JPH01319580A - Packing material - Google Patents

Abstract

PURPOSE:To obtain a packing material having compressive elasticity and sealing performance even under heating by irradiating a specified laminated film with radiation for crosslinking. CONSTITUTION:Radiation (e.g., electron rays, gamma rays or X rays) is applied to a gas barrier film-PE composite film/low density PE-based foamed material/ PE-gas barrier film composite film laminate for crosslinking to provide the objective packing material. In addition, the irradiation dose is preferably 20-30 Mrad in case of using electron rays.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a packing material. More specifically, the present invention relates to a packing material that has compressive elasticity and sealing properties even under heated conditions.

[Conventional technology]

Polyolefin foam has excellent hygiene, processability, compressive elasticity,
Because it has various properties such as excellent sealing properties, it is widely used as a packing material for lids, industrial packing, etc. However, polyolefin foam alone or laminated with gas barrier film-polyolefin composite film, etc.
Packing materials that require heat resistance above 0°C include:
Not satisfied with adequate compressive elasticity and sealability.

For example, heat-resistant foam packing materials such as high-density polyethylene and polypropylene are used as packing for rotary container lids such as screw caps and pilfer-proof caps.

When sterilization is carried out at 120°C for 30 minutes for 1 knot, the heat resistance is satisfactory, but there are problems in that it becomes hard, has poor compressive elasticity, and has poor sealing properties. Also,
Similar problems are also observed in these polyolefin foams laminated with a gas barrier film-polyolefin composite film.

[Problem to be solved by the invention]

The present invention aims to solve these problems and provide a banking system that has compressive elasticity and sealing properties even under heating conditions.

[Means to solve the problem]

The banking system that achieves the above object of the present invention is made of a laminate of gas barrier film-polyethylene composite film/low-density polyethylene foam/polyethylene-gas barrier film composite film which is cross-linked by irradiation with radiation. .

As the low-density polyethylene foam, low-density polyethylene or high-density polyethylene can be used for about 5 to 50%
A polyethylene mixture compounded with a proportion of flt% by weight is foamed and extruded by any method, and a C.I.-Autumn material having a foaming ratio of about 1.2 to 10 times and a thickness of about 0.5 to 5 mm is used.

The composite film cass barrier film 11 laminated on both sides of such a low-density polyethylene foam has an oxygen permeability and a carbon dioxide permeability of 30cc/m2/24hrs/atm based on ASTM nn-1434-x9s+#. Below JIS Z-
Polyvinyritine chloride (Pv +
+ t: ) film \, saponified ethylene-vinyl acetate copolymer (EVAL) film 1], oriented polypropylene (OPP) film, polyethylene layer [nophthalate 1-(+) IET) film [water vapor barrier property] and generally has a thickness of about 10 to 100 μm. On at least one side of these Casbarrier-+1 films 11, low density polyethylene (PE), ionomer resin, etc. are composited with a thickness of about 10 to 60 μm 3.
, 2.3 Examples of such composite films are as follows.

PF/PVDC/PE composite film +1
+(/IE VAL/PR composite film O
P l) / P IE composite film PET/ICE composite film The low density polyethylene foam and the composite film are laminated by 1-ly lamination method, extrusion using low density polyethylene, and the polyethylene layer side of the composite film and the foam. This is carried out by a known lamination method such as a lamination method.

The thus obtained laminate is crosslinked by irradiating it with radiation such as electron beams, gamma rays, and X-rays. When an electron beam is used, the irradiation dose is about 5 to
40 Mrad, preferably about 20-30 Mrad, if the irradiation dose is less than this, the intended purpose cannot be achieved, while if the irradiation dose is too high, the composite film,
In particular, this may lead to deterioration of the gas barrier film layer. .

〔Effect of the invention〕

The radiation-irradiated packing material of the present invention not only satisfies heat resistance even when it is used as a packing material for rotary container lids and subjected to I.L.I. sterilization treatment at 120°C for 30 minutes. It has excellent compressive elasticity and sealing properties, and has the effect of providing extremely favorable results in terms of content retention properties and hygiene.

〔Example〕

Next, the present invention will be described in detail with reference to examples.

Example low density polyethylene (Ojing Petrochemical Products Mirason C-2
604P; density 0.932g/cnj, melt index 2.5g/l, 0 minutes) 75 parts by weight and high-density polyethylene (Hisex 2200J; density 0.9683/+all, meltintex 6.0g)
/10 minutes) to 25 parts by weight of a known blowing agent, and this mixture was fed to an extruder with a diameter of 150 mm to give a density of 0.5 g.
/cn? A sheet-like foam having a thickness of 2.0 mm was molded.

01) P composite film (Tokyo Cellophane Paper Products OPP MI; 0PP2
0 p m/PE20 μm) or PET composite film (Unitika product Enfret PET-12; PET]
, 2 p m/PE22 p m), low density polyethylene (Mitsui Petrochemicals Mirason 11P; density 0.91
．． 7 g/i, null 1 - index 6.7 g/l, 0 min) to a thickness of 35 μn1, and laminated by extrusion lamination method.

The thus obtained composite film/low-density polyethylene/low-density polyethylene foam/low-density polyethylene/composite film laminate was exposed to the popular At an accelerating voltage of 750 KV,] 5 M r a cl soil or;
) OM r +i d electron beam was irradiated. .

The obtained electron beam irradiation crosslinked layer was heated to 120°C.
L'l' 1iil Dimensions in both vertical and horizontal directions when heated 7
1. The rate of change is as shown in Table 1. It can be seen that the dimensional change due to heating by electron beam irradiation becomes smaller than 2. Bon size η (change rate (ne))
1 go noino I kum --- rotation r-a --- vertical and horizontal white.
-1 Lateral direction -1 opp composite film 0 6.
8 2.12 15
2.0 0.83 30
0.5 0.24- PET composite fill, l
! , 0 6.8 2.35
15 2.0 0,56
30 0.5 0.2”
Each laminate in Table 2 was punched out into a disk shape with a diameter of 28 mm, fitted into a pilfer-proof cap, and 10011
Capacity filled with IQ boiling water] 1. The Omfl bottle was sealed using a sealing machine (Model 310A manufactured by Toyo Foods Machinery Co., Ltd.).

Next, please! 7 pulls 1 Heau 1 Taleb (1
Hemi Sei J', Model 5R740) and heated to 120℃ for 3 hours.
After heating for 0 minutes, the bottle was left at room temperature for 48 hours.The degree of vacuum inside the bottle was determined by using a vacuum cage, and the sustained reduced pressure resistance value was determined.

In addition, the force required to rotate and open the cap is reduced by 1
The lux meter was set to all +, and the lux value was determined from the time the cap was opened.

The measurement results in (1) below are shown in Table 2 below as the average value (and measurement value range) of the five measurement values.

Table 2 Continuous decompression resistance value Opening 1-luke value No.
-gL,,-(K,,B-cm)-10(Sute0)■. 2 (0-2) 2 22.0 (1,6-30) 5.2 (5-6
)3 32.4 (32-34) 8.0 (Zupete 8) 4 0 (Shuete 0) 1.6 (0-2) 5
20.8 (12-~26) 5.0 (t hete 5
)6 33.2 (32-34) 8.0 (all 8) From this result, the following can be said.

(1) Packing materials that are not subjected to electron beam irradiation treatment are 12
By sterilizing it in a cold oven at 0°C for 130 minutes, it does not lose its thermal properties and loses its function as a packing material.

(2) Materials irradiated with 15 Mrad of electron beam function sufficiently as packing materials even after sterilization, but variations in sustained decompression resistance are observed.

(3) Products irradiated with 30 Mrad of electron beams do not melt even under sterilization conditions and have excellent heat resistance and excellent compressive elasticity and sealing properties.
The content retention properties are stably exhibited.

Further, the opening torque value (8 kg-cm) in this case is a moderate value that even women and upper elementary school students can easily open.

Claims (1)

[Claims] 1. A packing material in which a gas barrier film-polyethylene composite film/low-density polyethylene foam/polyethylene-gas barrier film composite film laminate is irradiated with radiation and crosslinked.