JP7214742B2 - nonwoven fabric - Google Patents

Description

The present invention relates to nonwoven fabrics .

Nonwoven fabrics formed from fibers are known. Fibers include, for example, so-called nanofibers having nano-order diameters of several nanometers or more and less than 1000 nm, and so-called microfibers having micrometer-order diameters of several micrometers or more and less than 1000 micrometers.

As a fiber structure comprising a layer made of fibers such as nonwoven fabric (hereinafter referred to as a fiber layer), for example, in Patent Document 1, it is used as a separator or an insulating material in batteries and the like, and has a high average diameter of 50 nm to 3000 nm. A fibrous structure is described which comprises a fibrous layer of molecular fibers. The fiber layer has an average pore size of 0.01-15 μm, a thickness of 0.0025-0.3 mm, a porosity of 20-90%, a basis weight of 1-90 g/m ² , and a Frazier air permeability of 46 m ³ /min/m. less than ² and a Macmillan number between 2 and 15.

By the way, an electrospinning method is known as a method for producing a nonwoven fabric formed of fibers such as nanofibers. The electrospinning method is also called an electrospinning method or the like, as described in Patent Document 1, and is performed using, for example, an electrospinning apparatus (also called an electrospinning apparatus) having a nozzle, a collector, and a power source. In a general electrospinning apparatus, a voltage is applied between a nozzle and a collector by a power source, for example, the nozzle is negatively charged and the collector is positively charged.

When the raw material solution is ejected from the nozzle while a voltage is applied, a cone-shaped projection called Taylor cone formed from the solution is formed at the opening at the tip of the nozzle. When the applied voltage is gradually increased and the Coulomb force exceeds the surface tension of the solution, the solution is ejected from the tip of the Taylor cone to form a spinning jet. The spinning jet moves to a collector by Coulomb force, is collected as fibers on the collector, and forms a nonwoven fabric composed of fibers on the collector.

Moreover, as a structure other than the nonwoven fabric formed of fibers such as nanofibers, there is a sponge-like structure as described in Patent Document 2. In the sponge-like structure of Patent Document 2, fibers having a number average diameter of 1 nm to 50 μm and a length of 0.2 mm to 30 mm are fixed in a dispersed state. Adhesiveness between fibers is improved by using an adhesive or heat fusion.

WO2014/010753 JP 2007-70792 A

Nonwoven fabrics made of nanofibers and microfibers are actively being developed for use in various fields. Expected uses include, for example, heat insulating materials, sound absorbing materials, and filters, and are also expected to be used as medical nonwoven fabrics.

However, since the fiber structure and fiber layer described in Patent Document 1 are assumed to be used for a separator, the porosity of the fiber layer for good electrolyte absorption and the flow of ions between the anode and the cathode It specifies the thickness to make it easier, the weight to prevent dendrite shorts between the anode and the cathode, and the like. Therefore, it is difficult to develop the above-mentioned uses, such as the lack of sound absorbing performance and heat insulating performance as a sound absorbing material and a heat insulating material. In this respect, the more air is contained, the more the sound absorption performance and the heat insulation performance are improved, and the expansion of applications can be expected.

Also, short fiber pieces may come off from nonwoven fabrics and sponge-like structures formed from fibers. In this regard, if the nonwoven fabric is such that detachment of the fiber pieces is suppressed, contamination of the fiber pieces can be suppressed as a function of the filter, so it can be expected to be used as a filter more widely.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a nonwoven fabric containing a large amount of air and in which detachment of fiber pieces is suppressed.

The nonwoven fabric of the present invention is formed of a plurality of fibers, and the average diameter of the plurality of fibers is within the range of 0.10 µm or more and 5.00 µm or less. The nonwoven fabric has a porosity of at least 90%, an average pore size of 0.5 μm or more and 50 μm or less, a thickness of 2000 μm or more and 100000 μm or less, a breaking elongation of at least 10%, and a fiber is made of a cellulosic polymer, and the cellulosic polymer is cellulose acylate.

Cellulose acylate is preferably any one of cellulose acetate propionate, cellulose triacetate and cellulose diacetate.

According to the present invention, it is possible to obtain a nonwoven fabric containing a large amount of air and from which detachment of fiber pieces is suppressed.

1 is a schematic perspective view of part of a nonwoven fabric that is one embodiment; FIG. 1 is a schematic diagram of a nonwoven fabric manufacturing facility; FIG. 1 is a schematic diagram of a nonwoven fabric manufacturing facility; FIG.

A nonwoven fabric 10 of this embodiment shown in FIG. 1 is formed of a plurality of fibers 11 . The number of fibers 11 may be one. In the nonwoven fabric 10, a plurality of voids 13, which are spatial regions defined by the fibers 11, are formed as portions where air exists. Thus, the nonwoven fabric 10 contains air inside. In order to avoid complication of the drawing, FIG. 1 shows only a portion of one surface (hereinafter referred to as the first surface) 10A side of the nonwoven fabric 10 in the thickness direction Z. As shown in FIG. Therefore, the nonwoven fabric 10 has a structure in which a large number of fibers 11 are further stacked on the lower side of FIG. 1 in the thickness direction Z. As shown in FIG. Also, in FIG. 1, the fiber 11 is drawn with a greatly exaggerated diameter D11 for convenience of explanation, and actually the diameter D1 with respect to the length is much smaller than in FIG.

When the plurality of voids 13 communicate with each other in the thickness direction Z of the nonwoven fabric 10 , they form voids penetrating in the thickness direction Z of the nonwoven fabric 10 . When the nonwoven fabric 10 is used as a filter, for example, the pores function as pores of the filter. Further, some of the voids 13 do not form voids and exist as spatial regions that are not penetrated in the thickness direction Z, for example, are closed by the fibers 11 .

The nonwoven fabric 10 only needs to include the fibers 11, and in addition to the fibers 11, may include other fibers made of different materials. In FIG. 1 , the first surface 10A is drawn along the XY plane, and Z perpendicular to the XY plane is the thickness direction of the nonwoven fabric 10 .

The fiber 11 is formed to have a substantially constant diameter D1. The average value of the diameter D1 (hereinafter referred to as the average diameter) DF (unit: μm) is within the range of 0.10 μm or more and 5.00 μm or less. When the average diameter DF is 0.10 μm or more, the strength of the fiber 11 itself is stronger than when the average diameter DF is less than 0.10 μm. desorption is suppressed. By suppressing detachment of the fiber pieces, the nonwoven fabric 10 exhibits excellent durability. Further, when the nonwoven fabric 10 is used for an air conditioning filter, for example, it is possible to send out clean air free from fiber fragments. When the average diameter DF is 5.00 μm or less, the nonwoven fabric 10 has the same volume ratio of air (hereinafter referred to as porosity) as compared to the case where the average diameter DF is larger than 5.00 μm. Softer. Therefore, when the nonwoven fabric 10 is used for an air conditioning filter, for example, it can withstand changes in the pressure of air to be delivered. In addition, when the average diameter DF is 5.00 μm or less, the porosity of the nonwoven fabric 10 is increased compared to when the average diameter DF is 5.00 μm or less, even if the softness is about the same. When used as a material or heat insulating material, the sound absorbing performance and heat insulating performance are improved, and when used as a filter, the filtration throughput is increased. The average diameter DF is more preferably in the range of 0.15 μm or more and 4.00 μm or less, and further preferably in the range of 0.20 μm or more and 3.00 μm or less.

The average diameter DF can be obtained by measuring the diameter D1 of the fiber 11 at arbitrary 100 points from an image taken with a scanning electron microscope and calculating the average value of the obtained 100 measured values.

Fiber 11 is bent along first surface 10A. Bending along the first surface 10A means bending with a component of the first surface 10A (XY plane), and may further have a component in the thickness direction Z. The fibers 11 are overlapped in the thickness direction Z. As shown in FIG. Among them, many fibers 11 are folded in the thickness direction Z, that is, many layers are overlapped. The fibers 11 are thus formed very long enough to overlap in the thickness direction Z, and the length is in the range of 10 mm or more and 1000 mm or less. The length of the fiber 11 can be obtained by pulling out the fiber 11 with tweezers and measuring it with a ruler. In this example, when the individual spinning jets 69 and fibers 11 flying from the nozzle 27 (see FIGS. 2 and 3) were observed with a high-speed camera in the manufacturing method described later, the length was at least 30 mm. It has been confirmed that there is, that is, 30 mm or more. Thus, the length of fiber 11 can also be measured during the manufacturing process. In addition, the fibers 11 forming the nonwoven fabric 10 may include fibers 11 that do not overlap in the thickness direction Z, but in this example, observation was performed using a scanning electron microscope at a magnification of 100 times. By the way, it has been confirmed that all the fibers 11 observed in one field of view overlap in the thickness direction Z. FIG.

Since the nonwoven fabric 10 is formed so long that the fibers 11 are overlapped in the thickness direction Z, the nonwoven fabric 10 exhibits a high breaking elongation as described later. In addition, if there is an extremely short fiber of, for example, greater than 0 mm and 2 mm or less, such a short fiber may be detached as a fiber piece as it is, or may be cut into a shorter length during use, resulting in a fiber piece. Desorption may occur. However, since the fibers 11 of the nonwoven fabric 10 of the present example are long as described above, the detachment of such fiber pieces can be suppressed.

Furthermore, since the fibers 11 are formed long enough to overlap in the thickness direction Z, when tension is applied to the nonwoven fabric 10 in the direction along the XY plane, the fibers 11 are slightly elongated following the tension. Therefore, for example, when it is used as a heat insulating material, a sound absorbing material, etc., it is easy to construct. Further, when used as an air conditioning filter, for example, it can withstand the pressure of the air to be delivered and its change.

Focusing on one fiber 11 as described above, the fiber 11 overlaps in the thickness direction Z, and a plurality of fibers 11 also overlap each other in the thickness direction Z. As shown in FIG. In this way, the nonwoven fabric 10 has a plurality of fibers 11 overlapping each other, and furthermore, a plurality of fibers 11 overlapping each other, so that the fibers are in a folded state, and a high breaking elongation as described later can be achieved. Definitely manifest.

The plurality of fibers 11 are entangled with each other, and it is preferable that the overlapping portions in the thickness direction Z and/or the portions in contact with each other in the surface direction (in the XY plane) of the nonwoven fabric 10 are not bonded (non-bonded). , which is also done in this example. However, the parts may be partially adhered, and even if they are adhered, the adhesive force is kept small enough to be easily peeled off with a very weak force. When tension is applied to the nonwoven fabric 10, the voids 13 seen from the first surface 10A side change into a shape elongated in the direction in which the tension is applied due to the softness resulting from the aforementioned average diameter DF. In addition to this, although the fibers 11 overlapping in the thickness direction Z are entangled as described above, each of the fibers 11 has a play to allow the fibers 11 to slide relative to each other. In this way, the fibers 11 of the nonwoven fabric 10 are intertwined with each other so as to be slidable, so that the nonwoven fabric 10 is not easily broken even when tension is applied.

In addition, even if the fibers 11 are intertwined or adhered, the adhesive strength is suppressed to a small level. Therefore, the fibers 11 are soft and deformable in a state containing a large amount of air. When used as a material, the degree of freedom of the construction site is large.

The nonwoven fabric 10 has a porosity of 90% or more, that is, at least 90%. The nonwoven fabric 10 having such a very high porosity is fluffy. That is, it contains a large amount of air inside and is soft. Since it contains a large amount of air in this way, it has a wider range of applications than the case where the porosity is less than 90%. For example, it can be used as a sound absorbing material and a heat insulating material because it exhibits superior sound absorbing performance and heat insulating performance compared to a case with a porosity of less than 90%. In addition, compared with the case where the porosity is less than 90%, when it is made into a filter, it exhibits a large filtering performance. Filtration processing performance means throughput per unit time and/or persistence of a state in which clogging is suppressed.

A porosity of 99.8% or less is preferable because higher durability of the nonwoven fabric 10 is ensured. The porosity is more preferably in the range of 90% or more and 99.8% or less, still more preferably in the range of 95% or more and 99.6% or less, and particularly preferably 97% or more and 99.4% or less. Within range. When it is used as a filter, it may be more preferable to heat the nonwoven fabric 10 to bond the fibers 11 to each other and then use it as a filter. For example, in the case of a filter intended for separation by size (for example, a medical filter), it may be preferable to heat the nonwoven fabric 10 to bond the fibers 11 to each other before using it as a filter. This is because bonding the fibers 11 to each other sharpens the hole diameter distribution. On the other hand, in the case of a filter intended to remove foreign matter (for example, a mask or an air-conditioning filter), the fibers 11 do not necessarily have to be bonded together by heating.

The porosity (unit: %) is defined by setting W (unit: g/m ² ) as the weight of the nonwoven fabric 10 , H (unit: mm) as the thickness, and ρ1 (unit: kg/m ³ ) as the specific gravity of the fiber 11 . can be obtained by [1−{(W/1000)/(H/1000)}/ρ1]×100. The weight W is obtained by cutting out a sample of 5 cm×5 cm from the nonwoven fabric 10, measuring the mass of the sample with an electronic balance (manufactured by Mettler Toledo, Inc.), and converting the measured value into 1 m ² . The thickness H is measured by a non-contact laser displacement meter (LK-H025 manufactured by Keyence Corporation) in this example.

The thickness H of the nonwoven fabric 10 is not particularly limited, and can be adjusted according to the deposition amount of the fibers 11 as described later, and may be appropriately set according to the handling situation and/or application. For example, from the viewpoint of handling properties such as workability and durability in a handling situation, it is preferably in the range of, for example, 100 μm or more and 100000 μm or less. In addition, when used as a sound absorbing material or a heat insulating material, it may be thick (for example, within the range of 2000 μm or more and 100000 μm or less) for construction as a single sheet, or thin for construction in a stacked state (for example, within a range of 200 μm or more and 1000 μm or less). In this example, the thickness is set to 4000 μm. Although the nonwoven fabric 10 has a large degree of freedom in thickness as described above, it contains a large amount of air and is soft, so it has a wide range of uses.

Here, the average pore diameter of the nonwoven fabric 10 in which a plurality of voids 13 are formed is DA (unit: μm). The average pore diameter DA is within the range of 0.5 μm or more and 50 μm or less. Since the pore size is uniform in this range and the porosity is high as described above, when used as a filter, for example, high-precision filtration is efficiently performed and clogging (blockage) is unlikely. The average pore diameter DA is more preferably in the range of 2 µm or more and 30 µm or less, and further preferably in the range of 4 µm or more and 20 µm or less.

The average pore diameter DA can be obtained by the following method. First, a 5 cm square (5 cm×5 cm) is cut out from the nonwoven fabric 10 to obtain a sample. After immersing this sample in GALWICK (manufactured by POROUS MATERIAL) having a surface tension of 15.3 mN/m, the average pore diameter DA was measured by the bubble point method using a perm porometer (manufactured by POROUS MATERIAL). can get.

The nonwoven fabric 10 has an elongation at break of at least 10%. Since the elongation at break is as high as 10% or more in this way, it can be expected to be used in applications requiring resistance to tearing. Specifically, for example, when the nonwoven fabric 10 is used for an air conditioning filter, air pressure (wind pressure) is applied to the first surface 10A or the other second surface (not shown), It exhibits durability against the application of this wind pressure.

The breaking elongation is more preferably 15% or more, further preferably 20% or more. Although the upper limit of the elongation at break is not particularly limited, according to the manufacturing method described later, 94.2% is obtained as the maximum value of the elongation at break. Therefore, the elongation at break is in the range of 10% or more and 94.2% or less, more preferably in the range of 15% or more and 94.2% or less, and still more preferably in the range of 20% or more and 94.2% or less. You can say inside.

The breaking elongation (unit is %) can be obtained by the following method. A sample is prepared by cutting the nonwoven fabric 10 into a rectangle with a width of 20 mm and a length of 70 mm. Three samples are produced. In a state where the length of the sample between the clips of the tensile tester (Autograph AGS-J manufactured by Shimadzu Corporation) is 50 mm, the sample is sandwiched by 10 mm between the upper clip and the lower clip, and the tensile speed is 10 mm / min. A tensile test is performed on each of the three samples to determine the breaking elongation of each sample. The breaking elongation of the nonwoven fabric 10 is determined by averaging the breaking elongations of the three samples.

The fiber 11 is made of resin (polymer). A polymer that can be dissolved in a solvent to form a solution is used as the polymer. Further, the polymer is preferably soluble in a mixed solvent that is a mixture containing alcohols. More preferably, the polymer is a thermoplastic resin such as polymethyl methacrylate (hereinafter referred to as PMMA), cellulosic polymer, polyester, polyurethane, polyolefin, elastomer, and the like. In this example, for example, a cellulosic polymer 15 (see FIG. 2) is used.

The cellulosic polymer 15 is preferably cellulose acylate. Cellulose acylate is a cellulose ester in which some or all of the hydrogen atoms constituting the hydroxy groups of cellulose are substituted with acyl groups. Cellulose acylate is preferably cellulose acetate propionate (CAP), cellulose triacetate (TAC), or cellulose diacetate (DAC).

As described above, according to the above configuration, a large amount of air is included, and excellent heat insulation performance is obtained. Therefore, it can be used, for example, as heat-insulating building materials for floors, walls, and ceilings, heat-insulating members for vehicles, and the like. Furthermore, according to the above configuration, the thermal conductivity is lower than that of the conventional heat insulating material, and a sufficient heat insulating effect can be exhibited even in a narrow space. Therefore, it can be used as a heat insulating material used inside electronic equipment, vehicle-mounted equipment, and industrial equipment. Since the fiber diameter is small, the fiber is bulky, and it has excellent sound absorbing performance, it is suitable as a sound absorbing material for houses, vehicles, and electric appliances. In addition, according to the above configuration, sufficient air permeability can be obtained, so as described in Japanese Patent Application Laid-Open No. 2017-82346, by laminating on a porous sound absorbing material (felt, glass wool, urethane foam, etc.), sound absorbing Better performance.

Further, according to the above configuration, it can be suitably used as a filter for separating or removing a target substance from a mixture of solid and liquid (solid-liquid mixture). Among such filters, filters that can be particularly preferably used are those for food (including beverages), medical use, ultrapure water, and high-purity chemical liquids, which are concerned about contamination of fiber pieces. is a filter for Specific examples include filters for removing fine particles and/or microorganisms from beverages, filters for pretreatment of industrial pure water, and filters for inspection that collect specific cells from bodily fluids such as blood and saliva. . Examples of test filters include blood sugar test, urine sugar test, lifestyle disease test, gene test, tumor marker test, blood test, and the like.

The nonwoven fabric 10 can be manufactured by the nonwoven fabric manufacturing equipment 20 shown in FIG. 2, for example. The nonwoven fabric production facility 20 is for producing the nonwoven fabric 10 using an electrospinning method. The nonwoven fabric manufacturing facility 20 includes a solution preparation section 21 and a nonwoven fabric manufacturing device 22 . The details of the nonwoven fabric manufacturing apparatus 22 are shown in another drawing, and only a part of the nonwoven fabric manufacturing apparatus 22 is shown in FIG.

The solution preparation section 21 prepares the solution 25 for forming the fiber 11 . The solution preparation unit 21 prepares the solution 25 by dissolving the cellulose-based polymer 15 as the fiber material that will become the fibers 11 in the solvent 26 . This solution 25 is discharged from each of nozzles 27a to 27c, which will be described later, to form the fibers 11 on the support . In the following description, the nozzles 27a, 27b, and 27c are referred to as nozzles 27 when they are not distinguished from each other.

Solvent 26 is a mixture of at least two compounds, ie, two or more compounds. Specifically, the solvent 26 is a mixture of a first compound 26a that is different from alcohol and a second compound 26b that is alcohol. However, in addition to the first compound 26a and the second compound 26b, other compounds different from the first compound 26a and the second compound 26b are used as the third compound, the fourth compound, . may comprise the solvent 26.

The first compound 26a is used as a so-called good solvent for dissolving the cellulosic polymer 15, and the second compound 26b is for adjusting the balance between the evaporation rate of the solution 25 discharged from the nozzle 27 and the surface tension. be. Solvent 26 contains alcohol as second compound 26b in a mass proportion of at least 10%. The mass ratio of alcohol in the solvent 26 is preferably in the range of 10% or more and 50% or less. tend to be higher. The mass ratio of alcohol in the solvent 26 is more preferably in the range of 20% or more and 50% or less, and more preferably in the range of 30% or more and 50% or less.

Alcohol is not particularly limited as long as it is compatible with the first compound 26a, and methanol (MeOH), ethanol (EtOH), isopropanol, butanol, benzyl alcohol, or the like can be used. Among these, either methanol or ethanol is more preferable.

The first compound 26a in the solvent 26 preferably has the same or a higher mass proportion than the second compound 26b, and this is also the case in this example. The mass ratio of the first compound 26a is at most 90%, that is, 90% or less, preferably in the range of 50% or more and 90% or less, and preferably in the range of 50% or more and 80% or less. More preferably, it is in the range of 50% or more and 70% or less.

As described above, a solvent obtained by adding a compound different from the first compound 26a and the second compound 26b to the first compound 26a and the second compound 26b is used, and another compound different from the first compound 26a and the second compound 26b is used. When the compound is a good solvent for the cellulosic polymer 15, it is preferable that the mass ratio of the first compound 26a is the sum of the mass ratios of the other compounds and the first compound 26a. That is, the sum of the mass ratios of the other compounds and the first compound 26a is at most 90%, that is, 90% or less, preferably in the range of 50% or more and 90% or less, and 50% or more and 80%. % or less, more preferably 50% or more and 70% or less. Thus, it is preferable that the mass ratio of the good solvent component in the solvent 26 is the same as or higher than that of the second compound 26b. On the other hand, when the above other compound is a poor solvent for the cellulose-based polymer 15, the mass ratio of the first compound 26a in the solvent 26 is as described above.

The first compound 26a is preferably an organic compound, ie an organic solvent. More preferably, the first compound 26a is a liquid with a lower boiling point than the second compound 26b.

When cellulose acylate is used as the cellulosic polymer 15, the first compound 26a is acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl formate, ethyl formate, hexane, cyclohexane, dichloromethane ( DCM), chloroform, carbon tetrachloride, benzene, toluene, xylene, dimethylformamide, N-methylpyrrolidone, diethyl ether, dioxane, tetrahydrofuran, or 1-methoxy-2-propanol and the like can be used. Among these, any one of dichloromethane, chloroform, and acetone is more preferable. A plurality of compounds may be selected from these compounds, one of which may be the first compound 26a and the others may be the third compound, the fourth compound, . . .

When PMMA is used as the fiber material, methanol, dichloromethane, chloroform, toluene, acetone, tetrahydrofuran, or the like can be used as the first compound 26a. Among these, any one of dichloromethane, chloroform, and acetone is more preferable. A plurality of compounds may be selected from these compounds, one of which may be the first compound 26a and the others may be the third compound, the fourth compound, . . .

The concentration C of the polymer (cellulosic polymer 15 in this example) in the solution 25 is preferably adjusted based on the type and/or molecular weight of the polymer to be as low as possible while still allowing the electrospinning process to form fibers. For example, when the cellulose-based polymer 15 is used as the polymer, the concentration C is preferably in the range of 1% to 40%, more preferably in the range of 2% to 30%, and 3%. More preferably, it is in the range of 20% or less.

The solution preparation unit 21 includes a temperature control mechanism (not shown) and a stirring mechanism (not shown) for dissolving the cellulosic polymer 15 in the first compound 26a and the second compound 26b. A temperature control mechanism regulates the temperature of these mixtures to promote dissolution. A temperature control mechanism does not have to be used when the material is reliably melted without temperature control. In this example, the dissolution is accelerated by heating to 35°C, for example. However, temperature adjustment is not limited to heating, and cooling may be performed in addition to or instead of heating, or the temperature may be maintained at room temperature (25° C.). Further, the stirring mechanism promotes dissolution by stirring the mixture. The stirring mechanism may not be used if the solution is reliably dissolved without stirring.

In this example, the solvent 26 in which the first compound 26a and the second compound 26b are mixed is guided to the solution preparing section 21, but the present invention is not limited to this aspect. For example, the first compound 26a, which is a good solvent, and the cellulosic polymer 15 may first be introduced to the solution preparation section 21, and after dissolution, the second compound 26b may be introduced to the solution preparation section 21.

In this example, the nonwoven fabric manufacturing facility 20 includes pipes 33a to 33c that connect the solution preparation unit 21 and the nonwoven fabric manufacturing apparatus 22, and the nonwoven fabric manufacturing apparatus 22 has nozzles 27a to 27c arranged in a state separated from each other. . The pipes 33a-33c are for guiding the solution 25. As shown in FIG. A pipe 33a connects the solution preparation unit 21 and the nozzle 27a, a pipe 33b connects the solution preparation unit 21 and the nozzle 27b, and a pipe 33c connects the solution preparation unit 21 and the nozzle 27c. Thereby, the solution 25 is discharged from each of the nozzles 27a to 27c. The solutions 25 exiting the nozzles 27a-27c form the fibers 11 respectively. In the following description, the pipes 33a, 33b, and 33c are referred to as pipes 33 when not distinguished from each other.

In this example, an elongate support 28 is used for collecting and depositing the fibers 11 and supporting the nonwoven fabric 10, and the support 28 is moved longitudinally. In the following description, collection and deposition are collectively referred to as "accumulation". Although the details of the support 28 will be described later with reference to other drawings, the horizontal direction in FIG. 2 is the width direction of the support 28, and the depth direction of FIG. The nozzles 27a to 27c are arranged side by side in the width direction of the support 28 in this order. Although the number of nozzles 27 is three in this example, the number of nozzles 27 is not limited to this. A pump 38 for sending the solution 25 to the nozzle 27 is provided in each of the pipes 33a to 33c. By changing the number of rotations of the pump 38, the discharge amount of the solution 25 discharged from the nozzles 27a to 27c is adjusted.

The nozzles 27a-27c are held by a holding member 41. As shown in FIG. A nozzle unit 42 of the nonwoven fabric manufacturing apparatus 22 is composed of the holding member 41 and the nozzle 27 .

The nonwoven fabric manufacturing apparatus 22 will be described with reference to FIG. FIG. 3 shows a view from the nozzle 27a side of FIG. 2, and only the nozzle 27a is shown. The nonwoven fabric manufacturing apparatus 22 includes a chamber 45, the nozzle unit 42 described above, a stacking section 50, a power source 51, and the like.

The chamber 45 houses, for example, the nozzle unit 42 and part of the stacking section 50 . The chamber 45 is configured to be hermetically sealed, thereby preventing solvent gas from leaking to the outside. The solvent gas is the vaporized solvent 26 of the solution 25 .

The chamber 45 has a humidity adjustment mechanism 45a that adjusts the internal relative humidity (hereinafter simply referred to as humidity). The humidity adjustment mechanism 45a sends gas (for example, air) with adjusted humidity to the chamber 45, collects the atmosphere in the chamber 45, adjusts the humidity again, and then sends it to the chamber 45. The humidity inside the chamber 45 is thus adjusted. This humidity adjustment is performed to adjust the humidity of the spinning space, which is the space between the nozzle 27 and the support 28 . That is, the chamber 45 also has the function of separating the spinning space from the outside space and adjusting the humidity of the spinning space. However, the adjustment of the humidity in the spinning space is not limited to the method of this example using the chamber 45, and may not be performed. For example, within chamber 45 , the humidity of the spinning space may be regulated by a chamber defining the spinning space within chamber 45 .

The humidity in the spinning space is preferably 10% or more and 30% or less. It should be noted that the humidity may vary within this range during the production of the nonwoven fabric 10 . The humidity in the spinning space is more preferably in the range of 15% or more and 25% or less.

The nozzle unit 42 is arranged in the upper part inside the chamber 45 . The tip of the nozzle 27 from which the solution 25 exits is directed toward a collector 52 located below the nozzle 27 in FIG. When the solution 25 exits from an opening formed at the tip of the nozzle 27 (hereinafter referred to as tip opening), the solution 25 forms a generally conical Taylor cone 53 at the tip opening.

The stacking section 50 is arranged below the nozzle 27 . The stacking section 50 has a collector 52 , a collector rotation section 56 , a support supply section 57 , and a support winding section 58 . The collector 52 attracts the solution 25 discharged from the nozzle 27 and collects the formed fibers 11 as the nonwoven fabric 10. In this embodiment, the fibers are collected on a support 28 which will be described later.

The collector 52 is composed of an endless belt that is formed in an annular shape from a strip of metal. The collector 52 may be made of a material that is charged when a voltage is applied by the power source 51, such as stainless steel. The collector rotating section 56 is composed of a pair of rollers 61 and 62, a motor 60, and the like. The collector 52 is horizontally stretched over a pair of rollers 61 and 62 . A motor 60 arranged outside the chamber 45 is connected to the shaft of one roller 61 to rotate the roller 61 at a predetermined speed. This rotation causes the collector 52 to move and circulate between the rollers 61 and 62 . In this embodiment, the moving speed of the collector 52 is set to 0.2 m/min, for example, but it is not limited to this.

The collector 52 is supplied with a band-shaped support 28 made of, for example, an aluminum sheet by a support supply section 57 . The support 28 is for accumulating the fibers 11 to obtain the nonwoven fabric 10 . The support supply section 57 has a delivery shaft 57a. A support roll 63 is attached to the delivery shaft 57a. The support roll 63 is configured by winding the support 28 around a winding core 64 . The support winding section 58 has a winding shaft 67 . The winding shaft 67 is rotated by a motor (not shown) to wind the support 28 on which the nonwoven fabric 10 is formed on a set winding core 68 . Thus, the nonwoven fabric manufacturing apparatus 22 has a function of forming the fibers 11 and a function of forming the nonwoven fabric 10 . Alternatively, the support 28 may be placed on the collector 52 and moved by the movement of the collector 52 .

The nonwoven fabric 10 may be formed by directly stacking the fibers 11 on the collector 52, but depending on the material forming the collector 52 or the surface condition of the collector 52, the nonwoven fabric 10 sticks and is difficult to peel off. Sometimes. For this reason, it is preferable to guide the support 28 to which the nonwoven fabric 10 is difficult to stick onto the collector 52 and collect the fibers 11 on this support 28 as in this embodiment.

The power supply 51 applies a voltage to the nozzle 27 and the collector 52, thereby charging the nozzle 27 to a first polarity and charging the collector 52 to a second polarity opposite to the first polarity. Department. By passing through the charged nozzle 27, the solution 25 is charged and exits the nozzle 27 in a charged state. In this example, the holding member 41 and the nozzle 27 are electrically connected, and by connecting the power source 51 to the holding member 41 , a voltage is applied to the nozzle 27 through the holding member 41 . is not limited to this. For example, a voltage may be applied to each nozzle 27 by connecting a power supply 51 to each nozzle 27 . In this embodiment, the nozzle 27 is positively (+) charged and the collector 52 is negatively (-) charged, but the polarities of the nozzle 27 and the collector 52 may be reversed. It should be noted that the collector 52 side may be grounded to set the potential to zero. Due to the electrification, the solution 25 is ejected from the Taylor cone 53 toward the collector 52 as a spinning jet 69 . In this example, the solution 25 is charged by applying voltage to the nozzle 27 , but the solution 25 may be charged in the pipe 33 and the charged solution 25 may be guided to the nozzle 27 .

The distance L between the nozzle 27 and the collector 52 varies depending on the types of the cellulose polymer 15 and the solvent 26, the mass ratio of the solvent 26 in the solution 25, etc., but is preferably in the range of 30 mm or more and 500 mm or less. 150 mm. In addition, it is preferable to set the distance L as small as possible within a range in which the solvent 26 is sufficiently evaporated from the spinning jet 69 and the fiber 11 from the viewpoint of forming the fiber 11 longer.

A voltage (applied voltage) applied to the nozzle 27 and the collector 52 is preferably 5 kV or more and 200 kV or less. From the viewpoint of making the fiber 11 thinner, the applied voltage is preferably as high as possible within this range. In this embodiment, it is 40 kV.

When the evaporation rate of the solvent 26 is V (unit: ml/s, milliliter/second), the evaporation rate V and the average diameter DF of the fibers 11 formed on the support 28 are 1≤V/DF≤ 10 is preferred. V/DF can be set within the above range by adjusting at least one of the evaporation rate V and the average diameter DF.

The evaporation rate V is obtained by the following formula (1). Concentration C is the concentration of the solution 25 (unit: %). The concentration C is calculated by {M1/(M1+M2)}×100, where M1 is the mass of the polymer (cellulose polymer 15 in this example) and M2 is the mass of the solvent 26 . Q is the discharge amount of the solution 25 from the nozzle 27 (volume discharged per hour, unit: ml/h, milliliter/hour). ρ2 is the density of the solution 25 (unit: g/ml). Therefore, the evaporation speed V can be adjusted by increasing or decreasing at least one of the concentration C, the ejection amount Q, and the density ρ2. The evaporation rate V can also be adjusted by adjusting the formulation of the solvent 26 (for example, the types and mass ratios of the first compound 26a and the second compound 26b). Also, the average diameter DF can be adjusted by increasing or decreasing at least one of the ejection amount Q, the density C, the applied voltage described later, and the distance L from the nozzle 27 to the support 28 . In this example, the temperature of the spinning space, which is the space between the nozzle 27 and the support 28, is set to approximately 25°C. there is
V={(1−0.01C)×Q×10 ⁻³ }/(3600×ρ2) (1)

The operation of the nonwoven fabric manufacturing facility 20 will be described. A voltage is applied by a power supply 51 to the nozzle 27 and the circulating collector 52 . Thereby, the nozzle 27 is positively charged as the first polarity, and the collector 52 is negatively charged as the second polarity. The nozzle 27 is continuously supplied with the solution 25 from the solution preparation section 21 , and the support 28 is continuously supplied onto the moving collector 52 . The solution 25 is positively charged with the first polarity by passing through each of the nozzles 27a to 27c, and exits from each tip opening of the nozzles 27a to 27c in the charged state.

The collector 52 attracts the solution 25 exiting the tip opening while being charged to the first polarity. As a result, a Taylor cone 53 is formed at the tip opening, and the spinning jet 69 exits from this Taylor cone 53 toward the collector 52 . The spinning jet 69, which is charged to the first polarity, splits into smaller diameters by repulsion due to its own electric charge while heading toward the collector 52, and expands to smaller diameters while drawing a helical trajectory. , the fibers 11 are collected on the support 28 . Since the fibers 11 are deposited in a very short time, they will be collected as a nonwoven fabric 10 . The thickness of the nonwoven fabric 10 can be adjusted by increasing or decreasing the deposition amount. The amount of deposition can be increased or decreased by adjusting the moving speed of the support 28, for example.

In this example, the solution 25 is ejected from the nozzle 27 to be ejected toward the support 28, but the solution 25 may be ejected by a method that does not use the nozzle. For example, there are an electro-bubble spinning method, a wire fixed electrode method, and the like. The electro-bubble spinning method is a method in which a compressed gas is supplied to the solution 25 and a voltage is applied to the generated bubbles to cause the solution 25 to fly linearly from the surface of the bubbles to form the fibers 11. The method is introduced. The wire-fixed electrode method is a method of forming the fiber 11 by applying a solution to a wire whose both ends are fixed and applying a voltage between the wire and a collector. A fiber forming apparatus using this wire-fixed electrode method is sold, for example, by Elmarco.

If the evaporation rate of the solvent in the solution discharged from the nozzle 27 is excessively high beyond the balance with the surface tension, the solution will not reach the support 28 as the fibers 11 and will scatter around. On the other hand, if the surface tension of the solution exceeds the balance with the evaporation rate of the solvent and is too large, the solution will form droplets and will be mixed into the nonwoven fabric as beads (microspheres). However, in the present embodiment, the solvent 26 contains alcohol, which is the second compound 26b, at a mass ratio of 10% or more, so that the solution 25 discharged from the nozzle 27 has a balance between the evaporation rate and the surface tension of the solution 25. is adjusted to the support 28 . Therefore, the spinning jet 69 splits and becomes thinner while drawing a helical trajectory, forming longer fibers 11 having an average diameter DF within the range of 0.10 μm or more and 5.00 μm or less, Deposit on support 28 . For this reason, the nonwoven fabric 10 includes fibers 11 overlapping in the thickness direction Z, has a porosity of at least 90%, an average pore diameter DA within the range of 0.5 μm or more and 50 μm or less, and has a breaking elongation of at least 10%. becomes. The above effect is particularly remarkable when the fiber material is any one of the cellulosic polymer 15, especially CAP, TAC, and DAC.

Since the mass ratio of the first compound 26a is the same as that of the second compound 26b or higher than that of the second compound 26b, the solidification of the cellulosic polymer 15 at the tip of the nozzle 27 is ensured for a longer period of time. The nonwoven fabric 10 having the above structure is formed more reliably on the support 28 while being held down.

Since the evaporation rate of a liquid is generally higher for a substance with a lower boiling point, a liquid with a boiling point lower than that of the second compound 26b is used as the first compound 26a in this embodiment. Since the first compound 26a is a liquid with a boiling point lower than that of the second compound 26b, the solvent 26 in the solution 25 discharged from the nozzle 27 evaporates rapidly while maintaining the surface tension and balance. Therefore, on the support 28; The fibers 11 are not adhered to each other, or even if they are adhered to each other, the adhesive force is suppressed to be extremely weak. As a result, the nonwoven fabric 10 has a porosity of at least 90% and an average pore diameter DA within the range of 0.5 μm to 50 μm more reliably.

When the concentration C of the cellulosic polymer 15 in the solution 25 is 40% or less, solidification of the cellulosic polymer 15 at the tip of the nozzle 27 can be reliably suppressed for a longer period of time. Further, since the concentration C is 1% or more, coupled with the fact that the second compound 26b is used as the solvent 26, the speed at which the solvent 26 evaporates from the solution 25 discharged from the nozzle 27 is adjusted to an appropriate range, and the average The fiber 11 having a diameter DF within the range of 0.10 μm or more and 5.00 μm or less is formed longer.

Since the spinning space is humidity-controlled, the moisture content of the fibers 11 on the support 28 is adjusted to 3.0% or more and 10% or less. As a result, the nonwoven fabric 10 is more reliably manufactured with a porosity of 90% or more, and deformation of the moisture-absorbed fibers 11 due to their own weight is suppressed, and the porosity is easily maintained at a high level.

The nonwoven fabric 10 is sent to the support take-up section 58 together with the support 28 . The nonwoven fabric 10 is wound around the winding core 68 while overlapping the support 28 . After the winding core 68 is removed from the winding shaft 67 , the nonwoven fabric 10 is separated from the support 28 . The nonwoven fabric 10 obtained in this manner is long, and may be subsequently cut to a desired size, for example.

In this example, a circulating belt is used as the collector 52, but the collector is not limited to the belt. For example, the collector may be a fixed flat plate or a cylindrical rotating body. Even in the case of flat or cylindrical collectors, it is preferable to use a support 28 so that the nonwoven fabric 10 can be easily separated from the collector. When a rotating body is used, a cylindrical sheet material made of fibers is formed on the peripheral surface of the rotating body. Just cut it.

In the above example, the nozzle 27 is arranged with the tip opening facing downward, and the collector 52 is arranged below the nozzle 27, thereby discharging the solution 25 downward. However, the direction of ejection of the solution 25 is not limited to this example. For example, the solution 25 may be discharged upward by arranging the nozzle 27 with the tip opening facing upward and by arranging the collector 52 above the nozzle 27 .

[Example 1] to [Example 10]
Using the nonwoven fabric manufacturing equipment 20, the nonwoven fabrics 10 were manufactured under the conditions shown in Table 1, and designated as Examples 1 to 10. The thickness of the manufactured nonwoven fabric 10 is 4000 μm as described above. The fiber materials used are listed in Table 1 in the "Fiber Material" column. The applied voltage was 40 V and the distance L was 150 mm.

The solvent 26 is a mixture of two compounds, a first compound 26a and a second compound 26b. Table 1 shows the first compound 26a and the second compound 26b. In Table 1, "DMC" is dichloromethane, "MeOH" is methanol, and "EtOH" is ethanol. The "mass ratio of the first compound and the second compound" column in Table 1 indicates (mass of the first compound): (mass of the second compound), for example, "87:13" means ( mass of the first compound):(mass of the second compound) = 87:13. "Concentration C" in Table 1 is a percentage obtained by the formula (C1/C26)×100, where C1 is the mass of the fiber material and C26 is the mass of the solvent 26.

For the nonwoven fabric 10 obtained in each example, the elongation at break was determined and the detachment of the fiber pieces was evaluated. The elongation at break was determined by the method described above. Table 1 shows the determined elongation at break. Detachment of the fiber piece was evaluated by the following method.

A circular sample with a diameter of 47 mm was cut out from the obtained nonwoven fabric 10 . This sample is attached to a stainless steel line holder (KS-47, manufactured by Advantech Toyo Co., Ltd.), a membrane filter (A080P047A, manufactured by Advantech Toyo Co., Ltd.) is set on the downstream side, and 1 L (liter) of ultrapure water is allowed to pass through. rice field. The state of the fiber piece remaining on the membrane filter after passing water was visually observed, and the detachment evaluation of the fiber piece was made according to the following criteria. A and B pass, C fails. Evaluation results are shown in Table 1.

A; No fiber piece was observed.
B: Fiber pieces were observed, but the amount was extremely small and at a level that poses no practical problem.
C; A large amount of fiber pieces were observed.

Furthermore, using the nonwoven fabric 10 obtained in Example 1, genetic testing was performed. Specifically, after filtering human whole blood with the nonwoven fabric 10 obtained in Example 1, white blood cells remaining on the nonwoven fabric 10 are used, and paragraphs [0057] to [0061] of Japanese Patent No. 4058508 are used. Genetic testing was performed according to the method described in . As a result, results similar to those of the example described in Japanese Patent No. 4058508 were obtained.

[Comparative Example 1] to [Comparative Example 2]
Nonwoven fabrics were produced under the conditions shown in Table 1 and designated as Comparative Examples 1 and 2. The applied voltage was 40 V and the distance L was 150 mm.

Detachment of the fiber piece was evaluated by determining the breaking elongation by the same method and criteria as in the example. Evaluation results are shown in Table 1.

REFERENCE SIGNS LIST 10 nonwoven fabric 10A first surface 11 fiber 13 void 15 cellulosic polymer 20 nonwoven fabric production facility 21 solution preparation unit 22 nonwoven fabric production device 25 solution 26 solvent 26a first compound 26b second compound 27a-27c nozzle 28 support 33a-33c pipe 38 Pump 41 Holding member 42 Nozzle unit 45 Chamber 45a Humidity adjustment mechanism 50 Stacking unit 51 Power source 52 Collector 53 Tailor cone 56 Collector rotating unit 57 Support supplying unit 57a Delivery shaft 58 Support winding unit 60 Motor 61, 62 Roller 63 Support Roll 64 Winding core 67 Winding shaft 68 Winding core 69 Spinning jet D1 Diameter Z Thickness direction L Distance

Claims (2)

In a nonwoven fabric formed of a plurality of fibers,
The average diameter of the plurality of fibers is in the range of 0.10 μm or more and 5.00 μm or less,
has a porosity of at least 90%;
The average pore size is in the range of 0.5 μm or more and 50 μm or less,
The thickness is in the range of 2000 μm or more and 100000 μm or less,
an elongation at break of at least 10% ;
The fibers are made of a cellulosic polymer,
The nonwoven fabric , wherein the cellulosic polymer is cellulose acylate . 2. The nonwoven fabric according to claim 1, wherein the cellulose acylate is any one of cellulose acetate propionate, cellulose triacetate and cellulose diacetate.

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