KR100392470B1 - Method for manufacturing microporous poly(vinylchloride) membrane and microporous poly(vinylchloride) manufactured thereby - Google Patents

Abstract

In the present invention, after impregnating and applying a mixed solution consisting of a polymer, a solvent and an additive to a polyester nonwoven fabric, the phase separation is induced by a constant humidity and dried in the manufacturing process of the membrane,

To a solution of chlorinated polyvinyl chloride in tetrahydrofuran (THF), a polymer solution is formed by adding 1-30% by weight of alcohol, which is well mixed with a solvent and acts as a nonsolvent for a polymer. Provided is a method for producing a microporous chlorinated polyvinyl chloride membrane, which is obtained by impregnating and applying a polyester nonwoven fabric, followed by drying at room temperature in an atmosphere having a relative humidity (based on a temperature of 25 ° C.) of 45-90%.

The porous polymer membrane thus prepared has a pore size of 0.01-0.5 μm, porosity of 25-87%, and a pure permeation flux of 13-8000 LMH.

Description

Microporous chlorinated polyvinyl chloride membrane and method for manufacturing the same {Method for manufacturing microporous poly (vinylchloride) membrane and microporous poly (vinylchloride) manufactured thereby}

The present invention relates to a method for producing a porous membrane used for filtration and the like. More specifically, the present invention relates to a method for producing a porous membrane that is adjusted to have a porosity and pore size of the membrane suitable for improving the permeability of pure water in the preparation of a porous membrane using a phase separation method.

The process methods for the preparation of the porous membrane include a thermally induced phase separation process, a non-solvent induced phase separation process, and a phase separation process according to a wet and dry process. The nucleus-growth (NG) mechanism in the metastable region located between the spinodals and the phase separation (SD) mechanism in the unstable region inside the spinodal are summarized (P. van de Witte et al., Journal of Membrane Science). , 117 (1996) 1-31) In general, the pore size and the interconnection of the pores are very important for improving the permeability of the fluid. The pores of the membrane prepared by the nucleus-growth (NG) mechanism in the metastable region exhibit closed pores and poor permeability, but the pores of the membrane due to the phase separation (SD) mechanism in the unstable region have high pore connectivity. It has a very good permeability (SWSong et al., Journal of Membrane Science, 98 (1995) 209-222). Therefore, if the non-solvent is added properly to induce the thermodynamic composition of the solution to be easily located in the unstable region, the permeation performance can be improved because the pores inside the membrane are interconnected. Meanwhile, the relative humidity may affect the pore growth. Crazy The higher the relative humidity, the higher the activity that can induce phase separation and the faster the adsorption of water on the surface of the polymer solution, which acts as a mechanism to speed up the phase separation. In this case, the high permeability is a characteristic of the membrane because the capacity to be processed per unit time increases, but the problem is that the permeability is good and the permeability is good so the selectivity decreases accordingly. The lower the technical value, the smaller the pore size and the excellent permeability, the higher the technical value, and the narrower the pore size distribution, which has a stable selectivity. Iso-propyl, a known technique for making porous membranes A polyvinyl chloride membrane (JP 58-88011) prepared by using alcohol as a non-solvent and controlling the structure of a nonwoven fabric has been reported, and a porous membrane is prepared by using non-solvent of ethyl alcohol and polyvinyl chloride (JP 47). The results have also been reported.

In the present invention, a solution prepared by completely dissolving chlorinated polyvinyl chloride in a solvent, tetrahydrofuran (THF), by adding water or alcohol to prepare a mixed solution and impregnating and applying it to a nonwoven fabric, a relative humidity of 45-90% The final membrane is prepared by inducing phase separation of the polymer under an atmosphere of (at 25 ° C. temperature). At this time, the choice of additives added in the polymer solution is limited due to the limitation of thermodynamic properties depending on the type of solvent and the polymer used. Since the added alcohol acts as a non-solvent, it increases the entanglement of the polymer chains, so that separation easily occurs in the high and low polymer concentration regions. At these two regions, agglomeration occurs in order to lower their own surface tension, so that in the region of high polymer concentration, they form a skeleton of the formed membrane, and the region of low concentration grows into pores inside the membrane. It is easily removed in the solution to increase the content fraction of the polymer in the solution to cause a viscosity increase and concentration polarization interferes with the formation of the other two phases may also be a factor that inhibits the formation of pores and permeability. However, the present inventors have found that a solution having a relatively high boiling point added to a nonsolvent can overcome the above problems.

As described above, when the porous membrane is manufactured according to the drying method under a constant humidity of the non-solvent-added polymer solution, the pore size is controlled by smoothly controlling the dynamic and thermodynamic phase separation mechanism according to the boiling point of the added non-solvent. It is also possible to obtain a membrane having a porous structure with high porosity.

Thus, the present invention forms a polymer solution by adding 1-30% by weight of alcohol, which is well mixed with a solvent and acts as a non-solvent for a polymer, to a solution of chlorinated polyvinyl chloride in tetrahydrofuran (THF). And impregnating and applying the polymer solution to a polyester nonwoven fabric, and then drying the product under an ambient humidity of 45-90% (based on a temperature of 25 ° C.) and atmosphere to obtain a microporous chlorinated polyvinyl chloride membrane. In the method of producing the membrane, the boiling point is 50-150 ° C., and by selecting an additive which acts as a non-solvent for the polymer, the porosity of the porous polymer membrane is 0.01-0.5 μm and the porosity is 25-87%. Chlorinated polyvinyl chloride polymer membrane, chlorination characterized in that the pure permeate flow rate of the porous polymer membrane is 13 to 8000LMH The present invention relates to a polyvinyl chloride polymer membrane, and to a method for preparing a microporous membrane, and a porous chlorinated polyvinyl chloride membrane having a controlled pore size and improved permeation flow rate of pure water, prepared by the method according to the present invention. The membrane has excellent permeability and can be applied to precision filtration.

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

Example 1-5

9.47 wt% chlorinated polyvinyl chloride completely dissolved in 90.53 wt% THF and 5.26 wt% alcohol was added to the solution to give a final 9 wt% chlorinated polyvinyl chloride / 5 wt% nonsolvent (alcohol or water) / 86 A mixed solution having a composition of wt% THF was prepared. After impregnating and applying this solution to a polyester nonwoven fabric, the phase separation was induced in an atmosphere of a temperature of 25 ° C. and a relative humidity of 70% to prepare a final membrane, and the pore size, porosity, and water permeability were measured. Indicated.

TABLE 1

***: Value measured by electron scanning microscope observation with mean pore diameter

**: Pr (porosity) = (1- ρ _v / ρ _p ) × 100 ( ρ _v : polymer density at 25 ℃, ρ _p : membrane density)

*: Average value of pure water permeation amount (LMH: 1 / m ² hr)

Compared with the results of Comparative Example 1, the addition of 5% by weight of non-solvent increases the porosity, while not significantly affecting the pore size. In addition, as the boiling point of the non-solvent used increased, permeability was generally improved.

Example 6-10

9.47% by weight of chlorinated polyvinyl chloride was completely dissolved in 90.53% by weight of THF, and 5.26% by weight of alcohol was added to the solution to form a final composition of 9% by weight of chlorinated polyvinyl chloride / 5% by weight of alcohol / 61% by weight of THF. The mixed solution having was prepared. After impregnating and applying the solution to the polyester nonwoven fabric, the final membrane was prepared by inducing phase separation under an ambient temperature of 90% (at 25 ° C) at room temperature and relative humidity, and measuring the pore size, porosity and water permeability. Table 2 shows.

TABLE 2

***: Value measured by electron scanning microscope observation with mean pore diameter

**: Pr (porosity) = (1- ρ _v / ρ _p ) × 100 ( ρ _v : polymer density at 25 ℃, ρ _p : membrane density)

*: Average value of pure water permeation amount (LMH: 1 / m ² hr)

Similar to the results of Example 1-5 and Comparative Example 1, it can be seen that the addition of the additive under the condition of 90% relative humidity does not significantly affect the pore size, but the water permeation rate is greatly increased. However, when the additive is not added, as shown in the results of Comparative Example 1 and Comparative Example 2, it can be seen that the membrane obtained under the condition of high relative humidity has a small pore. As it increases, the pore size decreases slightly and the porosity in the membrane increases, but it does not necessarily increase the permeability.However, when the nonsolvent is added as an additive to the membrane manufacturing process, the boiling point of the nonsolvent is a major factor in the pore connectivity. In particular, it can exhibit the best permeability, especially in Examples 8 and 10 with the highest boiling point.

Example 11-18

As can be seen from the results of Example 1-10, it was found that the higher the boiling point of the non-solvent (alcohol) used as the additive, the higher the permeation amount of pure water. This completely dissolves 18 wt% chlorinated polyvinyl chloride in 82 wt THF, and the solution of 60 wt% alcohol (n-propyl alcohol, n-butyl alcohol) and 40 wt% THF is dissolved in the solution under mutual stirring. Finally, a mixed solution having a composition of 9 wt% chlorinated polyvinyl chloride / 30 wt% alcohol / 61 wt% THF was prepared. The solution was impregnated and applied to a polyester nonwoven fabric, and the final membrane was prepared by inducing phase separation at a constant temperature of 25 ° C. under various relative humidity conditions, and the pore size, porosity and water permeation were measured. The results are shown in Table 3. It was.

TABLE 3

***: Value measured by electron scanning microscope observation with mean pore diameter

**: Pr (porosity) = (1- ρ _v / ρ _p ) × 100 ( ρ _v : polymer density at 25 ℃, ρ _p : membrane density)

*: Average value of pure water permeation amount (LMH: 1 / m ² hr)

As a result of Example 1-10, n-butyl alcohol having a relatively high boiling point was prepared without a non-solvent additive or by adding methyl alcohol, iso-propyl alcohol, n-propyl alcohol, water, etc. as a non-solvent. It can be seen that the permeability is higher than that of the membrane. In addition, it can be seen that as the content of the additive increases, the effect of the interconnection of the pores has a greater influence on the water permeation amount than the factors due to the size and distribution of the pores.

Comparative Example 1-2

9% by weight of chlorinated polyvinyl chloride was completely dissolved in 91% by weight of THF to prepare a pure polymer solution without mixing of the non-solvent additive. After impregnating and applying the solution to the polyester nonwoven fabric, the final membrane was prepared by inducing phase separation in an atmosphere of 70% and 90% relative humidity, respectively, and the pore size, porosity, and water permeability were measured. The results are shown in Table 4.

TABLE 4

***: Value measured by electron scanning microscope observation with mean pore diameter

**: Pr (porosity) = (1- ρ _v / ρ _p ) × 100 ( ρ _v : polymer density at 25 ℃, ρ _p : membrane density)

*: Average value of pure water permeation amount (LMH: 1 / m ² hr)

As can be seen in Table 4, as the relative humidity of the polymer solution that is not mixed with the additive is increased, the size of the pores of the membrane formed is reduced and the porosity increases to increase the permeate flow rate. In other words, it is thought that as the relative humidity increases, the small pores are connected to each other to increase the porosity, thereby promoting water permeation.

As described above, in the present invention, a porous membrane can be obtained from a chlorinated polyvinyl chloride solution containing a nonsolvent additive, and a pore size and porosity can be controlled by using a non-solvent having a high boiling point and controlling relative humidity. It is possible to fabricate a porous membrane with excellent permeability by increasing the interconnectability of the pores, which makes it possible to apply to microfiltration.

Claims (8)

In the manufacturing process of the membrane in which a mixed solution composed of a polymer, a solvent, and an additive is impregnated and applied to a polyester nonwoven fabric, and then induced phase separation by a constant humidity to dry it, In the above process, 1-30% by weight of water or alcohol is added as a non-solvent to a solution in which polyvinyl chloride is dissolved in tetrahydrofuran (THF) to form a polymer solution, and the polymer solution is impregnated and applied to a polyester nonwoven fabric. Thereafter, the step of drying under an atmosphere of a predetermined state humidity to form a microporous chlorinated polyvinyl chloride membrane, By selecting the boiling point of the non-solvent within 50-150 ° C. and the relative humidity within the range of 40-90% (based on 25 ° C.), the pore size is 0.01-0.5 μm with a porosity of 25-87% and a pure permeation flux of 13 Create a membrane that is -8000 LMH, A method of producing a microporous chlorinated polyvinyl chloride membrane, characterized in that to produce a membrane having a small pore size and high permeate flow rate by adjusting the boiling point and relative humidity of the non-solvent within the above range. delete The microporous chlorinated polyvinyl chloride membrane of claim 1, wherein the non-solvent alcohol is any one selected from the group consisting of methanol, ethanol, n-propyl alcohol, isopropyl alcohol, and n-butyl alcohol. Manufacturing method. delete delete The method of manufacturing a microporous chlorinated polyvinyl chloride film according to claim 1, wherein the relative humidity is 70-90%. The method of producing a microporous chlorinated polyvinyl chloride film according to claim 7, wherein the boiling point of the non-solvent is 90-150 ° C. The microporous chlorinated polyvinyl chloride film produced by the method according to any one of claims 1, 3, 7, and 8.