JPS60250049A - Production of microporous filter membrane composed of polysulfone - Google Patents

Abstract

PURPOSE:To obtain a microporous filter membrane having excellent thermal stability, by dissolving a polysulfone resin in a mixture of a low-boiling good solvent and a high-boiling poor solvent, casting the soln., evaporating the good solvent and causing the soln. to become turbid and to gel to thereby forming micropores. CONSTITUTION:A polysulfone resin of formula I or II (wherein X1-X6 are each alkyl, halogen; l1-l6 are each 0-4) is homogeneously dissolved in a mixture of a low-boiling good solvent for the resin (e.g. methylene dichloride) and a high- boiling poor solvent for the resin (e.g. methyl ethyl ketone). The resulting homogeneous soln. is cast and the good solvent is gradually evaporated to thereby cause the soln. to become turbid and to gel, whereby micropores can be formed and the desired microporous filter membrane composed of polysulfone is obtained. The resulting filter membrane is stable against a high-pressure steam sterilization treatment and suitable for use in a pharmaceutical field.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a microporous filtration membrane, and more particularly, to a microporous filtration membrane with improved stability against autoclaving by % and a method for manufacturing the same.

(Prior art) Microporous sheets have been known for a long time (for example, R,
Kesting, “5yntbe ti cPoly
mer Membrane JMcGraw Hi11
Publication) Widely used in filtration filters, etc. Microporous sheets are described, for example, in U.S. Pat.
No. 1, No. 3. /33, No. 13, same λ.

Hatll, 0/7 issue, Tokko Sho ≠ 3-11 & 9g issue, Tokko Sho 4t! -JJ,? /J issue, same 1it-j sit issue,
As described in 4t11'-jooso, etc., it is produced using cellulose ester as a raw material.

However, microporous sheets made from cellulose acetate are very unstable at high temperatures, so their use has been limited. For example, a drug whose main ingredient is cellulose ester? Microporous sheets used for filtering are usually sterilized before use, but if a heat sterilization method such as high-pressure steam is used, the filtration rate of the sheet is significantly reduced. Therefore, special and limited methods are required to sterilize microporous sheets containing cellulose ester as the main component (
For example, gas sterilization) can only be used, and its use in the pharmaceutical industry has therefore been severely limited.

The present invention was developed to solve these drawbacks.

Polysulfone resin has attracted attention as a material for microporous filtration membranes that is stable against high-pressure steam sterilization, and methods for manufacturing microporous filtration membranes using polysulfone resin have been proposed.

Unexamined Japanese Patent Publication No. 34-/! μ03/ is a polysulfone resin that dissolves in good solvents such as poppymethylformamide and dioxane, as well as alcohols and ethers.

By adding an appropriate amount of a non-solvent such as a ketone, a "meta-stable" dope that separates into two phases when left standing for several days is created. This is a method of creating a porous membrane. In this method, when the membrane is immersed in the coagulation bath, the membrane shrinks rapidly, making it impossible to form a clean membrane. Furthermore, since the resulting membrane forms a skin layer with a thickness of λ to 3 μm and few openings on its surface, the filtration resistance increases and the filtration rate decreases.

Tokukai Akira! A dope is prepared by dissolving Hiro-λ42JrJi polysulfone resin in an aprotic polar solvent such as dimethylformamide or dimethylsulfoxide, and adding polyethylene glycol having a molecular weight of 100 or more to the solution. After this dope is cast onto a support, it is immersed in a water coagulation bath to form a microporous membrane.

In this method as well, the membrane shrinks significantly in the deicing and coagulating bath, significantly impairing the quality of the membrane. In addition, the diameter of the pores formed is almost the same between the front and back, resulting in a symmetrical membrane. A membrane with no difference in pore size between the front and back sides is used for filtration, and only the primary surface of the nine-sided membrane contributes to filtration, so it has the drawback of being susceptible to clogging.

(Object of the Invention) The present invention was developed to solve the respective drawbacks of conventional cellulose ester filtration membranes and polysulfone filtration membranes.

Therefore, the first object of the present invention is to provide a method for producing a microporous filtration membrane with excellent thermal stability. It is on offer. The microporous filtration membrane referred to here has a pore diameter of 0.0/μ to /Qμ, especially o, orμ.
Effective for removing bacteria, fungi and viruses from SOμ to 3μ, porosity from 30% to 20%, membrane thickness from SOμ to 230μ
The second object of the present invention is to use μ particles whose pore size changes continuously from the front side to the back side, and when the liquid is filtered from the side with the larger pore size, it will not clog. The front and back are asymmetrical, making it difficult to cause problems.

Moreover, it is a so-called 1 skin with many surface pores! - To provide a microporous filtration membrane and a method for producing the same.

(Means for Solving the Problems) As a result of various studies carried out by the present inventors, the above-mentioned object of the present invention is to create a homogeneous solution (dope After the purple flow spread,
We have discovered that this can be achieved by gradually volatilizing a low-boiling point good solvent while controlling the environmental temperature and gas concentration sound, thereby phase-separating the cydope, turning it cloudy, and then gelling it to form a microporous filtration membrane. In the method of the present invention, gelation of the membrane is carried out gradually in the air, so that the rapid contraction of the membrane that occurs in previous polysulfone filtration membrane manufacturing techniques does not occur. Therefore, a defect-free film with excellent thermal stability can be obtained.

Polysulfone resins that can be preferably used in the present invention include polymers having repeating units represented by the following general formula CI).

CI) (II) However, X 1- X 2h X 3, x4. Xs and X
6 may be the same or different and each represents an alkyl group or a halogen atom. Alkyl groups and [7] are preferably methyl or ethyl groups.

zi, 12-za% t4, t5 and t6 are each O-
≠ represents an integer.

The molecular weight of the polysulfone resin used in the present invention is preferably 11,000,000, and particularly preferably λ to j0,000.

Specific examples of the polysulfone resin represented by the general formula 1''I) or [II) of the present invention include the following structures.Commercially available products include UDELP-/7oo and UDELP-7oo from Union Carbide Co., Ltd. -J!00 and Imperial Chemical's VICTREX2ooP, same 3
0oP! I can list several things.

What is a good low boiling point solvent for the polysulfone resin used in the present invention? ! It is a solvent that can dissolve at least 1% by weight, preferably at least 1% by weight, and also has a low boiling point as the subsolvent used at the same time.

The difference in boiling point between the two is preferably 20c'C or more.

Examples of low boiling point good solvents include halogenated hydrocarbons such as methylene dichloride and chloroform, and cyclic ethers such as tetrahydrofuran and dioxane.

The poor solvent for the polysulfone resin used in the present invention is a solvent that dissolves the polysulfone resin by 3% by weight or less, or does not dissolve it at all but can swell it, and also has a high boiling point as the good solvent used at the same time. It is something.

Examples of high boiling point poor solvents for poly-sulfone are methyl ether ketone and diacetone alcohol.

Ketones and alcohols such as n-butanol and impropatol, esters such as butyl acetate and inamyl acetate, preferably ethers such as ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, diethylene glycol monoether ether, and polyethylene. ' Glycol and polypropylene glycol are used. Among them, polyethylene glycol and polyethylene glycol become the most preferable high-boiling point poor solvent when combined with tetrahydrofuran as a good solvent. Furthermore, water can be used in combination with the above-mentioned poor solvents in an amount of less than 3% of the total dope amount.

When polysulfone resin is uniformly dissolved in these solvents (
The aroma of the polysulfone resin in the dope of this solution (referred to as r-dope) is preferably j-/4% by weight, especially f,/-% by weight, and the amount of the high boiling point poor solvent is 21.6% by weight.
It is preferable that the amount of the solvent is 3λ~μr, and the amount of the low boiling point good solvent is 33 to 79% by weight, especially ao-t.
o It is preferable that it is related to weight.

The high boiling point poor solvent/polysulfone resin ratio is 3 to t%, especially 3.
3-j is preferred.

Furthermore, a hygroscopic agent or a surfactant may be added to the dope to improve its affinity with water. Glycerin and diglyceride are used as moisture absorbers, and anionic surfactants such as higher carboxylates, higher alcohol sulfate ester salts, polyethylene glycol ether sulfate ester salts, alkylaryl sulfonates, and phosphate ester salts are used as surfactants. , cationic surfactants such as amine salts and ammonium salts, amphoteric surfactants such as dodecylaminoethylglycine hydrochloride, alkyl ethers, alkyl allyl ethers, sorbitan monoalkyl esters, polyoxyethylene alkyl amines.

Polyoxyethylene alkylamide, polyethylene oxide, polypropylene oxide, saccharose ester, fatty acid ethanolamide, methylolamide,
Nonionic surfactants such as glycosides are used.

The dope thus prepared is cast onto a support and gradually dried at a temperature below the boiling point of the good solvent. Preferably, the boiling point of the good solvent is p30-jooC, especially 4to~
Dry for 20440 minutes at 4t♂0C low @ production, especially for 30 to SO minutes. When most of the good solvent (for example, 10% or more) has evaporated and the film turns into a white gel, micropores have already been formed in the film. However, since a large amount of poor solvent remains in the trench, the temperature must be adjusted to remove the poor solvent. Either dry it (for example, at a temperature higher than the poor solvent for 5 minutes or more, especially at a temperature higher than 10 °C for 1Q minutes or more), or wash it with a solvent that dissolves the poor solvent, such as water or alcohol. Is there a membrane here to remove the poor solvent? Does it already gel even after soaking in water? Because of the drying process, the membrane caused significant shrinkage, and there was a significant change in pore size. I won't wake you up.

The present invention will be further explained below with reference to Examples.

Example 1 Polysulfone (trade name UDELP-3so.

(manufactured by Union Carbide Company)
of polyethylene glycol≠rove to make a homogeneous solution. This homogeneous solution is applied onto a polyester sheet of approx.
When the polysulfone solution was cast to a thickness of θO μm and dried for 30 minutes at 20C without airflow, the cast polysulfone solution caused phase separation and then formed micropores. did. When air drying was carried out in this way for more than QJO minutes, the formation of micropores was completed. After the formation of micropores, the membrane was peeled off from the polyester sheet, and the polyethylene glycol residue remaining in the membrane was washed away with running water.

When the surface of the membrane thus formed was observed with a scanning electron microscope, the pore diameter on the side that was in contact with the polyester sheet was about three times larger than the pore diameter on the opposite side, with an average of about 0. They were 1 μm and 0.12 μm. Also, the water permeation rate of this membrane is / J'ml /min/cm'' (ip
The overpressure was 7 atm, and the water temperature was xO', c).

Example 2 Polysulfone 100? , polyethylene glycol 0
The average surface pore size (on the surface opposite the polyester sheet) of the membrane prepared from a homogeneous solution of 11tetrahydrofuran-02 is o,rμm.

The water permeation rate was 70 ml/Cm 27 min. The materials used, the membrane manufacturing method, and the evaluation method were the same as in Example 1.

Example 3 Polysulfonta Of, polyethylene glycol 3409
The surface average pore size (on the surface opposite to the polyester sheet) of a membrane made from a homogeneous solution consisting of tetrahydrofuran Jrot is 3 μm%, and the water permeation rate is 1 μOml/C.
It was rn2/min. The materials used, the membrane manufacturing method, and the evaluation method were the same as in Example 1.

Preferred embodiments of the invention are as follows.

l) The good solvent with a low boiling point in the claims is a cyclic ether.

λ) A good solvent with a low boiling point in the claims is tetrahydro-7rane.

3) The high boiling point poor solvent in the claims is chain ethers or chain ethers and water.

The high boiling point poor solvent in the claims is polyethylene glycol or polyethylene glycol and water.

j)! In the claims, the good solvent is tetrahydrofuran, and the poor solvent is polyethylene glycol or polypropylene glycol.

6) Within the scope of the claims, a microporous filtration membrane made by turning a solution into a cloudy state and gelling at 7C, washing with a poor solvent of a high boiling point solvent polysulfoshi resin, and then further drying, and a method for producing the same.

Claims (1)

[Claims] After casting a homogeneous solution consisting of a polysulfone resin, a good solvent with a low boiling point for the polysulfone resin, and a good solvent with a high boiling point for the polysulfone resin, the low boiling point good solvent is gradually evaporated,
A method for producing a polysulfone microporous filtration membrane, which comprises forming micropores by making the solution cloudy and gelling.