JP2013000633A - Method for manufacturing porous membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a porous membrane by which a high-performance porous membrane is manufactured without deteriorating the water permeability even when the porous membrane is manufactured by using a highly hydrophobic material.SOLUTION: The method for manufacturing a porous membrane includes depositing a porous membrane made of a hydrophobic resin containing halogen atoms and subsequently applying a solution containing a moisturizer and a surfactant onto the front surface of the porous membrane. As the moisturizer, glycerin, polyglycerin, polyvinyl alcohol, ethylene glycol, propylene glycol, polyethylene glycol, xylitol, diglycerin, dipropylene glycol, sorbitol, and 1,3-butylene glycol, etc., are taken. As the surfactant, sodium lauryl sulfate, lauryl trimethylammonium chloride, and polyoxyethylene alkyl ether, etc., are taken.

Description

  The present invention relates to a method for producing a porous membrane, and more particularly to a method for producing a porous membrane including a treatment after the formation of the porous membrane.

Conventionally, for example, water treatment membranes made of polymer materials have been used to purify water such as turbidity of river water and groundwater, clarification of industrial water, drainage and sewage treatment, and pretreatment of seawater desalination. Yes.
Such a water treatment membrane is used as a separation membrane in a water treatment apparatus. For example, polysulfone (PS), polyethylene (PE), cellulose acetate (CA), polyacrylonitrile (PAN), polyvinyl alcohol These are hollow fiber-like porous membranes, composite semipermeable membranes, and the like formed of various polymer materials such as (PVA) and polyimide (PI).

  When such hollow fiber-like porous membranes or composite semipermeable membranes are used in a modular form, it is advantageous to dry these membranes in terms of processability and storage stability. May cause a decrease in permeation flux and / or salt rejection. Therefore, methods for applying a drying inhibitor, a humectant, etc. to the surfaces of the porous membrane and the composite semipermeable membrane have been proposed (for example, Patent Documents 1 and 2).

However, as described in these patent documents, the use of a drying inhibitor and / or a humectant for the porous membrane material is particularly effective for the porous membrane made of a highly hydrophobic material. On the other hand, there has been a case in which a decrease in the permeation flux cannot be avoided.
Further, the above method requires special treatment such as ethanol washing after drying the hydrophobic membrane.

JP 2000-271451 A JP 2008-93543 A

  The present invention has been made in view of the above problems, and a method for producing a high-performance porous membrane without reducing water permeability even when producing a porous membrane using a highly hydrophobic material. The purpose is to provide.

  The method for producing a porous membrane of the present invention includes forming a hydrophobic porous membrane and then bringing a solution containing a humectant and a surfactant into contact with the surface of the porous membrane. To do.

In this method for producing a porous membrane, it is preferable to include one or more of the following.
(1) The moisturizing agent is selected from polyhydric alcohols, and the surfactant is selected from water-soluble surfactants having affinity for the hydrophobic resin.
(2) The humectant is selected from the group consisting of glycerin, polyglycerin, polyvinyl alcohol, ethylene glycol, propylene glycol, polyethylene glycol, xylitol, diglycerin, dipropylene glycol, sorbitol and 1,3-butylene glycol. One or more.
(3) The surfactant is a surfactant made of an aqueous solution and exhibiting a static contact angle of 0 to 30 ° with respect to the hydrophobic resin.
(4) The surfactant is one or more selected from the group consisting of sodium lauryl sulfate, lauryl trimethyl ammonium chloride, and polyoxyethylene alkyl ether.
(5) The hydrophobic resin is a halogen atom-containing resin.
(6) The hydrophobic resin is a vinyl chloride resin or a fluorine resin.

  According to the present invention, even when a porous membrane is manufactured using a highly hydrophobic material, a high-performance porous membrane capable of ensuring high water permeability can be manufactured by a simple and easy method. .

  In the method for producing a porous membrane of the present invention, first, a porous membrane made of a hydrophobic resin is formed, and then a solution containing a humectant and a surfactant is brought into contact with the surface of the porous membrane.

The porous membrane of the present invention is formed of a hydrophobic resin.
For example, as a material for the porous membrane, any material having high hydrophobicity is effective in the present invention. Vinyl chloride type; olefin type such as polyethylene and polypropylene; fluorocarbon type such as polyvinylidene fluoride; sulfone type Any of acrylonitrile-based and imide-based resins may be used.
Here, the “hydrophobic resin” includes, for example, a resin having a property of exhibiting a static contact angle of 70 to 90 ° when a 30% by weight aqueous solution of glycerin is dropped on the resin surface. The static contact angle can be measured by any commercially available contact angle measuring device.
Among these, it is particularly advantageous to use a resin known to have higher hydrophobicity by containing a halogen atom.
Examples of the halogen atom-containing resin include vinyl chloride resins and fluorine resins, and vinyl chloride resins are particularly advantageous.

  Examples of the vinyl chloride resin include vinyl chloride homopolymer (homopolymer), a copolymer of a monomer having an unsaturated bond copolymerizable with vinyl chloride monomer and vinyl chloride monomer, and a vinyl chloride monomer grafted onto the polymer. Examples thereof include polymerized graft copolymers, (co) polymers composed of chlorinated vinyl chloride monomer units, and the like. These may be used alone or in combination of two or more.

  The monomer having an unsaturated bond copolymerizable with the vinyl chloride monomer is not particularly limited, and (meth) acrylic acid derivatives such as methyl (meth) acrylate and ethyl (meth) acrylate; α-olefins such as ethylene Vinyl esters such as vinyl acetate; vinyl ethers such as butyl vinyl ether; aromatic vinyls such as styrene; vinylidene chloride vinyl vinyl chlorides; N-substituted maleimides such as N-phenylmaleimide; These may be used alone or in combination of two or more.

  The polymer to be graft-copolymerized to vinyl chloride is not particularly limited as long as it can be graft-polymerized to vinyl chloride. For example, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-carbon monoxide copolymer Examples include coalescence. These may be used alone or in combination of two or more.

  Furthermore, (meth) acrylic acid esters of polyhydric alcohols such as ethylene glycol di (meth) acrylate; acrylamides such as N-methylallylacrylamide; divinyl compounds such as divinylbenzene; at least two allyls in the diallyl phthalate molecule A polyallyl compound such as an allyl etherified product of sucrose having an ether unit; a crosslinkable monomer such as a (meth) acrylic acid ester of an unsaturated alcohol such as vinyl (meth) acrylate may be used.

  Further, a hydrophilic monomer may be copolymerized in order to impart stain resistance to the porous membrane. Examples of the hydrophilic monomer include monomers having an amino group, an ammonium group, a hydroxyl group, a carboxyl group, a sulfonic acid group, and the like.

As the fluorine-based resin, any known one can be used, and means a resin having at least one fluorine atom in the polymerization repeating unit.
Examples thereof include homopolymers or copolymers of perfluoroalkyl (meth) acrylate, copolymers of alkyl (meth) acrylate and perfluoroalkyl (meth) acrylate, and the like. Specific examples include “Teflon (registered trademark) AF1600” (trade name) and “Teflon (registered trademark) AF2400” (trade name) manufactured by DuPont.

As a method for forming the porous film, any method known in the art may be used. Examples thereof include a thermally induced phase separation method, a non-solvent phase separation method, and a stretching method.
In addition, when forming a porous membrane, you may use various additives well-known in the said field | area.
In this porous membrane, the average pore diameter is, for example, about 0.001 to 10 μm, preferably about 0.01 to 1 μm. The porosity is, for example, about 10 to 90%, preferably about 20 to 80%. The form is not particularly limited, and examples include generally known shapes such as a hollow fiber shape, a flat membrane shape, a spiral shape, a pleated shape, a monolith shape, and a tubular shape. Among these, a hollow fiber shape or a tubular shape is preferable. In this case, for example, the outer diameter of the hollow fiber membrane is about 900 to 3000 μm, the inner diameter is 500 to 2000 μm, and in the case of a tubular shape, the inner diameter is 2 to 15 mm, the wall thickness is about 100 to 1000 μm, and the inner diameter is about 900 to 3000 μm. About 500-2000 micrometers is mentioned.

  Further, the porous membrane preferably has a single layer structure. Here, having a single layer structure means being formed from a single material. Usually, a material with low strength cannot maintain a desired shape, for example, a cylindrical shape, a tube shape, or the like, unless it is a composite material with a support formed from a stronger material (ceramic, nonwoven fabric, etc.). . Therefore, conventionally, when this porous membrane is used as a water treatment membrane, a cylindrical ceramic or a non-woven fabric formed into a cylindrical shape is used as a structure supporting the membrane so that a desired shape is not crushed. It was. On the other hand, in the present invention, the support is formed of a material other than the hydrophobic halogen atom-containing resin so as not to change a desired shape such as a cylindrical shape, which is formed only of a single layer structure film. Preferably, even such a single-layer structure has sufficient strength to maintain a desired shape such as a cylinder or tube shape when used as a water treatment membrane, that is, "self-supporting" The thing which has is preferable.

After forming the porous film, a solution containing a humectant and a surfactant is applied to the surface of the porous film.
The humectant is not particularly limited as long as it can achieve humectation / water retention, but is preferably selected in consideration of the use of the porous membrane. For example, polyhydric alcohol, urea, amino acid, hyaluronic acid, polysaccharide and the like can be mentioned. In particular, polyhydric alcohols are preferable in terms of viscosity, water retention, and cost. Specifically, it is selected from the group consisting of glycerin, polyglycerin, polyvinyl alcohol, ethylene glycol, propylene glycol, polyethylene glycol, xylitol, diglycerin, dipropylene glycol, sorbitol, 1,3-butylene glycol and the like. These may be used alone or in combination of two or more.

As the surfactant, a water-soluble surfactant having an affinity for the above-described highly hydrophobic resin (for example, a hydrophobic halogen atom-containing resin) is preferably supplied as an aqueous solution. Specifically, an aqueous solution of a surfactant that exhibits a static contact angle of 0 to 30 ° with respect to the hydrophobic resin described above is preferable.
Here, “affinity” means a material having a static contact angle of 0 to 30 ° with respect to a hydrophobic resin (for example, a hydrophobic halogen atom-containing resin or a film-shaped surface).
Specifically, anionic surfactants such as sodium lauryl sulfate, cationic surfactants such as lauryltrimethylammonium chloride, nonionic surfactants such as polyoxyethylene alkyl ether, amphoteric surfactants such as petine, etc. Can be mentioned. These may be used alone or in combination of two or more. Of these, sodium lauryl sulfate, lauryltrimethylammonium chloride and polyoxyethylene alkyl ether are preferable.

In a solution containing such a humectant and a surfactant, the humectant and the surfactant are preferably contained in an amount of 10 to 70% by weight: 0.1 to 20% by weight based on the total solution, What contains glycerin: sodium lauryl sulfate by 10 to 70 weight%: 0.1 to 20 weight% is more preferable.
By including both components in such a range, it is possible to ensure appropriate affinity and moisture retention even for a highly hydrophobic porous membrane, and to maintain excellent water permeability. .

The solution containing the humectant and the surfactant may be diluted with water or a suitable solvent. For example, examples of the solvent include lower alcohols such as methanol and ethanol. Of these, water is preferred.
Furthermore, this solution may contain ethanol, formalin, hypochlorous acid and the like (hereinafter referred to as “ethanol etc.”). By containing ethanol or the like, the storage stability can be improved, for example, by preventing the growth of bacteria in the solution itself. The content of ethanol or the like here is, for example, about 10% or less with respect to the total solution weight.

A method for applying a solution containing a moisturizing agent and a surfactant to the surface of the porous film is not particularly limited, and examples thereof include a gravure coating method, a roll coating method, a spray coating method, a lip coating method, and a comma coating. A coating method such as a coating method, a coating method such as a printing method such as a gravure printing method or a screen printing method may be used, or a porous film may be immersed in this solution. Especially, since it is simple, the method of immersing is preferable.
It is preferable that the immersion time is appropriately adjusted so that the solution penetrates not only into the porous membrane surface but also into the inside depending on the immersion time. For example, it is suitable to end within about 24 hours, and it is preferable to end within about 12 hours.
Although the temperature at the time of application | coating is not specifically limited, Since the component used volatilizes depending on temperature and it is thought that a composition changes, when considering the heat resistance of resin, it is 0-90. It is preferable to carry out at a temperature in the range of about 0 ° C., particularly 20 to 60 ° C.

After applying a solution containing a humectant and a surfactant on the surface of the porous membrane, the obtained porous membrane is usually dried.
Drying can be performed by a method known in the art. For example, hot air drying, vacuum drying, or the like may be performed, or natural drying may be performed. Accordingly, the drying temperature may be in the range of about 10 to 80 ° C. in consideration of the heat resistance of the resin, and is preferably about 20 to 60 ° C. or about 0 to 40 ° C.

The porous membrane production method of the present invention, in particular, after the porous membrane is formed, the solution containing the specific component described above is brought into contact with the surface thereof, so that the porous membrane that has been dried thereafter is also permeable to water. There is no loss of sex. Therefore, it is not necessary to separately subject the dried porous membrane to washing with alcohol or the like, and a high-performance porous membrane that ensures water permeability can be easily produced.
The contact may be performed by any method known in the art, such as coating, spraying, or dipping using various devices.

Hereinafter, the manufacturing method of the porous membrane of this invention is demonstrated in detail by an Example.
Example 1
Sekisui Chemical's chlorinated vinyl chloride resin (product number “HA05K”) and polyethylene glycol (molecular weight 4000) are dissolved in dimethylacetamide at a ratio of 18:17:65 and discharged continuously from a hollow fiber nozzle. A porous hollow fiber membrane was obtained by phase separation at. The obtained hollow fiber-like membrane had an inner diameter of 1 mm and an outer diameter of 1.4 mm (hereinafter, the hollow fiber-like membrane at this point is referred to as “pre-drying hollow fiber-like membrane”)
Next, an aqueous solution containing 20% by weight of glycerin and 10% by weight of sodium lauryl sulfate was prepared, and the obtained hollow fiber membrane was immersed in this solution for 12 hours.
The hollow fiber membrane was taken out from the solution and allowed to stand at room temperature and normal pressure for 24 hours to dry the solution naturally.
The hollow fiber membrane was measured for pure water permeability before and after drying under the conditions of 25 ° C. and transmembrane pressure difference 100 kPa.
The recovery rate was determined from the pure water permeability before and after drying according to the following formula.
Recovery rate = (pure water permeability after drying) / (pure water permeability before drying) × 100
The results are shown in Table 1. The recovery rate in Example 1 was 97.2%.

Examples 2-8
A porous membrane was produced in the same manner as in Example 1 except that the composition and / or the solution soaking time of glycerin as a humectant and sodium lauryl sulfate as a surfactant were changed. Similarly, pure water permeability Was measured. The results are shown in Table 1.

Comparative Example 1
A porous membrane was produced in the same manner as in Example 1 except that an aqueous solution of 30% by weight of glycerin was used as the solution in which the hollow fiber membrane was immersed.
About the obtained film | membrane, the water permeability was not confirmed when the pure water water permeation performance was measured after drying similarly to Example 1.
Therefore, the porous membrane obtained after drying was immersed in an aqueous solution of 75% by weight of ethanol for 3 hours for cleaning, and then water permeation was attempted again. As a result, almost 100% recovery was observed.

Comparative Example 2
A porous membrane was produced in the same manner as in Example 1 except that an aqueous solution containing 10% by weight of sodium lauryl sulfate was used as the solution in which the hollow fiber membrane was immersed.
About the obtained membrane | film | coat, the water permeability of a pure water was measured after drying similarly to Example 1, but water permeability was not confirmed.

From the results shown in Table 1, only with the treatment with glycerin as a moisturizing agent, water permeability was not confirmed after drying in a porous membrane made of a vinyl chloride resin, and it was necessary to wash with an aqueous ethanol solution after drying.
On the other hand, as in the present invention, by applying an aqueous solution mixed with glycerin as a moisturizing agent and sodium lauryl sulfate as a surfactant to the surface of the porous membrane, water permeation can be performed without any special treatment after drying. I was able to confirm.

  INDUSTRIAL APPLICABILITY According to the present invention, it can be used in the production of porous membranes used for microfiltration membranes, ultrafiltration membranes and the like.

Claims (7)

After forming a porous film made of a hydrophobic resin,
A method for producing a porous membrane, comprising bringing a solution containing a humectant and a surfactant into contact with the surface of the porous membrane.   2. The method for producing a porous membrane according to claim 1, wherein the humectant is selected from polyhydric alcohols, and the surfactant is selected from water-soluble surfactants having affinity for the hydrophobic resin.   The humectant is one or more selected from the group consisting of glycerin, polyglycerin, polyvinyl alcohol, ethylene glycol, propylene glycol, polyethylene glycol, xylitol, diglycerin, dipropylene glycol, sorbitol and 1,3-butylene glycol. The method for producing a porous membrane according to claim 1 or 2.   The porous membrane according to any one of claims 1 to 3, wherein the surfactant is an aqueous solution and is a surfactant that exhibits a static contact angle of 0 to 30 ° with respect to the hydrophobic resin. Manufacturing method.   The said surfactant is 1 or more types selected from the group which consists of sodium lauryl sulfate, lauryl trimethyl ammonium chloride, and polyoxyethylene alkyl ether, The manufacture of the porous membrane as described in any one of Claims 1-4. Method.   The method for producing a porous film according to claim 1, wherein the hydrophobic resin is a halogen atom-containing resin.   The method for producing a porous membrane according to claim 6, wherein the hydrophobic resin is a vinyl chloride resin or a fluorine resin.