JPS63175157A - Nonwoven fabric - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a nonwoven fabric that exhibits high performance, particularly for use in filters, by specifying the size, shape characteristics, and physical properties of its constituent fibers.

[Prior Art] Demand for filters for body fluids such as blood is increasing, and nonwoven fabrics using fine denier fibers are being put into practical use. For example, the nonwoven fabrics described in JP-A-54-119012 and JP-A-54-119013 are examples. However, the fibers used to manufacture these nonwovens have a diameter of 3.5
Since the nonwoven fabric is a little thick, about ~10 μm, the free space of the nonwoven fabric, which is a folded body of these fibers, is too large, allowing even relatively large substances to pass through easily, making it unsatisfactory as a blood filter.

To address these problems, nonwoven fabrics using fine denier fibers obtained by melt blowing have recently been proposed (Japanese Patent Laid-Open No. 60-193468 and No. 60-2032).
No. 67, etc.), it is expected that the filtration separation efficiency will be improved. However, in the melt-blowing method, the fiber diameter becomes too thin and no stretching action is expected, so the modulus tends to be low.Furthermore, after the nonwoven fabric is finished, the heat setting process that is performed to prevent shrinkage and maintain the structure There is also the problem that the modulus of the fibers further decreases and the compression resistance as a nonwoven fabric further deteriorates.

Furthermore, regarding the problem of free space, it is originally narrowed due to the diameter reduction of the fibers, and the nonwoven fabric as a whole shrinks due to the heat shrinkage caused by the heat setting process, and the fibers become thicker in the direction that narrows the free space. , the free space narrowed by the adoption of the melt blowing method becomes even narrower.

The above-mentioned thickening of the fibers occurs intensively in the area facing the free space, resulting in fiber stiffness, which leads to deterioration of the physical properties as a nonwoven fabric and uneven size of the free space.The latter phenomenon is particularly important for filter selection. It leads to a defect that makes sex bad.

In addition, the lack of compressibility due to the low modulus of the fibers causes the nonwoven fabric to be crushed by suction or pressure when used as a filter, resulting in a narrowing of the free space, resulting in extremely high liquid flow resistance. This causes a problem of loss of filtering function (poor durability as a filter medium).

[Problems to be Solved by the Invention] The present invention has been made focusing on the above-mentioned problems, and its purpose is to prevent the low modulus seen in conventional fine denier fibers and to The purpose of this invention is to provide a nonwoven fabric that can ensure free space as uniform in size as possible, enhance the sorting function during filtration, and maintain bulkiness and compression resistance.

[Means for Solving the Problems] The structure of the nonwoven fabric of the present invention that can achieve the above objects has a fiber diameter of 3 μm or less, a fiber strength (CV) of 0.3 or less, and an initial tensile resistance. The gist is that it is made of synthetic fibers having a weight of 20 g/denier or more.

[Function] The fiber diameter of the synthetic fibers constituting the nonwoven fabric according to the present invention is 3μ
If the 6wX fiber diameter exceeds 3 μm, the nonwoven fabric, which is a folded body of these fibers, becomes visible, and even coarse substances that originally have to be removed are removed. Also, it becomes impractical as a blood filter or the like. However, when fibers with a fiber diameter of 3 μm or less are used, for example, leukocytes in blood can be efficiently separated and removed, and as a result, highly purified red blood cells can be recovered at a high yield. However, if the fiber diameter becomes too thin, not only will the free space of the nonwoven fabric become too small and the filtration resistance will increase, but also, for example, when used as a blood filter, some of the red blood cells will be filtered out along with white blood cells, etc., which will reduce the red blood cell recovery rate. The fiber diameter is preferably set to 0.1 μm or more.

Further, the fiber characteristic (CV) of the synthetic fiber must be 0.3 or less, and more preferably 0.1 or less. II
If the fiber diameter irregularity exceeds 3, the size of the free space formed when it is made into a non-woven fabric will be uneven, and the selectivity of filtration will be reduced, resulting in a low separation efficiency for specific particle size substances. Furthermore, the initial tensile resistance of the synthetic fiber is closely related to its anti-compressibility, that is, the function of suppressing the decrease in permeability due to compression, and it is necessary to use a synthetic fiber that exhibits an initial tensile resistance of 20 g/denier or more. More preferably 30g/
It is more than denier. However, the resistance value is 20g
/With non-denier grooves, the anti-compression strength of the nonwoven fabric is poor,
In particular, when the pressure is less than 108/denier, even a small filtration compression force compresses the nonwoven fabric until it becomes thin, crushing the free space of the nonwoven fabric, drastically reducing liquid permeability, and extremely slowing down the filtration processing speed.

The properties required of the fibers constituting the nonwoven fabric according to the present invention are as described above, but since the fibers have the following properties, the performance of the nonwoven fabric as a filter is even more excellent.

In other words, it has an amorphous sheath-core structure with a surface consisting of huge crystals with markedly oriented molecules and a highly abrasive orientation in one direction, and has a high modulus and low specific gravity.
The utilization rate of the surface boundary layer of the material is high for the same denier, and the filtration performance is extremely excellent. In this respect, the constituent fibers are completely different from conventional nonwoven fabrics formed by heat treatment after entangling yarns.

The raw material polymer for the synthetic fibers used in the present invention can be any polymer that can be easily controlled in shape during spinning and can be processed into fibers at a uniform price and with little denier unevenness. Among them, aromatic or aliphatic polymers can be used. Polyester, polyamide, polyacrylonitrile, or the like is preferable because when used as a blood filter, it adsorbs denatured components in blood or traps sticky substances such as denatured proteins, thereby contributing to cleaning of the filtrate. In the final step of processing, the nonwoven fabric for blood filters is made sterilized by heat treatment using polyethylene oxide gas (approximately 50°C) or heating steam (approximately 120°C).
If heat shrinkage occurs during this heat treatment process, the liquid permeability will decrease due to an increase in fiber diameter, or the anti-compressive force will decrease due to a decrease in modulus, so when selecting fiber materials, it is important to minimize the heat shrinkage rate. It is advisable to choose a small one. It is most preferable to specify the heat shrinkage rate in the state of the final product, which is a nonwoven fabric, and it has been confirmed through experiments that the heat shrinkage rate is 160°C x 30°C as a finished nonwoven fabric.
It has become clear that filters with shrinkage rates in both the longitudinal and transverse directions of 15% or less, more preferably 5% or less, when subjected to dry heat treatment for 30 minutes, can exhibit excellent performance as blood filters. Ta. By the way, the shrinkage rate is 15%.
If the fiber exceeds 20%, the thermal dimensional stability is poor, and the modulus decreases due to heat treatment, resulting in a decrease in anti-compressive force.Furthermore, the free space narrows due to the thickening of the fibers due to shrinkage, resulting in poor liquid permeability. and it becomes difficult to obtain good filtration performance. In addition, the apparent density of the nonwoven fabric of the present invention is a measure of bulkiness that affects filtration performance, and is 0.01 g/cm.
2 or more is preferable, especially when used as a blood filter, 0.05 to 0.5 g/cm by pressing etc.
It is desirable to adjust it to about 2. In this case, conventional fibers using low modulus fine denier fibers are crushed by the press and become vapor-like and thin, resulting in extremely low liquid permeability and impractical.However, in the present invention, as described above, the initial tensile resistance Since it uses fine denier fibers with high denier, it has good bulk retention properties, and the apparent density can be easily controlled while maintaining appropriate bulk as a filter.

The method for obtaining the fine denier fiber used in the present invention is as follows:
Various methods capable of producing ultra-fine denier can be employed, such as the melt blow method, flash spinning method, method of melting the seabird fiber structure obtained by composite spinning, and super draw method, but the most preferred method is the melt blow method. It is. The melt blowing method itself is well known, for example, as described in JP-A No. 59-26561, but even if the known method is applied as is, it is not possible to obtain fine denier fibers that meet the above-mentioned required characteristics. To do this, the spinning temperature must be set at 10 ± 5°C higher than the melting point of the raw material resin, and the traction fluid temperature must also be set at 20 ± 5°C higher than the melting point. It is desirable to set the fluid flow velocity to around Matsuha 1. For example, when polyethylene terephthalate is used as the raw material resin, the most preferable conditions are a spinning temperature of about 275°C and a pulling fluid temperature of about 275°C. The amount of discharge per single hole light can be arbitrarily determined depending on the target fiber diameter, bulk density, etc.
When obtaining fibers with a diameter of m or less, 0.1 to o, otg
/min, more preferably 0.05 to 0.02 g/min.

The fiber group spun under these conditions is made into a nonwoven fabric by hanging the fibers in a three-dimensional manner while intersecting each other on a suctioned drum or net, and interweaving the fibers as appropriate. The distance between the spinning nozzle and the drum or net is such that the fibers are not tightly entangled with each other and form a string, that is, the fibers are layered while intersecting each other three-dimensionally due to the spread and turbulence of the accompanying traction fluid. The distance is set to a sufficient distance, for example, about 30 to 60 cm. The apparent bulk density of the taken-up nonwoven fabric can be adjusted by lightly pressing it with a heating roller or the like or by embossing it, if necessary.

Examples will be given below to further clarify the structure and effects of the present invention. The physical properties of the fibers constituting the nonwoven fabric as defined in the present invention refer to values measured by the following method.

Fiber diameter: The nonwoven fabric was photographed using an electron microscope, 100 fibers were randomly selected from the enlarged photograph, and their diameter (di
) and obtain the average value using the following formula.

From the fiber diameter (di) obtained in the same manner as above, the variation thereof is determined by the following formula.

-Σ(di) Initial tensile resistance value: After pulling out single tAl + Kaso books at random and stringing them to form a single piece of wood, JIS 11074 ('65)
Measure according to

[Example] The melt blow nozzle shown in Fig. 1 [in the figure, 1 is a polymer discharge pipe, 2 is an orifice hole (0.15 mmψ), 53 is a heated fluid outlet (lip width 300 μm), and 4 is a heated fluid temperature detection end, respectively. ], polyethylene terephthalate with an intrinsic viscosity of 0.65 was spun at 275° C. at a discharge rate of 0.025 g/min per orifice, and the heated fluid outlet 3 had a temperature at the detection end 4. 275℃
Melt blowing was carried out while supplying heated air at a pressure of 2.2 kg/cm2, and 40 cal was released from the nozzle discharge end.
The spun fibers were collected on a net moving at a speed of 1 m/min at the position where the fibers were turned, to obtain a nonwoven fabric with a basis weight of 80 g/m2.

This nonwoven fabric is bulky and elastic, and has a soft feel.

This nonwoven fabric was cut into disk shapes with a diameter of 90 mm, and five pieces were stacked on top of each other to a thickness of 7011101 mm. It was fixed on a column with an effective diameter of 80 mm. Next, the entire column was heat treated in steam at 121° C. for 30 minutes and then dried under reduced pressure. Using this column, after briming with physiological saline at 25° C., 500 ml of fresh blood was poured to remove leukocytes, and then 80 ml of physiological saline was poured to recover red blood cells.

Excellent example 2 Nylon 6 with a specific viscosity of 1.3 is used, and the spinning temperature is 270.
A nonwoven fabric was manufactured and a live blood separation test was conducted in the same manner as in Example 1 above, except that the temperature was set at .degree.

Comparative Examples 1 to 5 Nonwoven fabrics were manufactured and live blood separation tests were conducted in the same manner as in Example 1, except that the spinning temperature, the temperature and pressure of the heating fluid (air), and the polymer discharge amount were partially changed. The experimental conditions and results of 1.2 and Comparative Examples 1 to 5 are collectively shown in Table 1.

(See below for Yugyozushin) \,]··hmm From Table 1, it can be considered as follows.

Examples 1 and 2: These are examples that satisfy all of the specified requirements of the present invention, and very good values are obtained for the raw blood processing speed, color blood cell removal rate, and red blood cell recovery rate.

Comparative Example 1: Even though the temperature of the heated fluid during melt blowing was increased by only 15°C, the fiber diameter and initial tensile resistance of the fibers were outside the specified range of the present invention, and the length and width of the nonwoven fabric The shrinkage rate is also very large, and especially the red blood cell recovery rate is significantly reduced.

Comparative Example 2: Even though the polymer discharge temperature during melt blowing was only increased by 5°C, the fiber diameter was outside the specified range of the present invention.The longitudinal and lateral shrinkage rates of the nonwoven fabric were also slightly higher. As a result, both leukocyte removal rate and red blood cell recovery rate are low.

Comparative example 3: The amount of polymer discharged during melt blowing was increased,
This is a comparative example in which the fiber denier has been increased to the same level as the conventional product, and although the red blood cell recovery rate is high, the filter is significantly clogged, the raw blood processing speed is reduced, and the white blood cell removal rate is significantly reduced. It is declining.

Comparative Example 4.5: The traction fluid temperature during spinning was set high, or the spinning temperature was set high, resulting in a large fiber diameter skin, insufficient initial tensile resistance, and longitudinal and transverse shrinkage. In Comparative Example 4, the raw blood processing speed is slow and the red blood cell recovery rate is low.

Furthermore, the membrane of the nonwoven fabric of Comparative Example 5 is also our best. It was judged that it was extremely difficult to put it into practical use. The filter performance evaluation test is currently in progress. It stopped.

[Effects of the Invention] The present invention is configured as described above, and by specifying the diameter and strength of the fibers constituting the nonwoven fabric, as well as the initial tensile resistance value, it is possible to create a free space of an appropriate and uniform size throughout. It has now become possible to provide a nonwoven fabric that is bulky and has excellent compression resistance.

In addition, this nonwoven fabric has excellent pore characteristics and structural strength that can withstand high compression forces, so it can be used in blood filters, various industrial filters (including bag filters, etc.), mask filters, and air purification. Not only can it exhibit excellent performance as a filter, etc., but it can also be widely used as a heat insulator, sterilization medium, sanitary material, etc.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a melt blow nozzle used in an example. 1... Polymer discharge amount 2... Orifice hole 3...
・Heated fluid outlet 4...Heated fluid detection end Figure 1

Claims (4)

[Claims] (1) Fiber diameter is 3 μm or less, fiber diameter unevenness (CV) is 0.3
A nonwoven fabric characterized by being made of synthetic fibers having the following properties and having an initial tensile resistance of 20 g/denier or more. (2) The nonwoven fabric according to claim 1, which has a dry heat shrinkage rate of 15% or less in both the longitudinal direction and the transverse direction. (3) The nonwoven fabric according to claim 1 or 2, wherein the synthetic fiber is a thermoplastic synthetic fiber produced by a melt blowing method. (4) The nonwoven fabric according to any one of claims 1 to 3, which is used as a filter.