KR100595492B1 - Method of manufacturing for nanofiber assembly with excellent mechanical property - Google Patents

Abstract

The present invention relates to a method for producing a nanofiber aggregate having excellent mechanical properties, the collector of which high voltage is applied through a spinning nozzle (5) having a high voltage applied to a spinning solution in which a water-soluble polymer resin whose terminal group is -OH group is dissolved in distilled water ( 7) In preparing a nanofiber aggregate by electrospinning on the phase, it is characterized in that the acid solution is added and mixed.

The present invention can greatly improve the mechanical properties of the nanofibers by increasing the degree of crystallinity by aligning the molecular chains constituting the electrospun nanofibers well in the fiber axis direction.

Nanofibers, aggregates, mechanical properties, electrospinning, nonwovens, water soluble polymers, acid solutions, filaments.

Description

Method for manufacturing nanofiber aggregates with excellent mechanical properties {Method of manufacturing for nanofiber assembly with excellent mechanical property}             

1 is a process schematic diagram of the present invention for producing a nanofiber aggregate in a bottom-up electrospinning method.

FIG. 2 is an enlarged illustration of the collector 7 used in the process of FIG. 1 when manufacturing nanofiber filaments. FIG.

Figure 3 is a graph showing the electrical conductivity change state of the spinning solution according to the spinning solution composition.

Figure 4 is a graph showing the state of the viscosity and surface tension change of the spinning solution according to the spinning solution composition.

Figure 5 is a scanning electron micrograph showing the surface state of the polyvinyl alcohol nanofiber nonwoven fabric prepared in Comparative Example 1.

6 is a scanning electron micrograph showing the surface state of the polyvinyl alcohol nanofiber nonwoven fabric prepared in Example 1. FIG.

7 is a scanning electron micrograph showing the surface state of the polyvinyl alcohol nanofiber nonwoven fabric prepared in Example 2. FIG.

8 is a scanning electron micrograph showing the surface state of the polyvinyl alcohol nanofiber nonwoven fabric prepared in Example 3. FIG.

9 is a scanning electron micrograph showing the surface state of the polyvinyl alcohol nanofiber nonwoven fabric prepared in Example 4. FIG.

10 is a graph showing the correlation between strain and stress of the nanofiber nonwoven fabric prepared in Examples 1 to 4 and Comparative Example 1.

* Explanation of symbols on the main parts of the drawings

1: Spinning solution main tank 2: Metering pump 3: Spinning solution drop device

4: Spinning nozzle block 5: Spinning nozzle 6: Nanofiber

7 collector (conveyor belt) 7a: groove formed in the collector

8a, 8b: collector support roller 9: voltage generator

10: Radiating nozzle block left and right reciprocating device

11a: motor for agitator 11c 11b: non-conductive breaking device

11c: Stirrer 12: Spinner Discharge Device

13 transfer pipe 14 nonwoven fabric support roller

15: nonwoven fabric 16: nonwoven fabric winding roller

a: nanofiber nonwoven fabric prepared in Comparative Example 1

a ₁ : spinning solution of Comparative Example 1

b: nanofiber nonwoven fabric prepared in Example 1 b ₁ : spinning solution of Example 1

c: nanofiber nonwoven fabric prepared in Example 2 c ₁ : spinning solution of Example 2

d: nanofiber nonwoven fabric prepared in Example 3 d ₁ : spinning solution of Example 3

e: nanofiber nonwoven fabric prepared in Example 4 e ₁ : spinning solution of Example 4

The present invention relates to a method for producing a nanofiber aggregate having excellent mechanical properties, and more particularly, an acid solution is added to a spinning solution when the nanofiber aggregate is prepared by electrospinning a spinning solution in which a water-soluble polymer resin is dissolved in distilled water. It relates to a method of producing a nanofiber aggregate having excellent mechanical properties by mixing.

In the present invention, the nanofiber means a fiber having a fiber diameter of 1,000 nm or less.

Aggregates composed of nanofibers, more specifically nonwoven fabrics, membranes, braids, etc. composed of nanofibers are widely used in household goods, agriculture, clothing, industrial, and the like. Specifically, it is used in various fields such as artificial leather, artificial suede, sanitary napkins, garments, diapers, packaging materials, miscellaneous materials, various filter materials, medical materials for gene carriers, defense materials such as bulletproof vests.

As shown in FIG. 1, the spinning apparatus for manufacturing the nanofiber aggregate includes a spinning liquid main tank 1 for storing spinning liquid, a metering pump 2 for quantitative supply of spinning liquid, and a plurality of nozzles for ejecting spinning liquid. (5) is composed of a spinneret block (4) arranged, a collector (7) for generating the fibers and a voltage generator (9) for generating a voltage located at the bottom or top of the nozzle.

Looking at the manufacturing method of the nanofiber aggregate using the electrospinning device in detail, the spinning solution in the spinning solution main tank 1 is continuously metered into a plurality of nozzles 5 to which a high voltage is applied through a metering pump.

Subsequently, the spinning liquid supplied to the nozzles is spun and concentrated through the nozzle onto the collector 7 under high voltage to form a nanofiber web.

Subsequently, the nanofiber web is calendered or needle punched to produce a nonwoven fabric composed of nanofibers.

On the other hand, looking at an example of a method for producing a continuous phase filament consisting of nanofibers when using the electrospinning of Figure 1 method of using a collector 7 formed grooves at regular intervals as shown in Figure 2 when electrospun There is this.

When the collector 7 of FIG. 2 is not used, the continuous filaments made of nanofibers are formed by cutting the electrospun nanofiber webs at a predetermined interval (small width) and then twisting the cut narrow nanofiber webs. It can also manufacture.

In the case of preparing the nanofiber aggregate, more specifically, the nanofiber nonwoven fabric or the nanofiber filament by electrospinning the spinning solution in which the water-soluble polymer resin is dissolved in distilled water by the conventional methods described above, it is applied because the prepared nanofiber aggregate is water-soluble. There were many limitations on the use and very weak mechanical properties.

When manufacturing the nanofiber aggregate by the electrospinning method, the distance between the nozzle and the collector (radiation distance) is very short, so that a separate stretching process cannot be introduced therebetween, so that the mechanical properties of the manufactured nanofiber aggregate are greatly reduced. .

The present invention significantly improves the mechanical properties of the nanofiber aggregate prepared by electrospinning the spinning solution in which water-soluble polymer resin is dissolved in distilled water in order to solve the conventional problems, and at the same time the nanofiber aggregate is insoluble in water. It is intended to provide a manufacturing method to have.

Method for producing a nanofiber aggregate of the present invention for achieving the above problems, the collector is a voltage is applied through the nozzle (3) is applied to the spinning solution dissolving a water-soluble polymer resin having a terminal group of -OH group in distilled water ( When the nanofiber aggregates are prepared by electrospinning with 4), an acidic solution is added to the polymer spinning solution.

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

In the present invention, the nanofiber aggregate includes both a nonwoven fabric composed of nanofibers and a continuous filament composed of nanofibers.

First, looking at the method for producing a nanofiber nonwoven fabric according to the present invention, the spinning solution in which a high voltage is applied in an electrospinning apparatus such as FIG. An acid solution is added to the spinning solution and mixed when the nanofibers are prepared by electrospinning the collector 7 under high voltage.

The water-soluble polymer resin is a polyvinyl alcohol-based resin or the like, and is at least one resin selected from polymers, copolymers and mixtures thereof containing vinyl alcohol.

The acid solution is acetic acid, lactic acid, malic acid, citric acid, and the like.

The addition amount of the acidic solution is preferably 1 to 30% by weight, more preferably 1 to 10% by weight relative to the total weight of the spinning solution.

When the addition amount of the acidic solution is less than 1% by weight, the effect of improving mechanical strength is insignificant, and when it exceeds 30% by weight, the formation ability of the nanofibers is remarkably lowered, and thus, electrospinning may be very difficult.

On the other hand, as the electrospinning method, (i) a bottom-up electrospinning method in which the radiation nozzle block 4 is located below the collector 7, and (ii) the radiation nozzle block 4 is located above the collector 7. Any of the top-down electrospinning methods and (i) the horizontal electrospinning method in which the radial nozzle block 4 and the collector 7 are positioned at a horizontal or similar angle may be used, but a bottom-up electrospinning method is more preferable. Do.

The reason is that in the case of the bottom-up electrospinning method, the nozzles can be arranged indefinitely so that mass production is possible and the width or thickness of the nonwoven fabric can be freely adjusted.

Next, look at the method of manufacturing the nanofiber nonwoven fabric or filament of the present invention using the bottom-up electrospinning apparatus of FIG.

First, the water-soluble polymer resin spinning solution stored in the spinning solution main tank 1 is metered by a metering pump 2 and supplied to the spinning solution dropping device 3 by quantity.

In this case, as the polymer resin for preparing the spinning solution, a water-soluble polymer resin having a terminal group of -OH group, such as polyvinyl alcohol, is used.

In this way, the spinning solution supplied into the spinning solution drop device 3 is discontinuously passing through the spinning solution drop device 3, that is, the clouding of the spinning solution is blocked more than once, and a high voltage is applied and the stirrer 11c is applied. Is supplied to the installed spinneret block (4). The spinning solution drop device (3) also serves to block the flow of spinning solution to prevent electricity from flowing in the spinning solution main tank (1).

Subsequently, in the spinning nozzle block 4, the spinning liquid is discharged upward through the upward spinning nozzle 5 to the upper collector 7 where the high voltage is applied, thereby manufacturing the nonwoven web.

At this time, the excess spinning solution supplied to the top of the nozzle block is forcibly transferred to the spinning solution main tank 1 by the spinning solution discharge device (12).

At this time, in order to promote the formation of the fiber by the electric force to the radiation nozzle block 4 and the collector 7 is applied a voltage of 1kV or more, more preferably 20kV or more generated by the voltage generator (9). It is more advantageous in terms of productivity to use an endless belt as the collector 7. The collector 7 preferably reciprocates a certain distance from side to side to make the density of the nonwoven uniform.

When the nonwoven fabric formed on the collector 7 is wound on the winding roller 16 via the nonwoven fabric support roller 14, the nonwoven fabric manufacturing process is completed.

Meanwhile, two or more kinds of polymer spinning solutions may be electrospun on one collector 7 through different nozzles 5 arranged on one spinning nozzle block 4, and two or more kinds of polymer spinning solutions may be used. They may be electrospun on one collector 7 through nozzles 5 arranged on two or more separate spinning nozzle blocks 4, respectively.

In this case, the spinning solution is added and mixed with each of the two or more polymer spinning solutions.

On the other hand, when the nanofiber filament is to be manufactured, as shown in FIG. 2, the nanofibers are electrospun using the collector 7 having grooves 7a having conductors formed at predetermined intervals on the plate of the non-conductor. ), A narrow nanofiber web can be prepared, drawn and stretched.

In addition, in the case of using the collector 7, in which the grooves 7a are not formed at regular intervals as shown in FIG. After cutting to prepare a small nanofiber web, it is also possible to draw and wind it.

The present invention does not specifically limit the apparatus and process for manufacturing nanofiber filaments or nanofiber nonwoven fabrics.

In the nanofiber aggregates prepared according to the present invention, the molecular chains constituting the nanofibers are well oriented in the fiber axis direction to increase the degree of crystallinity, thereby greatly improving mechanical properties as compared to the nanofiber aggregates produced by the conventional method as shown in FIG. 10.

10 is a graph showing the correlation between strain and stress of the nanofiber nonwoven fabric according to the type of acid solution added to the spinning solution.

In addition, according to the present invention, when the acid solution is added to the spinning solution as shown in Figures 3 to 4 compared with the acid solution is not added, the viscosity and surface tension is not significantly different, but the electrical conductivity is greatly improved.

3 is a graph showing a change state of the electrical conductivity of the spinning solution according to the spinning solution composition, Figure 4 is a graph showing a change state of the viscosity and surface tension of the spinning solution according to the spinning solution composition.

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples. However, the present invention is not limited only to the following examples.

Example 1

After dissolving polyvinyl alcohol in distilled water at 80 ° C. for 1 hour (solid content of 10% by weight) and cooling to room temperature, 4% by weight of acetic acid (Acetic acid) was added thereto to prepare a polymer spinning solution. The polymer spinning solution was electrospun onto a collector through a nozzle of 1 mm in diameter under a voltage of 30 kV and a spinning distance of 13 cm in the electrospinning apparatus as shown in FIG. 1, and the nanofiber web electrospun on the collector was separated on the collector and the nano Fibrous nonwovens were made. An electron micrograph showing the surface state of the prepared nanofiber nonwoven fabric is as shown in FIG. 6. In addition, the results of measuring the inertia rotation radius (Radius of Gyration) of the polymer spinning solution and the mechanical properties of the prepared nanofiber nonwoven fabric are shown in Table 2.

Example 2-Example 4 and Comparative Example 1

A nanofiber nonwoven fabric was prepared in the same manner as in Example 1 except that the type and amount of the acidic solution were changed as shown in Table 1. Table 2 shows the results of measuring the inertia rotation radius of the polymer spinning solution and the mechanical properties of the prepared nanofiber nonwoven fabric.

Manufacture conditions division Type of acid solution Addition amount of acidic solution (wt%) Example 1 Acetic acid 4 Example 2 Lactid acid 4 Example 3 Citric acid 4 Example 4 Malic acid 4 Comparative Example 1 No acidic solution added (distilled water added) 0 (addition of distilled water: 4% by weight)

Property evaluation result division Rotation radius of spinning of spinning solution (R ₂ ) Mechanical Properties of Nonwovens Electron micrograph showing the surface condition of nonwoven fabric Yield Stress (MPa) Tensile stress (MPa) Strain (%) Example 1 2.220 × 10 ² 4.2 5.0 65 6 Example 2 2.006 × 10 ² 5.0 8.5 130 7 Example 3 2.241 × 10 ² 6.2 9.4 120 8 Example 4 3.538 × 10 ² 3.7 12.0 420 9 Comparative Example 1 3.306 × 10 ² 10 1.2 25 5

* Mechanical properties of the nonwoven fabric were taken as the average value of five specimens measured using a universal tensile tester according to ASTM D 638 method with a cross-head speed of 10 m / min.

* The inertia rotation radius of the spinning solution was measured using a Dynamic Light Scattering Spectrometer (DLS-700, manufactured by OTSUKA Elecronice co.).

The nanofiber aggregates produced by the present invention are insoluble in water and have excellent mechanical properties despite being produced by electrospinning water-soluble polymer resins.

As a result, the nanofiber aggregate produced by the present invention can be widely applied to various fields of use.

Claims (8)

In producing a nanofiber aggregate by electrospinning a spinning solution obtained by dissolving a water-soluble polymer resin having a terminal group of -OH in distilled water on a collector 7 under high voltage through a spinning nozzle 5 under high voltage. A method for producing a nanofiber aggregate having excellent mechanical properties, characterized by adding and mixing an acidic solution to a working solution. The method of producing a nanofiber aggregate having excellent mechanical properties according to claim 1, wherein the water-soluble polymer resin having a terminal group of -OH is a polyvinyl alcohol-based resin. The method for producing a nanofiber aggregate having excellent mechanical properties according to claim 1, wherein the water-soluble polymer resin having a terminal group of -OH is at least one resin selected from polymers, copolymers and mixtures thereof containing vinyl alcohol. The method of claim 1, wherein the nanofiber aggregate is a nonwoven fabric composed of nanofibers or a continuous filament composed of nanofibers. The nanofiber aggregate having excellent mechanical properties according to claim 1, wherein the acid solution is one solution selected from acetic acid, lactic acid, malic acid, and citric acid. Manufacturing method. The method according to claim 1, wherein the addition amount of the acidic solution is 1 to 30% by weight based on the total weight of the spinning solution. The method according to claim 1, wherein the addition amount of the acidic solution is 1 to 10% by weight based on the total weight of the spinning solution. 2. The electrospinning method according to claim 1, wherein the electrospinning method is (i) a bottom-up electrospinning method in which the spinneret block 4 is located below the collector 7; Nano mechanically excellent mechanical properties, characterized in that it is one of the top-down electrospinning method and (i) horizontal electrospinning method in which the radial nozzle block (4) and the collector (7) is located at a horizontal or similar angle. Method for producing a fiber aggregate.

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