JPH03106950A - Moisture-permeable film - Google Patents

Abstract

PURPOSE:To prepare a film having an improved water vapor permeability and suitable for long-term storage of vegetable and fruit by compounding a specific filler into a film made from a polymer of an olefin or, if necessary, a copolymer of the olefin with another monomer. CONSTITUTION:A polymer of an olefin (e.g. ethylene) or, if necessary, a copolymer of the olefin with another monomer (e.g. vinyl acetate) is compounded with 5wt.% or more, pref. 5-60wt.%, filler which is a powder pref. having a mean particle diameter of 50mum or lower and is selected from the group consisting of sodium sulfate, magnesium silicate, magnesium hydroxide, and diatomaceous earth. The resulting compsn. is formed into a film having a thickness of 5-300mum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a moisture permeable film based on polyolefin, such as a moisture permeable film suitable for packaging materials for fruits and vegetables. (Prior Art) Polyolefins are used in a very wide range of applications because they are easy to process, transparent, and inexpensive, and are typical of so-called general-purpose resins. However, since polyolefins have high water vapor barrier properties,
When fruits and vegetables are wrapped in polyolefin film, the moisture that evaporates from the fruits and vegetables condenses inside the package, promoting the growth of mold. To prevent this, there is a known method of packaging fruits and vegetables in polyolefin film with holes of about 3 mm in diameter, but films with such large holes have virtually no water vapor barrier properties, and the fruits and vegetables may dry out. I end up. (Problem to be solved by the invention!!) Therefore, an object of the present invention is to provide a polyolefin film having water vapor permeability suitable for long-term storage of fruits and vegetables. (Means for Solving the Problems) To achieve this objective, the present invention provides an olefin polymer or olefin containing 5 to 60% by weight of a filler selected from sodium sulfate, magnesium silicate, magnesium hydroxide, and diatomaceous earth. and other monomers. (Specific Description of the Invention) As the olefin polymer according to the present invention, low-density polyethylene, medium-density polyethylene, high-density polyethylene, polybrobylene, and copolymers of ethylene and propylene or butene can be used. In addition, copolymers of olefin and other monomers include copolymers of ethylene and vinyl acetate, copolymers of ethylene and (meth)acrylic acid, copolymers of ethylene and methyl (meth)acrylate, etc. can. It may also be an ionomer. The filler of the present invention is mixed for the purpose of improving the moisture permeability of the film. The filler must be selected from one or more of sodium sulfate, magnesium silicate, magnesium hydroxide, and diatomaceous earth. When using other similar substances, such as calcium carbonate or aluminum silicate, moisture permeability hardly improves. The filler must be present uniformly in the film. For this reason and from the viewpoint of processing suitability, it is desirable to use the filler in powder form. For example, the average particle size is 50 μm or less. Further, the filler must be present in the film in an amount of 5 to 60% by weight. If it is less than 5%, there will be little improvement in moisture permeability.
Moreover, if it exceeds 60%, the mechanical strength and flexibility of the film will be impaired, making it unsuitable for use as a film. In addition, in order to ensure heat sealability when used as a packaging material, the content must be 60% or less. Films can be manufactured by melt extrusion or molding. In order to uniformly disperse the filler, it is desirable to create a masterbatch by mixing the filler with the polymer and then supplying this masterbatch to an extrusion molding machine to form a film. However, it is also possible to supply the polymer and filler to an extruder, mix them inside the extruder, and form the film by extrusion. The resulting film has moisture permeability and excellent heat seal strength. The thickness may be 5 to 300 μm, and the thickness and moisture permeability are approximately inversely proportional. Therefore, this film alone can be used as a packaging material for fruits and vegetables. It can also be used as a packaging material by laminating it on the inner surface of paper or nonwoven fabric. Alternatively, it can be used by laminating it on a moisture permeable film such as nylon. In either case, this film can be used as a heat seal layer. In addition to packaging materials for fruits and vegetables, it can also be used as packaging materials for desiccants and oxygen absorbers. (Example) Various fillers are blended into low-density polyethylene bereft, and a masterbatch is produced using a twin-screw extruder. Using this masterbatch, a film was formed using an extruder.
The extruder temperature is pellet injection part 160°C1 barrel 200°
~220℃, T die 220℃, screw rotation speed 8Or
pm, the take-up speed was 4.1 to 5.5 m/min, and the thickness of the obtained film was 100 μm. Table 1 shows the 33 humidity (g/m", 100 pm thickness, 24 hours) measured by the cup method (40°C) based on JIS Z 0280. Table 1 (Effects) As mentioned above, this book According to the invention, it is possible to obtain a film with excellent moisture permeability using a general-purpose polyolefin resin.Patent applicant Kazuo Suzuki, Representative of Toppan Printing Co., Ltd.

Claims (1)

[Claims] (1) A moisture-permeable film made of an olefin polymer or an olefin and other monomer copolymer containing 5% by weight or more of a filler selected from sodium sulfate, magnesium silicate, magnesium hydroxide, and diatomaceous earth.