JPWO2020050311A1 - Non-woven fabric and non-woven fabric manufacturing method - Google Patents

Abstract

Provided are a non-woven fabric and a non-woven fabric manufacturing method in which a large amount of air is contained and desorption of fiber pieces is suppressed.
The non-woven fabric (10) is formed of a plurality of fibers (11). The average diameter of the plurality of fibers (11) is within the range of 0.10 μm or more and 5.00 μm or less. The non-woven fabric (10) has a porosity of at least 90%. The non-woven fabric (10) has an average pore diameter in the range of 0.5 μm or more and 50 μm or less. The non-woven fabric (10) has a breaking elongation of at least 10%.

Description

The present invention relates to a non-woven fabric and a method for producing a non-woven fabric.

Nonwoven fabrics made of fibers are known. Examples of the fiber include so-called nanofibers having a diameter of several nm or more and less than 1000 nm, and so-called micron fibers having a diameter of several μm or more and less than 1000 μm.

As a fiber structure including a layer made of fibers such as a non-woven 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 a battery or the like, and has a high average diameter of 50 nm to 3000 nm. A fiber structure comprising a fiber layer made of molecular fibers is described. The fiber layer has an average pore diameter of 0.01 to 15 μm, a thickness of 0.0025 to 0.3 mm, a porosity of 20 to 90%, a weighing of 1 to 90 g / m ² , and a Frazier air permeability of 46 m ³ / min / m. ^{It is} less than 2 and the number of McMillan is 2 to 15.

By the way, an electric field spinning method is known as a method for producing a non-woven fabric made of fibers such as nanofibers. As described in Patent Document 1, the electrospinning method is also called an electrospinning method or the like, and is performed using, for example, an electrospinning device (also called an electrospinning device) having a nozzle, a collector, and a power source. In a general electric field spinning device, 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 a solution as a raw material is discharged from a nozzle while a voltage is applied, a conical protrusion composed of a solution called a Taylor cone is formed in 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 pops out from the tip of the Taylor cone to form a spinning jet. The spinning jet moves to the collector by Coulomb force and is collected as fibers on the collector, and a non-woven fabric composed of fibers is formed on the collector.

Further, as a structure other than the non-woven 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 immobilized in a dispersed state. Then, the adhesiveness between the fibers is improved by using an adhesive or heat-sealing.

International Publication No. 2014/010753 JP-A-2007-70792

Nonwoven fabrics made of nanofibers and micron fibers are being actively developed for use in various fields. Expected applications include, for example, heat insulating materials, sound absorbing materials, filters, etc., and are also expected to be used as medical non-woven fabrics.

However, since the fiber structure and the fiber layer described in Patent Document 1 are premised on the use as a separator, the porosity of the fiber layer for satisfactorily absorbing the electrolyte and the flow of ions between the anode and the cathode. The thickness for facilitating and the weighing for preventing dendried short circuit between the anode and the cathode are specified. Therefore, for example, as a sound absorbing material and a heat insulating material, the sound absorbing performance and the heat insulating performance are insufficient, and it is difficult to develop them into the above-mentioned applications. In this respect, the more air is contained, the better the sound absorption performance and the heat insulation performance, and the wider the application can be expected.

In addition, short fiber pieces may be detached from the non-woven fabric and sponge-like structure formed of fibers. In this respect, a non-woven fabric in which desorption of fiber pieces is suppressed can be expected to be widely used as a filter because, for example, contamination of fiber pieces is suppressed as a filter performance.

Therefore, an object of the present invention is to provide a non-woven fabric containing a large amount of air and suppressing desorption of fiber pieces, and a non-woven fabric manufacturing method for manufacturing the non-woven fabric.

The non-woven fabric of the present invention is formed of a plurality of fibers, and the average diameter of the plurality of fibers is in the range of 0.10 μm or more and 5.00 μm or less. The non-woven fabric has a porosity of at least 90%, an average pore diameter in the range of 0.5 μm or more and 50 μm or less, and a breaking elongation of at least 10%.

The fiber is preferably formed of a cellulosic polymer, and the cellulosic polymer is preferably a cellulosic acylate. The cellulose acylate is preferably either cellulose acetate propionate, cellulose triacetate, or cellulose diacetate.

In the method for producing a non-woven fabric of the present invention, a voltage is applied between a solution in which a fiber material is dissolved in a solvent and a collector, and the solution is attracted to the collector to produce a non-woven fabric formed of fibers. The solvent is a mixture containing alcohol in a mass ratio of at least 10%.

The alcohol is preferably either methanol or ethanol.

The solvent preferably contains a liquid having a boiling point lower than that of alcohol, and the solvent more preferably contains a liquid having a boiling point lower than that of alcohol in the same mass ratio as alcohol or in a mass ratio higher than that of alcohol. The liquid is preferably any of dichloromethane, chloroform and acetone.

The fiber material is preferably a cellulosic polymer, and the cellulosic polymer is preferably a cellulosic acylate. The cellulose acylate is preferably either cellulose acetate propionate, cellulose triacetate, or cellulose diacetate.

According to the present invention, a non-woven fabric containing a large amount of air and in which desorption of fiber pieces is suppressed can be obtained.

It is a perspective schematic diagram of a part of the non-woven fabric which is one Embodiment. It is the schematic of the non-woven fabric manufacturing equipment. It is the schematic of the non-woven fabric manufacturing equipment.

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

When the plurality of voids 13 communicate with each other in the thickness direction Z of the non-woven fabric 10, pores are formed through the non-woven fabric 10 in the thickness direction Z. When the non-woven fabric 10 is used as a filter, for example, the pores function as holes in the filter. Further, some of the voids 13 do not form pores and exist as a non-penetrating space region in the thickness direction Z, for example, a space region closed by the fiber 11.

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

The fiber 11 is formed so that the diameter D1 is substantially constant. The average value (hereinafter referred to as the average diameter) DF (unit: μm) of the diameter D1 is in 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 fiber 11 itself is stronger than the case where the average diameter is less than 0.10 μm, so that the fiber 11 is hard to break, and as a result, the fiber piece is much shorter than the fiber 11. Desorption is suppressed. The non-woven fabric 10 exhibits excellent durability by suppressing the detachment of the fiber pieces. Further, when the non-woven fabric 10 is used as a filter for air conditioning, for example, clean air without fiber pieces can be sent out. Since the average diameter DF is 5.00 μm or less, the non-woven fabric 10 contains the same volume ratio of air (hereinafter referred to as porosity) as compared with the case where it is larger than 5.00 μm, even if the volume ratio (hereinafter referred to as porosity) is the same. Softer. Therefore, when the non-woven fabric 10 is used, for example, as a filter for air conditioning, it withstands a change in the pressure of the air to be sent out. Further, since the average diameter DF is 5.00 μm or less, the porosity of the non-woven fabric 10 is larger than that in the case where it is larger than 5.00 μm even if the softness is about the same, and as a result, sound absorption is achieved. When used as a material or a heat insulating material, the sound absorbing performance and the heat insulating performance are improved, and when used as a filter, the amount of filtration treatment 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 an arbitrary 100 points from an image taken with a scanning electron microscope and calculating the average value of the obtained 100 measured values.

The fiber 11 is bent along the first surface 10A. Bending along the first surface 10A means that it is bent with a component of the first surface 10A (XY plane), and may further have a component in the thickness direction Z. The fibers 11 overlap in the thickness direction Z. Among them, there are many fibers 11 that are folded in the thickness direction Z, that is, are overlapped in multiple layers. The fiber 11 is formed so long that it overlaps in the thickness direction Z in this way, 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 determined 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) in the manufacturing method described later were observed with a high-speed camera, the length was at least 30 mm. It is confirmed that there is, that is, 30 mm or more. In this way, the length of the fiber 11 can be measured during the manufacturing process. Further, among the fibers 11 constituting the non-woven fabric 10, there may be fibers 11 that do not overlap in the thickness direction Z, but in this example, the fibers 11 were observed at a magnification of 100 times using a scanning electron microscope. However, it has been confirmed that all the fibers 11 observed in one visual field overlap in the thickness direction Z.

Since the non-woven fabric 10 is formed so long that the fibers 11 overlap in the thickness direction Z, it exhibits a high elongation at break as described later. Further, for example, when an extremely short fiber larger than 0 mm and 2 mm or less exists, such a short fiber is detached as it is as a fiber piece, or the fiber piece is cut even shorter during use, for example. It may be detached. However, in the non-woven fabric 10 of this example, since the fiber 11 is long as described above, the detachment of such fiber pieces can be suppressed.

Further, since the fibers 11 are formed long enough to overlap in the thickness direction Z, when tension is applied to the non-woven fabric 10 in the direction along the XY plane, the fibers 11 follow the tension and stretch to some extent. 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 a filter for air conditioning, for example, it withstands the pressure of the air to be sent and its change.

When focusing on one fiber 11 as described above, the fibers 11 overlap each other in the thickness direction Z, but the plurality of fibers 11 also overlap each other in the thickness direction Z. As described above, in the non-woven fabric 10, since the plurality of fibers 11 are overlapped with each other and the plurality of fibers 11 are overlapped with each other, the fibers are in a folded state, and the high elongation at break as described later is obtained. It is definitely expressed.

It is preferable that the plurality of fibers 11 are entangled with each other, and the portions overlapping in the thickness direction Z and / or the portions in contact with each other in the plane direction (in the XY plane) of the non-woven fabric 10 are not adhered (non-adhesive). , This is also the case in this example. However, there may be a part where the adhesive is adhered, and even if the adhesive is adhered, the adhesive force is kept small enough to be easily peeled off with a very weak force. When tension is applied to the non-woven fabric 10, the void 13 seen from the first surface 10A side changes into a shape extending in the direction in which tension is applied due to the softness caused by the above-mentioned average diameter DF. In addition to this, the fibers 11 that overlap in the thickness direction Z are entangled as described above, but since each of the fibers 11 has a play that can be moved, the fibers 11 slide to each other. As described above, since the non-woven fabric 10 is entangled with each other in a state in which the fibers 11 can be slidably moved, the non-woven fabric 10 is not easily torn even when tension is applied.

Further, since the fibers 11 are entangled with each other or the adhesive force is suppressed to be small even if they are adhered to each other, they are soft and deformable in a state of containing a large amount of air. Therefore, for example, a heat insulating material and a sound absorbing material. When used as a material, there is a great deal of freedom in the construction site.

The non-woven fabric 10 has a porosity of 90% or more, that is, at least 90%. As described above, the non-woven fabric 10 having a very high porosity has a fluffy feeling. 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 excellent sound absorbing performance and heat insulating performance as compared with the case where the porosity is less than 90%. Further, the filter has a larger filtration treatment performance than the case where the porosity is less than 90%. The filtration treatment performance means the amount of treatment per unit time and / or the sustainability of the state in which clogging is suppressed.

The porosity is preferably 99.8% or less because higher durability of the non-woven fabric 10 is ensured. The porosity is more preferably in the range of 90% or more and 99.8% or less, further preferably in the range of 95% or more and 99.6% or less, and particularly preferably 97% or more and 99.4% or less. It is within the range. When used as a filter, it may be more preferable to use the non-woven fabric 10 as a filter after adhering the fibers 11 to each other by heating the non-woven fabric 10. For example, in the case of a filter for the purpose of separation by size (for example, a medical filter or the like), it is preferable to heat the non-woven fabric 10 to bond the fibers 11 to each other and then use the filter. This is because the pore size distribution becomes sharp due to the adhesion between the fibers 11. On the other hand, in the case of a filter for removing foreign matter (for example, a mask and a filter for air conditioning), the fibers 11 do not necessarily have to be adhered to each other by heating.

The porosity (unit:%) is such that the non-woven fabric 10 is weighed at W (unit is g / m ² ), the thickness is H (unit is mm), and the specific gravity of the fiber 11 is ρ1 (unit is kg / m ³ ). When doing so, it can be obtained by [1-{(W / 1000) / (H / 1000)} / ρ1] × 100. Weighing W is cut out a sample with an area of 5 cm × 5 cm of a non-woven fabric 10, a sample of the mass measured by an electronic balance (manufactured by Mettler-Toledo, Inc.), a value obtained by converting the measured value per 1 m ^2. In this example, the thickness H is measured by a non-contact laser displacement meter (LK-H025 manufactured by KEYENCE CORPORATION).

The thickness H of the non-woven fabric 10 is not particularly limited, and can be adjusted by the amount of the fibers 11 deposited as described later, and may be appropriately set according to the handling situation and / or the application. For example, from the viewpoint of handleability (handling) such as workability and durability in the handling scene, it is preferably in the range of 100 μm or more and 100,000 μm or less, for example. Further, when it is used as a sound absorbing material or a heat insulating material, it may be thickened (for example, within the range of 2000 μm or more and 100,000 μm or less) so that it can be constructed as it is, or it may be thinned (for example, it is constructed in a stacked state). It may be in the range of 200 μm or more and 1000 μm or less). In this example, it is set to 4000 μm. The non-woven fabric 10 has a large degree of freedom in thickness as described above, but contains a large amount of air and is soft, so that it has a wide range of uses.

Here, the average pore diameter of the non-woven fabric 10 in which the plurality of voids 13 are formed is DA (unit: μm). The average pore size DA is in the range of 0.5 μm or more and 50 μm or less. Since the pore diameter is uniform in this range and has a high porosity as described above, for example, when used as a filter, high-precision filtration is efficiently performed and clogging (clogging) is unlikely to occur. 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 size DA can be obtained by the following method. First, the non-woven fabric is cut into 5 cm squares (5 cm x 5 cm) from the non-woven fabric 10 and used as a sample. After immersing this sample in GALWICK (manufactured by POROUS MATERIAL) having a surface tension of 15.3 mN / m, the average pore size DA was measured by the bubble point method using a palm poromometer (manufactured by POROUS MATERIAL). can get.

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

The elongation at break is more preferably 15% or more, and even more preferably 20% or more. The upper limit of the elongation at break is not particularly limited, but 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 further preferably in the range of 20% or more and 94.2% or less. It can be said that it is inside.

The elongation at break (unit:%) can be determined by the following method. A sample is prepared by cutting the non-woven fabric 10 into a rectangle having a width of 20 mm and a length of 70 mm. Prepare 3 samples. With the sample length between the clips of the tensile tester (Autograph AGS-J manufactured by Shimadzu Corporation) being 50 mm, the sample is sandwiched by 10 mm each with the upper clip and the lower clip, and the tensile speed is 10 mm / min. Tensile tests of each of the three samples are performed to determine the elongation at break of each sample. The average value of the breaking elongations of the three obtained samples is taken as the breaking elongation of the non-woven fabric 10.

The fiber 11 is made of a resin (polymer). As the polymer, a polymer that can be made into a solution by dissolving in a solvent is used. Further, it is preferable that the polymer can be dissolved in a mixed solvent which is a mixture containing an alcohol. The polymer is more preferably a thermoplastic resin, and examples thereof include polymethylmethacrylate (hereinafter referred to as PMMA), cellulose-based polymers, polyesters, polyurethanes, polyolefins, and elastomers. 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 group of cellulose are substituted with an acyl group. The cellulose acylate is preferably any one of cellulose acetate propionate (CAP), cellulose triacetate (TAC), and cellulose diacetate (DAC).

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

According to the above configuration, it can be suitably used as a filter for separating or removing a target substance from a mixture of a solid and a liquid (solid-liquid mixture). Among such filters, filters that can be particularly preferably used are for foods (including beverages), medical treatments, ultrapure water, and high-purity chemicals, which are concerned about contamination of fiber pieces. It is a filter of. Specific examples thereof include a removal filter for removing fine particles and / or microorganisms from a beverage, a pretreatment filtration filter for industrial pure water, and a test filter for collecting specific cells from body fluids such as blood and saliva. .. Examples of the test filter include a blood glucose level test, a urine sugar test, a lifestyle-related disease test, a genetic test, a tumor marker test, and a test filter such as a blood test.

The non-woven fabric 10 can be manufactured by, for example, the non-woven fabric manufacturing equipment 20 shown in FIG. The non-woven fabric manufacturing equipment 20 is for manufacturing the non-woven fabric 10 by using an electrospinning method (electrospinning method). The non-woven fabric manufacturing equipment 20 includes a solution preparing unit 21 and a non-woven fabric manufacturing apparatus 22. The details of the nonwoven fabric manufacturing apparatus 22 are shown in another drawing, and in FIG. 3, only a part of the nonwoven fabric manufacturing apparatus 22 is shown.

The solution preparation unit 21 is for preparing the solution 25 that forms the fiber 11. The solution preparation unit 21 prepares the solution 25 by dissolving the cellulosic polymer 15 as the fiber material to be the fiber 11 in the solvent 26. This solution 25 is discharged from each of the nozzles 27a to 27c described later to form the fiber 11 on the support 28. In the following description, when the nozzle 27a, the nozzle 27b, and the nozzle 27c are not distinguished, the nozzle 27 is described.

The solvent 26 is a mixture composed of at least two kinds, that is, two or more kinds of compounds. Specifically, the solvent 26 is a mixture of the first compound 26a, which is different from the alcohol, and the second compound 26b, which is the 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, ..., And three or more kinds of compounds are used. May constitute 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 and the surface tension of the solution 25 discharged from the nozzle 27. be. The solvent 26 contains alcohol as the second compound 26b in a mass ratio 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, and the higher the mass ratio of alcohol in this range, the higher the elongation at break and the porosity of the non-woven fabric 10. It tends 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 further preferably in the range of 30% or more and 50% or less.

The 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 and 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 mass ratio as the second compound 26b or a higher mass ratio 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 another 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 cellulose-based polymer 15, it is preferable that the sum of the mass ratios of the other compounds and the first compound 26a is the mass ratio of the first compound 26a. That is, the sum of the mass ratios of the other compound 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. It is more preferably in the range of% or less, and further preferably in the range of 50% or more and 70% or less. As described above, it is preferable that the good solvent component in the solvent 26 has the same mass ratio as that of the second compound 26b or a higher mass ratio than that of the second compound 26b. On the other hand, when the other compound is a poor solvent for the cellulosic 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, that is, an organic solvent. It is more preferable that the first compound 26a is a liquid having a boiling point lower than that of the second compound 26b.

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

The concentration C of the polymer (cellulosic polymer 15 in this example) in solution 25 is preferably adjusted as low as possible within the range in which fibers can be formed by electrospinning, based on the type and / or molecular weight of the polymer. For example, when the cellulosic polymer 15 is used as the polymer, the concentration C is preferably in the range of 1% or more and 40% or less, more preferably in the range of 2% or more and 30% or less, and 3%. It is more preferably in the range of 20% or more.

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. The temperature control mechanism regulates the temperature of these mixtures and promotes dissolution. If the temperature is surely melted without adjusting the temperature, the temperature control mechanism may not be used. In this example, dissolution is promoted by heating to, for example, 35 ° C. However, the 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.). In addition, the stirring mechanism promotes dissolution by stirring the above mixture. When it is surely dissolved without stirring, the stirring mechanism may not be used.

In this example, the solvent 26, which is a mixture of the first compound 26a and the second compound 26b, is guided to the solution preparation unit 21, but the present invention is not limited to this embodiment. For example, the first compound 26a and the cellulosic polymer 15, which are good solvents, may be guided to the solution preparation unit 21 first, and after dissolution, the second compound 26b may be guided to the solution preparation unit 21.

In this example, the non-woven fabric manufacturing equipment 20 includes pipes 33a to 33c connecting the solution preparation unit 21 and the non-woven fabric manufacturing apparatus 22, and the non-woven fabric manufacturing apparatus 22 has nozzles 27a to 27c arranged in a state of being separated from each other. .. The pipes 33a to 33c are for guiding the solution 25. The pipe 33a connects the solution preparation unit 21 and the nozzle 27a, the pipe 33b connects the solution preparation unit 21 and the nozzle 27b, and the pipe 33c connects the solution preparation unit 21 and the nozzle 27c. As a result, the solution 25 is discharged from each of the nozzles 27a to 27c. The solutions 25 discharged from the nozzles 27a to 27c form the fibers 11, respectively. In the following description, when the pipe 33a, the pipe 33b, and the pipe 33c are not distinguished, the pipe 33 is described.

In this example, a long support 28 is used for collecting and depositing the fiber 11 and supporting the non-woven fabric 10, and the support 28 is moved in the longitudinal direction. In the following description, when collecting and depositing are collectively described, it is described as "accumulation". The details of the support 28 will be described later with reference to another drawing, but the lateral direction in FIG. 2 is the width direction of the support 28, and the paper depth direction in FIG. 2 is the movement direction of the support 28. The nozzles 27a to 27c are arranged in this order in the width direction of the support 28. In this example, the number of nozzles 27 is three, but the number of nozzles 27 is not limited to this. Each of the pipes 33a to 33c is provided with a pump 38 that sends the solution 25 to the nozzle 27. By changing the rotation speed of the pump 38, each discharge amount of the solution 25 discharged from the nozzles 27a to 27c is adjusted.

The nozzles 27a to 27c are held by the holding member 41. The holding member 41 and the nozzle 27 constitute a nozzle unit 42 of the non-woven fabric manufacturing apparatus 22.

The non-woven fabric manufacturing apparatus 22 will be described with reference to FIG. FIG. 3 shows a case where the nozzle 27a is viewed from the nozzle 27a side of FIG. 2, and only the nozzle 27a is shown for the nozzle 27. The non-woven fabric manufacturing apparatus 22 includes a chamber 45, the nozzle unit 42 described above, an integration unit 50, a power supply 51, and the like.

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

The chamber 45 includes a humidity adjusting mechanism 45a that adjusts the internal relative humidity (hereinafter, simply referred to as humidity). The humidity adjusting mechanism 45a sends a humidity-adjusted gas (for example, air) to the chamber 45, recovers the atmosphere in the chamber 45, adjusts the humidity again, and then sends the gas to the chamber 45. In this way, the humidity inside the chamber 45 is 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 a function of partitioning the spinning space from the external space and adjusting the humidity of the spinning space. However, the adjustment of the humidity of the spinning space is not limited to the method of this example using the chamber 45, and may not be performed. For example, the humidity of the spinning space may be adjusted by a chamber that defines the spinning space in the chamber 45.

The humidity of the spinning space is preferably 10% or more and 30% or less. The humidity may change within this range during the production of the non-woven fabric 10. The humidity of the spinning space is more preferably in the range of 15% or more and 25% or less.

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

The accumulating portion 50 is arranged below the nozzle 27. The collecting unit 50 includes a collector 52, a collector rotating unit 56, a support supply unit 57, and a support winding unit 58. The collector 52 is for attracting the solution 25 discharged from the nozzle 27 and collecting the formed fibers 11 as the non-woven fabric 10, and in the present embodiment, it is collected on the support 28 described later.

The collector 52 is composed of an endless belt formed in an annular shape by a metal strip. The collector 52 may be made of a material that is charged by applying a voltage from the power supply 51, and is made of, for example, stainless steel. The collector rotating portion 56 includes a pair of rollers 61 and 62, a motor 60, and the like. The collector 52 is horizontally hung on 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 the rollers 62. In the present embodiment, the moving speed of the collector 52 is, for example, 0.2 m / min, but the moving speed is not limited to this.

A support 28 made of, for example, a strip-shaped aluminum sheet is supplied to the collector 52 by the support supply unit 57. The support 28 is for accumulating the fibers 11 to obtain the non-woven fabric 10. The support supply unit 57 has a delivery shaft 57a. A support roll 63 is mounted on the delivery shaft 57a. The support roll 63 is configured by winding the support 28 around the winding core 64. The support winding portion 58 has a winding shaft 67. The winding shaft 67 is rotated by a motor (not shown), and the support 28 on which the non-woven fabric 10 is formed is wound around the winding core 68 to be set. As described above, the non-woven fabric manufacturing apparatus 22 has a function of forming the fiber 11 and a function of forming the non-woven fabric 10. The support 28 may be placed on the collector 52 and moved by moving the collector 52.

The non-woven fabric 10 may be formed by directly integrating 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 non-woven fabric 10 may be stuck and difficult to peel off. In some cases. Therefore, as in the present embodiment, it is preferable to guide the support 28 to which the non-woven fabric 10 is hard to stick on the collector 52, and to integrate the fibers 11 on the support 28.

The power supply 51 applies a voltage to the nozzle 27 and the collector 52, whereby the nozzle 27 is charged to the first polarity and the collector 52 is charged to the second polarity opposite to the first polarity. It is a 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 supply 51 to the holding member 41, a voltage is applied to the nozzle 27 via the holding member 41. The method of applying the voltage is not limited to this. For example, a voltage may be applied to each nozzle 27 by connecting a power supply 51 to each of the nozzles 27. In the present 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 opposite. The collector 52 side may be grounded to set the potential to 0. Due to charging, 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 a 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 type of the cellulosic polymer 15 and the solvent 26, the mass ratio of the solvent 26 in the solution 25, and the like, but is preferably in the range of 30 mm or more and 500 mm or less, and in the present embodiment. It is set to 150 mm. The distance L is preferably set as small as possible within a range in which the solvent 26 can be sufficiently evaporated from the spinning jet 69 and the fiber 11, from the viewpoint of forming the fiber 11 longer.

The 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 forming the fiber 11 thinner, the applied voltage is preferably as high as possible within this range. In this embodiment, it is set to 40 kV.

When the evaporation rate of the solvent 26 is V (unit: ml / s, milliliter / sec), the evaporation rate V and the average diameter DF of the fiber 11 formed on the support 28 are 1 ≦ V / DF ≦. It is preferable to satisfy 10. The V / DF can be set in the above range by adjusting at least one of the evaporation rate V and the average diameter DF.

The evaporation rate V is calculated by the following formula (1). The concentration C is the concentration (unit:%) of the solution 25. The concentration C is calculated by the formula of {M1 / (M1 + M2)} × 100 when the mass of the polymer (cellulosic polymer 15 in this example) is M1 and the mass of the solvent 26 is M2. Q is the discharge amount of the solution 25 from the nozzle 27 (the volume discharged per hour, and the unit is ml / h, milliliter / hour). ρ2 is the density of the solution 25 (unit: g / ml). Therefore, the evaporation rate V can be adjusted by increasing or decreasing at least one of the concentration C, the discharge 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 type and mass ratio of each compound of the first compound 26a and the second compound 26b). Further, the average diameter DF can be adjusted by increasing or decreasing at least one of the discharge amount Q, the concentration C, the applied voltage described later, and the distance L from the nozzle 27 to the support 28. In this example, since the temperature of the spinning space, which is the space between the nozzle 27 and the support 28, is set to about 25 ° C., the evaporation rate V is obtained at 25 ° C., which is roughly the same as the temperature of the spinning space. There is.
V = {(1-0.01C) x Q x 10 ^-3 } / (3600 x ρ2) ... (1)

The operation of the non-woven fabric manufacturing equipment 20 will be described. A voltage is applied to the nozzle 27 and the circulating collector 52 by the power supply 51. As a result, the nozzle 27 is positively charged as the first polarity, and the collector 52 is negatively charged as the second polarity. The solution 25 is continuously supplied to the nozzle 27 from the solution preparation unit 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 that comes out of the tip opening in a state of being charged to the first polarity. As a result, a Taylor cone 53 is formed in the tip opening, and the spinning jet 69 exits from the Taylor cone 53 toward the collector 52. The spinning jet 69, which is charged with the first polarity, splits into a smaller diameter due to the repulsion of its own charge while heading toward the collector 52, and extends to a smaller diameter while drawing a spiral trajectory. , The fiber 11 is collected on the support 28. Since the fiber 11 is deposited in an extremely short time, it will be collected as the non-woven fabric 10. The thickness of the non-woven fabric 10 can be adjusted by increasing or decreasing the amount of deposition. The amount of deposit can be increased or decreased, for example, by adjusting the moving speed of the support 28.

In this example, the solution 25 is blown toward the support 28 by ejecting the solution 25 from the nozzle 27, but the solution 25 may be blown by a method that does not use a 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 a solution 25 and a voltage is applied to the generated bubbles to linearly blow the solution 25 from the bubble surface to form a fiber 11, from Hirose Paper Co., Ltd. The method is introduced. The wire fixing electrode method is a method of forming a fiber 11 by applying a solution to a wire having both ends fixed and applying a voltage between the wire and a collector. A fiber forming apparatus using this fixed wire electrode method is sold by, for example, El Marco Co., Ltd.

If the evaporation rate of the solvent in the solution discharged from the nozzle 27 exceeds the balance with the surface tension and is excessively large, the solution does not reach the support 28 as the fiber 11 and scatters to the surroundings. On the other hand, if the surface tension of the solution exceeds the balance with the evaporation rate of the solvent and is excessively large, the solution forms droplets and is mixed in the non-woven fabric as beads (microspheres). However, in the present embodiment, since the solvent 26 contains an alcohol which is the second compound 26b in a mass ratio of 10% or more, 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 toward the support 28. Therefore, the spinning jet 69 splits and becomes smaller in diameter while drawing a spiral trajectory, forming a longer fiber 11 having an average diameter DF in the range of 0.10 μm or more and 5.00 μm or less. It deposits on the support 28. Therefore, the non-woven fabric 10 is provided with fibers 11 overlapping in the thickness direction Z, has a porosity of at least 90%, has an average pore diameter DA of 0.5 μm or more and 50 μm or less, and has a breaking elongation of at least 10%. It becomes. The above action is particularly remarkable when the fiber material is one of the cellulosic polymer 15, especially CAP, TAC, and DAC.

Since the first compound 26a has the same mass ratio as the second compound 26b or a higher mass ratio than the second compound 26b, the cellulose-based polymer 15 is surely solidified at the tip of the nozzle 27 for a longer period of time. The non-woven fabric 10 having the above structure is more reliably formed on the support 28 while being suppressed.

In general, the lower the boiling point of a substance, the higher the evaporation rate of the liquid. Therefore, in the present embodiment, a liquid having a boiling point lower than that of the second compound 26b is used as the first compound 26a. Since the first compound 26a is a liquid having a boiling point lower than that of the second compound 26b, the solvent 26 evaporates rapidly in the solution 25 discharged from the nozzle 27 while maintaining the surface tension and balance. Therefore, on the support 28. Even if the fibers 11 are not adhered to each other or adhered to each other, the adhesive strength is suppressed to an extremely weak level. As a result, the non-woven fabric 10 is more reliably produced within a porosity of at least 90% and an average pore diameter DA of 0.5 μm or more and 50 μm or less.

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

Since the humidity of the spinning space is adjusted, the water content of the fiber 11 on the support 28 is adjusted to 3.0% or more and 10% or less. As a result, the non-woven fabric 10 is more reliably manufactured with a porosity of 90% or more, and the hygroscopic fiber 11 is suppressed from being deformed by its own weight, so that the porosity is easily maintained high.

The non-woven fabric 10 is sent to the support winding section 58 together with the support 28. The non-woven fabric 10 is wound around the core 68 in a state of being overlapped with the support 28. After the winding core 68 is removed from the winding shaft 67, the non-woven fabric 10 is separated from the support 28. The non-woven fabric 10 thus obtained is long, but may be subsequently cut into, for example, a desired size.

In this example, a belt that circulates as the collector 52 is used, 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 a collector made of a flat plate or a cylindrical body, it is preferable to use the support 28 so that the non-woven fabric 10 can be easily separated from the collector. When a rotating body is used, a tubular sheet material made of fibers is formed on the peripheral surface of the rotating body. Therefore, after spinning, the tubular sheet material is pulled out from the rotating body to obtain a desired size and shape. Just cut it.

In the above example, the nozzle 27 is arranged with the tip opening facing downward, and the collector 52 is arranged under the nozzle 27, whereby the solution 25 is discharged downward. However, the discharge direction 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 arranging the collector 52 on the nozzle 27.

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

The solvent 26 is a mixture of two compounds, the first compound 26a and the second compound 26b. The first compound 26a and the second compound 26b are shown in Table 1. In Table 1, "DMC" is dichloromethane, "Methanol" is methanol, and "EtOH" is ethanol. The "Mass ratio between the first compound and the second compound" column of Table 1 indicates (mass of the first compound) :( mass of the second compound). For example, "87:13" means ( The mass of the first compound): (mass of the second compound) = 87:13. “Concentration C” in Table 1 is a percentage calculated by the formula (C1 / C26) × 100 when the mass of the fiber material is C1 and the mass of the solvent 26 is C26.

For the non-woven 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. The obtained elongation at break is shown in Table 1. Desorption of fiber pieces was evaluated by the following method.

A circular sample having a diameter of 47 mm was cut out from the obtained non-woven fabric 10. This sample is attached to a stainless line holder (manufactured by Advantech Toyo Co., Ltd., KS-47), a membrane filter (manufactured by Advantech Toyo Co., Ltd., A080P047A) is set on the downstream side thereof, and 1 L (liter) of ultrapure water is passed through. rice field. The residual state of the fiber pieces on the membrane filter after water flow was visually observed, and the detachment of the fiber pieces was evaluated according to the following criteria. A and B pass, C fails. The evaluation results are shown in Table 1.

A: No fiber pieces were found.
B; Although fiber pieces were observed, the amount was extremely small and there was no problem in practical use.
C: A large amount of fiber pieces were observed.

Further, the non-woven fabric 10 obtained in Example 1 was used to perform a genetic test. Specifically, after filtering human whole blood with the non-woven fabric 10 obtained in Example 1, leukocyte cells remaining on the non-woven fabric 10 are used, and paragraphs [0057] to [0061] of the specification of Japanese Patent No. 40558508 are used. Genetic testing was performed according to the method described in. As a result, the same results as those of the examples described in Japanese Patent No. 40558508 were obtained.

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

The elongation at break was determined by the same method and criteria as in the examples, and the detachment of the fiber pieces was evaluated. The evaluation results are shown in Table 1.

10 Non-woven fabric 10A 1st surface 11 Fiber 13 Void 15 Cellulose-based polymer 20 Non-woven fabric manufacturing equipment 21 Solution preparation department 22 Non-woven fabric manufacturing equipment 25 Solution 26 Solvent 26a 1st compound 26b 2nd compound 27a-27c Nozzle 28 Support 33a-33c Piping 38 Pump 41 Holding member 42 Nozzle unit 45 Chamber 45a Humidity adjustment mechanism 50 Integration part 51 Power supply 52 Collector 53 Taylor cone 56 Collector rotation part 57 Support support part 57a Sending shaft 58 Support winding part 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 (12)

In a non-woven fabric formed of multiple fibers
The average diameter of the plurality of fibers is within the range of 0.10 μm or more and 5.00 μm or less.
Porosity is at least 90%
The average pore diameter is within the range of 0.5 μm or more and 50 μm or less.
A non-woven fabric having a breaking elongation of at least 10%. The non-woven fabric according to claim 1, wherein the fiber is made of a cellulosic polymer. The non-woven fabric according to claim 2, wherein the cellulosic polymer is cellulose acylate. The non-woven fabric according to claim 3, wherein the cellulose acylate is any one of cellulose acetate propionate, cellulose triacetate, and cellulose diacetate. In a non-woven fabric manufacturing method for manufacturing a non-woven fabric formed of fibers by applying a voltage between a solution in which a fiber material is dissolved in a solvent and a collector and attracting the solution to the collector.
A method for producing a non-woven fabric, wherein the solvent is a mixture containing alcohol in a mass ratio of at least 10%. The method for producing a non-woven fabric according to claim 5, wherein the alcohol is either methanol or ethanol. The method for producing a non-woven fabric according to claim 5 or 6, wherein the solvent contains a liquid having a boiling point lower than that of the alcohol. The method for producing a non-woven fabric according to claim 7, wherein the solvent contains the liquid in the same mass ratio as the alcohol or in a mass ratio higher than that of the alcohol. The method for producing a non-woven fabric according to claim 7 or 8, wherein the liquid is either dichloromethane, chloroform, or acetone. The method for producing a non-woven fabric according to any one of claims 5 to 9, wherein the fiber material is a cellulosic polymer. The method for producing a non-woven fabric according to claim 10, wherein the cellulosic polymer is a cellulose acylate. The method for producing a non-woven fabric according to claim 11, wherein the cellulose acylate is any one of cellulose acetate propionate, cellulose triacetate, and cellulose diacetate.

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