JP2845682B2 - Easy tearing film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily tearable film which can be easily torn and a method for producing the same.
It can be used as a base film for packaging bags of industrial products and the like.

[0002]

BACKGROUND ART In recent years, films such as linear low-density polyethylene (L-LDPE) have been frequently used as seal base material (sealant) films for packaging bags of foods, medicines and the like. However, this L-LDPE film is safe because of its excellent sealing strength, but has a large tear resistance, so that it cannot be cut straight along the cut when used and has a problem in opening. Thus, various proposals have conventionally been made for imparting easy tearability and straight-line cutability to the film.

For example, (a) a laminate film having a uniaxially stretched film as an intermediate layer (Japanese Patent Publication No. 58-3)
No. 8320, Japanese Patent Publication No. 55-31725), (b) a structure in which fine scratches are made on the surface of the front base film to facilitate opening,
(c) There is a configuration in which an opening tape is attached to the opening portion of the film.

[0004]

In the structure according to the above (a), the number of intermediate layers is increased by one, and the material cost and the processing cost for laminating are increased. Further, although a uniaxially stretched film is interposed in the intermediate layer, the uniaxially stretched film does not contribute much in strength. In the configuration according to the above (b), the linear cutability is governed by the characteristics of the base material, even if the front base material film is finely scratched and easily opened. In addition, since the surface is damaged even if it is fine, there is a concern about strength.

In the configuration according to the above (c), the cost is increased due to the opening tape, and the productivity is deteriorated. Accordingly, an object of the present invention is to provide an easily tearable film having excellent tearability and straight-line cutability and having sufficient impact strength, and a method for producing the same.

[0006]

SUMMARY OF THE INVENTION The present invention provides a
An easily tearable film used to tear straight
Te, Nylon 6 (Ny6) 40 to 85 parts by weight of meta-xylylene adipamide (MXD6) 15 to 60 parts by weight (however, Ny6
+ MXD6 = 100 parts by weight) and a second layer made of saponified ethylene-vinyl acetate copolymer (EVOH), and a layer ratio between the first layer and the second layer. 2: 1 to 1: 2 is extruded from a multilayer die as, the
Direction during biaxial stretching (moving direction of film)
And TD direction (width direction of the film) are both 2.8 times or more and have a linear cut property, and the tear strength is 8.9 kg / cm or less in any of the MD direction and the TD direction. .

The content ratio of Ny6 and MXD6 in the first layer is 40 to 85 parts by weight of Ny6 and 15 to 60 parts by weight of MXD6 (however, Ny6 + MXD6 = 100 parts by weight). 50 to 80 parts by weight, MXD6 20 to
50 parts by weight. When the MXD6 is less than 15 parts by weight, the tearability and the straight-cutting property become poor. On the other hand, if the content of MXD6 is more than 60 parts by weight, the impact strength is greatly reduced, and the practicality is poor. The MXD6
Is shown in the following chemical formula 1.

[0008]

Embedded image

By including a layer of EVOH,
Gas barrier properties can also be imparted to the easily tearable film. The ethylene content in EVOH in the second layer is:
For example, it is 25 to 45 mol%, preferably 29 to 38 mol%. If the ethylene content is less than 25 mol%, molding becomes difficult, and if it is more than 45 mol%, the barrier performance decreases. In the layer ratio between the first layer and the second layer, the first
When the thickness of the layer is smaller than １ ／ of the thickness of the second layer, the tearability is reduced.

The layer structure in the easily tearable film is arbitrary as long as it has the first layer and the second layer. For example, as shown in FIG. 1, a three-layer structure in which the upper and lower sides of a second layer 31 are sandwiched between first layers 32, and as shown in FIG. 2, the first layer 31 and the second layer 32 Two-layer structure,
As shown in FIG. 3, a third layer (for example, Ny6) 33 is further formed above and below a three-layer structure in which the upper and lower sides of the second layer 31 are sandwiched by the first layer 32.
, And a three-layer structure in which the first layer 32 is sandwiched above and below the second layer 31 as shown in FIG. The thickness of the film including these layers is arbitrary, and is, for example, 8 to 50 μm.

Next, according to the present invention, tearing is performed in a straight line by hand.
The method for producing an easily tearable film used in the above method comprises 40 to 85 parts by weight of nylon 6 (Ny6) and 15 to 60 parts by weight of metaxylylene adipamide (MXD6) (however, Ny6 + MXD6
= 100 parts by weight) and a second layer made of ethylene-vinyl alcohol copolymer (EVOH), wherein the layer ratio of the first layer to the second layer is 2: 1 to 1: 1. 1: 2
After being melt-extruded from a multilayer die, the cooled raw film is simultaneously stretched at a draw ratio of 2.8 times or more in both the MD direction (moving direction of the film) and the TD direction (width direction of the film).
Biaxial stretching to give straight cut, MD direction and TD
The tear strength is 8.9 kg / cm or less in any of the directions.

The raw film is stretched 2.8 times or more in both the MD and TD directions, and preferably 3.0 times or more. When the stretching ratio is smaller than 2.8 times, the tearability and the straight-cutting property are inferior. In addition, the impact strength is reduced, causing a problem in practicality. The stretching is preferably performed by simultaneous biaxial stretching by a tubular method.

The easily tearable film according to the present invention includes:
Necessary additives can be appropriately added. Examples of such additives include an antiblocking agent (such as an inorganic filler), a water repellent (such as ethylene bisstearate), and a lubricant (such as calcium stearate).

[0014]

EXAMPLE 1 A mixture of nylon 6 (Ny6) and metaxylylene adipamide (MXD6) at a ratio of 60 parts by weight and 40 parts by weight, respectively, was melted at 270 ° C. in an extruder (diameter 40 mm). After kneading, the saponified ethylene-vinyl acetate copolymer (E
VOH) in an extruder (diameter 30 mm) at 220 ° C., and then melted by a 90 mm diameter multilayer circular die.
It was extruded as a three-layer film of y6 + MXD6 / EVOH / Ny6 + MXD6 (layer ratio is 2: 1: 2), and then quenched with water to produce a cylindrical raw film. This film corresponds to the three-layer structure shown in FIG.

The Ny6 used was Nylon 6 manufactured by Ube Industries, Ltd. (UBE nylon 1023 FD (trade name), relative viscosity η _r = 3.6), and the MXD6 used was Mitsubishi Gas Chemical ( Metaxylylene adipamide [MX Nylon 6007 (trade name), relative viscosity η]
_r = 2.7]. The EVOH used is a saponified ethylene-vinyl acetate copolymer [Eval F (trade name): ethylene content 32 mol%] manufactured by Kuraray Co., Ltd.

Next, as shown in FIG. 5, after this raw film 11 is inserted between a pair of nip rolls 12, the raw film 11 is heated by a heater 13 while pressurizing gas thereinto, and an air ring 14 The air 15 was blown further to expand the bubble 16 and the pair was taken up by a pair of nip rolls 17 on the downstream side, thereby performing simultaneous biaxial stretching in the MD and TD directions by the tubular method. The magnification for this stretching is MD
It was 3.0 times in both the TD and TD directions. Next, the stretched film 18 was placed in a tenter-type heat treatment furnace, and heat-set at 210 ° C. to obtain an easily tearable film 18 according to the present example.

Next, the tear strength and impact strength (film impact) of the obtained easily tearable film 18 are described.
Was measured, and the tearability and straight-line cutability were evaluated. The results are shown in Tables 1 and 2 below. The measurement of the tear strength was performed by measuring the Elmendorf tear strength (kg / cm 2) in the stretching direction of the film according to JIS-Z1702.

The impact strength was measured using a film impact tester manufactured by Toyo Seiki Co., Ltd., and a semi-circular pendulum (1/2 inch in diameter, weight 30 kg-cm) was attached to a fixed ring-shaped film. ) And measuring the impact strength required for punching the film. If the impact strength is 4500kgcm / cm or more, ○, 4500kgcm / c
x was evaluated as less than m. This impact strength is 4500kgcm
If it is less than / cm, the performance as a surface substrate will gradually decrease, and its practicality as a liquid packaging substrate will be poor.

The above-mentioned tearability is evaluated as follows. For the element E tear strength value E, E ≦ 7 kg / cm: ○, 7 kg / cm <E <9
kg / cm 2 was evaluated as Δ, and E ≧ 9 kg / cm 2 as ×. E is 9
When it is more than kg / cm, the easiness of tearing decreases significantly,
In particular, the straight-line cutability drops sharply.

The straight-line cut property was evaluated as follows. That is, as shown in FIG. 6, the 20cm width of the film 18 nicked 21 at predetermined intervals W _s example 2cm intervals, after tearing the film 18 along these cuts 21, the film piece 18A of the other end 22 measuring the width W _e, the deviation α between the original distance W _s determined as follows. α = _{[(W s -W e) / W} s ] × 100

This measurement was carried out on ten film pieces 18A, and those having an average value α (%) of less than ± 10% were evaluated as ◎
(Very good linear cutability), ± 10% ≦ α ≦ ± 30% ○ (Good linear cutability), x (%) exceeding ± 30% × (Poor linear cutability) ). If α (%) exceeds ± 30%, it becomes difficult to cut the film 18 straight. In the comprehensive evaluation column of Table 1, ◎ indicates very good, は indicates good, and × indicates bad.

Examples 2 to 16 In the above Example 1, the mixing ratio of Ny6 and MXD6 was
The tearable films 18 according to Examples 2 to 16 were obtained by the same manufacturing process as in Example 1 except that the ethylene content, the layer composition ratio, and the stretching ratio of EVOH were changed as shown in Table 1. In addition,
The EVOH used was a saponified ethylene-vinyl acetate copolymer manufactured by Kuraray Co., Ltd. [EVAL F (trade name): ethylene content: 32 mol%, EVAL L: 29 mol%, EVAL H: 38 mol% , EVAL E: 45 mol%].

With respect to the film 18 according to each of the examples, various characteristics were measured and evaluated in the same manner as in the first example. The results are shown in Tables 1 and 2. In the table, numerical values of the first and third layers in the column of raw material composition indicate parts by weight, and numerical values of the second layer indicate ethylene content (mol%). Further, as described below, when the gas barrier property of the film 18 was measured, the oxygen permeability (cc / m ² 24Hr) was 0.79 in Example 4: and 0.70 in Example 10;
48, Example 12: 0.31, and Example 13: 2.06. The oxygen permeability was measured using a Mocon oxygen permeation tester, 23
The measurement was performed under the conditions of ° C and 0% relative humidity.

Comparative Examples 1 to 14 In the above Example 1, the raw material composition, the layer composition ratio and the stretching ratio of each of the three layers were changed as shown in Table 3, and
The films according to Comparative Examples 1 to 17 were obtained by the same manufacturing steps as in Example 1. Comparative Example 7 is a single film of EVOH, Comparative Example 8 is a single film of stretched nylon, and Comparative Example 9 is MXD.
6 is a single film. For the film according to each comparative example, measurement and evaluation of various characteristics were performed in the same manner as in Example 1. Tables 3 and 4 show the results. When the gas barrier properties of the film were measured, the oxygen permeability (cc / m ²⁾
24Hr) were Comparative Example 1: 1.56, Comparative Example 7: 0.30, and Comparative Example 8: 61.0.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

Discussion of Examples and Comparative Examples From Tables 1 and 2, the easily tearable film 18 according to the present example
a first layer containing 40 to 85 parts by weight of y6 and 15 to 60 parts by weight of MXD6, a second layer of EVOH,
And the layer ratio of the second layer to the second layer is 2: 1 to 1: 2, and the stretching ratio of the film during biaxial stretching is in the MD direction and in the T direction.
Since it is 2.8 times or more in both directions D, it can be seen that the tear strength is 8.9 kg / cm or less and excellent in tearability, and that the straight cut property is good or very good. In addition, each of them has a high impact strength of 5000 kg · cm / cm or more.

On the other hand, from Tables 3 and 4, the films according to Comparative Examples 1 to 4 have three layers and a second layer made of EVOH, but the film containing both Ny6 and MXD6 Since there is no first layer according to the present invention, even if the impact strength is sufficient, the tear strength is high, and the tearability and the linear cut property are poor.

The films according to Comparative Examples 5 and 6 had a layer containing Ny6 and MXD6, but had a high tear strength, easy tearability and a straight line cut because the component ratio was not within the range according to the present invention. Poor sex. When the component ratio of MXD6 is too large (Comparative Example 6), the impact strength is also inferior. Since the films according to Comparative Examples 7 to 9 are single films and are not a combination of the first layer and the second layer according to the present invention, any one of the tear strength, the linear cut property, and the impact strength is required. Inferior in one or more.

Even if the films according to Comparative Examples 10 to 12 have the first layer and the second layer according to the present invention, since the stretch ratio is not more than the range according to the present invention, the tear strength and the ease of tearing can be improved. Tear,
It is inferior in any one or more of the linear cut property and the impact strength. Even though the films according to Comparative Examples 13 and 14 have the first layer and the second layer according to the present invention, since the layer ratio is out of the range according to the present invention, the film has tear strength and tearability. , Inferior in any one or more of straight cut property and impact strength.

[0033]

According to the easily tearable film and the method for producing the same of the present invention, a film having excellent tearability and straight-cutting properties and having sufficient impact strength can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one configuration of an easily tearable film according to the present invention.

FIG. 2 is a sectional view showing another configuration of the easily tearable film according to the present invention.

FIG. 3 is a sectional view showing another configuration of the easily tearable film according to the present invention.

FIG. 4 is a cross-sectional view showing another configuration of the easily tearable film according to the present invention.

FIG. 5 is a schematic view of a biaxial stretching device used in the method for producing an easily tearable film according to an example of the present invention.

FIG. 6 is a diagram illustrating a method for evaluating straight-line cut properties.

[Explanation of symbols]

 11 Raw film 12,17 Nip roll 16 Bubble 18 Tear-resistant film 31 Second layer 32 First layer 33 Third layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B29K 77:00 B29L 9:00 (56) References JP-A-53-83892 (JP, A) JP-A-6-55710 (JP, A) JP-A-4-169231 (JP, A)

Claims (2)

(57) [Claims] An easy tear used for tearing in a straight line by hand
A first layer containing 40 to 85 parts by weight of nylon 6 (Ny6) and 15 to 60 parts by weight of meta-xylylene adipamide (MXD6) (however, Ny6 + MXD6 = 100 parts by weight); A second layer comprising a saponified vinyl acetate copolymer (EVOH), extruded from a multilayer die with a layer ratio of the first layer to the second layer of 2: 1 to 1: 2, MD direction (moving direction of film) and TD direction (width direction of film) during simultaneous biaxial stretching
Has a linear cut property by setting both magnifications to 2.8 times or more.
An easily tearable film having a tear strength of 8.9 kg / cm or less in any of the D direction and the TD direction. 2. An easy tear used for tearing in a straight line by hand.
A method for producing a functional film, comprising: nylon 6 (Ny6)
40-85 parts by weight and meta-xylylene adipamide (MXD6)
15-60 parts by weight (however, Ny6 + MXD6 = 100 parts by weight)
And a second layer made of ethylene-vinyl alcohol copolymer (EVOH), wherein the layer ratio of the first layer to the second layer is 2: 1 to 1: 2. After being melt-extruded from a die, the cooled raw film is simultaneously biaxially stretched at a draw ratio of 2.8 times or more in both the MD direction (moving direction of the film) and the TD direction (width direction of the film) to have a linear cut property. And a tear strength of 8.9 kg / cm or less in any of the MD direction and the TD direction.