KR100640235B1 - Apparatus and Method For Estimating Pore Structure of Electro-spun Web - Google Patents

Abstract

The present invention relates to a method capable of measuring the pore size in real time as well as to the distribution of the pore size of an opaque web, and to such a measuring device. More specifically, the pore size is obtained by an image input device, and a laser measuring device and a thickness measurement Provided are methods for measuring the pore size and distribution of pore size over the entire web in real time by calculating the number n of layers corresponding thereto using a device and a technique for such a device.

Fiber aggregate, pore size, real time, laser, image input device, depth of focus, CCD camera

Description

Apparatus and Method For Estimating Pore Structure of Electro-spun Web}

1 is a conceptual diagram of a measuring device capable of measuring the pore size of the fiber assembly according to the present invention.

FIG. 2 is a conceptual diagram illustrating a relationship in which n pore sizes have pore sizes of the entire lattice based on one lattice, assuming that the fiber assembly is composed of n layers.

<Explanation of symbols for the main parts of the drawings>

1: solution reservoir 2: spinning nozzle

3: high voltage generator 4: light source

5: Video input device 6: Analysis device

7: control device 8: thickness measuring device

9: laser measuring device

The present invention measures the filtration performance by measuring and analyzing the pore size and pore size distribution of the web (i.e., the fiber aggregate) through a real-time pore structure evaluation technology, more specifically, melting, dry, wet, wet and wet and electrospinning processes. It relates to a technique for evaluating.

The technique for evaluating pore characteristics of conventional fiber aggregates (including woven fabrics and nonwoven fabrics) includes: (i) a method of measuring the distribution of pores according to the amount of passage of liquid while passing the liquid in the vertical direction while increasing the pressure at regular intervals, (ii) measuring the filter efficiency by passing the standard dust through a fiber assembly under a certain pressure; (iii) measuring the distribution of pores by image processing after obtaining images of the pores while passing light using optical equipment. It is divided into ways. The methods of (i) and (ii) are commonly used in laboratories in which it is impossible to evaluate the structure of pores in real time due to the nature of the measurement method, and the method of (iii) is applicable in real time in principle, There was a drawback of limited application to only sufficient thin fiber assemblies.

An object of the present invention relates to a method capable of measuring the pore size in real time, and also to measuring the pore distribution of an opaque web in order to solve the above problems, and more particularly, to melt, dry, The present invention provides a technique and method for measuring and analyzing the pore size and pore size distribution in real time in order to evaluate the filtration performance of the web through wet, wet and electrospinning processes.

The present invention is a method for measuring the pore size and the distribution of the opaque web in real time, the measuring method according to the present invention comprises the steps of irradiating light of high brightness; Receiving an image from the irradiated light; Measuring pore size and depth of focus from an input image; Measuring the total thickness of the web with a laser to analyze the input image to calculate the total pore size and the number of layers constituting the web; And estimating the pore size using the distribution function and the probability density function for the pore size.

In addition, the measurement method according to the present invention estimates the distribution of pore sizes based on the following equation, where n is the number of layers of the web, λ is the mean of the pore sizes, and t is the time, respectively.

In addition, the apparatus according to the present invention comprises: (i) a light source for irradiating light from one side to the center of the traveling web; (ii) an image input device including a microscope, a CCD camera, and a surface displacement input device for receiving an image formed by the irradiated light; (iii) a laser device for measuring the overall thickness of the web; (iv) an analysis device for receiving the input image and the overall thickness to calculate the pore size and the pore size distribution; And (v) a controller for controlling the discharge pressure of the polymer solution, the applied voltage or the descent distance of the fiber, wherein the analysis device uses the focal depth and the total thickness of the web to determine pore size and pore size. It is characterized by calculating the distribution.

In the above measuring apparatus, the present invention estimates the distribution of pore sizes based on the following equation, where n is the number of layers of the web,? Is the mean of the pore sizes, and t is the time.

There are various processes such as melt spinning, dry spinning, wet spinning, wet and wet spinning, and electrospinning. In particular, the electrospinning process is one of the methods for producing nanofibers. It is attracting attention as an optimal material of the filter or membrane because it can produce ultra-fine fibers having a.

As one example of these spinning processes, the electrospinning process will be described in detail as follows. However, the following electrospinning process is intended to illustrate the present invention, the nonwoven fibers of the present invention can be prepared by a variety of processes, such as melt spinning, dry spinning, wet spinning, wet and wet spinning, electrospinning and only the following electrospinning process It is not limited.

In the electrospinning process, the web of nonwoven fibers falls on the focusing belt by high pressure while being exposed to high voltage and finely divided before the solvent evaporates and fibrates. Typically, the web is formed by the contact of finely divided fibers, resulting in the formation of thick webs stacked in parallel in several layers over time. Therefore, the entanglement of the fibers in the vertical direction is extremely excluded and forms a multilayer structure mainly arranged parallel to the plane axis.

The average size of the pores is mainly determined by the amount of discharge per unit time and the diameter of the fiber, and the uniformity of the size varies with various process variables such as voltage, spinning solution concentration and discharge pressure. As the pore distribution changes, the micropore structure of the web changes, which affects the filtration and permeation performance of the web.

In the electrospinning process, an increase in the discharge pressure is accompanied by an increase in the discharge amount per unit time, which is accompanied by an increase in the fiber diameter, thereby reducing the pore size of the web, which may be offset by an increase in the applied voltage and also It can also be influenced by adjusting the descent distance.

This ability to measure the pore size and distribution affecting the permeation and filtration performance of the web during electrospinning allows the process to increase or decrease the applied voltage, discharge pressure, and descent distance as needed. It can be a useful means.

As described above, the present invention is a method for measuring the pore size and distribution of an opaque web in real time in order to evaluate the filtering performance of the web undergoing an electrospinning process, the method comprising: irradiating high-brightness light from a light source 4, Receiving an image formed by the irradiated light, Analyzing the size of the pores by analyzing the input image, Measuring the overall thickness of the web using a laser measuring device (9), Measuring the overall thickness of the web And calculating the number of layers needed to calculate the total pore size and distribution using the depth of focus measured in the previous step, and estimating the pore distribution using the pore size and the calculated number of layers. .

In addition, as described above, the present invention is a device for measuring the pore size and distribution of the opaque web in real time in order to evaluate the filtration performance of the web undergoing the electrospinning process, the light from one side centering on the progressing web A light source 4 for irradiating the light, an image input device 5 for receiving an image formed of irradiated light, a laser measuring device 9 for measuring the overall thickness of the web, and a constant web for measuring the thickness of the web. A thickness measuring device 8 for applying pressure, and an analysis device 6 for calculating the pore size and pore size distribution by analyzing the input image, the depth of focus, and the measured thickness of the web.

When the light source 4 is used as a reflected light source, the light source 4 and the image input device 5 are located on the same side with respect to the web surface, and when the light source 4 is used as a transmitted light source, the light source 4 and the image input The device 5 is configured to be on the opposite side with respect to the web side.

The image input device 5 is composed of a microscope, a CCD camera, and a surface displacement measuring device, and preferably, a light source of high brightness is used as the light source 4, and more preferably a halogen light source of high brightness.

When the image generated by the light source 4 is input and the frame grabber converts the analog image signal into a digital image, the analyzer 6 measures the size of pores shown in the digital image.

)를 측정하고 레이저 측정 장치(9)는 웹의 전체 두께(

)를 측정함으로써 디지털 영상을 분석하여 측정한 것과 같은 층(layer)이 몇 개 있는 것과 동등한가를 측정한다. 즉, 웹이 균일한 n개의 층으로 평행 적층 배열되어 있다고 가정하였을 때 다음 식이 성립한다.Depth of focus (using the microscope of the image input device 5)

) And the laser measuring device 9 measures the overall thickness of the web (

) To determine how many layers are equivalent to the digital image. In other words, assuming that the webs are arranged in parallel stacked layers of n uniform layers, the following equation holds.

The analyzer 6 receives the focal depth measured using the microscope of the image input apparatus 5 and the total thickness measured from the laser measuring apparatus 9, calculates the number of layers, and calculates the number of layers. Using the data on pore size, estimate the overall pore size and pore size distribution according to the following logic.

The web is arranged in parallel stacks of virtually uniform n layers, each layer consisting of a number of unit grids of the same size, with only one pore in the lattice and the pore size in that layer following an exponential distribution. Assume

이라 하면, 한 격자의 수직방향의 기공도를 결정하는 확률변수 Y는In this case, the pore distribution of the stacked multi-layered nonwoven fabric is determined by the minimum pore size of the n-layer vertically arranged gratings for the particular grating. The pore size of each of the n layers

In this case, the random variable Y that determines the porosity in the vertical direction of a lattice

(See Fig. 2).

The distribution function of Y is

라면,If the pore distribution in one layer is exponential and the mean of pore sizes in that layer is

Ramen,

The probability density function of Y

When the distribution of the pores is derived by estimating the distribution of the pores by the method described above, the controller 7 can be used for controlling the discharge pressure of the polymer solution, controlling the applied voltage, or controlling the falling distance of the fiber. That is, if the distribution of pores estimated by the probability density function is too large, the discharge pressure is increased, the applied voltage is lowered, or the fall distance of the fiber is controlled to increase, and conversely, the probability density function is estimated by the above probability density function. If the distribution of the pores is too small, it is controlled to reduce the discharge pressure, increase the applied voltage, or shorten the falling distance of the fiber.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on the following Example. However, the following examples are not intended to limit the present invention, but are not limited thereto. Various physical property evaluations of the yarns and treatment cords prepared in Examples and Comparative Examples of the present invention were performed by the following methods.

Example 1 and Comparative Example 1

Example 1 measured the pores of the transparent web sample 1 by a pore measuring device and a measuring method according to the present invention, and Comparative Example 1 measured the pores of the web sample by a method in which the same sample is dependent only on the existing high-brightness illumination. The results are listed in Table 1, respectively.

Example 2 measured the pores of the opaque web sample 2 by the pore measuring device and the measuring method according to the present invention, and Comparative Example 2 measured the pores of the web sample by a method in which the same sample depends only on the existing high-brightness illumination. The results are shown in Table 1, respectively.

Example 3 measured the pores of the opaque web sample 3 by the pore measuring device and the measuring method according to the present invention and Comparative Example 3 is a method for measuring the pores by the change of the liquid passage rate according to the existing pressure of the same sample The pores of the web samples were measured, and the results are shown in Table 3, respectively.

TABLE 1

One 2 3 Example 540 550 570 Comparative Example 560 Not measurable 580

(Unit: nm)

Example 1 and Comparative Example 1 showed almost similar measurement results for Web Sample 1, which is a transparent web sample. However, for the opaque web sample 2, Comparative Example 2 could not measure the pore size because light did not pass, but Example 2 was possible. In addition, for the opaque web sample 3, Comparative Example 3 was able to measure because it was not using a light source, but it was not possible online, while Example 3 proved to be a better method because it was possible to measure as well as online. It was.

As described above, the present invention can not only measure and analyze the pore size and pore size distribution in real time to evaluate the filtration performance of the web undergoing the electrospinning process, but also the pore size and pore size distribution of the opaque thick web. Provides a technique for measuring and measuring devices that can be measured.

While the invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims. .

Claims (4)

In the method for measuring the pore distribution of the opaque web produced by the electrospinning process in real time, (a) irradiating high brightness light; (b) receiving an image from the irradiated light; (c) measuring the pore size and depth of focus from the input image: (d) measuring the total thickness of the web with a laser and analyzing the input image to calculate the total pore size and the number of layers that make up the web Doing; And (e) estimating the size of the pores using a distribution function and a probability density function for the pore sizes. The method of claim 1, wherein the probability density function is

Wherein n is the number of layers of the web, λ is the mean of the pore sizes, and t is the time, respectively. An apparatus for measuring the pore distribution of an opaque web produced by an electrospinning process in real time, (i) a light source for irradiating light from one side to the center of the traveling web; (ii) an image input device including a microscope, a CCD camera, and a surface displacement input device for receiving an image formed by the irradiated light; (iii) a laser device for measuring the overall thickness of the web; (iv) an analysis device for receiving the input image and the overall thickness to calculate the pore size and the pore size distribution; And (v) a controller for controlling the discharge pressure, applied voltage, or descent distance of the polymer solution, The analysis device is a device for measuring the pore distribution of the opaque web, characterized in that for calculating the pore size and the distribution of the pore size using the depth of focus and the total thickness of the web by the microscope. The device of claim 3, wherein the analysis device is

A pore distribution is calculated using a probability density function, where n is the number of layers of the web, λ is the mean of the pore sizes, and t is the time.

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