JP2012211339A - Easily tearable shrink film, easily tearable laminated film, easily tearable bag and production method of easily tearable shrink film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily tearable shrink film having excellent straight cutting property and causing no intralayer exfoliation in an oriented film layer, to provide an easily tearable laminated film and an easily tearable bag using the same, and to provide a production method of the easily tearable shrink film.SOLUTION: The easily tearable shrink film comprises 60-85 pts.mass nylon 6 (hereinafter expressed as Ny6) and 15-40 pts.mass methaxylylene adipamide (hereinafter expressed as MXD6) (the sum of both being 100 pts.mass) as raw materials, wherein the raw materials include a virgin material comprising 60-85 pts.mass Ny6 and 15-40 pts.mass MXD6 and a thermal history product provided by melt-kneading the Ny6 and the MXD6 to render the melting point of the MXD6 233-238°C, the content of the thermal history product is 5-40 mass% based on the total raw materials, and the shrinkage of the easily tearable shrink film is 3-20% when the film is held in 95°C hot water for 30 min.

Description

  The present invention relates to an easily tearable shrink film, an easily tearable laminate film, an easily tearable bag, and a method for producing an easily tearable shrinkable film.

In Japan, helping with the aging society, helping elderly and people with disabilities to live a comfortable social life with young and healthy people, removes barriers (disabilities) in various fields. The concept of “barrier-free” is beginning to attract attention.
On the other hand, films such as linear low-density polyethylene (L-LDPE) are frequently used as a sealing substrate (sealant) film for packaging bags for foods, medicines and the like. However, this L-LDPE film is safe because it has excellent sealing strength, but has a problem that it is difficult to open because it has a high tear resistance and does not cut straight along the cut line during use.
Therefore, in the packaging field, the demand for “barrier-free” has been greatly increased. Specifically, for various food packaging materials and medical packaging materials, there is a further demand for easy opening (easy tearability). It is growing.
Therefore, various proposals have been made for imparting easy tearing properties, particularly straight line cutting properties, to the film constituting the bag.
For example, a laminate film having a uniaxially stretched film as an intermediate layer (Patent Document 1), and nylon 6 (hereinafter also referred to as Ny6) and metaxylylene adipamide (hereinafter also referred to as MXD6) as a surface base film. Examples using a biaxially stretched film made of a blend resin are known (Patent Document 2, Patent Document 3). Furthermore, an example in which shrinkage (shrink) characteristics are provided for packaging ham, sausage and the like is also known (Patent Document 4).

Japanese Patent Publication No.58-38302 Japanese Patent Laid-Open No. 5-220837 Japanese Patent Laid-Open No. 5-200958 JP 11-91052 A

  However, in the structure which concerns on patent document 1, although the uniaxially stretched film is interposed in the intermediate | middle layer and the linear cut property is excellent, this uniaxially stretched film does not contribute much in terms of strength. On the other hand, in the structure which concerns on patent documents 2-4, since the surface base material excellent in the linear cut property was given and it was set as the laminate film, since the outstanding linear cut property can be maintained, it is practical as an easily tearable bag. High value. However, a biaxially stretched film made of a blend resin of Ny6 and MXD6 may cause so-called delamination within the layer of the biaxially stretched film when placed under harsh conditions after forming a laminate film. . When such delamination occurs, the strength of the laminate film becomes unstable, causing a practical problem when a bag is constructed. In particular, in the case of a shrink-wrapping bag that causes shrinkage of the laminate film during boiling or retorting, such delamination in the layer becomes a serious problem.

  Therefore, the object of the present invention is an easily tearable shrinkable film that has excellent linear cut properties and does not cause in-layer peeling in the stretched film layer, an easily tearable laminate film, an easily tearable bag, And it is providing the manufacturing method of an easily tearable shrink film.

The easily tearable shrinkable film of the present invention is an easily tearable shrinkable film containing, as raw materials, 60 to 85 parts by mass of Ny6 and 15 to 40 parts by mass of MXD6 (the total of both being 100 parts by mass). Includes a virgin raw material composed of 60 to 85 parts by mass of Ny6 and 15 to 40 parts by mass of MXD6, and a heat history product obtained by melting and kneading Ny6 and MXD6 to have a melting point of MXD6 of 233 to 238 ° C., The content of the heat history product is 5 to 40% by mass based on the total amount of the raw material, and when the easily tearable shrink film is held in hot water at 95 ° C. for 30 minutes, the shrinkage rate of the film is MD direction. The TD direction is 3 to 20%. This shrinkage rate is preferably 6 to 20%, more preferably 10 to 20%.
Here, the chemical formula of Ny6 is shown in the following chemical formula 1, and the chemical formula of MXD6 is shown in the chemical formula 2 below.

The above-mentioned virgin raw material usually means a raw material that is not a mixed raw material having a history in which Ny6 and MXD6 are mixed and melt-kneaded. For example, even if Ny6 and MXD6 have a history of being melt-kneaded independently (for example, recycled products), they are virgin raw materials when they are not mixed and melt-kneaded. However, from the viewpoint of physical properties when it becomes an easily tearable shrink film, it is preferable to use a virgin raw material with as few times of recycling as possible. Even if Ny6 and MXD6 have a history of mixing and melt-kneading each other, because the kneading is weak, if the melting point of MXD6 is not so low and the temperature exceeds 238 ° C., these Ny6 and MXD6 are still It constitutes a virgin raw material, not a heat history product.
That is, in the present invention, Ny6 and MXD6 constituting the virgin raw material are added to a heat history product, and the three (or two) are melt-kneaded after so-called dry blending to form an easily tearable shrink film.
The heat history product is a blended product of Ny6 and MXD6 and once passed through the extruder. In the present invention, the melting point of MDX6 resin is in the range of 233 to 238 ° C. with a differential scanning calorimeter (DSC). Means the one held in

Here, peeling within a layer means a phenomenon that causes peeling in an easily tearable shrinkable film (nylon layer) when the tearable shrinkable film is laminated with an appropriate sealant film and used under severe conditions. The mechanism of delamination is not always clear, but it is considered that Ny6 and MXD6 are oriented in layers in the easily tearable shrink film, and delamination occurs at the interface.
When such delamination occurs, the strength of the laminate film becomes unstable, and problems such as broken bags may occur when a bag is formed. In particular, the problem is great at the time of shrinkage in boil processing and retort processing. Such in-layer peeling can be reproduced by, for example, a test for measuring the laminate strength (peel strength) of the laminate film.

According to the easily tearable shrinkable film of the present invention, the blending ratio of Ny6 and MXD6 in the virgin raw material is 60 to 85 parts by mass for Ny6 and 15 to 40 parts by mass for MXD6, so that it has excellent linear cut properties. And since the heat history product formed by melt-kneading Ny6 and MXD6 is contained in the entire raw material, it is peeled in the layer even if an easily tearable shrink film is used under severe conditions. It is hard to cause.
The melting point of MXD6 in the heat history product is 233 to 238 ° C, preferably 235 to 237 ° C. When the melting point of MXD6 in the heat history product is less than 233 ° C., the linear cut property and impact resistance of the easily tearable shrink film are lowered. Further, when the melting point of MXD6 in the heat history product is 238 ° C. or more, the effect of preventing in-layer peeling is reduced.
In addition, when the temperature and pressure at the time of kneading are high in the process of manufacturing a heat history product, the melting point of MXD6 in the heat history product is further lowered. Here, the melting point of MXD6 in the heat history product refers to a melting point measured in a state before being melt-kneaded with the virgin raw material.

When this easily tearable shrinkable film is used as a surface base material of a laminate bag, biaxially stretched is preferable from the viewpoint of improving impact resistance. In addition, biaxial stretching is preferably performed by simultaneous biaxial stretching by a tubular method from the viewpoint of the balance of strength in the vertical and horizontal directions.
Moreover, in terms of easy tearing, it is preferable that the tear strength in at least one direction in the plane of the easily tearable shrink film is 70 N / cm or less, but when the film is biaxially stretched, In particular, the tear strength is more preferably 70 N / cm or less in at least one of the MD direction and the TD direction.

In this invention, it is preferable that the mixture ratio of Ny6 and MXD6 in the said heat history goods is Ny6: MXD6 = 60-85 mass parts: 15-40 mass parts.
According to the present invention, since the blending ratio of Ny6 and MXD6 in the heat history product is Ny6: MXD6 = 60 to 85 parts by mass: 15 to 40 parts by mass, linear cut performance, impact resistance, and anti-layer peeling effect Thus, an easily tearable shrink film can be obtained.

The easily tearable laminate film of the present invention is characterized in that the above easily tearable shrink film is formed as at least one of a plurality of layers.
According to the easily tearable laminate film of the present invention, since the above easily tearable shrink film is formed as at least one of a plurality of layers, the laminate film is a shrink film excellent in linear cut property and impact resistance. .

The easily tearable bag of the present invention is characterized by using the above easily tearable laminate film.
According to the easily tearable bag of the present invention, since it is constructed using the above easily tearable laminate film, it is excellent in unsealing property (straight cut property) and in-layer peeling does not occur in the nylon film layer. In addition, it is an easily tearable bag that is stable in strength and practical. Moreover, even if it is used under severe shrinkage conditions such as boiling and retort, it is difficult for the nylon layer to peel in the layer.

  The production method of the easily tearable shrinkable film of the present invention includes a raw film containing Ny6 and MXD6 as raw materials in both the MD direction (film moving direction) and the TD direction (film width direction) of 2.8 times or more. A method for producing an easily tearable shrinkable film that is stretched at a draw ratio, wherein the raw material is a virgin raw material composed of 60 to 85 parts by mass of Ny6 and 15 to 40 parts by mass of MXD6 (both are 100 parts by mass in total). On the other hand, Ny6 and MXD6 are melt-kneaded to contain a heat history product in which the melting point of MXD6 is 233 to 238 ° C. based on the total amount of the raw material, and the heat treatment temperature after stretching is 150 to 205 ° C. It is characterized by doing.

According to the manufacturing method of the easily tearable shrinkable film of the present invention, since Ny6 and MXD6 are included as raw materials and stretched at a predetermined stretching ratio, the manufactured film is excellent in linear cut property, and a laminate film is used. Even in the case of the configuration, the good linear cut property can be maintained. Moreover, since it is biaxial stretching to MD direction and TD direction, it is excellent also in impact resistance. Furthermore, since the raw material contains a predetermined heat history product, the nylon layer does not peel in the layer even when the laminate film (bag) is handled under severe conditions.
In addition, the draw ratio in the MD direction and / or TD direction is both 2.8 times or more, preferably 3.0 times or more. When the draw ratio is less than 2.8 times, the linear cut property becomes inferior. Even biaxial stretching causes a problem in practicality due to a decrease in impact resistance. In addition, it is preferable to perform extending | stretching by simultaneous biaxial stretching by a tubular method at the point of the intensity | strength balance of MD direction and TD direction.
And since the heat treatment temperature after stretching is set to 150 to 205 ° C. to form an easily tearable shrink film, an easily tearable laminate film and an easily tearable bag are produced from the easily tearable shrinkable film, and shrinkage due to boiling, retort, etc. When the treatment is performed, it has an appropriate shrinkage rate and is also characterized in that the nylon layer is hardly peeled off within the layer.

1 is a schematic view of a biaxial stretching apparatus according to an embodiment of the present invention. Sectional drawing of the easily tearable laminated film (2 layer structure) in the said embodiment. Sectional drawing of the easily tearable laminated film (3 layer structure) in the said embodiment. Sectional drawing of the easily tearable laminated film (3 layer structure) in the said embodiment. The front view which shows the easily tearable bag in the said embodiment. The figure which shows the evaluation method of the linear cut property which concerns on the Example of this invention.

[Easily tearable shrink film]
As described above, the easily tearable shrink film of the present invention satisfies the conditions such as the blending amount of Ny6 and MXD6 in the raw material, and when the film is held in hot water at 95 ° C. for 30 minutes, The production method is not particularly limited as long as the shrinkage rate is 3 to 20% in both the MD direction and the TD direction. This shrinkage rate is preferably 6 to 20%, more preferably 10 to 20%.
Hereinafter, the best mode for carrying out the present invention will be described in detail.

In the easily tearable film of the present invention, the blending ratio of Ny6 and MXD6 in the virgin raw material is 60 to 85 parts by mass of Ny6 and 15 to 40 of MXD6 from the viewpoint of the linear cut property and impact resistance of the film after film formation. It must be part by mass. When the MXD6 in the virgin raw material is less than 15 parts by mass, the linear cut property becomes inferior. Moreover, when there is more MXD6 than 40 mass parts, impact resistance (impact strength) will fall significantly and it will become impractical.
Ny6 and MXD6 constituting the virgin raw material are preferably used by dry blending pellets.

  The raw material must contain a heat history product obtained by melting and kneading Ny6 and MXD6. The melting point of MXD6 in the heat history product is 233 to 238 ° C, preferably 235 to 237 ° C. When the melting point of MXD6 in the heat history product is less than 233 ° C., the linear cut property and impact strength of the easily tearable shrink film are lowered. In addition, when the melting point of MXD6 in the heat history product is 238 ° C. or higher, the effect of preventing in-layer peeling is reduced.

Furthermore, it is necessary that the heat history product formed by melting and kneading Ny6 and MXD6 is contained in an amount of 5 to 40% by mass, preferably 10 to 35% by mass, based on the entire raw material. If the heat history product is less than 5% by mass, peeling within the layer tends to occur when the tearable shrink film is used as a laminate film and then used under severe conditions. Moreover, when a heat history product exceeds 40 mass%, the linear cut property and impact strength of an easily tearable shrink film will fall.
In addition, it is preferable that the mixture ratio of Ny6 and MXD6 in a heat history goods is Ny6: MXD6 = 60-85 mass parts: 15-40 mass parts.
Ny6 is 60-85 parts by mass and MXD6 is 15-40 parts by mass in the heat history product. It can be a film.
When the blending ratio of MXD6 in the heat history product is less than 15 parts by mass (the blending ratio of Ny6 is more than 85 parts by mass), the effect of preventing in-layer peeling is reduced when an easily tearable shrink film is formed. When the mixing ratio of MXD6 in the heat history product exceeds 40 parts by mass (the mixing ratio of Ny6 is less than 60 parts by mass), the linear cut property and impact strength of the easily tearable shrinkable film are lowered.

  The heat history product may be a product obtained by recycling the easily tearable shrinkable film obtained according to the present embodiment. In order to dry blend the heat history product with the Ny6 pellet and the MXD6 pellet well, it is desirable to process the shape of the heat history product into a pellet. For example, the easily tearable shrinkable film obtained according to the present embodiment may be cut and compressed into such a shape.

  This easily tearable shrink film is preferably biaxially stretched when used as a front substrate of a laminate bag. Biaxial stretching is preferably performed by simultaneous biaxial stretching by a tubular method from the viewpoint of the balance of strength in the vertical and horizontal directions. Moreover, it is preferable that the tear strength is 70 N / cm or less in any of the MD direction and the TD direction from the viewpoint of improving the linear cut property.

  In addition, a required additive can be suitably added to an easily tearable shrink film. Examples of such additives include anti-blocking agents (such as inorganic fillers), water repellents (such as ethylene bis stearates), and lubricants (such as calcium stearate).

According to the easily tearable shrinkable film of the present invention described above, the blending ratio of Ny6 and MXD6 in the virgin raw material is 60 to 85 parts by mass for Ny6 and 15 to 40 parts by mass for MXD6, in which Ny6 and MXD6 are melted. Since the melting point of MXD6 in this heat history product is 233 to 238 ° C. and the content of the heat history product is 5 to 40% by mass based on the total amount of raw materials, Excellent in strength and impact strength.
Further, when the easily tearable shrink film is held in hot water at 95 ° C. for 30 minutes, the shrinkage rate of the film is 3 to 20% in both MD and TD directions, preferably 6 to 20%, more preferably. 10 to 20%, an appropriate shrinkage characteristic can be exhibited when an easily tearable laminate film described later and further an easily tearable bag are used. If the shrinkage rate is less than 3%, it is not preferable that the easily tearable bag is shrunk when it is shrunk by boil, retort or the like. For example, even if heat treatment is performed after the unheated sausage raw material is charged and the material is shrunk, the contents and the easily tearable bag are not sufficiently adhered, and the appearance of the bag is deteriorated. On the contrary, if the shrinkage rate exceeds 20%, excessive shrinkage may occur, which may cause deformation of the easily tearable bag.
And even if it uses such an easily tearable shrink film under severe conditions, such as a boil and a retort, a nylon layer does not raise | generate peeling in a layer easily.

  The easily tearable shrinkable film of the present invention can be produced using, for example, a tubular biaxial stretching apparatus 1 as shown in FIG. For example, after melt-extruding a mixture of Ny6 pellets, MXD6 pellets and a heat history product that has been dry blended, the cooled original film is biaxially stretched at a magnification of 2.8 times or more in both the MD and TD directions and stretched. It can be produced by setting the subsequent heat treatment temperature to 150 to 205 ° C, preferably 160 to 195 ° C. By setting the heat treatment temperature after stretching in such a range, the shrinkage rate of the easily tearable shrinkable film when held in hot water at 95 ° C. for 30 minutes is easily controlled to 3 to 20%. be able to.

[Easily tearable laminate film]
The easily tearable laminate film of the present invention includes an easily tearable shrink film as at least one layer, and may have any number of layers such as two layers and three layers. 2 to 4 show the easily tearable laminate films 100, 200, and 300 according to the present embodiment. Here, for example, as shown in FIG. 2, a two-layer structure in which the first layer is an easily tearable shrink film 18 and the second layer is various sealant films 19, and as shown in FIG. The material film 20, a three-layer structure in which the second layer is an easily tearable shrink film 18, and the third layer is various sealant films 19, as shown in FIG. 4, the first layer is an easily tearable shrink film 18, the second layer It is good also as a 3 layer structure which used various base film 20 and the 3rd layer as various sealant films 19.

  Examples of the material of the base film 20 include PET (polyethylene terephthalate), EVOH (saponified ethylene-vinyl acetate copolymer), PVA (polyvinyl alcohol), PP (polypropylene), PVDC (polyvinylidene chloride), HDPE (high Biaxial or uniaxially stretched films such as density polyethylene) and PS (polystyrene) or unstretched films can be used. In addition to such a resin film, a metal film such as an aluminum foil may be used.

  As a material of the sealant film 19, L-LDPE (linear low density polyethylene), LDPE (low density polyethylene), HDPE (high density polyethylene), EVA (ethylene-vinyl acetate copolymer), PB (polybutene-1) ), CPP (unstretched polypropylene), ionomer, PMMA (polymethylmethacrylate), and the like, and mixtures thereof. Examples of the laminating method of the easily tearable laminate film include an extrusion laminate, a hot melt laminate, a dry laminate, and a wet laminate.

  According to the present embodiment, the easily tearable laminate films 100, 200, and 300 have the above-described easily tearable shrink film 18 formed as at least one of a plurality of layers. Property) and impact strength. In addition, even when used under severe conditions, the nylon layer does not peel off within the layer. That is, if a bag is manufactured using this easily tearable laminate film 100, 200, 300, it can be used as an easily tearable bag 400 (FIG. 5) utilizing the characteristics. Specifically, even after the bag is shrunk with a boil or a retort after filling the contents, the nylon layer hardly peels in the layer.

Therefore, the easily tearable laminate film and easily tearable bag of the present invention can be suitably used for shrink packaging of hams and sausages.
For example, as a conventional sausage packaging, a type using a vinylidene casing and an aluminum caulking is generally used, but it is very difficult to open. On the other hand, if the easily tearable bag of the present invention is used, the user can easily open (straight cut) simply by providing a V notch or an I notch at one end of the bag. Further, since the easily tearable bag of the present invention does not require the use of metal, it is possible to use a metal detector, and since heat sealing is possible, the content is excellent in sealing performance. And it is very preferable to fill an unheated sausage raw material in the bag and perform a retort treatment because the bag can be shrunk and shaped simultaneously with the heat curing and sterilization of the raw material. In order to improve the adhesion between the contents (sausage, etc.) and the easily tearable bag, the seal surface (the inner surface side of the bag) of the sealant film constituting the easily tearable bag is subjected to corona treatment. Is also effective.

Although the best configuration for carrying out the present invention has been disclosed in the above description, the present invention is not limited to this. That is, the present invention has been described primarily with reference to specific embodiments, but with respect to the above-described embodiments without departing from the scope of the technical idea and object of the present invention, the material, quantity, and other details. In this configuration, those skilled in the art can make various modifications.
Accordingly, the description of the materials, layer structures, and the like disclosed above is exemplary for easy understanding of the present invention, and does not limit the present invention. Descriptions with names excluding some or all of the limitations are included in the present invention.

For example, in the present embodiment, a biaxially stretched film is manufactured as the easily tearable shrink film, but a uniaxially stretched film may be used. For example, a uniaxially stretched film oriented in the TD direction in the easily tearable bag of FIG. 5 may be used as the front substrate film. This is suitable when the straight cut is particularly important.
Moreover, in this embodiment, although the tubular system was employ | adopted as a biaxial stretching method, a tenter system may be used. Furthermore, the stretching method may be simultaneous biaxial stretching or sequential biaxial stretching.

Next, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to these examples.
[Example 1]
(Manufacture of tearable shrink film)
Ny6 pellets and MXD6 pellets were mixed at a ratio of 70 parts by weight and 30 parts by weight, respectively, and heat history products that had already been melt-mixed and pelletized at this blending ratio (with a melting point of MXD6 of 236 ° C) ) Was blended in an amount of 15% by mass based on the total amount of raw materials. After this dry blend product was melt-kneaded at 270 ° C. in an extruder, the melt was extruded as a cylindrical film from a die and then rapidly cooled with water to produce a raw film.
Here, the melting point of MXD6 was measured by increasing the temperature from 50 ° C. to 280 ° C. at a temperature increase rate of 10 ° C./min using a differential scanning calorimeter (DSC) manufactured by PerkinElmer. In all cases, the value in the first run was taken as the melting point.

What was used as Ny6 is Ube Industries, Ltd. nylon 6 [UBE nylon 1023FD (trade name), relative viscosity ηr = 3.6]. What was used as MXD6 is
It is metaxylylene adipamide [MX nylon 6007 (trade name), relative viscosity ηr = 2.7] manufactured by Mitsubishi Gas Chemical Co., Ltd.
In addition, the mixture ratio of Ny6 and MXD6 was 70 mass parts and 30 mass parts, respectively, and what was extruded at 270 degreeC using 40phiEX and a single screw (made by Yamaguchi Seisakusho) was used as a heat history article.

Next, as shown in FIG. 1, the raw film 11 is inserted between a pair of nip rolls 12 and then heated by a heater 13 while a gas is being pressed into the film 11. Was blown into the bubble 16 and taken up by a pair of downstream nip rolls 17 to perform simultaneous biaxial stretching in the MD direction and the TD direction by the tubular method. The magnification during this stretching was 3.0 times in the MD direction and 3.2 times in the TD direction.
Next, this stretched film is put into a tenter type heat treatment furnace (not shown) and subjected to a heat treatment (heat setting) at 160 ° C., and an easily tearable shrink film 18 according to this example (hereinafter also referred to as a stretched film 18). Got. Moreover, the shrinkage rate when this stretched film was held in hot water at 95 ° C. for 30 minutes was 19% in both the MD direction and the TD direction.

(Manufacture of easy tear laminate film)
Next, the stretched film 18 (thickness 15 μm) was used as a surface base film, an L-LDPE film (Unilux LS-711C (trade name), manufactured by Idemitsu Unitech Co., Ltd., thickness 50 μm), and a sealant film. Was dry laminated to obtain an easily tearable laminate film (hereinafter also referred to as a laminate film) 100 as shown in FIG. In addition, as an adhesive for dry lamination, a blended product of Takelac A-615 / Takenate A-65 (mixing ratio 16/1) manufactured by Mitsui Takeda Chemical was used. The laminated film after dry lamination was aged at 40 ° C. for 3 days.

[Evaluation method]
(Stretch formability)
The stability of bubbles at the time of forming the stretched film 18 was evaluated as stretch moldability. Specifically, the case where the bubble was stable was evaluated as A, and the case where the bubble was unstable and unstable was evaluated as C. In addition, even if there was shaking of the bubble at first, B was the one that could stabilize the bubble by fine adjustment.

(Shrinkage factor)
After preparing a stretched film 18 with a 100 mm marked line along the MD and TD directions and leaving this film in 95 ° C. hot water for 30 minutes, the condition was adjusted to 23 ° C. and humidity 50% RH. The shrinkage in the MD and TD directions was measured. The shrinkage, _{L 0} the initial length, the length after shrinkage as _L, was calculated by the equation of _{(L 0 -L) / L 0} × 100 (%).

(Impact resistance)
The stretched film 18 was measured for impact strength as follows.
Using a film impact tester manufactured by Toyo Seiki Co., Ltd., impact strength required for punching the film 18 by striking a semicircular pendulum (1/2 inch in diameter) on the fixed ring-shaped film 18 It was performed by measuring. An impact strength of 45,000 J / m or more was evaluated as A, and less than 45,000 J / m was evaluated as C. When this impact strength is less than 45,000 J / m, the performance as a surface base material is lowered, and the practicality as a base material for shrink wrapping becomes poor.

(Linear cut property)
As a measure of easy tearability of the stretched film 18, linear cutability was measured as follows.
As shown in FIG. 6, cuts 21 are made in a 20 cm wide film 18 at predetermined intervals Ws (for example, 2 cm intervals), the film 18 is torn along these cuts 21, and then the width of the other end 22 of the film piece 18A. We are measured, and a deviation α from the original interval Ws is obtained by the following equation.
α = [| Ws−We | / Ws] × 100
This measurement is performed on 10 pieces of film 18A, and the average value α (%) is less than ± 10% when A ⁺ (the linear cut property is very good), ± 10% ≦ α ≦ ± 30. % Was evaluated as A (good linear cut performance), and α (%) exceeded ± 30% as C (bad linear cut performance). If α (%) exceeds ± 30%, it is difficult to cut the film 18 straight.

(Tear strength)
About the stretched film 18, tear strength was measured as follows.
Based on the Elmendorf tear strength test (JIS K 7128), the tear strength in the MD direction and the TD direction of the stretched film 18 was measured. And, the tear strength of 70 N / cm or less was evaluated as A, and the one exceeding 70 N / cm (high tear resistance) was evaluated as C. The tear strength is preferably 70 N / cm or less from the viewpoint of improving the linear cut property. When the tear strength exceeds 70 N / cm, the tear resistance increases and the linear cut property decreases, and the practical performance as an easily tearable packaging substrate becomes poor.

(In-layer peeling)
A strip-shaped test piece having a width of 15 mm was cut out from the above-described laminate film 100, and the end portion thereof was subjected to interfacial peeling by several cm by hand to separate it into a front substrate film (stretched film 18) and a sealant film. Thereafter, each film piece was set in a tensile tester (Instron universal tester 1123 type), and a peel test of the laminate portion was performed at a speed of 300 mm / min (90 ° peel).
In the middle of the peel test, if peeling inside the surface substrate film occurs, the peel strength sharply decreases. Therefore, it can be determined whether or not such peeling has occurred, depending on whether or not such behavior has occurred. For example, at the start of the peel test, if the peel strength is about 7 N / 15 mm width, but suddenly decreases to about 1 to 2 N / 15 mm width during the peel test, it can be judged that the in-layer peel has occurred. .
And the thing which did not show the behavior of peeling in a layer inside a surface base film was evaluated as A, and the thing which showed the behavior of peeling in a layer was evaluated as C.

(Product appearance)
A three-sided ham and sausage casing bag is prepared using the laminate film 100, the contents are filled, and then boiled with hot water (95 ° C., 30 minutes) to evaluate the adhesion between the bag and the contents. did. The case where the adhesion between the bag and the contents was good was designated as A, and the case where the adhesion between the bag and the contents was poor or warped was designated as C.

(Comprehensive evaluation)
A comprehensive evaluation was given as A when all of the above eight items, namely stretch moldability, shrinkage rate, impact resistance (impact strength), linear cut property, tear strength, delamination within the product, and product appearance, were A or higher. If there is at least one C among the above 8 items, the overall evaluation is C.

[Examples 2 to 8, Comparative Examples 1 to 7]
In Example 1 above, the mixing amount of Ny6 pellets, MXD6 pellets and heat history product, and the melting point of MXD6 in the heat history product were changed, and the heat setting conditions after stretching were changed, and the same production as in Example 1 Film formation was performed according to the process. The evaluation test was also performed in the same manner as in Example 1. Table 1 shows the production conditions and evaluation results of the examples, and Table 2 shows the comparative examples.

[Evaluation results]
As shown in Table 1, the stretched film 18 according to the present example is obtained when the blending amounts of Ny6 and MXD6 in the raw material satisfy predetermined conditions and the film is held in hot water at 95 ° C. for 30 minutes. Since the shrinkage ratio of the film is in the range of 3 to 20% in both the MD direction and the TD direction, any of stretch moldability, impact strength, straightness cut property, tear strength, and in-layer peeling prevention effect can be obtained. Excellent. Furthermore, since the hot water shrinkage was appropriate, the adhesion between the laminate film 10 and the contents was good, and the product appearance of the bag was good.

  On the other hand, as shown in Table 2, since the comparative examples do not satisfy the above-described conditions, there are problems in the physical properties of the stretched film 18. Specifically, since Comparative Example 1 did not contain a heat history product as a raw material, the film 18 (nylon layer) had undergone in-layer peeling. Moreover, since the content of the heat history goods is as large as 45 mass%, the comparative example 2 was inferior to impact strength, linear cut property, and tear strength. In Comparative Example 3, since the shrinkage rate of the film (95 ° C., 30 minutes) is very small at 2% in both the MD direction and the TD direction, the shrinkage during boiling of the casing three-sided bag made from the laminate film 10 is not sufficient. The product appearance of the bag was poor, and the adhesion to the contents was insufficient. In Comparative Example 4, since the melting point of MXD6 in the heat history product was as low as 232 ° C., the linear cutting property was inferior. In Comparative Example 5, since the content of the heat history product is small, the film 18 (nylon layer) caused in-layer peeling as in Comparative Example 1. In Comparative Example 6, since the melting point of the heat history product was as low as 210 ° C., the impact strength, the linear cut property, and the tear strength were both inferior. The stretch moldability was also poor. In Comparative Example 7, since the content of Ny6 was too large, the tear resistance was high (high tear strength) and the linear cut property was poor.

  INDUSTRIAL APPLICATION While this invention is excellent in easy tearability (straight cut property) and impact resistance (impact strength), it can be utilized as an easily tearable bag for shrink wrapping in which the nylon layer does not cause in-layer peeling.

DESCRIPTION OF SYMBOLS 1 ... Biaxial stretching apparatus 11 ... Original fabric film 12 ... Nip roll 13 ... Heater 14 ... Air ring 15 ... Air 16 ... Bubble 17 ... Nip roll 18 ... Easy tear film 19 ... Sealant film 20 ... Base film 100,200, 300 ... Easy tear laminate film 400 ... Easy tear bag

Claims (6)

Easy tear containing 60 to 85 parts by mass of nylon 6 (hereinafter also referred to as Ny6) and 15 to 40 parts by mass of metaxylylene adipamide (hereinafter also referred to as MXD6) (the total of both being 100 parts by mass) A shrinkable film,
The raw materials are 60 to 85 parts by mass of Ny6 and 15 to 40 parts by mass of MXD6,
Ny6 and MXD6 are melt kneaded, and MXD6 has a melting history of 233 to 238 ° C.
The content of the heat history product is 5 to 40% by mass based on the total amount of the raw material,
When the easily tearable shrink film is kept in hot water at 95 ° C. for 30 minutes, the shrinkage rate of the film is 3 to 20% in both the MD direction and the TD direction. Shrink film. In the easily tearable shrinkable film according to claim 1,
An easily tearable shrinkable film having a tear strength in at least one direction in the plane of the easily tearable shrinkable film of 70 N / cm or less. In the easily tearable shrinkable film according to claim 1 or 2,
An easily tearable shrinkable film, wherein the blending ratio of Ny6 and MXD6 in the heat history product is Ny6: MXD6 = 60 to 85 parts by mass: 15 to 40 parts by mass.   The easily tearable shrinkable film according to any one of claims 1 to 3, wherein the easily tearable shrinkable film is formed as at least one of a plurality of layers.   An easily tearable bag using the easily tearable laminate film according to claim 4. A process for producing an easily tearable shrinkable film, in which a raw film containing Ny6 and MXD6 as raw materials is stretched at a stretch ratio of 2.8 times or more in both the MD direction (film movement direction) and the TD direction (film width direction). Because
Ny6 and MXD6 are melt-kneaded with respect to the virgin raw material which 60 to 85 mass parts of Ny6 and MXD6 consist of 15 to 40 mass parts (the total of both is 100 mass parts), and the melting | fusing point of MXD6 is 233- Containing 5 to 40% by mass of the heat history product at 238 ° C. based on the total amount of the raw materials,
A method for producing an easily tearable shrinkable film, wherein a heat treatment temperature after stretching is 150 to 205 ° C.

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