JPH0459353A - Laminate wrapping film - Google Patents

Abstract

PURPOSE:To improve gas-barrier and retort resistant character by providing the laminate structure made up of a surface layer consisting of stretched polyester film, an intermediate layer consisting of the biaxially stretched film formed by building up in layers polyamide, the saponification product of ethylene-vinyl acetate copolymer and polyamide in that order and a sealant layer consisting of undrawn polypropylene film. CONSTITUTION:The subject film consists of a surface layer, an intermediate layer and a sealant layer and the surface layer is formed of stretched polyester film. It is desirable to use, as the stretched polyester film, biaxially stretched polyethylene terephthalate or polyethylene naphthalate, preferably with the thickness ranging from 7 to 25mum. The intermediate layer consists of the biaxially stretched film formed by building up in layers polyamide, the saponification product of ethylene-vinyl acetate copolymer (EVOH) and polyamide in that order. With respect to the thickness of each layer, it is desirable to form 3-10mum polyamide layer, 3-20mum EVOH later and 3-10mum polyamide layer, with the total layer thickness amounting to 10-30mum. The sealant layer consists of undrawn polypropylene film, preferably with the thickness ranging from 20 to 60mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laminated film for packaging, and more specifically, a packaging film that has a specific laminated structure and has excellent gas barrier properties and retort resistance. The present invention relates to a laminated film for use in industrial applications.

[Conventional technology]

Conventionally, various packaging films have been proposed and put into practical use.

Many proposals have also been made regarding packaging films with gas barrier properties.

For example, a low-density polyethylene film is laminated on one side of a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) film, and a film of polypropylene, nylon, polyester, etc. is laminated on the other side. proposed to improve the drawbacks of EVOH such as drop strength, thermoformability, and moisture resistance while maintaining the gas barrier properties of EVOH (Japanese Patent Publication No. 49-6192), by mixing polyamide with EVOH, Proposal to improve the drawbacks of impact resistance and stretchability (Special Publication No. 44-2427)
7), polyamide to EVOH for the same purpose.
Proposal to mix polyether block copolymers (JP-A-60-139733, JP-A-60-161453)
Publication No.)) etc. have been made.

The above-mentioned gas barrier packaging film is suitable for packaging contents that do not like deterioration due to oxygen, such as foods and medicines.

By the way, particularly in the packaging of foods and medicines, retort treatment may be performed after packaging for the purpose of heat sterilization.

Therefore, packaging films for such uses are required to have pinhole resistance and retort resistance in addition to the above-mentioned gas barrier properties.

[Problem to be solved by the invention]

However, all of the above proposals relate to improving the mechanical properties and formability of EVOH while maintaining its gas barrier properties. No film proposals have been made.

An object of the present invention is to provide a laminated film for packaging that has excellent gas barrier properties and retort resistance.

[Means to solve the problem]

As a result of various studies, the present inventors have found that the above object can be easily achieved by a laminated film having a specific laminated structure, and have completed the present invention.

That is, the gist of the present invention is that the surface layer (
A laminated film for packaging characterized by having a laminated structure of A)/intermediate layer (B)/sealant layer (C).

Surface layer (A); Stretched polyester film intermediate layer (B): Biaxially oriented film having a laminated structure of polyamide layer/saponified ethylene-vinyl acetate copolymer layer/polyamide layer Sealant layer (C): Unstretched polypropylene film The present invention will be explained in detail below.

The laminated film for packaging of the present invention is composed of a surface layer (A), an intermediate layer (B), and a sealant layer (C).

First, the surface layer (A) will be explained.

The surface layer (A) is made of a stretched polyester film.

The stretched polyester film is preferably biaxially stretched. And, as a stretched polyester film,
In particular, oriented polyethylene terephthalate or polyethylene naphthalate is preferably used.

The thickness of the surface layer (A) is preferably in the range of 7 to 25 microns.

If it is less than 7μ, the laminated film is likely to whiten during retorting, and if it exceeds 25μ, not only will the production cost increase, but the anti-whitening effect will be saturated, and the film will become hard and difficult to handle.

Next, the intermediate layer (B) will be explained.

The intermediate layer (B) is composed of a biaxially stretched film in which a polyamide layer/a saponified ethylene-vinyl acetate copolymer layer/a polyamide layer are laminated in this order.

The raw material polyamide resin constituting the above polyamide layer is
Generally, nylon 6, nylon 66, nylon 12
, nylon 6/66, aromatic nylon, etc.

Specifically, raw materials for the polyamide resin include lactams such as ε-caprolactam, enanthralactam, capryllactam, lauryllactam, α-pyrrolidone, and α-piperidone, 6-aminocaproic acid, 7-aminohebbutanoic acid, Nylon salts of omega amino acids or dibasic acids and diamines such as 9-aminononanoic acid and 11-aminoundecanoic acid are used.

The dibasic acids mentioned above include munroic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid,
Azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, hexadecenedioic acid,
Octadecanedionic acid, octadenedionic acid, eicosadionic acid, eicosenedionic acid, tocosandionic acid,
2゜2.Aliphatic carboxylic acids such as 4-trimethyladipic acid, 1. Cycloaliphatic dicarboxylic acids such as 4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid,
Examples include aromatic dicarboxylic acids such as phthalic acid and xylylene dicarboxylic acid, and examples of diamines include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, xamethylenediamine, heptamethylenediamine, and octamethylenediamine. , nonamethylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene diamine, tridecamethylene diamine, hexadecamethylene diamine,
Octadecamethylene diamine, 2°2.4 (or 2,
4.4) Aliphatic diamines such as -trimethylhexamethylene diamine, cycloaliphatic diamines such as cyclohexane diamine, methylcyclohexane diamine, bis-(4,4'aminocyclohexyl)methane, aromatic such as xylylene diamine Examples include group diamines.

The polyamide resin used in the present invention may contain well-known additives such as various stabilizers, filler pigments, dyes, lubricants, antiblocking agents, and various thermoplastic resins, as long as they do not exceed the spirit of the present invention. good.

On the other hand, the above saponified ethylene-vinyl acetate copolymer (
EVOH constituting the EVOH) layer is produced by saponifying ethylene vinyl acetate copolymer.

And EVOH has an ethylene content of 20 to 70 mo
1%, preferably 25 to 50 mo1%, and the degree of saponification of the vinyl acetate component is 95 mo1% or more, preferably 98 mo1
% or more are used. Ethylene content is 20mo
If it is less than 1%, melt extrudability will be poor and coloration will occur easily, while if it exceeds 70 mo1%, oxygen barrier properties will deteriorate. Moreover, when the degree of saponification is less than 95 mo1%, oxygen barrier properties and moisture resistance decrease.

The above EVOH contains a small amount of propylene, isobutyne, α
- α- such as octene, α-dodecene, α-octadecene, etc.
Comonomers such as olefins, unsaturated carboxylic acids, salts thereof, partial or complete alkyl esters, nitriles, amides, anhydrides, unsaturated sulfonic acids or salts thereof may be included. Further, a small amount of polyolefin resin, polyester resin, or polyamide resin may be blended.

In the intermediate layer (B) of the present invention, polyamide layer/EVO
The thickness of each layer of H layer/polyamide layer is from polyamide layer 3 to
10μ, EVOH layer 3-20μ, polyamide layer 3-10
μ, and the total thickness is preferably 10 to 30 μ. If the thickness of the polyamide layer is less than 3μ, it will not have sufficient pinhole resistance for use in packaging applications, and if it exceeds 10μ, it will not only increase the manufacturing cost but also reduce the hardness of the entire film. This also reduces handling performance. It is desirable that the two polyamide layers have the same thickness, but they can also have different thicknesses. If the thickness of the EVOH layer is less than 3μ, the resulting laminated film will not have sufficient gas barrier properties, and if it exceeds 20μ, the gas barrier properties will not only be saturated, but also the manufacturing cost will increase. It also becomes more expensive.

In order to manufacture the above intermediate layer (B), first, a polyamide layer/EVOH layer/polyamide layer is laminated in this order.
A substantially amorphous and unoriented unstretched laminated film (hereinafter referred to as "laminated unstretched film") is produced.

The above laminated unstretched film can be produced by a coextrusion method. As the coextrusion method, specifically, a multi-manifold die method, a feed block method, a multi-slot die method, etc. can be adopted. The coextruded laminated unstretched film is closely attached to the surface of a casting roll maintained at 40°C or lower, preferably 35°C or lower. As the adhesion means, known means such as electrostatic pinning method and air knife method can be used.

The laminated unstretched film is then biaxially stretched.

The method of biaxial stretching is simultaneous biaxial stretching (JP-A-52-115
880), sequential biaxial stretching (Japanese Patent Application Laid-Open No. 61-2739)
No. 31 Publication) may be used.

Alternatively, the film may be stretched after film formation using an annular die.

The stretching ratio of biaxial stretching is preferably 2 to 5 times in each axial direction, particularly preferably 2.5 to 4 times. If the stretching ratio is less than 2 times, the stretching effect will be small and the strength of the film will be poor.
Moreover, if it exceeds 5 times, the film will often break during stretching, resulting in poor long-run performance in practical terms.

In the case of tenter sequential biaxial stretching, for example, stretching is carried out 2 to 5 times in the longitudinal direction at 45°C to 80°C using a roll-type longitudinal stretching machine, and then using a hot air or thermal radiation type tenter (horizontal stretching machine). ) may be stretched 2 to 5 times in the transverse direction at 60 to 120°C.

In addition, in the case of tenter simultaneous biaxial stretching and tubular simultaneous biaxial stretching, for example, 2
What is necessary is just to stretch it 5 times.

By heat treatment after stretching, a stretched film with excellent dimensional stability can be obtained. The heat treatment temperature is preferably in a temperature range with a lower limit of 190°C and an upper limit of 500 degrees lower than the melting point of the raw material polyamide.

Next, the sealant layer (C) will be explained.

The sealant layer (C) consists of an unstretched polypropylene film. The thickness of the sealant layer (C) is 20 to 60μ
A range of is preferred. If it is less than 20μ, the seal strength when sealing the film will be low, and the seal may be damaged during use. Moreover, when it exceeds 60μ, not only does the cost increase, but also the thickness of the laminated film increases, and accordingly, the hardness of the film also increases, resulting in a decrease in handling properties.

The laminated film for packaging of the present invention has each of the above layers as a surface layer (
It has a structure in which A)/intermediate layer (B)/sealant layer (C) are laminated in this order. The respective layers can be bonded together according to a known method such as a dry lamination method using an adhesive or an extrusion lamination method.

The packaging laminated film of the present invention configured as described above has an oxygen permeability of 3 c c/rd-day-a tm or less under conditions of 25° C. and 65% RH,
In addition, it has the characteristic that hot water treatment at 105 to 127°C for 5 minutes or more is possible. Therefore, it can be particularly used as an advantageous packaging material in many other packaging fields, including food packaging and pharmaceutical packaging that require retort resistance.

When the laminated film for packaging of the present invention is to be made into a bag, the sealant layer (C) sides may be aligned and heat-sealed. As the heat-fusion method, a heat sealing method is preferably employed, but other methods may be employed as long as the sealing strength is sufficient.

The bag can be of any shape, including one-sided biro type, three-sided seal type, and gusset type.

〔Example〕

Next, the present invention will be explained in more detail based on examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

In the following examples, the physical properties of the films were evaluated by the methods described below.

(1) Oxygen transmission rate (cc/rd ・24 hrs)
Oxygen permeability measuring device 0XY-TRAN100 type (Mod
erncontro1) at 25°C and 60%
Measured under RH conditions.

The above oxygen permeability measurement was performed before and after the next retort test.

(2) Retortability Perform retort treatment at 127°C for 5 minutes. And 23°
After being stored for one day under conditions of C150% RH, the appearance is observed and the oxygen permeability is measured.

Example 1 <Manufacture of intermediate layer (B)> Nylon 6 resin (Tsubamitsudo 102 manufactured by Mitsubishi Kasei Corporation)
2) was extruded from two melt extruders, and EVOH (EVAL EP-F manufactured by Kuraray Co., Ltd.) was extruded from another melt extruder.
IOIB, ethylene content 32mo1%, saponification degree 99
．． 6mo1% or more) was used as an intermediate layer and laminated in three layers in a T-gui.

The above laminated film was brought into close contact with a cooling roll kept at 30° C. by electrostatic pinning and rapidly cooled to obtain a laminated unstretched film having a thickness of 51 μm for each layer and a total thickness of 153 μm.

The above-mentioned laminated unstretched film is introduced into a longitudinal stretching machine composed of multiple rolls, and longitudinally stretched at 60°C and 3 times the strength.
Subsequently, the film was introduced into a tenter, and subjected to transverse stretching at 90°C and 3.5 times, and further heat-treated at 2000°C.

The film is made by cutting both sides of the film and winding it up using a winder.The film consists of a polyamide layer/EVOH layer/polyamide layer, with each layer having a thickness of about 5μ and a total thickness of about 15μ.
A laminated biaxially stretched film of μ was produced.

<Manufacture of laminated film> First, both surfaces of the intermediate layer (B) were subjected to corona treatment to achieve wetting by a wetting reagent of 52 dyn or more.

Next, apply adhesive (Toyo Morton #) to one side of the intermediate layer (B).
900 adhesive diluted with ethyl acetate to a solid content concentration of 30%) was applied to a thickness of 10μ, and heated with hot air at 80°C for 30 minutes.
After drying for minutes (approximately 3μ as an adhesive layer), 30μ of unstretched polypropylene (CP) was applied as a sealant layer (C).
P) A film (S type, manufactured by Tokyo Cellophane Co., Ltd.) was crimped.

Next, a 16μ biaxially oriented polyethylene terephthalate (PET) film, one side of which was corona treated, was used as the surface layer (A), and one layer of the same adhesive as above was applied to the corona treated side.
After coating to a thickness of 0μ and drying with hot air at 80°C for 3 minutes (approximately 3μ as adhesive layer), it was pressed together with the nylon 6 side surface of the intermediate layer (B). Then, at 40℃
Aging was performed for 6 hours to obtain a laminated film with a total thickness of 67 μm.

Table 1 shows the evaluation results of the obtained laminated film.

Example 2 A laminated film was obtained in the same manner as in Example 1, except that the thickness of the intermediate layer (B) was changed to 7 μm for each layer, and the total thickness was changed to 21 μm.

Table 1 shows the evaluation results of the obtained laminated film.

Comparative Example 1 In Example 1, except that unstretched linear low-density polyethylene (LLDPE, UH-1 manufactured by Tamapoly Co., Ltd.) with a thickness of 30 μm was used in place of the CPP film of the sealant layer (C). A laminated film was obtained in the same manner as in Example 1.

Table 1 shows the evaluation results of the obtained laminated film.

Comparative Example 2 A laminated film was obtained in the same manner as in Example 1, except that the surface layer (A) was not laminated.

Table 1 shows the evaluation results of the obtained laminated film.

The laminated packaging film of the present invention can be used as an advantageous packaging material in many other packaging fields, including food packaging and medical product packaging that require retort resistance. can be used.

Claims (1)

[Claims] (1) Surface layer (A)/intermediate layer (B)/defined below
A laminated film for packaging characterized by having a laminated structure of a sealant layer (C). Surface layer (A): Stretched polyester film Intermediate layer (B): Biaxially oriented film laminated in the order of polyamide layer/saponified ethylene-vinyl acetate copolymer layer/polyamide layer Sealant layer (C): Unstretched polypropylene film