JPS587449B2 - Method for manufacturing porous membrane shaped article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a porous membrane shaped article.

Porous membrane-like molded products suitable for use as filtration membranes have been provided in the past, but the manufacturing method for these porous membrane-like molded products is to use a membrane made of an olefin resin and a finely powdered inorganic substance. Hot-rolling the shaped molded product in one or more axial directions at an appropriate temperature within a temperature range lower than the melting temperature of the olefin resin and higher than the softening temperature of the olefin resin, A method of manufacturing a porous membrane-like molded article is known.

However, in order to create enough porosity to use this method as a filtration membrane, it is necessary to disperse an extremely large amount of finely powdered inorganic material into the olefinic resin. However, there was a drawback that the mechanical strength of the shaped molded product was reduced.

The present invention solves the above-mentioned drawbacks, and in addition to the filtration membrane,
The present invention provides a method for manufacturing a porous membrane-like molded product suitable for electrode separators of storage batteries, air/moisture permeable membranes, etc.

The gist of the present invention is a method for producing a porous film-like molded product, which comprises cold-stretching a film-like molded product made of an olefinic resin and a finely powdered inorganic substance, and then further hot-stretching the film-like molded product.

The manufacturing method of the present invention will be explained in detail below.

The olefin resin that forms the film-like molded product includes olefin homopolymers such as polyethylene, polypropylene, polybutene, polybutylene, and poly4-methylpentene-1, ethylene-propylene copolymers, ethylene-butene copolymers, Copolymers of olefins and monomers copolymerizable with them, such as ethylene-vinyl acetate copolymers, ethylene-vinyl chloride copolymers, glopyrene-butene copolymers, and ethylene-ethyl acrylate copolymers; It is preferable to use one or a mixture of two or more modified olefin resins such as chlorinated polyethylene and chlorosulfonated polyethylene.

In addition, the olefin resin includes one or more thermoplastic resins selected from styrene resins, vinyl chloride resins, vinyl acetate resins, acrylic acid resins, polycarbonate resins, phenoxy resins, etc. May be added.

The finely powdered inorganic substance used in the present invention includes:
Silica powder, diatomaceous earth powder, carbon powder, mica powder, coal powder, graphite powder, barium sulfate powder, calcium hydroxide powder, calcium carbonate powder, magnesium hydroxide powder, barium hydroxide powder, barium titanate powder, titanium oxide powder, etc. It is preferable to select and use one or more types.

The particle size of the inorganic substance is preferably 20μ or less, and optimally 5μ or less.

The finely powdered inorganic substance is preferably used in an amount of 5 to 500 parts by weight per 100 parts by weight of the olefin resin.
Optimally, 10 to 300 parts by weight are used.

In the present invention, pigments, lubricants, heat stabilizers, plasticizers,
Surfactants, antioxidants, antistatic agents, etc. can be used.

Further, in the present invention, a material made of an olefin resin and a finely powdered inorganic material, preferably having a thickness of about 0.05 mm to 3 mm, and most preferably a thickness of 0.1 mm to 1 mm. However, these film-like molded products are first cold-stretched in uniaxial or biaxial directions at an appropriate temperature lower than the softening temperature of the olefin resin.
Microscopic cracks occur at the interface between the olefin resin and the finely powdered inorganic substance.

Next, the film-like molded product with microscopic cracks caused by cold stretching is
Fine cracks are formed in the pores by hot stretching in uniaxial or biaxial directions at an appropriate temperature within a temperature range higher than the softening temperature of the olefin resin and lower than the melting temperature of the olefin resin. It grows and becomes a porous film-like molded product.

The porous film-like molded article usually has a pore diameter of 0.1 to 10μ, but the amount of the finely powdered inorganic material used, the particle size of the finely powdered inorganic material, and the stretching during the cold stretching and hot stretching The pore diameter can be adjusted by selecting the magnification and the like.

Moreover, most of the pores generated in the film-like molded product penetrate from one side of the film-like molded product to the other side.

Conventionally, in order to create sufficient porosity in a film-shaped molded product made of olefin resin and finely powdered inorganic material to be used as a filtration membrane, a very large amount of finely powdered inorganic material was added to the olefin resin. However, according to the present invention, a film-like molded product made of an olefin resin and a finely powdered inorganic substance has micro cracks at the interface between the olefin resin and the finely powdered inorganic substance due to the cold stretching process. The microscopic cracks are easily and effectively grown into pores during the subsequent hot rolling process, so it can be used as a filtration membrane simply by dispersing a small amount of finely powdered inorganic material in the olefin resin. A film-like molded product made of an olefinic resin and a finely powdered inorganic substance can be produced with sufficient porosity to achieve this.

Next, examples of the present invention will be described below.

Example 1 100 parts by weight of a polypropylene resin and 20 parts by weight of calcium carbonate having a typical particle size of 0.1 μm were kneaded using a heated roll to form a film-like molded product with a thickness of 200 μm.

The film-like molded product thus obtained was applied to a uniaxial stretching machine and cold-stretched at a stretching ratio of 1.2 times in the uniaxial direction at room temperature, and then applied to a biaxial stretching machine and stretched to 4 times in each of the biaxial directions at 150°C. Hot stretching was performed at the same magnification.

As a result of observing the thus obtained porous membrane-like molded product using a scanning electron microscope, the pore diameters were distributed in the range of 0.1μ to 1μ, and most of the pores were located on one side of the porous membrane-like molded product. It was confirmed that it penetrated from one side to the other side.

This porous membrane shaped product had excellent water permeability and was suitable as a filtration membrane.

At the same time, as Conventional Example 1, the same film-like molded product as used in Example 1 was produced by the conventional method, omitting the cold stretching step, and directly applied to a biaxial stretching machine at 150°C to 4 times the thickness in each of the two axial directions. The air permeability of the porous membrane molded product thus obtained was compared with the air permeability of the porous membrane molded product obtained in Example 1.

The results are shown in Table 1. Example 2 Ethylene-vinyl acetate copolymer (ethylene content: 60
weight%) 100 parts by weight and 30 parts of silica powder with a typical particle size of 1μ
A film-like molded product with a thickness of 500 μm obtained by kneading and molding parts by weight using an extruder was applied to a biaxial stretching machine, cold-stretched at room temperature in each direction at a stretching ratio of 1.1 times, and then applied to a biaxial stretching machine. , and hot stretching was carried out at 80° C. in both biaxial directions at a stretching ratio of 6 times.

As a result of observing the thus obtained porous membrane-like molded product using a scanning electron microscope, the pore diameters were distributed in the range of 0.5μ to 3μ, and most of the pores were located on one side of the porous membrane-like molded product. It was confirmed that it penetrated from one side to the other side.

This porous membrane shaped product had excellent water permeability and was suitable as a filtration membrane.

At the same time, as Conventional Example 2, the same film-like molded product used in Example 2 was produced by a conventional method, omitting the cold stretching step, and directly applied to a biaxial stretching machine to be stretched 6 times in each of the two axial directions at 80°C. The air permeability of the porous film-like molded product thus obtained was compared with the air permeability of the porous film-like molded product obtained in Example 2.

The results are shown in Table 2. As described above, the present invention provides a method for producing a porous film-like molded product that easily and effectively creates pores by adding a cold stretching step to a conventional method for producing a porous film-like molded product. Furthermore, the products produced according to the present invention have a wide range of uses, including not only as filtration membranes but also as electrode separators for storage batteries, air-permeable and moisture-permeable membranes, etc.

Claims (1)

[Claims] 1. A method for producing a porous film-like molded product, which comprises cold-rolling a film-like molded product made of an olefin resin and a finely powdered inorganic substance, and then hot-stretching it.