JPH1148424A - Biaxially oriented polyamide film and self-supporting packaging bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film, retaining the excellent characteristics of biaxially oriented polyamide film, which are such as toughness, transparency, resistance to pin-hole, resistance to shock, resistance to dropping bag or the like, and excellent in adhesive property between a substrate film and a sealant film as well as the straight tearable property while capable of making a self-supporting packaging bag, easy in opening seal, and a self-supporting packaging bag. SOLUTION: A biaxially oriented polyamide film is constituted of the mixture, having the weight ratio of poly-ε-caplamide (N6) to a thermosetting polyamide except N6 such as polymethaxylene adipamide or polyhexamethylene sebacamide or the like of 80-95/20-5 and provided with the thickness of 12-30 μm while polyurethane base resin or polyurethane urea base resin is applied on at least one side of the film with the coating amount of 0.02-0.5 g/m<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-contained packaging bag excellent in adhesiveness to a sealant film comprising a mixture of poly-.epsilon.-capramide (N6) and a thermoplastic polyamide other than N6, and excellent in straightness in tearing in the longitudinal direction. The present invention relates to a biaxially stretched polyamide film for a base material, a laminated film for a self-supporting packaging bag in which a sealant film is laminated thereon, and a self-standing packaging bag using the laminated film.

[0002]

2. Description of the Related Art A laminated film packaging bag in which various biaxially stretched plastic films (base films) and a sealant film are laminated is widely used for packaging foods, pharmaceuticals, daily necessities, detergents and the like. In particular, high-strength biaxially stretched polyamide film is used as a base film for packaging of liquids or viscous materials that require pinhole resistance, impact resistance, and bag fall resistance (drop bag break resistance). Is used.

[0003] However, a packaging bag using a usual biaxially stretched polyamide film has a problem that the tear straightness is not good, the packaging bag does not tear linearly when the packaging bag is opened, and the contents are easily scattered. Was.

[0004] In order to solve this problem,
An easily tearable biaxially stretched polyamide film composed of a mixture of N6 and a thermoplastic polyamide other than N6 such as polymethaxylylene adipamide (MXD6) and polyhexamethylene sebacamide (N610), and a sealant film laminated on the film. (Japanese Unexamined Patent Application Publication No. Hei.
No. 200958, No. 5-220837, No. 7-113015).

[0005] However, when such a laminated film is used as a self-supporting packaging bag, the self-standing packaging bag needs to have rigidity.
If a film having a thickness of μm is used and the adhesiveness between the base film and the sealant film is insufficient, there is a problem that delamination occurs at the time of opening to deteriorate the tearing property, and in some cases, the film cannot be opened. In addition, the laminating strength between the base film and the sealant film may be reduced due to a boil treatment, a retort treatment, or a change with time of the product (content-filled product), which may make it impossible to tear easily when opening.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a biaxially stretched polyamide film having toughness and transparency, pinhole resistance,
Maintains excellent properties such as impact resistance and bag fall resistance, and
Excellent adhesion between base film and sealant film,
An object of the present invention is to provide a film and a self-contained packaging bag that can be made into a self-contained packaging bag that has good tear straightness and that can be easily opened.

[0007]

The present invention solves the above-mentioned problems, and the gist thereof is as follows. 1. The weight ratio between N6 and a thermoplastic polyamide other than N6 is
A biaxially stretched polyamide film having a thickness of 12 to 30 μm comprising a mixture of 80 to 95/20 to 5, and a polyurethane resin or a polyurethane urea resin on at least one side having a thickness of 0.02 to
A biaxially stretched polyamide film for a base material of a self-standing packaging bag, which is coated with a coating amount of 0.5 g / m ² and has excellent adhesiveness to a sealant film and excellent straightness in tearing in a longitudinal direction. 2. 2. A laminated film for a self-supporting packaging bag, which has good tear straightness in the longitudinal direction, wherein a sealant film is laminated on a coated surface (one surface) of the biaxially stretched polyamide film according to item 1. 3. An easy-opening self-supporting packaging bag made from the laminated film according to Item 2 so that the longitudinal direction of the biaxially stretched polyamide film is in the tearing direction.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The biaxially stretched polyamide film in the present invention is composed of a mixture of N6 and a thermoplastic polyamide other than N6. Here, N6 includes not only a homopolymer but also an N6 copolymer containing the same as a main component.
The polyamide mixture may contain other polymers or polyamide additives as long as the effects of the present invention are not impaired.

As the thermoplastic polyamide other than N6,
MXD6, N610 and copolyamides containing these as main components are preferably used.

It is necessary that the ratio between N6 and the thermoplastic polyamide other than N6 is 80 to 95/20 to 5 by weight. If the proportion of N6 is larger than this range, the tearing straightness in the longitudinal direction will not be exhibited, while if the proportion of N6 is smaller than this range, strength properties such as pinhole resistance, impact resistance, and falling bag resistance will be exhibited. Is impaired.

The biaxially stretched polyamide film of the present invention comprises:
A polyurethane resin or a polyurethane urea resin is coated on at least one side with a coating amount of 0.02 to 0.5 g / m ² (coating amount on one side) in order to impart easy adhesion and improve adhesion with the sealant film. It has been engineered. The polyurethane resin or the polyurethane urea resin is desirably cross-linked with a melamine cross-linking agent or an epoxy cross-linking agent. If the coating amount is less than the above range, sufficient adhesive strength cannot be obtained, while if it is too large, impact resistance, pinhole resistance, tear straightness and the like are reduced.

The lamination strength (peeling strength) between the biaxially stretched polyamide film and the sealant film is 300 g / 15
It is desirable to select the type of the coating agent and the amount of coating so as to be at least 500 mm, preferably at least 500 g / 15 mm. If the lamination strength is low, delamination occurs between the biaxially stretched polyamide film and the sealant film at the time of opening, and tear straightness cannot be obtained, or in some cases, tearing cannot be performed.

The self-standing packaging bag using the biaxially stretched polyamide film coated with the polyurethane resin or the polyurethane urea resin of the present invention has high peeling strength and heat treatment such as boiling treatment or retort treatment or the contents ( In particular, there is little decrease in laminate strength due to aging of pharmaceuticals, detergents, etc.), and it is particularly suitable as a self-supporting packaging bag requiring long-term storage.

The film of the present invention has a thickness of 12 to 30.
μm, preferably 15 to 25 μm.
If the thickness is less than 12 μm, the tear straightness and impact resistance are poor. If it exceeds 30 μm, the tear straightness and impact resistance are effective, but the transparency and pinhole resistance (bending fatigue resistance) are poor. It is not preferable because it decreases.

Next, an example of a method for producing the biaxially stretched polyamide film of the present invention will be described. First, N6
And a polyamide other than N6 in a predetermined ratio, and the mixture is supplied to an extruder.
It is extruded into a sheet from a T-die, wound around a cooling drum and quenched to obtain a substantially non-oriented unstretched film.

If the temperature of the melt-kneading is too low, kneading becomes insufficient and fish eyes are generated, resulting in poor stretchability. On the other hand, if this temperature is too high, amide exchange between N6 and polyamide other than N6 is performed. A reaction occurs, and the shape of the polyamide particles other than N6 dispersed in N6 becomes very fine, and the tear straightness becomes insufficient.

When the softened sheet extruded from the T-die is wound around a cooling drum and taken off,
It is desirable that the draft ratio (DR), that is, the ratio between the discharge gap of the T-die and the thickness of the sheet, is 5 or more. DR
Indicates the apparent amount of deformation between the T die and the cooling drum. As the DR increases, the shape of the polyamide particles other than N6 in N6 becomes elongated and dispersed in the longitudinal direction of the film. , Good tear straightness.

Subsequently, the obtained unstretched film is simultaneously biaxially stretched as follows to obtain a biaxially stretched film.

First, the unstretched film is immersed in water to adjust the water content to 1 to 6% by weight. Unless this water-absorbing treatment is applied, the film is unfavorably stretched or uneven in thickness when stretched.

Next, an aqueous emulsion of a polyurethane resin or a polyurethane urea resin is applied to at least one surface of the unstretched film. As the polyurethane resin or the polyurethane urea resin, a self-emulsifying resin is preferable, and in order to improve water resistance, it is desirable to use a melamine crosslinking agent or an epoxy crosslinking agent, and a crosslinking catalyst if necessary. .

The unstretched film coated with the water emulsion is introduced into a tenter type simultaneous biaxial stretching machine, dried and preheated, and then at a temperature of 150 to 220 ° C. and a stretching ratio of 2.5 to 4.0 times in the longitudinal and transverse directions, respectively. It is simultaneously biaxially stretched so that
If the stretching temperature is too low, the dimensional stability of the stretched film will be poor, and if it is too high, crystallization will proceed and the stretchability will deteriorate. Also, if the stretching ratio is small, the strength of the film is reduced, and if the stretching ratio is too large, in the stretching step,
Film cutting occurs frequently, and the operability deteriorates.

The biaxially stretched film is subsequently heat treated to fix the biaxial orientation. The conditions for this heat treatment are preferably a temperature of 180 to 220 ° C., a treatment time of 3 to 10 seconds, and a relaxation ratio in the width direction of 0 to 10%. Among the heat treatment conditions, a particularly important condition in the present invention is a heat treatment temperature. That is, if the heat treatment temperature is lower than 180 ° C., the dimensional stability of the film is deteriorated, while if the heat treatment temperature is higher than 220 ° C., the toughness and impact resistance of the film are impaired.

The coating of the polyurethane resin or the polyurethane urea resin is usually performed on one side of the film.
When the film of the present invention is used as one layer of a multilayer film having three or more layers, it is preferable to apply the film to both sides. When coating on one side, the other side is left untreated or subjected to corona treatment or the like.

[0025] Instead of applying a polyurethane resin or a polyurethane urea resin to an unstretched film, it may be applied to a stretched film. Also,
If necessary, a coating treatment such as polyvinylidene chloride or polyvinyl alcohol can be applied to impart barrier properties.

The biaxially stretched polyamide film of the present invention comprises:
In addition to having excellent tear straightness in the longitudinal direction of the film, it also has excellent pinhole resistance, dimensional stability and impact resistance, and thus is suitable as a base film for a self-supporting packaging bag.

In the case of a self-supporting packaging bag, a sealant film (heat sealing film) is laminated on the resin-coated surface of the biaxially stretched polyamide film to form a laminated film. As the sealant film, polypropylene (PP),
A low melting point film made of polyethylene (PE), ethylene-vinyl acetate copolymer or the like is used. The sealant film has a thickness of 80 to 180 μm, preferably 100 to 15 μm.
A thickness of 0 μm is appropriate.

If necessary, the surface of the non-laminated sealant film of the biaxially stretched polyamide film may be
In order to improve rigidity, impact resistance, gas barrier properties, and the like, a reinforcing sheet such as a stretched plastic film such as polyethylene terephthalate, nylon, or polypropylene, paper, or a metal foil such as an aluminum foil is laminated.

By making such a laminated film such that the longitudinal direction of the biaxially stretched polyamide film is in the tearing direction, an easily openable self-standing packaging bag is obtained. And since this self-supporting packaging bag is excellent in bag dropping resistance and tear straightness in addition to pinhole resistance and impact resistance,
Including foods such as soup, jam and retort pouch,
It is useful as a packaging bag for toiletries such as pharmaceuticals, daily necessities and detergents.

[0030]

Next, the present invention will be specifically described with reference to examples and comparative examples. In addition, the measurement and evaluation methods are as follows. (1) Tear straightness A sample having the dimensions shown in Fig. 1 was prepared by laminating two laminated films on the sealant film surface and sealing both ends, and a notch with a length of 5 mm in the width direction as shown in Fig. 1 (I
Notch) was made, the film was torn by hand in the long side direction from this cut, and as shown in FIG. 2, the opening X of the upper and lower films at which the tear propagation end reached another seal portion was measured and evaluated in the following four steps. . ◎: X is 5mm or less ○: X is 6 to 10mm △: X is 11 to 15mm ×: X is 16mm or more (2) Pinhole resistance 20cm x 30cm rectangle adjusted at 20 ° C and 65% RH Was attached to a gelbo flex tester (manufactured by Tester Sangyo Co., Ltd.), and a bending test was performed 10,000 times. For the film after the bending test, a coloring liquid (Ageless Checker manufactured by Mitsubishi Gas Chemical Company) was applied to one side of the film, and the number of locations where the liquid permeated the opposite side was counted as the number of pinholes. (3) Impact resistance A square film of 10 cm × 10 cm adjusted at 23 ° C. and 50% RH was mounted on a film impact tester (manufactured by Toyo Seiki Seisaku-sho, Ltd.), and the impact strength Y was read from the scale plate. It was evaluated on a scale. ◎: Y is 16 kgf ・ cm or more ○: Y is 11 to 15 kgf ・ cm △: Y is 6 to 10 kgf ・ cm ×: Y is 5 kgf ・ cm or less (4) Dropping resistance 25 cm × 12 cm freestanding bag Is filled with 500 ml of water and at a temperature of 5 ° C,
The operation of dropping from the height of 1.5 m onto the concrete floor surface was repeatedly performed, and the number of times Z until the bag was broken (leaked) was measured, and evaluated in the following four steps. ：: Z is 21 times or more (20 times without breaking) ○: Z is 11 to 20 times △: Z is 5 to 11 times ×: Z is 4 times or less (5) Adhesiveness (lamination strength) Width 15 mm The peel strength between the biaxially stretched polyamide film and the sealant film was evaluated as normal T
It was measured at a tensile speed of 300 mm / min by a mold method. (6) Comprehensive evaluation The results of the above (1) to (5) were comprehensively evaluated in the following four stages. ◎: Excellent ○: Excellent △: Good (OK) ×: Bad (Not OK)

Example 1 N6 (manufactured by Unitika Ltd., trade name: A1030BRF) and MXD6
(Mitsubishi Gas Chemical Company, trade name: MX Nylon 6007) and a mixture with a weight ratio of 90/10 is supplied to an extruder equipped with a coat hanger type T-die, melt-kneaded at a temperature of 260 ° C., and extruded from the T-die. The mixture was extruded, and was brought into close contact with a cooling drum adjusted to 20 ° C. and rapidly cooled (DR8.8) to obtain an unstretched film having a thickness of about 160 μm. The obtained unstretched film was sent to a hot water tank adjusted to 50 ° C., and subjected to a soaking treatment for 2 minutes to adjust the moisture content to 4.1%. Next, self-emulsifying polyurethane polyurea resin 100
6 parts by weight of a melamine-based crosslinking agent was added to parts by weight,
A water emulsion having a solid content of 6% by weight was applied to one surface of the unstretched film by an air knife method, and dried. The unstretched coated film was introduced into a tenter-type simultaneous biaxial stretching machine, stretched 3.3 times in each of the longitudinal and transverse directions at a temperature of 190 ° C, and a relaxation rate of 5% in the transverse direction.
After a heat treatment for 2 seconds, the film was gradually cooled to room temperature to obtain a biaxially stretched polyamide film (ON1). This biaxially stretched polyamide film had a thickness of 15 μm, and had a layer with a coating amount of a polyurethane resin of 0.1 g / m ^{2 on} one side.

Examples 2 to 6 and Comparative Examples 1 to 10 Biaxially stretched polyamide films (ON2 to ON16) having the composition, thickness and coating amount of polyurethane resin shown in Table 1 were prepared in the same manner as in Example 1. ).

[0033]

[Table 1]

Examples 7 to 18 and Comparative Examples 11 to 24 Laminated films having the packaging materials shown in Tables 2 and 3 were prepared by a dry laminating method, and tear straightness, pinhole resistance,
Tables 2 and 3 show the results of the evaluation of impact resistance, bag fall resistance and adhesiveness. The other films used in Tables 2 and 3 are as follows. LL: Linear low-density polyethylene film (thickness 80 to 150
μm) PET: polyethylene terephthalate film (thickness 12
μm) OPP: stretched polypropylene film (thickness 20 μm)

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

According to the present invention, the toughness and transparency of the biaxially stretched polyamide film, the pinhole resistance, the impact resistance,
A film and self-supporting film that retains excellent properties such as bag drop resistance, has excellent adhesion between the base film and the sealant film, has good tear straightness, and can be easily opened as a self-contained packaging bag. A packaging bag is provided. The self-standing packaging bag of the present invention is particularly suitable as a packaging bag for liquids such as foods and toiletries.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a sample used for evaluation of tear straightness of a laminated film.

FIG. 2 is an explanatory view showing a state after tearing of the sample of FIG. 1;

Claims (5)

[Claims] 1. A biaxially stretched polyamide film having a thickness of 12 to 30 μm comprising a mixture of poly-ε-capramide (N6) and a thermoplastic polyamide other than N6 in a weight ratio of 80 to 95/20 to 5, A polyurethane resin or a polyurethane urea resin is coated on at least one surface at a coating amount of 0.02 to 0.5 g / m ² , and is excellent in adhesiveness to a sealant film and straightness in tearing in a longitudinal direction. Biaxially stretched polyamide film for base material of self-supporting packaging bags. 2. The biaxially stretched polyamide film for a base material of a self-standing packaging bag according to claim 1, wherein the thermoplastic polyamide other than N6 is polymethaxylylene adipamide or polyhexamethylene sebacamide. 3. A laminated film for a self-supporting packaging bag having good tear straightness in the longitudinal direction, wherein a sealant film is laminated on a coated surface (one surface) of the biaxially stretched polyamide film according to claim 1 or 2. 4. The laminated film for a self-supporting packaging bag according to claim 3, wherein a reinforcing sheet is laminated on the surface on the opposite side where the sealant film is laminated and has good tear straightness in the longitudinal direction. 5. An easy-opening self-supporting packaging bag made from the laminated film according to claim 3 so that the longitudinal direction of the biaxially stretched polyamide film is in the tearing direction.