JPS63175156A - 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 Application Field] The present invention is made of ultra-fine synthetic fibers, and
By specifying the dry heat shrinkage rate in the lateral direction and the transmitted microwave intensity ratio in the longitudinal and lateral directions, the present invention relates to a nonwoven fabric that exhibits high performance especially for use in filters.

[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.

Moreover, nonwoven fabrics used as filters for body fluids such as blood are sterilized by being heat-treated (about 50°C) using polyethylene oxide gas or the like or heated steam (about 130°C) in the final process of processing. Although it is
In conventional nonwoven fabrics, the heat shrinkage caused by this heat treatment process is large, and as a result, the free space is narrowed, and the free space is further narrowed due to the thickening of the fibers due to heat shrinkage. The free space narrowed by the diameter becomes even narrower. As a result, the mesh of the nonwoven fabric becomes too narrow, increasing resistance to liquid passage, and even fine substances such as red blood cells that should normally be allowed to pass through are filtered out, thus defeating the purpose of filtration and separation.

On the other hand, the uniformity of the free space is cited as a factor that affects the filtration performance of nonwoven fabrics.In order to improve the filtration performance, it is best to have the free space size as constant as possible and the pore distribution to be narrow. Although it seems that qualitative knowledge has been obtained that filtration performance is preferable, there has been no research that pursues the quantitative relationship between the uniformity of the free space of nonwoven fabrics and filtration performance.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned circumstances, and its purpose is to solve the above-mentioned problems, particularly the diameter of the fibers constituting the non-woven fabric, heat shrinkage of the non-woven fabric, and The purpose of this invention is to solve the problem of poor filtration performance due to the uniformity of free space, and to provide a nonwoven fabric that can exhibit excellent performance as a filter.

[Means for Solving the Problems] The structure of the nonwoven fabric of the present invention that has achieved the above object is made of synthetic fibers with a single fiber diameter of 3 μm or less,
The dry heat shrinkage rate in the longitudinal and transverse directions at °C is 15% each.
The gist is as follows and below.

[Function] The fiber diameter of the synthetic fibers constituting the nonwoven fabric according to the present invention is 3μ
m or less, more preferably 2 μm or less. If the fiber diameter exceeds 3 μm, the nonwoven fabric, which is a folded body of these fibers, becomes visible and allows coarse substances that should originally be removed to pass through, making it impractical as a blood filter, etc. Become. However, if fibers with a fiber diameter of 3 μm or less are used, for example, leukocytes in blood can be efficiently separated and removed.
As a result, it becomes possible to collect highly purified red blood cells at a high yield. However, if the fiber diameter becomes too thin, not only will the free space of the nonwoven fabric become too narrow 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., making it difficult to recover the red blood cells. The fiber diameter is preferably set to 0.1 μm or more, since the fiber ratio decreases.

Next, the dry heat shrinkage rate of the nonwoven fabric according to the present invention at 160° C. in the longitudinal direction and the transverse direction must be 15% or less, and more preferably 5% or less. If the shrinkage rate exceeds 15%, the thermal dimensional stability of the product filter is poor, and it shrinks during the heat treatment process for sterilization as described above, creating a gap between the filter support material and the filtration separation. In addition, the narrowing of the free space due to heat shrinkage and the narrowing of the free space due to the thickening of the fibers may cause the mesh of the nonwoven fabric to become too dense, which not only increases the resistance to liquid flow. Filtration separation efficiency also decreases.

Furthermore, when the nonwoven fabric of the present invention is used as a filter, it is desirable that the size of the pores formed by the free space be as constant as possible in order to successfully filter and separate solids of a specific size. That is, even if the average size of the pores is the same, if the distribution width of the size is wide, coarse particles will be shed from the rough areas and the separation effect will be significantly deteriorated.

From this point of view, it is necessary to keep the size of the free space constant, but since there is no means to confirm the uniformity of the size for nonwoven fabrics, almost no improvement research has been conducted on this point. The current situation is that this is not the case. However, according to various studies conducted by the present inventors, there is a certain correlation between the lower transmission intensity ratio (lower transmission intensity ratio) and the uniformity of pore size, and as this value approaches 1, the pore size becomes smaller. It was found that the size became uniform and the separation efficiency improved. It was also confirmed that in order to achieve the object of the present invention, it is necessary to suppress the transmission intensity ratio to 1.5 or less, more preferably 1.2 or less. A nonwoven fabric having such characteristics can be obtained by randomly arranging fibers in the vertical and horizontal directions using a method described below.

The properties required of the nonwoven fabric according to the present invention are as described above, but in addition to this, it is desirable that the initial tensile resistance of the fibers constituting the nonwoven fabric be 15 g/denier or more, more preferably 20 g/denier or more. That is, the initial tensile resistance of the fibers is closely related to the anti-compressive force of the nonwoven fabric, that is, the suppression of the decline in filtration performance due to compression, and the tensile resistance is 15
If it is less than g/denier, the nonwoven fabric will have poor compression resistance, and the free space will be crushed by the compression force applied during suction or pressure filtration, resulting in a loss of bulk and a drastic increase in liquid passage resistance, as well as pores. becomes too small and the separation efficiency deteriorates. However, nonwoven fabrics whose initial tensile resistance is 15 g/denier or higher exhibit sufficient compression resistance, are less likely to lose bulk due to free space being crushed, and retain their initial excellent filtration and separation performance. It becomes something that can last.

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'.
The above is preferable, and especially when used as a blood filter, it is 0.05 to 0.5 g/cm3 by pressing etc.
It can be adjusted to the extent. In this case, a nonwoven fabric with poor compression resistance will be crushed by the press treatment and become paper-like and thin, losing its bulk and becoming unpractical. However, as mentioned above, nonwoven fabrics made of fibers with high initial tensile resistance have strong compression resistance. Therefore, the apparent density can be easily controlled while maintaining appropriate bulkiness as a filter.

In addition, since the fibers constituting the nonwoven fabric according to the present invention have the following structure, the performance as a filter is even more excellent.

In other words, it has a sheath-core structure in which the surface is composed of huge crystals with extremely oriented molecules, and the inner layer is amorphous with extremely low orientation, resulting in high modulus and low specific gravity, making it possible to utilize the surface boundary layer of the material. The filtering performance improves because the rate increases for the same denier. In this respect, the constituent fibers are completely different from the nonwoven fabric formed by the heat treatment after the entanglement treatment.

The raw material polymer for the fibers used in the present invention can be any polymer that can be processed into ultrafine fibers that are homogeneous and have little denier unevenness, but aromatic or aliphatic polyesters, polyamides, polyacrylonitrile, etc. When used as a filter, does it adsorb denatured components in blood or capture sticky substances such as denatured proteins? Since it contributes to the cleaning of f1 materials, it is recommended as a preferable method.

The nonwoven fabric of the present invention can also be produced by forming ultrafine fibers using a flash spinning method, super draw method, etc., and then processing them into a nonwoven fabric. However, it is most preferable to use a melt blowing method to produce ultrafine fibers and turn them into a nonwoven fabric. This is a method in which processing is performed continuously. The melt blowing method itself is well known as described in, for example, Japanese Patent Application Laid-open No. 59-26561, but it is not possible to obtain fine denier fibers that meet the above-mentioned required characteristics even if the known method is applied as is. Instead, in carrying out this process, the spinning temperature must be set at 10 ± 5°C higher than the melting point of the raw material resin, and the pulling fluid temperature must also be set at 20 ± 5°C higher than the melting point for elongation. It is desirable that the flow velocity of the traction fluid be set to around 1 Matsuha. For example, when polyethylene terephthalate is used as the raw material resin, the most preferable conditions are that the spinning temperature is about 275°C and the pulling fluid temperature is also about 275°C. The amount of resin discharged per single hole can be arbitrarily determined depending on the target fiber diameter, bulk density, etc.
When obtaining a nonwoven fabric with a fiber diameter of 2 μm or less, the amount is 0.1 to 0.
It is preferable to select from the range of 0.01 g/min, more preferably from 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 intertwining the fibers slightly with each other. The distance between the spinning nozzle and the drum or net is such that the fibers are not tightly intertwined 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. In this case, in order to make the fiber arrangement of the nonwoven fabric as random as possible and make the transmission intensity ratio 1.5 or less, for example, as shown in FIG. The spinning nozzle groups 1, 1. ...
It is effective to arrange them so that they are orthogonal to each other. If the moving speed of the net 2 becomes too fast, the fiber arrangement will be biased in the vertical direction and the random arrangement will be disrupted, so the moving speed should be set appropriately while taking into account the installation angle of the spinning nozzle group, the spinning speed, etc. It is desirable to control the The laminate thus obtained can be made into a nonwoven fabric as it is, but if necessary, the apparent bulk density etc. can be adjusted by lightly pressing it with a heating roller or the like or by embossing it.

Examples will be given below to further clarify the structure and effects of the present invention. The physical properties of the nonwoven fabric and the constituent fibers 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.

The nonwoven fabric is cut to 25 cm x 25 cm, and a frame of 20 cII + x 200111 is drawn along the periphery of the cut piece.

The cut piece was held at one point outside the frame with a clip and hung in a hot air dryer, heat-treated at 160°C for 30 minutes, cooled to room temperature atmosphere (20°C x 65% RH) for 30 minutes, and dried vertically. Length It; cm) and lateral length 1. : cm), the longitudinal shrinkage rate [SHD (T)] and the lateral shrinkage rate [SHD (T)] are calculated using the following formula.

n n-b The nonwoven fabric was cut into 25 cm x 25 cm as a sample, and a microwave molecular orientation meter rMDA-2001A manufactured by Kanzaki Paper Co., Ltd. was used.
Calculate the ratio of the transmitted microwave intensities in the vertical and horizontal directions using the ``type''. Note that one to three samples are measured by stacking them in the circumferential direction, and the thickness effect is determined based on a value corresponding to a basis weight of 80 g/cm'' from a correction curve determined by the minimum double method.

[Example] Example 1 Figure 2 [6 is a polymer discharge pipe, 7 is an orifice hole (0,
15rnmφ), 8 is the traction fluid outlet (lip width 30mm)
0 μm) and 9 indicate the temperature detection end of the traction fluid], 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 traction fluid was From the fluid outlet 3, traction air whose temperature at the detection end is 275°C is supplied at a pressure of 2.2 k.
g/cm2, the melt is blown from the nozzle group arranged as shown in FIG.
The spun fibers were collected on a net moving at a speed of 1 m/min at the cmil position to obtain a nonwoven fabric.

This nonwoven fabric has elasticity at the height of the groove and has a soft feel. This nonwoven fabric was cut into disk shapes with a diameter of 90 mm, and three sheets were stacked on top of each other to obtain a thickness of 40 mm and an effective diameter of 80 m.
It was fixed on a column of m. The column was then heat treated in steam at 130°C for 30 minutes and then dried under reduced pressure.

Using this column, 25℃ using the apparatus shown in Figure 3.
A filter performance evaluation test was conducted. That is, emulsion E containing 1% by weight of 1 μm standard particles (to which 0.2% surfactant was added for particle dispersion) was placed in an emulsion tank 10, and the pump 11 was adjusted to have a feeding pressure of 0.1 kg/cm2. Column 1 of the above emulsion by
2 (in the figure, 13 indicates a pressure gauge, and 14 indicates a pressure controller). The average amount of liquid passing through column 12 for 10 minutes and 60 minutes was calculated from the amount of liquid passing through column 12, and the particle capture rate was calculated from the amount of 1 μm standard particles in the filtrate (15 in the figure).
16 is a filtrate tank, 17 is a stirrer, and 18 is a liquid level gauge).

Example 2 A nonwoven fabric was obtained in the same manner as in Example 1 above, except that polypropylene with a melt index of 13 was used, the spinning temperature was set at 265°C, and the pulling fluid temperature was set at 265°C, and then a filter performance evaluation test was performed in the same manner. I did it.

Comparative Example 1 A nonwoven fabric was obtained in the same manner as in Example 1 except that the traction fluid temperature was 285° C., and then a filter performance evaluation test was conducted in the same manner.

Comparative Example 2 A nonwoven fabric was obtained in the same manner as in Example 1, except that four nozzle groups were arranged perpendicular to the net movement direction and the net movement speed was 5 m/min, and then a filter was obtained in the same manner. A performance evaluation test was conducted.

Comparative Example 3 A nonwoven fabric was obtained in the same manner as in Example 1, except that the single hole discharge amount was 0.05 g for 7 minutes, the pressure of the traction fluid was 0.5 kg/cm2, and the net moving speed was 2 m/min. A filter performance evaluation test was also conducted.

Comparative Example 4 A nonwoven fabric was obtained in the same manner as in Example 2, except that the spinning temperature was 285°C and the pulling fluid temperature was 285°C, and a filter performance evaluation test was conducted in the same manner.

Comparative Example 5 The spinning temperature was 275°C, the single hole discharge rate was 0.05 g/min, the traction fluid temperature was 275°C, the pressure was 2.0 kg/cm2,
A nonwoven fabric was obtained in the same manner as in Example 2, except that the net moving speed was set to 2 m/min, and then a filter performance evaluation test was conducted in the same manner.

Comparative Example 6 Four nozzle groups were arranged perpendicular to the net movement direction, the net movement speed was set to 3 m/min, the spinning temperature was 270°C, and the single hole discharge rate was 0.03 g/min. A nonwoven fabric was obtained in the same manner as in Example 2, except that the traction fluid temperature was set at 270° C., and then a filter performance evaluation test was conducted in the same manner.

The results are summarized in Table 1.

From the results in Table 1, the following can be considered.

Examples 1 and 2: These are examples that satisfy all the specified requirements of the present invention, and in both cases, a high particle capture rate is obtained, there is little decrease in liquid passage rate over time, and the filtration efficiency is sustainable. I know it's excellent.

Comparative Example 1: Although the traction fluid temperature during melt blowing was only increased by 10°C compared to Example 1, the longitudinal and transverse shrinkage rates of the nonwoven fabric were abnormally high, and the initial tensile resistance of the fibers was also extremely high. It's getting lower. As a result, the free space after heat treatment becomes too small, increasing the passage resistance and reducing the liquid passage rate. Moreover, since the initial tensile resistance of the TA fibers is low, the nonwoven fabric has poor compression resistance, and the free space of the nonwoven fabric is crushed by the compressive force during filtration, making it paper-like. The liquid passing rate has decreased to 115 or less.

Comparative Example 2.6 = Comparative example in which the spinning nozzle group during melt blowing was arranged in series and the longitudinal/lateral microwave intensity ratio was over 1.5, and the size of the free space formed in the nonwoven fabric was non-uniform. Since the particles have a wide distribution width, the particle capture rate is very poor.

Comparative Example 3: This is a comparative example in which the traction fluid pressure during melt blowing was set low and the single fiber diameter was made thicker than the specified value, and the free space within the nonwoven fabric was too large, so the particle capture rate was extremely low.

Comparative Example 4: Large longitudinal and transverse shrinkage ratios obtained by setting the spinning temperature and traction fluid temperature higher during melt blowing. This is an example of a nonwoven fabric with a low initial tensile resistance of the A fibers.The free space is narrowed due to shrinkage during heat treatment, so the resistance to liquid passage is high.The initial tensile resistance of the fibers is also low, and the anti-compressive force is poor, so it is difficult to use during filtration. The compression force further narrows the free space, further increasing the resistance to liquid passage, and clogging occurs in a short period of time, making filtration impossible.

Comparative Example 5: This is a comparative example in which the single hole discharge rate during spinning was set to a larger value and the single fiber diameter was made thicker, but at the same time, the unevenness of the fiber diameter was significant and the vertical and horizontal shrinkage rates were also large, making it difficult to capture particles. The rate is very poor.

[Effects of the Invention] The present invention is configured as described above, and by specifying the longitudinal and transverse shrinkage rates and the longitudinal and transverse microwave intensity ratios of the nonwoven fabric, as well as the diameter of the constituent fibers, In particular, it has become possible to provide a nonwoven fabric that has excellent performance as a filter material. This nonwoven fabric has excellent pore characteristics and free space uniformity, so it can be used as a filter for body fluids such as blood, various industrial filters, air purification filters, etc.
It can be widely used as a heat insulator, bacterial culture medium, and sanitary material.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of the main part showing the melt blowing method adopted in the example, FIG. 2 is a sectional view of the main part of the spinning nozzle section, and FIG. 3 is a flow chart showing the filter performance evaluation test method. 1... Spinning nozzle group 2... Net 3... Roller 4... Suction part 7... Orifice hole 8... Traction fluid supply port agent Patent attorney Eizo Asakusa "H"Lt' , 6. Furnace?・−− 12 to”

Claims (3)

[Claims] (1) Made of synthetic fibers with a single fiber diameter of 3 μm or less,
The dry heat shrinkage rate in the longitudinal and transverse directions at 0°C is 15 each.
% or less, and the value given by the transmitted microwave intensity in the longitudinal direction is 1.5% or less, and the value given by the transmitted microwave intensity in the horizontal direction is 1.5% or less. (2) The initial tensile resistance of the single fibers that make up the nonwoven fabric is 15g.
/denier or more. (3) The nonwoven fabric according to claim 1 or 2, wherein the synthetic fiber is obtained by a melt blowing method.