KR101530432B1 - Polymer composition for preparing acetylated alkyl cellulose membrane and preparation method of acetylated alkyl cellulose membrane using the same - Google Patents

Abstract

The present invention relates to a polymer composition for the production of an acetylated alkyl cellulose separation membrane containing an acetylated alkyl cellulose, a crystalline polymer, a surfactant and a poor solvent, and a process for producing an acetylated alkyl cellulose separation membrane using the same. The acetylated alkyl cellulose separator produced is excellent in mechanical properties, excellent in water permeability, and excellent in hydrophilicity and excellent in membrane fouling resistance, so that it is suitable for use as an acetylated alkyl cellulose separator.

Description

TECHNICAL FIELD [0001] The present invention relates to a polymer composition for preparing an acetylated alkyl cellulose separator, and a method for producing the same. [0002]

The present invention relates to a polymer composition for preparing an acetylated alkyl cellulose separator and a process for preparing an acetylated alkyl cellulose separator using the same, and more particularly, to a polymer composition comprising an acetylated alkyl cellulose polymer, a crystalline polymer and a surfactant, The present invention relates to a polymer composition for the production of an acetylated alkyl cellulose separator which can produce a separator having excellent water permeability and tensile strength, which is produced by a heat induction phase separation method, and a process for producing an acetylated alkyl cellulose separator using the polymer composition.

In recent years, there has been a growing interest in separation membranes because of the advantages of water quality stability, compact site, and automation in the water treatment process. Most membranes used in water treatment require strong durability and longevity, and membrane resistance is highly required for this purpose.

In the case of hydrophobic polymer membranes, the membranes are susceptible to membrane contamination. Separators using hydrophilic polymers are relatively stable against membrane contamination. Cellulose acetate, which is currently used as a separation membrane material, is excellent in membrane fouling resistance. However, since a base is used in a process for producing cellulose acetate, there is a disadvantage in that the polymer is decomposed and durability of the separation membrane, that is, mechanical strength is lowered.

Accordingly, there is an increasing demand for a membrane having high mechanical permeability and high membrane permeation resistance, while being excellent in mechanical strength and capable of completely removing pathogenic microorganisms.

Since acetylated alkyl cellulose has hydrophilic properties, it has a favorable aspect against stain resistance. However, since it is amorphous polymer, it behaves liquid-liquid demixing during the heat-induced phase separation process and thus, results in liquid-liquid phase separation continuous sectional structure. However, the bi-continuous cross-sectional structure has a higher density than the spherulite cross-section structure due to the solid-liquid demixing during the thermal-induced phase separation of the crystalline polymer. Therefore, in order to increase the permeation amount of the polymer, If the content is reduced to make the cross section of the porous membrane, there is a problem that the tensile strength is rapidly lowered.

DISCLOSURE OF THE INVENTION An object of the present invention is to overcome the problems of the prior art described above and one object of the present invention is to provide a polymer composition for producing an acetylated alkyl cellulose membrane having a high water permeation rate and excellent mechanical properties and membrane fouling resistance, And a method for producing an alkyl cellulose separator.

One aspect of the present invention relates to a polymer composition for producing an acetylated alkyl cellulose separator comprising an acetylated alkyl cellulose, a crystalline polymer, a surfactant, and a poor solvent.

Further, another aspect of the present invention relates to a composition comprising: acetylated alkylcellulose; Crystalline polymer; Preparing a spinning solution comprising a surfactant and a poor solvent; And a step of spinning the spinning solution and then forming a separation membrane by a heat-induced phase separation method of solidifying in a coagulation bath.

The acetylated alkylcellulose membrane prepared by the polymer composition and the method of the present invention is excellent in membrane fouling resistance due to the inherent hydrophilicity of the acetylated alkylcellulose material, The membrane can be used in various ways such as a hollow fiber membrane module, an immersion membrane module for a biofilm reactor, a chemical mixture separation module, and a pretreatment membrane module for seawater desalination by producing a membrane with excellent mechanical strength. The acetylated alkyl cellulose separator of the present invention can be applied to a next-generation high-efficiency separation process since deformation and deterioration do not occur even after long-term use while exhibiting processing performance.

FIG. 1 is a graph showing a comparison of the pure water permeability of a separation membrane according to the present invention and a separation membrane used as an acetylated alkyl cellulose or polyvinylidene fluoride alone.

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

One aspect of the present invention is directed to a composition comprising: acetylated alkylcellulose; Crystalline polymer; A surfactant, and a poor solvent, and a method for preparing a separator using a thermally induced phase separation method (TIPS) using the polymer composition.

The polymer composition for producing an acetylated alkyl cellulose separation membrane according to one aspect of the present invention comprises: acetylated alkyl cellulose; Crystalline polymer; Surfactants: and poor solvents.

The acetylated alkyl cellulose used in the present invention has hydrophilic properties, so that film contamination due to an organic material is reduced and a high transmittance is exhibited. As the acetylated alkylcellulose, it is preferable to use a polymer having a relatively large molecular weight ranging from 50,000 to 2,000,000. If the weight average molecular weight of the acetylated alkyl cellulose is less than 50,000, the strength after spinning is very weak, which is difficult to use as a separation membrane. When the weight average molecular weight exceeds 2,000,000, when the heat induction phase separation method using a poor solvent is used This is because the viscosity is too high to make the spinning solution.

The acetylated alkylcellulose used in the present invention refers to cellulose substituted with an alkyl group having 1 to 3 carbon atoms and an acetyl group. That is, cellulose having three hydroxy groups bonded to each other in the cellulose unit structure, and cellulose in which some of the three hydroxy groups are substituted with alkyl or acetyl is referred to as "acetylated alkyl cellulose" in the present invention.

The heat-induced phase separation method, which is one of the methods for producing a separator, is a method of producing a porous separator by causing liquid-solid phase separation and solidification by contacting a polymer solution dissolved at a high temperature with a low-temperature medium. When a separator is prepared by using the heat-induced phase separation method, the amorphous polymer forms a bi-continuous structure by liquid-liquid phase separation, while the crystalline polymer exhibits a high-liquid phase separation behavior to form a spherical crystal structure.

Generally, in the crystal structure of the spherical crystal, the density of the polymer is high, but the density of the polymer is low between the crystal and the crystal. Therefore, since the density of the polymer is low, The bi-continuous structure is more uniform than the spherical crystal structure, while the bi-contiuous membrane has a higher tensile strength, while the water permeation has more resistance, .

In the present invention, a separation membrane having excellent permeability and tensile strength is manufactured through a method of producing a hollow fiber membrane by a heat induction phase separation method using a spinning solution obtained by mixing an acetylated alkyl cellulose and a crystalline polymer, which are hydrophilic and amorphous polymers can do.

The crystalline polymer is a crystalline polymer having low gas permeability irrespective of the degree of crystallinity. Non-limiting examples of the crystalline polymer usable in the present invention include polyamide, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, Polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, and a thermotropic or liquid crystal liquid crystal polymer.

Since the crystalline polymer is hydrophobic, it is not uniformly dissolved when it is mixed with the hydrophilic acetylated alkylcellulose to make a spinning solution. When a surfactant is added to the dope solution, a mixed spinning solution of a hydrophobic crystalline polymer and a hydrophilic acetylated alkyl cellulose is present in a uniform single phase, and when the spinning solution is produced through heat induction phase separation, A separator having excellent tensile strength can be produced.

As the surfactant, any surfactant including an anionic surfactant, a cationic surfactant, a neutral surfactant, and a counter ionic surfactant can be used. Depending on the amount and type of surfactant, the size of the polymer dispersed particles is determined. When the amount of the surfactant is above the critical micelle concentration (CMC), a dispersed phase of the polymer is formed. An appropriate amount of the surfactant may vary depending on the kind of the surfactant and the solvent, but it is preferably added in the range of 0.1 to 10 wt% based on the total amount of the solution. Examples of the surfactant include, but are not necessarily limited to, sodium dodecyl sulfate, a straight chain alkyl sulfonate or a mixture thereof.

 As in the present invention, it is important to select an optimal poor solvent in order to apply the thermally induced phase separation (TIPS) using the acetylated alkyl cellulose and the crystalline polymer as the hydrophilic polymer material.

The poor solvent used in the heat-induced phase separation process serves to inhibit the formation of macrovoids in the separator and to maximize the pore size and porosity of the separator, and the temperature change, viscosity change, and ease of molding of the polymer composition . In the present invention, a poor solvent means that the resin can be dissolved at not more than 5% by weight at a low temperature of 60 캜 or lower, but can be used without limitation as long as it can dissolve at least 5% by weight in a high- have. The present invention relates to a process for the preparation of an acetylated alkylcellulose by the use of polyethylene glycol (PEG), triethylene glycol, ethylene glycol, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate ,? -butyrolactone, cyclohexanone, acetophenone, and isophorone may be used.

For the preparation of the polymer composition of the present invention, 10 to 30% by weight of acetylated alkylcellulose; 10 to 30% by weight of a crystalline polymer, 0.1 to 10% by weight of a surfactant; And 50 to 79.9% by weight of a poor solvent. If the content of the acetylated alkylcellulose is less than 10% by weight, the strength of the separation membrane is lowered. If the content of the acetylated alkylcellulose is more than 30% by weight, the viscosity of the polymer composition is too high to easily spin.

Another aspect of the present invention is a composition comprising: acetylated alkylcellulose; Crystalline polymer; Preparing a spinning solution comprising a surfactant and a poor solvent; And a step of spinning the spinning solution and then forming a separation membrane by a heat-induced phase separation method of solidifying in a coagulation bath.

The present invention will be described in more detail as follows. First, a spinning solution is prepared by mixing acetylated alkylcellulose, a crystalline polymer, a surfactant, and a poor solvent.

For purification of the polymer composition, the polymer composition may be heated and filtered to remove insoluble components. The purification process will be described in more detail. The polymer composition is heated to 100 to 200 ° C to completely dissolve the acetylated alkylcellulose, and then filtered to prepare a purified polymer composition.

The separation membrane can be produced by forming a membrane using the polymer composition prepared by the above method. In the present invention, a method for producing a hollow fiber membrane as a typical separation membrane will be described.

Considering that the melting point of the acetylated alkyl cellulose is approximately 170 ° C, the polymer composition is heated to a temperature within the range of 150 ° C to 170 ° C, which is the melting point of the acetylated alkyl cellulose, to prepare a spinning solution. If the heating temperature for the production of the polymer composition is less than 150 캜, complete dissolution does not occur, resulting in poor processability. If the heating temperature exceeds 170 캜, the polymer may be decomposed.

The spinning solution thus prepared is spinned in a nozzle for forming a hollow fiber membrane shape, and the spinning solution is phase-transformed to produce a hollow fiber membrane. In order to form the inner hole of the hollow fiber membrane when the spinning solution is radiated from the spinning nozzle,

A pump for dosing is injected into the nozzle for radiating the spinning solution. At this time, the temperature of the coagulating bath is preferably set in the range of 20 to 30 캜.

The porous separation membrane manufactured according to the present invention can be used in a water purifier, a pretreatment device for a seawater desalination process, a water softener, a water treatment device, a wastewater treatment device, or a food purification device.

Hereinafter, the present invention will be described in more detail by way of examples, but the scope of the present invention is not limited by the following examples.

Example

Comparative Example 1

A hollow fiber membrane was prepared by dissolving 25 wt% of acetylated methyl cellulose (AMC) and 75 wt% of triethylene glycol (TEG) at 160 ° C, spinning through a spinneret, and solidifying in a coagulation bath at 25 ° C.

Comparative Example 2

20 wt% of AMC and 80 wt% of TEG were melted at 160 DEG C to prepare a hollow fiber membrane in the same manner as in Comparative Example 1, and the performance was evaluated.

Comparative Example 3

25 wt% of polyvinylidene fluoride and 75 wt% of dimethyl phthalate (DMP) were dissolved at 160 ° C to prepare a hollow fiber membrane in the same manner as in Comparative Example 1, and the performance was evaluated.

Comparative Example 4

20 wt% of polyvinylidene fluoride and 80 wt% of DMP (dimethyl phthalate) were melted at 160 ° C to prepare a hollow fiber membrane in the same manner as in Comparative Example 1, and the performance was evaluated.

Example 1

15 wt% of acetylated methyl cellulose, 10 wt% of polyvinylidene fluoride (PVDF), 0.1 wt% of sodium dodecyl sulfate (SDS), and 74.9 wt% of triethylene glycol (TEG) The hollow fiber membranes were prepared in the same manner and evaluated for their performance.

Example 2

The hollow fiber membranes were prepared by dissolving 10 wt% of AMC, 10 wt% of PVDF, 0.1 wt% of SDS (Sodium Dodecyl Sulfate) and 79.9 wt% of TEG at 160 ° C.

Experimental Example: Evaluation of Physical Properties

The properties of the hollow fiber membranes prepared in Examples 1 and 2 and Comparative Examples 1 to 4 were measured by the following methods, and the results are shown in Table 1 below.

In this experiment, pure water permeation flow rate was measured by fabricating a module having a certain length and number of hollow fiber membranes, supplying pure water (20 ° C) in the water tank by Out-In method to the side of the module, And then measured in terms of unit time and permeation amount per unit membrane area. The tensile strength was measured by using a tensile strength tester, measuring the force at the time of cutting, and dividing by the cross-sectional area of the hollow fiber.

division Pure permeate flow rate (L / m ² · hr) The tensile strength Comparative Example 1  50 LMH 21 MPa Comparative Example 2 150 LMH  7 MPa Comparative Example 3 210 LMH  5.5 MPa Comparative Example 4 280 LMH  4 MPa Example 1 120 LMH  20 MPa Example 2 250 LMH  10 MPa

1 and 2, the acetylated alkyl cellulose separator of the present invention prepared in Examples 1 and 2 had a net permeation amount and mechanical strength higher than that of the acetylated alkyl cellulose separator prepared in Comparative Examples 1 to 4 .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the exemplary embodiments or constructions. The scope of which is defined in the following claims and their equivalents.

Claims (11)

10 to 30% by weight of acetylated alkylcellulose; 10 to 30% by weight of a crystalline polymer, 0.1 to 10% by weight of a surfactant; And 50 to 79.9% by weight of a poor solvent. ≪ RTI ID = 0.0 > 11. < / RTI >
The method of claim 1, wherein the crystalline polymers are selected from the group consisting of polyamides, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polyisocyanate, polyvinylidene fluoride, polytetrafluoroethylene, Wherein the polymer is selected from the group consisting of sulfides, sulfides, and sulfides.
The polymer composition according to claim 1, wherein the poor solvent is at least one selected from the group consisting of polyethylene glycol,? -Butyrolactone, cyclohexanone, acetophenone, and isophorone. .
The polymer composition of claim 1, wherein the surfactant is sodium dodecyl sulfate, a linear alkyl sulfonate, or a mixture thereof.
delete Acetylated alkylcellulose; Crystalline polymer; Preparing a spinning solution comprising a surfactant and a poor solvent; And
And a step of spinning the spinning solution and then forming a separation membrane by a heat induction phase separation method which solidifies in a coagulation bath.
7. The method of claim 6, wherein the spinning solution comprises 10 to 30% by weight of acetylated alkyl cellulose; 10 to 30% by weight of a crystalline polymer, 0.1 to 10% by weight of a surfactant; And 50-79.9 wt% of a poor solvent. ≪ RTI ID = 0.0 > 11. < / RTI >
7. The method of claim 6, wherein the surfactant is sodium dodecyl sulfate, a straight chain alkyl sulfonate, or a mixture thereof.
7. The method of claim 6, wherein the poor solvent is selected from the group consisting of polyethylene glycol, triethylene glycol, ethylene glycol, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate,? -Butylolactone, cyclohexanone, Wherein the alkylated cellulose is at least one selected from the group consisting of polyvinyl alcohol and polyvinyl alcohol.
The method according to claim 6, wherein the crystalline polymer is selected from the group consisting of polyamide, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polyisocyanate, polyvinylidene fluoride, polytetrafluoroethylene, Sulfide, and sulfide. The method for producing an acetylated alkyl cellulose separation membrane according to claim 1,
The method for producing an acetylated alkyl cellulose separation membrane according to claim 6, wherein the temperature of the coagulation bath is in a range of 20 캜 to 30 캜.

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