KR20100079632A - Manufacturing method for high flow micro-porous membrane using sonication and micro-porous membrane thereby - Google Patents

Abstract

PURPOSE: A manufacturing method of a high flow minute microporous membrane and a minute porous membrane manufactured thereby are provided to improve productivity through reduction of solidification time and to manufacture an asymmetric minute porous membrane. CONSTITUTION: A manufacturing method of a high flow minute microporous membrane includes the following steps: casting a polymer solution including a polymer, a solvent, and an additive on a metal plate support; exposing the polymer solution to the air; and forming minute pores by dipping the polymer solution in an ultrasonic solidification bath. The method further includes a step for precipitating the exposed polymer solution in a pre-process solidification bath. The relative humidity of the air is 35% ~ 95%. The temperature of the air is 22 ~ 35°C. The retention time of the ultrasonic solidification bath is 1 ~ 60 seconds.

Description

Manufacturing method of high flow rate microporous membrane using ultrasonic wave and microporous membrane manufactured therefrom {MANUFACTURING METHOD FOR HIGH FLOW MICRO-POROUS MEMBRANE USING SONICATION AND MICRO-POROUS MEMBRANE THEREBY}

The present invention relates to a method for manufacturing a microporous membrane applicable to semiconductor, pharmaceutical, and power generation wastewater treatment. More specifically, the microporous membrane has a high flow rate and a high porosity with improved productivity, cost reduction, and increased porosity. A method of making a membrane and a microporous membrane made therefrom.

Micro-porous membranes are economically and technically very important in the material separation process, and are applied in various fields including medicine, food, semiconductor, and water treatment. For example, since resins such as polyvinylidene fluoride and polyether sulfone have high thermal stability, oxidative stability, and temperature stability, they are widely used because they are suitable for various wastewater, purified water, and drinking water treatment processes.

Currently used microporous membranes have various structures and functions and are manufactured by various manufacturing methods.

Typically, the polymer membrane is prepared by selecting a suitable polymer solvent to make a polymer solution, casting it to form a thin sheet, and depositing it in a solid phase. The deposited polymer membrane is generally formed in short contact with air and in contact with the nonsolvent liquid in the settling bath. Membranes prepared in this way have been used in a wide range of membrane preparation methods, from microfiltration to gas permeation.

Looking at the manufacturing example of such a microporous membrane, US Patent No. 4,840,733 casts a polysulfone-based polymer, and presents the manufacturing conditions such as temperature, humidity, wind speed, in particular, the air exposure time is within 2 seconds, 30 seconds long A method of preparing a single layer polymer membrane without air support by air treatment for a relatively short time is disclosed.

In addition, U. S. Patent No. 4,933, 081 discloses a method of making a membrane based on dry-wet coagulation. More specifically, the patent is a polyvinylpyrrolidone and a non-solvent, and then uniformly mixed with water after mixing the polymer and the solvent, and then cast the cast film step by step under a condition of 40 ℃, 60% relative humidity. It is disclosed that after exposure to air for 30 seconds, coagulation and drying at a temperature of 20 ° C. produces a microporous membrane of asymmetric structure.

U. S. Patent No. 5,886, 059 also discloses a method of making a membrane based on wet coagulation. More specifically, in the patent, the non-solvent is uniformly added after mixing the polyether sulfone and the solvent, and the obtained solution is cast on a support, exposed to air for 2 seconds, and solidified in a coagulation bath to form a microporous of asymmetric structure. The manufacture of membranes is disclosed.

In addition, US Pat. No. 6,939,468 discloses a method for preparing a membrane based on dry coagulation. More specifically, in the patent, an asymmetric microporous membrane is prepared by appropriately mixing a polymer, a solvent, and a non-solvent, casting the obtained solution, controlling humidity and exposure time of a humidified air, and controlling a coagulation bath temperature. It is disclosed.

In addition, Korean Patent Publication Nos. 2003-86741 and 2003-43283 disclose a composition for preparing a polyether sulfone membrane and a method for preparing a microfiltration membrane using the same. The content of polyethylene glycol as a pore control agent through the preparation method is known. It is described that it is possible to freely control the microporosity and pore size by only a short time exposure under constant humidity during casting.

As described above, the microporous membrane in the prior art is largely manufactured by three methods, namely, dry coagulation, wet coagulation, and dry wet coagulation. However, when the microporous membrane is manufactured by the conventional technique, the solidification time is increased during solidification, and thus the manufacturing time of the microporous membrane is lengthened, resulting in a sufficiently low productivity and an increase in related costs. Due to the manufacture of the membrane through the membrane there are many constraints to efficiently produce high flow characteristics.

Accordingly, the present inventors have tried to solve the conventional problems, shorten the solidification time to improve productivity, and to obtain a high flow rate asymmetric microporous membrane with increased porosity, so that the ultrasonic treatment in the solidification step of the polymer solution By carrying out, the present invention was completed by preparing a microporous membrane and confirming high flow characteristics due to the high porosity of the microporous membrane.

It is an object of the present invention to shorten the solidification time and to provide a method for producing a microporous membrane of high porosity and high flow rate.

Another object of the present invention is to provide a microporous membrane prepared by the above production method and having an average diameter of 0.1 to 1.0 μm, and having a porosity of 70 to 80%.

In order to achieve the above object, the present invention provides a method for producing a microporous membrane which casts a uniform polymer solution including a polymer, a solvent, and an additive to a metal plate support, is exposed to air, and then immersed in an ultrasonic coagulation bath to form micropores. to provide.

In addition, the manufacturing method may further include the step of precipitating the exposed polymer solution in an ultrasonic untreated coagulation bath after exposure to air.

At this time, the relative humidity of the air is 35% to 95%, the temperature of the air is preferably 22 to 35 ℃.

The residence time of the ultrasonic coagulation bath is preferably 1 to 60 seconds, and the residence time of the ultrasonic untreated coagulation bath is preferably 1 second to 30 seconds.

At this time, the frequency of the ultrasonic wave is preferably 15 to 85 KHz.

The polymer solution applied to the present invention may be composed of 5 to 40% by weight of the polymer and additive mixture and 60 to 95% by weight of the solvent, and the mixture may be mixed at a ratio of 0.5 to 3 polymers to 7 to 9.5 of the additive.

At this time, the polymer may be any one selected from the group consisting of polyether sulfone, polysulfone, polyvinylidene fluoride and polyacrylonitrile having a weight average molecular weight of 500,000 to 700,000, the solvent is N- One or more selected from the group consisting of methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and dimethylacetamide (DMAc) may be used, and the additive may be ethylene glycol, Glycerol; Methanol, ethanol; Acetone; One or more selected from the group consisting of polyvinylpyrrolidone, polyethylene glycol can be used.

Furthermore, the present invention provides a microporous membrane prepared by the above method of casting a uniform polymer solution including a polymer, a solvent and an additive to a metal plate support, exposing to air, and then immersing in an ultrasonic coagulation bath to form micropores. do.

At this time, the average diameter of the micropores is 0.1 to 1.0 ㎛ and porosity is 70 to 80%.

The present invention has an asymmetric cross-section due to the improvement of productivity through the reduction of the solidification time and the high porosity and pore formation due to the vibration by applying the ultrasonic wave that gives a strong vibration to the solidification step, thereby producing a high asymmetric microporous membrane. It is applicable to semiconductor, pharmaceutical, power generation wastewater treatment with better physical properties.

Hereinafter, the present invention will be described in more detail.

One aspect of the present invention comprises the steps of preparing a uniform polymer solution containing a polymer, a solvent and an additive; Casting the uniform polymer solution on a metal plate support; Exposing the cast solution to air at an appropriate temperature and humidity; And dipping the exposed polymer solution in an ultrasonic coagulation bath to form a microporous membrane.

First, the present invention provides a polymer solution including a polymer, a solution, and an additive.

Polymers usable in the present invention are selected from polyethersulfone, polysulfone, polyvinylidene fluoride, polyacrylonitrile and the like, and the weight average molecular weight thereof is in the range of 500,000 to 700,000 in consideration of the mechanical strength of the microporous membrane prepared. Is preferably.

In addition, the solvent in the present invention can be applied to any solvent that can dissolve the polymer and additives at the same time, but preferably N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide ( One solvent selected from the group consisting of DMSO) and dimethylacetamide (DMAc), or mixtures of two or more such solvents.

The additive in the present invention may use all additives that can be appropriately adjusted or modified for the desired properties of the microporous membrane to be produced, for example additives for controlling the pores formed in the microporous membrane, ie pore control agent Can be used. The pore control agent usable in the present invention may be a hydrophilic material having affinity for water in humidified air, and more preferably glycols such as ethylene glycol and glycerol; Alcohols such as methanol and ethanol; Ketones such as acetone; Preference is given to one pore control agent or a mixture of two or more such pore control agents selected from the group consisting of polymers such as polyvinylpyrrolidone, polyethylene glycol and the like.

The present invention can adjust the pore size of the surface according to the control of the composition ratio of the polymer solution, the composition ratio of each component in the polymer solution is 5 to 40% by weight of the polymer and additive mixture and 60 to 95% by weight solvent It is preferred to have a composition ratio of 8 to 25% by weight of the polymer and additive mixture and 75 to 92% by weight of the solvent.

At this time, the mixture is preferably mixed at a ratio of 0.5 to 3 polymers to 7 to 9.5 of the additives, and if the polymer ratio is less than 0.5, a symmetrical structure is formed, which does not correspond to the preparation of an asymmetric membrane for the purpose of the present invention, and more than 3 In case of coagulation, an asymmetric structure including macropores is formed during solidification, which shows disadvantageous disadvantages in mechanical performance of the membrane.

In addition, the temperature of the polymer solution is preferably maintained higher than the temperature of the metal plate support to be cast, more preferably from room temperature to 70 ℃. If the temperature of the polymer solution is lower than room temperature, the problem may occur that the permeation flow rate decreases due to the increase of the viscosity of the polymer solution, and when the temperature exceeds 70 ° C, the casting viscosity is disadvantageous due to the low viscosity.

The present invention then casts a homogeneous polymer solution onto the metal plate support and exposes the cast solution to air at an appropriate temperature and humidity.

The metal plate support may be a metal material, preferably stainless steel, aluminum, or a copper alloy.

On the other hand, the appropriate temperature of the air is room temperature, that is, 25 ℃ to 35 ℃, wherein the relative humidity of the air is preferably maintained in the range of 35% to 95%.

In addition, the exposure time of the polymer solution in the air is preferably 2 seconds to 60 seconds depending on the temperature and relative humidity of the air. If the exposure time is less than 2 seconds, it is difficult to express an asymmetric structure due to the weak diffusion of the solvent in the air, and if it exceeds 60 seconds, it is difficult to control the size and asymmetric structure of the pores and the productivity is lowered.

The present invention then precipitates the exposed polymer solution in an ultrasonic coagulation bath to coagulate it.

The ultrasonic coagulation bath is a coagulation bath including an ultrasonic wave generation device, a frequency control device, a time control device, and the like, which are capable of ultrasonic treatment, and the kind thereof is well known to those skilled in the art, and the present invention is not limited thereto.

At this time, the frequency of the ultrasonic wave is preferably 15 to 85 KHz. If the frequency is less than 15 KHz, the porosity increase due to the vibration of the ultrasonic wave is not sufficient, and if the frequency exceeds 85 KHz, the microporous membrane is formed due to the strong vibration. Pore of is broken and is undesirable.

Meanwhile, the ultrasonic coagulation bath residence time of the exposed polymer solution is 1 to 60 seconds, more preferably 5 to 60 seconds. If the ultrasonic coagulation bath residence time is less than 1 second, the porosity due to the vibration of the ultrasonic wave is not sufficient. If it exceeds 60 seconds, the pores are partially broken due to the ultrasonic waves, and it is difficult to form a uniform membrane.

By appropriately adjusting the residence time and frequency of the ultrasonic coagulation bath, porosity and porosity through ultrasonic vibration can be optimally adjusted according to the present invention. In addition, as the coagulating solution of the present invention, various solvents including water may be used, and preferably water is used.

The present invention can shorten the solidification time by performing such an ultrasonic treatment step, thereby improving the productivity, and also has an asymmetric cross section due to the high porosity and pore formation by ultrasonic vibration, thereby producing a fine It can be represented by the high flow characteristics of the porous membrane.

In addition, the production method of the present invention may further comprise the step of precipitating the exposed polymer solution in an ultrasonic untreated coagulation bath.

Accordingly, another aspect of the present invention is to prepare a uniform polymer solution containing a polymer, a solvent and an additive; Casting the uniform polymer solution on a metal plate support; Exposing the cast solution to air at an appropriate temperature and humidity; Precipitating the exposed polymer solution in an ultrasonic untreated coagulation bath; And immersing the exposed polymer solution in an ultrasonic coagulation bath to form a microporous membrane.

In this case, the ultrasonic untreated coagulation bath may be used after the same device as the ultrasonic coagulation tank, or may be used as another device. When the ultrasonic untreated coagulation bath is used in the same apparatus as the ultrasonic coagulation bath, the coagulation bath may be equipped with a switch or an equivalent control device for starting and stopping the ultrasonic treatment. The residence time of the ultrasonic untreated coagulation bath is 1 to 30 seconds, more preferably 1 to 5 seconds.

 In addition, the coagulation liquid of the present invention is preferably water.

The membrane subjected to the solidification step of the present invention further includes a washing process to remove the remaining solvent in and out of the surface. The use of water as the washing liquid is preferred, and the washing time is not particularly limited, but at least 12 hours or more, preferably 1 day or less. The present invention may further include a step of drying in the air after immersion in ethanol or methanol, the immersion and drying period is not particularly limited, but 4 hours or less is preferred.

In addition, the present invention is a fine polymer produced by the above method, characterized in that to cast a uniform polymer solution containing a polymer, a solvent and an additive to a metal plate support, exposed to air, and then immersed in an ultrasonic coagulation bath to form fine pores Provide a porous membrane.

In this case, the microporous membrane has a final thickness of 100 to 120 ㎛, comprises a porous having an average diameter of 0.1 to 1.0 ㎛, and has a porosity of 70 to 80%.

In addition, the detailed description of the polymer, the solvent and the additive is the same as described above.

The microporous membrane prepared by the embodiments of the present invention is a high flow porous membrane having a porosity increased by vibration in accordance with ultrasonic treatment, and can be used for semiconductor, pharmaceutical, power generation wastewater treatment, and the like. That is, it can be used for battery separator, various filters, waterproof clothing, gas permeable membrane, reverse osmosis membrane, ultrafiltration membrane, microfiltration membrane and the like.

Hereinafter, the present invention will be described in detail with reference to examples.

The following examples are merely illustrative of the present invention, but the scope of the present invention is not limited to the following examples.

≪ Example 1 >

15% by weight of polyethersulfone resin (H2000, manufactured by Solvay co.), 60% by weight of dimethylformamide (DMF), and 25% by weight of polyetherglycol (800), which is a pore regulator, were stirred at 30 ° C. to obtain a completely uniform polymer. The solution was prepared and bubbles were removed from the solution while keeping it at 30 ° C. This polymer solution was uniformly cast on the stainless steel support to a thickness of 120 μm at a rate of 2 m per minute. Immediately after casting it was exposed to air at 25 ° C. and 50% relative humidity for 10 seconds. The polymer solution exposed to air was coagulated by passing it through an ultrasonic coagulation tank having a frequency of 45 KHz for 5 seconds. Thereafter, the remaining solvent component contained in the membrane was completely extracted in a washing tank and dried with air at 80 ° C. to prepare a microporous membrane.

<Example 2>

A microporous membrane was prepared in the same manner as in Example 1 except that the residence time of the ultrasonic coagulation bath was performed for 10 seconds.

<Example 3>

The same method as in Example 1 was used to cast on a stainless steel support and exposed to air. Thereafter, the polymer solution exposed to air was passed through the ultrasonic untreated coagulation bath for 5 seconds, and then coagulated by passing it through the ultrasonic coagulation bath for 5 seconds. Thereafter, the same procedure as in Example 1 was performed to prepare a microporous membrane.

<Example 4>

A microporous membrane was prepared in the same manner as in Example 3 except that the residence time of the ultrasonic coagulation bath was performed for 10 seconds.

Comparative Example 1

A microporous membrane was prepared in the same manner as in Example 1 using an ultrasonic untreated coagulation bath.

Experimental Example

After mounting the prepared microporous membrane 47 mm diameter disk, the pressure of 10 psi was kept constant to measure the unit area and the flow rate per minute. The physical properties of the measured membranes are shown in Table 1 below.

Polymer concentration (%) Casting speed (m / min) Solidification tank residence time (sec.) Flow rate evaluation
(ml / min * cm ² * bar) Ultrasonic untreated ultrasonic wave
process Example 1 15 2 0 5 32-36 Example 2 15 2 0 10 40-44 Example 3 15 2 5 5 36-40 Example 4 15 2 5 10 42-46 Comparative Example 1 15 2 60 0 28-32

From the above results, the microporous membrane prepared by the ultrasonic treatment in Examples 1 to 4 compared with the microporous membrane of Comparative Example 1 which was not ultrasonically treated, observed an increase in permeate flow rate, and also according to the increase of the ultrasonic treatment time. , Increase in permeation flow rate was observed. It can be seen from this feature that the porosity of the microporous membrane is increased by the ultrasonic vibration according to the present invention, thereby increasing the permeate flow rate of the microporous membrane.

As described above, the present invention has an asymmetric cross-section due to high productivity and reduction of the solidification time by applying ultrasonic waves giving a strong vibration to the solidification step and having an asymmetric cross section due to high porosity and pore formation due to vibration. It was possible to produce a microporous membrane, which can be applied to semiconductor, pharmaceutical, power generation wastewater treatment with better physical properties.

Although the present invention has been described in detail only with respect to the embodiments described, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and such modifications and modifications belong to the appended claims.

Claims (13)

A method for producing a microporous membrane, comprising casting a polymer solution including a polymer, a solvent, and an additive to a metal plate support, exposing it to air, and then immersing it in an ultrasonic coagulation bath to form micropores. The method of claim 1, further comprising the step of precipitating the exposed polymer solution in an ultrasonic untreated coagulation bath after exposure to air. The method of claim 1, wherein the relative humidity of the air is 35% to 95%. The method of claim 1, wherein the temperature of the air is 22 to 35 ℃. The method of claim 1, wherein the residence time of the ultrasonic coagulation bath is 1 to 60 seconds. The method of manufacturing the microporous membrane according to claim 2, wherein the residence time of the ultrasonic untreated coagulation bath is 1 to 30 seconds. The method of claim 1, wherein the frequency of the ultrasonic waves is 15 to 85KHz. According to claim 1, wherein the polymer is any one selected from the group consisting of polyethersulfone, polysulfone, polyvinylidene fluoride and polyacrylonitrile having a weight average molecular weight of 500,000 to 700,000 Method for producing a porous membrane. The method of claim 1, wherein the solvent is at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and dimethylacetamide (DMAc). Method for producing the microporous membrane, characterized in that. The method of claim 1, wherein the additive is at least one selected from the group consisting of ethylene glycol, glycerol, methanol, ethanol, acetone, polyvinylpyrrolidone, and polyethylene glycol. The method of claim 1, wherein the polymer solution comprises 5 to 40 wt% of a polymer and additive mixture and 60 to 95 wt% of a solvent. 12. The method of claim 11, wherein the mixture is mixed at a ratio of 0.5 to 3 polymers to 7 to 9.5 of additives. A microporous membrane prepared by the method of claim 1, wherein the average pore size of the micropores is 0.1 to 1.0 µm and the porosity is 70 to 80%.