JPH05287083A - Film or tube having heat sealability and heat resistance - Google Patents

Abstract

PURPOSE:To improve the heat sealability and heat resistance of a plastic film or tube. CONSTITUTION:A film laminate of a film layer 1 consisting of a plastic alone with a film layer 2 consisting of a plastic contg. a radiation energy absorbent is prepd. by simultaneous extrusion. The laminate is irradiated with a radiation, e. g. an electron beam, at such a dose that the gel fraction of the film layer 1 is 70% or higher and that of the film layer 2 is 30% or lower. Thus, the film layer 1 turns into a highly crosslinked layer 3, and the film layer 2 into a lowly crosslinked layer 4 due to the effect of the absorbent contained. The highly crosslinked layer improves the heat resistance, and the lowly crosslinked one is heat-sealable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat seal and heat resistant film or tube used for food packaging materials, medical infusion container materials and the like.

[0002]

2. Description of the Related Art Plastic films and tubes are used for packaging materials such as foods and medical infusion containers such as drip bags. For example, retort food packs are immersed in hot water. These films and tubes are irradiated with radiation such as an electron beam to cause a cross-linking reaction in the plastic, and thus have excellent heat resistance as compared with non-cross-linked ones.

[0003]

By the way, when such a film or tube is used as a packaging or container material, the ends of the film or tube are usually heat-sealed. However, when the film and the tube are crosslinked, the heat resistance is excellent, so that the heat seal property is rather deteriorated, and the efficiency of packaging, container formation, sealing work and the like is deteriorated.

An object of the present invention is to provide a film and a tube having heat sealability and heat resistance.

[0005]

The present invention provides a film or tube comprising a composite layer having a plastic layer containing a radiation energy absorber, wherein the gel fraction of the layer containing the radiation energy absorber is 30% or less. It is characterized by being irradiated with a radiation dose of

As for the film F in FIG. 1 and the tube T in FIG.
A composite film and a tube made of a film layer 1 made of plastic alone and a film layer 2 made by adding a radiation energy absorber to plastic are produced by composite coextrusion. This composite film or tube is irradiated with radiation such as an electron beam so that the plastic single layer has a gel fraction of 70% or more and the film layer containing a radiation energy absorber has a gel fraction of 30% or less. ..

The film F and the tube T thus obtained are formed as a composite layer of a high cross-linking layer 3 made of plastic alone and a low cross-linking layer 4 by adding a radiation energy absorber. A film and a tube having improved heat resistance and heat sealability due to the low cross-linking layer 4 and having heat sealability and heat resistance as a whole can be obtained.

[0008]

【Example】

(Example 1) Low density polyethylene LDPE was used as a raw material, and as shown in FIG. 1, a single layer 1 thereof and N-N'-diphenyl-P-
A two-layer film consisting of layer 2 with 5% addition of phenylenediamine is produced by extrusion with a thickness of 0.5 mm. An electron beam of 500 MV at 30 Mrad was applied to this two-layer film.
Irradiation is performed to cross-link the plastic single layer 1 of LDPE.

(Example 2) Vinyl acetate VA of 10
% Ethylene-vinyl acetate EVA as raw material,
As shown in FIG. 2, a two-layer tube consisting of the single layer 1 and a layer 2 obtained by adding 3% of phenyl-α-naphthylamine as a radiation energy absorber to the same raw material is extruded to have a thickness of 0.2 mm. Then, the two-layer tube was irradiated with an electron beam at 500 kV for 20 Mrad, and EVA was applied.
The single plastic layer 1 is cross-linked.

(Comparative Example 1) Low density polyethylene LDPE
500 mm of extruded film with electron beam of 500
Irradiate with 30 Mrad at kV.

Comparative Example 2 An 0.2 mm thick extruded tube of ethylene-vinyl acetate EVA (VA10%) was irradiated with an electron beam at 500 kV for 20 Mrad.

Table 1 shows the evaluation results of the films and tubes obtained in the above Examples and Comparative Examples. (Note) Heat-sealing strength: Peel strength after heat-sealing at 120 to 150 ° C. Heat resistance: 120 ° C. Left in autoclave for 60 seconds, and then evaluated by appearance change (shrinkage, coloring, shape change) [○ … Good, ×… bad]

The results of gel fraction after electron beam irradiation are shown in Table 2. The gel fraction was measured as follows. The sample is immersed in xylene (120 ° C) for 6 hours, and then the insoluble matter is filtered through a filter paper, and then the solvent (xylene) contained in the residue on the paper is dried at 80 ° C and 0.01 mmHg until a constant weight is obtained. Then, the weight of the insoluble matter is measured. Then, from the initial weight W ₁ before immersion and the weight W _{2 of the} insoluble matter, the gel fraction showing the degree of crosslinking is obtained by (W ₂ / W ₁ ) × 100%.

A polycyclic aromatic compound is used as the radiation energy absorber. For example, the following can be mentioned. 1 Styrenated phenol 2 2-2'-methylene-bis (4methyl-6-tert-butylphenol) 3 2-2'-methylene-bis (4ethyl-6-tert-butylphenol) 4 4-4'-iso- Propylidene bisphenol 5 4-4'-butylidene-bis (3methyl-6-tertiary
Butylphenol) 6 1-1'-bis (4-hydroxy-phenyl) cyclohexane 7 4-4'-methylene-bis (2-6-di-tert-butylphenol) 82.6-bis (2'-hydroxy-3) '-Tert-Butyl-5'-methylbenzyl) 4-methyl-phenol 9 1-1-3-tris (2-methyl-4-hydroxy-5-tert-butyl-phenyl) butane 10 1-3-5- Tris-methyl-2-4-6-tris (3-5-tert-butyl-4-hydroxy-benzyl)
Benzene 11 Tris [β- (3-5-di-tert-butyl-4-hydroxy-phenyl) propionyl-oxyethyl] isocyanate 12 4-4′-thiobis (3-methyl-6-t-butylphenol) 13 2-2 ′ -Thiobis (4-methyl-6-t-butylphenol) 14 4-4′-Thiobis (2-methyl-6-t-butylphenol) 15 Phenyl-α-naphthylamine 16 Phenyl-β-naphthylamine 17 NN′- Diphenyl-P-phenylenediamine 18 N-N'-di-β-naphthyl-P-phenylenediamine 19 N-cyclohexyl-N'-phenyl-P-phenylenediamine 20 Aldol-α-naphthylamine 21 Thiobis (β-naphthol) 22 Thiobis (N-phenyl-β-naphthylamine) 23 Tri (nonylphenyl) phosphite 24 4 -4'-butylidene-bis (3methyl-6-t-
Butylphenyl-ditridecyl phosphite) The amount of addition varies depending on the crosslinkability of the plastic alone, and is adjusted within the range of 0.1 to 10%.

The plastics of the composite film and the tube are not limited to the same kind of plastics, but different kinds of plastics can be combined.

[0016]

As described above, in the composite film and tube of the present invention, the crosslinking reaction of the plastic layer containing the radiation energy absorber is reduced, and the plastic single layer is sufficiently crosslinked. Compared to films and tubes made only of plastic, it has superior heat sealability and has the same level of heat resistance.

[Brief description of drawings]

FIG. 1 is an explanatory view of an example of a composite film of the present invention.

FIG. 2 is an explanatory view of an embodiment of the composite tube of the present invention.

[Explanation of symbols]

1 Single layer of plastic 2 Layer with radiation energy absorber added to plastic 3 Highly crosslinked layer 4 Lowly crosslinked layer

Claims (1)

[Claims] 1. A film or tube comprising a composite layer having a plastic layer containing a radiation energy absorber, which is irradiated with a radiation dose such that the gel fraction of the plastic layer containing the radiation energy absorber is 30% or less. Film or tube having heat-sealing property and heat resistance