JP2000093766A - Water resistant hydrophilic microporous membrane and its manufacturing method - Google Patents

Abstract

(57) [Problem] To provide a microporous membrane that withstands long-term use and does not lose hydrophilicity even when drying and wetting are repeated, and a method for producing the same. SOLUTION: A microporous membrane made of a water-repellent material is immersed in a solution containing a hydrophilic substance having a functional group capable of forming a complex with a metal to form a hydrophilic microporous membrane, which is a polyvalent metal. The present invention relates to a water-resistant hydrophilic microporous membrane which is immersed in a solution containing ions to insolubilize the hydrophilic substance, thereby achieving water resistance, and a method for producing the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-resistant hydrophilic microporous membrane and a method for producing the same. More specifically, the present invention can withstand long-term use and does not lose its hydrophilicity even after repeated drying and wetting. The present invention relates to a water-resistant hydrophilic microporous membrane and a method for producing the same.

[0002]

2. Description of the Related Art It is essential that a microporous membrane used for filtration or electrolysis of water withstands long-term use and does not lose its hydrophilicity even after repeated drying and wetting.

A large number of microporous membranes used for water filtration, electrolysis, and the like are made of various materials, and are roughly classified into those made of a hydrophilic material and those made of a water-repellent material. You. An example of the former is a cellulose acetate membrane, which has the advantage that it can be used without special treatment because the material itself has hydrophilicity, but has the physical and chemical strength of the material itself. However, there is a drawback in that care is required for handling because of its small size. On the other hand, examples of the latter include various membranes such as polyolefins such as polyethylene and polypropylene, vinyls such as polyvinyl chloride and polyvinylidene fluoride, and engineering plastics such as polysulfone, and physical and chemical strength and purpose of use. It has the advantage of being able to use differently according to the conditions, but has the disadvantage of requiring pretreatment for imparting hydrophilicity to the material itself.

Various methods have been developed for pretreatment for imparting hydrophilicity to the above-mentioned water-repellent material, and practical use has been attempted. One is to apply a surfactant to a microporous membrane made of a water-repellent material and dry it to make it hydrophilic. As another method, a hydrophilic group is chemically bonded to a water-repellent material to make it hydrophilic.

[0005]

The above-mentioned microporous membrane made of a hydrophilic material has a drawback that it cannot withstand long-term use because of its low physical and chemical strength. In a microporous membrane made by applying a surfactant to a microporous membrane made of and drying and hydrophilizing the surfactant, the surfactant is soluble, so the surfactant is eluted with long-term use and the hydrophilicity is lost In the case of a microporous membrane made hydrophilic by chemically bonding a hydrophilic group to a water-repellent material, there is a drawback that the process for each material is different or complicated.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that a water-resistant treatment is carried out on a hydrophilic microporous film obtained by hydrophilizing a microporous film made of a water-repellent material. It is a hydrophilic microporous membrane, whereby a microporous membrane that can withstand long-term use can be obtained.

Further, the invention according to claim 2 is characterized in that the water-repellent hydrophilic microporous membrane according to claim 1 contains a surfactant or a hydrophilic filler in the water-repellent material and insolubilizes the surfactant or hydrophilic filler. Thereby, it is possible to obtain a microporous membrane that can prevent elution of the surfactant or the hydrophilic filler.

Further, the invention according to claim 3 comprises a step of hydrophilizing a microporous membrane made of a water-repellent material to obtain a hydrophilic microporous membrane, and a step of subjecting the hydrophilic microporous membrane to a water resistance treatment. This is a method for producing a water-resistant hydrophilic microporous membrane, whereby the microporous membrane can be easily hydrophilized and subjected to a water-resistant treatment.

According to a fourth aspect of the present invention, in the method for producing a water-resistant hydrophilic microporous membrane according to the third aspect, the step of obtaining the hydrophilic microporous membrane includes the step of forming the hydrophilic microporous membrane from a water-repellent material with a hydrophilic substance. Wherein the step of immersing the hydrophilic microporous membrane in a water-repellent treatment is a step of insolubilizing the hydrophilic substance attached to the hydrophilic microporous membrane. This is a method for producing a microporous membrane, whereby the process of making the microporous membrane hydrophilic and performing a water resistance treatment can be simplified.

[0010] According to a fifth aspect of the present invention, in the method for producing a water-resistant hydrophilic microporous membrane according to the third aspect, the step of obtaining the hydrophilic microporous membrane comprises a repellent containing a surfactant or a hydrophilic filler. The step of forming a film using an aqueous material, wherein the step of performing a water-resistant treatment on the hydrophilic microporous membrane is a step of insolubilizing a surfactant or a hydrophilic filler attached to the hydrophilic microporous membrane. This makes it possible to obtain a microporous membrane that withstands long-term use and does not lose its hydrophilicity even after repeated drying and wetting.

According to a sixth aspect of the present invention, in the method for producing a water-resistant hydrophilic microporous membrane according to the fourth aspect, the solution containing a hydrophilic substance is a solution containing a hydrophilic polymer compound. This is a method for producing a water-resistant hydrophilic microporous membrane, which makes it easy to hydrophilize the microporous membrane.

According to a seventh aspect of the present invention, in the method for producing a water-resistant hydrophilic microporous membrane according to the sixth aspect, the solution containing the hydrophilic polymer compound has a functional group capable of forming a complex with a metal. This is a method for producing a water-resistant hydrophilic microporous membrane, characterized by being a solution containing, whereby a microporous membrane capable of maintaining hydrophilicity for a long period of time can be obtained.

According to the invention of claim 8, in the method for producing a water-resistant hydrophilic microporous membrane according to claim 7, the substance having a functional group capable of forming a complex with a metal is sodium carboxymethylcellulose or a derivative thereof. This is a method for producing a water-resistant hydrophilic microporous membrane, whereby a microporous membrane capable of easily maintaining hydrophilicity for a long period of time can be obtained.

[0014] The invention according to claim 9 provides the invention according to claims 3 to
8. In the method for producing a water-resistant hydrophilic microporous membrane according to any one of items 8, the step of performing a water-resistant treatment on the hydrophilic microporous membrane includes immersing the hydrophilic microporous membrane in a solution containing polyvalent metal ions. This is a process for producing a water-resistant hydrophilic microporous membrane, which is characterized in that the process is a step, whereby the hydrophilic polymer compound can be stabilized.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on its embodiments.

A feature of the water-resistant hydrophilic microporous membrane according to the embodiment of the present invention is that a hydrophilic microporous membrane obtained by hydrophilizing a microporous membrane made of a water-repellent material is subjected to a water-resistant treatment. As the water-repellent material, a polyolefin-based material such as polyethylene and polypropylene, polyvinyl chloride, a vinyl-based material such as polyvinylidene fluoride, and a microporous film made of an engineering plastic-based material such as polysulfone in a solution containing a hydrophilic substance. Impregnated or made hydrophilic by adding a surfactant or a hydrophilic filler to the above-described water-repellent material to form a film, and the hydrophilic substance, surfactant or hydrophilic filler is further insolubilized. .

Further, a feature of the method for producing a water-resistant hydrophilic microporous membrane according to the embodiment of the present invention is that a step of hydrophilizing a microporous membrane made of a water-repellent material to obtain a hydrophilic microporous membrane, Subjecting the hydrophilic microporous membrane to a water-resistant treatment.The step of obtaining a hydrophilic microporous membrane comprises immersing the microporous membrane made of a water-repellent material in a solution containing a hydrophilic polymer compound, Alternatively, it is to form a film using a water-repellent material containing a hydrophilic filler, and the step of subjecting the hydrophilic microporous membrane to a water-resistant treatment includes a hydrophilic substance, a surfactant, or a surfactant attached to the hydrophilic microporous membrane. This is to insolubilize the hydrophilic filler.

The hydrophilic polymer compound used in the above-mentioned process for producing the water-resistant hydrophilic microporous membrane has a functional group capable of forming a complex with a metal, such as sodium carboxymethylcellulose (CMC) or a derivative thereof. Preferably, the substance is a substance. In order to easily penetrate the substance into a microporous membrane made of a water-repellent material, a water-soluble organic solvent such as alcohol is added to an aqueous solution of sodium carboxymethylcellulose (CMC) or a derivative thereof. Good to use.

In the above-mentioned method for producing a water-resistant hydrophilic microporous membrane, various surfactants or hydrophilic fillers to be contained in the water-repellent material at the time of film formation may be used depending on the use of the microporous membrane. Can be used.

The water-resistant treatment of the hydrophilic microporous membrane used in the above-mentioned method for producing a water-resistant hydrophilic microporous membrane is performed by treating the hydrophilic microporous membrane with a divalent or trivalent material such as calcium, aluminum or iron. It is preferable to immerse in a solution containing a valent metal ion.

Next, in the above-mentioned method for producing a water-resistant hydrophilic microporous membrane, a microporous membrane made of a water-repellent material is treated with sodium carboxymethylcellulose (CM
After immersion in the solution containing C), after immersion in the solution containing divalent or trivalent metal ions such as calcium, aluminum and iron, the solution containing sodium carboxymethylcellulose (CMC) After immersion and drying, it may be immersed in a solution containing divalent or trivalent metal ions such as calcium, aluminum and iron. In the latter case, a small amount of surfactant is added to the water-repellent material. By adding the surfactant or adding a small amount of a surfactant to a solution containing sodium carboxymethyl cellulose (CMC), the surface tension of the microporous membrane can be reduced. It can be uniformly attached to the surface of the microporous membrane. In this case, since the surfactant is not used for hydrophilizing the microporous membrane, the addition amount may be small.

In the above method for producing a water-resistant hydrophilic microporous membrane, the microporous membrane made of a water-repellent material is immersed in a solution containing sodium carboxymethylcellulose (CMC). In other applications, the polymer may be immersed in a solution containing another substance having a functional group capable of forming a complex with a metal such as sodium polyacrylate or a derivative thereof as a hydrophilic polymer compound.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on its embodiments.

A sample obtained by cutting a microporous membrane made of polypropylene having an average pore size of 0.2 μm into a size of 10 cm × 10 cm, and a treatment solution A obtained by dissolving 10 g of sodium carboxymethylcellulose in a mixed solvent of 300 g of special grade ethanol and 700 g of water. A processing solution B prepared by dissolving 30 g of ferric sulfate in 70 g of water is prepared. The sample is immersed in the processing solution A for 5 minutes, then continuously immersed in the processing solution B for 60 minutes, and washed with tap water for 10 minutes. After drying in a hot air dryer set at 40 ° C. for 60 minutes, take out and float on water,
It was found that it absorbed water instantly and was completely wet.

Then, even when the above test was repeated 10 times with the same sample, it was found that water was absorbed instantaneously and completely wetted.

[0026]

As described above, according to the present invention, the hydrophilicity can be maintained even when drying and wetting are repeated, so that a water-resistant hydrophilic microporous membrane that can withstand long-term use can be obtained. Can be.

Claims (9)

[Claims] 1. A water-resistant hydrophilic microporous film obtained by subjecting a hydrophilic microporous film obtained by hydrophilizing a microporous film made of a water-repellent material to a water-resistant treatment. 2. The water-resistant hydrophilic microporous membrane according to claim 1, wherein the water-repellent material contains a surfactant or a hydrophilic filler and is insolubilized. film. 3. A water-resistant hydrophilic microporous membrane comprising: a step of hydrophilizing a microporous membrane made of a water-repellent material to obtain a hydrophilic microporous membrane; and a step of subjecting the hydrophilic microporous membrane to a water-resistant treatment. Recipe. 4. The method for producing a water-resistant hydrophilic microporous membrane according to claim 3, wherein the step of obtaining the hydrophilic microporous membrane comprises immersing the microporous membrane made of a water-repellent material in a solution containing a hydrophilic substance. Wherein the step of subjecting the hydrophilic microporous membrane to a water-resistant treatment is a step of insolubilizing a hydrophilic substance attached to the hydrophilic microporous membrane. 5. The method for producing a water-resistant hydrophilic microporous membrane according to claim 3, wherein the step of obtaining the hydrophilic microporous membrane is performed using a water-repellent material containing a surfactant or a hydrophilic filler. Wherein the step of subjecting the hydrophilic microporous membrane to a water-resistant treatment is a step of insolubilizing a surfactant or a hydrophilic filler attached to the hydrophilic microporous membrane. Recipe. 6. The method for producing a water-resistant hydrophilic microporous membrane according to claim 4, wherein the solution containing a hydrophilic substance is a solution containing a hydrophilic polymer compound. Recipe. 7. The method for producing a water-resistant hydrophilic microporous membrane according to claim 6, wherein the solution containing a hydrophilic polymer compound is a solution containing a substance having a functional group capable of forming a complex with a metal. A method for producing a water-resistant hydrophilic microporous membrane. 8. The method for producing a water-resistant hydrophilic microporous membrane according to claim 7, wherein the substance having a functional group capable of forming a complex with a metal is sodium carboxymethylcellulose or a derivative thereof. Production of porous microporous membrane. 9. The method for producing a water-resistant hydrophilic microporous membrane according to any one of claims 3 to 8, wherein the step of subjecting the hydrophilic microporous membrane to a water-resistant treatment comprises: A method for producing a water-resistant hydrophilic microporous membrane, which is a step of immersion in a solution containing metal ions.