JPH08332703A - Multi-layer film - Google Patents

Abstract

PURPOSE: To improve the deep-drawing formability and pinhole resistance of a packing material to be heated for sterilization by layering an outer layer consisting of polypropylene resin, intermediate layer consisting of mixture of aromatic series and fatty series nylon, a gas barrier layer and a sealing layer in particular order through adhesive resin if necessary. CONSTITUTION: An outer layer (A) consisting of polypropylene resin, an intermediate layer (B) consisting of mixture of aromatic series and fatty series nylon, a gas barrier layer (C) and a sealing layer (D) are layered in the order of (A)-(B)-(C)-(D) or (A)-(C)-(B)-(D) through adhesive resin if necessary. As the outer layer, homopolypropylene whose melt flow rate is 2-20(g/10min.) or random copolymer of ethylene and propylene is desirable, and as the intermediate layer, mixture consisting of 6-nylon containing aromatic series nylon of 3-20% or mixture consisting of 6.66-nylon is desirable. These are formed by a co- extruding method, or by laminating multi-layer film consisting of (B), (C) and (D) layers prepared by the co-extruding method on the outer layer (A).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention improves deep drawability,
The present invention relates to a multilayer film excellent in curl, gas barrier property and transparency generated after boil sterilization.

[0002]

2. Description of the Related Art Performance required in the field of flexible packaging such as food packaging includes moldability, transparency and pinhole resistance. In the field of food packaging, heat sterilization such as boiling sterilization is performed to completely kill and remove microorganisms that cause deterioration and spoilage of food, and packaging work is performed in a clean room. In addition, a gas barrier property is given to the packaging material to prevent the deterioration and spoilage of foods due to oxygen gas and to improve the storage stability. However, in the distribution process, a pinhole may be generated due to vibration and drop applied to the product, outside air may intrude from the position, contact the product, and the product may be discolored or spoiled. For this reason, the packaging material is required to have pinhole resistance against rubbing due to vibration and impact due to dropping. In terms of pinhole resistance, a technique that has hitherto been widely used is a multilayer film in which a polyamide resin having an excellent impact strength is used for the multilayer film. However, when the content is large and used in high deep drawing, the thickness of the formed film becomes thinner, the impact strength decreases, and in order to satisfy the required pinhole resistance, the thickness of the polyamide resin must be increased considerably. There was a problem that it was necessary.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is to use a mixture of aromatic nylon and aliphatic nylon in the intermediate layer as a packaging material for heat sterilization treatment to obtain deep drawability and pin resistance. It is to provide a multilayer film having an improved hole property and an excellent gas barrier property.

[0004]

According to the present invention, an outer layer (A) made of polypropylene resin, an intermediate layer (B) made of a mixture of aromatic nylon and aliphatic nylon, a gas barrier layer (C), and a seal layer (D). Optionally via an adhesive resin, (A)-(B)-(C)-(D) or (A)-
(C)-(B)-(D) are laminated in this order, preferably the outer layer (A) has a melt flow rate (JIS K 6758 [test temperature 230.
C, test load 2.16 kgf]) = 2 to 20 (g / 10
Min) homopolymerized polypropylene [hereinafter abbreviated as homo PP] or melt flow rate (JIS K 6758 [test temperature 230 ° C, test load 2.16 kgf]) = 2 to 2
0 (g / 10 min) is a random copolymer of ethylene and propylene [hereinafter abbreviated as random PP], the intermediate layer (B) is a mixture of aromatic nylon and 6 nylon, and the content of aromatic nylon is 3-20% or a mixture of aromatic nylon and 6.66 nylon with an aromatic nylon content of 3-20%, made by coextrusion or made by coextrusion It is a multilayer film prepared by laminating a multilayer film composed of layers (B), (C) and (D) on the outer layer (A) of a single layer film.

Since the outer layer (A) is exposed to hot water or high temperature steam during heat sterilization, it may easily cause a phenomenon such as curling or clouding of the film, which may impair the appearance, due to the influence of moisture due to moisture absorption. By using polypropylene having excellent water resistance, these inconvenient phenomena are eliminated and practically excellent packaging performance is imparted. Melt flow rate of polypropylene resin used (JIS K 675
8 [test temperature 230 ° C., test load 2.16 kgf]) is preferably 2 to 20 (g / 10 minutes). When the melt flow rate is 2 (g / 10 minutes) or less, thickness unevenness is likely to occur during film production, and when it is 20 (g / minute) or more, wrinkles due to film heating unevenness are likely to occur during deep drawing. Considering heat resistance, homo PP having a high melting point is preferable. In consideration of transparency and flexibility, random PP is preferable.

The aliphatic nylon used in the (B) layer is
6 nylon, 6,6 nylon, 6,10 nylon, 6,
12 Nylon, 11 Nylon, 12 Nylon, and their copolymers and mixtures, etc. By using a mixture of aromatic nylon and aliphatic nylon as an intermediate layer of a multilayer film, the thin film of the film during deep drawing Is improved and excellent pinhole resistance is imparted. The content of aromatic nylon is preferably 3 to 20%. If the content is 3% or less, the effect of preventing film thinning during deep drawing is low, and pinholes are likely to occur. On the other hand, if the content exceeds 20%, the layer (B) becomes cloudy and the transparency of the film decreases. Further, considering transparency, the aliphatic nylon is preferably 6 nylon or 6.66 nylon.

For the gas barrier layer (C), ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyacrylonitrile, etc. can be used, but ethylene-vinyl alcohol copolymer is preferable from the viewpoint of barrier property. Also (C)
The layer may be outside or inside adjacent to the layer (B). The seal layer (D) is a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE), a medium density polyethylene (MDPE), a high density polyethylene (HDPE), a polypropylene resin such as polypropylene (PP), and an ethylene copolymer. Combined ethylene-vinyl acetate copolymer (E
VA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EEA), ethylene-ethyl acrylate-maleic anhydride copolymer (E Resins such as -EA-MAH), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), and ionomer (ION) can be used.

[0008]

EXAMPLE A raw material and adhesive resin shown below were used in a 6-layer multi-manifold coextrusion die with a total thickness of 200 μm.
6-layer film was prepared. Using a vacuum packaging machine (FV-6300 manufactured by Omori Machine Industry Co., Ltd.) for the obtained film, deep drawing was performed to confirm the thickness of the film and 300 as the content.
An evaluation sample was prepared by vacuum-packing baked pork blocks of about g. As the lid material used at that time, a film having the same layer structure as the bottom material and having a total thickness of 100 μm was used. The packed sample is sterilized in a boiling tank at 95 ° C for 30 minutes,
The change in appearance and the pinhole resistance by drop test were evaluated. Also, the oxygen gas barrier property is OXTRAN (JI
The film before sterilization treatment was measured by SK 7126 B method).

(Material used) PP1: Homo PP (melt flow rate = 10) PP2: Homo PP (melt flow rate = 1) PP3: Homo PP (melt flow rate = 30) PP4: Random PP (melt flow rate = 10) ) Ny1: 6 nylon / aromatic nylon = 90/10 Ny2: 6 nylon / aromatic nylon = 60/40 Ny3: 6.66 nylon / aromatic nylon = 90/1
0 Ny4: 6 Nylon EVOH: Ethylene-vinyl alcohol copolymer Contact: Adhesive resin Sealant: Seal layer Table 1 shows the layer constitution of Examples and Comparative Examples, and Table 2 shows the evaluation results.

Table 1 Layer structure and thickness (μm) 1 2 3 4 5 6 Actual 1 PP1 (40) contact (20) EVOH (20) Ny1 (40) contact (20) sealant (60) 2 PP4 (40) contact (20) ) EVOH (20) Ny1 (40) contact (20) sealant (60) Example 3 PP4 (40) contact (20) EVOH (20) Ny3 (40) contact (20) sealant (60) 4 PP1 ( 40) Contact (20) Ny3 (40) EVOH (20) Contact (20) Sealant (60) Ratio 1 PP2 (40) Contact (20) EVOH (20) Ny1 (40) Contact (20) Sealant ( 60) Comparison 2 PP3 (40) contact (20) EVOH (20) Ny1 (40) contact (20) sealant (60) Example 3 PP1 (40) contact (20) EVOH (20) Ny2 (40) contact ( 20) Sealant (60) 4 PP4 (40) contact (20) EVOH (20) Ny4 (40) contact (20) Sealant (60) 5 PP1 (40) contact (30) Ny1 (40) contact ( 30) Sealant (60)

Table 2 OTR film thickness Appearance Pinhole (cc / m ² · 24hrs) (μm) Occurrence Actual 1 1 50 ○ None Provided 2 1 50 ○ None Example 3 1 55 ○ None 4 1 55 ○ None Ratio 1 1 20 ○ Yes Comparison 21 50 × None Example 3 1 50 × None 4 1 25 ○ Yes 5 20 50 ○ None

The evaluation was carried out by the following method. -OTR: Oxygen gas permeation amount (23 ° C, 65%)-Film thickness: 80 mm The thickness of the deep drawn film was measured-Appearance: 95 ° C x 30 minutes Curling of the film after boiling,
Observation of unevenness and cloudiness (○: good, ×: uneven, cloudy) ・ Pinhole resistance: 10 samples were packed in a cardboard box and dropped onto concrete from a height of 1 m 10 times on each surface of the cardboard box. Presence of air leaked sample in pinhole, etc.

[0013]

EFFECTS OF THE INVENTION The multilayer film according to the present invention has a high commercial value because it does not thin the film at the time of deep drawing and has excellent pinhole resistance and does not deteriorate the appearance due to curling after high temperature sterilization. Can be provided.

Claims (7)

[Claims] 1. An outer layer (A) made of a polypropylene resin, an intermediate layer (B) made of a mixture of aromatic nylon and aliphatic nylon, a gas barrier layer (C), and a seal layer (D) have adhesiveness as required. Via resin, (A)-
(B)-(C)-(D) or (A)-(C)-(B)-
A multi-layer film which is laminated in the order of (D). 2. The outer layer (A) is melt flow rate (JI
SK 6758 [Test temperature 230 ° C, test load 2.1
The multilayer film according to claim 1, which is a homopolymerized polypropylene of 6 kgf]) = 2 to 20 (g / 10 minutes). 3. The melt flow rate (JI) is used as the outer layer (A).
SK 6758 [Test temperature 230 ° C, test load 2.1
The multilayer film according to claim 1, which is a random copolymer of ethylene and propylene of 6 kgf]) = 2 to 20 (g / 10 minutes). 4. The intermediate layer (B) is a mixture of aromatic nylon and 6 nylon, and the content of aromatic nylon is 3 to 20.
%, The multilayer film according to claim 1, 2 or 3. 5. The intermediate layer (B) comprises aromatic nylon and 6.6.
It is a mixture of 6 nylons and has an aromatic nylon content of 3
It is -20%, The multilayer film of Claim 1, 2 or 3. 6. The multilayer film according to claim 1, 2, 3, 4, or 5, which is produced by a coextrusion method. 7. (B) prepared by the coextrusion method,
The multilayer film according to claim 1, 2, 3, 4, or 5, which is produced by laminating a multilayer film comprising layers (C) and (D) on the outer layer (A) of a single layer film.