JP4306904B2 - Multilayer film excellent in linear cut property and package using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer film having at least a sealant layer and a base material layer, and a package obtained from the film. Specifically, the present invention relates to a multilayer film excellent in linear cut property and sealability, and a package formed from the film.
[0002]
[Prior art]
In recent years, as one of the performances required for a package, there is a straight-cut property (property to tear straight in one direction). FIG. 4 is a perspective view showing the opened state of the conventional package A ′. When the package A ′ is torn from the unsealed side 41, the film forming the package has a straight-cut property. Therefore, the cut edges 5a and 5b of the front film 1a and the back film 1b are not aligned and are displaced. If the cut ends 5a and 5b are displaced, it becomes difficult to cut the cut portion 6 at the side portion 42 on the side opposite to the unopening side. If the cutting part 6 is forcibly torn, an extra force is applied to the side part 42 on the side opposite to the unopening side, and the contents may pop out at the moment of tearing.
[0003]
Therefore, in recent years, a method for imparting a linear cut property to a film forming a package has been studied. The most common method for imparting linear cut properties is a method in which a base material layer and a sealant layer are separately formed, and only the base material layer is stretched and oriented, and then these are bonded together. However, in order to achieve sufficient seal strength, the film forming the package usually has a sealant layer that is thicker than the base material layer. Therefore, even if only the base material layer was stretched and oriented, satisfactory linear cut properties could not be obtained. In addition, when the sealant layer has a property that it is difficult to tear, even when the base material layer is cut at the time of opening, the sealant layer is not cut properly, and may appear in a state of extending to the cut end.
[0004]
Then, the method of extending | stretching and orientating a sealant layer similarly to a base material layer was examined. However, for example, when the sealant layer is formed of linear low-density polyethylene, high-density polyethylene, or the like, the sealant layer easily breaks during the stretching process, and even if it does not break, it is difficult to be stretched uniformly and has a thickness. Was uneven. Further, when the sealant layer is formed of polypropylene, the sealant layer is stretched relatively stably. At this time, the crystallization proceeds, the melting point rises, and a temperature range in which a good seal can be performed. It was narrow.
[0005]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to provide a multilayer film excellent in linear cut property and excellent in sealability, and a package using the film.
[0006]
[Means for Solving the Problems]
According to the present invention, as a means for solving the above-mentioned problems, a multi-layer film having at least a sealant layer and a base material layer, wherein the sealant layer is a dicarboxylic acid unit (A) mainly comprising a terephthalic acid unit (a). And a polyester obtained by copolymerizing a glycol unit (B) mainly composed of an ethylene glycol unit (b-1) and a 1,4-cyclohexanedimethanol unit (b-2), and the sealant layer is oriented. A multilayer film characterized in that is provided,
Furthermore, the multilayer film is provided, wherein the sealant layer is manufactured by a T-die extrusion method,
Furthermore, the multilayer film is characterized in that the sealant layer is stretched by a tenter stretching method,
Furthermore, the packaging body which consists of the said multilayer film and the orientation direction of a sealant layer and the opening direction of a packaging body overlap is provided.
[0007]
As a result of intensive studies on a resin that can be oriented very easily and that is excellent in sealability even when oriented, the present inventors have found that a dicarboxylic acid unit (A) mainly composed of a terephthalic acid unit (a) , An amorphous polyester obtained by copolymerizing a glycol unit (B) mainly composed of an ethylene glycol unit (b-1) and a 1,4-cyclohexanedimethanol unit (b-2) (hereinafter referred to as amorphous (Referred to as PET). Furthermore, in order to obtain a multilayer film excellent in linear cut property and sealability using the resin, the present inventors have found that the resin is preferably stretched and oriented and used as a sealant layer. Furthermore, since amorphous PET is very easy to be oriented, it can be oriented simply by forming a film by a T-die extrusion method, and can provide a linear cut property, and a tenter stretching method is used. Furthermore, when it extended | stretched to a uniaxial direction, it discovered that linear cut property could be provided more correctly, and came to this invention.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view (A) (B) showing a multilayer film 1 of the present invention. The multilayer film 1 of the present invention has at least a sealant layer 2 and a base material layer 3. Each of the sealant layer 2 and the base material layer 3 may be a single layer or a multilayer. In the multilayer film 1 shown in FIG. 1A, the sealant layer 2 is a single layer, the base material layer 3 is composed of two layers of a layer 31 and a layer 32, and the multilayer film 1 shown in FIG. Is composed of two layers of the innermost layer 21 and the other layer 22, and the base material layer 3 is also composed of two layers.
When the sealant layer 2 is a multilayer as shown in FIG. 1B, the innermost layer 21 must be made of amorphous PET in consideration of the sealing ability of the multilayer film 1. However, when the innermost layer 21 has a sufficient thickness, specifically, when it is 10 μm or more, there is no problem even if the other layer 22 is formed from a resin other than amorphous PET. Absent.
[0009]
In the multilayer film 1 of the present invention, at least the sealant layer 2 (when the sealant layer 2 is a multilayer film, at least the innermost layer 21 of the sealant layer 2) is formed from amorphous PET. , Dicarboxylic acid unit (A) mainly composed of terephthalic acid unit (a), glycol unit (B) mainly composed of ethylene glycol unit (b-1) and 1,4-cyclohexanedimethanol unit (b-2) It is formed from the polyester obtained by copolymerizing.
In addition to terephthalic acid (a), the dicarboxylic acid unit (A) includes isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, as long as the effects of the present invention are not impaired. , 5-naphthalenedicarboxylic acid, methyl terephthalic acid, 4,4′-biphenyldicarboxylic acid, 2,2′-biphenyldicarboxylic acid, 1,2′-bis (4-carboxyphenoxy) -ethane, succinic acid, adipic acid, Other dicarboxylic acid units such as suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, octadecanedicarboxylic acid, dimer acid, and 1,4-cyclohexanedicarboxylic acid may be included.
[0010]
The glycol unit (B) mainly comprises an ethylene glycol unit (b-1) and a 1,4-cyclohexane dimethanol unit (b-2), and the blending ratio thereof is not particularly limited. ) :( b-2) = 60 to 90 mol%: preferably in the range of 40 to 10 mol%, particularly preferably in the range of 65 to 80 mol%: 35 to 20 mol%. When the ethylene glycol (b-1) component is less than 60 mol%, the tensile strength and the flexural modulus are lowered, the sheet becomes weak, and conversely when it exceeds 90 mol%, the crystallinity of the resulting polyester is increased. , Stretchability and sealability deteriorate.
In addition to these, the glycol unit (B) includes propylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1 as long as the effects of the present invention are not impaired. , 10-decanediol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 2,2-bis (2′-hydroxyethoxyphenyl) propane and other glycol units may be included.
[0011]
Furthermore, the amorphous PET is within the range that does not change the properties of the resin, for example, reinforcing agent, filler, or antioxidant, ultraviolet absorber, heat stabilizer, antistatic agent, lubricant, antiblocking agent, dye, pigment, etc. These various additives can also be included.
[0012]
Next, the base material layer 3 will be described. The resin for forming the base material layer 3 is not particularly limited, and may be appropriately selected and used according to the contents. For example, when the contents are foods that do not like moisture such as candy and rice crackers, it is preferable to use an olefin resin such as polyethylene or polypropylene having excellent water vapor barrier properties for at least one layer of the base material layer. Is a food that dislikes oxygen like a snack, it is preferable to use an ethylene-vinyl alcohol copolymer, an aluminum foil or the like for at least one layer of the base material layer.
Moreover, since the multilayer film 1 of this invention is provided with the linear cut property by the sealant layer 2, there is no problem even if the base material layer 3 is not oriented. However, when the base material layer 3 is formed of a resin having a high tear strength, it is preferable that the base material layer 3 is oriented in the opening direction by stretching or the like.
[0013]
Next, although the manufacturing method of the multilayer film of this invention is demonstrated based on FIG. 2 (A)-(C), the manufacturing method of this invention is not limited to this.
FIG. 2A shows a method in which a sealant layer 2 and a base material layer 3 are formed at a time using an inflation coextrusion molding method, a T-die coextrusion molding method, or the like, and then a multilayer film is stretched. When the multilayer film is formed by the T-die coextrusion molding method, since the sealant layer 2 is already oriented, the stretching step (β) may be omitted. Moreover, also when forming the multilayer film 1 by the inflation coextrusion method, the multilayer film 1 can be oriented by adjusting the blow ratio and the winding speed. As long as the multilayer film 1 is sufficiently oriented in at least one of the longitudinal direction and the transverse direction, the stretching step (β) may be omitted as in the case of using the T-die coextrusion molding method. However, when it is desired to give a more accurate straight cut property, it is desirable to stretch the multilayer film 1 as shown in FIG. The stretching method is not particularly limited as long as it can be accurately stretched in one direction, but the tenter stretching method is given as a preferred example in the present invention.
[0014]
Moreover, as shown in FIGS. 2B and 2C, the sealant layer 2 and the base material layer 3 may be separately formed and then bonded to form the multilayer film 1. When the stretching process is performed, it may be performed before the sealant layer 2 and the base material layer 3 are bonded together as shown in FIG. 2 (B), and the sealant layer 2 and the base material layer as shown in FIG. 2 (C). 3 may be performed after pasting together. Moreover, you may perform bonding of the sealant layer 2 and the base material layer 3 via adhesive resin etc. as needed.
[0015]
Next, although the method to manufacture the package A using the multilayer film 1 of this invention is demonstrated based on FIG. 3, it is not limited to this. First, the multilayer film 1 shown in FIG. 3A is folded in two in parallel with the orientation direction X (B), or two multilayer films 1 are prepared and overlapped so that the orientation directions X overlap (B ′). Prepare a stack of 1's. However, at this time, the multilayer film 1 is overlaid so that the sealant layer 2 is inside.
Next, a seal 7 is performed at regular intervals (C), cut as necessary, and a pre-packed body a that is closed except one side is formed (D). Finally, if the contents 8 are filled from the unsealed side and the filling port is sealed 7, the package A of the present invention is completed (E). At this time, an opening notch 9 may be provided on the side perpendicular to the alignment direction X as necessary.
[0016]
In addition, although it is the intensity | strength of the seal | sticker 7 in the package A, a required value changes with the weight of the content 8, etc. FIG. If the contents are relatively light seaweed or delicacy, the seal strength should be 5N / 15mm or more. Further, even when the package A performs individual packaging of confectionery, there is no particular problem if the seal strength is 5 N / 15 cm or more.
When the contents become heavy and it is necessary to increase the sealing strength, the thickness of the layer made of amorphous PET of the sealant layer 2 may be increased. Even if the thickness of the amorphous PET is increased to some extent, if the layer is oriented, the straight-cut property is not lowered so much that it is better than the polyolefin-based sealant layer.
[0017]
【Example】
Hereinafter, the present invention will be described with reference to examples. However, the performance of the obtained multilayer film is evaluated by conducting the following test.
[Linear cut property test]
Using the multilayer films obtained in Examples 1 and 2 and Comparative Example 1, a package having a length of 200 mm and a width of 140 mm is produced. In addition, a package is created so that the orientation direction is the horizontal direction, and the package is opened in the horizontal direction.
At this time, a straight line is drawn in the orientation direction from the opening position, and the distance (the length of L in FIG. 4) of the portion where the cut end is most deviated from the straight line is measured and set as the maximum deviation. Moreover, the distance (the length of M in FIG. 4) of the portion where the cut edges of the front film and the back film are most shifted is measured and set as the front / back shift.
If the multilayer film has a good linear cut property, the multilayer films on the front and back sides are cut in a straight line, so that the maximum deviation and the front and back deviation are both close to zero.
[0019]
[Example 1] Using terephthalic acid as the dicarboxylic acid component and using as a glycol component a mixture of ethylene glycol and 1,4-cyclohexanedimethanol in a molar ratio of 70:30, and copolymerizing them. The resulting amorphous polyester is formed into a 120 μm film by a T-die extrusion method. Further, the film is stretched 6 times in the transverse direction by the tenter stretching method and oriented. The obtained film is used as a sealant layer. Next, polypropylene is formed into a film by a T-die extrusion method, and the obtained film is stretched by a tenter stretching method to form a film having a thickness of 20 μm. Let the obtained film be a base material layer. The sealant layer and the substrate film are bonded together via a polyether-based urethane adhesive so that the orientation directions are overlapped to obtain a multilayer film .
[0020]
[Example 2] Using the same resin as in Example 1, a film having a thickness of 30 μm was formed by an inflation extrusion molding method, and this was used as a sealant layer. However, at the time of inflation extrusion molding, the blow ratio is 2.5 times and the film is stretched in the transverse direction, the winding speed is 20 m / mim, the machine direction is stretched 5 times, and the resin is oriented in both the transverse and longitudinal directions. Film formation is performed. The obtained film is used as a sealant layer. Further, the same polypropylene film as in Example 1 is used as a base material layer, and the base material layer and the sealant layer are bonded together via a polyether-based urethane adhesive so that the orientation directions are overlapped to obtain a multilayer film .
[0021]
[Comparative Example 1] Polypropylene was formed into a 30 μm film by a T-die extrusion method, and a polypropylene film oriented in the machine direction was formed, which was used as a sealant layer. Further, in the same manner as in Examples 1 and 2, a polypropylene film was formed by a T-die extrusion method and further stretched by a tenter stretching method, and a film having a thickness of 20 μm was used as a base material layer. The sealant layer and the base material layer are bonded together so that the orientation directions are overlapped to obtain a multilayer film .
[0023]
When a stretched and oriented amorphous PET film is used as a sealant layer, the linear cut property of the obtained film is improved. In addition, although the sealant layer of Example 1 was greatly stretched in one direction by a tenter stretching method, it was very excellent in linear cut property. In addition, the sealant layer of Example 2 is stretched in two directions in the vertical and horizontal directions by an inflation extrusion molding method, and is also oriented in the opening direction. Moreover, the multilayer film of Example 2 has good sealing strength and is suitable when the contents are heavy. In addition, the sealant layer of Comparative Example 1 was formed by a T-die extrusion method and oriented in the machine direction, but sufficient linear cutability was not obtained.
[0024]
【The invention's effect】
In the multilayer film of the present invention, the sealant layer has a dicarboxylic acid unit (A) mainly composed of a terephthalic acid unit (a), an ethylene glycol unit (b-1), and a 1,4-cyclohexanedimethanol unit (b-2). It is molded from an amorphous polyester obtained by copolymerizing a glycol unit (B) mainly comprising the above, and an excellent seal can be performed even at a relatively low temperature. Moreover, since the sealant layer is oriented in the opening direction, the multilayer film of the present invention is excellent in linear cut property.
[0025]
Furthermore, since the resin forming the sealant layer of the multilayer film of the present invention is easily oriented, it can be oriented in one direction in a very simple and stable manner using a T-die extrusion molding method or a tenter stretching method.
Furthermore, the packaging body obtained from the multilayer film of the present invention can be opened linearly, so that it takes no effort to open the packaging body, and excessive force is not applied to the packaging body and the contents do not pop out.
Furthermore, the amorphous polyester is excellent in the property of barriering the scent, and even if the contents are foods that value the scent such as tea leaves and coffee beans, the scent is not escaped.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view (A) (B) showing an example of a multilayer film of the present invention.
FIGS. 2A to 2C are explanatory views (A) to (C) showing a method for producing a multilayer film of the present invention. FIGS.
FIGS. 3A to 3E are explanatory views (A) to (E) showing a method for manufacturing a package according to the present invention. FIGS.
FIG. 4 is a perspective view showing an opened state of a conventional package.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Multilayer film 1a 'Front side film 1b' Back side film 2 Sealant layer 21 Innermost layer 22 Other layers 3 Base material layer 41 Opening side side part 42 Anti-opening side side part 5a 'Front side film cut 5b' Back side film cut 6 Cutting Part 7 Seal 8 Contents 9 Notch A Package a Pre-package L Maximum deviation M Front / back deviation

Claims (3)

A multilayer film having at least a stretched sealant layer 2 and a stretched base material layer 3, wherein the sealant layer 2 includes a dicarboxylic acid unit (A) mainly composed of a terephthalic acid unit (a), and ethylene glycol. excellent linear cutting properties, characterized in that comprising a unit (b-1) and 1,4-cyclohexanedimethanol units (b-2) a polyester obtained by copolymerizing glycol units (B) composed mainly of Multilayer film 1. The multilayer film 1 according to claim 1, wherein the sealant layer 2 is uniaxially stretched by a tenter stretching method.  A package A comprising the multilayer film 1 according to claim 1.

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