KR20120076907A - Tubular braid and composite hollow fiber membrane using the same - Google Patents

Abstract

The present invention relates to a tubular knitted fabric and a composite hollow fiber membrane using the same, and more particularly, to knit a tubular knitted fabric with a multifilament composed of 0.41 to 0.49 denier twisted or non-twisted monofilament, to prepare a composite hollow fiber membrane using the same As a result, the specific surface area of the composite hollow fiber membrane can be expanded and the peeling strength can be improved.

Description

Tubular knitted fabric and composite hollow fiber membrane using the same {Tubular braid and Composite Hollow Fiber Membrane using the same}

The present invention relates to a tubular knitted fabric and a composite hollow fiber membrane using the same.

In general, it is well known that water treatment using a separation membrane is a purification technique using a selective permeation mechanism of a material. At this time, the water treatment using the membrane, that is, the technology of separating contaminated water is economical in terms of energy saving, facility simplification, and operation efficiency compared to the distillation method used in the conventional chemical treatment, and also meets the social needs such as environmental protection. From the simple laboratory scale to the scale of various industrial fields, a wide range of research and practical use has been conducted.

The separation membranes are morphologically flat, tubular, hollow fiber, etc. The flat membranes have high pollution resistance and are widely applied as wastewater treatment technology, but have a high density per unit volume. Low economical installation is difficult. Hollow fiber membrane is morphologically shaped and has a merit that can increase the throughput by packing a lot of membranes per unit volume. Therefore, since the hollow fiber membrane has a large membrane surface area and easy to modularize compared to other membranes of the same volume, the application of the hollow fiber membranes has been actively conducted in recent years.

However, hollow fiber membranes are often easily cut off during operation due to low mechanical strength, and in particular, these disadvantages act as a deterrent to securing high quality water. According to the demand for the improvement of the mechanical strength for such hollow fiber membranes, a composite hollow fiber membrane for producing a hollow fiber membrane using a knitted or tubular knitted fabric having excellent mechanical strength has been proposed.

When the composite hollow fiber membrane is manufactured with non-twisted non-twisted yarn having a small surface area, the contact surface between the membrane and the tubular knitted fabric is small, and thus the adhesive strength is weak, and thus, the membrane may fall from the tubular knitted fabric during the process.

On the other hand, when the microfiber of 0.4 denier or less is used, microfiber single yarns are generated in the process of producing a tubular knitted fabric, and the single yarns are agglomerated to reduce workability. In addition, since a single yarn is formed on the surface of the tubular knitted fabric, the single yarn is protruded on the coating surface during polymer coating, thereby increasing the defect of the hollow fiber membrane.

One object of the present invention is to provide a tubular knitted fabric which is excellent in mechanical strength, in particular peel strength, and which is free of monofilaments monolithic on the surface of the tubular knitted fabric, which enables uniform quality maintenance of the hollow fiber membrane.

It is another object of the present invention to provide a composite hollow fiber membrane having improved mechanical strength by using the tubular knitted fabric.

One aspect of the present invention for solving the above problem relates to a tubular knitted fabric knitted with multifilament consisting of 0.41 to 0.49 denier or non-twisted monofilament.

Another aspect of the present invention for solving the above problems is a composite hollow fiber membrane made of a tubular knitted fabric knitted with multifilament consisting of 0.41 to 0.49 denier or non-twisted monofilament and a polymer resin thin film coated on the surface of the tubular knitted fabric It is about.

According to embodiments of the present invention, by using 0.41 to 0.49 denier monofilament, the contact surface between the polymer solution and the tubular knitted fabric can be increased to improve the peel strength between the tubular knitted fabric and the polymer resin thin film. In addition, the filament does not protrude out of the coating layer because there is less single yarn generated during the operation of the tubular knitted fabric, it is possible to maintain a uniform quality of the hollow fiber membrane, and it is economical because it does not need an additional process for removing the monofilament single yarn on the surface of the tubular knitted fabric.

1 is a cross-sectional view of a composite hollow fiber membrane according to an embodiment of the present invention.
<Explanation of symbols for the main parts of the drawings>
1: tubular knitted fabric 2: polymer resin thin film
3: hollow part

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

One embodiment of the present invention relates to a tubular knit knitted from multifilament consisting of 0.41 to 0.49 denier or non-twisted monofilament.

1 is a cross-sectional view of a composite hollow fiber membrane according to an embodiment of the present invention.

Referring to Figure 1, the composite hollow fiber membrane according to an embodiment of the present invention is a tubular braid (tubular braid) (1), a polymeric resin thin film (2) coated on the surface of the tubular knitted fabric 1 and the treated material It consists of a hollow portion (3) for receiving. The tubular knitted fabric 1 is a multifilament made of 0.41 to 0.49 denier or non-twisted monofilament, and contributes to the improvement of the properties of the composite hollow fiber membrane.

The tubular knitted fabric according to the embodiment of the present invention is composed of multifilaments composed of 0.41 to 0.49 denier twisted or non-twisted monofilaments, so that the contact area between the polymer solution and the tubular knitted fabric is expanded, and the dope solution is converted into the tubular knitted fabric. Since it can penetrate, the adhesive force with the polymer resin thin film can be improved. Therefore, it is possible to improve the peel strength which is pointed out as a disadvantage of the conventional reinforcing hollow fiber membranes. Can be used to ensure excellent processing stability.

The tubular knitted fabric 1 is preferably composed of multifilaments composed of false or non-twisted monofilaments with a fineness of 0.41 to 0.49 denier. If the fineness of the monofilament exceeds 0.49 denier, the peeling strength between the tubular knitted fabric 1 and the polymer resin thin film (2) coated on the surface is lowered, and if the fineness of the monofilament is less than 0.41 denier, the peeling strength increases. However, the water permeability decreases and can lead to polymer coating failure due to monofilament of monofilament.

300 to 1000 denier yarns are manufactured by plying 2 to 10 multifilaments of 20 to 200 deniers consisting of 40 to 500 monofilaments. When the fineness of the multifilament is less than 20 denier, the production rate is lowered, and when the fineness of the multifilament exceeds 200 denier, the degree of integration per unit volume may be reduced as the outer diameter of the tubular knitted fabric 1 is expanded.

10 to 40 yarns thus prepared are woven to produce the tubular knitted fabric 1.

The material of the tubular knitted fabric 1 according to the embodiment of the present invention may be polyethylene terephthalate (PET), nylon (Nylon), or the like including a polar group, but is not limited thereto. Polyethylene, polypropylene, etc., which are composed of non-polar molecular chains, have poor adhesion with the polymer resin thin film layer, which is a coating layer, while polyester-based and polyamide-based materials including polar groups have excellent interfacial adhesion with the coating layer.

One embodiment of the present invention relates to a composite hollow fiber membrane made of a tubular knitted fabric made of multifilament made of false twisted or non-twisted monofilament of 0.41 to 0.49 denier and a polymer resin thin film coated on the surface of the tubular knitted fabric.

According to one embodiment of the invention, the polymer resin thin film (2) is coated on the surface of the tubular knitted fabric (1) to form a composite hollow fiber membrane, the polymer resin thin film (2) is the mechanical strength of the composite hollow fiber membrane, the number of membranes Affects permeability and filtration reliability. The polymer resin thin film (2) has a lower mechanical strength than the tubular knitted fabric (1), but has a mechanical strength such that the polymer resin thin film (2) itself does not peel or break, and the tensile strength and pressure resistance of the composite hollow fiber membrane To complement.

With regard to water permeability and filtration reliability, the tubular knitted fabric 1 has a relatively large void compared to the polymeric resin thin film 2, so that the filtrate passing through the polymeric resin thin film 2 has a large void. Pass (1) without great resistance. That is, the water permeability of the filtrate is affected by the polymer resin thin film 2 having small pores, and the water permeability of the entire composite hollow fiber membrane is determined by the micropore structure and porosity of the polymer resin thin film 2.

The micropore structure and porosity of the polymer resin thin film 2 is determined according to the difference in thermodynamic stability according to the composition of the dope. In more detail, when the solvent or additives constituting the dope solution strongly interact with the polymer, a sponge-like structure is formed due to the 'demixing delay effect' between the polymer and the coagulation bath solution. As the interaction with the polymer becomes weaker, the 'demixing effect' proceeds rapidly to form a finger-like structure. The sponge structure is advantageous over the finger structure in terms of mechanical strength, but disadvantageous in terms of water permeability. The reason is that the sponge structure has a strong hydraulic resistance compared to the finger structure. On the other hand, the surface pore size distributed on the surface shows an important function for imparting reliability of the filtration characteristics. That is, the formation of the surface pore having the same distribution excludes particles of a certain size or more to impart stability of the water quality in the water treatment process.

According to one embodiment of the present invention, the polymer resin thin film 2 forms a sponge structure from 50 to 190 μm in the lower layer to simultaneously express mechanical strength, water permeability, and filtration reliability, and a finger structure up to 0.1 to 10 μm in the upper layer. Forming can minimize the dispersion of the surface pore size. Micropores having a pore size of 0.01 to 1 μm may be formed in the surface layer, and micropores having a pore size of 0.01 to 10 μm may be formed in an inner layer. In addition, when the diameter of the micropores formed in the inner layer of the composite hollow fiber membrane gradually increases toward the center direction to increase asymmetry, the water permeability can be enhanced.

Next, the polymer resin thin film 2 is applied to the tubular knitted fabric 1 and undergoes a solidification process. As the organic solvent is released during the solidification process, a pore is formed therein. At this time, since the surface layer of the polymer resin thin film 2 has a faster solidification rate than the inner layer, the pore size of the surface layer is formed relatively smaller than the pore size of the inner layer.

In one embodiment of the present invention, the thickness of the polymer resin thin film (2) may be in the range of 10 to 200㎛, when the thickness of the polymer resin thin film (2) is less than 10㎛ when the mechanical strength falls, if larger than 200㎛ Permeability may drop. The distance that the polymer resin thin film 2 penetrates into the tubular knitted fabric 1 may range from 10 to 30% of the thickness of the tubular knitted fabric 1 (ie, the difference between the outer diameter and the inner diameter of the tubular knitted fabric 1). If the distance is less than 10% of the thickness of the tubular knitted fabric 1, the mechanical strength is lowered, and if it is more than 30%, the water permeability may be lowered.

The polymer resin thin film 2 according to an embodiment of the present invention is formed by coating a surface of the tubular knitted fabric 1 with a spinning dope composed of a polymer resin, an organic solvent, and an additive polyvinylpyrrolidone and a hydrophilic compound. .

In the process of manufacturing a composite hollow fiber membrane according to an embodiment of the present invention, the tubular knitted fabric (1) passes through the tubular knitted fabric (1) to the center of the double tubular nozzle and flows the spinning dope into the surface of the tubular knitted fabric (1). Coating the spin dope on the surface of the substrate). Subsequently, the spinning dope may be discharged into the air outside the nozzle, coagulated with an external coagulation liquid, and then washed with water and dried.

Spinning dope which can be used in embodiments of the present invention is prepared by dissolving a polymer resin, an additive polyvinylpyrrolidone and a hydrophilic compound in an organic solvent. Preferred content ranges include, but are not limited to, 10 to 50% by weight of polymer resin, 1 to 30% by weight of polyvinylpyrrolidone and hydrophilic compound, and 20 to 89% by weight of organic solvent.

The polymer resin may be polysulfone resin, polyethersulfone resin, sulfonated polysulfone resin, polyvinylidene fluoride (PVDF) resin, polyacrylonitrile (PAN) resin, polyimide resin, polyamideimide resin, and poly One or more selected from the group consisting of esterimide resins can be used.

The organic solvent may be at least one selected from the group consisting of dimethylacetamide, dimethylformamide and dimethylacrylamide, but is not limited thereto. In addition, as the surface pore-forming agent, one or more selected from the group consisting of water or a polypyrrolidone-based compound may be used. When the polypyrrolidone compound is less than 1%, no uniform surface pore is formed, and the polypyrrolidone compound is 30 If it is more than%, the mechanical strength decreases due to the brittleness of the thin film.

Hereinafter, the present invention will be described in more detail with reference to the following examples in order to help understand the present invention, but various modifications may be made to the embodiments according to the present invention, and the scope of the present invention is limited to the following examples. It should not be interpreted.

Example  One

Ten strands of 43 denier multifilaments consisting of 96 filaments of polyethylene terephthalate twisted yarn monofilament with 0.45 denier were made to have a total fineness of 430 denier per yarn. Thereafter, a tubular knitted fabric woven to have an outer diameter of 1.7 mm was prepared using the prepared 24 strands of yarn.

As the dope solution, 10% by weight of polyvinylidene fluoride (PVDF) as a polymer resin and 10% by weight of polyvinylpyrrolidone (PVP) as an additive are sufficiently dissolved in a dimethylacetamide solvent at 50 ° C, followed by degasing. The gas generated during the manufacturing process was removed and placed at room temperature. The dope solution was coated on the outside of the tubular knitted fabric by supplying the prepared dope solution to the double tubular nozzle and passing the woven tubular knitted fabric through the center portion. At this time, the thickness of the coating layer was 0.2mm. The knitted fabric which passed the air gap 5 cm was solidified in an external coagulation bath at 30 ° C. Thereafter, a post-treatment was performed in a hydrothermal apparatus at 60 ° C. for one day to remove residual solvents and additives. The composite hollow fiber membrane was prepared by immersion in a 20 wt% alcohol aqueous solution for 2 hours and then dried in a dryer at 40 ° C. for one day. .

Example  2

Ten strands of 43 denier multifilament consisting of 96 filaments of polyethylene terephthalate non-twisted monofilament with a fineness of 0.45 denier were spun together to give a total fineness of 430 denier per yarn. Thereafter, a tubular knitted fabric woven to have an outer diameter of 1.7 mm was prepared using the prepared 24 strands of yarn.

Using the tubular knitted fabric, a composite hollow fiber membrane was obtained by the same processes and conditions as in Example 1.

Comparative example  One

Two 240 denier non-twisted multifilament strands composed of 96 strands of polyethylene terephthalate monofilament having 2.5 deniers of fineness were spliced to give a total fineness of 480 deniers per yarn. Thereafter, a tubular knitted fabric woven so as to have an outer diameter of 1.9 mm was prepared using 24 prepared yarns. Using the tubular knitted fabric, a composite hollow fiber membrane was obtained by the same processes and conditions as in Example 1.

Comparative example  2

The 7 fine strands of 60 denia twisted yarn multifilament made of 200 strands of polyethylene terephthalate monofilament having a fineness of 0.3 denier were combined so that the total fineness of one yarn was 420 denier. Thereafter, a tubular knitted fabric woven so as to have an outer diameter of 1.7 mm was prepared using 24 prepared yarns. Using the tubular knitted fabric, a composite hollow fiber membrane was obtained by the same processes and conditions as in Example 1.

<Method for Evaluating Physical Properties of Composite Hollow Fiber Membrane>

The physical properties of the composite hollow fiber membranes prepared in Examples and Comparative Examples were measured by the following method and are shown in Table 3 below.

Experimental Example  One : Peel strength

The load at the moment of peeling of the polymer resin thin film from the tubular knitted fabric was measured using a tensile tester, and the peel strength was calculated by dividing this by the area (㎡) to which the shear force was applied. Specific measurement conditions are shown in Table 1 below.

Measuring device manufacturer Instron Load cell 1KN Cross head speed 25 mm / min Gripping distance 50 mm Specimen Manufacturing Manufactured by bonding and fixing one strand of composite hollow fiber membrane to 6mm diameter polypropylene tube with polyurethane resin so that the length of adhesive part is 10mm

Peel strength is defined as the shear strength per unit area applied to the coated polymer resin thin film when the specimen is tensioned, and the area (m ² ) to which shear force is applied is π × outer diameter of the composite hollow fiber membrane (m) × Calculated by the adhesion length (m). The calculation is as follows.

* Peel strength (Pa) = Load at yield point (kg) / Area under shearing force (m ² )

Experimental Example  2 : Dope permeability

The cross section of the manufactured composite hollow fiber membrane was cut and the degree of penetration of the dope solution into the tubular knitted fabric was observed through a microscope.

Experimental Example  3: Permeability

A compact pressure module with a membrane area of 0.0057 m ² was fabricated and placed in a device with a pressure gauge. The interlayer differential pressure was kept constant at 100 kPa and RO water at 24 ± 1 ° C. was supplied to measure the water permeation rate for 2 minutes. The unit of permeation amount is LMH (L / m ² × h).

Experimental Example  4: Coating Defect  Confirm

After sufficiently wetting the small pressure module with a membrane area of 0.0057 m ² , 0.1 pm of air was injected backward to observe whether or not the pneumatic pressure was maintained for 1 min.

Monofilament denier Twist type Peel strength
(Mpa) Dope
permeability(%) Permeability (LMH) Defect
The presence or absence Example 1 0.45 Yeonsasa Temple 10.7 20 1,150 radish Example 2 0.45 Non-burning yarn 10.1 20 1,160 radish Comparative Example 1 2.50 Non-burning yarn 5.8 40 1,200 radish Comparative Example 2 0.30 Yeonsasa Temple 10.9 10 600 U

As can be seen in Table 2, in the case of Comparative Example 1 in which the denier of the monofilament was 2.5 denier, the peel strength was decreased due to the decrease in the adhesion surface with the polymer coating layer, and in Comparative Example 2 in which the monofilament denier was 0.3 denier, the permeability Defects due to degradation and monofilament single yarn were observed. On the other hand, in Examples 1 and 2, the peeling strength was effectively improved without decreasing the permeability, and no defect occurred due to the monofilament single yarn. Thus, 0.41 to 0.49 denier or non-twisted monofilament was used according to the present invention. It can be confirmed that the hollow fiber membrane with high permeability and peel strength can be stably produced.

Although the present invention has been described in detail with reference to preferred embodiments of the present invention, these are merely exemplary, and those skilled in the art to which the present invention pertains have various modifications and equivalents therefrom. It will be appreciated that embodiments are possible. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (15)

A tubular knitted fabric knitted from multifilament consisting of 0.41 to 0.49 denier twisted yarn monofilament.
A tubular knitted fabric knitted from multifilament consisting of 0.41 to 0.49 denier non-twisted monofilament.
The tubular knitted fabric of claim 1 or 2, wherein the multifilament is formed by combining 40 to 500 monofilaments, and has a fineness of 20 to 200 denier.
The tubular knitted fabric of claim 1 or 2, wherein the tubular knitted fabric is manufactured by knitting 10 to 40 yarns, and each of the yarns is manufactured by weaving 2 to 10 multifilaments. .

5. The tubular knitted fabric of claim 4, wherein the fineness of each of the yarns is between 300 and 1000 denier.
The tubular knitted fabric of claim 1 or 2, wherein the tubular knitted fabric is made of one or more selected from the group consisting of polyethylene terephthalate and nylon.
A composite hollow fiber membrane comprising a tubular knitted fabric made of multifilament composed of 0.41 to 0.49 denier twisted yarn monofilament and a polymer resin thin film layer coated on the surface of the tubular knitted fabric.
A composite hollow fiber membrane comprising a tubular knitted fabric made of multifilament composed of 0.41 to 0.49 denier non-twisted monofilament and a polymer resin thin film layer coated on the surface of the tubular knitted fabric.

The composite hollow fiber membrane according to claim 7 or 8, wherein the multifilament is made by combining 40 to 500 monofilaments, and the fineness is 20 to 200 denier.
The composite hollow according to claim 7 or 8, wherein the tubular knitted fabric is manufactured by knitting 10 to 40 yarns, and each of the yarns is manufactured by weaving 2 to 10 multifilaments. desert.
The composite hollow fiber membrane according to claim 10, wherein the fineness of each of the yarns is 300 to 1000 denier.
The method of claim 7 or 8, wherein the polymer resin thin film forms a sponge-like structure up to 50 to 190㎛ in the lower layer and a finger-like structure up to 0.1 to 10㎛ in the upper layer Composite hollow fiber membrane, characterized in that.
9. The composite hollow according to claim 7 or 8, wherein the polymer resin thin film comprises a surface layer having a pore size of 0.01 to 1 μm and an inner layer having a pore size of 0.01 to 10 μm. desert.
The composite hollow fiber membrane according to claim 7 or 8, wherein the polymer resin thin film has a thickness of 10 to 200 µm.
The composite hollow fiber membrane according to claim 7 or 8, wherein the polymer resin thin film penetrates into the tubular knitted fabric in a range of 10 to 30% of the thickness of the tubular knitted fabric.

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