JP3234540B2 - Polyamide multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyamide-based multilayer film having improved pinhole resistance.

[0002]

2. Description of the Related Art Hitherto, a multilayer film containing a polyamide resin layer has been widely used in various fields as a film having gas barrier properties, toughness, etc., for example, polyamide resin layer / ethylene-vinyl acetate copolymer. A multilayer film in which a compound layer / a polyamide-based resin layer is provided in this order seems to be a once-possible film. As the polyamide-based resin layer in such a multilayer film, a layer composed of a composition layer of a crystalline polyamide and an amorphous polyamide is also known, and is a noteworthy product because of its good stretchability.

[0003] However, these multilayer films have some difficulty in pinhole resistance. That is, for example, when used for packaging of angular articles, the angular portions are apt to produce pinholes, and the pinholes also hinder the excellent gas barrier properties of the multilayer film.

[0004]

SUMMARY OF THE INVENTION In order to solve such a conventional problem, the present inventors have paid attention to the composition of the polyamide resin layer, and have finally completed the present invention. That is, an object of the present invention is to mainly improve the pinhole resistance, and thereby, a gas barrier property superior to the related art is exhibited.

[0005]

A feature of the present invention is that in a multilayer film having at least two layers including a polyamide resin layer, the polyamide resin layer is made of a crystalline polyamide, an amorphous polyamide, It is a composition layer of a modified ethylene-vinyl acetate copolymer, and is further characterized by a polyamide resin layer / a saponified ethylene-vinyl acetate copolymer layer / a polyamide resin layer provided in this order. In the polyamide-based multilayer film having at least three layers, the polyamide-based resin layer is a composition layer of a crystalline polyamide, an amorphous polyamide and a modified ethylene-vinyl acetate copolymer, The feature is that the polyamide resin layer / meta-xylylenediamine-based polyamide resin layer / polyamide-based resin layer The thus provided in this order, in a multilayer film having at least three layers, wherein the polyamide-based resin layer is crystalline polyamide, amorphous polyamide and a modified ethylene - lies in a composition layer of vinyl acetate copolymer.

[0006]

Next, the means for solving the problems will be described in more detail, and embodiments of the invention will be described. The crystalline polyamide constituting the polyamide resin layer in the present invention is not particularly limited, and examples thereof include 6-nylon, 66-nylon, 12-nylon and copolymers thereof, and the like. Is not particularly limited, and examples thereof include a copolymer of hexamethylenediamine and terephthalic acid and / or isophthalic acid. The modified ethylene-vinyl acetate copolymer is not particularly limited, but a carboxylic acid having a polar group such as maleic acid or fumaric acid or an anhydride thereof is graft-copolymerized into the ethylene-vinyl acetate copolymer. Modified products can be exemplified. Here, the purpose of using the modified ethylene-vinyl acetate copolymer is to impart flexibility to the polyamide-based resin layer and to improve its torsional bending property. It is suitable for food packaging, winter transportation, and the like.

The mixing ratio of the polyamide resin layer is not particularly limited, but is 62 to 97% by weight of a crystalline polyamide, 28 to 1% by weight of an amorphous polyamide and 10 to 2% by weight of a modified ethylene-vinyl acetate copolymer. And about 62 to 93% by weight of a crystalline polyamide, about 28 to 5% by weight of an amorphous polyamide, and about 10 to 2% by weight of a modified ethylene-vinyl acetate copolymer. When the content of the crystalline polyamide is less than 62% by weight, the feeling of the film tends to be hard and the pinhole resistance tends to decrease.
When the content exceeds 7% by weight, the film tends to be broken, so that the film is easily formed, and the pinhole resistance tends to be hardly improved. When the amount of the amorphous polyamide is less than 1% by weight, the film tends to be broken, so that it is difficult to form a film. Hall properties also tend to decrease.
Further, when the content of the modified ethylene-vinyl acetate copolymer is less than 2% by weight, the pinhole resistance tends to be hardly improved, and when it exceeds 10% by weight, the transparency of the film tends to be greatly reduced. In addition to the fact that it may be a problem in practical use in food packaging, etc., the difference in melting point between the crystalline polyamide and the modified ethylene-vinyl acetate copolymer becomes too large, making it difficult to form a uniform melt-extruded film. In some cases, it may cause gel or lumps. However, these ranges are not particularly limited, and if a preferred multilayer film is obtained, even if these ranges are exceeded, no problem is posed.

The saponified ethylene-vinyl acetate copolymer is not particularly limited, but has an ethylene content of 20 to 65.
For example, a xylylenediamine-based polyamide resin may be a polymer synthesized from meta- and / or para-xylylenediamine and a dicarboxylic acid such as adipic acid. Can be illustrated. Further, the polyolefin resin can be exemplified by polyethylene, polypropylene, butene and appropriate copolymers thereof, among which linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-vinyl acetate copolymer and the like are preferable. The modified polyolefin resin is not particularly limited, and the modified polyolefin resin is a modified product obtained by graft-copolymerizing a carboxylic acid having a polar group such as maleic acid or fumaric acid or an anhydride thereof to the polyolefin resin described above. Can be exemplified, but there is no particular limitation. If necessary, appropriate additives such as a thermoplastic resin and an antistatic agent may be added to each of the layers exemplified above. In addition, when the multilayer film is wound up, in order to make the wound state slightly soft and appropriate, polymethyl methacrylate or the like may be added to the polyamide resin layer or the like as an additive.

In the multilayer film of the present invention, the modified ethylene-vinyl acetate copolymer according to the present invention may be added to the above-mentioned xylylenediamine-based polyamide resin layer and the like, whereby the pinhole resistance is further improved. Thus, the interlayer strength is also improved. Of course, such a modified ethylene-vinyl acetate copolymer may be added to the saponified ethylene-vinyl acetate copolymer layer by, for example,
Although the interlayer strength is further improved by adding about 10 to 10% by weight, the modified ethylene-vinyl acetate copolymer is added to the polyamide-based resin layer. Thus, the interlayer strength that can be used is guaranteed.

The multilayer film according to the present invention includes "polyamide resin layer / ethylene-vinyl acetate copolymer saponified layer / polyamide resin layer" and "polyamide resin layer /
"Saponified ethylene-vinyl acetate copolymer layer / polyamide resin layer / modified polyolefin layer / polyolefin resin layer""Polyolefin resin layer / modified polyolefin layer / polyamide resin layer / ethylene-vinyl acetate copolymer saponified layer" / Polyamide resin layer / modified polyolefin layer / polyolefin resin layer "" polyolefin resin layer / modified polyolefin layer / polyamide resin layer / modified polyolefin layer / polyolefin resin layer "and" polyamide resin layer / xylylenediamine type The configuration of "polyamide resin layer / polyamide resin layer" can be exemplified, and there is no particular limitation.

The overall thickness of the multilayer film according to the present invention,
The thickness of each layer is not particularly limited, and the total thickness is usually 4.5 to 130 μm, preferably 10 to 8 μm.
The thickness of each layer is 2 to 50 microns, preferably 3 to 30 microns for the polyamide resin layer.
The saponified ethylene-vinyl acetate copolymer layer is 1 to 20 microns, preferably 2 to 15 microns, the modified polyolefin layer is 0.5 to 20 microns, preferably 1 to 4 microns, and the polyolefin resin layer is 1 to 40 microns. , Preferably 2 to 30 microns. Here, the thickness of the polyamide-based resin layer is desirably 2 μm or more in consideration of film forming properties, and 3 to 30 μm is a desirable value in consideration of physical properties, strength and the like. The thickness of the saponified ethylene-vinyl acetate copolymer layer is 1 to 20 μm, preferably 2 to 1 μm in consideration of oxygen permeability and the like.
5 μm is a desirable value, and the thickness of the modified polyolefin layer is 0.5 to 0.5 in consideration of the interlayer adhesion strength and the like.
20 μm, preferably 1 to 4 μm, is a desirable value, and the thickness of the polyolefin resin layer is 1 to 40 μm, preferably 2 to 30 μm, in consideration of the heat sealing strength and the like. In addition, as for the overall thickness, thin ones are preferred for packaging of electronic components and the like and applications such as balloons, and thick ones are preferred for applications such as sheets.
0 microns, preferably 10 to 80 microns. At this time, regarding the thickness of each layer, of the respective layers exemplified above, even in a multilayer film having any structure not having at least one layer except the polyamide resin layer, the above value is preferable. Of course, it can be exemplified.

The multilayer film of the present invention can be produced basically by a conventional laminating method, and there is no particular limitation. Usually, the multilayer film is formed by coextrusion. Is preferred. At this time, the presence or absence of stretching after film formation is free, but it is preferable to perform stretching if various physical properties are to be improved. The presence or absence of heat treatment after stretching is optional, but if heat shrinkage is required, weak heat treatment or no heat treatment is desirable, and if no shrinkage is required, normal heat treatment is desirable.

The present invention has been described by way of example, and the present invention is not limited to the description.

[0014]

The present invention will be described in more detail with reference to the following examples together with comparative examples. Example 1 Polyamide-based resin (nylon-6, 76.9% by weight, copolymer of hexamethylenediamine with terephthalic acid and isophthalic acid, amorphous nylon, 19.2% by weight, modified ethylene-vinyl acetate Polymer 3.9% by weight) / Saponified ethylene-vinyl acetate copolymer (Ethylene content 32 mol%, Saponified 99%) / Polyamide-based resin (same as above) by co-extrusion in this order. Film formation was performed to obtain a multilayer film. Subsequently, this film was stretched 3.0 times in the machine direction and 4.0 times in the transverse direction by a tenter, and further heat-treated to obtain a 15 micron thick film.
At this time, the thickness of each layer was 6/3/6 microns from the surface.

Example 2 The procedure of Example 1 was repeated, except that the saponified ethylene-vinyl acetate copolymer in Example 1 was replaced with a xylylenediamine-based polyamide resin which was a polymer synthesized from meta-xylylenediamine and adipic acid. In the same manner as in Example 1, a 15-micron thick multilayer film was obtained. At this time, the thickness of each layer was 5/5/5 microns from the surface.

Example 3 The thickness was the same as in Example 1 except that a linear low-density polyethylene resin layer was laminated on the polyamide resin layer on both surfaces of the layer structure of Example 1 via a modified polyethylene resin layer. A 25 micron film multilayer film was obtained. At this time, the thickness of each layer is 3/2/5/3/5/2 in order from the surface.
/ 5 microns.

Example 4 The thickness was the same as in Example 1 except that a linear low-density polyethylene resin layer was laminated via a modified polyethylene resin layer to a polyamide-based resin layer on one surface in the layer structure of Example 1. A 40 micron film multilayer film was obtained. At this time, the thickness of each layer is 6 in order from the surface of the polyamide resin layer.
/ 3/6/2/23 microns.

Example 5 Linear low density polyethylene resin / modified polyethylene resin /
The same polyamide resin / modified polyethylene resin / linear low-density polyethylene resin as in Example 1 was formed by coextrusion in this order to obtain a multilayer film. Subsequently, the film was stretched 3.0 times in the vertical direction and 4.0 times in the horizontal direction by the tenter.
The film was stretched twice and further heat-treated to obtain a micron film having a thickness of 30. At this time, the thickness of each layer is 6/2 /
10/2/10 microns.

Example 6 The same structure as in Example 1 was adopted, except that only the thickness of each layer was 8 in order from the surface.
/ 9/8 microns (thus the overall thickness is about 25 microns).

Comparative Example 1 Polyamide-based resin (nylon-6, 80% by weight and copolymerized amorphous nylon of hexamethylenediamine with terephthalic acid and isophthalic acid, blended composition of 20% by weight) / ethylene-acetic acid A saponified vinyl copolymer (ethylene content 32 mol%, saponification degree 99%) / polyamide resin (same as above) was formed into a film by coextrusion to obtain a multilayer film. Subsequently, this film was stretched 3.0 times in the machine direction and 4.0 times in the transverse direction by a tenter, and further heat-treated to obtain a 15 micron thick film. At this time, the thickness of each layer was 6/3/6 microns from the surface.

Comparative Example 2 The thickness of Comparative Example 1 was the same as that of Comparative Example 1 except that a linear low-density polyethylene resin layer was laminated via a modified polyethylene resin layer on a polyamide resin layer on one surface in the layer structure. A 40 micron multilayer film was obtained. At this time, the thickness of each layer is 6/3/6 in order from the surface of the polyamide resin layer.
/ 2/23 microns.

Comparative Example 3 The same configuration as in Comparative Example 1, except that the thickness of each layer was 8 in order from the surface.
/ 9/8 microns (thus the overall thickness is about 25 microns).

Each of the multilayer films of the embodiments can be subjected to corona discharge treatment on both surfaces or one surface if necessary. Next, Tables 1 and 2 show the physical properties of the above Examples and Comparative Examples. Example 1 in Tables 1 and 2
The multilayer film of Comparative Example 1, and Example 6 in Table 2,
The data of the multilayer film of Comparative Example 3 was obtained by subjecting one surface to a corona discharge treatment.

[Table 1]

[Table 2]

The pinhole resistance in Tables 1 and 2 is measured by a gel botester manufactured by Rikagaku Kogyo Co., Ltd. The measuring method is as follows. And a 15.0 cm bending linear motion at a twisting angle of 440 ° at 10 ° C at 25 ° C.
After repeating 200 times at 00 times and at −20 ° C., the number of pinholes is examined using a permeate. Further, a test repeated 200 times at −20 ° C. was similarly performed.
The measurement was performed at a position of 300 cm ^{2 at} the center of the sample. In the actual packaging test, after wrapping the cake in a film so as to fit it, eight pieces of the cake are put into a rotating drum having a hexagonal prism shape and rotating 50 times per minute, and
After rotating for 30 minutes and 30 minutes, the number of square cakes wrapped in the film with pinholes was checked.
At this time, the pinhole is large enough to allow air to enter and exit, and the pinhole can be visually observed by examining it with a color solution.
In addition, the tactile test is a feeling, that is, the state of hardness and flexibility is checked by hand, ○ is moderate flexibility and good, Δ is slightly hard and hard to say good, × is hard Was determined.

According to Tables 1 and 2, according to the present invention, the pinhole resistance was remarkably improved, the tactile sensation was good, and the flexibility was moderate. It can be seen that the example is inferior in pinhole resistance and is hard even from the tactile sensation.

[0026]

The present invention has a special effect that the pinhole resistance is improved by the above constitution, and it has become possible to provide a polyamide-based multilayer film having improved gas barrier properties. It is widely used for various purposes, and is suitably used for, for example, food packaging. Particularly, it is effective for packaging of angular articles, packaging of frozen foods, transport of packaged articles in winter, and the like.

Continuing from the front page (72) Inventor Shinichi Suzuki 88, Eue Arai, Motomiya-cho, Adachi-gun, Fukushima Prefecture Inside Fukushima Plastics Co., Ltd. In Fukushima Plastics Co., Ltd. (72) Inventor Hiroki Kuryu 88, Uekai Arai, Motomiyacho, Adachi-gun, Fukushima Examiner in Fukushima Plastics Co., Ltd. Hiroaki Hirai (56) References A) JP-A-60-118735 (JP, A) JP-A-3-2260 (JP, A) JP-A-4-4248 (JP, A) JP-A-5-43798 (JP, A) JP-A-55 -74744 (JP, A) JP-A-8-118569 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (5)

(57) [Claims] 1. A polyamide resin layer comprising 62 to 93% by weight of a crystalline polyamide, 28 to 5% by weight of an amorphous polyamide and 10 to 2% by weight of a modified ethylene-vinyl acetate copolymer / ethylene-vinyl acetate copolymer. A saponified polymer layer / a polyamide resin layer composed of 62 to 93% by weight of a crystalline polyamide, 28 to 5% by weight of an amorphous polyamide, and 10 to 2% by weight of a modified ethylene-vinyl acetate copolymer. Polyamide-based multilayer film. 2. A polyamide resin layer / xylylenediamine polyamide comprising 62 to 93% by weight of a crystalline polyamide, 28 to 5% by weight of an amorphous polyamide and 10 to 2% by weight of a modified ethylene-vinyl acetate copolymer. Resin layer / crystalline polyamide 62-93% by weight, amorphous polyamide 2
8 to 5% by weight and modified ethylene-vinyl acetate copolymer 1
A polyamide multilayer film comprising three layers of a polyamide resin layer comprising 0 to 2% by weight. 3. The polyamide-based multilayer film according to claim 1, wherein the crystalline polyamide is 6-nylon. 4. The polyamide-based multilayer film according to claim 1, wherein the amorphous polyamide is a copolymer of hexamethylenediamine and terephthalic acid and / or isophthalic acid. 5. The polyamide-based multilayer film according to claim 1, wherein a polyolefin resin layer is provided on at least one of the polyamide-based resin layers via a modified polyolefin resin layer.