KR100855663B1 - Surface modification method of pvdf membrane with high flux properties - Google Patents

Abstract

The present invention relates to a method for surface modification of polyvinylidene fluoride membranes having high flow rate characteristics.

In the present invention, the surface modification method of the polyvinylidene fluoride membrane consists of not only the surface of the polyvinylidene fluoride membrane but also an alcohol solution containing an acrylic monomer and a photoinitiator to the inside of the pores, followed by UV light irradiation. Hydrophilic acrylic derivative is bonded to the main chain of the linear polymer of the hydrophobic polyvinylidene fluoride membrane in the form of a side chain, and a hydroxyl group (-OH) is formed on the surface of the polyvinylidene fluoride membrane. Polyvinylidene fluoride membranes surface-modified to have Furthermore, the polyvinylidene fluoride membrane of the present invention can improve surface hydrophilicity, shorten moisture absorption time, and can provide high flow rate characteristics.

Polyvinylidene Fluolide, Membrane, Hydrophilicity, Hydrophilic, UV, Light Irradiation

Description

SURFACE MODIFICATION METHOD OF PVDF MEMBRANE WITH HIGH FLUX PROPERTIES

1 is a side view of the air hydraulic device of the present invention,

2 is a front view of the air hydraulic apparatus of the present invention.

<Short description of drawing symbols>

1: air inlet 2: air outlet

3: General suction line 4: Porous type suction line

The present invention relates to a surface modification method of a polyvinylidene fluoride membrane (hereinafter referred to as "PVDF") having high flow rate characteristics, and more particularly, not only to the surface of the PVDF membrane but also to the inside of the pores for improving the flow rate. The present invention relates to a surface modification method of a PVDF membrane in which a PVDF membrane and an acrylic derivative are surface-modified hydrophilically by graft polymerization by filling an alcohol solution containing an acrylic monomer and a photoinitiator and then irradiating with UV light.

Conventionally, various graft polymerization methods which depend on the degree of hydrophilization are representative of the method of hydrophilizing a hydrophobic polymer surface. Specifically, ozone [ Journal of Applied Polymer Science , 1999 , 72 , 611], radiation [ Journal of Polymer Science , 1994 , 51 , 1269, Radiation Physics and Chemistry , 1999 , 54 , 637], and radicals are formed using plasma and ultraviolet light, and then hydrophilic monomers are introduced and grafted thereto.

However, the method mainly low geurapeuteuyul since modified in the form of a coating only to the polymer surface layers, because the use of expensive equipment, there is limited application of such small-sized special film and membrane there is a limit to the application [Journal of Applied Polymer Science , 1998 , 69 , 143].

In addition, in order to apply a compatibilizer and a dye for the branding between the hydrophilic polymer and the hydrophobic polymer to the polymer, a high graft ratio is required for the polymer of the main chain, which is a method for obtaining a polymer having such a high graft ratio. US Pat. No. 5,663,237 discloses a method of grafting under supercritical water of carbon dioxide, a method of grafting in a molten state of a polymer [ Journal of Applied Polymer Science , 1994, 53, 239]. In addition, US Pat. No. 5,079,032 discloses a solid phase polymerization method in which a small amount of solvent is added to a surface to have flexibility and wettability, thereby maintaining the solid state during the reaction of the polymer.

However, the solid phase polymerization method is very limited because it attempts to introduce a hydrophilic hydrocarbon monomer into a hydrophobic polymer consisting mainly of hydrocarbons, and the reactor used is a Brabender type which is a mixer used commercially for solid-solid mixing. Since it is used as it is, there is a limit to the application.

Therefore, the conventional technology is limited to the surface of the film type having no porosity, and thus, exhibits significantly lower characteristics than other materials in terms of water permeability (flow rate). Particularly, in the case of hydrophilization using plasma, hydrophilization treatment into internal pores is quite difficult and practical commercialization is difficult due to high cost. In addition, the surface treatment method by UV light irradiation is now widely commercialized, but pretreatment mainly through the spray method and dipping method, which is a conventional pretreatment method, hydrophilization treatment for membranes for the purpose of high flow rate through improving water permeability As it is inefficient in method, it is not effective.

As yet, conventional hydrophilization methods do not adequately wet the membrane surfaces with low surface tension, but rather hydrophilicity causes low fluid permeability or pressure drop across the membrane. Due to this phenomenon, various methods have recently been attempted to improve hydrophilic coatings. However, the permeability of the membrane coated with the above proposed method shows a slight improvement or still low results, which are not satisfactory.

Therefore, the present inventors have tried to solve the problems of the prior art, as a result of the pre-treatment process before the light irradiation in the conventional hydrophilic process by the light irradiation method, the alcohol solution containing acrylic monomers and photoinitiator pores as well as the surface of the PVDF membrane After filling to the inside, UV light irradiation was carried out to graft polymerization, surface hydrophilicity was improved, moisture absorption time was shortened, and the present invention was completed by confirming PVDF membrane physical properties to which high flow rate characteristics were imparted.

It is an object of the present invention to provide a method for surface modification of PVDF membranes having high flow rate characteristics.

Another object of the present invention is to provide a surface modification method of a PVDF membrane having a high flow rate characteristic of performing a pretreatment method for hydrophilization treatment before UV irradiation of the PVDF membrane.

It is still another object of the present invention to provide a high flow rate PVDF membrane prepared from the surface modification method of the PVDF membrane.

In order to achieve the above object, the present invention provides a method for producing a hydrophilic surface-modified PVDF membrane. More specifically

1) A PVDF membrane having a pore size of 0.1 to 10 μm is first impregnated into an alcohol solution containing an acrylic monomer and a photoinitiator,

2) suctioning the solution present on the impregnated PVDF membrane surface into the PVDF membrane pores via an air inlet,

3) secondly impregnated the PVDF membrane in the alcohol solution containing the acrylic monomer and photoinitiator,

4) After removing the solvent at a temperature of 40 ~ 80 ℃ the PVDF membrane, UV light irradiation to graft polymerization reaction of the PVDF membrane and the acrylic derivative surface modification to hydrophilic.

The PVDF membrane of step 1) is supplied at a process speed of 0.5 ~ 5 m / min.

The solution in step 1) or step 3) is prepared by containing 10-50 g of acrylic monomer and 0.1-1.0 g of photoinitiator in 1 L of alcohol solvent, and the acrylic monomer is a group consisting of acrylic acid, methacrylic acid and glycidyl methacrylate. Is any one selected from, and the photoinitiator is 2,2-dimethoxy-2-phenylacetophenone.

In the manufacturing method of the present invention, step 2) is characterized in that the solution is sucked into the PVDF membrane pores due to the difference between the air pressure inside the apparatus and the air pressure outside the apparatus while the primary impregnated PVDF membrane passes through the air inlet apparatus. do. The air inlet device consists of a tubular roll having a porous suction tube 4 formed on a general suction tube 3 between the air inlet 1 and the air outlet 2.

In the production method of the present invention, the UV light irradiation in step 4) is irradiated for 1 second to 10 minutes.

The present invention provides a PVDF membrane, which is prepared from the above method, and prepared by graft polymerization of a PVDF membrane and an acrylic derivative. The PVDF membrane has a surface tension of 50 to 64 dyne / cm, a contact angle of 55 ° to 67 °, and a moisture absorption time of 1.0 to 1.5 s / μl.

In addition, the PVDF membrane of the present invention is characterized by maintaining a tensile strength of 95% to 100% with respect to the porous PVDF membrane not UV treated.

Hereinafter, the present invention will be described in detail.

The present invention provides a method for surface modification of a PVDF membrane surface-modified to have a hydroxyl group (-OH) on the surface of the PVDF membrane by preparing a graft polymer of a PVDF membrane and an acrylic derivative by UV light irradiation.

More specifically, a graft polymer obtained by combining a hydrophilic acrylic derivative in the form of a side chain with a hydrophobic PVDF (CF ₂ -CF ₂ ) _n membrane in the bond line of the polymer is connected to the main chain of the polymer. The present invention provides a pretreatment method for more effective hydrophilization treatment of PVDF membranes before UV light irradiation.

Thus, the method of manufacturing the PVDF membrane of the present invention

1) A PVDF membrane having a pore size of 0.1 to 10 μm is first impregnated into an alcohol solution containing an acrylic monomer and a photoinitiator,

2) suctioning the solution present on the impregnated PVDF membrane surface into the PVDF membrane pores via an air inlet,

3) secondly impregnated the PVDF membrane in the alcohol solution containing the acrylic monomer and photoinitiator,

4) After removing the solvent at a temperature of 40 ~ 80 ℃ the PVDF membrane, UV light irradiation to graft polymerization reaction of the PVDF membrane and the acrylic derivative surface modification to hydrophilic.

The PVDF membrane of step 1) is supplied at a process speed of 0.5 to 5 m / min. Depending on the process speed, when UV light irradiation, the reaction time is different. At this time, if the process speed is less than 0.5 m / min, UV irradiation time is long, the chemical bond is decomposed by the excessive light source is inadequate, and if it exceeds 5 m / min, UV irradiation time required for the reaction is short, the graft rate is low It is not desirable because

The solution in step 1) or step 3) is to introduce an acrylic derivative into the PVDF membrane, and is prepared by containing 10-50 g of acrylic monomer and 0.1-1.0 g of photoinitiator in 1 L of an alcohol solvent.

The acrylic monomer is any one selected from the group consisting of acrylic acid, methacrylic acid and glycidyl methacrylate, the preferred content is to use 10 to 50 g / L per 1 L of solvent, if less than 10 g / L, If the required amount of monomer is small, the graft rate is low, resulting in poor water permeability. If it exceeds 50 g / L, the polymerization rate is higher than the polymerization with the membrane due to the presence of excess monomer, and thus the graft rate between the membrane surface and the monomer is low. Not.

Preferred photoinitiators used in the present invention are 2,2-dimethoxy-2-phenylacetophenone, and it is preferable to use 0.1-1.0 g per 1 L of solvent.

At this time, if the photoinitiator is less than 0.1 g / L, the graft ratio between the monomer and the membrane is advantageous, and if it exceeds 1.0 g / L, the amount of photoinitiator required for the reaction is reduced due to the radical reaction of the photoinitiator itself is not preferable.

The solvent used in the present invention is not particularly limited as long as it is a solvent which can be evaporated at 40 to 80 ° C, and may be used. More preferably, an alcohol solvent is used, and as an example thereof, any one selected from the group consisting of methyl alcohol, ethyl alcohol, propyl alcohol and isopropyl alcohol is used.

In the method of the present invention, step 2) impregnates the PVDF membrane in the alcohol solution containing the acrylic monomer and the photoinitiator in step 1), so that the solution existing on the surface of the PVDF membrane is passed through the air injector through the PVDF membrane pores. It is a process to inhale inside.

Although the acrylic monomer used in the present invention is in a liquid state at room temperature, it is difficult to evenly disperse evenly to the inside of the membrane pores with respect to the hydrophobic PVDF membrane surface, but the alcohol containing the acrylic monomer and the photoinitiator by the air inhalation method of step 2). By evenly dispersing the solution into the inner pores, as well as the membrane surface, it is possible to achieve high graft rates that cannot be reached by simply performing a conventional impregnation process.

1 and 2 are side and front views of the air inlet device of the present invention, when passing through the air inlet port 1 through the air outlet port 2, the fine pores on the general suction tube (3) with large pores in the middle portion It consists of a tubular roll formed with a porous suction tube 4 of a ball.

At this time, the PVDF membrane impregnated in step 1) passes through the upper portion of the porous suction pipe 4 of the air inlet device, and the solvent existing on the surface before and after the PVDF membrane is introduced into the inside due to the difference in the air pressure inside the device and the air pressure outside the device. It is.

That is, the air inflow method is an application of Bernoulli's theorem, and is a penetration method using the principle that the pressure is lowered on the surface where the speed of the fluid is increased, and the flow of the fluid flows from a high place to a low place. Therefore, since the inside of the tubular of the air inlet device of the present invention is low in pressure and the top of the tubular maintains atmospheric pressure in the atmospheric state, fluid existing outside the membrane is introduced into the inside.

In the method of the present invention, step 3) is the acrylic monomer and photoinitiator on both surfaces of the PVDF membrane by secondary impregnation of the PVDF membrane in which the alcohol solution containing the acrylic monomer and the photoinitiator is sucked up to the inside of the PVDF membrane in step 2). The alcohol solution containing is dispersed to induce the graft polymerization reaction.

In the method of the present invention, before the UV light irradiation in step 4), a process of removing the solvent leaving only the acrylic monomer and photoinitiator necessary for the graft polymerization reaction by light irradiation is performed.

As for the removal means of the said solvent, it is more preferable to use the infrared heater of 30-80 degreeC.

Then, using a UV lamp of a high energy density of 100 mW / cm or more, the graft polymerization reaction by UV irradiation for 1 second to 10 minutes.

At this time, 2,2-dimethoxy-2-2-phenylacetophenone which is a photoinitiator used in the present invention is decomposed into radicals at 90 to 120 ° C., and has a half-life of about 1 to 20 minutes, depending on the polymerization reaction time. The graft ratio can be adjusted appropriately.

Accordingly, the preferred polymerization time of the present invention is preferably 1 second to 10 minutes. If the polymerization time is less than 1 minute, it is difficult to obtain a polymer having an appropriate graft ratio. The performance is lowered, so that the self polymerization of the monomer proceeds more easily than the graft polymerization, which also lowers the graft rate.

The irradiation source of light irradiation used in the graft polymerization in the present invention may provide a continuous spectrum of wavelengths, a series of peaks or a single emission line. Preferred light irradiation source may be any one method selected from the group consisting of vacuum UV irradiation, high power UV irradiation, Broadband UV irradiation and Black body UV irradiation.

UV light irradiation source is preferably radiation having a broadband. For example, the broadband may include a wavelength distribution in the UV band of the wavelength range of 100nm to 400nm, for example, the band of 150nm to 350nm.

On the other hand, the radiation source may include a narrower band of radiation, for example, wavelength distribution within 100 to 200nm, 200 to 280nm, 280 to 315nm and 315 to 400nm, UV light source is not limited to this, and more It can be divided into various irradiation wavelength ranges.

The intensity or power density of the pulsed light source is about 100 to 1000 mW / cm at a treatment time of 1 second to 300 seconds, preferably 1 second to 120 seconds, more preferably 1 second to 60 seconds. Such a light source can deliver irradiation pulses in a short burst, and a pulse source can have sufficient energy and can deliver high density irradiation. Most preferably, the source is a source capable of pulsed broadband and blackbody irradiation as described in US Pat. No. 5,789,755.

The present invention provides a fluoride membrane that can be implemented from the surface modification method of the PVDF membrane.

The surface tension of the PVDF membrane is 50-64 dyne / cm, the contact angle is 55 ° -67 °, the surface hydrophilicity is improved, the moisture absorption time is 1.0-1.5 s / μl, the moisture absorption time is shortened, and eventually high flow rate Characteristics can be achieved.

Furthermore, the PVDF membrane of the present invention is characterized by maintaining a tensile strength of 95% to 100% with respect to the porous PVDF membrane not UV treated.

Accordingly, while maintaining the properties of the PVDF membrane, the PVDF membrane and the acrylic derivative are graft-polymerized to surface-modify hydrophilicly, thereby obtaining a high-volume PVDF membrane.

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

This embodiment is specifically described based on the most preferred embodiment of the present invention, the scope of the present invention is not limited to these examples.

<Example 1>

A PVDF membrane having a surface tension of 25 dyne / cm was impregnated in an ethanol solution containing 50 g of an acrylic acid monomer and 1 g of a photoinitiator 2,2-dimethoxy-2-2-phenylacetophenone, and then using a solvent suction device. The solution containing the monomer and the photoinitiator was sucked into the pores inside the PVDF membrane and filled. After the suction step, the PVDF membrane was re-impregnated with an ethanol solution containing 50 g of acrylic acid monomer and 1 g of photoinitiator 2,2-dimethoxy-2-2-phenylacetophenone. Subsequently, the solvent present on the surface and internal pores of the PVDF membrane was evaporated at 70 ° C., and then exposed to UV light for 10 seconds to obtain a surface treated PVDF membrane. At this time, the PVDF membrane was bound in the form of an acrylic derivative branch (Side Chain) by UV light irradiation, its surface tension was 51.5 dyne / cm, and the physical properties before and after the surface treatment is described in Table 1 and Table 2 below. It was.

Comparative Example 1

Impregnating a PVDF membrane having a surface tension of 25 dyne / cm into an ethanol solution containing 50 g of an acrylic acid monomer and 1 g of a photoinitiator 2,2-dimethoxy-2-2-phenylacetophenone, and inhaling the solution; and Except not performing the re-impregnation process of the impregnation solution, it was carried out in the same manner as in Example 1 to obtain a surface-treated membrane, wherein the surface tension of the surface-treated PVDF membrane was 42.5dyne / cm .

Comparative Example 2

The PVDF membrane was impregnated with an ethanol solution containing 50 g of acrylic acid monomer and 1 g of photoinitiator 2,2-dimethoxy-2-2-phenylacetophenone, and then exposed without evaporation of the solvent without passing through the solvent suction device. Was carried out in the same manner as in Example 1 to surface-treat the PVDF membrane. In this case, the surface tension of the surface-treated PVDF membrane was 33.5 dyne / cm.

<Example 2>

The PVDF membrane was surface treated in the same manner as in Example 1 except that the exposure time of UV light after evaporation of the solvent was changed as follows.

Experimental Example 1

For the surface treated PVDF membrane in the above embodiment, it was carried out by the following method to measure the degree of surface hydrophilization.

1) Surface tension measurement

When the contact angle was obtained from the correlation between the contact angle with water and the surface tension, the surface tension was calculated based on Equation 1 below.

Is the contact angle with water.

2) contact angle measurement

The contact angle with respect to distilled water was measured about the surface-treated PVDF membrane using the Sessile drop method.

The seseal drop method measures the wettability of fixed water droplets. The average value was measured by dropping a prescribed (0.1 μl) droplet onto the membrane and measuring the slope of the angle between the membrane surface and the droplet surface.

3) flow measurement

The amount of water penetrating the membrane was measured at a cross-sectional area of 124.69 cm ² , static pressure of 1 kgf and unit time of 1 minute.

4) Moisture absorption time measurement

The surface-treated PVDF membrane was measured for the degree of hydrophilization treatment in the inside by measuring the time (hygroscopic time, s / 1 μl) of 1 μl of water drop disappearing using a Sessile drop method.

Based on the seseal drop method, the time taken for the water droplets on the membrane surface to disappear completely into the membrane was measured.

PVDF membrane characteristics before surface treatment Surface tension (dyne / cm) Contact angle Flow rate (ml / min / cm 2) Moisture absorption time (s / μl) PVDF before treatment <0.1 130 0.1 to 0.3 ∞

PVDF membrane characteristics after surface treatment division Surface tension (dyne / cm) Contact angle Flow rate (ml / min / cm 2) Moisture absorption time (s / μl) Example 1 51.5 55 13-16 <0.8 Comparative Example 1 42.5 70 8 to 11 60-65 Comparative Example 2 33.5 85 3 to 5 > 3600

From the above results, the surface-treated PVDF membrane of the present invention confirmed the flow rate increase with the increase of the surface tension.

PVDF Membrane Characteristics According to Reaction Time division Response time (sec) Surface tension (dyne / cm) Contact angle Flow rate (ml / min / cm 2) Moisture absorption time (s / μl) Example 1 10 51.5 55 13-16 <0.8 Example 2 20 50.0 58 10 to 13 <1.2 Comparative Example 3 40 45.5 65 9-12 10 to 12 Comparative Example 4 60 42 71 7-10 21-23 Comparative Example 5 120 39 76 4 to 5 35-40

In addition, according to the preparation method of the present invention, as the PVDF membrane is surface treated, the contact angle to distilled water is lowered to 55 ° to 67 ° without surface damage for a short time, and the moisture absorption time is observed to be 1.0 to 1.5 s / μl, Surface tension of PVDF membrane surface is 51.5dyne / cm As mentioned above, it modified to the hydrophilic surface and confirmed the high flow characteristic.

As a result of the above, the present invention

First, a method of surface modification of a PVDF membrane maximized hydrophilicity by graft polymerization of a hydrophilic acrylic derivative bond to a main chain of a hydrophobic PVDF membrane in a bond-line polymer is provided.

Second, before the UV light irradiation, the pretreatment process was carried out by filling the alcohol solution containing the acrylic monomer and the photoinitiator not only to the surface of the PVDF membrane but also to the inside of the PVDF membrane through the air inflow method.

Third, from the method of the present invention, the surface hydrophilicity was improved, the moisture absorption time was shortened, and the PVDF membrane provided with high flow rate characteristics was provided.

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 spirit of the present invention, and such modifications and variations belong to the appended claims. .

Claims (12)

1) A polyvinylidene fluoride (PVDF) membrane having a pore size of 0.1 to 10 μm is first impregnated into an alcohol solution containing an acrylic monomer and a photoinitiator, 2) suctioning the solution present on the impregnated PVDF membrane surface into the PVDF membrane pores via an air inlet, 3) secondly impregnated the PVDF membrane in the alcohol solution containing the acrylic monomer and photoinitiator, 4) The surface modification method of the polyvinylidene fluoride membrane which removes the solvent at the temperature of 40-80 degreeC, and irradiates with UV light, and the PVDF membrane and an acryl-type derivative graft-polymerize. The method of claim 1, wherein the PVDF membrane of step 1) is supplied at a process rate of 0.5 to 5 m / min. The method of claim 1, wherein the solution of step 1) or step 3) comprises 10-50 g of an acrylic monomer and 0.1-1.0 g of a photoinitiator in 1 L of an alcohol solvent. The method of claim 3, wherein the acrylic monomer is any one selected from the group consisting of acrylic acid, methacrylic acid, and glycidyl methacrylate. 4. The method of claim 3, wherein said photoinitiator is 2,2-dimethoxy-2-phenylacetophenone. The method of claim 1, wherein step 2) is characterized in that the solution is sucked into the PVDF membrane pores due to the difference between the air pressure inside the apparatus and the air pressure outside the apparatus while the primary impregnated PVDF membrane passes through the air inlet apparatus. Surface modification method of the polyvinylidene fluoride membrane. 7. The polyvinylidene according to claim 6, wherein the air inlet device is made of a tubular roll having a porous suction pipe 4 formed on a general suction pipe 3 between the air inlet port 1 and the air outlet port 2. Method of surface modification of fluoride membrane. The surface modification method of the polyvinylidene fluoride membrane according to claim 1, wherein the UV light irradiation of step 4) is irradiated for 1 second to 10 minutes. UV light irradiation by the surface modification method of claim 1 to graft polymerization reaction of the PVDF membrane and the acrylic derivative to the surface modified to have a hydroxyl group (-OH) on the surface of the PVDF membrane, the surface tension is 50 ~ 64 dyne / cm Polyvinylidene fluoride membrane. 10. The polyvinylidene fluoride membrane according to claim 9, wherein the PVDF membrane has a contact angle of 55 ° to 67 °. The polyvinylidene fluoride membrane according to claim 9, wherein the moisture absorption time of the PVDF membrane is 1.0 to 1.5 s / μl. 10. The polyvinylidene fluoride membrane of claim 9 wherein the PVDF membrane maintains a tensile strength of 95% to 100% relative to the untreated UV PVDF membrane.

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