KR101811540B1 - Composition for separation membrane, method for separation membrane using the same, separation membrane prepared therefrom and apparatus for purifying water - Google Patents

Abstract

A composition for forming a separation membrane according to the present invention comprises 20 to less than 40 wt% of a vinylidene fluoride resin, 5 to 20 wt% of a suitable solvent, 25 to 73.9 wt% of a plasticizer, 0.1 to 5 wt% of acetylated methylcellulose, and 1 to 10 wt% of a hydrophilic additive. An objective of the present invention is to provide a composition for forming a separation membrane having excellent mechanical strength and water permeability, a separation membrane production method using the same, a separation membrane, and a water treatment apparatus.

Description

TECHNICAL FIELD The present invention relates to a composition for forming a membrane, a method for preparing a membrane using the same, a membrane, and a water treatment apparatus. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for forming a membrane,

The present invention relates to a composition for forming a separation membrane, a separation membrane production method using the same, a separation membrane, and a water treatment apparatus.

With the development of the industry and population growth, interest in efficient water use and treatment technologies is increasing. In recent years, membrane technology has been increasingly applied to ensure water quality stability in water treatment, under-wastewater treatment, and seawater desalination. Particularly, the hollow fiber membrane has a high area per unit volume, few membrane fouling, and is easy to wash.

The separator can be made of various components, but the polyvinylidene polymer is widely used because of its excellent chemical resistance and strength. However, since the polyvinylidene-based polymer material is a hydrophobic material, the water permeability is low.

Efforts have been made to improve the water permeability of the separator, but if the size of the pore increases, the strength and pressure resistance of the separator deteriorate.

Therefore, a separator having excellent water permeability is required without deteriorating pressure resistance, chemical resistance and strength.

It is an object of the present invention to provide a composition for forming a separation membrane having excellent mechanical strength and water permeability, a separation membrane production method using the same, a separation membrane, and a water treatment apparatus.

The above and other objects of the present invention can be achieved by the present invention described below.

One aspect of the present invention relates to a composition for forming a membrane.

According to one embodiment, the composition for forming a separation membrane comprises 20 to less than 40% by weight of a vinylidene fluoride resin, 5 to 20% by weight of a suitable solvent, 29 to 73.9% by weight of a plasticizer and 0.1 to 1% by weight of acetylated methylcellulose, , And 1 to 10% by weight of a hydrophilic additive.

The vinylidene fluoride resin may have a weight average molecular weight of 300,000 or more.

The two solvents may be selected from N-methyl-2-pyrrolidone, dimethylformamide, N, N'-dimethyl acetamide, (Dimethylsulfoxide), and hexamethylphosphoric triamide.

The plasticizer may include a polyester plasticizer.

The hydrophilic additive may be selected from the group consisting of polyvinylpyrrolidone (PVP), ethylene glycol, polyethylene glycol (PEG), a hydrophilic polymer having at least one (meth) acrylate group introduced therein, glycerol, polyacrylonitrile (PAN), polyethylene oxide (PEO) And polyvinyl acetate (PVAc).

Another aspect of the present invention relates to a method for producing a membrane.

In one embodiment, the separation membrane manufacturing method includes the steps of: stirring the composition for forming a separation membrane; discharging the composition for forming a separation membrane through a spinning channel to form a separation membrane in the form of a hollow fiber; .

In the separation membrane production method, the stirring may be performed at 160 ° C to 220 ° C.

In the separation membrane production method, the solidification may be performed by injecting the hollow fiber type separation membrane into a coagulation bath containing at least one of a good solvent and a non-solvent.

The separation membrane production method may further include a step of solidifying and then stretching.

Another aspect of the present invention relates to a separation membrane.

In one embodiment, the separation membrane can be produced by the separation membrane production method, and can have a water permeability of 1000 LMH or more and a tensile strength of 1.2 kgf / fiber or more.

The separation membrane may have a hollow shape.

The separation membrane may have a mesh type crystal structure.

The separation membrane may have an average pore size of 0.05 탆 to 0.3 탆.

Another aspect of the present invention relates to a water treatment apparatus.

The water treatment apparatus according to one embodiment may include the separation membrane.

The present invention provides a composition for forming a separation membrane having excellent mechanical strength and water permeability, a separation membrane production method using the same, a separation membrane, and a water treatment apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electron microscope image of an enlarged cross section of the hollow fiber membrane of Example 1 of the present invention. FIG.
2 is an electron microscope image of a cross section of the hollow fiber membrane of Comparative Example 1 of the present invention.

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

In the following description of the present invention, detailed description of known related arts will be omitted when it is determined that the gist of the present invention may be unnecessarily obscured by the present invention.

In the case where the word 'includes', 'having', 'done', etc. are used in this specification, other parts can be added unless '~ only' is used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise.

Also, in interpreting the constituent elements, even if there is no separate description, it is interpreted as including the error range.

In the present specification, 'X to Y' representing the range means 'X or more and Y or less'.

Composition for forming a membrane

In one embodiment of the present invention, the composition for forming a separation membrane comprises 20 to less than 40% by weight of a vinylidene fluoride resin, 5 to 20% by weight of a positive solvent, 29 to 73.9% by weight of a plasticizer and 0.1 to 5% by weight of acetylated methylcellulose, , And 1 to 10% by weight of a hydrophilic additive.

Hereinafter, each component of the composition for forming a separation membrane will be specifically described.

The vinylidene fluoride-based polymer resin may include at least one of a vinylidene fluoride homopolymer and a vinylidene fluoride copolymer. Specifically, it may contain at least one of tetrafluoroethylene, hexafluoropropylene, trifluoroethylene or a copolymer of trifluoroethylene and chlorofluorocarbon.

The vinylidene fluoride-based polymer resin may be contained in the composition for forming a separation membrane in an amount of 20 wt% or more and less than 40 wt%, specifically 25 to 35 wt%. If the content of the vinylidene fluoride polymer resin in the composition for forming a separator is less than 20% by weight, it may be difficult to sufficiently secure the mechanical properties and chemical resistance of the separator, or the separator may not be easily formed. If the content of the vinylidene fluoride polymer resin in the composition for forming a separation membrane is more than 40% by weight, the pores formed in the separation membrane may become very small and water treatment efficiency may be lowered.

The both solvents can sufficiently dissolve the vinylidene fluoride-based polymer resin contained in the composition for forming a separation membrane, and can give an appropriate viscosity required for the separation membrane.

The two solvents can be used without limitation as long as they can dissolve the vinylidene fluoride-based polymer resin. For example, the two solvents may be N-methyl-2-pyrrolidone, dimethylformamide, N, N'-dimethyl acetamide, , Dimethylsulfoxide, and hexamethylphosphoric triamide. ≪ Desc / Clms Page number 7 >

The two solvents may be contained in the composition for forming a separation membrane in an amount of 5% by weight to 20% by weight, specifically 7% by weight to 15% by weight. If the content of the good solvent in the composition for forming a separation membrane is less than 5% by weight, the flowability of the composition may be lowered, and accordingly, the stirring temperature must be increased. If the content of the good solvent in the composition for forming a separation membrane is more than 20% by weight, the pores formed in the separation membrane become very large and water treatment performance may be deteriorated.

The plasticizer can dissolve the vinylidene fluoride-based polymer resin at a high temperature. The plasticizer may have a viscosity of 300 to 4,000 cps, specifically 2,000 cps to 3,500 cps. The separation membrane formed from the composition containing the plasticizer having the viscosity range described above can improve the porosity of the membrane and improve the flowability of the spinning solution.

The plasticizer may include at least one of a polyester-based plasticizer, a phthalic acid-based plasticizer, an adipic acid-based plasticizer and a trimellitic acid-based plasticizer. The plasticizer may be a polyester plasticizer in terms of the porosity of the separation membrane (for example, hollow fiber membrane) and the flowability of the spinning solution.

The polyester plasticizer may be a polyester containing a dicarboxylic acid and a diol as repeating units. The polyester plasticizer may have a weight average molecular weight of 500 to 4,000, specifically 1,500 to 3,500. In the above molecular weight range, the polyester-based plasticizer has an advantage of improving the porosity of the hollow fiber membrane and the flowability of the spinning solution.

The dicarboxylic acid may be a linear and / or cyclic aliphatic dicarboxylic acid. Specifically, the dicarboxylic acid may be a linear alkylene group having 1 to 20 carbon atoms or a dicarboxylic acid containing a branched alkylene group having 3 to 20 carbon atoms. For example, the dicarboxylic acid containing a linear alkylene group having 1 to 20 carbon atoms or a branched alkylene group having 3 to 20 carbon atoms is preferably a dicarboxylic acid selected from the group consisting of ethylene dicarboxylic acid, 1,3-propane-dicarboxylic acid, Butane dicarboxylic acid, 1,4-pentanedicarboxylic acid, 1,5-pentanedicarboxylic acid, 1,6-hexanedicarboxylic acid, 3- Methyl pentane-1,4-dicarboxylic acid, 2,2,4-trimethylpentane-1,3-dicarboxylic acid, 2-ethylhexane-1 , 3-dicarboxylic acid, 2,2-diethylpropane-1,3-dicarboxylic acid, and the like, but not limited thereto.

The diol may include a linear alkylene group having 1 to 20 carbon atoms or a diol having a branched alkylene group having 3 to 20 carbon atoms. For example, the diol comprising the linear alkylene group having 1 to 20 carbon atoms or the branched alkylene group having 3 to 20 carbon atoms may be at least one member selected from the group consisting of ethylene glycol, 1,3-propane-diol, 1,3-butanediol, , 1,4-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methylpentane-2,4-diol, 2-methylpentane- 1,3-diol, 2-ethylhexane-1,3-diol, 2,2-diethylpropane-1,3-diol, and the like.

The plasticizer may be contained in the composition for forming a separator in an amount of 29 to 73.9% by weight, specifically 35 to 70% by weight. If the content of the plasticizer in the composition for forming a separation membrane is less than 25% by weight, the viscosity of the composition is low, and the separation membrane is not easily formed, and water permeability is decreased due to insufficient pores. If the content of the plasticizer in the composition for forming a separation membrane exceeds 73.9% by weight, the strength of the separation membrane is lowered.

The acetylated methylcellulose is included in the composition for forming a separation membrane and serves to improve the hydrophilicity of the separation membrane. Specifically, the acetylated methylcellulose has a large amount of hydrophilic groups such as hydroxy groups, and thus the hydrophilicity of the separation membrane can be improved with a small amount, and the water permeability can be improved while maintaining the chemical resistance and strength of the separation membrane.

The acetylated methylcellulose may be contained in the composition for forming a separation membrane in an amount of 0.1 to 5% by weight, specifically 1 to 3% by weight. In the above content range, the separating membrane can have higher hydrophilicity and water permeability can be improved.

The hydrophilic additive can improve the hydrophilicity and water treatment efficiency of the separation membrane. Examples of the hydrophilic additive include polyvinylpyrrolidone (PVP), ethylene glycol, polyethylene glycol (PEG), hydrophilic polymers having at least one (meth) acrylate group introduced therein, glycerol, polyacrylonitrile (PAN) Oxide (PEO) and polyvinyl acetate (PVAc).

The hydrophilic additive may be included in the composition for forming a separation membrane in an amount of 1 to 10% by weight, specifically 1 to 8% by weight. If the content of the hydrophilic additive in the composition for forming a separation membrane is less than 1% by weight, hydrophilicity may not be sufficient and water permeability may be lowered. If the content of the hydrophilic additive in the composition for forming a separation membrane exceeds 10% by weight, the mechanical strength of the separation membrane may be lowered.

Meanwhile, the composition for forming a separation membrane may further include an additional additive (excluding the hydrophilic additive) in order to control physical properties and uses of the separation membrane to be produced, the shape and size of the pores formed on the surface or inside of the separation membrane. Additional additives may include conventional components capable of achieving this purpose, such as polyoxyethylene-polyoxypropylene block copolymer, lithium chloride (LiCl), lithium perchlorate (LiClO ₄ ), methanol, ethanol, Isopropanol, acetone, phosphoric acid, propionic acid, acetic acid, pyridine, polyvinylpyridine and the like may be used singly or in combination. The additional additive may be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the composition for forming a separation membrane.

Membrane manufacturing method

The method for manufacturing a separation membrane according to one embodiment of the present invention includes the steps of: stirring the composition for forming a separation membrane; discharging the composition for forming a separation membrane through a spinning channel to form a separation membrane in the form of a hollow fiber; As shown in FIG.

The step of stirring the composition for forming a separator is a step of sufficiently dissolving and / or mixing the components of the composition in a good solvent. The stirring is performed at 160 to 220 캜, specifically, at 170 to 210 캜 for 2 to 8 hours , Specifically, heating and stirring for 2 hours to 6 hours. Within this range, a viscosity suitable for spinning can be maintained, and uniform pores can be sufficiently formed in the separation membrane.

In the step of forming the separation membrane-forming composition by discharging the composition for forming a separation membrane through a spinning channel, the spinning-out may be performed using a spinneret having an inner channel and an outer channel. Specifically, the composition for forming a separation membrane may be discharged into the outer passage, and the inner coagulating solution may be discharged into the inner passage. In the case of using the spinneret, a hollow-fiber separator can be formed without using an inner coagulating solution.

The internal coagulating solution may generally be a composition comprising at least one of a good solvent for the polymer and a non-solvent.

In embodiments, the internal coagulating solution may comprise 10 to 70% by weight of at least one positive solvent of N-methylpyrrolidone and dimethylacetamide, based on 100% by weight of the internal coagulating solution, and the balance of non-solvent. In this content range, damage to the inner surface of the hollow fiber membrane can be prevented, and the porosity inside the hollow fiber membrane can be prevented from lowering. The non-solvent may include at least one of water, ethylene glycol, an alcohol solvent, a ketone solvent, and a polyalkylene glycol.

The step of solidifying the hollow fiber type separation membrane may be performed by injecting the hollow fiber type separation membrane into a coagulation bath containing at least one of a good solvent and a non-solvent to solidify the hollow fiber type separation membrane.

The solidifying step is a step of forming a film according to the coagulating bath treatment. Specifically, the discharged composition for forming a separation membrane can be precipitated in a non-solvent to form internal pores and to produce a membrane. The coagulation bath may include a non-solvent which does not dissolve both the solvent and the polymer membrane.

The two solvents may be, for example, N-mentyl-2-pyrrolidone, dimethylformamide, N, N'-dimethyl acetamide, , Dimethylsulfoxide, and hexamethylphosphoric triamide. ≪ Desc / Clms Page number 7 >

For example, water, glycol, and the like may be used as the non-solvent, and a coagulation solvent in which water, water and an organic solvent or water and glycol are mixed may be used. More specifically, . The temperature of the coagulation solvent used may be from 0 캜 to 90 캜, specifically from 5 캜 to 50 캜.

In another embodiment, the separation membrane manufacturing method may further include the steps of stirring the composition for forming a separation membrane, and then removing bubbles before discharging the dispersion composition to the spinning channel.

In still another embodiment, the separation membrane production method may further include the step of solidifying and then stretching.

The stretching may be dry stretching, and in this case, the mechanical strength and water permeability are improved. The dry stretching may be performed by an inter-roll stretching method, a heating roll stretching method, a compression stretching method or a tenter stretching method or a batch jig stretching method.

The inter-roll stretching method refers to a method of stretching the coagulated composition through two pairs of rollers having different rotational speeds. In addition, the batch jig stretching method refers to a method in which a PVDF hollow fiber membrane precursor is fixed on a pair of jigs, and one or both of the pair of jigs is stretched by moving the gap between the two jigs. The heating roll stretching method, the compression stretching method, or the tenter stretching method can be carried out by a conventionally known method.

Specifically, the dry stretching may be performed by passing the coagulated composition between two pairs of rollers having different rotational speeds. The stretching speed is 3 to 30 m / s, the stretching temperature is 10 to 50 ° C, the elongation is 30 % To 300%. Specifically, the dry stretching can be performed under the condition of an elongation of 50% to 200%. Stable stretching is possible in the above-mentioned range.

The separation membrane manufacturing method may further include washing and drying the resultant of solidifying (and / or stretching) the hollow fiber type separation membrane. Specifically, the resultant product of the solidification (and / or stretching) step is washed with a solvent that does not dissolve and dried at a predetermined temperature to finally obtain a polymer membrane (for example, hollow fiber membrane). For washing, acetone, methanol, ethanol, water and the like can be used. For example, water at 10 ° C to 90 ° C can be used. Further, after the washing, the resultant is dried at a temperature of 10 ° C to 200 ° C to finally produce a microporous polymer membrane (for example, a hollow fiber membrane).

Membrane

The separation membrane according to one embodiment of the present invention may be one produced by the separation membrane production method.

In an embodiment, the separation membrane has a mesh-type crystal structure by the separation membrane production method, so that the water permeability is excellent. The mesh type crystal structure refers to a structure in which resin solid components are connected in a three-dimensional network shape. The mesh-type crystal structure includes pores formed by partitioning the resin solid constituting the mesh. For example, the separator may have an average pore size of 0.05 탆 to 0.3 탆, specifically 0.08 탆 to 0.2 탆. In the average pore size range, the separator has excellent water permeability and water treatment efficiency.

In addition, since the separation membrane contains acetylated methyl cellulose having a large number of hydrophilic groups, the hydrophilicity of the separation membrane can be improved by a small amount, and the water permeability can be improved while maintaining the chemical resistance and strength of the separation membrane.

The separator preferably has a water permeability of at least 1000 LMH / bar, such as 1000 LMH / bar to 5,000 LMH / bar, specifically 1100 LMH / bar to 4,000 LMH / bar, more specifically 2000 LMH / bar to 4,000 LMH / More specifically from 2500 LMH / bar to 3500 LMH / bar.

The separator had a tensile strength of 1.2 kgf / fiber. For example, 1.2 kgf / fiber to 10 kgf / fiber, specifically 1.5 kgf / fiber to 9 kgf / fiber.

Water treatment  Device

The water treatment apparatus according to an embodiment of the present invention may include the separation membrane. The water treatment apparatus including the separation membrane has an advantage in that the mechanical strength is excellent, the life of the water treatment apparatus can be prolonged, the water permeability is excellent, and the water treatment efficiency is excellent.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

Example

Example  One

30% by weight of polyvinylidene difluoride (PVDF) and 54% by weight of a polyester plasticizer were stirred and mixed at 190 DEG C for 3 hours, and 10% by weight of N-methyl-2-pyrrolidone, 5% by weight of povidone (PVP) and 1% by weight of acetylated methyl cellulose (AMC) were mixed to prepare a composition for forming a separation membrane.

The composition for forming a separation membrane was discharged into a coagulation tank containing water through an outer passage of the spinneret and solidified to prepare a preliminary separation membrane. (I do not use my coagulating liquid)

The solidified preliminary separation membrane was passed through a washing tank and wound at the downstream end. The plasticizer was dipped in a dichloromethane solution for 24 hours, and the hollow fiber membrane was prepared by dry stretching at a room temperature and a 150% stretching ratio. 1 (magnification: 50 times) and Fig. 2 (magnification: 5000 times) images of the cross section of the produced hollow fiber membrane are shown.

Comparative Example  One

A separation membrane was prepared in the same manner as in Example 1, except that acetylated methyl cellulose (AMC) was not included and the composition for forming a separation membrane was applied in the contents shown in Table 1 below. An electron microscope image of the cross section of the hollow fiber membrane was shown in FIG. 3 (magnification: 50 times) and FIG. 4 (magnification: 5000 times).

Property evaluation method

(1) Water permeability (LMH): The hollow fiber membrane was placed in a 10 cm-thick acrylic tube, and potting was carried out using epoxy. The permeation rate was measured according to the membrane area by measuring the pure permeation flow rate per hour. In the measurement of the pure water permeability, a pressure of 1 bar was applied and measured by a dead-end filtration method.

(2) Tensile strength (kgf / fiber): One of the hollow fiber membranes was immersed in an influent using an Instron, and the tensile strength was measured while pulling the hollow fiber membrane at a rate of 50 mm / min.

Example 1 Comparative Example 1 PVDF 30 30 Poly plasticizer 54 55 NMP 10 10 AMC One 0 PVP 5 5 Water Transmission (LMH) 2700 1900 Tensile strength (kgf / fiber) 1. 7 1.15

As shown in Table 1, Example 1 containing acetylated methylcellulose (AMC) in the content of the present invention had excellent water permeability and tensile strength, while Comparative Example 1 containing no acetylated methyl cellulose (AMC) 1 shows low water permeability and tensile strength because of low hydrophilicity of the membrane.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the embodiments described above are in all respects illustrative and not restrictive.

Claims (13)

A separation membrane comprising 20% by weight or more and less than 40% by weight of a vinylidene fluoride resin, 5 to 20% by weight of a suitable solvent, 29 to 73.9% by weight of a plasticizer, 0.1 to 1% by weight of acetylated methylcellulose, and 1 to 10% by weight of a hydrophilic additive / RTI >
The method of claim 1, wherein the two solvents are selected from the group consisting of N-mentyl-2-pyrrolidone, dimethylformamide, N, N'-dimethyl acetamide, dimethylsulfoxide, and hexamethylphosphoric triamide. The composition for forming a separation membrane according to claim 1, wherein the composition comprises at least one of acetamide, dimethylsulfoxide, and hexamethylphosphoric triamide.
The composition for forming a separation membrane according to claim 1, wherein the plasticizer comprises a polyester plasticizer.
The method of claim 1, wherein the hydrophilic additive is selected from the group consisting of polyvinylpyrrolidone (PVP), ethylene glycol, polyethylene glycol (PEG), hydrophilic polymer having at least one (meth) acrylate group introduced therein, glycerol, polyacrylonitrile , Polyethylene oxide (PEO), and polyvinyl acetate (PVAc).
Stirring the composition for forming a separator of any one of claims 1 to 4;
Forming a separation membrane in the form of a hollow fiber by discharging the composition for forming a separation membrane through a spinning channel;
Solidifying the hollow-fiber type separation membrane;
≪ / RTI >
6. The method of claim 5, wherein the stirring is performed at 160 to 220 deg.
The separation membrane manufacturing method according to claim 5, wherein the solidification is performed by introducing the hollow-fiber separation membrane into a coagulation bath containing at least one of a good solvent and a non-solvent.
The separation membrane producing method according to claim 5, further comprising the step of solidifying and then stretching.
A separator produced by the method of claim 5 and having a water permeability of at least 1000 LMH and a tensile strength of at least 1.2 kgf / fiber.
10. The separation membrane according to claim 9, wherein the separation membrane has a hollow cylindrical shape.
The separation membrane according to claim 9, wherein the separation membrane has a mesh-type crystal structure.
The separation membrane according to claim 9, wherein the separation membrane has an average pore size of 0.05 탆 to 0.3 탆.
A water treatment apparatus comprising the separation membrane of claim 9.

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