JPH10138411A - Composite film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite film suitable for obtaining a package which has favorable transparency, whose shrinkage at a molded portion at the time of boiling is small, and whose curling and waviness at a surface seal portion with a lid are small. SOLUTION: This composite film comprises a polypropylene resin layer or a nylon 12 resin layer as a first layer, an adherent resin layer as a second layer, a polyamide resin layer as a third layer, an adherent resin layer as a fourth layer, a low-density polyethylene resin layer or an ethylene vinyl acetate resin layer having a vinyl acetate content of at most 5mol%, or a layer of a blended article whose principal raw materials are composed of these polyethylene resin and ethylene vinyl acetate resin, as a fifth layer, and a straight-chain, low-density polyethylene resin layer whose thickness is 3-15μm, and whose Vicat softening point is in the range of 105-145 deg.C according to JIS K7206, or a polypropylene resin layer, as a sixth layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite film which can be used mainly as a bottom material for deep drawing packaging of foods, has good transparency, has a small shrinkage of a molded portion at the time of boiling, and has a sealing portion with a lid material. The present invention relates to a composite film suitable for obtaining a package having less curl and waving.

[0002]

2. Description of the Related Art Conventionally, as a bottom material for deep drawing packaging for boiling, a laminate of a nylon resin and a linear low-density polyethylene resin layer or a laminate of a nylon resin layer and a polypropylene resin layer has been used. I have.

The high gas barrier type is a laminate comprising a nylon resin layer / a saponified ethylene vinyl acetate resin layer / a linear low density polyethylene resin layer, a polypropylene resin layer / an ethylene vinyl acetate copolymer. Of a laminate consisting of a saponified resin layer / nylon resin layer / linear low-density polyethylene resin layer and a laminated body of a saponified ethylene vinyl acetate copolymer resin layer / nylon resin layer / ethylene vinyl acetate copolymer resin layer Laminated products in which a polypropylene film is dry-laminated on the saponified ethylene vinyl acetate copolymer resin layer side are used.

However, in the case where the linear low-density polyethylene resin is used for the heat-sealing layer, the film is whitened due to crystallization of the linear low-density polyethylene resin during heat sealing, and the transparency of the sealing portion is remarkably reduced. There was a disadvantage that it would.

[0005] In addition, since the linear low-density polyethylene resin itself is a resin that is very easily shrunk, and usually deep drawing is performed at a temperature equal to or lower than the melting point of the linear low-density polyethylene resin, the sealing of the package with the lid material sealed is performed. There is a disadvantage that curling and waving of the part cannot be prevented.

On the other hand, in the case where the ethylene-vinyl acetate copolymer resin is used for the heat seal layer, if the forming temperature is high at the time of deep drawing, the heat seal layer is melted and taken off by the hot plate heated from the seal portion side. For this reason, low-temperature molding must be performed, so that high-melting-point resin such as nylon resin has strong molding distortion during low-temperature molding, and has a disadvantage that it is easily shrunk during boiling. Further, in the configuration of the nylon resin layer and the polypropylene resin layer, the molding temperature is increased and the shrinkage is suppressed, but there is a problem in softness and pinhole resistance.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel composite film which solves the above-mentioned problems of the prior art.

[0008]

The above object is achieved by the following means.

That is, according to the present invention, the first layer comprises a polypropylene resin layer or a 12 nylon resin layer, the second layer comprises an adhesive resin layer, the third layer comprises a polyamide resin layer, and the fourth layer comprises an adhesive resin layer. Five layers are a low-density polyethylene resin layer, an ethylene vinyl acetate resin layer having a vinyl acetate content of 5 mol% or less, or a blend layer containing them as a main material, and a sixth layer is 3 to 15 μm thick and is Vicat softened according to JIS K7206. The present invention proposes a composite film comprising a linear low-density polyethylene resin layer or a polypropylene resin layer having a temperature in the range of 105 ° C. to 145 ° C., and the present invention provides a polyamide resin layer of the composite film. Characterized in that a saponified ethylene-vinyl acetate copolymer resin layer is provided adjacent to or via an adhesive resin layer. It is intended to propose. Further, the present invention includes that the first polypropylene resin layer is dry-laminated on the surface of a co-extruded composite film obtained by laminating by a co-extrusion method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail.

In the composite film according to the first aspect of the present invention, the first layer is a polypropylene resin layer (hereinafter referred to as PP) or a 12 nylon resin layer (hereinafter referred to as 12 Ny), and the thickness thereof is in the range of 5 to 70 μm. preferable. The second layer is an adhesive resin layer, and the third layer is a polyamide resin layer (hereinafter N
y), the fourth layer is an adhesive resin layer, and the fifth layer is a low-density polyethylene resin layer (hereinafter referred to as LDPE) or an ethylene vinyl acetate resin layer having a vinyl acetate content of 5 mol% or less (hereinafter referred to as EVA) or a combination thereof. This is a layer of a blend as a raw material, and the sixth sealing layer has a thickness of 3 to 1
Vicat softening point according to JIS K7206 is 10 at 5 μm
A composite film comprising a linear low-density polyethylene resin layer (hereinafter referred to as LLDPE) or PP in the range of 5 ° C to 145 ° C. If the thickness of the sealing layer is less than 3 μm, it tends to be formed on a hot plate during heat sealing, and if it exceeds 15 μm, there is a problem that whitening due to crystallization during sealing cannot be suppressed low. Examples of the adhesive resin for the second and fourth layers include an acid-modified polyolefin resin and the like.
The range of μm is preferred. As the Ny of the third layer, 6 nylon, 6-66 nylon, 12 nylon, 6-12 nylon and the like can be mentioned, but 6 nylon is more preferable because the shrinkage stress of the molded product is small and the shrinkage during boiling is suppressed more. .

The thickness of Ny is preferably in the range of 5 to 70 μm. The thickness of the fifth layer made of LDPE or EVA or a blend containing them as a main raw material is 15 to 15
A range of 0 μm is preferred. EVA has a vinyl acetate content of 0
The range of about 5 mol% is preferred. If the content exceeds 5 mol%, there is a problem that the shrinkage rate increases and shrinkage easily occurs during boiling.

The ratio of the blend mainly composed of LDPE and EVA is not particularly limited, and may be determined in consideration of shrinkage.

It is important that the sixth sealing layer has a Vicat softening point in the range of 105 ° C. to 145 ° C. according to JIS K7206.

If the Vicat softening point is lower than 105 ° C., the molding distortion of Ny and other layers cannot be suppressed small, and the shrinkage of the molded portion during boiling cannot be reduced. It is not preferable because the sealing property deteriorates.

As the PP for the sixth sealing layer, it is preferable to use a random copolymerization type PP because the molding temperature can be increased more. However, if the interlayer adhesion strength with the adjacent fifth layer becomes insufficient, It is preferable to add a low-crystalline resin of a copolymer of polyethylene and α-olefin having a density of 0.9 or less to the resin of the fifth layer because the interlayer strength can be improved.

As the PP of the first outer layer, a homopolymer is preferable because it has a small shrinkage stress and is good, but a random copolymer type PP having good gloss and transparency can be used. In that case, the larger the thickness of the PP, the smaller the shrinkage, which is better.

The composite film according to claim 2 is provided with a saponified ethylene vinyl acetate copolymer resin layer (hereinafter referred to as EVOH) adjacent to Ny or with an adhesive resin layer interposed therebetween in order to impart gas barrier properties. It is possible to store foods and the like for a long time. Further, the composite film of the third aspect is obtained by laminating the above-mentioned first layer of PP on a co-extruded composite film of another layer by dry lamination, and has an advantage that shrinkage during boiling is easily reduced.

[0019]

The present invention will be described below in more detail with reference to examples.

Example 1 A composite film composed of the following six layers was co-extruded to obtain a co-extruded composite film. PP (thickness 40 μm) / adhesive resin (10 μm) / Ny (thickness 30 μm) / adhesive resin (thickness 10 μm) / LDPE (thickness 50 μm) / LLD
PE (thickness: 10 μm) The PP of the outer layer was a random copolymer with ethylene, and the Vicat softening point of LLDPE was 110 ° C. The obtained co-extruded composite film was subjected to molding at the maximum molding temperature shown in Table 1 (the maximum temperature at which the film was not removed from the hot plate), and the deep drawing packaging machine F manufactured by Omori Machinery Co., Ltd.
After heating and molding for 1.5 seconds using V6300 and filling the obtained bottom material with the contents, the lid material was face-sealed to obtain a package, and the package was boiled at 98 ° C for 20 minutes. Then, the shrinkage state at the time of boiling, the transparency of the face seal portion and the pinhole resistance were evaluated. Table 1 shows the results.

The lid was a dry laminate of stretched Ny and EVA.

Evaluation method-Shrinking state at the time of boiling Boiled with no tendency to undulate at the time of boiling, 〇 when shrunk and slightly wavy, and X when shrunk and undulated. -Transparency of the face seal portion The heat seal portion having no whitening was marked with 〇, the one with little whitening was marked with △, and the whitened portion was marked with x. -Pinhole resistance The pinholes with no pinholes due to boiling were marked with "〇" and those with pinholes were marked with "x".

Example 2 A composite film having the following seven layers was co-extruded to obtain a co-extruded composite film.

PP (thickness: 40 μm) / adhesive resin (thickness: 1)
0 μm) / Ny (thickness 30 μm) / EVOH (thickness 10
μm) / adhesive resin (thickness 10 μm) / LDPE (thickness 4
0 μm) / LLDPE (thickness: 10 μm) The same PP and LLDPE as in Example 1 were used. The obtained co-extruded composite film was evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 3 A composite film having the following five layers was co-extruded to obtain a co-extruded composite film.

EVOH (thickness 20 μm) / Ny (thickness 2
0 μm) / adhesive resin (thickness 10 μm) / EVA (thickness 4
0 μm) / LLDPE (thickness: 10 μm) PP having a thickness of 50 μm was dry-laminated on the EVOH side of the co-extruded composite film to obtain a six-layer composite film.

The same PP and LLDPE as those used in Example 1 were used.

The obtained composite film was evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 4 A composite film having the following six layers was co-extruded to obtain a co-extruded composite film.

PP ₁ (thickness 40 μm) / adhesive resin (thickness 10 μm) / Ny (thickness 30 μm) / adhesive resin (thickness 1
0 μm) / LL (thickness 50 μm) / PP ₂ (thickness 10 μm)
m) In addition, the PP random copolymer of ethylene as PP _2, using PP homopolymer as PP _1.

The obtained co-extruded composite film was evaluated in the same manner as in Example 1. Table 1 shows the results.

Example 5 A composite film having the following seven layers was co-extruded to obtain a composite film of the present invention.

12 Ny (thickness 10 μm) / adhesive resin (thickness 10 μm) / Ny (thickness 30 μm) / EVOH (thickness 10 μm) / adhesive resin (thickness 10 μm) / EVA (thickness 70 μm) / LLDPE (thickness 10 μm) The same one as in Example 1 was used. E
VA has a vinyl acetate content of 3 mol%.

The obtained co-extruded composite film was evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 A composite film having the following five layers was co-extruded to obtain a co-extruded composite film.

PP (thickness: 40 μm) / adhesive resin (thickness: 1)
0 μm) / Ny (thickness 30 μm) / adhesive resin (thickness 10
μm) / LLDPE (thickness: 60 μm) The same LLDPE as in Example 1 was used.

The obtained composite film was evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 A composite film having the following six layers was coextruded to obtain a coextruded composite film.

PP (thickness: 40 μm) / adhesive resin (thickness: 1)
0 μm) / Ny (thickness 30 μm) / adhesive resin (thickness 10
μm) / LDPE (thickness: 40 μm) / LLDPE (thickness: 20 μm) The same LLDPE as in Example 1 was used.

The obtained composite film was evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 3 A composite film having the following six layers was co-extruded to obtain a composite film.

PP (thickness: 40 μm) / adhesive resin (thickness: 1)
0 μm) / Ny (thickness 30 μm) / adhesive resin (thickness 10
μm) / LDPE (thickness 50 μm) / LLDPE (thickness 10 μm) The LLDPE used had a Vicat softening point of 100 ° C.

The obtained composite film was evaluated in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 4 A composite film having the following five layers was coextruded to obtain a composite film.

EVOH (thickness 20 μm) / Ny (thickness 2
0 μm) / adhesive resin (thickness 10 μm) / EVA (thickness 4
0 μm) / LLDPE (thickness: 10 μm) The same LLDPE as in Comparative Example 3 was used. E
VA has a vinyl acetate content of 3 mol%.

A 50 μm-thick PP was dry-laminated on the EVOH side of the co-extruded composite film to obtain a composite film.

The obtained composite film was evaluated in the same manner as in Example 1. Table 1 shows the results. Comparative Example 5 A composite film having the following three layers was co-extruded to obtain a composite film.

Ny (thickness: 50 μm) / adhesive resin (thickness: 1)
0 μm) / PP (thickness: 90 μm) The obtained composite film was evaluated in the same manner as in Example 1. Table 1 shows the results.

From Table 1, it can be seen that Examples 1 to 5 which are the packages using the composite film of the present invention do not shrink when boiled, have good transparency of the face seal portion, and have a pinhole resistance. It can also be seen that it is good. On the other hand, in Comparative Examples 1 and 2 in which the thickness of the seal layer is too thick, the transparency of the face seal portion is inferior, and in Comparative Examples 3 and 4 in which the Vicat softening point of the LLDPE of the seal layer is low, shrinkage occurs at the time of boiling and undulation occurs. Occurred and found to be problematic. Further, in Comparative Example 5, although there is no shrinkage at the time of boiling, it is found that the whitening of the seal portion and the pinhole resistance are inferior.

[0050]

[Table 1]

[0051]

According to the present invention, there is provided a composite film which is suitable for obtaining a package having good transparency, little shrinkage of the molded part at the time of boiling, and little curling or waving of the sealing part with the lid material. it can.

Claims (3)

[Claims] A first layer comprising a polypropylene resin layer or a 12 nylon resin layer; a second layer comprising an adhesive resin layer; a third layer comprising a polyamide resin layer; a fourth layer comprising an adhesive resin layer;
The layer is a low density polyethylene resin layer or vinyl acetate content 5
Mole% or less of an ethylene vinyl acetate resin layer or a blend layer containing them as a main raw material, wherein the sixth layer has a thickness of 3 to 15 μm and a linear linear shape having a Vicat softening point according to JIS K7206 of 105 ° C. to 145 ° C. A composite film comprising a low-density polyethylene resin layer or a polypropylene resin layer. 2. A composite film according to claim 1, wherein a saponified ethylene vinyl acetate copolymer resin layer is provided adjacent to the polyamide resin layer of the composite film or via an adhesive resin layer. 3. The composite film according to claim 1, wherein the first polypropylene resin layer is dry-laminated on the surface of a co-extruded composite film obtained by laminating by a co-extrusion method.