JPS6045654B2 - Breathable plastic film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plastic film with increased gas permeability.

When gas sterilizing medical instruments, etc., the method is generally to wrap the instruments in packaging material and then sterilize them.

The most common packaging materials are paper and plastic film. However, although paper has good air permeability and sterilization gas permeability, it is weak against moisture and there is a risk that it may enter after sterilization.Also, ordinary plastic film has low air permeability and requires a considerable amount of time to sterilize. are doing. Therefore, there is a strong desire for a film that has high permeability to gases such as sterilizing gas and is substantially impermeable to bacteria. In view of these circumstances, the present inventors conducted various studies and found that a thermoplastic film that has been subjected to embossing treatment at a relatively low temperature has good air permeability and is impermeable to germs. It was completed.

However, it is well known that embossing is applied to various thermoplastic films.

In conventional embossing methods, a plastic film is heated to a temperature above the softening point of the film material and embossed to facilitate and speed up the processing. In contrast, the film of the present invention is embossed at a temperature at least 20°C below the softening point of the film material, which is much lower than the embossed film used in conventional embossing. The special effects of the film of the present invention can only be achieved through low-temperature embossing.

That is, the present invention provides an air-permeable film obtained by embossing a thermoplastic film having a thickness of 10 to 100 μm at a temperature at least 20°C lower than the softening point of the film using an embossing machine that has an uneven pattern on the processed surface. It concerns an expanded plastic film. Examples of the thermoplastic plastic include polyethylene, polypropylene, polyester, polystyrene, polyvinyl chloride, and nylon.

The thickness of the thermoplastic film is 10 to 100 microns, preferably 20 to 70 microns.

Any conventional embossed crosspiece may be used as long as the uneven pattern on the processed surface is suitable for producing the film of the present invention, and the processed surface may be either flat type or roll type.

Both of the convex and concave processed surfaces may be made of metal, or may be a combination of a convex metal and rubber having a Shore hardness of 80 degrees or more, preferably 85 to 100 degrees. The uneven pattern on the processed surface may be dotted, linear, or net-like, and these may be combined to form characters, figures, designs, etc. The pattern on the processed surface of the embossing machine is made up of unevenness on the processed surface and is formed so that the film can be partially bent at an angle within a certain range. The tip of the bent portion is locally a curved surface, and its radius R is usually 0.1-0.5TI$L1, preferably 0.2-0.
4? It is. The height of the peak in a convex type is usually 0.5~5w
n1 is preferably 1 to 3 T$. It is preferable that the pattern is distributed as uniformly over the entire processed surface as possible. If the number of bending points in the film formed by the pattern is too small, the air permeability effect may not be sufficiently achieved. For patterns, at least 1 per cT1
It is good to have TW1. As mentioned above, embossing is carried out at a temperature at least 20 DEG C. below the softening point of the film, but usually at a temperature of 5 DEG to 50 DEG C.

The pressure applied to the film during embossing is desirably higher than that of conventional methods, and is usually 5 to 500 k9/Cdl, preferably 10 to 200 k9/Cd.

When the processing machine is rotary, the roll pressure is nip pressure of 50
~150k9/Cml preferably 70-100kg/C
m, and the rotational speed of the roller is 3 to 20 m.m. / minute is appropriate. The film according to the invention obtained by such treatment is substantially non-porous and has a high gas permeability. For example, the oxygen permeability of polyethylene with a thickness of 40μ is 7000~
25000cc/i. Between 2 fences (24002cc before treatment)
/d・24 hours), 70 for polypropylene with a thickness of 30μ
00~20000CC/7T1●24 hours (9 before treatment
0 cc/24 hours), and the gas permeability was increased by about 3 to 2 compared to that before treatment.

Such a film according to the present invention can be suitably used for medical sterilization/sterilization bags, and can also be used for pears, pears, etc. during the development process.
It can be used as packaging materials that require high air permeability, such as protective bags for fruits such as peaches.

EXAMPLES The present invention will be described in more detail with reference to Examples below.

Example 1 High-pressure polyethylene film with a thickness of 60μ (softening point:
90°C; Oxygen permeability: 2400cc・0.1噸/d・
24 hours) using a rotary embossing machine (having a convex metal roller and a flat rubber roll with a shore hardness of 99 degrees) at a roll pressure of 100k9/CrrL (nip pressure), a roll temperature of 25°C, and a roll rotation speed of 5TL. Embossed in / minute.

The oxygen permeation of this film was measured and was 10,000c.
c/d・24 hours. 90 using this film
A bag of 180 mIn was made, latex rubber was placed therein, and the bag was kept in ethylene oxide gas for 24 hours.The amount of ethylene oxide gas that had passed through the film and was adsorbed to the latex rubber was measured and found to be 2,700 ppm. This value is approximately the same as that of a commercially available paper sterilization bag (2900 ppm). Furthermore, the presence or absence of bacterial permeation through this film was examined using Serratia bacteria (size: 0.22 μm), but no bacterial permeation was observed. Example 2 Unstretched polypropylene with a thickness of 30p (softening point 150°C; oxygen permeability: 900cc・0.1Tmm/I・24
time) using a rotary embossing machine with metal rolls for both convex and concave types, with a roll pressure of 120 kg/α (nip pressure),
Embossing was carried out at a roll temperature of 20° C. and a roll rotation speed of 77 TL/min.

The oxygen permeation rate of this film is 12000cc/Rrl・
It was hot in 24 hours. In addition, in the same manner as in Example 1, the amount of ethylene oxide gas permeated and the presence or absence of bacteria permeation were investigated. Ta.

Claims (1)

[Claims] 1. A plastic film with increased air permeability, which is obtained by embossing a thermoplastic plastic film with a thickness of 10 to 100 μm at a temperature at least 20° C. lower than the softening point of the film using an embossing machine having an uneven pattern on the processed surface.