JP3028341B2 - Multilayer film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flat multilayer film suitable as a packaging film.

<Conventional technology> Ethylene content 20-65 mol%, saponification degree 90%
Various multilayer films containing the above-mentioned saponified ethylene-vinyl acetate copolymer (hereinafter referred to as saponified) layers are scattered, but these are usually formed into a tube by an inflation method, and are flattened by a T-die or the like. Those extruded in a shape were out of scope. The reason for this is that the saponified product is usually difficult to be stretched, and for this reason, stretching of a flat film by the T-die method was not common. On the other hand, in the film formation by the inflation method, there is another problem that the deviation in wall thickness is inadequate by all means, and the thickness varies widely.

<Means for Solving the Problems> In such a situation, the present inventors will pursue a flat multilayer film including a saponified layer, and the saponified material is sandwiched between the polyamide-based resin layers. Focusing on the fact that the saponified material itself is also easily stretched, a mixed resin of 50 to 95% by weight of a nylon 6 resin and 50 to 5% by weight of an amorphous polyamide resin is further added to at least one of the polyamide resins. Focusing on the fact that it becomes easier to stretch by using,
Finally, the present invention has been reached. That is, the present invention improves the stretchability of the saponified product by taking the above basic constitution,
As a result, the thickness deviation of the multilayer film itself and the variation in thickness are to be improved.

The present invention provides the following multilayer film.

(1) It has at least a three-layer structure comprising a polyamide resin layer, an ethylene-vinyl acetate copolymer saponified layer having an ethylene content of 20 to 65 mol% and a saponification degree of 90% or more, and a polyamide resin layer. At least one of the polyamide resin layers in a multilayer film formed into a flat shape and sequentially biaxially stretched is made of nylon 6 resin.
It is a mixed resin layer of 50 to 95% by weight of a mixture containing 10 to 95 parts by weight of an aromatic polyamide resin and 50 to 5% by weight of an amorphous polyamide resin per 100 parts by weight. Multilayer film.

(2) The oxygen permeability of the multilayer film is 20 cc / m ² , 24H, at
m (20 ° C., 65% RH) or less.

(3) Polyamide resin layer (A), ethylene content 20 to
65 mol%, saponification degree 90% or more ethylene-vinyl acetate copolymer saponified layer (D), polyamide resin layer (A),
Mixture layer of modified linear low-density polyethylene and linear low-density polyethylene (B) and linear low-density polyethylene layer (C)
Has a five-layer structure laminated in this order, and at least one of the polyamide-based resin layers in the multilayer film formed into a flat film and sequentially biaxially stretched has a nylon 6 resin content of 50 to 95% by weight. Characterized in that it is a mixed resin layer comprising: a mixed resin layer of at least 50% by weight of an amorphous polyamide resin.

(4) Mixed resin layer of 50 to 95% by weight of nylon 6 resin and 50 to 5% by weight of amorphous polyamide resin, ethylene content 20
~ 65 mol%, saponified ethylene-vinyl acetate copolymer layer having a degree of saponification of 90% or more, and nylon 6 resin 50 ~ 95 wt%
And a mixed resin layer of 50 to 5% by weight of an amorphous polyamide resin having a three-layer structure laminated in this order, formed into a flat film, and successively biaxially stretched. A multilayer film characterized by being heat-treated.

Next, means for solving the problems in the present invention will be described in detail.

The polyamide resin according to the present invention, nylon 6, nylon 66, nylon 610, nylon 6 in addition to nylon 6-66 copolymer, nylon 6-610 copolymer and other copolyamide, aromatic polyamide resin, An amorphous polyamide resin or a mixture thereof can be exemplified, and there is no particular limitation. Here, the nylon 6 resin is a well-known resin obtained by ring-opening polymerization of ε-caprolactam. The aromatic polyamide resin is not particularly limited as long as it has a structure having an aromatic ring in a main chain and / or a side chain, but it is generally preferable to use a resin having crystallinity. Xylylenediamine and carbon 4 ~
A polyxylylene-based polymer polycondensed from about 12 dicarboxylic acids can be exemplified. Among them, polymethaxylylenediadipamide synthesized from metaxylylenediamine and adipic acid can be exemplified as a suitable example, and such a polymer has properties such as gas barrier properties, low water absorption, and low moisture permeability. I have.

At this time, Ninelon 6 resin and aromatic polyamide resin may be blended and used.
Aromatic polyamide resin 10-95 based on 100 parts by weight of resin
It is desirably about part by weight, but is not limited to this range and may be appropriately blended and used.

Further, the amorphous polyamide resin is generally referred to as having no crystallinity or having poor crystallinity, and is not particularly limited, but generally has an aromatic ring in a main chain and / or a side chain. Semi-aromatic polyamides can be exemplified. Specific examples thereof include a polymer of a dicarboxylic acid such as terephthalic acid and isophthalic acid and a diamine such as hexamethylenediamine, and a terpolymer, but are not particularly limited. Such amorphous polyamide resin is excellent in gas barrier property when high humidity, for example, certain amorphous polyamide has an oxygen permeability of 0% RH of 25μm film ^{39cc / m 2 .24hr (23 ℃} ) , 100% R
Value of about ^{17cc / m 2 .24hr (23 ℃} ) in H can be ensured.

The multilayer film according to the present invention comprises at least a polyamide resin layer, an ethylene content of 20 to 65 mol%, a saponified ethylene-vinyl acetate copolymer having a saponification degree of 90% or more, and a polyamide resin layer. It has a three-layer configuration,
And at least one layer thereof is a polyamide resin having a specific configuration, and the total thickness of the multilayer film is not particularly limited, but is usually 8 to 100 μm, and preferably 1 to 100 μm.
For example, about 0 to 60 μm can be exemplified. It should be noted that any other suitable third component may be added to the above-mentioned polyamide resin or saponified product.

At this time, examples of the configuration of the multilayer film include three or more layers, preferably about 3 to 7 layers. When forming a multilayer, the resin used as another layer is not particularly limited, and various resin layers may be appropriately combined and used. An example of a commonly used resin is an olefin polymer. Examples of such olefin polymers include, for example, olefin homopolymers, mutual copolymers, other copolymerizable monomers such as copolymers with other vinyl monomers, and modified copolymers thereof. it can. Specifically, for example, polyethylene of various densities ranging from low density to high density (including linear low density polyethylene), polypropylene,
Examples thereof include polybutene, their mutual copolymers, ionomer resins, ethylene-acrylic acid copolymers, ethylene-vinyl acetate copolymers, and modified polyolefin resins. Here, as the modified polyolefin-based resin, for example, maleic acid,
Fumaric acid, acrylic acid, and other suitable unsaturated carboxylic acids or derivatives thereof such as acid anhydrides, esters or metal salts thereof can be exemplified as modified polymers obtained by copolymerization, for example, graft copolymerization. Alone or other components, for example, a mixture with another olefin polymer, etc. are also included in the modified polyolefin resin. Such a modified polyolefin-based resin can be suitably used as an adhesive resin when forming a multilayer, and other such adhesive resins include ionomer resins, ethylene-ethyl acrylate resins, ethylene-vinyl alcohol copolymers, and the like. And there is no particular limitation.

Particularly preferred among the olefin polymers described above are low-density polyethylene, linear low-density polyethylene,
Examples include ionomer resins, modified polyolefin resins, and ethylene-vinyl acetate copolymers. The above olefin polymers can be used alone or as a mixture of two or more. Such a layer made of an olefin polymer can be conveniently used as a heat seal layer if necessary.

Further, a gas barrier resin other than a saponified material can also be exemplified as one of the resins used for the other layers. Examples of the resin having such a gas barrier property include a polyacrylonitrile resin, a polyvinylidene chloride resin, and a polyester resin. Etc. can also be exemplified.

It is clear from the above description that various combinations can be adopted as the resin of each layer constituting the multilayer film,
The following is a more preferred combination example. In the following, each alphabet symbol indicates the following resin.

A: Polyamide resin B: Modified polyolefin resin C: Olefin polymer D: Saponified product A / D / A, A / D / A / B / C, C / B / A / D / A / B / C , B / A / D / A / B / C, A / D / B / A / B / C In the above-mentioned one multilayer film, even if a modified polyolefin-based resin in which B is different from each other is used. It is needless to say that the same type may be used, and that C may be a different type of olefin polymer or the same type.

In the above-mentioned combinations, those in which B is replaced with an ionomer resin can be used.

The thickness of the polyamide-based resin layer according to the present invention is usually 2 to 35 µm, preferably 3 to 20 µm per layer, and the thickness of the saponified material is usually 1 to 30 µm, preferably 2 to 20 µm. The thickness of the adhesive resin layer and the thickness of the olefin-based polymer layer added according to the above conditions may be appropriately determined. Of course, these descriptions are not particularly limited, and any values may be used as needed. In addition, the oxygen permeability of the multilayer film is 20 cc / m ² , 24H, atm (20
° C, 65% RH) or less, preferably 10 cc / m ² , 24H, atm (20
(° C., 65% RH) or less, but of course there is no particular limitation on these values, and any value may be used as needed.

Furthermore, even if the multilayer film of the present invention has heat shrinkability, the heat shrinkability is poor, or it may not substantially have heat shrinkage. The heat shrinkage and the heat shrinkage are poor, or the heat shrinkage of the multilayer film having substantially no heat shrinkage may be appropriately determined and is not particularly limited. In the case of having a 90 ° C. hot water bath for 30 seconds, the heat shrinkage in the vertical direction is 5 to 50%, preferably 10 to 30%,
50%, preferably about 10 to 30%, and if there is substantially no heat shrinkage or poor heat shrinkage, 90 ° C hot water bath
The heat shrinkage in 30 seconds is less than 5% in the longitudinal direction, preferably 0 to
3%, less than 5% in the horizontal direction, preferably about 0 to 3%.

The present invention is formed into a flat film and is successively biaxially stretched. The present invention
Usually, it is sufficient to form a co-extrusion film in a flat shape from a T die.
The film formation is not particularly limited, but is generally performed by extrusion casting on a cooled chill roll, and the present invention can be achieved by stretching the film thus formed continuously or in another step. The stretching can be exemplified by a biaxial stretching method. In general, necessary stretching is performed by performing longitudinal stretching by a roll stretching machine and transverse stretching by a tenter stretching machine, but the stretching means is not particularly limited. The stretching conditions are not particularly limited depending on the characteristics of the polymer used for the multilayer film, but are usually 2 to 5 times in the machine direction and 2 to 6 times in the transverse direction (the stretching order may be reversed in the machine direction). Biaxial stretching can be exemplified, and the stretching temperature in the machine direction is
Examples thereof include a range of 60 to 120 ° C, preferably 70 to 100 ° C, and a transverse stretching temperature of 70 to 180 ° C, preferably 100 to 160 ° C.

After the stretching, heat treatment is performed as necessary. However, when a high degree of heat shrinkability is required, the heat treatment may not be performed.
The heat treatment may be performed by any means, but is generally performed in a continuous process following the transverse stretching by a tenter stretching machine. When the heat treatment is performed, the width may be reduced (relaxed) to 20% or less, preferably 3 to 10% in the width direction. However, the width may be set to be equal to the width in the transverse stretching. The width may be set to be equal to or larger than the width at the time of stretching. The heat treatment temperature is different in the case of obtaining a multilayer film having heat shrinkage and in the case of obtaining a multilayer film having poor heat shrinkage or having substantially no heat shrinkage. Often performed in the low temperature range. For example, in order to obtain a heat-shrinkable multilayer film, the heat treatment is carried out by a tenter stretching machine at a temperature of less than 150 ° C, preferably 80 to 130 ° C, and if necessary within 20% in the width direction, preferably 3 to 10%.
It is also possible to do it with the size reduced in the range of 10%,
In order to obtain a multilayer film having no heat shrinkage or poor heat shrinkage, heat treatment is performed at 150 ° C with a tenter stretching machine.
Above, preferably 180 to 250 ° C, more preferably 210 to 250
It is also possible to reduce the temperature in the range of 20 ° C. and, if necessary, within 20% in the width direction, preferably in the range of 3 to 10%. However, these values are merely examples and are particularly limited. Not something. When obtaining a film having heat shrinkability, the heat treatment is performed for the purpose of preventing spontaneous shrinkage, and the purpose of the heat treatment performed when obtaining a film having poor heat shrinkage or substantially no heat shrinkage ( The purpose may be slightly different from the above (to suppress the heat shrinkability).

Uses of the multilayer film according to the present invention include meat, processed meat, retort food, water food, microwave oven products, food packaging materials such as frozen foods, and other various packaging materials, and deep drawing containers and the like. It is also possible to process it, and its use is not particularly limited, and can be applied to all fields.

Examples of the packaging form when used as a packaging material include overlap packaging, sleeve packaging, and the like.Also, it may be formed into a bag shape by heat sealing, and there is no particular limitation. In such a case, it can be used as a packaging material only by cutting to a predetermined size, and such a usage is also possible, and there is no particular limitation.

While the above has illustrated preferred embodiments of the present invention,
The present invention can take any embodiment without being limited by such description.

<Example 1> 90% by weight of nylon 6 resin and amorphous polyamide resin 10
% By weight of a polyamide resin layer A, an ethylene content of 44 mol%, and a saponified ethylene-vinyl acetate copolymer layer having a degree of saponification of 99% or more (melting point: 164 ° C.) in the order of A / D / A. Co-extrusion film is formed on a chill roll that circulates cooling water from a T die to obtain a flat three-layer film.
Thereafter, the film is stretched three times in a longitudinal direction by a roll stretching machine at 80 ° C., and further horizontally stretched 3.5 times by a tenter stretching machine in a 140 ° C. atmosphere. Heat set in. The thickness of the film thus obtained is A, D, A = 5, 5, 5 μ, and the heat shrinkage at 90 ° C. for 30 seconds in hot water is 15% in the vertical direction and 20% in the horizontal direction.
Met. Such a film had good thickness deviation accuracy and little thickness variation. The oxygen permeability is 7cc / m ² ,
It was 24H, atm (20 ° C, 65% RH).

<Comparative Example 1> A heat-shrinkable multilayer film was obtained in the same manner as in Example 1 except that a polyamide-based polymer layer consisting of only nylon 6 was used in Example 1, and the film was stretched under the same conditions. Many tears occurred during tenter stretching, and stable stretching was not possible.

<Example 2> Using the same resin as in Example 1, a co-extrusion film was formed on a chill roll that circulates cooling water from a T die so as to be in the order of A / D / A to obtain a flat three-layer film. 80
The film is longitudinally stretched 3 times by a roll stretching machine at ℃, and further stretched 3.5 times by a tenter stretching machine in an atmosphere at 140 ° C.
Subsequently, the width was reduced by about 4% by the tenter while 21
Heat fixing was performed in an atmosphere at 0 ° C. The thicknesses of the films thus obtained were A, D, A = 5, 5, 5 μ and 5, 10, 5 μ, and the thermal shrinkage at 90 ° C. for 30 seconds in hot water was 1% in the vertical direction and 1% in the horizontal direction. %Met. Such a film had good thickness deviation accuracy and little thickness variation. The oxygen permeability is
7cc / m ² , 24H, atm (20 ° C, 65% RH) and 4cc / m ² , 24
H, atm (20 ° C., 65% RH).

<Example 3> A / D / A / B / C (where B is a modified linear low-density polyethylene resin and C is a linear low-density polyethylene resin using the same resin as in Example 1) ) A heat-shrinkable multilayer film was obtained in the same manner as in Example 1 except that the film was changed to a five-layer film as described in (1). (No. 1 above) A multilayer film having poor heat shrinkage was obtained in the same manner as in Example 1 except that the heat treatment was performed in an atmosphere of 210 ° C. as No. 2.

In Experiments Nos. 3 to 6 below, films were formed in the same manner, and the materials used, thickness, stretching temperature, and heat treatment temperature were set as shown in Table 1.

In this case, LL is linear low-density polyethylene LL ₁ is high-melting linear low-density polyethylene LL ₂ is low-melting linear low-density polyethylene Modified LL is a mixture of modified linear low-density polyethylene and linear low-density polyethylene PA is nylon Mixture of 6 and amorphous polyamide resin (compounding ratio of Example 1) PP is polypropylene Modified PP is a mixture of modified polypropylene and polypropylene PA ₁ is 100 parts by weight of nylon 6 resin and 50 parts by weight of aromatic polyamide resin mixture PA ₂ of amorphous polyamide resin by weight 15 parts by weight (9.1 wt%) is nylon 6-nylon 66 copolymer.

As specific examples of the features and preferred uses of the multilayer film thus obtained, No. 1 is preferably used as a heat shrink wrapping material for boiled food, processed meat casing, meat, general food, and the like. , No. 2 has the same characteristics as No. 1 and is used favorably as a packaging material for No. 1 non-shrinkage field, other frozen foods, various foods, etc., and No. 3 seals No. 4 has improved heat resistance, while No. 5 has improved heat resistance, and is suitable as a packaging material for retort foods. 6 is particularly suitable as a packaging material for foods and the like that require a high degree of gas barrier properties. The applications described above are merely examples of preferable ones, and the present embodiment is not limited to the description.

<Effects of the Invention> The present invention uses a specific polyamide-based polymer layer in at least one layer of a multilayer film, so that it can be stretched in a flat shape with good thermal stretchability and can be stretched at a higher speed. There are advantages. In addition, the film thus obtained is excellent in uneven thickness accuracy and has little unevenness in thickness, so that it is suitably used as various packaging materials, and great expectations are placed on its future application.

For example, since a multilayer film having heat shrinkability can be provided, it is excellent for use in various shrink packaging, and when the object to be packaged is meat, for example, because of its heat shrinkability, it is suitable for meat. It is also packaged in close contact, and has an effect of suppressing generation of meat juice and the like over time.

Further, for example, it is possible to provide a multilayer film having substantially no heat shrinkage or poor heat shrinkage, and it is also possible to provide a multilayer film having a low oxygen permeability, so that various packaging materials and other fields can be provided. It has advantages such as adaptability, and is expected to be widely used in the future.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B29C 61/02

Claims (4)

(57) [Claims] 1. A polyamide resin layer having an ethylene content of 20 to 20.
It has at least a three-layer structure comprising a saponified ethylene-vinyl acetate copolymer layer having a degree of saponification of at least 65 mol% and a degree of saponification of 90% or more, and is formed into a flat film and successively biaxially stretched. At least one of the polyamide-based resin layers in the multilayer film is composed of aromatic polyamide resin 10 to 9 with respect to 100 parts by weight of nylon 6 resin.
A multilayer film comprising a mixed resin layer of 50 to 95% by weight of a mixture containing 5 parts by weight and 50 to 5% by weight of an amorphous polyamide resin. 2. The multilayer film has an oxygen permeability of 20 cc / m ² , 2
The multilayer film according to claim 1, which is 4H, atm (20 ° C, 65% RH) or less. 3. A polyamide resin layer (A), a saponified ethylene-vinyl acetate copolymer layer (D) having an ethylene content of 20 to 65 mol% and a saponification degree of 90% or more, a polyamide resin layer (A), The modified linear low-density polyethylene and the linear low-density polyethylene mixture layer (B) and the linear low-density polyethylene layer (C) have a five-layer structure laminated in this order, are formed into a flat film, and At least one of the polyamide-based resin layers in the multilayer film that is successively biaxially stretched is a mixed resin layer of 50 to 95% by weight of a nylon 6 resin and 50 to 5% by weight of an amorphous polyamide resin. A multilayer film. 4. A mixed resin layer of 50 to 95% by weight of a nylon 6 resin and 50 to 5% by weight of an amorphous polyamide resin, ethylene-vinyl acetate having an ethylene content of 20 to 65% by mole and a saponification degree of 90% or more. Saponified copolymer layer and nylon 6 resin 50-95
A mixed resin layer of 50% by weight and 50 to 5% by weight of an amorphous polyamide resin has a three-layer structure laminated in this order.
A multilayer film characterized by being heat-treated at 50 ° C.