KR20080095623A - Ultra fine fiber, manufacturing method thereof and manufacturing method of carbon nanofiber - Google Patents

Abstract

A carbon nano fiber is provided to mass-produce the carbon nano fiber by a manufacturing method of the nanofiber using a sea island typed fiber manufacture method and an electricity spinning method, to obtain an ultra-fine fiber having a special structure, and to manufacturing easily the carbon nano fiber. A spinning solution is manufactured by a difficultly soluble polymer and an easily soluble polymer with a solvent. A fine-fiber is obtained by authorizing a voltage to the spinning solution. An ultra-microfilament is manufactured by removing the easily soluble polymer by washing the fine-fiber with a wiping solvent in which the easily soluble polymer is selectively dissolved. The difficultly soluble polymer is a poly acrylonitrile(PAN) or a PAN copolymer. The easily soluble polymer is a polyvinyl alcohol(PVA), a polyethylene oxide(PEO) or a polyvinylpyrrolidone(PVP).

Description

Ultrafine Fiber, Manufacturing Method and Carbon Nanofiber Manufacturing Method {NanoFiber, Manufacturing Method Thereof And Manufacturing Method of Carbon NanoFiber}

Figures 1a to 1d is a surface fine form of the ultrafine web of the web according to an embodiment of the present invention (PAN: PVA = 4: 6), (a), (b) is the form of the surface of the as-spun ultrafine fibers , (c), (d) is a photograph showing the split microfiber form (100 ℃, 5 minutes) after the hot water treatment,

Figures 2a to 2d is a microstructure of the surface of the ultra-fine fiber web according to an embodiment of the present invention (PAN: PVA = 5: 5), (a) the state of the web, (b) the surface of the ultra-fine fibers, (c ) Nanofiber web after hydrothermal treatment (100 ° C., 5 minutes), (d) micrograph of split nanofiber after hydrothermal treatment,

Figure 3a to 3d is a surface fine form of the ultra-fine fiber web according to an embodiment of the present invention (PAN: PVA = 6: 4), (a), (b) is the surface form of as-spun ultra-fine fibers, (c), (d) picture showing the surface shape of the split microfiber (100 ° C, 5 minutes) after the hot water treatment,

Figure 4 is a photograph after the heat treatment (60 ~ 260 ℃, heating rate 1 ℃ / min, holding time 60 min) the ultra-fine fibers according to an embodiment of the present invention (PAN: PVA = 5: 5).

The present invention relates to an ultrafine fiber, a method for producing the same, and a method for producing carbon nanofibers.

As the microfibers still have a lot of unknown parts and as the fibers are further refined, the expectation is that they will be developed and used for what function.

The manufacturing method of the ultra fine fibers can be largely classified into direct spinning method and composite spinning method. However, the micro fiber by the direct spinning method has its fineness and the stability of the manufacturing process is problematic. It is common to manufacture a composite spinning method that can adjust the fineness, and the typical one is a manufacturing method of ultra fine yarn by the island-in-the-sea manufacturing method.

Background Art [0002] An extremely large number of islands-in-the-sea composite fiber production methods and apparatuses have been proposed. However, even if the number of island components can be increased, it is difficult to increase the mass ratio occupied by the island components with respect to the sea component. In other words, if the ratio is increased, the island-in-sea relationship is reversed, and the polymer used for the purpose of forming the island component is in a continuous state to form a sea component, or it is possible to increase the number of island components. There is a problem that the area per discharge hole of the spinneret becomes large. In this case, it is also difficult to control the position and number of island components, resulting in various problems such as obtaining a heterogeneous composite fiber.

In particular, the island-in-the-sea yarn manufactured by manufacturing sea island-like fibers having a thickness of about 20 μm and then eluting the island components can produce nanofibers of at least 800 nm, and this product has been commercialized. The production and practical use of ultra-fine nanofibers of several hundred nm is difficult in the conventional method.

The present invention is to solve the above problems, by combining the manufacturing technology of the island-in-the-sea fiber to obtain the fine fibers and the manufacturing technology of the nanofibers using the electrospinning method, ultra-fine nanofibers, especially ultra-fine nanofibers having a fiber diameter of 100nm or less For the purpose of manufacturing.

The present invention for achieving the above object

Preparing a spinning solution by mixing a island component polymer, which is a hardly soluble polymer, and a sea component polymer, which is a soluble polymer, with a solvent; Applying a voltage to the spinning solution and electrospinning to obtain fine fibers; And a step of removing the sea component polymer by washing the obtained microfibers with a washing solvent in which the sea component polymer is selectively dissolved.

In addition, the island component polymer is a PAN copolymer copolymerized with polyacrylonitrile (PAN) or another polymer, and the sea component polymer is polyvinyl alcohol (PVA), polyethylene in which all or part of an ester group is hydrolyzed with alcohol. Oxide (PEO) or polyvinylpyrrolidone (PVP) provides a method for producing ultra-fine fibers, characterized in that.

In addition, in the step of preparing the spinning solution, the mixing weight ratio of the island component polymer and the sea component polymer provides a method for producing ultra-fine fibers, characterized in that 4: 6 ~ 6: 4.

In addition, the solvent of the spinning solution provides a method for producing ultra-fine fibers, characterized in that dimethyl sulfoxide (DMSO).

In addition, in the step of removing the sea component polymer by washing with the washing solvent, the washing solvent provides a method for producing ultra-fine fibers, characterized in that the water heated to 60 to 100 ℃.

In addition, in the step of removing the sea component polymer by washing with the washing solvent, the washing solvent provides a method for producing ultra-fine fibers, characterized in that the water heated to 60 to 100 ℃.

The present invention also provides a method for producing ultrafine fibers, wherein the average diameter of the fine fibers obtained by the electrospinning is 250 nm or less.

The present invention also provides an ultra-fine fiber produced by the manufacturing method, the fiber bundle is divided into an ultra-fine fiber having an average diameter of 100nm or less.

In addition, after the step of removing the sea component polymer provides a method for producing an ultra-fine fiber, characterized in that further comprising the step of heat treatment at 100 ~ 300 ℃ oxidative stabilization process.

In addition, the present invention provides a carbon nanofiber manufacturing method further comprising the step of carbonizing the ultrafine fibers in an inert gas or vacuum atmosphere after the oxidation stabilization step.

The present invention will be described in more detail with reference to the following Examples. The following detailed description is for the purpose of describing the exemplary embodiments of the present invention, but the present invention is not intended to limit the scope of the rights defined by the appended claims, even though there is a certain or limiting expression.

Nanofiber manufacturing technology using electrospinning is a technology capable of producing fine fibers as a spinning process for obtaining fine fibers. Using this technique, if the island-in-the-sea fine fibers are manufactured and sea components are washed and removed, ultrafine nanofibers of several nm to several tens of nm can be produced. That is, the finer nanofibers can be obtained by removing the sea component again from the finely obtained fibers by the electrospinning process.

Through this, it is possible to obtain a very fine ultra-fine nanofibers than the conventional microfibers obtained through the conventional electrospinning process, than the existing island-in-the-sea fine microfibers.

Method for producing an ultra-fine fiber according to the present invention comprises the steps of preparing a spinning solution by mixing the island component polymer which is a poorly soluble polymer and the sea component polymer which is a soluble polymer with a solvent, Applying a voltage to the spinning solution to electrospin to obtain microfibers, and washing the obtained microfibers with a washing solvent in which the sea component polymer is selectively dissolved to remove the sea component polymer. do.

The step of preparing the spinning solution is prepared by mixing the solvent with a solvent-based polymer and a sea component polymer as a main component. In addition, if necessary, additives known in the art may be further included, which are also included in the present invention.

The island component polymer and the sea component polymer include a sea-soluble polymer that can be dissolved and removed in a washing solvent in a subsequent washing and removing process, and uses a sea-soluble polymer and a poorly soluble polymer that does not dissolve in the washing solvent. It is divided into island-based polymers.

Examples of the island component polymer include, but are not limited to, polyacrylonitrile (Ho-PAN) or PAN copolymer (Co-PAN) copolymerized with other polymers. As a copolymer composition, a (meth) acrylate type, itaconic acid, etc. are mentioned.

Examples of the sea component polymer include polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), or the like, in which all or part of the ester group is hydrolyzed with alcohol. Can be.

In the step of preparing the spinning solution, the mixing weight ratio of the island polymer and the sea polymer is not limited, but is preferably 4: 6 to 6: 4. If there is a large amount of sea component polymer beyond the above range, the waste of sea component polymer that is eventually removed increases, which is not preferable.If the content of the island component polymer is exceeded, the coagulation between the island component polymers occurs, resulting in extremely fine fibers. The frequency with which splitting does not occur may increase.

The solvent is not limited as long as it can dissolve or evenly disperse the island polymer and the sea component polymer, and may be tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAc), alcohols, or dimethyl sulfoxide ( DMSO) may be used alone or in combination, preferably DMSO.

Although the content of the solvent is not limited, it is preferable to adjust the amount of the solvent so that the viscosity is 30 to 120 poise, preferably about 90 poise. The preferred solvent content is such that the total concentration of the island component polymer and the sea component polymer is 5 to 50% by weight.

Next, the spinning solution prepared above is electrospun to obtain fine fibers.

The method of electrospinning is not limited. For example, the prepared spinning solution is connected to the spinneret, a voltage of 50 kV is applied, and the distance between the spinneret and the current collector is kept 0.1 cm per hole. A method of electrospinning by discharging at 3 cc / g.

Next, the microfibers obtained by the electrospinning are washed with a washing solvent to remove the sea component polymer to obtain ultrafine fibers. In other words, when the sea component polymer of the island-in-the-sea fiber is removed through the washing process, only the island-based polymer remains, thereby obtaining more fine fibers.

The washing solvent is not limited as long as it can selectively dissolve the sea component polymer, preferably water with less environmental pollution is preferable. For water, it is recommended to use distilled water.

At the time of washing, even when washed with a washing solvent at room temperature, it can be seen to some degree of washing effect, preferably to wash the washing solvent by heating for a short time effective washing, when using water, to 60 to 100 ℃ It is advisable to clean it using heating, especially boiling water. The washing time is not limited, but boiling water is preferably about 3 to 20 minutes. The washing method may be performed by immersing and washing the island-in-the-sea fibers obtained in the washing solvent, or by flowing with a flowing washing solvent, but is not limited thereto.

After the washing process, a drying process may be added, and may also be prepared by heat treatment at 100 ~ 300 ℃ oxidative stabilization treatment to produce ultra-fine fibers. For example, the temperature may be elevated to 260 ° C. at a temperature increase rate of 1 ° C./min, and then subjected to an oxidation stabilization process in an oxidizing gas atmosphere for one hour.

The ultrafine fiber according to the present invention prepared by the above method is characterized by the presence of a fiber bundle divided into ultrafine fibers having an average diameter of 250 nm or less. That is, the microfiber obtained after electrospinning is an island-in-the-sea microfiber composed of a sea component polymer and a island component polymer that is divided into a plurality of fibers. There are structural features present in bundle form.

The present invention also provides a method for producing carbon nanofibers. When the ultrafine fibers prepared by the above production process are carbonized in an inert gas or vacuum atmosphere, ultrafine carbon nanofibers can be obtained. Examples of the inert gas include helium, neon, argon, and the like, and argon is preferable. It is good to carbonize using a carbonization furnace, and the carbonization temperature is not limited, but it is good to perform at 800 ~ 1500 ℃.

It will be described in more detail through the following examples.

Table 1 shows the composition and concentration of the polymer solution as an example for producing island-in-the-sea fine fibers. Polyacrylonitrile (PAN) is used as a co-constituent, and homo-polymer product with molecular weight of 150,000 g / mol and co-polymer (90% AN content) with molecular weight of 40,000 g / mol are used. Silver polyvinyl alcohol (PVA, Poly vinylalcohol) was used for easy removal using hot water, and experiments were carried out with different hydrothermal solubility using two or more partially alcoholated PVA. The solution was prepared with three compositions of 4: 6, 5: 5, and 6: 4 ratios of PAN and PVA, and the concentrations in the range of bags available for electrospinning of each solution are shown in Table 1 through many tests. The solvent for preparing the spinning solution was prepared using dimethyl sulfoxide (DMSO), a co-solvent of PAN and PVA.

Viscosity of the solution was measured in the range of 30 to 90 poise, and microfibers were obtained at high viscosity, unlike the result of general electrospinning, in the solution of 4: 6 composition ratio with high PVA content. The viscosity value measured was about 90 poise, and the fiber diameter of the obtained fine fiber was about 250 nm or less. In general, considering the correlation between viscosity and fiber diameter in the case of a single component solution, a fiber diameter of about 2,000 nm or less is obtained for a solution having a viscosity of 90 poise.

Figure of Ingredient PAN Sea Ingredient PVA Composition ratio density(%) Example 1 Ho-PAN Fully 6: 4 10 to 12 Example 2 5: 5 Example 3 4: 6 Example 4 Partially 6: 4 12 to 16 Example 5 5: 5 Example 6 4: 6 Example 7 Co-PAN Fully 6: 4 18 to 22 Example 8 5: 5 Example 9 4: 6 Example 10 Partially 6: 4 24 to 27 Example 11 5: 5 Example 12 4: 6

Hydrothermal Post-Treatment Conditions and Results of Example 9 Post Processing Condition Reduction amount (g) Web weight (excluding Al foil) % Actual reduction One Dry 0.0009 0.0327 2.8 2 Wash + Dry 0.0119 0.0299 39.8 3 Treatment (5 ') + Wash + Dry 0.0143 0.0309 46.3 4 Treatment (10 ') + Wash + Dry 0.0145 0.0319 45.5 5 Treatment (20 ') + Wash + Dry 0.0141 0.031 45.5

* Treatment: Washing treatment with hot water at 100 ℃ for each hour

* Wash: Wash with 10 distilled water for 10 minutes

* Dry: Treated for 30 minutes in hot air dryer at 60 ℃

Table 2 shows the results obtained by hydrothermally treating Example 9 in which the ratio of PAN and PVA is 4: 6. No. 1 and No. 2 were blank tests, which were used as reference data after checking the weight change of a simple dry sample and washing with distilled water at room temperature for 10 minutes. The sample was dried for 30 minutes at 60 ° C.

As a result of the hydrothermal post-treatment, it was confirmed that after only 5 minutes in boiling water, about 40% of the weight was removed from the dried sample, that is, most of the PVA components were removed, and the microstructure was observed using a real scanning electron microscope (SEM). As a result, it was confirmed that the split nanofibers were prepared. After that, even if the hydrothermal treatment for more than one hour was found that the weight loss does not occur significantly.

1A to 1D, 2A to 2D, and 3A to 3D are microfibers before hydrothermal treatment with PAN: PVA of 4: 6 (Example 3), 5: 5 (Example 2), and 6: 4 (Example 1), respectively. And micrographs (SEM) of the surface fine morphology of the ultrafine fiber web after the hydrothermal treatment. The microfiber web before the hydrothermal treatment has the same shape as the web obtained after the general electrospinning, and the ultrafine fibers (segmented microfine fibers) after the hydrothermal treatment where sea components are removed by performing the hydrothermal treatment at 100 ° C. for about 5 minutes are 100 nm or less. To form very fine fibers. The sample with a solution composition of 6: 4 had a portion where the surface of the microfibers was not completely divided after the hydrothermal treatment, and the scratch shape was found to be somewhat incompletely divided (see FIG. 3). In the example, it can be seen that after the hydrothermal treatment, all the fibers are split to form split type ultrafine fibers of 30 nm to 100 nm (see FIG. 1). The overall shape of the web has a membrane-like structure. For the 5: 5 composition solution with the same ratio of PAN and PVA, coarse microfibers were more completely divided to form fiber bundles, and the fine microfibers were found to be somewhat incomplete.

Fig. 4 is a micrograph of stabilized fiber which undergoes oxidation stabilization process in oxidizing gas atmosphere for one hour after heating up split PAN ultrafine fiber obtained by hot water treatment to 260 ° C at a heating rate of 1 ° C / min. As a result of the combustion test, the oxidation was stabilized well, and the shape of the split microfiber web was maintained. The chemical vapor deposition method applied to the production of CNF or GNF of several nm to several hundred nm has been a bottom-up technique for producing fiber form through chemical vapor deposition of carbon-rich gas. Representative technology for manufacturing a carbon material, but the mass production was difficult. This technology is a technology for manufacturing carbon nanofibers of 100 nm or less and is the world's first mass-produced CNF manufacturing technology that can be mass-produced as a top-down technology for the production of split microfibers in solution electrospinning.

The present invention combines the manufacturing technology of nanofibers using the island-in-the-sea fiber manufacturing and the electrospinning method is excellent in mass production, it is possible to obtain a very fine fiber having a specific structure, and also based on this easy to manufacture carbon nanofibers There are advantages to it.

Claims (9)

Preparing a spinning solution by mixing a island component polymer, which is a hardly soluble polymer, and a sea component polymer, which is a soluble polymer, with a solvent; Applying a voltage to the spinning solution and electrospinning to obtain fine fibers; And And washing the obtained microfibers with a washing solvent in which the sea component polymer is selectively dissolved to remove the sea component polymer. The method of claim 1, wherein the island component polymer is a polyacrylonitrile (PAN) or a PAN copolymer copolymerized with another polymer, the sea component polymer is a polyvinyl alcohol in which all or part of the ester group is hydrolyzed with alcohol ( PVA), polyethylene oxide (PEO) or polyvinylpyrrolidone (PVP) manufacturing method of ultrafine fibers, characterized in that. The method of claim 1, wherein in the step of preparing the spinning solution, the mixing weight ratio of the island component polymer and the sea component polymer is 4: 6 to 6: 4. The method of claim 1, wherein the solvent of the spinning solution is dimethyl sulfoxide (DMSO). The method of claim 1, wherein in the step of removing the sea component polymer by washing with the washing solvent, the washing solvent is water heated to 60 to 100 ° C. 6. The method of producing an ultrafine fiber according to claim 1, wherein the average diameter of the microfibers obtained by electrospinning is 250 nm or less. According to claim 1, After the step of removing the sea-component polymer, the method of producing an ultrafine fiber, characterized in that further comprising the step of heat treatment at 100 ~ 300 ℃ oxidative stabilization process. An ultrafine fiber produced by the manufacturing method of any one of claims 1 to 7, wherein a fiber bundle divided into ultrafine fibers having an average diameter of 100 nm or less exists. A method of producing carbon nanofibers by carbonizing an ultrafine fiber prepared by the method of any one of claims 1 to 7 in an inert gas or vacuum atmosphere.

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