heat-shrink film, wrapped in a cylinder shape from the top and bottom of the object to be packaged, and heat sealed at the rear of the object to be packaged. In any method, the heat-shrinkable film is continuously drawn out from the raw roll wound in a roll shape, and has a pair of side edges parallel to the MD direction. Regardless of whether the sleeve packaging is a wound sleeve or a front / rear seal, the heat-shrinkable film is sleeve-wrapped so as to be wound in the MD direction. That is, the side edge can be formed as a sleeve opening of the heat-shrinkable package when heat-shrinking after sleeve packaging.

  Next, the material of the heat shrink film A will be described.

  The material for forming the heat-shrinkable film A is not particularly limited, and examples thereof include a film formed of a resin. The kind of resin is not specifically limited, For example, well-known resin is mentioned.

  The resin is preferably formed of a resin including a polyolefin-based resin containing a cyclic olefin and / or an ionomer.

  It does not specifically limit as polyolefin resin, For example, polyethylene and a polypropylene can be illustrated.

  As the polyethylene resin, a resin containing 30% by mass or more of low density polyethylene (LDPE) is preferable in order to obtain a high heat shrinkage rate. More specifically, LDPE is more preferably 35% by mass or more, and may be 100% by mass of LDPE. When LDPE and other polyethylene resins are used in combination, for example, linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), etc. may be used. it can. By using LDPE in combination with other polyethylene resins, the strength of the heat shrinkable film can be improved. These polyethylene resins other than LDPE can be used alone or in admixture of two or more.

LDPE is a polyethylene resin (homopolyethylene) having a density in the range of 0.910 to 0.930 g / cm ³ , and examples thereof include those produced by high-pressure radical polymerization using a radical initiator. In addition, the density in this specification is the value measured on the conditions of JIS K7112: 1999 underwater substitution method (A method) and 25 degreeC.

  In order to obtain the excellent binding property (shrinkability) and film forming stability of the heat-shrinkable film, the melt flow rate (MFR) of LDPE is preferably 0.05 to 2.0 g / 10 minutes, 2.0 g / 10 min is more preferable, and 0.2 to 1.0 g / 10 min is still more preferable. The MFR in the present specification is a value measured under the conditions of JIS K7210: 1999, Method A, 190 ° C., and load 21.18N unless otherwise specified.

  There is no clear distinction between LLDPE and MDPE, but there are cases where they are distinguished for convenience depending on density. LLDPE and MDPE can be obtained by copolymerizing ethylene and α-olefin using a single-site catalyst such as Ziegler catalyst, metallocene catalyst, and density by adjusting the type and amount of α-olefin. The range can be controlled.

  Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like. These α-olefins can be used alone or in combination of two or more.

LLDPE has a density of 0.870 to 0.945 g / cm ^{3 in} a wide range of products on the market and is not particularly limited in the present invention, but is 0.900 to 0.00 in terms of obtaining high cohesiveness in an integrated package. 940 g / cm ³ is preferable, and 0.910 to 0.940 / cm ³ is more preferable. On the other hand, if the MFR of LLDPE is too small, the film forming property becomes unstable, and if it is too large, the excellent binding property of the heat-shrinkable film cannot be obtained, so 0.1 to 4.0 g / 10 min is preferable. 5 to 2.0 g / 10 min is more preferable.

MDPE refers to LLDPE having a density of about 0.930 to 0.945 / cm ³ , and MFR is preferably about 0.05 to 2.0 g / 10 min.

Is not particularly limited as HDPE, density is preferably ^{0.940~0.960g / cm 3, 0.945~0.960g / cm} 3 is more preferable. Moreover, in order to obtain the excellent binding property and film forming stability of the heat shrinkable film, the melt flow rate (MFR) of HDPE is preferably 0.1 to 4.0 g / 10 min, and preferably 0.5 to 2. 0 g / 10 min is more preferable.

  The cyclic olefin system is not particularly limited as long as it contains a cyclic olefin in the polymer. A cycloolefin homopolymer (hereinafter also referred to as “COP”), an ethylene-cycloolefin copolymer, etc. (hereinafter, And an ethylene-cycloolefin copolymer (also referred to as “COC”). COC is preferable in that the heat shrinkability in the TD direction of the heat shrinkable film can be improved.

The ethylene-cyclic olefin copolymer is not limited, but if the ethylene content as a monomer component is 25% by mass or more and the glass transition point (Tg) is 120 ° C. or less, a polyethylene resin such as LDPE or LLDPE Dispersibility in the TD direction is improved, and heat shrinkability in the TD direction is improved, which is preferable. The density of the ethylene-cyclic olefin copolymer is preferably about 0.95 to 1.05 g / cm ³ , and the MFR measured at 190 ° C. and 21.18 N is preferably about 0.05 to 4.0 g / 10 minutes. .

Examples of the cyclic olefin as the monomer component include vinylcycloalkanes and derivatives thereof having a cycloalkane having 3 to 20 carbon atoms, monocycloalkenes and derivatives thereof having 3 to 20 carbon atoms, and bicyclo [2.2. 1] -2-heptene (norbornene) and its derivatives, tricyclo [4.3.0.1 ^2,5 ] -3-decene and its derivatives, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene and its derivatives, pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13] -4-pentadecene and its derivatives, pentacyclo [7.4.0.1 ^2,5. 1 ^9,12 . 0 ^8,13] -3-pentadecene and its derivatives, pentacyclo [8.4.0.1 ^2,5. 1 ^9,12 . 0 ^8,13] -3-hexadecene and its derivatives, pentacyclo [6.6.1.1 ^{3, 6.} 0 ^2,7 . 0 ^9,14] -4-hexadecene and derivatives thereof, hexacyclo [6.6.1.1 ^{3, 6.} 1 ^10,13 . 0 ^2,7 . 0 ^9,14] -4-heptadecene and its derivatives, heptacyclo [8.7.0.1 ^2,9. 1 ^4,7 . 1 ^{11, 17} . 0 ^3,8 . 0 ^12,16 ] -5-eicosene and its derivatives, heptacyclo [8.7.0.1 ^3,6 . 1 ^{10, 17} . 1 ^{12, 15} . 0 ^2,7 . 0 ^11,16 ] -4-eicosene and its derivatives, heptacyclo [8.8.0.1 ^2,9 . 1 ^4,7 . 1 ^{11, 18} . 0 ^3,8 . 0 ^12,17 ] -5- ^Heneicosene and its derivatives, octacyclo [8.8.0.1 ^2,9 . 1 ^4,7 . 1 ^{11, 18} . 1 ^13,16 . 0 ^3,8 . 0 ^12,17] -5-docosene and its derivatives, Nonashikuro [10.9.1.1 ^{4, 7.} 1 ^13,20 . 1 ^{15, 18} . 0 ^2,10 . 0 ^3,8 . 0 ^{12, 21} . 0 ^14,19] -5-pentacosene and its derivatives. The cyclic olefin may be subjected to a hydrogenation treatment as disclosed in JP 2007-291364 A.

Examples of the ethylene-cyclic olefin copolymer include ethylene-bicyclo [2.2.1] -2-heptene copolymer, tricyclo [4.3.0.1 ^2,5 ] -3-decene-ethylene copolymer. Polymer, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] -3-dodecene-ethylene copolymer and the like. In addition, as the ethylene-cyclic olefin copolymer, commercially available products may be used, for example, Apel (trade name) manufactured by Mitsui Chemicals, Inc. TOPAS (trade name) manufactured by Topas Advanced Polymers GmbH, etc. It is done.

The cycloolefin homopolymer is not particularly limited, and if the glass transition point (Tg) is 120 ° C. or less, the dispersibility in polyethylene resins such as LDPE and LLDPE is improved, and the heat shrinkability in the TD direction is improved. Therefore, it is preferable. The density of the cycloolefin homopolymer is preferably about 0.95 to 1.05 g / cm ³ , and the MFR measured at 190 ° C. and 21.18 N is preferably about 0.05 to 4.0 g / 10 minutes.

  Examples of commercially available cycloolefin homopolymers include ZEONOR (trade name) manufactured by Nippon Zeon Co., Ltd., Arton (trade name) manufactured by JSR Corporation, and the like.

  The said cyclic olefin polymer can be used individually or in mixture of 2 or more types.

  When the heat-shrinkable film of the present invention is a single layer, the content of the cyclic olefin polymer is preferably 5 to 50% by weight and more preferably 10 to 30% by weight in 100% by weight of the resin component. Further, when the heat shrinkable film of the present invention is a multilayer as will be described later, any one of the layers contains a cyclic olefin polymer, and the resin component in 100% by weight of the layer containing the cyclic olefin polymer. The content of the cyclic olefin polymer is preferably 5 to 50% by weight, more preferably 10 to 30% by weight. By setting the content of the cyclic olefin polymer in the entire heat-shrinkable film within the above range, the heat-shrinkable film easily exhibits excellent heat-shrinkability and tearability.

  An ionomer is a resinous polymer in which part or all of an olefin polymer is neutralized with metal ions. Examples of the olefin polymer include olefin-unsaturated carboxylic acid copolymers and modified products of olefin polymers.

  Examples of the olefin forming the olefin-unsaturated carboxylic acid copolymer include ethylene and propylene. That is, specific examples of the olefin-unsaturated carboxylic acid copolymer include an ethylene-unsaturated carboxylic acid copolymer and a propylene-unsaturated carboxylic acid copolymer.

  As the unsaturated carboxylic acid constituting the olefin-unsaturated carboxylic acid copolymer, acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleate, A monoethyl maleate etc. can be illustrated. Among these, acrylic acid or methacrylic acid is preferable. Moreover, as said unsaturated carboxylic acid, unsaturated carboxylic acid ester may be used and the saponification thing of the said unsaturated carboxylic acid ester may be used.

  The olefin-unsaturated carboxylic acid copolymer is a copolymer having an unsaturated carboxylic acid content of preferably 1 to 25% by mass, more preferably 3 to 23% by mass, and still more preferably 4 to 20% by mass. Yes, it may be not only a binary copolymer of an olefin and an unsaturated carboxylic acid but also a multi-component copolymer in which other monomers are optionally copolymerized. When the content of the unsaturated carboxylic acid is within the above range, the heat shrinkable film A can exhibit more sufficient tearability, and an increase in hygroscopicity can be suppressed and excellent moldability can be exhibited. .

  Other monomers that may be optionally copolymerized include vinyl acetate, vinyl esters such as vinyl propionate, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, and n-acrylate. Examples include butyl, isooctyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, dimethyl maleate, diethyl maleate, and the like, carbon monoxide, sulfur dioxide, etc. be able to. These other monomers may be copolymerized within a range of, for example, 0 to 30% by weight, preferably 0 to 20% by weight. Such other monomers are preferably not contained, and even if it is contained, it is preferably copolymerized in an amount of about 15% by mass or less.

  Examples of the modified product of the olefin polymer include a modified product obtained by reacting an olefin polymer such as polyethylene or polypropylene with a carboxylic acid or a carboxylic anhydride to add a carboxyl group or a carboxylic anhydride group. .

  As the ionomer, the olefin-unsaturated carboxylic acid copolymer and the modified olefin polymer are 10 to 100 mol%, preferably 10 to 80 mol% of the carboxyl group, carboxylic acid ester group and carboxylic anhydride group. Those neutralized with metal ions can be suitably used. When the degree of neutralization of the carboxyl group, the carboxylic acid ester group, and the carboxylic anhydride group is within the above range, a decrease in tearability of the heat-shrinkable film A can be suppressed. Here, examples of the metal ions include alkali metals such as lithium, sodium and potassium, alkaline earth metals such as magnesium and calcium, and ions such as zinc. Among them, lithium, sodium, potassium, magnesium or zinc is preferable. In particular, it is more preferable to use an ionomer having sodium as an ion source in that the heat-shrinkable film A is excellent in tearability.

  As the ionomer, for example, those described in International Publication No. 2010/024286 and JP-A-6-192512 can be used.

  The ionomer MFR is preferably 0.1 to 4.0 g / 10 min, and preferably 0.5 to 2.0 g / 10 min in terms of excellent moldability and film physical properties in the production process. More preferred. When the heat-shrinkable film is a single layer, the content of ionomer is preferably 10 to 50% by weight and more preferably 15 to 40% by weight in 100% by weight of the resin component. In addition, when the heat shrinkable film of the present invention is a multilayer as described later, any layer contains an ionomer, and the content of the ionomer is 10 to 10% by weight in the resin component of 100% by weight of the layer containing the ionomer. 100 weight% is preferable and 15-100 weight% is more preferable. By setting the content of the ionomer in the entire heat shrinkable film within the above range, the heat shrinkable film easily exhibits excellent heat shrinkability and tearability.

  The layer containing the ionomer may contain, in addition to the polyethylene resin, other ionic copolymers that are not neutralized with metal ions in addition to the ionomer. As the other ionic copolymer that is not neutralized with the metal ion, an ethylene-unsaturated carboxylic acid copolymer that is not neutralized with the metal ion used in the preparation of the ionomer can be used. The unsaturated carboxylic acid copolymer may be the same as or different from the ethylene-unsaturated carboxylic acid copolymer used to prepare the ionomer used in the layer containing the ionomer.

  The heat-shrinkable film preferably contains a polyethylene resin as a main component as a resin component other than the “cyclic olefin” and the “ionomer”. In the present invention, “having a polyethylene-based resin as a main component” means 100% by mass of a resin component other than “cyclic olefin and ionomer” contained in the entire heat-shrinkable film (including cases where the heat-shrinkable film is a multilayer). It means that the polyethylene resin is contained in an amount of 60% by mass or more, more preferably 80% by mass or more. In this specification, “resin component” may include “polyethylene resin” and “ionomer”, but “polyethylene resin” and “ionomer” are different components and are distinguished from each other.

  When the heat-shrinkable film A is a single layer, the thickness is preferably 15 to 150 μm, and more preferably 20 to 100 μm. In the case of multiple layers, the total thickness is preferably 15 to 150 μm, more preferably 20 to 100 μm. In the case of a multilayer, for example, the heat-shrinkable film (basic layer) described above has at least one layer in the multilayer, and the thickness of the basic layer is 10% or more of the total thickness of the multilayer heat-shrinkable film. It is preferable.

  The multilayer heat-shrinkable film is not particularly limited as long as it has the above basic layer, for example, a layer structure comprising other layers as inner and outer layers on both sides of the basic layer as an intermediate layer, The structure which equips one surface of the said basic layer with another layer, and the structure which equips the both surfaces of the other resin layer as an intermediate | middle layer with the said basic layer as an inner layer and an outer layer may be sufficient.

  The other layer laminated with the basic layer is not particularly limited, and examples thereof include a layer mainly composed of LDPE, a layer mainly composed of LLDPE, and the like. A layer composed of LDPE, a layer composed of LLDPE, and the like. Preferably used.

  In the multilayer heat-shrinkable film, the thickness of the basic layer is preferably 10% or more of the total thickness of the multilayer heat-shrinkable film. If the thickness of the base layer is less than 10% of the total thickness of the multilayer heat shrinkable film, the heat shrinkability in the TD direction may not be sufficiently exhibited. The thickness of the basic layer is preferably 15% or more, more preferably 20% or more of the total thickness of the multilayer heat-shrinkable film.

  When the heat shrinkage rate of the heat shrinkable film is measured at 130 ° C. for 20 seconds in accordance with JIS Z1709, the heat shrinkage rate in the MD direction is preferably 30% or more, and is 40 to 80%. It is more preferable. The thermal shrinkage rate in the TD direction is preferably 0% or more. By setting the heat shrinkage rates in the MD direction and the TD direction as described above, it is easy to obtain a high binding property and an excellent appearance of the sleeve opening. In addition, 130 degreeC shrinkage | contraction rate in this specification is the value measured by the measuring method based on JISZ1709 (however, temperature conditions were changed into 120 degreeC from 120 degreeC) using silicone oil as a heat-medium liquid.

  The density of the heat-shrinkable film is not particularly limited, and the MFR is preferably 0.1 to 2.0 g / 10 minutes. By having the above-mentioned specific composition and specific MFR, it is more suitable for accumulation packaging (especially sleeve packaging) of contents (packaged items), and has excellent binding force and strength, and has an opening mark portion The contents can be taken out easily by tearing.

  Examples of the contents (packaged items) include can drinks, plastic bottle drinks, paper pack drinks, and the like, and can be packaged in units of 24 cans, 6 bottles, and the like.

  The heat shrink film of this embodiment can be applied to a heat shrink package. The heat-shrinkable package is obtained by wrapping a heat-shrinkable film in the MD direction around the article to be packaged, or sleeve-wrapping it so as to be wrapped in the front-back direction in the MD direction and then heat-shrinking.

  Specifically, the packaged item is roughly wrapped in a sleeve using a sleeve wrapping machine, and then put into a shrink tunnel. The temperature in the shrink tunnel is raised to a temperature higher than the shrinkage temperature of the heat shrink film, and then heated and cooled. By doing so, it may be shrink-wrapped. Thereby, the MD direction side of a heat shrink film forms what is called a sleeve mouth of a heat shrink package.

  The heating temperature can be appropriately set according to the length of the shrink tunnel and the line speed, but is generally 130 to 240 ° C. By setting to such a temperature range, sufficient shrinkage can be obtained, and perforation due to excessively high temperature can be prevented.

  In the heat-shrinkable package, the side edge parallel to the MD direction of the heat-shrinkable film forms the sleeve opening of the heat-shrinkable package, so that the opening mark portion comprising a hole and / or a cut is formed in the TD direction near the sleeve opening. Remain along. Therefore, the binding force of the heat-shrinkable package and the design of the appearance are not impaired, and it is easy to break the film by hooking or tearing a finger on the sleeve opening, and good openability can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to the aspect of these Examples.

(Preparation example)
The following raw materials were prepared as raw materials for preparing the heat-shrinkable film, and a heat-shrinkable film having a multilayer structure was produced by the following procedure.
LDPE (Asahi Kasei Corporation Suntech LD: M2204, density 0.922 g / cm3, MFR 0.4 g / 10 min (190 ° C.))
Cyclic olefin polymer (TOPAS 9506F-500 manufactured by Polyplastics Co., Ltd., density 1.02 g / cm 3, MFR 1.0 g / 10 min (190 ° C.))
Three extruders (extruders for forming the inner and outer layers (inner and outer layers) and the intermediate layer, respectively) are connected to a circular multilayer die having a diameter of 225 mm and a lip gap of 2.5 mm via a connector. A multilayer inflation film forming apparatus was prepared.

  Two types of films (film A and film B) were produced by using LDPE and a cyclic olefin polymer (COC) with the composition shown in Table 1. Specifically, LDPE and a cyclic olefin polymer (COC) are mixed with the composition shown in Table 1, supplied to each of the extruders, melted and kneaded at 190 ° C., and then the molten resin is mixed with the circular die. Further, it was discharged (co-extruded) under the condition of a die temperature of 190 ° C. to form a melt film. Each of the obtained tubular films had a thickness of 30 μm, a folding width of 70 cm, and a blow ratio of about 2.0. A heat-shrink film having a width of 40 cm was cut out from each of the film A and the film B and used for packaging evaluation.

  Table 1 also shows the physical property values of the heat-shrinkable films obtained in the examples.

  A heat shrink package was prepared using the heat shrink film, and the openability was evaluated.

(Examples 1-5, Comparative Example 1)
As shown in Table 2, the opening mark part of the form shown in FIGS. 1-5 was formed by providing the said heat shrinkable film with the hole or notch of a predetermined shape (each Example 1-5). Table 2 shows the length (diameter), direction, pitch, number of rows, D, and the length and interval of the opening mark portion of the opening mark portion. For comparison (Comparative Example 1), a heat-shrinkable film without holes or notches was prepared.

  Next, using a heat-shrinkable film provided with an opening mark part and a heat-shrinkable film not provided with an opening mark part, a cubic cardboard box having a side of 15 cm is packaged on a cardboard board having a width of 30 cm and a length of 20 cm. It was placed as a product, and a heat-shrinkable film A having a width of 40 cm was wound in the MD direction to provide a front-rear seal and sleeve-wrapped. And it passed through the shrink tunnel set to 160 degreeC, and the heat shrink package was obtained.

  Next, a hole is made by pushing the opening mark portion in the space region formed between the corrugated paperboard and the cardboard box with a finger (in the heat shrink film of Comparative Example 1, a hole is made by pushing the vicinity of the center portion with a finger), and the film Was pinched with a finger, and it was torn in a tape shape in the TD direction and opened.

Openability was evaluated according to the following criteria.
○: The sleeve was torn into a tape shape and could be easily opened.
X: The jammed film was cut halfway and could not be opened.

  Table 2 shows the evaluation results of the unsealing properties.

A heat shrink film 11 margin area 12 unsealing mark part 17 side edge 2a notch 2b hole 20 display part a MD direction b TD direction

Claims (9)

A heat shrink film having an MD direction and a TD direction,
An opening mark formed by a hole and / or a notch is provided,
The Elmendorf tear strength in the TD direction measured in a state without the opening mark portion is 1 N or less,
The opening mark portion is formed by arranging a plurality of holes and / or notches along the MD direction,
The said opening mark part is a heat-shrink film currently formed inside the both ends along the MD direction of the said heat-shrink film.   The heat shrink film according to claim 1, wherein the plurality of holes and / or cuts are formed in at least two rows along the MD direction.   The heat-shrinkable film according to claim 1 or 2, wherein a length in the TD direction of the opening mark portion is 5 to 20 mm. The side ends have side edges along the MD direction,
A blank area set with a length exceeding at least 30 mm from each of the side edges toward the TD direction is provided,
The heat-shrinkable film according to any one of claims 1 to 3, wherein the unsealing mark part is provided with the margin area therebetween. A plurality of the opening mark portions are provided,
The heat-shrinkable film according to any one of claims 1 to 4, wherein each of the unsealing mark portions is arranged along the MD direction with a predetermined interval therebetween.   The heat-shrinkable film according to any one of claims 1 to 5, wherein the opening mark portion has a display portion that guides the opening in the TD direction.   The heat-shrinkable film according to any one of claims 1 to 6, wherein the heat-shrinkable film is formed of a resin containing a polyolefin-based resin containing a cyclic olefin and / or an ionomer.   The heat-shrinkable film according to claim 7, wherein the polyolefin resin includes a polyethylene resin.   The heat-shrink package using the heat-shrink film of any one of Claims 1-8.