KR100321133B1 - Polypropylene hollow fiber membrane comprising a nucleating agent and method of the preparation thereof - Google Patents

Abstract

The present invention relates to a polypropylene hollow fiber membrane comprising a nucleating agent of 0.5 to 3% by weight of polypropylene, and a method for producing the hollow fiber membrane, which has an improved processability, porosity and resolution while having pores of uniform size. It can be usefully used as a separator.

Description

Polypropylene hollow fiber membrane comprising a nucleating agent and method of the preparation

The present invention relates to a polypropylene hollow fiber membrane comprising a nucleating agent and a method of manufacturing the same, and specifically, to a polypropylene having improved porosity, porosity, and separation ability while having pores of uniform size, including a predetermined weight of nucleating agent. It relates to a hollow fiber membrane and a method of manufacturing the same.

1 is a view schematically showing an apparatus for producing a polyolefin hollow fiber separator by a conventional melt spinning method. According to FIG. 1, after the polyolefin and the diluent are added to the mixer 2 at an appropriate ratio and melt-mixed for a predetermined time, the mixture is spun by a predetermined amount using a gear pump driven by a gear pump motor 6. Nitrogen gas from the nitrogen tank (5) is also fed to the spinneret (7) to make the hollow of the membrane. The mixture spun together with nitrogen from the spinneret 7 through the spinneret 8 falls through some cooling process in the air while the separation of its constituent polyolefin and diluent continues. This mixture is immersed in the coagulation bath 9, and the separation of the polyolefin and the diluent in the coagulation bath 9 continues to solidify the polyolefin to form hollow fibers. Subsequently, the formed hollow fiber is wound and wound at room temperature between the final two winding machines 10 through several winding machines, and then separated. The diluent remaining in the separated hollow fiber membrane is extracted, evaporated, and finally heat-treated. Manufacture the desert.

Phase separation in a two-component phase composition consisting of the polyolefin and the diluent is largely divided into liquid-liquid phase separation and solid-liquid phase separation. Liquid-liquid phase separation is induced due to thermodynamic instability of the system, and solid-liquid phase separation leads to phase separation with a solid polymer and a liquid diluent because the vitrification or crystallization temperature of the solution is higher than the phase separation temperature.

Conventionally, in order to improve the permeability of the formed hollow fiber membranes, research has been mainly conducted on the manufacturing parameters affecting the preparation of the membrane by liquid-liquid or solid-liquid phase separation. The present invention has been completed by discovering that it is possible to prepare hollow fiber membranes having improved porosity, porosity and resolution while having uniformly sized pores by adding a nucleating agent in desert production.

It is an object of the present invention to provide a polypropylene hollow fiber membrane having a uniform size of pores and having improved processability, porosity and resolution, and a method of manufacturing the same.

1 is a view schematically showing an apparatus for producing a polyolefin hollow fiber separator by a conventional melt spinning method,

Figures 2a, 2b and 2c is a photograph of the inner surface of the hollow fiber membrane prepared by varying the amount of nucleating agent, respectively, Figures 3a, 3b, 3c, and 4a, 4b, 4c are hollow corresponding to Figures 2a, 2b and 2c, respectively Outside surface and cross-section picture of the desert,

Figures 5a, 5b and 5c is a photograph of the outer surface of the hollow fiber membrane prepared by changing the temperature of the coagulation bath when no nucleating agent is added, Figures 6a, 6b and 6c is a change in the temperature of the coagulation bath when the nucleating agent is added Is a photo of the outer surface of the hollow fiber membrane prepared by

Figure 7a and 7b is a photograph of the outer surface of the hollow fiber membrane prepared for the case without heat treatment and the heat treatment, respectively,

8a, 8b and 8c are photographs of the outer surface of the hollow fiber membrane prepared by varying the winding rate, respectively.

9A, 9B and 9C are photographs of the outer surface of the hollow fiber membranes manufactured by varying the distance between the spinning nozzle and the coagulation bath, respectively.

<Brief Description of Drawings>

1: extruder motor 2: mixer

3: pressure gauge 4: valve

5: nitrogen tank 6: gear pump motor

7: spinneret 8: spinning nozzle

9: solidification tank 10: winding machine

In order to achieve the above object, the present invention provides a polypropylene hollow fiber membrane comprising a nucleating agent of 0.5 to 3% by weight of the polypropylene weight.

Further, in the present invention, after spinning and solidifying the molten mixture containing the polypropylene, nucleating agent and diluent to form a polypropylene hollow fiber containing the nucleating agent, the hollow fiber is stretched to have a winding rate of 476 to 579 It provides a method for producing the polypropylene hollow fiber membrane, including heat treatment at 100 to 140 ℃.

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

As used in the present invention, "lamellar" refers to the overlapping of linear polymer chains in multiple layers. The lamellar forms a uniform crystal lattice as the temperature of the polymer chains that are completely melted and disorderly dispersed at a high temperature decreases. It is produced as the chain grows in a constant direction and then folds in the process of going into a thermodynamically stable state, that is, changing from a melt state to a crystalline state.

Also used in the present invention refers to the aggregate of lamellae described above.

As a representative example of the nucleating agent used in the present invention, adipic acid, 1,2,3,4-dibenzylidene sorbitol, 1,2,3,4-bis (p-methylbenzylidene) sorbitol, 1,2, 3, 4-bis (p-ethylene sorbitol), bis (4-t- butylphenyl) sodium phosphate, talc, etc. are mentioned. The nucleating agent increases the crystallization temperature of the polymer by providing a nucleus in which the polymer can be easily crystallized, and increases the pore size and porosity of the region between the sparrites by controlling the number and size of the sparite, thereby increasing the water permeability significantly. It increases the melt viscosity to increase the processability, and increases the density of the film serves to improve the physical properties of the film.

According to the present invention, the nucleating agent may be added in an amount of 0.5 to 3% by weight of the polypropylene weight when the polypropylene and the diluent are mixed in the polypropylene hollow fiber membrane manufacturing process, and when added less than 0.5% by weight The effect of not being seen, when added in excess of 3% by weight may increase the pore diameter may limit the use of the membrane.

The polypropylene hollow fiber membrane of the present invention can be prepared according to a conventional method for producing a polymer hollow fiber membrane, including melt mixing, spinning, solidification, stretching and heat treatment of the raw materials.

According to the present invention, a polypropylene having a melt index of 0.1 to 30 may be used as a substrate of the membrane, and polypropylene may be used at 10 to 80% by weight of the total weight during melt mixing of the polypropylene and the diluent. Conventional diluents such as liquid paraffin, soybean oil, paraffin wax, peanut oil, olive oil, castor oil, dioctylphthalate (DOP) may be used as the diluent mixed with the nucleating agent and the polypropylene, and then separated upon solidification. Liquid paraffin and soybean oil may be used.

As the coagulating solution, not only all of the above diluents but also water can be used, and the temperature of the coagulating solution is usually adjusted in the range of 3 to 100 ° C. In the case of hollow fiber membranes containing no nucleating agent, the residence time in the liquid-liquid phase separation zone is relatively longer as the temperature of the coagulating solution increases, whereas the pore size increases when the nucleating agent is included. The decrease in promotes nucleation, i.e., the production of speralite and increases the pore size.

According to the present invention, the distance from the spinning nozzle to which the mixture of nucleating agent, polypropylene, and diluent is spun can be adjusted appropriately, and within the appropriate range, spherite grows as the distance between the spinning nozzle and the coagulation bath increases. More time is given to make the production of sparlite distinct, and the fibril structure is well formed between sparrites. The polypropylene containing the nucleating agent and the diluent are separated by the coagulation liquid in the coagulation bath, and the polypropylene is completely solidified to form hollow fibers.

The hollow yarns formed are wound while being stretched at room temperature between the final two winding machines through several stages of winding machines, and are preferably drawn to have a winding rate of 476 to 579 (coiling rate = winding speed / spinning speed). In general, as the coiling rate increases, the pore size of the membrane increases. When the coiling rate is less than 476, the pore size is too small, the water permeability is low, and when the coiling rate is larger than 579, the fibrils are broken.

According to the present invention, the wound hollow fiber membrane is separated from the winding machine to extract and evaporate the diluent remaining in the hollow fiber membrane, and when extracted, an aliphatic hydrocarbon such as ethyl alcohol, isopropyl alcohol, N-hexane, or a chlorinated hydrocarbon or a fluorinated hydrocarbon And halogenated hydrocarbons such as chlorinated fluorinated hydrocarbons, or freons. Subsequently, the hollow fiber membrane subjected to the above step may be finally heat-treated at 100 to 140 ° C. in order to remove the elastic recovery ability of the polypropylene and form a fibrillated structure between sparite wells.

The polypropylene hollow fiber membrane prepared according to the method of the present invention has an inner diameter of 100 to 500 μm, a film thickness of 10 to 200 μm, and a bubble point pressure measurement method (ASTM F316-80, E128-61). The measurement resulted in various pore sizes of 0.1 to 20 μm.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are not intended to limit the present invention, but are not limited thereto. Performance evaluation of the hollow fiber membranes prepared in Examples and Comparative Examples of the present invention was performed by the following method.

Bubble Point Pressure and Maximum Pore Diameter Measurements

Five hollow fiber membranes were potted with epoxy to completely block one side and nitrogen gas on the other side. After immersing the module in 30% by volume of ethanol solution for about 5 minutes, the pressure when the gas bubbles first emerge through the pores of the hollow fiber membrane while slowly injecting nitrogen gas was called bubble point pressure (kgf / cm ² ). At this time, the reason for using ethanol is to increase the wettability of the hollow fiber membrane in consideration of the hydrophobic polypropylene. The maximum pore diameter (μm) of the hollow fiber membrane was obtained by substituting the measured bubble point pressure into the Young-Laplace equation, which is a correlation between the bubble point pressure and the maximum pore diameter.

Reference Example 1: Temperature Change in a Solidification Bath

After melting and mixing polypropylene having a melt viscosity of 2 and soybean oil (diluent) at 170 to 240 ° C. to make 40% by weight of polypropylene, the mixture was spun, and the spun mixture was separated and solidified using water as a coagulant. (Distance between the radiation nozzle and the solidification bath = 150 cm). At this time, the mixture of polypropylene and soybean oil is divided into a case in which 2% by weight of adipic acid is added as a nucleating agent and a case in which no polycarbonate is added, and the temperature of the coagulation bath is 3, 60, and 100 as shown in Table 1 below. The experiment was performed while changing to ℃.

The hollow fiber thus formed by solidification was wound up and separated while being stretched at room temperature at a winding rate of 476, and the soybean oil remaining in the hollow fiber membrane was extracted and evaporated with Freon 141B. The hollow fiber membrane thus formed was finally heat treated at 120 ° C. to prepare a hollow fiber membrane. The maximum pore diameter (μm) was measured according to the water permeation rate (ml / min bar cm ² ) and the bubble point pressure (kgf / cm ² ) of the prepared hollow fiber membrane, and the results are shown in Table 1 below.

Temperature of the coagulation bath If no nucleating agent is added If nucleating agent is added Water transmission Bubble point pressure Maximum pore diameter Water transmission Bubble point pressure Maximum pore diameter 3 ℃ 0.41 2.20 0.49 11.89 0.79 1.36 60 ℃ 0.46 1.55 0.69 6.99 1.29 0.83 100 ℃ 1.07 1.31 0.82 6.58 1.42 0.76

Figures 5a, 5b and 5c is a photograph of the outer surface of the hollow fiber membrane prepared by changing the temperature of the coagulation bath when no nucleating agent is added, Figures 6a, 6b and 6c is a change in the temperature of the coagulation bath when the nucleating agent is added The outer surface photograph of the hollow fiber membrane manufactured by From Table 1 and FIGS. 5 and 6, when the nucleating agent is not added, the pore size increases as the temperature of the coagulation bath increases, whereas when the nucleating agent is added, the spherorite is produced as the temperature of the coagulation bath decreases. This can be seen that the pore size increases and the fibril structure is well formed.

REFERENCE EXAMPLE 2 Distance Change Between Spinning Nozzle and Solidification Bath

After melting and mixing polypropylene having a melt viscosity of 2 and a liquid paraffin (diluent) at 170 to 240 DEG C so that 50% by weight of polypropylene is added thereto, 2% by weight of adipic acid as the nucleating agent is added thereto. The mixture was spun and the spun mixture was separated and solidified using water at room temperature as the coagulation solution. At this time, the experiment was performed while changing the distance between the spinning nozzle and the coagulation bath to 45, 100 and 150 cm. The hollow fiber formed by coagulation was treated in the same manner as in Reference Example 1 to prepare a hollow fiber membrane.

9A, 9B and 9C are external surface photographs of hollow fiber membranes manufactured by changing the distance between the spinneret and the coagulation bath to 45, 100 and 150 cm, respectively. As the distance between the spinneret and the coagulation bath increases, Clear and fibrillated structures formed well.

Reference Example 3: Effect of the nucleating agent on the melt viscosity

A polypropylene having a melt viscosity of 2 and a liquid paraffin (diluent) were melt mixed at 170 to 240 ° C. so that 40% by weight of polypropylene was added, and 0.5% by weight of adip was not added to the nucleating agent. In the case of adding the acid as nucleating agent, the correlation between the melt viscosity (Pa · s) according to the temperature change was investigated and shown in Table 2 below.

160 ℃ 170 ℃ 180 ℃ 190 ℃ 200 ℃ If no nucleating agent is added 174.31 152.34 138.13 128.59 124.38 If nucleating agent is added 183.47 167.87 150.08 138.90 135.40

From the above Table 2, both cases showed a tendency to increase the melt viscosity as the temperature is lowered, but the addition of the nucleating agent generally has a higher melt viscosity than the case where no nucleating agent is added, thereby improving the processability by adding the nucleating agent. It can be seen.

Examples 1 to 4, and Comparative Examples 1 and 2: Change in the amount of nucleating agent used

A hollow fiber membrane was prepared in the same manner as in Reference Example 1, except that water at room temperature was used as a coagulation solution and the amount of adipic acid serving as a nucleating agent was changed as shown in Table 2 below. The maximum pore diameter (μm) was measured according to the water permeation rate (ml / min bar cm ² ) and the bubble point pressure (kgf / cm ² ) of the prepared hollow fiber membrane, and the results are shown in Table 3 below.

Nucleating Agent Consumption (Based on Polypropylene Weight) Water transmission Bubble point pressure Maximum pore diameter Comparative Example 1 0 0.33 1.30 0.83 Example 1 0.5 wt% 3.50 0.83 1.31 Example 2 1 wt% 9.89 0.72 1.49 Example 3 2 wt% 11.89 0.68 1.58 Example 4 3 wt% 11.98 0.66 1.62 Comparative Example 2 4 wt% 12.1 0.45 2.38

2A, 2B and 2C are internal surface photographs of the hollow fiber membranes prepared by changing the amount of nucleating agent to 0, 0.5 and 1% by weight, respectively, and FIGS. 3A, 3B and 3C, and 4A, 4B and 4C are shown in FIGS. The external surface and cross-sectional photograph of the hollow fiber membranes corresponding to 2b and 2c. From Table 3 and FIGS. 2, 3 and 4, the addition of the nucleating agent promoted the production of spherite, and increased the pore size and the fibril structure, when the nucleating agent was not added (Comparative Example 1). It can be seen that the formation of the well, and as the amount of nucleating agent increases, the size of the spherite is slightly reduced and the pore size is slightly increased. However, when 3% by weight or more of the nucleating agent was added to the polypropylene weight (Comparative Example 2), the maximum pore diameter was larger than the intended use.

Example 5 and Comparative Example 3: presence or absence of heat treatment

The same method as in Reference Example 1, except that water at room temperature was used as a coagulation solution, and adipic acid as a nucleating agent was used in an amount of 1% by weight of polypropylene, and the final heat treatment was performed. A hollow fiber membrane was prepared. The maximum pore diameter (μm) was measured according to the water permeation rate (ml / min bar cm ² ) and the bubble point pressure (kgf / cm ² ) of the prepared hollow fiber membrane, and the results are shown in Table 4 below.

Heat treatment presence Water transmission Bubble point pressure Maximum pore diameter Example 5 ○ 5.01 0.96 1.13 Comparative Example 3 × 4.52 1.15 0.93

7A and 7B are external surface photographs of the hollow fiber membranes prepared for the case where the heat treatment is not performed and the case where the heat treatment is performed. Table 4 and FIG. 7 show that when the heat treatment is not performed (Comparative Example 3), when the membrane shrinks, the pore size is small and the fibril structure is hardly formed, whereas when the heat treatment is performed (Example 5), the pore size It can be seen that is increased and the fibril structure is well formed.

Examples 6 to 8, and Comparative Examples 4 and 5: winding rate change

Hollowed in the same manner as in Reference Example 1, except that water at room temperature was used as a coagulation solution, adipic acid serving as a nucleating agent was used in an amount of 1% by weight of polypropylene, and the winding ratio was changed as shown in Table 5 below. Desert was prepared. The maximum pore diameter (μm) was measured according to the water permeation rate (ml / min bar cm ² ) and the bubble point pressure (kgf / cm ² ) of the manufactured hollow fiber membrane, and the results are shown in Table 5 below.

Coiling rate Water transmission Bubble point pressure Maximum pore diameter Comparative Example 4 420 3.34 1.21 0.89 Example 6 476 5.01 0.95 1.13 Example 7 528 5.29 0.80 1.34 Example 8 579 9.90 0.72 1.49 Comparative Example 5 581 Fibril is broken

8A, 8B and 8C are external surface photographs of the hollow fiber membranes prepared by changing the winding ratios to 476, 528 and 579, respectively. From Table 5 and Figure 8, it can be seen that the pore size increases as the winding rate increases, but when the winding rate is less than 476 (Comparative Example 4), the permeability is too small, the winding rate is greater than 579 In the case (Comparative Example 5), the fibrils were broken.

The polypropylene hollow fiber membrane according to the present invention can be usefully used as a separation membrane having an improved processability, porosity and resolution while having a uniform size of pores by including an appropriate amount of the nucleating agent.

Claims (5)

After spinning the melt mixture containing polypropylene, nucleating agent and soybean oil as diluent and solidifying by contact with coagulating liquid, the solidified hollow fiber is drawn to a winding rate of 476 to 579, and the remaining diluent is extracted and then removed. Polypropylene hollow fiber membrane produced by heat treatment at 100 to 140 ℃. The method of claim 1, The nucleating agent is adipic acid, 1,2,3,4-dibenzylidene sorbitol, 1,2,3,4-bis (p-methylbenzylidene) sorbitol, 1,2,3,4-bis (p-ethylene Sorbitol), bis (4-t-butylphenyl) sodium phosphate or talc. After spinning the melt mixture containing polypropylene, nucleating agent and soybean oil as diluent and solidifying by contact with coagulating liquid, the solidified hollow fiber is drawn to a winding rate of 476 to 579, and the remaining diluent is extracted and then removed. A method for producing a polypropylene hollow fiber membrane, comprising heat treatment at 100 to 140 ° C. The method of claim 3, wherein The nucleating agent is adipic acid, 1,2,3,4-dibenzylidene sorbitol, 1,2,3,4-bis (p-methylbenzylidene) sorbitol, 1,2,3,4-bis (p-ethylene Sorbitol), bis (4-t-butylphenyl) sodium phosphate or talc. delete