JPH07125132A - Wrapping material - Google Patents

Abstract

PURPOSE:To provide a wrapping material that has excellent characteristics on an easily openable property, shock resistance or the like, and can obtain a remarkable Improvement with respect to a gas barrier property. CONSTITUTION:The material has an aluminum oxide layer with a thickness of 100-4000Angstrom on at least one surface of a film (l.e., PA+MXD6=100 pts.wt.) containing 40-85wt.% polyamide (PA) and 15-60wt.% mxylylene adipamide (MXD6). Herein, PA is one kind or more of nylon 6 and nylon 66. The film is oriented at the magnification of 2.8 times or more respectively in the MD direction (the moving direction of the film) and TD direction (the width direction of the film).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a packaging material which is particularly excellent in easy-opening property, gas barrier property, impact resistance and the like, and can be used in the fields of foods, chemicals, industrial products and the like.

[0002]

2. Description of the Related Art In recent years, various proposals have been made for imparting linear cutting property (easy opening property) to a packaging material such as food when opening. For example, (a)
A laminated film having a uniaxially stretched film as an intermediate layer, (b) a structure that makes it easy to open by making fine scratches on the surface of the front substrate film, (c) attach an unsealing tape to the unsealing portion of the film The configuration, etc. However, in each case, the easy-open property and the impact strength were insufficient, and the economy was poor.

Particularly in the fields of foods and medicines, straight-line cutability for facilitating the opening and improving the appearance of the opening, gas barrier property for long-term storage, and preventing bag breakage are directly linked to the protection of contents. Impact resistance is required as an important characteristic. Regarding the gas barrier property, a packaging material having an aluminum foil has been proposed, but in this case, it has the drawback that it is not transparent and cannot be used in a microwave oven because it is a metal. Moreover, since metal aluminum is mixed in the plastic material, the suitability for recycling is poor, so it cannot be said to be a preferable packaging material from the viewpoint of environmental protection.

Although a structure in which a silicon oxide film and an aluminum oxide film are formed on a PET film instead of the aluminum foil has been proposed, it has a gas barrier property comparable to that of a packaging material having an aluminum foil, but is resistant to In addition to having insufficient impact resistance, it does not have easy opening property. On the other hand, the applicant has proposed an easily tearable film containing nylon 6 and metaxylylene adipamide (MXD6) in Japanese Patent Application Nos. 3-308427 and 4-253116.

This easily tearable film has made it possible to obtain substantially satisfactory results in terms of easy opening property, gas barrier property, impact resistance and the like, but the gas barrier property is as good as that of a packaging material having an aluminum foil. Not a level. Therefore, an object of the present invention is to provide a packaging material which has excellent properties such as easy opening property and impact resistance and, in addition, has a remarkable effect of improving gas barrier property.

[0006]

The packaging material according to the present invention is a film containing 40 to 85 parts by weight of polyamide (PA) and 15 to 60 parts by weight of metaxylylene adipamide (MXD6). , PA + MXD6 = 100 parts by weight) with an aluminum oxide layer of 100-4000Å on at least one surface.
It is characterized in that it is formed with a thickness of. MXD
The chemical formula of 6 is shown in the following chemical formula 1.

[0007]

[Chemical 1]

When MXD6 in the film is less than 15 parts by weight, the easy tearing property and the linear cutting property are deteriorated. When MXD6 is more than 60 parts by weight, the impact strength is significantly reduced and the practicality becomes poor. The polyamide (PA) in the film is at least one of nylon 6 and nylon 66. Specifically, nylon 6
Either nylon or nylon 66, a copolymer of both, or a mixture of these monomers and a copolymer may be used.

The film has the MD direction (the moving direction of the film) and the TD direction (the width direction of the film), respectively.
It is drawn at a magnification of 2.8 times or more, preferably 3.5 times or more. If the draw ratio is less than 2.8 times,
The easy tearing property and the straight line cutting property are inferior, and the impact strength is lowered, which causes a problem in practical use. Such a stretched film can be obtained by performing simultaneous biaxial stretching by, for example, a tubular method. Incidentally, necessary additives can be appropriately added to the film.

Examples of such additives include anti-blocking agents (such as inorganic fillers), water repellents (such as ethylene bisstearate) and lubricants (such as calcium stearate). The form of the aluminum oxide may be amorphous or crystalline. If the thickness of the aluminum oxide layer is less than 100Å, sufficient gas barrier properties cannot be obtained. On the other hand, if it is greater than 4000Å, the aluminum oxide layer is prone to cracking and the gas barrier properties are extremely deteriorated.

In the aluminum oxide layer, durability,
Other components, for example, metal oxides other than aluminum oxide may be added to improve strength and the like. The method for forming the aluminum oxide layer is arbitrary, and a vacuum deposition method is generally used. The film is a single layer, but may be a laminate film including an L-LDPE layer, a PP layer and the like. Further, the aluminum oxide layer may be formed not only on one side of the film but also on both sides.

[0012]

Example 1 Nylon 6 (Ny6) and metaxylylene adipamide (MXD6) were mixed at a ratio of 60 parts by weight and 40 parts by weight, respectively, and melt-kneaded in an extruder at 270 ° 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 Ny6 used was Nylon 6 [UBE Nylon 1023 FD (trade name), relative viscosity η _r = 3.6] manufactured by Ube Industries, Ltd., and the one used as MXD6 was manufactured by Mitsubishi Gas Chemical Co., Inc. Metaxylylene adipamide [MX nylon 6007 (trade name), relative viscosity η _r = 2.7]
Is.

Next, the obtained tube-shaped raw material was inserted between a pair of nip rolls, and then heated by a heater while injecting gas into the nip rolls, and air was blown from an air ring to the stretching start point to expand the bubbles. Then, simultaneous biaxial stretching in the MD direction and the TD direction by the tubular method was performed by taking them out with a pair of downstream nip rolls. The draw ratio during this stretching was 3.0 times in both MD and TD. Next, this stretched film was placed in a tenter type heat treatment furnace and heat-set at 210 ° C. to obtain a biaxially stretched film.

The biaxially stretched film was placed in a vacuum vapor deposition apparatus and heated to 880 ° C. under a vacuum of 0.7 × 10 ⁻⁴ Torr to form an aluminum oxide layer on one side of the film by vapor deposition to a thickness of 1000 Å. A packaging material according to this example was obtained. Next, the tear strength and impact strength (film impact) of this packaging material were measured, and the tearability and linear cuttability were evaluated. The results are shown in Table 1 below.
The tear strength is measured in the stretching direction of the packaging material.
Elemendorf tear strength (kg / cm according to JIS-Z1702
) Was measured.

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 less than 4500 kg · cm / cm, the performance as a surface base material is deteriorated and the practicality as a liquid packaging material becomes poor. Regarding the easy tearability, the value E of the Elemendorf tear strength was E ≦ 7 kg / cm, ○, 7 kg / cm <
E <9 kg / cm 2 was evaluated as Δ and E ≧ 9 kg / cm 2 was evaluated as x.
When E is 9 kg / cm or more, the easiness of tearing is remarkably reduced, and especially the linear cut property is rapidly reduced.

The linear cuttability was evaluated as follows. The film having a width of 20 cm is cut at predetermined intervals W _s , for example, at intervals of 2 cm, the film is torn along these cuts, and the width W _e of the other end of the film piece is measured to obtain the original distance W _s . The deviation α is calculated as follows. α = [(W _s −W _e ) / W _s ] × 100 This measurement was performed on 10 pieces of film, and if the average value α (%) was less than ± 10% ◎ (linear cutability Is very good), ± 10% ≤ α ≤ ± 30% is evaluated as ○ (good linear cutting property), and α (%) exceeding ± 30% is evaluated as × (poor linear cutting property). . α (%) is ± 30%
If it exceeds, it becomes difficult to cut the film straight.

Further, the oxygen permeability was measured as an index of the gas barrier property of the packaging material. This measurement is based on ASTM-D-398
According to 5, it was carried out under the conditions of 23 ° C. and 0% RH. The results are shown in Table 1 below. In the column of comprehensive evaluation in Table 1, ⊚ indicates very good, ∘ indicates good, and x indicates poor.

Examples 2 to 6 In Example 1 above, the composition and stretch ratio of the film and the thickness of the aluminum oxide layer were changed as shown in Table 1,
The packaging materials according to Examples 2 to 6 were obtained by the same manufacturing process as in Example 1. With respect to the packaging materials according to each example, various characteristics were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Examples 1 to 6 In the above Example 1, the composition and stretch ratio of the film and the thickness of the aluminum oxide layer were changed as shown in Table 1,
By the same manufacturing process as in Example 1, the packaging materials according to Comparative Examples 1 to 6 were obtained. With respect to the packaging material 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 1.

[0020]

[Table 1]

From Table 1, the packaging materials according to Examples 1 to 6 contain 40 to 80 parts by weight of Ny6 and 20 to 60 parts by weight of MXD6 and are stretched 3.0 times or more in the MD and TD directions, respectively. Aluminum oxide layer on one side of the film
It can be seen that each of them has a tear strength of 7.0 kg / cm or less, excellent tearability, and good or very good linear cutability, because they are formed with a thickness of 500 to 3000Å. Moreover, all of them have high impact strength of 6000 kg · cm / cm or more. Furthermore, the oxygen permeability is very small and the gas barrier property is excellent. In addition, since aluminum foil or the like is not used, it has transparency, can be used in a microwave oven, and is suitable for recycling, which is preferable from the viewpoint of environmental protection.

On the other hand, the films according to Comparative Examples 1 and 2 are within the range according to the present invention with respect to the draw ratio and the thickness of the aluminum oxide layer, but since they are films made of only Ny6, they have impact strength and gas barrier properties. Is good,
The straight line cutting property is poor. The film according to Comparative Example 3 is within the range according to the present invention with respect to the composition of the film and the thickness of the aluminum oxide layer, but since the stretching ratio of the film is small, even if the gas barrier property is good, the tear strength is high. Large, easy tearing and poor linear cutting,
Moreover, the impact strength is also inferior.

The films according to Comparative Examples 4 and 5 had a composition of the film and a draw ratio within the range according to the present invention, but the thickness of the aluminum oxide layer was outside the range according to the present invention, and thus the film was easy to tear. Although the linear cut property and the impact strength are good, the gas barrier property is poor. The film according to Comparative Example 6 has a composition of the film within the range according to the present invention, but is out of the range according to the present invention with respect to the draw ratio and the thickness of the aluminum oxide layer, and therefore has a linear cut property and a gas barrier property. It is bad.

[0024]

The packaging material according to the present invention has excellent properties such as tear strength, easy tearability, straight line cutting property and impact strength, and also has excellent gas barrier property.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // B29K 77:00 B29L 7:00

Claims (3)

[Claims] 1. A film containing 40 to 85 parts by weight of polyamide (PA) and 15 to 60 parts by weight of metaxylylene adipamide (MXD6) (provided that PA + MXD6 = 100 parts by weight) has aluminum oxide on at least one surface. Layer 100 ~
A packaging material characterized by being formed with a thickness of 4000Å. 2. The polyamide (PA) is nylon 6
The packaging material according to claim 1, wherein the packaging material is one or more of nylon 66 and nylon 66. 3. The film is stretched at a magnification of 2.8 times or more in each of the MD direction (the moving direction of the film) and the TD direction (the width direction of the film). The packaging material described in.