JPH02247239A - Stretched film with antibacterial effect - Google Patents

Abstract

PURPOSE:To provide the subject stretched film having a layer prepared by blending a polyolefin-based resin with a powdery zeolite containing specified metals in an ionic state and stretching the resultant composition as the surface layer and excellent in antibacterial, antifungal and hygienic properties. CONSTITUTION:With (A) a polyolefin-based resin, (B) a powder prepared by making (B2) one or more metals selected from silver, copper, zinc and tin to be carried on (B1) a porous zeolite (e.g. A type zeolite or mordenite) having <=10mum average particle size and a large ion exchange capacity in an ionic state in an amount of >=0.01wt.% on an anhydride basis and drying under heating is blended in an amount of 0.05-10wt.%, preferably 0.1-5wt.% on an anhydride basis based on (A). The resultant composition is subjected to monoaxial stretching (2-20 time) or biaxial stretching (4-80 time area ratio), thus obtaining the objective single layer film or the objective multi-layer film having the above-mentioned stretched layer as the surface layer.

Description

[Detailed description of the invention] [Background of the invention] Industrial applications TECHNICAL FIELD The present invention relates to stretched films.

More specifically, the present invention relates to an antibacterial stretched film that has antibacterial properties and has freshness retention and hygienic properties suitable for food packaging, medical packaging, and the like.

BACKGROUND OF THE INVENTION Recently, efforts have been made to impart freshness retention properties to food packaging materials, and various freshness retention packaging materials have been developed. Conventionally, packaging materials with a freshness-preserving function have been made by adding inorganic particles to the film and utilizing the ethylene adsorption and far-infrared radiation effects of the inorganic particles, or by retaining metals that have a bactericidal effect. There are products that utilize the antibacterial effect of inorganic fine powder. In particular, the inorganic fine powder used in the latter packaging material has excellent antibacterial and antifungal properties against various types of bacteria, so its application to packaging materials, especially in fields where hygiene is strongly required, is progressing. It is being

However, these fine powders with excellent antibacterial properties are also used in basic packaging materials such as various thermoplastic resins,
When kneaded and used, the antibacterial fine powder was often buried in the basic material and the original antibacterial effect of the fine powder was not fully exerted. Therefore, in order to obtain the desired antibacterial performance, it was necessary to add a large amount of antibacterial fine powder.

However, adding large amounts of fine powder may impair the properties required for basic packaging materials, such as strength, barrier properties, transparency, and heat sealability, so avoid it unless there are special circumstances. Needless to say, it's better.

[Summary of the invention]

Summary> As a result of intensive studies to solve the above-mentioned problems, the present inventors have developed a single-layer film to which zeolite powder with antibacterial activity is added, or a multi-layer film having a surface layer to which zeolite powder is added. The present inventors have discovered that an excellent antibacterial film can be obtained by stretching in the -axis or biaxial direction even when a relatively small amount of antibacterial inorganic fine powder is added.

Therefore, the stretched film having an antibacterial effect according to the present invention is a zeolite powder containing one or more metals selected from the metal group consisting of silver, copper, zinc, and tin in an ionic state in a polyolefin resin. It is characterized in that it comprises a layer formed by stretching in a uniaxial direction or biaxial direction a resin composition formed by blending 0.05 to 10% by weight on an anhydrous basis as a surface layer.

<Effects> The stretched film having antibacterial properties according to the present invention has excellent antibacterial properties, as shown in the experimental examples described later.

Further, the stretched film according to the present invention is highly practical in fields where antibacterial properties, antifungal properties, and hygiene are particularly required.

By employing the method used in conventional films, such as stretching in uniaxial or biaxial directions, as in the present invention, an antibacterial property improvement effect that is different from the purpose of stretching conventional films was obtained. is interpreted as something unexpected.

[Detailed description of the invention]

<Polyolefin resin> The polyolefin resin used in the present invention and blended with zeolite powder (details will be described later) is a known one,
Those conventionally used for producing stretched films can be used.

Typical examples of such polyolefin resins include (
(b) Ethylene homopolymer, (b) Ethylene and polymerizable monomers other than ethylene, such as propylene, budene-1,
Copolymers with α-olefins having about 3 to 12 carbon atoms such as hexene-1,4-methylpentene-1, (c) homopolymers of propylene, (d) propylene and α-olefins other than propylene Examples include trillion polymers with -olefins (excluding ethylene), (e) (co)polymers of these various α-olefins, and other blends.

Particularly preferred α-olefins to be copolymerized with ethylene or propylene are those having 4 to 8 carbon atoms, such as 1-butene, 1-pentene, 1-hexene-1,4-methyl-pentene, 1-octene. α-olefin is
Two or more types can be used in combination. Such a polyolefin resin can be obtained by any method such as a gas phase method, a slurry method, or a high pressure method, but in the present invention, it is produced by a method using a catalyst that does not contain chlorine in the polymerization catalyst. Preferably.

Zeolite powder> The zeolite powder blended into the above-mentioned polyolefin resin holds one or more metals selected from the metal group consisting of silver, copper, zinc, and tin in an ionic state. . In particular, in the present invention, in consideration of dispersibility in polymers, a porous synthetic or natural zeolite with a relatively small particle size, a large amount of ion exchange, and a large specific surface area is selected from the metal group of silver, copper, zinc, and tin. After holding one or more selected metals in an ionic state (for example, by bringing an aqueous solution of water-soluble salts of these metals into contact with H-type or alkali metal-type zeolite to perform ion exchange) , activated by heat and then dried is preferred.

Here, as a porous zeolite powder with a large ion exchange amount, synthetic products such as A-type, X-type, or Y-type zeolite, synthetic mordenite, high-silica zeolite, etc.
On the other hand, as natural products, mordenite, clinoptilolite, chabasite, etc. are preferable. The average particle size is preferably 10 μm or less in view of the physical properties and appearance of the film.

The total amount of bactericidal metals in the zeolite is desirably 0.01% by weight or more and the saturated amount or less, based on the anhydrous zeolite.

Further, the amount of this specific zeolite to be blended into the polyolefin resin is 0.05 to 10% by weight, preferably 0.1 to 5% by weight, particularly preferably 0. .2 to 3% by weight. If the blending amount is less than 0.05% by weight, the antibacterial and antifungal performance will be poor, while if the blending amount exceeds 10% by weight, the effect will not only become saturated and the cost will increase, but also problems such as coloring will occur, so it is preferable. do not have.

<Resin Composition> A resin composition obtained by blending a specific zeolite powder with a polyolefin resin as described above is formed into a film shape and stretched to constitute the surface layer of the stretched film according to the present invention.

Methods for blending specific zeolite with polyolefin resin include melt-kneading directly with a roll or mixer such as a Banbury Kneader 1 extruder, or mixing the polyolefin resin in advance with a Henschel type mixer to improve the dispersion of the zeolite. Various known methods can be applied, such as a method in which the mixture is mixed with the powder and then melted and kneaded using the mixer described above, or a method in which a highly concentrated masterbatch is first prepared and then diluted.

The resin composition formed in this manner may contain small amounts of other miscible resins, additives, or colorants, such as polyester, polystyrene, etc., or oxidized Additives such as inhibitors, neutralizing agents such as metal soaps and fatty acid amides, lubricants, anti-blocking agents, antistatic agents, ultraviolet absorbers, light stabilizers, fluorescent whitening agents, or organic pigments, Colorants such as inorganic pigments can also be added directly or as a masterbatch of resin or the like. However, these additives, coloring agents, etc. may reduce the color fastness and antibacterial performance of the product, so care must be taken with the type and/or amount added. In addition, it is preferable not to add anything that does not particularly require addition.

<Stretched Film> The stretched film having antibacterial properties according to the present invention includes a layer formed by stretching a resin composition containing zeolite powder as described above in a uniaxial direction or a biaxial direction as a surface layer. Here, "containing as a surface layer" means having as a surface the surface of a layer formed by stretching a resin composition in uniaxial or biaxial directions. Therefore, the antibacterial film according to the present invention includes a single layer film consisting only of a stretched layer containing zeolite powder, a multilayer film formed by laminating such a stretched film on one or both sides of another film,
Other things also exist.

The resin composition blended with zeolite powder can be formed into a film and stretched by a known method conventionally used in the production of stretched resin films. The stretching ratio of the resin composition blended with zeolite powder is preferably 4 to 80 times, especially 8 to 60 times in terms of area magnification in the case of biaxial stretching, and 2 to 20 times in the case of -axial stretching. , particularly preferably 4 to 10 times.

When forming a multilayer film by laminating other films, the resin composition containing zeolite powder can be stretched before or after laminating the other films. Alternatively, this resin composition can be laminated on another film that has been stretched in the -axial direction, and then stretched in the other axial direction.

In addition, a coextrusion method or an in-line lamination method is adopted to form and laminate a resin composition containing a specific zeolite powder and another resin composition to form a film simultaneously or afterward in a softened state. It is also possible to produce the resulting multilayer film by stretching it.

A wide range of other films can be used to be laminated to the resin composition film, and a typical example of such other films is a film molded from the above-mentioned polyolefin resin. . If the resin composition film has already been stretched at a predetermined magnification and no further stretching is performed after laminating other films, the other films to be laminated to the stretched resin composition film are non-stretchable materials, For example, it may be made of paper, resin foam, metal, nonwoven fabric, or the like.

The thickness of the resin composition layer containing zeolite powder in the stretched film having antibacterial properties according to the present invention varies depending on the use and purpose, but is generally 0.1 to 20 μm.
In particular, it is 0.5 to 10 μm1.

The stretched film having antibacterial properties according to the present invention is
It can be used as it is or after the necessary processing in applications where antibacterial and hygienic properties are particularly required.

<Experimental example> Example 1 High density polyethylene (density 0.960, Mll, 5) 9
8% by weight, A-type zeolite (average particle size 2μ) was held in an ionic state with 2.5% silver and 12% zinc on an anhydrous basis, and then heated and dried at about 200°C. 2 wt. This pellet was extruded using a T-die molding machine to make a film with a thickness of 100 μm, and this was stretched 6 times in the -axial direction to obtain a film with a thickness of 20 μm.

Example 2 Polypropylene (density 0.906, M12.3) was blended with 2% by weight of the same powder as in Example 1 and kneaded in the same manner to obtain a pellet, which was extruded with a T-die molding machine to form a thick Sa1.
I made a 0ms sheet. This sheet was sequentially stretched 5 times in the longitudinal direction and 10 times in the transverse direction using a sequential biaxial stretching method to obtain a thickness of 2.
A film of 0 μm was obtained.

Example 3 A pellet made of ethylene propylene copolymer (13% by weight of ethylene, MI5) mixed with 2'% by weight of the same powder as in Example 1, and a pellet made of the same polypropylene (containing powder) as used in Example 2. A laminated film having a surface layer made of an ethylene propylene copolymer blended with powder was prepared by extruding the sample (not shown) using a T-die coextrusion method. This laminated film was stretched 5 times in the longitudinal direction and 10 times in the transverse direction to obtain a film having a surface layer thickness of 2 μm and a total thickness of 20 μm.

Comparative Example 1 Using the same high-density polyethylene and zeolite powder (in which silver and zinc were held in an ionic state) as in Example 1, this was extruded by the T-die method to obtain an unstretched film with a thickness of 20 μm.

Comparative Example 2 The ethylene propylene copolymer of Example 3 was biaxially stretched in the same manner without containing powder to obtain a film with a thickness of 20 μm.

Antibacterial Evaluation Test Antibacterial evaluation tests were conducted on each of the films obtained in Examples 1 to 3 and Comparative Examples 1 to 2 by the method ζ shown below. The following Table 1 shows the results. As shown in this table, the films of the Examples of the present application kill bacteria in a shorter time than the films of the Comparative Examples, and have excellent antibacterial properties.

Antibacterial property evaluation test method The films obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were cut into 5C11 squares and placed in a petri dish (horizontally).
Drop the solution containing bacteria onto the film.

After storing it in an atmosphere at 23℃ for a certain period of time, the bacteria on the film were washed, and the washing solution was placed on an agar medium (mixed, the bacteria were grown, and the number of colonies formed was counted, and the antibacterial properties were evaluated. We used Staphylococcus aureus, the type of bacteria!

Claims (1)

[Claims] Zeolite powder containing one or more metals selected from the metal group consisting of silver, copper, zinc, and tin in an ionic state is added to a polyolefin resin at 0.0% on an anhydrous basis.
1. A stretched film having an antibacterial effect, comprising a layer formed by stretching a resin composition containing 05 to 10% by weight in a uniaxial or biaxial direction as a surface layer.