KR20120004015A - Tubular braid and composite hollow fiber membrane using the same - Google Patents

Abstract

PURPOSE: Tubular knit and composite hollow fiber membrane using the same are provided to maintain the uniform quality of the hollow fiber membrane and to improve the splitting resistance of the tubular knit and a polymer resin thin film. CONSTITUTION: Tubular knit(1) is knitted based on shaped yarn mono-filament. The shaped yarn mono-filament is composed of polyethylene terephthalate and polytrimethylene terephthalate of 0.01-7 deniers. The maximum thermal temperature of the mom-filament is more than or equal to 155 degrees Celsius. The elastic recovery rate of the mono-filament is more than or equal to 70%. The cross-section of the mono-filament is in a side-by-side shape or a sheath-core shape. 10 to 300 mono-filaments are braided to obtain yarn.

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.

If the use of microfibers of 0.4 denier or less is used in the production of composite hollow fiber membranes, 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 having excellent elongation and recovery rate of monofilament, no monofilament single-threaded on the surface of the tubular knitted fabric, and hardly deformed to maintain uniform quality 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 problems is a tubular knitted with a heterospun cross-section monofilament composed of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) of 0.01 to 7 denier Relates to knitted fabrics.

Another aspect of the present invention for achieving the above object is a tubular knitted fabric knitted from a hetero-section monofilament composed of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) of 0.01 to 7 denier And it relates to a composite hollow fiber membrane made of a polymer resin thin film coated on the surface of the tubular knitted fabric.

According to embodiments of the present invention, a polymer solution and a tubular knitted fabric are made by using a single-sided monofilament composed of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) of 0.01 to 7 deniers. The contact surface between them 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.
2- (a), (b), (c), and (d) are cross-sectional views of a release cross-section monofilament according to one 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 knitted fabric knitted from a heterosized single-sided monofilament composed of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) of 0.01 to 7 denier.

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 made of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) of 0.01 to 7 deniers to contribute to improving the properties of the composite hollow fiber membrane Done.

The monofilament is a fiber obtained by using two kinds of melt-spun fiber-forming polymers. The maximum heat shrinkage stress temperature is 155 ° C or higher, the crimp elongation is 40% or more, and the elastic recovery rate is 70% or more under unloaded non-water treatment. It is an elastic composite fiber with excellent shape stability because it is possible to manufacture processed fabrics with iron shrinkage of 3% or less.

In addition, the shape of the cross section of the monofilament is preferably a side-by-side type or an eccentric sheath-core type. 2- (a), (b), (c), and (d) are cross-sectional views of a release cross-section monofilament according to one embodiment of the present invention. 2- (a) and 2- (b) show side-by-side cross-sections of the shaped cross-section monofilament, and FIG. 2- (d) shows the shaped cross-section monofilament Shows an eccentric sheath-core type cross section.

10 to 300 of such monofilaments are plyed together to produce yarns of 0.1 to 500 deniers. When the fineness of the yarn is less than 0.1 denier, the production rate is lowered, and when the fineness of the yarn exceeds 500 denier, the degree of integration per unit volume may decrease as the outer diameter of the tubular knitted fabric 1 is expanded.

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

One embodiment of the present invention is a tubular knitted fabric and a tubular knitted knitted with a hetero-section monofilament composed of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) of 0.01 to 7 denier It relates to a composite hollow fiber membrane consisting of a polymer resin thin film coated on the surface.

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, wherein 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 interact strongly 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. 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. If the distance is greater than 30%, the water permeability decreases, and the film thickness becomes thin, resulting in defects on the surface, thereby degrading the removal performance of the film. do.

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

Yarn of 6-denier multifilament of 50 deniers consisting of 36 filaments of heterospun monofilament consisting of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) with 1.4 degrees of fineness One total fineness was 300 deniers. Then, using the 26 yarns prepared to prepare a tubular knitted fabric woven so that the outer diameter is 1.9 mm.

As a dope solution, a composition composed of 16% PVDF, 12% polyvinylpyrrolidone, and 72% dimethyl acrylamide was sufficiently dissolved at 50 ° C., and then degased to remove gas generated during the manufacturing process and placed at room temperature. I was. 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

Yarn is made of 6 strands of 50 filament multifilament composed of 100 filaments of heterospun monofilament composed of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) with 0.5 degree of fineness. One total fineness was 300 deniers. Thereafter, using the prepared 26 strands of yarn to prepare a tubular knitted fabric woven so that the outer diameter is 1.9mm. The subsequent process obtained the composite hollow fiber membrane by the process and conditions similar to Example 1.

Comparative example  One

Six 50 strands of stretched multifilament of 50 denier yarns consisting of 36 strands of PET monofilament having a fineness of 1.4 denier were spliced to obtain a total fineness of 300 denier per yarn. Then, using the 26 yarns prepared to prepare a tubular knitted fabric woven so that the outer diameter is 1.9 mm. The subsequent process obtained the composite hollow fiber membrane by the process and conditions similar to Example 1.

Comparative example  2

A total of 6 yarns of 50 non-stretched non-stretched multifilament composed of 100 PET monofilament having 0.5 degree of fineness was made to have a total fineness of 300 yarn of one yarn. Then, using the 26 yarns prepared to prepare a tubular knitted fabric woven so that the outer diameter is 1.9 mm. The subsequent process obtained the composite hollow fiber membrane by the process and conditions similar to Example 1.

<Evaluation Criteria and Measurement Method of Composite Fiber Properties>

One. Heat shrinkage stress  Measure

The initial load of 0.5g / d, the temperature increase rate of 2.2 ℃ / second was measured using a thermal stress tester of Kanebo.

2. Crimp extension rate  And Elastic recovery  Measure

The fiber skein was immersed in boiling water for 30 minutes under no load, and then dried at room temperature, subjected to 0.1 g / d load for 2 minutes, and left for 10 minutes. After the sample subjected to the steps allowed to stand for two minutes under 0.002 g / d load was measured in length (L ₁₎ at that time. 0.1 g / d load was added to the sample and the length (L ₂ ) was measured after 2 minutes. Furthermore, after removing the 0.1 g / d load, the length (L ₃ ) at that time after 2 minutes was measured. Crimping rate or elastic recovery rate was calculated by the following formula (1) or (2).

[Equation 1]

Crimping rate (%) = [(L ₂ -L ₁ ) / L ₂ ] × 100

[Equation 2]

Elastic recovery rate (%) = [(L ₂ -L ₃ ) / (L ₂ -L ₁ )] × 100

3. Iron ( Iron ) Shrinkage  Measure

It was knitted and salted by a conventional method and measured according to KS K 0558-2001 and A-1 (dry heat iron method).

<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 1 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 3 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-stiffness ( Stiffness )

Using the sample holder provided by Instron, the composite hollow fiber membrane was pressed in the compression mode to evaluate the stiffness with the maximum load generated when bending occurred. Specific measurement conditions are shown in Table 2 below.

Measuring device manufacturer Instron Load cell 10KN 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

Experimental Example  4 - 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).

Denier of monofilament Peel Strength (Mpa) Penetration of dope Stiffness (kg) Permeability (LMH) Example 1 1.4 1.11 X 0.131 531 Example 2 0.5 1.21 X 0.109 523 Comparative Example 1 1.4 1.09 X 0.128 521 Comparative Example 2 0.5 0.92 X 0.065 485

As can be seen in Table 3, in the composite hollow fiber membrane according to the present invention, a single-sided yarn monolayer composed of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) of 0.01 to 7 denier It can be seen that the filament can be used to increase the peel strength by expanding the specific surface area.

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. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (10)

A tubular knitted fabric knitted from heterosized single-sided monofilaments composed of polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT) of 0.01 to 7 denier.
The monofilament of claim 1, wherein the monofilament has a maximum heat shrinkage stress of at least 155 ° C., a crimp elongation rate of at least 40%, an elastic recovery rate of at least 70%, and an iron shrinkage rate of at most 3% under no-load water treatment. Tubular knitted fabric, characterized in that the production of.
The tubular knitted fabric of claim 1, wherein the monofilament has a side-by-side type or a heath-core type.
The tubular knitted fabric of claim 1, wherein the tubular knit fabric is made by knitting between 8 and 40 yarns, each of which is fabricated by blending 10 to 300 monofilaments.
5. The tubular knitted fabric of claim 4, wherein the fineness of each of the yarns is between 0.1 and 500 denier.
A tubular knitted fabric composed of a mono-filament monolayer filament composed of 0.01 to 7 denier polyethylene terephthalate (PET) and polytrimethylene terephthalate (PTT), and a polymer resin thin film layer coated on the surface of the tubular knitted fabric Composite hollow fiber membrane. The monofilament of claim 6, wherein the monofilament has a maximum heat shrinkage stress of at least 155 ° C., a crimp elongation rate of at least 40%, an elastic recovery rate of at least 70%, and an iron shrinkage rate of at most 3% under unloaded non-water treatment. Composite hollow fiber membrane, characterized in that the production of.
7. The composite hollow fiber membrane according to claim 6, wherein the monofilament has a side-by-side type or a heat-core type.
The composite hollow fiber membrane of claim 6, wherein the tubular knitted fabric is manufactured by knitting 8 to 40 yarns, and each of the yarns is manufactured by plying 10 to 300 monofilaments.
The composite hollow fiber membrane of claim 6, wherein the fineness of each of the yarns is 0.1 to 500 denier.

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