JPH0699492A - Easy tearing film and production thereof - Google Patents

Abstract

PURPOSE:To obtain an easy tearing film excellent in easy tearing properties and linear cutting properties and also having sufficient impact strength. CONSTITUTION:First 1 third layers 31-33 each containing nylon 6 (Ny 6) and m-xylyleneadipamide (MXD 6) are formed so that the Ny 6 content of the first and third layers 31, 33 is set to 60-95 pts.wt. and the MXD 6 content thereof is set to 5-40 pts.wt. and the Gy 6 content of the second layer 32 is set to 40-85 pts.wt. and the MXD 6 content thereof is set to 15-60 pts.wt. The ratio of the first-third layers 31-33 is set to 1:8:1-4:2:4 and the ratio of the first (or third) layer and the second layer is set to 1:8-2:1 and the ratio of the first and third layers is set to 1:8-2:1 and, in this state, the first - third layers are extruded from a multilayered die in a molten state to form a raw film which is, in turn, stretched by 2.8 times or more in both of the MD and TD directions thereof to obtain an easy tearing film.

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, for example, foods, medicines,
It can be used as a base film for packaging bags for industrial products and the like.

[0002]

BACKGROUND ART In recent years, films such as linear low-density polyethylene (L-LDPE) have been widely used as a seal base material (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 it has a large tear resistance, so it cannot be cut straight along the cut line during use, and there was a problem during opening. Therefore, various proposals have heretofore been made to impart easy tearability and linear cuttability to a film.

For example, (a) a laminated film having a uniaxially stretched film as an intermediate layer (Japanese Patent Publication No. 58-3).
No. 8320 gazette, Japanese Patent Publication No. 55-31725 gazette), (b) A structure that makes it easy to open by making fine scratches on the surface of the front substrate film,
(c) There is a configuration in which an unsealing tape is attached to the unsealing portion of the film.

[0004]

In the structure according to (a) described above, the number of intermediate layers is increased by one, and the material cost and the machining allowance for laminating become high. Further, although a uniaxially stretched film is interposed in the intermediate layer, this uniaxially stretched film does not contribute much in terms of strength. In the configuration according to the above (b), the linear cuttability is governed by the characteristics of the base material even if the front base material film is finely scratched and easily opened. Further, even if it is fine, it scratches the surface, so there is concern about strength.

In the structure according to (c), the unsealing tape causes a high cost and a poor productivity. Therefore, an object of the present invention is to provide an easily tearable film which has excellent easy tearability and linear cuttability and also has sufficient impact strength, and a method for producing the same.

[0006]

The easily tearable film according to the present invention has first to third layers containing nylon 6 (Ny6) and metaxylylene adipamide (MXD6), and The Ny6 content of the first and third layers is 60 to 95 parts by weight, the MXD6 content is 5 to 40 parts by weight, and the Ny of the second layer is
6 content is 40 to 85 parts by weight and MXD6 content is 15 to 60 parts by weight (provided that each layer has Ny6 + MXD6 = 100 parts by weight and the MXD6 content of the second layer is MXD6 of the first and third layers). Content ratio), the layer ratio of the first to third layers is 1: 8: 1 to 4: 2: 4, and the layer ratio of the first (or third) and second layers is 1: 8 to 2: 1, and the layer ratio of the first and third layers is 1: 2 to 2: 1.

Ny6 and MX in the first and third layers
The content ratio of D6 is 60 to 95 parts by weight of Ny6 and 5 to 40 parts by weight of MXD6, preferably 70 to 90 parts by weight of Ny6 and 10 to 30 parts by weight of MXD6. If the amount of Ny6 is less than 60 parts by weight, the pinhole resistance is lowered.
Further, when Ny6 is more than 95 parts by weight, the linear cut property is deteriorated.

The content ratio of Ny6 and MXD6 in the second layer is 40 to 85 parts by weight of Ny6 and 15 to 60 parts by weight of MXD6, preferably 50 to 80 parts by weight of Ny6 and MX.
D6 is 20 to 50 parts by weight. When the amount of MXD6 is less than 15 parts by weight, the easy tearing property and the linear cutting property are deteriorated. Further, when the amount of MXD6 is more than 60 parts by weight, the impact strength is significantly reduced and the practicality becomes poor. The chemical formula of MXD6 is shown in Chemical Formula 1 below.

[0009]

[Chemical 1]

The layer ratio of the first to third layers is 1: 8: 1 to
The ratio is 4: 2: 4, preferably 15:70:15 to 35:30:
35. The layer ratio of the first (or third) layer to the second layer is 1: 8 to 2: 1 and preferably 15:70 to 35:30. If it is smaller than 1/8, the pinhole resistance is lowered.

The layer constitution in the easily tearable film is from the first to the first.
Any number of layers can be used as long as it has the third layer. For example, as shown in FIG. 1, a three-layer structure in which a first layer 31, a second layer 32 and a third layer 33 are sequentially stacked, and as shown in FIG. 2, a first layer 31 and a second layer 31. , 32 and third layer 33 between the fourth layer
There is a four-layer structure with 34 interposed. This fourth layer 34 is
It is also possible to mix all layers and add a new component (Ny6 or MXD6) to the recycled layer having an intermediate compounding ratio of all layers or this recycled layer. The new component is preferably a compounding amount of Ny6 or MXD6 in the middle of the first and second layers.

Next, in the method for producing an easily tearable film according to the present invention, the first to third layers containing nylon 6 (Ny6) and metaxylylene adipamide (MXD6) are added to the first layer.
And the Ny6 content of the third layer is 60 to 95 parts by weight, the MXD6 content is 5 to 40 parts by weight, and the Ny6 content of the second layer is 40 to 85 parts by weight.
Parts by weight, the content of MXD6 is 15 to 60 parts by weight (however, each layer is Ny6 + MXD6 = 100 parts by weight), and the layer ratio of the first to third layers is 1: 8: 1 to 4: 2: 4 and the first ( Or after melt extrusion from a multi-layer die with the layer ratio of the third layer to the second layer being 1: 8 to 2: 1, and the layer ratio of the first layer to the third layer being 1: 2 to 2: 1. , Cooled original film in MD direction (film moving direction) and TD direction (film width direction)
Both are characterized by being drawn at a draw ratio of 2.8 times or more.

The original film is stretched by 2.8 times or more in both MD and TD directions, preferably 3.0 times or more. When the draw ratio is less than 2.8 times, the easy tearing property and the linear cutting property become poor. In addition, the impact strength is lowered, causing a problem in practical use. The stretching is preferably performed by simultaneous biaxial stretching by a tubular method.

The easily tearable film according to the present invention comprises:
Necessary additives can be added appropriately. Examples of such additives include anti-blocking agents (inorganic fillers, etc.), water repellents (ethylene bisstearate, etc.), and lubricants (calcium stearate, etc.).

[0015]

EXAMPLES Example 1 80 parts by weight and 20 parts by weight of nylon 6 (Ny6) and metaxylylene adipamide (MXD6), which are the first layer, respectively.
Ny6, which is the second layer, which is mixed in a ratio of parts by weight.
And MXD6 in a proportion of 40 parts by weight and 60 parts by weight, respectively, and a third layer, Ny6 and MXD6.
80 parts by weight and 20 parts by weight, respectively, were melt-kneaded at 270 ° C. in three extruders (diameter 40 mm), and then the melt was melted through a circular circular die with a diameter of 90 mm to the first position.
Layer / second layer / third layer (layer ratio 1: 2: 1) was extruded as a three-layer film, followed by quenching with water to prepare a cylindrical raw film. In addition, this film is
Corresponds to the three-layer structure shown in.

The Ny6 used was Nylon 6 [UBE Nylon 1023 FD (trade name), relative viscosity η _r = 3.7] manufactured by Ube Industries, and the one used as MXD6 was Mitsubishi Gas Chemical ( Co., Ltd. Metaxylylene adipamide [MX nylon 6007 (trade name), relative viscosity η
_r = 2.7].

Next, as shown in FIG. 3, after the raw film 11 is inserted between a pair of nip rolls 12, it is heated by a heater 13 while gas is being pressed into the nip rolls 12, and an air ring 14 is set at a stretching start point. More air 15 is blown to expand the bubbles 16, and the bubbles 16 are taken up by a pair of downstream nip rolls 17 to perform simultaneous biaxial stretching in the MD and TD directions by the tubular method. Magnification during this stretching is MD
It was 3.0 times in both the direction and the TD direction. Next, the stretched film 18 was placed in a tenter type heat treatment furnace and heat-set at 210 ° C. to obtain a biaxially stretched film 18 according to this example.

Next, regarding the obtained stretched film 18,
Tear strength and impact strength (film impact) were measured, and easy tearability and linear cutability were evaluated. The results are shown in Table 1 below. The tear strength was measured by measuring the Elemendorf tear strength (kg / cm 2) according to JIS-Z1702 in the stretching direction of the film.

The impact strength was measured by using a film impact tester manufactured by Toyo Seiki Co., Ltd., and a semicircular pendulum (diameter: 1/2 inch, weight: 30 kg-cm) was attached to a fixed ring-shaped film. ) Was punched and the impact strength required for punching the film was measured. When the impact strength is 4500 kg ・ cm / cm or more, ○, 4500 kg ・ cm / c
The value less than m was evaluated as x. This impact strength is 4500kg ・ cm
When it is less than / cm, the performance as a surface base material deteriorates and the practicality as a base material for liquid packaging becomes poor.

Regarding the easy tearability, the value E of the Elmendorf tear strength is E = 7 kg / cm, and 7 kg / cm <E <9.
The evaluation was made with kg / cm 3 as Δ and E ≧ 9 kg / cm 2 as ×. E is 9
If it is over kg / cm, the easiness of tearing will decrease significantly,
In particular, the straight line cutting property drops sharply.

The linear cuttability was evaluated as follows. That is, as shown in FIG. 4, cuts 21 are made in the film 18 having a width of 20 cm at a predetermined interval W _s, for example, 2 cm, and the film 18 is torn along these cuts 21 and then the other end 22 of the film piece 18A is cut. The width W _e is measured and the deviation α from the original interval W _s is determined as follows. α = [(W _s −W _e ) / W _s ] × 100

This measurement was carried out on 10 pieces of film 18A, and if the average value α (%) was less than ± 10%,
(Linear cut property is very good), ± 10% ≤ α ≤ ± 30% ○ (Linear cut property is good), α (%) exceeds ± 30% × (Linear cut property is poor ). If α (%) exceeds ± 30%, it becomes difficult to cut the film 18 straight. In the columns of comprehensive evaluation in Tables 2 and 4, ⊚ indicates very good, ∘ indicates good, and x indicates poor.

Examples 2 to 15 The same as Example 1 except that the mixing ratio of Ny6 and MXD6, the layer constitution ratio and the draw ratio in the first to third layers were changed as shown in Table 1. The biaxially stretched film 18 according to Examples 2 to 15 was obtained by the manufacturing process. Regarding the film 18 according to each example, various characteristics were measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Examples 1 to 11 The same as Example 1 except that the mixing ratio of Ny6 and MXD6, the layer constitution ratio and the draw ratio in the first to third layers were changed as shown in Table 3. Biaxially stretched films according to Comparative Examples 1 to 11 were obtained by the manufacturing process. In addition, Comparative Examples 1 to 4 are single-layer films. With respect to the film according to each comparative example, various characteristics were measured and evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

Consideration of Examples and Comparative Examples From Tables 1 and 2, the film 18 according to this example shows that nylon 6 (Ny6) and metaxylylene adipamide (MXD6) were used.
The first to third layers containing Ny6 of the first and third layers.
Content of 60-95 parts by weight, MXD6 content of 5-40 parts by weight, Ny6 content of the second layer of 40-85 parts by weight, MXD6 content of 15 parts by weight.
-60 parts by weight (however, Ny6 + MXD6 = 10 for each layer)
0 parts by weight, and the MXD6 content of the second layer is higher than the MXD6 content of the first and third layers), and the layer ratio of the first to third layers is 1: 8: 1 to 4: 2: 4. A film at the time of biaxial stretching, in which the layer ratio of the first (or third) layer to the second layer is 1: 8 to 2: 1, and the layer ratio of the first to third layer is 1: 2 to 2: 1. It can be seen that, since the stretching ratio of No. 2 is 2.8 times or more in both MD and TD, the tear strength is 7.0 kg / cm or less, the tearability is excellent, and the linear cutting property is good or very good. All of them have high impact strength of 6500 kg · cm / cm or more.

On the other hand, from Tables 3 and 4, since the films according to Comparative Examples 1 and 2 are single-layer films made of Ny6,
High tear strength and poor linear cutability.
The film according to Comparative Example 3 is a single-layer film containing a small amount of MXD6 as small as 10%, and therefore has poor linear cutability. The film according to Comparative Example 4 is a single-layer film made of MXD6, and therefore has poor impact strength.

The films according to Comparative Examples 5 to 7 have the first and third layers, but the content ratios of Ny6 and MXD6 in these layers deviate from the content ratios according to the present invention, and therefore, the linear cut film is used. Inferior in sex. The film according to Comparative Example 8 is
Even if there are first to third layers, Ny of the layers of the first and third layers
Since the content ratio of 6 and MXD6 deviates from the content ratio according to the present invention, and the layer ratio deviates from the layer ratio according to the present invention,
It is inferior in easy tearing and straight line cutting.

The films according to Comparative Examples 9 to 11 are Nos. 1 to 3
The content ratios of Ny6 and MXD6 in the layer No. 1 are included in the content ratio according to the present invention, and the layer ratios of the first to third layers are within the layer ratio according to the present invention. Since the stretching ratio is less than 2.8 times in both MD and TD, it is inferior in any one or more of tear strength, linear cut property and impact strength.

[0033]

EFFECTS OF THE INVENTION According to the easily tearable film and the method for producing the same of the present invention, a film having excellent easy tearability and linear cuttability and also having sufficient impact strength can be obtained.

[Brief description of 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 cross-sectional view showing another structure of the easily tearable film according to the present invention.

FIG. 3 is a schematic view of a biaxial stretching device used in a method for producing an easily tearable film according to an example of the present invention.

FIG. 4 is a diagram showing an evaluation method of linear cuttability.

[Explanation of symbols]

 11 Original film 12,17 Nip roll 16 Bubble 18 Biaxially stretched film 31 First layer 32 Second layer 33 Third layer 34 Fourth layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29L 9:00 4F

Claims (2)

[Claims] 1. Having first to third layers containing nylon 6 (Ny6) and metaxylylene adipamide (MXD6), wherein the Ny6 content of the first and third layers is 60 to 95 parts by weight. , MXD6 content of 5-40 parts by weight, Ny of the second layer
6 content is 40 to 85 parts by weight and MXD6 content is 15 to 60 parts by weight (provided that each layer has Ny6 + MXD6 = 100 parts by weight and the MXD6 content of the second layer is MXD6 of the first and third layers). Content ratio), the layer ratio of the first to third layers is 1: 8: 1 to 4: 2: 4, and the layer ratio of the first (or third) and second layers is 1: 8 to 2: 1,
An easily tearable film, wherein the layer ratio of the first and third layers is 1: 2 to 2: 1. 2. The first to third layers containing nylon 6 (Ny6) and metaxylylene adipamide (MXD6), wherein the Ny6 content of the first and third layers is 60 to 95 parts by weight, MX
The D6 content is 5 to 40 parts by weight, and the Ny6 content of the second layer is
40 to 85 parts by weight and MXD6 content of 15 to 60 parts by weight (provided that each layer has Ny6 + MXD6 = 100 parts by weight and the MXD6 content of the second layer is MXD6 of the first and third layers).
Content ratio), the layer ratio of the first to third layers is 1: 8: 1 to 4: 2: 4, and the layer ratio of the first (or third) and second layers is 1: 8 to 2: 1,
After melt extruding from the multilayer die in a state where the layer ratio of the first and third layers is 1: 2 to 2: 1, the cooled original film is subjected to MD direction (film moving direction) and TD direction (film direction). A method for producing an easily tearable film, characterized in that both are stretched at a draw ratio of 2.8 times or more in the width direction.