JP2617655B2 - 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 it cannot be cut straight along the cut when used, and there is 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]

The easily tearable film according to the present invention contains nylon 66 (Ny66) and an aromatic nylon metaxylylene adipamide (MXD6). 85 parts by weight of the MXD6
15 to 60 parts by weight (however, Ny66 + MXD6 = 100 parts by weight). The chemical formula of MXD6 is shown in Chemical Formula 1 below.

[0007]

Embedded image

The content ratio of Ny66 and MXD6 is as follows:
Ny66 is 40 to 85 parts by weight and MXD6 is 15 to 60 parts by weight (however, Ny66 + MXD6 = 100 parts by weight), preferably 50 to 80 parts by weight of Ny66 and 20 to 50 parts by weight of MXD6. 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. And, by containing Ny66, heat resistance can be imparted to the easily tearable film.

Next, the method for producing an easily tearable film according to the present invention is characterized in that Ny66 is 40 to 85 parts by weight and MXD6 is 15 to 60 parts by weight.
After mixing the raw materials containing parts by weight (however, Ny66 + MXD6 = 100 parts by weight), melt extruding the mixture, and cooling the cooled raw film in the MD direction (the moving direction of the film) and the TD direction (the width direction of the film) in 2.8 It is characterized in that it is stretched at a stretching ratio of at least twice.

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).

[0012]

EXAMPLE 1 A mixture of nylon 66 (Ny66) and metaxylylene adipamide (MXD6) at a ratio of 80 parts by weight and 20 parts by weight, respectively, was melt-kneaded at 280 ° C. in an extruder.
The melt was extruded from a die having a diameter of 90 mm as a cylindrical film, and then rapidly cooled with water to produce a raw film.

The Ny66 used was Nylon 66 (UBE Nylon 2026 (trade name), relative viscosity η _r = 3.5) manufactured by Ube Industries, Ltd., and the MXD6 used was Mitsubishi Gas Chemical Co., Ltd. ) Metaxylylene adipamide [MX Nylon 6007 (trade name), relative viscosity η
_r = 2.7].

Next, as shown in FIG. 1, after this raw film 11 is inserted between a pair of nip rolls 12, it 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 bubble 16 was taken up by a pair of nip rolls 17 on the downstream side, whereby simultaneous biaxial stretching in the MD and TD directions by the tubular method was performed. 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 a biaxially stretched film 18 according to the present example.

Next, regarding the obtained stretched film 18,
The tear strength and impact strength (film impact) were measured, and the tearability and straight-line cut property were evaluated. The results are shown in Table 1 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 fixed on 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: With respect to the value E of the Elmendorf tearing strength, when 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
If it is over kg / cm, the tearability will decrease significantly,
In particular, the straight-line cutability drops sharply.

The straight-line cut property was evaluated as follows. That is, as shown in FIG. 2, 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 columns of comprehensive evaluation in Tables 1 and 2, ◎ indicates very good, ○ indicates good, and × indicates bad.

Examples 2 to 9 The same procedures as in Example 1 were carried out except that the mixing ratio of Ny66 and MXD6 and the stretching ratio were changed as shown in Table 1. An axially stretched film 18 was obtained. Regarding the film 18 according to each example, measurement and evaluation of various characteristics were performed in the same manner as in the first example. Table 1 shows the results.

Comparative Examples 1 to 8 The same procedures as in Example 1 were carried out except that the mixing ratio of Ny66 and MXD6 and the stretching ratio were changed as shown in Table 2, and the same processes as in Example 1 were repeated. An axially stretched film was obtained. For the film according to each comparative example, measurement and evaluation of various characteristics were performed in the same manner as in Example 1. Table 2 shows the results.

[0022]

[Table 1]

[0023]

[Table 2]

Discussion of Examples and Comparative Examples From Table 1, the film 18 according to this example contains Ny66 and MXD6, and the content of Ny66 is 40 to 85 parts by weight, and the content of MXD6 is 15 to 60 parts by weight. Part, the stretching ratio of the film at the time of biaxial stretching is MD direction and TD
2.8 times or more in both directions.
It can be seen that the tearability is excellent at 7.0 kg / cm or less, and the straight-line cutability 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 Table 2, the films according to Comparative Examples 1, 2 and 3 have stretch ratios satisfying the conditions according to the present invention.
The content of Ny66 is more than 85 parts by weight, while MXD6
Is less than 15 parts by weight (including 0), so that even if the impact strength is sufficient, the linear cutability is poor.

In the films according to Comparative Examples 4 and 5, the stretch ratio satisfies the condition according to the present invention, but the content ratio of Ny66 is
Since the content of MXD6 is less than 40 parts by weight (including 0) and the content of MXD6 is more than 60 parts by weight, even if the tearability and the straight-cutting property are good, the impact strength is poor and the surface base film is poor. Is difficult to use.

The films according to Comparative Examples 6, 7, and 8 were Ny
Although the content ratio of 66 and MXD6 is within the range according to the present invention, the draw ratio is smaller than the range according to the present invention, so that the tearability, the linear cut property and the impact strength are poor, and it is not suitable for practical use. Disappears.

[0028]

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 schematic view of a biaxial stretching apparatus used in a method for producing an easily tearable film according to an embodiment of the present invention.

FIG. 2 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 Biaxially stretched film

────────────────────────────────────────────────── (5) Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location B29L 7:00 (56) References JP-A-4-198329 (JP, A) JP-A-64- 6056 (JP, A) JP-A-56-49226 (JP, A) JP-A-53-49073 (JP, A) JP-A-52-104565 (JP, A) JP-A-48-54176 (JP, A)

Claims (2)

(57) [Claims] 1. The method according to claim 1, which comprises nylon 66 (Ny66) and metaxylylene adipamide (MXD6).
40 to 85 parts by weight, and MXD6 15 to 60 parts by weight (provided that
Ny66 + MXD6 = 100 parts by weight). 2. Nylon 66 (Ny66) is 40 to 85 parts by weight and metaxylylene adipamide (MXD6) is 15 to 60 parts by weight.
After mixing the raw materials containing parts by weight (however, Ny66 + MXD6 = 100 parts by weight), melt extruding the mixture, and cooling the cooled raw film in the MD direction (the moving direction of the film) and the TD direction (the width direction of the film) in 2.8 A method for producing an easily tearable film, wherein the film is stretched at a stretching ratio of at least twice.