JPH081884A - Multilayered film - Google Patents

Abstract

PURPOSE:To obtain a multilayered film excellent in pinhole resistance, transparency and surface label aptitude after boiling sterilization treatment by laminating an outer layer composed of a mixture of amorphous nylon and other nylon, an intermediate layer composed of noncrystalline nylon or a nylon mixture and a seal layer. CONSTITUTION:An outer layer (A) composed of a mixture of amorphous nylon and straight chain aliphatic nylon, an intermediate layer (B) composed of one of amorphous nylon and straight chain aliphatic nylon or a mixture of them, an adhesive resin layer (C) and a seal layer (D) are laminated in the order of (A)-(C)-(B)-(C)-(D). As straight chain aliphatic nylon to be used, there are 6 nylon, 6.66 nylon, 6.1 nylon, a copolymer or mixture of them and the like. A resin used in the adhesive resin layer is a modified polyolefin resin and, concretely, a polyethylene resin or a polypropylene resin is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer film which is excellent in pinhole resistance and transparency and which has excellent label suitability on the film surface after boil sterilization.

[0002]

2. Description of the Related Art In the food industry, deterioration of product quality due to the influence of temperature, moisture, oxygen, ultraviolet rays, and microorganisms such as bacteria and mold in the distribution and sales process is a serious problem not only from the loss of business but also from the viewpoint of food hygiene. Is. In the past, antioxidants and preservatives were added directly to food as a method of preventing such quality deterioration, but recently, regulations on food additives have become stricter from the standpoint of consumer protection, and the amount added has decreased. Is an unavoidable situation. Boil sterilization or retort sterilization is performed as a method for treating bacteria attached at high temperature in order to ensure long-term storage stability of the contents under such circumstances. In particular, boiled sterilization is widely used in the food industry because it can be performed with simple equipment as compared with retort sterilization, and because it has a relatively low temperature, it does not require a special film as much as retort sterilization. Further, in the distribution and sales process, a pinhole may be generated in the product due to an external force such as a vibration or a drop, and air may enter the product to cause discoloration or deterioration of the product. Therefore, a multilayer film incorporating a nylon layer having excellent mechanical strength is used. However, if the nylon layer is made thicker in order to improve the pinhole resistance, the flexibility of the multilayer film is significantly reduced, and the pinhole resistance is not necessarily improved in direct proportion to the thickness of the nylon layer. It was Japanese Patent Application 1-274
Japanese Patent No. 857 discloses a multilayer film having a layer structure in which a polyamide resin layer is divided into multiple layers and an adhesive layer is inserted between the polyamide resin layers as a buffer material. However, with this layered structure, the label suitability of the film surface was significantly reduced after boil sterilization, and the trouble of dropping the label attached to the product frequently occurred.

[0003]

The object of the present invention is to provide a transparent packaging material for foods to be heat-sterilized,
It is intended to provide a multilayer film having excellent boil resistance, label suitability and pinhole resistance.

[0004]

According to the present invention, the outer layer (A) is a mixture of amorphous nylon and linear aliphatic nylon,
The intermediate layer (B) is composed of an amorphous nylon or a linear aliphatic nylon alone or in a mixture, and the adhesive resin layer (C)
And the sealing layer (D) is (A)-(C)-(B)-(C)
It is a multi-layer film characterized by being laminated in the order of- (D). The linear aliphatic nylon used in the present invention includes 6 nylon, 6.66 nylon, 6/10 nylon, 6/12 nylon, 11 nylon, 12 nylon,
And copolymers and mixtures thereof.

The amorphous nylon content of the layer (A) is 5 to 2
0% is desirable. If the content is less than 5%, the label suitability will be significantly reduced and the product label will fall off. On the other hand, if the content exceeds 20%, the layer (A) becomes cloudy and the transparency decreases. Further, in consideration of transparency, 6 nylon is preferable as the linear aliphatic nylon. The layer (B) is a single substance or a mixture of amorphous nylon or linear aliphatic nylon, but 6.66 nylon is preferable in consideration of transparency and flexibility.

The resin used in the adhesive resin layer (C) is a modified polyolefin resin, and specifically, a polyethylene resin, a polypropylene resin, a copolymer thereof or a copolymer with a different α-olefin, or ethylene-. Acrylic acid, methacrylic acid and other monobasic unsaturated fatty acids such as vinyl acetate copolymer, maleic acid, phthalic acid,
An acid-modified olefin resin obtained by chemically binding an anhydride of a dibasic unsaturated fatty acid such as itaconic acid, that is, maleic anhydride is used. Considering heat resistance and pinhole resistance during high temperature sterilization, acid-modified linear low-density polyethylene is most preferable. Further, the outside (C) and the inside (C) may be different adhesive resins.

The seal layer (D) is a low density polyethylene (L
DPE), linear low density polyethylene (LLDPE),
Polyolefin resins such as medium density polyethylene (MDPE), high density polyethylene (HDPE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA) which is an ethylene copolymer, ethylene-methyl methacrylate copolymer ( EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer (EEA), ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH),
Ethylene-acrylic acid copolymer (EAA), ethylene-
Methacrylic acid copolymer (EMAA), ionomer (I
ON) and other resins can be used. Although the optimum resin varies depending on the use of the film, ethylene-methacrylic acid copolymers or ionomers are preferable for preventing dripping in products that are deep-drawn and vacuum-packed in meat products. The nylon layer is divided into two layers (A) and (B) through the adhesive resin layer, as in Japanese Patent Laid-Open No. 1-274857, and the adhesive resin layer functions as a shock absorbing material. However, as a result of detailed examination of a resin capable of exhibiting a function as a buffer material, it was found that all acid-modified polyolefin resins having a Shore hardness (D) (ASTM D2240) of 60 or less are possible.

[0008]

Example A five-layer film having a total thickness of 200 μm was prepared using the following raw materials with a five-layer multi-manifold coextrusion die. The obtained film was confirmed with a vacuum packaging machine (FV-6300 manufactured by Omori Machine Industry Co., Ltd.) for moldability and used as a content.
About 70 g of baked pork blocks were filled and vacuum packed to prepare an evaluation sample. The lid material used at that time was 25 μm in a 100 μm 5-layer film with the same layer structure as the above bottom material.
A dry-laminated OPP (biaxially oriented polypropylene) film was used. The packed sample was sterilized in a boiling tank at 90 ° C. for 20 minutes, and the change in appearance and the pinhole resistance by a drop test were evaluated. Label suitability was evaluated in the state where the film alone was boiled under the same conditions, cooled, and the surface was condensed. Oxygen gas barrier property is Mocon OX
The film before sterilization was measured by TRAN (JIS K 7126 B method).

(Raw materials used in coextrusion) Ny1: 6 nylon / amorphous nylon = 80/20 Ny2: 6 nylon / amorphous nylon = 90/10 Ny3: 6 nylon / amorphous nylon = 95/5 Ny4: 6 nylon / amorphous nylon = 70/30 Ny5: 6 nylon Ny6: 6.66 nylon Ny7: 12 nylon contact 1: adhesive resin acid-modified LLDPE contact 2: adhesive resin acid-modified EVA EMAA: ethylene-methacryl Acid Copolymer ION: Ionomer As comparative examples, the sample prepared by the above coextrusion method and the sample prepared by the dry lamination method were used. The dry laminating 6 nylon and LLDPE films were of general grade. The results are shown in Tables 1 and 2.

Table 1 Layer composition and thickness (μm) Manufacturing method 1 2 3 4 5 Ex 1 Coextrusion Ny1 (20) contact 1 (40) Ny5 (50) contact 1 (20) EMAA (70) 2 Coextrusion Ny2 (15) contact 2 (40) Ny6 (60) contact 2 (20) ION (65) Example 3 Coextrusion Ny3 (30) Contact 2 (40) Ny3 (30) Contact 1 (20) EMAA (80) Ratio 1 Coextrusion Ny4 (20) Contact 2 (40) Ny5 (50) Contact 1 (20) EMAA (70) Comparison 2 Co-extrusion Ny5 (15) Contact 1 (40) Ny5 (60) Contact 2 (20) ION (65) Example 3 Dry Laminate 6Ny (70) / LLDPE (130)

Table 2 Appearance of pinholes Appropriate label 1 ○ None 450 Application 2 ○ None 390 cases 3 ○ None 350 Ratio 1 × None 460 Comparison 2 ○ None 55 cases 3 ○ Yes 50

The evaluation was carried out by the following method. Appearance: 90 ° C x 20 minutes Check for curl and turbidity of the film after boiling ◯: Good, x: White turbidity Pinhole resistance: 10 samples are packed in a cardboard box, and a cardboard is placed on concrete at a height of 1 m. Presence / absence of sample that was dropped 10 times on each side of the box and leaked air through pinholes etc. Label suitability: 90 ℃ × 20 minutes After boiling, put in a refrigerator at 5 ℃ 1
Leave it for 2 hours, then take it out to room temperature and apply a label with a constant load on the surface of the sample with moisture in the atmosphere condensed on the entire surface, and measure the peel strength (unit: g / 25 mm width)

[0013]

EFFECT OF THE INVENTION The multilayer film according to the present invention is excellent in deep drawability and heat resistance, has no curl even after high temperature sterilization, and has no migration of residual solvent odor which occurs in a dry laminated film, and thus has high commercial value. We can provide products.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B32B 27/32 101 8413-4F

Claims (6)

[Claims] 1. The outer layer (A) is a mixture of amorphous nylon and a linear aliphatic nylon, and the intermediate layer (B) is composed of an amorphous nylon or a linear aliphatic nylon alone or in a mixture. A multilayer film comprising an adhesive resin layer (C) and a seal layer (D) laminated in the order of (A)-(C)-(B)-(C)-(D). 2. The (A) layer is a mixture of 6 nylon and amorphous nylon, and the content of the amorphous nylon is 5 to 20%.
The multilayer film according to claim 1, wherein 3. The multilayer film according to claim 1, wherein the (B) layer is 6.66 nylon. 4. The (C) layer has a Shore hardness (D) (AS
The multilayer film according to claim 1, 2 or 3, which is an acid-modified polyolefin resin having a TM D 2240) of 60 or less. 5. The multilayer film according to claim 1, wherein the layer (C) is an acid-modified linear low-density polyethylene. 6. The (D) layer is an ethylene-methacrylic acid copolymer or an ionomer.
The described multilayer film.