JP2833980B2 - Easy tearable 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 film.
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. Therefore, an object of the present invention is to provide an easily tearable film having excellent tearability and straight-line cutting properties and having sufficient strength, and a method for producing the film.

[0006]

The easily tearable film according to the present invention contains 55 to 85 parts by weight of nylon 6 (Ny6) and 15 to 45 parts by weight of metaxylylene adipamide (MXD6). (However, Ny6 + MXD6 = 100 parts by weight)
In addition, the melt viscosity ratio (η _MXD6 / η _Ny6 ) at 270 ° C. and a shear rate of 10 ² sec ⁻¹ is 0.2 to 10.0, and the MD direction (moving direction of the film) and the TD direction (width of the film) Direction) in both cases.
The chemical formula of MXD6 is shown in Chemical Formula 1 below.

[0007]

Embedded image

When the content of 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. When the ratio of the melt viscosity (η _MXD6 / η _Ny6 ) is out of the above range, the tearability and the linear cut property are remarkably reduced.

[0009] The melt viscosity of each resin can be measured using a flow tester. Next, the method for producing an easily tearable film according to the present invention comprises: 55 to 85 parts by weight of Ny6 and MXD6.
15 to 45 parts by weight (Ny6 + MXD6 = 100
Parts by weight) and a raw material having a melt viscosity ratio (η _MXD6 / η _Ny6 ) of 0.2 to 10.0 at 270 ° C. and a shear rate of 10 ² sec ⁻¹ were mixed, and the mixture was melt-extruded and then cooled. The raw film is stretched at a magnification of 2.8 times or more in both the MD and TD directions.

The form of the mixture of the raw materials is arbitrary, and may be, for example, kneaded pellets produced by melting and kneading both raw materials with a biaxial kneader, or mixed pellets obtained by mixing the raw material pellets with a blender. 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 linear cutting property are inferior. In addition, the impact strength is reduced, causing a problem in practicality. The stretching is
It is preferable to carry out 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 6 (Ny6) and metaxylylene adipamide (MXD6) at a ratio of 60 parts by weight and 40 parts by weight, respectively, was melt-kneaded by a twin-screw kneader, and the melt was mixed. After being extruded into a strand, the mixture was rapidly cooled with water and then cut with a rotary cutter to produce kneaded pellets.

The Ny6 used was Nylon 6 (UBE Nylon 1022 FD (trade name), number average molecular weight 22000) manufactured by Ube Industries, Ltd. at 270 ° C. and a shear rate of 10 ² sec ^-1 . The melt viscosity η _Ny6 is 7100 poise. The MXD6 used was metaxylylene adipamide [MX Nylon 6007 manufactured by Mitsubishi Gas Chemical Company, Ltd.].
(Trade name), number average molecular weight 25000].
The melt viscosity η _MXD6 at a shear rate of 10 ² sec ^-1 is 6000 poise. Therefore, the ratio of the melt viscosities of both resins at 270 ° C. and a shear rate of 10 ² sec ⁻¹ (η _MXD6 / η _Ny6 ) is 0.85.

Next, the kneaded pellets are put into a single-screw extruder, melt-kneaded at 270 ° C., and the melt is extruded as a cylindrical film from a die having a diameter of 90 mm. Was prepared. Next, after the raw film is inserted between a pair of nip rolls, while being heated by a heater while gas is being injected thereinto, air is blown from an air ring to a stretching start point to expand the bubble into a bubble, and a pair of the downstream side is expanded. , And simultaneous biaxial stretching in the MD and TD directions was performed by a tubular method. The magnification at the time of this stretching was 3.0 times in both the MD and TD directions. Next, this stretched film was placed in a tenter-type heat treatment furnace and heat-set at 210 ° C. to obtain an easily tearable film according to this example.

Next, the obtained stretched film was measured for impact strength (film impact) and evaluated for straight-line cutability. The results are shown in Table 1 below.
The measurement of the impact strength was performed by using a film manufactured by Toyo Seiki
A semi-circular pendulum (1/2 inch diameter, weight 30
kg-cm 2) and measuring the impact strength required for punching the film. The impact strength was evaluated as ○ when the impact strength was 4500 kg · cm / cm or more, and evaluated as × when the impact strength was less than 4500 kg · cm / cm 2. If the impact strength is less than 4500 kg · cm / cm, the performance of the surface base material will decrease, and the practicality as a liquid packaging base material will be poor.

The straight-line cutability was evaluated as follows. In other words, after making cuts at 2 cm intervals on a 20 cm wide film and tearing the film along these cuts,
The width W _e of the other end of the film piece is measured, the deviation α between the original distance W _s determined as follows. α = _{[(W s -W e) / W} s ] × 100

This measurement was performed on 10 pieces of film, and those having an average value α (%) of less than ± 10% were evaluated as ◎ (very good linear cutability), ± 10% ≦ α ≦ ± A sample of 30% was evaluated as ○ (good linear cut property), and a sample with α (%) exceeding ± 30% was evaluated as × (poor linear cut property). In addition, 80% or more of the film pieces are ± 10% ≦ α ≦ ± 30%, but nearly 20% of the film pieces are ± 30% ≦ α ≦ ± 40% as △ (slightly unstable in linear cutability). did. If α (%) exceeds ± 30%, it becomes difficult to cut the film straight.
In the comprehensive evaluation column of Table 1, ◎ indicates very good, は indicates good, and × indicates bad.

Examples 2 to 6 In the above Example 1, the composition ratios of Ny6 and MXD6 and the melt viscosities were changed as shown in Table 1. A tearable film was obtained. Also for the easily tearable film according to each of the examples, the impact strength was measured and the linear cut property was evaluated in the same manner as in Example 1. Table 1 shows the results.

[0019] In Comparative Examples 1-5 Example 1, the composition ratio and melt viscosity of Ny6 and MXD6 changed as shown in Table 1, according to Comparative Examples 1 to 5 by the same manufacturing steps as in Example 1 Film I got As for the film according to each comparative example, similarly to Example 1,
The impact strength was measured and the straight-line cut property was evaluated. Table 1 shows the results.

[0020]

[Table 1]

According to Table 1, the easily tearable film according to the present example contains 55 to 85 parts by weight of Ny6 and 15 to 45 parts by weight of MXD6, and at 270 ° C. and a shear rate of 10 ² sec ^-1 . The ratio of melt viscosity (η _MXD6 / η _Ny6 ) is 0.2 to 10.0 and both MD and TD are stretched at a ratio of 2.8 or more, so that the impact strength is 4650 kg · cm / c in all cases.
It can be seen that the resin has a high impact strength of at least m and has a good or very good straight-line cut property. On the other hand, in the film according to Comparative Example 1, the composition ratio of Ny6 and MXD6 is within the range according to the present invention, but the melt viscosity ratio (η _MXD6 / η _Ny6 ) is 1
Since it exceeds 0.0, the impact strength and straight-line cutability are poor.

The film according to Comparative Example 2 was composed of Ny6 and MX.
Although the composition ratio of D6 is within the range according to the present invention, η _MXD6 /
Since η _Ny6 is smaller than 0.2, even if the impact strength is sufficient, it is inferior in straight-line _cutability . The films according to Comparative Examples 3 and 4 have η _MXD6 / η _Ny6 within the range according to the present invention,
Since the composition ratio of Ny6 and MXD6 is out of the range according to the present invention, there is a problem in the linear cut property even if the impact strength is sufficient. Since the film according to Comparative Example 5 was a film composed of only Ny6, the linear cutability was poor even though the impact strength was sufficient.

[0023]

According to the easily tearable film and the method for producing the same according to the present invention, it is possible to obtain a film having excellent tearability and straight-cutting properties and having sufficient strength.

Continuation of the front page (51) Int.Cl. ⁶ identification code FI B29L 7:00 (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 55/02-55/16 C08J 5/18 CFG

Claims (2)

(57) [Claims] 1. Nylon 6 (Ny6) in an amount of 55 to 85 parts by weight
And meta-xylylene adipamide (MXD6) 15-45 weight
Parts (however, Ny6 + MXD6 = 100 parts by weight)
Both, 270 ° C, shear rate 10^Twosec^-1Of melt viscosity at
Ratio (η_MXD6/ Η _Ny6) Is 0.2 to 10.0 and MD direction
(Moving direction of film) and TD direction (width direction of film)
Directionally easy-to-tear film stretched at a magnification of 2.8 times or more
M 2. Nylon 6 (Ny6) is added in an amount of 55 to 85 parts by weight.
And meta-xylylene adipamide (MXD6) 15-45 weight
Parts (however, Ny6 + MXD6 = 100 parts by weight)
Both, 270 ° C, shear rate 10^Twosec^-1Of melt viscosity at
Ratio (η_MXD6/ Η _Ny6) Is 0.2 ~ 10.0,
After melt extruding the mixture, the cooled raw film
MD direction (moving direction of film) and TD direction (fill
Stretching at a magnification of 2.8 times or more.
A method for producing an easily tearable film.