KR20070091401A - Method for manufacturing polyethersulfone membrane by air coagulation - Google Patents

Abstract

A method for manufacturing a polyethersulfone membrane having proper filtrating efficiency, high flux and improved service cycle is provided, and a method for manufacturing a polyethersulfone membrane, which establishes the reproducibility of asymmetrical cross-sectional structure and physical properties of the polyethersulfone membrane more stably, is provided. A method for manufacturing an asymmetrical polyethersulfone membrane comprises the steps of: providing a solution prepared by dissolving polyethersulfone into a solvent; uniformly mixing a non-solvent and hydrophilic material and a pore-adjusting reaction catalyst with the polymer solution; casting the uniform solution on a continuous support and exposing the cast solution to circulated air having proper temperature and humidity, thereby solidifying the solution; and extracting a non-solidified compound from a polyethersulfone solidified body. The membrane has an average substantial pore size of 0.01 to 2.0 mum. The circulated air has a temperature ranging from 20 to 65 deg.C and a humidity ranging from 30 to 80%. The air is ejected at a rate of 1 to 20 m/min according to the pore size. The membrane has a porosity of 70% or more. The reaction catalyst includes an epoxy-based compound.

Description

 Method for manufacturing polyethersulfone membrane by air coagulation method {Method for manufacturing Polyethersulfone membrane by air coagulation}

The present invention relates to a method for producing a membrane by the air coagulation method that has a moderate filtration efficiency, can improve the use cycle and express high flow properties.

Polyethersulfone resins are used in general-purpose membranes that are widely used in the field of water treatment in areas other than industrial fields where acid resistance and alkali resistance chemical resistance are required together with polysulfone resins. Since ancient times, various methods for producing a variety of membranes have been introduced. Looking at the prior art to which the invention belongs as follows.

U. S. Patent No. 5,886, 059, which is based on a wet coagulation method, discloses a method for producing a membrane having an asymmetric cross-sectional structure with a pore size difference of 50: 1 on the front and back sides. According to this, after mixing a polyether sulfone and a solvent, a non-solvent is added uniformly. The solution is cast on a support, exposed to air for 2 seconds, and then coagulated in a coagulation bath to give an asymmetric membrane with a practical pore size in the range of 0.05 to 2 μm.

U. S. Patent No. 5,906, 742 also discloses a membrane having a microporous asymmetric structure, which is based on a wet coagulation method, in which a sulfon polymer and a hydrophilic polymer are mixed and cast. The pores of this membrane range on average from 1 to 5 μm, using polyethersulfones and polyarylsulfones as sulfone polymers and polyvinyl-pyrrolidone as hydrophilic polymers. The thickness of the densely packed layer is about 15-25% of the membrane thickness. In the manufacturing method, the sulfon polymer concentration was 8-14%, the solution of hydrophilic polymer concentration 5-25% was cast as a thin film, and the cast film was exposed for 5 seconds to 35 seconds at a relative humidity of 50-80%. . Then, the temperature is solidified in the range of 30 to 70 ℃.

The method described in US Pat. No. 6,056,903 relates to the preparation of symmetrical membranes with microporosity without the formation of dense surface layers, polyethersulfone polymers, solvents, aliphatic glycols having a range of 2 to 20 carbon atoms. After casting a solution containing on a support, it is exposed to the atmosphere. Subsequently, the membrane is prepared by passing a coagulation bath containing water and aliphatic glycol, washing with water and drying. As described, this is also based on wet coagulation.

US Pat. No. 6,565,782 relates to a method for producing an asymmetric membrane having an average particle diameter of 0.1 to 10 μm with a pore size difference of 5 to 1,000 times between the front and back sides, and the method described in US Pat. No. 5,906,742. Almost similar. Therefore, it is based on the wet coagulation method.

As shown in the prior art, the manufacturing method of the polysulfone and polyether sulfone membranes differs in the polymer solution composition, but from the viewpoint of the manufacturing process, most of the symmetric or asymmetric membranes are manufactured based on wet coagulation.

However, when the conventional polyether sulfone or polysulfone membrane is manufactured by the wet coagulation method, there is a problem in that high flow rate and a decrease in the service life appear. In addition, the conventional wet coagulation method has low reproducibility of the cross-sectional shape and physical properties of the membrane.

Therefore, there is a need for a new method of reproducibly producing a polyethersulfone membrane having a proper filtration efficiency required by the industry and dramatically improving performance of a high flow rate and a low cycle of use.

The present invention is to solve the problems according to the prior art as described above, an object of the present invention is to provide a method for producing a polyether sulfone membrane having a moderate filtration efficiency, improved flow rate and life cycle.

Another object of the present invention is to provide a method for producing a polyether sulfone membrane in which the asymmetric cross-sectional structure of the polyether sulfone membrane and the reproducibility of physical properties are more stably established.

In order to achieve the above object, the present invention provides a step of dissolving a polyether sulfone in a solvent; Uniformly mixing a non-solvent, a hydrophilic material, and a pore control reaction catalyst with the polymer solution; Casting the homogeneous solution onto a continuous phase support and solidifying by exposure to circulating air (AIR) having a suitable temperature and humidity; Provided is a method of making an asymmetric polyether sulfone membrane, comprising extracting uncoagulated compound from a polyethersulfone coagulant.

In the production method, the membrane is preferably a practical pore size in the range of 0.01 to 2.0 ㎛ average.

In another aspect, the circulating air preferably has a temperature in the range of 20 to 65 ° C. In addition, the circulating air preferably has a humidity in the range of 30 to 80%.

In the process of the invention, the air is injected at a speed in the range of 1-20 m / min, depending on the pore size.

In addition, the membrane of the present invention is an asymmetric structure, having a porosity of 70% or more.

The reaction catalyst preferably contains an epoxy compound.

Hereinafter, the present invention will be described in detail.

The cross-sectional structure of the micropores formed in the membrane can be largely divided into symmetrical structure and asymmetrical structure. The double, symmetrical structure can obtain a high flow rate by controlling the porosity, but the cycle of use decreases gradually. Therefore, an asymmetrical structure is advantageous in order to have a high filtration efficiency and to prevent a high flow rate and a decrease in the use cycle, and the present invention provides a method for easily manufacturing such an asymmetrical structure.

To this end, a polymer, a solvent, a non-solvent, and a reaction catalyst are used as a basic composition, and a prescription design for controlling the composition ratio of the solvent / non-solvent, the polymer concentration, and the pore size of the surface by the reaction catalyst, and a temperature having an appropriate range of gradients, The surface of the coating liquid in contact with air is solidified by spray circulating the moisture-containing air in contact with the surface of the coating liquid, and the back side of the coating liquid on the support forms relatively dense pores to form a desired asymmetry. It is possible to produce a membrane having a cross-sectional structure.

In more detail, during the solidification process, the film forming speed is 0.2 m / min, the temperature gradient range is 20 to 65 ° C., and the humidity range is 30 to 80%. At this time, not only the temperature and humidity of the circulating air but also the injection speed are controlled, and the reaction catalyst contained in the coating liquid controls the reaction between the air and the surface of the coating liquid to adjust the evaporation rate of the solvent and the non-solvent in the coating liquid. It is possible to produce a microporous homogeneous membrane having a pore size. In addition, the control of porosity can ensure high porosity by completely extracting the solvent and non-solvent remaining in the washing process after air coagulation.

It is.

Specifically, to prepare a polyether sulfone membrane having fine pores having an asymmetric structure, first, an organic compound and a solvent capable of dissolving them are added to the polyether sulfone resin to prepare a mixed solution.

Next, the non-solvent, the hydrophilized material and the pore control catalyst are uniformly mixed with the solution.

The crude solution is cast on a polyester film support and then formed using a temperature / humidity gradient to form a partially solidified membrane.

By immersing the resulting membrane in water or an alcohol mixed solution, the uncoagulated organic compound is dissolved and extracted from the coagulated membrane to form micropores.

Suitable solvents for use in the present invention may be known general purpose solvents or two or more types of mixed solvents. However, the direct factor for making the micropores of the asymmetric structure must be the addition of appropriate additives.

As a solvent of the polyether sulfone used in the present invention, an organic material capable of plasticizing and hydrophilicity and dissolving polyether sulfone resin well in order to make many effective pores that can interpenetrate into the membrane which is primarily subjected to solidification by circulating air. Solvent.

What is important when making a porous membrane is that the polyethersulfone polymer should be mixed very uniformly, and the added organic compounds should be effectively discharged when extracted with water or alcohol mixed solution in the washing process.

As a solvent capable of dissolving both the polyether sulfone polymer and the organic compound, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide, dimethylacetamide (DMAc) or a mixture thereof This is preferable.

The above-mentioned organic compounds may be acetate, ether, alcohol, ketone, ester or mixtures thereof, and these organic compounds may be contained in a proportion of 6 to 25 parts by weight based on 100 parts by weight of the polyether sulfone resin crude liquid composition. It is suitable to mix.

According to the present invention, the additive is characterized by a composition of an addition catalyst which controls the evaporation reaction rate of the non-solvent by an acetate compound, an alcohol compound and circulating air which can be chemically uniformly mixed but not easily separated.

 For example, butyl acetate, polyethylene glycol, and pore control reaction catalyst are uniformly mixed with the polyether sulfone resin solution. This is cast on a film support, and the surface pore size is controlled by simultaneously evaporating the non-solvent in the coating solution and simultaneously solidifying by moisture exposure while injecting circulating air containing a proper temperature / humidity to contact the surface of the coating solution. . Of course, the air non-contact surface facing the support is relatively blocked from the circulation air contact to form a dense surface layer. This solidifies into an asymmetric polyether sulfone membrane.

Of course, to ensure that the evaporation of the non-solvent in the coating liquid does not occur rapidly, sufficient residence time and the injection speed of the air to be precisely controlled.

Then, the solvent, non-solvent, and other additive compounds remaining in the membrane are removed with an alcohol mixture or water, and micropores are formed therein to complete the porous polyether sulfone membrane shape. Through this proper drying process, we can reproducibly produce a membrane that can improve the efficiency, high flow rate, and useful life by asymmetrical cross-sectional structure and porosity that we want.

Thereafter, optionally, when hydrophilicity is further required as a method of post-treatment process according to the use of each industry, the hydrophilic function may be imparted to the membrane by a hydrophilic material crosslinking reaction such as UV treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, these Examples are only some examples of the present invention, and the scope of the present invention is not limited to these.

The polyether sulfone resin used in the following examples has a molecular weight of 100,000 to 300,000. Pellets or powdered polyether sulfones are dissolved in a solvent to form an opaque, highly viscous liquid. The solvents that can be used are N-methyl-2-pyrrolidone (NMP) and dimethylformamide (DMF). ), Dimethyl sulfoxide, dimethylacetamide (DMAc) or a mixture thereof.

In this experiment, NMP was used to dissolve and epoxy-based compounds were added as catalysts to control the pore formation rate during the coagulation reaction with acetate-based and alcohol-based organic compounds and circulating air. It was.

 EXAMPLE

 Example 1 (Air coagulation method; average pore 0.1 μm)

18 to 20% of polyether sulfone resin (E6020-P, manufactured by BASF), 30 to 40% of N-methyl-2-pyrrolidone (NMP), 15 to 20% of butyl acetate, 10 to 15 of polyether glycol 800 A composition solution of 1% to 5% of reaction catalyst is prepared. At this time the solution is maintained at 30 ℃. The solution is uniformly cast on the continuous film support and then coated to have a thickness of 100 to 120 µm. Process the coating solution coated with circulating air using the temperature range 20 ~ 65 ℃ and humidity range 30 ~ 80% gradient device to make the pore size of the surface layer, and the coagulation tank in which the composition ratio of IPA / water is kept constant Pass through to complete solidification. Thereafter, the membrane is peeled off from the film support, and the remaining solvent component contained in the microporous membrane in the washing tank is completely extracted, and the membrane is prepared by drying the air at 80 ° C. under the conditions shown in Table 1 below. Then, the physical properties of the membrane prepared through the hydrophilization treatment mentioned above were measured based on the following evaluation method. The results are summarized in Table 2.

 Examples 2 to 4 (Air coagulation method; average porosity 0.2 µm to 0.8 µm)

In the same manner as in Example 1, except that the circulating air contact amount and residence time of the polyether sulfone were changed under the conditions shown in Tables 1 and 2 below. The results measured according to the following evaluation methods are summarized in Table 2.

Property evaluation method

  (1) The flow rate measured the unit area and the flow rate per minute at a constant pressure (10 Psi) after mounting a disk with a diameter of 47 mm.

  (2) The bubble point was measured by moistening pure water with a WET solution using a PMI Co., Ltd. model.

  (3) The flow rate reduction rate is the moment when the membrane passes through the membrane at 47mm diameter flat membrane evaluator (manufactured by Saehan Co., Ltd.) at the time of passing 2L of dust standard solution through the membrane at the initial flow rate and constant pressure (0.9bar). The flow rate was measured and indicated as being reduced.

 [Comparative Examples 1-4] (Wet Coagulation Method; Average Pore 0.1 µm to 0.8 µm)

Membrane was prepared in the same manner as in Example 1 except that the circulating air coagulation method was not used using a temperature and humidity gradient equipment. The results measured according to the above evaluation method are summarized in Table 3.

Table 1

Pore size (㎛) Circulating air Retention time (minutes)   Injection speed (m / min)   Temperature range (℃)  Humidity Range (%)  Example 1  0.1  > 1  <3   20 to 65  30 to 80  Example 2  0.2  > 3  <6  Example 3  0.45  > 4    <10  Example 4  0.8  > 6   <15

Table 2

Pore size (㎛) Polymer concentration  Coagulation              Property evaluation PES (%) Melting temperature Speed (m / min) Coagulation bath (% IPA) Thickness (㎛) Flow rate (ml / min / cm 2) IPA (B.P; Psi) Flow rate reduction rate (%) Example 1 0.1 18-20 30  0.2 50 100-120  7-11  30 to 36  20-30 Example 2 0.2 14-16 30  0.2 50 100-120  16-25  20 to 26  20-30 Example 3 0.45 10 to 12 30  0.2 50 100-120  26-34  12-16  20-30 Example 4 0.8  8 to 10 30  0.2 50 100-120  45 to 60 6-9  30-40

Table 3

Pore size (㎛) Polymer concentration  Coagulation Property evaluation PES (%) Melting temperature  Speed (m / min) Coagulation bath (% IPA) Thickness (㎛) Flow rate (ml / min / cm 2)   IPA (B.P; Psi) Flow rate reduction rate (%) Comparative Example 1 0.1 18-20 30 0.2 50 100-120 3 to 5 28-31  45 to 60 Comparative Example 2 0.2 14-16 30 0.2 50 100-120 8 to 12 18-22  40-50 Comparative Example 3 0.45 10 to 12 30 0.2 50 100-120 16-22 10 to 12  35-50 Comparative Example 4 Not measurable  8 to 10 30 0.2 50 100-120 20 to 26 12-15  70-80

As described above, the production method according to the present invention more stably establishes the asymmetric cross-sectional structure and reproducibility of the physical properties of the polyether sulfone membrane, and the prepared polyether sulfone membrane exhibits optimum filtration efficiency, high flow rate and use. The cycle exhibits improved characteristics.

Claims (7)

Providing a solution of polyethersulfone dissolved in a solvent; Uniformly mixing a non-solvent, a hydrophilic material, and a pore control reaction catalyst with the polymer solution; Casting the homogeneous solution onto a continuous phase support and solidifying by exposure to circulating air having a suitable temperature and humidity; A method of making an asymmetric polyether sulfone membrane, comprising extracting an uncoagulated compound from a polyethersulfone coagulant. The method of claim 1, wherein the membrane has an average pore size in the range of 0.01-2.0 μm on average. The method of claim 1, wherein the circulating air has a temperature in the range of 20-65 ° C. 3. The method of claim 1, wherein the circulating air has a humidity in the range of 30-80%. The method of claim 1, wherein the air is injected at a speed in the range of 1-20 m / min, depending on the pore size. The method of claim 1, wherein the membrane has a porosity of at least 70%. The method of claim 1, wherein the reaction catalyst comprises an epoxy-based compound.