JPH0699488A - 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:A raw material consisting of 40-85 pts.wt. of nylon 6-66 (Ny 6-66) and 15-60 pts.wt. of m-xylyleneadipamide MXD 6) (Ny 66 + MXD 6 = 100 pts.wt.) is mixed and the resulting mixture is extruded in a molten state to form a raw film 11. After cooling, the raw film 11 is stretched by 2.8 times or more in both of the moving direction (MD direction) and traverse direction (TD direction) of the film to obtain an easy tearing film 18.

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 does not cut straight when used,
There was a problem opening it. 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 comprises a nylon 6-66 copolymer (Ny6-
66) and an aromatic nylon metaxylylene adipamide (MXD6), 40 to 85 parts by weight of Ny6-66 and 15 to 60 parts by weight of MXD6 (however, Ny6-6
6 + MXD6 = 100 parts by weight).
The chemical formula of MXD6 is shown in Chemical Formula 1 below.

[0007]

[Chemical 1]

The content ratio of Ny6-66 and MXD6 is 40 to 85 parts by weight of Ny6-66 and 15 to 60 parts by weight of MXD6 (however, Ny6-66 + MXD6 = 100 parts by weight), preferably Ny6- 50 to 80 parts by weight of 66, 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. Then, by containing Ny6-66, shrinkability can be imparted to the easily tearable film.

Next, in the method for producing an easily tearable film according to the present invention, 40 to 85 parts by weight of Ny6-66 and 15 parts of MXD6 are used.
~ 60 parts by weight (however, Ny6-66 + MXD6 = 100 parts by weight) are mixed, the mixture is melt-extruded, and then the cooled raw film is subjected to MD direction (film moving direction) and TD direction (film width). (Direction) both are 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.).

[0012]

Example 1 Nylon 6-66 copolymer (Ny6-66) and metaxylylene adipamide (MXD6) were mixed in a proportion of 80 parts by weight and 20 parts by weight, respectively, in an extruder. After melt-kneading at 0 ° C., the melt was extruded from a die having a diameter of 90 mm as a cylindrical film, and then rapidly cooled with water to prepare a raw film.

The one used as Ny6-66 is
Ube Industries Co., Ltd. nylon 6-66 copolymer [UBE nylon 5023 (trade name), relative viscosity η _r = 3.6], used as MXD6 is Mitsubishi Gas Chemical Co., Ltd. metaxylylene azide. Pamide [MX Nylon 60
07 (trade name), relative viscosity η _r = 2.7].

Next, as shown in FIG. 1, 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 therein, 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, this stretched film 18 was placed in a tenter type heat treatment furnace and heat-set at 160 ° 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 Tables 1 and 2 below. The measurement of the tear strength,
The film was stretched by measuring the Elemendorf tear strength (kg / cm 2) according to JIS-Z1702.

The impact strength was measured by using a film impact tester manufactured by Toyo Seiki Co., Ltd., and a semi-spherical 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.

As for the easy tearability, the value E of Elemendorff 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 exceeds 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. 2, cuts 21 are formed in a 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 column of comprehensive evaluation in Table 1, ⊚ indicates very good, ∘ indicates good, and x indicates bad. Further, when the shrinkage ratio of the stretched film 18 was measured as described below, it was MD direction / TD direction = 30% / 29%. Regarding the shrinkage ratio, a marked line is drawn on the film at intervals of 10 cm, and the marked line length l ₀ before hot water treatment and the marked line length l after hot water treatment at 95 ° C.
Determined in from the difference .DELTA.l _S between _{S (Δl S / l 0)} × 100 (%).

Examples 2 to 9 In Example 1 except that the mixing ratio of Ny6-66 and MXD6 and the draw ratio were changed as shown in Table 1,
The biaxially stretched film 18 according to Examples 2 to 9 was obtained by the same manufacturing process as described above. 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 Tables 1 and 2. Further, when the shrinkage rate of the film 18 according to Example 4 was measured, MD / TD = 32
% / 30%. In the case of the film 18 according to Example 6,
MD / TD = 33% / 33%.

Comparative Examples 1 to 8 In the above-mentioned Example 1, the mixing ratio of Ny6-66 and MXD6 and the draw ratio were changed as shown in Table 3, and Example 1 was changed.
The biaxially stretched films according to Comparative Examples 1 to 8 were obtained by the same manufacturing process as in. 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 Tables 3 and 4. Moreover, when the shrinkage rate of the film according to Comparative Example 1 was measured, it was MD / TD = 29% / 28%. In the case of the film according to Comparative Example 2, MD / TD =
It was 31% / 30%.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

Consideration of Examples and Comparative Examples From Tables 1 and 2, the film 18 according to this example is Ny6-
66 and MXD6 are contained, and the content ratio of Ny6-66 is
40 to 85 parts by weight, the content ratio of MXD6 is 15 to 60 parts by weight, and the stretching ratio of the film at the time of biaxial stretching is 2.8 times or more in both MD and TD directions. It can be seen that when it is less than / cm, it is easy to tear and the linear cut property is good or very good. Moreover, all of them have high impact strength of 6000 kg · cm / cm or more.

On the other hand, from Tables 3 and 4, the films according to Comparative Examples 1, 2 and 3 satisfy the conditions according to the present invention in the stretch ratio, but the content ratio of Ny6-66 is more than 85 parts by weight, while MXD6. Content of less than 15 parts by weight (including 0)
Therefore, even if the impact strength is sufficient, it is inferior in the linear cut property.

The films according to Comparative Examples 4 and 5 have a stretching ratio within the range according to the present invention, but the content of Ny6-66 is less than 40 parts by weight (including 0), while the content of MXD6 is less. Since it is more than 60 parts by weight, it is difficult to use as a surface base material film because it has poor impact strength even though it has good tearability and linear cuttability.

The films according to Comparative Examples 6, 7 and 8 are Ny.
The content ratios of 6-66 and MXD6 are within the range according to the present invention, but since the stretching ratios are all smaller than the range according to the present invention, easy tearability, linear cuttability and impact strength are poor, and practical Will not be suitable for.

[0031]

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 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. 2 is a diagram showing an evaluation method of linear cuttability.

[Explanation of symbols]

 11 Raw film 12,17 Nip roll 16 Bubble 18 Biaxially stretched film

Claims (2)

[Claims] 1. A nylon 6-66 copolymer (Ny6-6)
6) and metaxylylene adipamide (MXD6), 40 to 85 parts by weight of Ny6-66, and MXD6
An easily tearable film characterized by being 15 to 60 parts by weight (however, Ny6-66 + MXD6 = 100 parts by weight). 2. A nylon 6-66 copolymer (Ny6-6)
6) 40 to 85 parts by weight and metaxylylene adipamide (M
XD6) 15 to 60 parts by weight (however, Ny6-66 + MXD
6 = 100 parts by weight), and the mixture is melt-extruded, and then the cooled original film is stretched at a draw ratio of 2.8 times or more in both MD direction (film moving direction) and TD direction (film width direction). A method for producing an easily tearable film, which comprises stretching the film.