JPH03290446A - Processing of porous film - Google Patents

Abstract

PURPOSE:To obtain a film suitable as a medical material, material of clothing, etc., arbitrarily controlling pore diameter of porous film, selectively providing function of solvent permeability, by subjecting a porous film to low-temperature plasma treatment under a specific condition. CONSTITUTION:The surface of a porous film containing >=10wt.%, preferably 20-40wt.% inorganic porous material consisting essentially of cristobalite is irradiated with low-temperature plasma in the presence of an inorganic or organic gas under 0.01-10Torr gas pressure. Polyolefin, polystyrene, polyester or cellulose may be cited as the film, the film thickness thereof is preferably 0.1-100mum, the controllable pore diameter range is 0.01-1,000mum and the pore diameter can be regulated in <=0.10mum accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a useful method in which the pore diameter of this porous film can be arbitrarily controlled and the function of solvent permeability can be freely and selectively imparted. It concerns a method for processing porous films.

Porous films are widely used as packaging materials, clothing materials, etc. due to their selective permeation function, but in recent years there has been a demand for high-performance porous films with even higher gas separation and molecular separation capabilities. There is a need for a processing method that not only allows the size of the pores to be controlled, but also allows for selectively imparting the function of solvent permeability.

Various types of polymer films containing inorganic porous materials have been developed, including those in which zeolite, activated carbon, Oya stone, etc. are kneaded into the polymer film. In addition, it has inorganic porous gas adsorption, deodorizing, and antibacterial properties. The conventional processing method for this film involves pulverizing these existing inorganic porous materials to a particle size of 1 to several 10 μm, kneading it into a polymeric material and molding it using an inflation method, etc. The pore diameter of the film itself and high functionality such as solvent permeability, moisture permeability, and gas separation function are determined by the molding conditions.

As mentioned above, the conventional method is to arbitrarily change the diameter of the pores of the porous film and the associated functionality by changing the molding conditions such as kneading an inorganic porous material with a uniform particle size. .

On the other hand, by post-processing the porous films that have been molded to date, it is possible to freely and selectively impart the pore size of the film itself and high functionality such as solvent permeability, moisture permeability, and gas separation function. Porous films in particular have poor solvent permeability. Furthermore, it has been difficult to control the pore diameter of existing inorganic porous materials themselves. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for processing a porous film that solves the problems of conventional processing techniques, allows easy arbitrary control of the pore diameter, and is useful for processing porous films.

In order to solve these drawbacks, the present inventors focused on the future potential of porous films and high-performance porous films with gas separation ability and molecular separation ability. As a result of intensive and extensive systematic research into freely and selectively imparting functionality, we found that high-performance properties such as the pore size and solvent permeability of the film itself can be achieved by performing low-temperature plasma treatment on the surface of the porous film. The present invention was achieved based on the discovery that the desired effect can be obtained by freely and selectively imparting the desired effect.

It is well known that low-temperature plasma etches and decomposes the surface area of a material within a range of a few to several thousand koostomes, and that the activation of the material surface is determined by the type of gas used during low-temperature plasma treatment. be. Focusing on this phenomenon, by applying low-temperature plasma treatment to the surface of a porous film containing fine powder of cristobalite, a type of silica-based porous material, it is possible to expand the pore diameter of the film itself by etching and activating the film. , and it was possible to freely and selectively impart high functionality such as solvent permeability.

The processing process of the porous film of the present invention using such low temperature plasma treatment is very different from conventional ones. That is, in the conventional method, the size of the pore diameter of the porous film was determined by the molding conditions before film production. On the other hand, in the method of the present invention, it was possible to determine the plasma treatment conditions after forming the porous film.

It is well known that porous films cannot be obtained by simply plasma treating a film. In addition, Jikai Vi56-90838 states, ``As a result of plasma treatment of a polypropylene porous film, the surface of the material became hydrophilic, and even though the pore size could be increased, water permeability could not be achieved.'' By subjecting the surface of a porous film containing 10% by weight or more of fine powder of cristobalite, a type of silica-based porous material, to low-temperature plasma treatment and etching, the pore diameter of the film itself is further expanded and the permeability of solvents is increased. We discovered this phenomenon and arrived at the present invention.

The above phenomenon did not occur with porous films containing less than 101% by weight of fine cristobalite powder and porous films containing inorganic compounds other than cristobalite (for example, zeolite, CaC◯, etc.).

An object of the present invention is to provide a useful porous film in which the pore diameter of the porous film can be arbitrarily controlled by a low-temperature plasma treatment method, and in which a solvent permeability function can be freely and selectively imparted. The objective is to provide a processing method for

The porous film used in the present invention is made of a polymeric material, such as polyolefins such as polypropylene, polyethylene, polybutadiene, polystyrene, polyester, cellulose, and polysaccharides. A blend of materials is also acceptable. The cristobalite dispersed in the above polymeric material is a silica-based natural porous mineral, and most preferably has a particle size in the range of 1 μm to 100 μm. Its content is 10% or more, but 2
The film thickness is preferably 0% to 40%, 0.1 μm
to 100 μm is preferable.

In addition, the shape is not only film-like, but also non-woven fabric, paper, l
A laminate with ll1 fiber etc. may also be used.

By subjecting the porous film material of the present invention to low-temperature plasma treatment, the surface region of the material is etched and activated at the same time, making it possible to expand the pore size of the film itself and to improve functionality such as solvent permeability. can be given freely and selectively.

Solvents include water, aqueous solutions of solutes (inorganic and organic compounds), organic solvents such as alcohol and benzene, and mixed solvents thereof.

The determining factors of the low-temperature plasma processing conditions for etching and activating the surface area of the material are the gas composition, pressure, and flow rate, as well as the output power and processing time, which determine the water permeability of the porous film. It is determined.

The plasma gas of the present invention is nitrogen, nitrogen, or hydrogen.

Argon, neon, helium, air, water! ! These include chlorine, ammonia, carbon oxide, carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and chlorofluorocarbons, as well as polymerizable plasma gases.

These can be used alone or in combination.

In particular, inorganic gases are effective for increasing the water permeability of porous films, and fluorocarbon-based organic gases are effective for increasing the permeability of nonpolar solvents.

To quickly achieve the object of the present invention, it is desirable to create an atmosphere in which the partial pressure of the low-temperature plasma processing gas is 50) torr or less, more preferably 5 x 10 -z torr or less. In a plasma atmosphere with a partial pressure greater than 20 Torr, the effectiveness of plasma processing decreases rapidly. The flow rate of the plasma gas is determined by the volume of the reactor and the partial pressure of the plasma gas.

Although the output is generally 500 watts or less, it is possible to obtain the desired performance by combining it with the processing time.

The plasma processing time varies depending on the type and shape of the material, the processing equipment, etc., but is usually from several seconds to several tens of minutes, preferably from about 5 minutes to 15 minutes.

When applying plasma gas to the surfaces of plastic materials and glass materials, many combinations are possible. That is, various choices can be made, such as the structure of the reactor, the type of power source, frequency, discharge format, and electrode position.

For plasma processing, high frequency (13,5
6MH2), microwave (2,45GHz) - low frequency (
As a discharge method, glow discharge is effective. ! l! Regarding the position of the electrodes, there are internal and external types, but the internal type is easier to operate in terms of uniformity of effect.

By combining the above plasma treatment conditions such as gas type, gas flow rate, output, and treatment time, it is possible to perform treatment to any pore size.

It is more effective to extend the treatment time under an output of 200 WJX as much as possible, as this allows the pore diameter to be expanded without impairing the shape of the film.

The plasma treatment time is 1 to 3600 seconds, preferably 1 to 1800 seconds.

When plasma gas is applied to the film surface, various choices can be made such as the structure of the reactor, the type of power source, the frequency, the discharge method, the position of the electrodes, etc., and there are no particular limitations.

The range of the pore diameter of the film that can be controlled in the present invention is from 0.01 μm to 1000 μm, and can be controlled with an accuracy of 0.10 μm or less.

Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 Polypropylene porous films containing 10 and 30.40% by weight of cristobalite were treated with low-temperature plasma, respectively.

The plasma processing conditions: The plasma processing equipment uses a high frequency generator to
A glow discharge internal electrode type was used in which a constant voltage was applied through a matching box with a high frequency of MHz. First, the sample from the previous period was suspended in a glass plasma chamber, and after the chamber was sufficiently degassed, the sample was heated to 0.05 Torr.
Oxygen gas or fluorocarbon gas was introduced to the pressure of r. Thereafter, plasma discharge was performed for 30 to 600 seconds at an output of 50 to 300W.

Next, the surface of the plasma-treated porous film and the untreated porous film was analyzed using a scanning electron microscope (SEM) and a porosimeter. * Using a glass filtration device, distilled water, ethanol, and benzene were
The amount of permeation was measured after pouring 0ml and leaving it for 30 minutes under atmospheric pressure.

The results of these measurements are shown in Tables 1-3.

Comparative Examples Polyolefin porous film containing 5% by weight of cristobalite (Ichiiina NC Film), polyolefin porous film containing 5% by weight of zeolite (Ichihara Uniace), polyolefin containing 5% by weight of Oya stone system porous film (commercial name: FH film), C
A polyolefin film containing 15% by weight of aCO5 (Ichihara Breathable Film) and a polyolefin porous film containing no inorganic porous material (commercially available Meiko Suboar) were each subjected to plasma treatment in the same manner as in Example 1. The solvent permeability was also measured in the same manner. The results are shown in Table 4.

Margin below.

Table 1 Solvent permeability of plasma-treated porous film (containing Krysto A-Lite) Table 2 Effect of plasma output on solvent permeability Sample: Krysto A-Lite 30wt%1
[Porous film with polypropylene] Plasma treatment conditions (gas type = 02. Gas flow rate: 20 m1/1st
in, processing time: 180 sec) Table 3 Effect of plasma processing time on solvent permeability *) Plasma processing conditions (output: 300III, gas flow 1k: 20II 1st/min, processing time: 180 sec) - Unmeasurable - Sample: cristobalite 30 wt% 1 [polypyropylene-based porous film, plasma treatment conditions (gas type = 02, gas flow rate: 20 m1/lll1n, output crab 30 1st) - Engraved discord table 4 Plasma treated porous film ( Solvent permeability of inorganic porous material (containing inorganic porous material) Example 1: Christker 94130w
t% content 1 reflow phosphorus-based porous film) Plasma treatment conditions (gas type: 02. Output 300W,
Gas flow rate: 20 1st/Un, processing time: 180se
c) ・Surface condition: O: expansion of pores, O: change in surface shape such as protrusion of porous material, x: no change. From the above, a porous film containing 10% by weight or more of cristobalite has a low-temperature plasma on the surface. It was confirmed that the treatment enlarges the pores and increases solvent permeability. Furthermore, it has been found that the pore diameter can be controlled by selecting plasma treatment conditions.

In addition, polyolefin porous films containing 5 wt% cristobalite, 5 wt% zeolite, and 5 wt% otani stone, and polyolefin porous films containing no inorganic porous material, do not survive low-temperature plasma treatment on their surfaces. No pore expansion was observed, and it was not possible to increase solvent permeability. Furthermore, 15 wt% Ca
In the COI-containing polyolefin porous film, pore expansion was observed, but as in Example 1, the solvent permeability could not be increased.

The processing method for porous film in the basic invention allows the pore size of the film to be precisely adjusted by changing the plasma treatment conditions, and also allows for water permeability, non-water permeability, moisture permeability, and gas permeability. High functions such as bone ant can be freely and selectively imparted.

Furthermore, this plasma treatment is a dry process that can be performed in a short time, which is labor-saving. In addition, since secondary processing of the amount of molding is possible, repeated processing can be performed. Through this processing method, the pore size is controlled to the micron order according to the purpose, and the film can be widely used as a separating film with high selective permeability in medical materials, clothing materials, packaging materials, fuel cell matrices, industrial materials, etc. .

Furthermore, it can be expected to be used as a carrier that can immobilize biological samples of a desired size.

Claims (1)

[Scope of Claims] 1. A method for processing a porous film, characterized by subjecting the surface of the porous film to low-temperature plasma treatment to increase solvent permeability. 2. The method for processing a porous film according to claim 1, wherein the porous film is a polymer film containing 10% by weight or more of an inorganic porous material. 3. Low-temperature plasma treatment is performed at a gas pressure of 0.01 to 10 torr.
4. The method of processing a porous film according to claim 1, which comprises low temperature plasma irradiation carried out in the presence of inorganic and organic gases. 4. The first claim in which the solvent is water, an aqueous solution, or an organic solvent
Processing method of porous film described in Section 1. 5. The method for processing a porous film according to claim 2, wherein the inorganic porous material is a porous material containing cristobalite as a main component.