JPS6211503A - Film for drying and filtration - Google Patents

Abstract

PURPOSE:To obtain a hydrophobic plastic film for drying and filtration having superior hydrophilic property and filtration performance being capable of removing quickly a wetting agent from the film when it is washed with water by using a water-soluble vinyl polymer as the wetting agent. CONSTITUTION:Hydrophobic resin such as polyether sulfone, etc. is formed to filtration film by a conventional film-forming method. After, then, dipping the filtration film in a soln. of water-soluble vinyl polymer such as aq. soln. of polyvinyl pyrrolidone, etc., the film is dried with hot air to obtain dry filtration film. The film obtd. by this process is wetted instataneously when it is dipped in water, and the wetting agent such as polyvinyl pyrrolidone is removed by washing with water. Since the acid resistance, alkali resistance, and heat resistance of the film are high, it is usable under severe conditions.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a dry filtration membrane made of hydrophobic resin, and more specifically, a water-soluble vinyl polymer is attached to the front, back, and/or inside of the membrane. , relates to a hydrophobic resin dry filtration membrane with highly improved hydrophilicity, filtration performance and mechanical strength.

Membrane separation technology has attracted attention for its energy saving and compactness, and has made remarkable progress. Various types of Girimer have been researched and developed as membrane materials for permselective separation membranes used in such systems, including cellulose,
Polymers such as polyamide, polyacrylonitrile, polycarbonate, polyphenylene oxide, and polysulfone are used.

Among them, hydrophobic polymers such as polysulfone, polycarbonate, polyphenylene oxide, and fluorine-containing polymers are originally used as engineering plastics, but they have excellent heat resistance and mechanical properties. Because of this, it is also being used as a material for separation membranes.

However, compared to hydrophilic fats such as cellulose acetate, hydrophobic resins such as polysulfone resins are extremely hydrophobic, and therefore become extremely water repellent, especially when formed into a dry filtration membrane. For this reason, the membrane becomes difficult to mix with water and often fails to exhibit sufficient filtration performance. Therefore, when producing a dry filtration membrane made of a hydrophobic resin such as polysulfone-based RI fat, some sort of hydrophilic treatment is required.

Note that the filtration membrane in the present invention refers to a precision filtration membrane having pores with a pore size of 100A or more and an ultrafiltration membrane having pores with a pore size of 100A or less.

Dry filtration membranes are much more convenient in terms of storage, transportation, processing, etc. than filtration membranes in a water-containing state.

[Prior art]

Conventionally, I! Methods for making an aqueous dry filtration membrane hydrophilic include: (1) A method of incorporating a hydrophilic substance such as glycerin, triacetin, polyethylene glycol, or hydroxypropyl cellulose into the membrane.

(2) A method of incorporating a surfactant into the film.

(3) A method of applying a water-insoluble hydrophilic polymer such as cellulose acetate to the surface of the filtration membrane (for example, British Patent No. 20
No. 81604).

(4) A method of grafting a hydrophilic hepatoma onto the surface of a filtration membrane (for example, US Pat. No. 4,340,482).

r5) By exposing the F' membrane to a plasma atmosphere to make it hydrophilic, for example, JP-A-Sho: srs 15g6G+)
・, d, etc. are known. When using the dry filtration membrane prepared by the method (1) or (old), first remove the hydrophilic substance or surfactant contained in it by washing with water. , need to be removed.

Therefore, it is preferable that the content of the hydrophilic substance or surfactant in the dry filtration membrane be as small as possible, since it can be removed more quickly. However, when using hydrophilic substances or surfactants such as glycerine, triacetin, polyethylene glycol, and hydroxypropyl cellulose, if their content is small, the hydrophilicity of the filtration membrane cannot be sufficiently increased, and the filtration Performance often deteriorates as well.

Therefore, it is necessary to contain a large amount of the above-mentioned hydrophilic substance or surfactant, but in such a case, it takes a lot of time and a large amount of water to wash the membrane, making it economical even in one hour. is also inconvenient. In particular, hydroxypropylcellulose has low solubility in water and is insoluble in hot water of 40° C. or higher, so it is not preferred as a wetting agent.

In the case of (3), the hydrophilicity of the membrane is increased, but the pores on the membrane surface are blocked, resulting in poor F4 permeability.

Method (4) is disadvantageous in that it often deteriorates the membrane surface condition and impairs filtration performance.

Method (5) is a relatively effective method.

Plasma processing equipment is expensive and consumes a lot of power, which poses cost problems and makes it difficult to put it into practical use.

[Object of the present invention]

The object of the present invention is to solve the above-mentioned problems.

The object of the present invention is to obtain a dry filtration membrane made of a hydrophobic resin that is excellent in hydrophilicity, filtration performance, and mechanical strength.

[Configuration of the present invention]

The present invention provides a dry filtration membrane produced by immersing a filtration membrane in a solution of a wetting agent and then drying the membrane, wherein the wetting agent is a water-soluble vinyl polymer. It is a membrane.

The hydrophobic resin referred to in the present invention is ASTM D570
A resin having a water absorption rate of 5% or less when immersed in water (23° C., 24 hr) according to the above method is preferably used. Examples of such hydrophobic resins are glysulfone, polyethersulfone, polyphenylene oxide, polycarbonate, polyacetal.

Examples include triacetate and Teflon.

Not limited to these.

In the present invention, a hydrophobic resin is molded into FM rattan using a known film forming method.

The shape of the membrane can be any shape that can be produced by a normal membrane manufacturing method, such as a flat membrane, a cylindrical membrane, or a hollow fiber membrane.

Then, this filtration membrane is immersed in a solution containing a water-soluble vinyl polymer and then dried to obtain a dry filtration membrane of the present invention.

The water-soluble vinyl polymer referred to in the present invention is obtained by polymerizing 1@1 or 2a or more of the vinyl monomers listed below, and is 0.2
It has the property of dissolving more than f.

(l Amides, such as vinylpyrrolidone, acrylic acid amide F, methacrylamide, etc.)

(2) It has a carboxyl group. For example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, etc.

(3) Contains a hydroxyl group. For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, m2-hydroxypropyl methacrylate, and the like.

(4) Vinyl acetate, ethylene, vinyl chloride, acrylonitrile, methacrylonitrile, chloroprene, isoprene, butadiene, vinylide ν, etc.

(5) Styrenes, styrene, methylstyrene, chloromethylstyrene, etc.

(6) Esters, such as methyl acrylate.

Methyl methacrylate, glycidyl acrylate.

Glycidyl methacrylate etc.

In addition, after polymerizing one or more of the above monomers, the water-soluble vinyl polymer of the present invention can also be obtained by carrying out a chemical treatment such as hydrolysis.〇 Raw water-soluble vinyl polymer Regarding the average molecular weight of the coalescence.

Although not particularly limited, 1G of water at 20 to 30℃ (0.2
The average molecular weight for dissolving f or more is preferably 1,000 or more and 1,000,000 or less.

When producing the dry r-permeable membrane of the present invention, the concentration of the solution of the water-soluble vinyl polymer used, the dipping time, the solution temperature, etc. are not particularly limited, but the content of the water-soluble vinyl polymer in the dry r-permeable membrane is not particularly limited. It is preferable to set conditions such that the ratio is 0.1% by weight or more and 30fiii% or less. The solvent for the water-soluble vinyl polymer solution may be water, alcohol, or any other solvent that dissolves the water-soluble vinyl polymer, but does not dissolve the filtration membrane material.

The drying process for producing the dry transient membrane of the present invention consists of fI
A known method such as air drying, vacuum drying, or natural drying at room temperature can be used.

[Effects of the present invention]

By using the water-soluble vinyl polymer of the present invention as a wetting agent, compared to conventional polymeric wetting agents such as polyethylene glycol and hydroxyethyl cellulose.

([) A dry transient membrane made of hydrophobic resin with better hydrophilicity and filtration performance is obtained.

(2) The wetting agent can be quickly removed from the membrane by washing with water.

This is an excellent effect.

In particular, in the case of a dry film made of polysulfone-based W resin, the resin has high mechanical strength and excellent acid resistance.

Due to the effects of the wetting agent of the present invention, alkali resistance and heat resistance are improved.
This makes it possible to use transient membranes under harsher conditions compared to conventional transient membranes such as cellulose acetate.
The industrial value is extremely large.

〔Example〕

Next, one embodiment of the present invention will be specifically explained with reference to examples.

Here, content W of water-soluble vinyl polymer or hydrophilic low molecule, filtration coefficient LP and bubble point) B, P,
is roared as follows.

Here, W is the weight of the dried transient membrane, and Wt is the weight when the dried transient membrane is washed with water to completely remove water-soluble vinyl polymers or hydrophilic low molecules and then re-dried. be.

B, P,... Based on the bubble point method of ASTM-B128.

Measured using pure water. The unit is amazing.

In addition, the estimated maximum pore diameter (μm) was determined from the following equation.

However, r: g surface tension cuff of water at 5°C 2 dynV/
611θ: Contact angle between hydrophobic glue finger and water, which is 78 for polyether sulfone.The strength and elongation at the breaking point were measured in the dry state for the dry filtration membrane.

Example 1 Polyether sulfone (trade name Vlctrex 48G
GF.

(manufactured by ICI) and 8 parts by weight of cylic acid were dissolved in 78 parts by weight of 2-pyrrolidone to obtain a uniform polymer solution. This was cast onto a glass plate to a thickness of 250 μm, left in a room temperature atmosphere for 30 seconds, immersed in room temperature water, peeled off from the glass plate, and washed with water.

The length of the temporary membrane to obtain the moisture-containing membrane is 5.6 m.
A/yriyr・rd・%, B, P are 3
．． 5%, therefore, was 0.17 μm. This film was made of polyvinylpyrrolidone (Aldri) with an average molecular weight of 10,000.
After immersion in an aqueous solution of

It was dried with hot air at 60° C. to obtain a dry filtration membrane containing 8.9 weight fIk% of W. When you put this film in water, it gets wet instantly.

Polyvinylpyrrolidone is removed by washing with water.

L, is 4.4 mt/yrtis -7-1J-91i
, B, P are 3.6 fi, therefore, is 0.17 μm
The filtration performance was extremely good.

Comparative Example 1 When the water-containing transient membrane used in Example 1 was directly dried with hot air at 60°C, the dried filtration membrane did not get wet with water at all, and L was 0.3 ml/1 m -t. The value was as low as /l-%.

Example 2゜14 parts by weight of the polyether sulfone used in Example 1 and 9 parts by weight of oxalic acid were dissolved in 77 parts by weight of 2-pyrrolidone,
A uniform polymer solution was obtained, which was cast onto a polyester film to a thickness of 300 μm, left in a room temperature atmosphere for 70 seconds, immersed in room temperature water, and then peeled off from the polyester film.

The membrane was washed with water to obtain a water-containing transient membrane. This temporary film (7)
Lp is 9.8 ml, 7mlx-, -d-%, B
, P, is 2.9%, so DMl-1,0,21μ
It was m. Also, the strength at the breaking point is 420 f/
j, elongation was 36%. This membrane was immersed in the polyvinylpyrrolidone aqueous solution of Example 1.

It was dried with hot air at 60° C. to obtain a dried transient film containing 2.7% by weight of W. When this membrane is immersed in water, it becomes wet instantly, and polyvinylpyrrolidone is removed by washing with water, and L is 9.5 mA.
/'m·dl-fi, B, P, was 3.5%, so 8 was 0.17 μm. In addition, the strength at the breaking point is 460 f/-1, and the elongation is 36%, and the filtration performance is 1
The mechanical strength was also extremely good.

Example 3 The water-containing temporary membrane used in Example 2 was immersed in an aqueous solution of polyacrylic acid (manufactured by Nippon Pure Chemical Industries, Ltd.) with an average molecular weight of 20,000, and then dried to obtain a solution containing 2.5% W. A dry filtration membrane of gk% was obtained. When this membrane is soaked in water, it shatters instantly, the polyacrylic acid is removed by washing with water, and the Lp is 11.5 ml/1m-
ad-%, B, P, is 2.7%, sub-v”CD,
It was 0.23 μm. In addition, the strength at the breaking point is 390 f/xJ, the elongation is 38%, and the filtration performance is 1.
The mechanical strength was also extremely good.

Comparative Example 2゜The hydrated temporary membrane used in Example 2 had an average molecular fit.
After soaking in an aqueous solution of 400 polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), it was dried to give a W content of 3.3%.
A dry filtration membrane was obtained. This film can be wetted with water when it is shed.<<,
L, is 7.4mt/mm'd'%, B, P, Ha1
．． 1%, therefore, the DM was 0.56 μm, and the resofiltration performance was significantly inferior to that of the original membrane in a water-containing state.

Example 4゜The hydrated temporary membrane used in Example 2 was immersed in the high concentration solution of polyvinylpyrrolidone used in Example 1, and then dried to obtain a dry temporary membrane containing 16% W. . This membrane instantly became wet with water, and polyvinylpyrrolidone in the membrane was quickly removed by washing with water. Also.

L, is 10.1 mA/l1ill ・cy!・M,
B, P, are 3.21. Follow me.

was 0.19 μm, and the filtration performance was good.

Example 5 A flat membrane (water-containing state) of polyethersulfone ultrafiltration membrane DO8-40 manufactured by Daicel Chemical Industries, Ltd. was immersed in the aqueous solution of polyvinylpyrrolidone used in Example 1, and then dried to change W to O, S. % dry filtration membrane was obtained. When this membrane is immersed in water, it becomes wet instantly, and polyvinylpyrrolidone is quickly removed by washing with water.

is 0.28 mt/rItix-al-M (4,Ot
l/m”-day/day).Also, ovalbumin (
When the exclusion rate of the molecule t14aOGO1 (manufactured by Wako Pure Chemical Industries, Ltd.) was determined by the following formula, it was 99% and %
The overflow performance was good.

Comparative Example 3 When the water-containing DU8-40 used in Example 5 was dried as it was, the dried film did not get wet with water at all.

L is also 1.9n? /m”・Japanese・Police, and FL overperformance was inferior.

Claims (2)

[Claims] (1) A dry filtration membrane produced by immersing a filtration membrane in a solution of a wetting agent and then drying the membrane, the dry filtration membrane made of a hydrophobic resin characterized in that the wetting agent is a water-soluble vinyl polymer. . (2) The dry filtration membrane according to claim 1, wherein the hydrophobic resin exhibits a water absorption rate of 5% or less when immersed in water according to ASTM D570.