WO2019176490A1

WO2019176490A1 - Fiber sheet, and fiber sheet producing method

Info

Publication number: WO2019176490A1
Application number: PCT/JP2019/006504
Authority: WO
Inventors: 洋亮中川; 金村　一秀; 竜太竹上; 邦行神長
Original assignee: 富士フイルム株式会社
Priority date: 2018-03-14
Filing date: 2019-02-21
Publication date: 2019-09-19
Also published as: TW201938872A; JPWO2019176490A1; JP7163363B2

Abstract

Provided are: a fiber sheet which has excellent filtration accuracy and in which the detachment of a fiber piece is suppressed; and a fiber sheet producing method for producing a fiber sheet. This fiber sheet (10) is formed of fibers (11, 11a, 11b, 11c). Pores (12) are formed in the fiber sheet (10). The average pore diameter DA of the pores (12) is within the range of 2-20 μm. In the fiber sheet (10), the proportion of pores having a pore diameter within the range of DA×0.80 to DA×1.20 in the pores (12) is at least 90%.

Description

Fiber sheet and fiber sheet manufacturing method

The present invention relates to a fiber sheet and a fiber sheet manufacturing method.

A fiber sheet made of fiber is known. Examples of the fiber include a so-called nanofiber having a nano-order diameter of several nm or more and less than 1000 nm, and a so-called micron fiber having a diameter of several micrometers or more and less than 1000 μm.

As a fiber sheet, for example, Patent Document 1 includes a plurality of nanofibers made of a thermoplastic resin (thermoplastic polymer) and a lump formed by adhesion of nanofibers, and a lump that satisfies a predetermined condition. A nanofiber sheet containing a predetermined amount or more per unit area is described. In this nanofiber sheet, pores having a diameter of 5 μm or less are formed between nanofibers.

Such fiber sheets are actively developed for use in various fields. Examples of expected applications include filters, and examples of filters include solid-gas separation filters that separate solids and gases, and solid-liquid separation filters that separate solids and liquids.

Incidentally, an electrospinning method is known as a method for producing a fiber such as a nanofiber and a fiber sheet. As described in Patent Document 1, the electrospinning method is also referred to as an electrospinning method, and is performed using, for example, an electrospinning device (also referred to as an electrospinning device) having a nozzle, a collector, and a power source. In this electrospinning apparatus, a voltage is applied between a nozzle and a collector by a power source, and for example, the nozzle is negatively charged and the collector is positively charged.

When a solution, which is a raw material, is taken out from the nozzle in a state where a voltage is applied, a conical projection composed of a solution called a Taylor cone 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 and a spinning jet is formed. The spinning jet moves to the collector by the Coulomb force and is collected as a fiber on the collector, and a fiber sheet composed of fibers is formed on the collector. The fiber sheet thus obtained may be subjected to heat treatment, and even in Patent Document 1, heat treatment is performed.

JP 2016-199828 A

The filter is required to have filtration accuracy as separation performance, but the fiber sheet described in Patent Document 1 has insufficient filtration accuracy when used for filtration. The filter is also required to have durability, but the fiber sheet described in Patent Document 1 may be detached from the fiber piece when used for filtration.

Therefore, an object of the present invention is to provide a fiber sheet that is excellent in filtration accuracy and in which desorption of fiber pieces is suppressed, and a fiber sheet manufacturing method for manufacturing the fiber sheet.

The fiber sheet of the present invention is made of fiber and has pores. The average pore diameter of the pores is in the range of 2 μm to 20 μm. When the average hole diameter is DA, the ratio of holes having a hole diameter in the range of DA × 0.80 to DA × 1.20 is at least 90%.

When the angle between the fiber and the sheet surface of the fiber sheet is θ, and 0 ° ≦ θ ≦ 90 °, θ is preferably 20 ° or less.

The fiber is preferably formed of a cellulosic polymer, and the cellulosic polymer is preferably cellulose acylate, and the cellulose acylate includes cellulose acetate propionate, cellulose acetate butyrate, and cellulose triacetate. It is preferable that it is either.

The fiber sheet manufacturing method of the present invention includes a collecting step, a tension applying step, and a heating step, and collects fibers and manufactures a fiber sheet in which holes are formed. The collection process includes a polymer and a solvent, and the charged solution is attracted to a collector that is charged with a polarity opposite to that of the solution or that has a potential of zero, thereby sheeting the fiber formed of the polymer. Collect as material. The tension applying step applies tension to the sheet material. In the heating step, the fibers are bonded to each other by heating the sheet material to which tension is applied.

It is preferable that the fiber sheet manufacturing method further includes a cooling step of cooling the fiber sheet obtained in the heating step in a state where tension is applied, and the tension is released after cooling.

In the heating step, it is preferable to heat the sheet material to the glass transition point or more and the melting point or less of the polymer.

According to the present invention, it is possible to obtain a fiber sheet that is excellent in filtration accuracy and in which detachment of fiber pieces is suppressed.

It is a schematic perspective view of the fiber sheet which is one Embodiment of this invention. It is explanatory drawing of angle | corner (theta) to make. It is a schematic diagram of sheet material formation equipment. It is the schematic of a sheet material forming apparatus. It is the schematic of a temperature control apparatus. 2 is an SEM (Scanning / Electron / Microscope, scanning electron microscope) image of the fiber sheet obtained in Example 1. FIG. 6 is a SEM image of the fiber sheet obtained in Comparative Example 2.

A fiber sheet 10 according to the present embodiment shown in FIG. However, the fiber sheet should just contain the fiber 11, and in addition to the fiber 11, you may provide the other fiber from which a raw material differs. In FIG. 1, the XY plane is the film surface of the fiber sheet 10, and Z is the thickness direction of the fiber sheet 10.

The diameter of the fiber 11 is approximately 1.8 μm in the present embodiment, but is not particularly limited. When the fiber sheet 10 is used as a solid-gas separation or solid-liquid separation filter, the diameter of the fiber 11 is preferably in the range of 0.1 μm to 5 μm. This is because the detachment of the fiber piece is further suppressed. The suppression of the fiber piece detachment means that the fiber piece detachment from the fiber sheet 10 is suppressed, and the suppression of the fiber piece detachment leads to excellent durability. In FIG. 1, only a part on one sheet surface side in the thickness direction Z of the fiber sheet 10 is drawn in order to avoid complication of the drawing. Therefore, the fiber sheet 10 has a structure in which the fibers 11 are further overlapped in the thickness direction Z.

The thickness of the fiber sheet 10 is preferably in the range of 5 μm to 5000 μm, more preferably in the range of 10 μm to 3000 μm, and still more preferably in the range of 20 μm to 1000 μm. In this example, it is 50 μm.

The fiber sheet 10 has a plurality of holes 12. The air holes 12 are formed so as to penetrate through in the thickness direction Z of the fiber sheet 10 among the air gaps defined as the space regions defined by the fibers 11. Accordingly, some voids exist as a space region that does not penetrate in the thickness direction Z, for example, is closed by the fiber 11, without forming the air holes 12 penetrating in the thickness direction Z.

Here, the average pore diameter of the plurality of holes 12 is DA (unit: μm). The average pore diameter DA is in the range of 2 μm to 20 μm. When the average pore diameter DA is 2 μm or more, when the fiber sheet 10 is used as a filter for filtration, for example, the processing amount per unit time is increased as compared with the case where the average pore diameter DA is less than 2 μm. A large amount of processing per unit time means that filtration efficiency is good. When the average pore diameter DA is 20 μm or less, detachment of the fiber pieces is suppressed when used as a filter for filtration, for example, compared to a case where the average pore diameter DA is larger than 20 μm. The average pore diameter DA is more preferably in the range of 3 μm to 15 μm, and still more preferably in the range of 4 μm to 10 μm.

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 fiber sheet 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 is determined by measuring by a bubble point method using a palm porometer (manufactured by POROUS MATERIAL). can get.

Among the plurality of holes 12, the ratio of holes 12 having a hole diameter in the range of DA × 0.80 to DA × 1.20 (hereinafter referred to as a predetermined hole ratio) is at least 90%, that is, 90%. That's it. Thus, since the distribution of the hole diameter of the air holes 12 is very small, when used as a filter for filtration, the pores 12 are separated with excellent filtration accuracy. The predetermined vacancy ratio (unit:%) is more preferably 95% or more, further preferably 98% or more, and is preferably closer to 100% in this way.

The predetermined pore ratio was calculated from the sum (quantity) of pores 12 that is DA × 0.80 or more and DA × 1.20 or less with respect to the pore size distribution obtained from a palm porometer (manufactured by POROUS MATERIAL). . Specifically, using the pore size distribution output by the palm porometer (correlation data between the pore size and the abundance of pores having the pore size), the range of DA × 0.80 to DA × 1.20 is used. The ratio of the amount of holes having a hole diameter to the total amount of holes was determined as a predetermined hole ratio.

It is preferable that the fibers 11 are bonded to each other in a portion overlapping in the thickness direction Z and / or a portion in contact in the sheet surface direction (in the XY plane) of the fiber sheet 10, and in this example as well. Yes. In this way, the fibers 11 are fixed to each other. By this fixing, the fiber sheet 10 is further suppressed from detaching the fiber pieces.

The fiber 11 is made of a polymer, more specifically, a thermoplastic resin (polymer). The thermoplastic resin of this example is a cellulose polymer 15 (see FIG. 3). 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 acyl groups.

Cellulose acylate includes cellulose acetate propionate (hereinafter referred to as CAP, melting point Tm is 188 ° C. or higher and 210 ° C. or lower, glass transition point Tg is 147 ° C.), and cellulose acetate butyrate (hereinafter referred to as CAB, melting point Tm). Is 195 ° C. or higher and 205 ° C. or lower, glass transition point Tg is 141 ° C.) and cellulose triacetate (hereinafter referred to as TAC, melting point Tm is 290 ° C., glass transition point Tg is 200 ° C.). preferable. Thereby, it can be used as a filter with high filtration accuracy and high durability even under high temperature conditions of, for example, 100 ° C. or more and 140 ° C. or less.

2, the

fibers

11a, 11b, 11c,... Extend in a direction along one sheet surface (hereinafter referred to as a first sheet surface) 10A. The direction along the surface may extend with an in-plane component parallel to the first sheet surface 10A, and may be bent in the surface. The other sheet surface (not shown, hereinafter referred to as the second sheet surface) and the first sheet surface 10A may be regarded as parallel. Therefore, the

fibers

11a, 11b, 11c,... Extend in the direction along the second sheet surface. In addition, when not distinguishing

fiber

11a, 11b, 11c, ..., it describes as the fiber 11. FIG.

An angle formed by the fiber 11 and the first sheet surface 10A is θ (unit: °). However, the angle θ formed is defined within a range of 0 ° to 90 °, that is, 0 ° ≦ θ ≦ 90 °. The formed angle θ is preferably 20 ° or less, and thus extends in the direction along the first sheet surface 10A. In FIG. 2, the angle θ formed to avoid complication of the drawing is shown only for the fiber 11b, but the same applies to the

other fibers

11b, 11c,. The formed angle θ is more preferably 15 ° or less, and further preferably 10 ° or less.

The formed angle θ can be obtained using an SEM (Scanning Electron Microscope) image, and is also obtained by this method in this example. First, the fiber sheet 10 is cut in the thickness direction, and an image on the SEM is observed. When an image is observed, a part of the longitudinal direction of one fiber 11 is observed in a line segment shape. Twenty of the line-shaped fiber portions are arbitrarily selected, and the angles θ1, θ2, θ3,..., Θ20 (unit: °) formed by each of them are measured. An average value of the measured angles formed by these 20 is obtained by a calculation formula of (θ1 + θ2 + θ3 +... + Θ20) / 20, and is defined as an angle θ formed therefrom. Of the 20 fiber parts to be selected from the image, it is preferable to select an observed fiber part having as large an angle θ as possible.

According to the above configuration, since the filtration accuracy is excellent and the detachment of the fiber piece is suppressed, it is suitable as a filter for separating or removing a target substance from a mixture of solid and liquid (solid liquid mixture). Can be used. Among such filters, a filter that can be particularly preferably used is for food (including beverages), for medical use, for ultra-high precision separation performance, because there is a concern about contamination of fiber pieces (contamination). It is a filter for pure water and high-purity chemical liquid. Specific examples include a filter for removing fine particles and / or microorganisms from beverages, a pretreatment 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 test filter for blood glucose level test, urine sugar test, lifestyle-related disease test, genetic test, tumor marker test, blood test, and the like.

The fiber sheet 10 is manufactured by a manufacturing method having a sheet material forming step and a fiber sheet forming step. In the sheet material forming step, the sheet material 16 (see FIG. 3) is formed. The sheet material 16 is a precursor of the fiber sheet 10. In the fiber sheet forming step, the fiber sheet 10 is formed from the sheet material 16.

The sheet material forming equipment 20 shown in FIG. 3 is for forming the sheet material 16 using an electrospinning method. The sheet material forming facility 20 includes a solution preparation unit 21 and a sheet material forming device 22. The details of the sheet material forming apparatus 22 are shown in another drawing, and only a part of the sheet material forming apparatus 22 is shown in FIG.

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 cellulose polymer 15 in the solvent 26 of the cellulose polymer.

In the present embodiment, a mixture of dichloromethane and methanol is used as the solvent 26. When cellulose acylate is used as the cellulose polymer 15, the solvent 26 is methanol, ethanol, isopropanol, butanol, benzyl alcohol, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl formate. Ethyl formate, hexane, cyclohexane, dichloromethane, chloroform, carbon tetrachloride, benzene, toluene, xylene, dimethylformamide, N-methylpyrrolidone, diethyl ether, dioxane, tetrahydrofuran, 1-methoxy-2-propanol and the like. These may be used alone or in combination depending on the type of cellulose acylate.

In this example, the sheet material forming facility 20 includes pipes 33a to 33c that connect the solution preparation unit 21 and the sheet material forming apparatus 22, and the sheet material forming apparatus 22 includes nozzles 36a to 36 that are arranged in a state of being separated from each other. 36c. The pipes 33a to 33c are for guiding the solution 25. The pipe 33a connects the solution preparation unit 21 and the nozzle 36a, the pipe 33b connects the solution preparation unit 21 and the nozzle 36b, and the pipe 33c connects the solution preparation unit 21 and the nozzle 36c. Thereby, the solution 25 is discharged from each of the nozzles 36a to 36c. The solutions 25 exiting from the nozzles 36a to 36c form the fibers 11, respectively. In the following description, when the pipe 33a, the pipe 33b, and the pipe 33c are not distinguished, they are described as the pipe 33. Moreover, when not distinguishing the nozzle 36a, the nozzle 36b, and the nozzle 36c, it describes as the nozzle 36. FIG.

In this example, a long support 37 is used for collecting the fibers 11 and supporting the sheet material 16, and the support 37 is moved in the longitudinal direction. Although details of the support 37 will be described later with reference to another drawing, the horizontal direction in FIG. 3 is the width direction of the support 37, and the depth direction in FIG. 3 is the movement direction of the support 37. The nozzles 36 a to 36 c are arranged in this order in the width direction of the support 37. In this example, the number of nozzles 36 is three, but the number of nozzles 36 is not limited to this. Each of the pipes 33a to 33c is provided with a pump 38 for sending the solution 25 to the nozzle 36. By changing the rotation speed of the pump 38, each flow rate of the solution 25 exiting from the nozzles 36a to 36c is adjusted.

The nozzles 36a to 36c are held by a holding member 41. The holding member 41 and the nozzle 36 constitute a nozzle unit 42 of the sheet material forming apparatus 22.

The sheet material forming apparatus 22 will be described with reference to FIG. FIG. 4 shows the case seen from the nozzle 36a side of FIG. 3, and only the nozzle 36a is shown for the nozzle 36 in order to avoid complication of the drawing. The sheet material forming apparatus 22 includes a spinning chamber 45, the nozzle unit 42 described above, a stacking unit 50, a power source 51, and the like. The spinning chamber 45 houses, for example, the nozzle unit 42 and a part of the stacking unit 50, and is configured to be hermetically sealed to prevent the solvent gas from leaking to the outside. The solvent gas is obtained by vaporizing the solvent 26 of the solution 25.

The nozzle unit 42 is arranged in the upper part of the spinning chamber 45. The tip from which the solution 25 of the nozzle 36 exits is directed to the collector 52 disposed below the nozzle 36 in FIG. When the solution 25 exits from an opening formed in the tip of the nozzle 36 (hereinafter referred to as a tip opening), a generally conical Taylor cone 53 is formed by the solution 25 in the tip opening.

The stacking unit 50 is disposed below the nozzle 36. The stacking 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 attracts the solution 25 from the nozzle 36 and collects the formed fiber 11 as the sheet material 16. In this embodiment, the collector 52 collects on the support 37 described later.

The collector 52 is composed of an endless belt formed of a metal strip. The collector 52 may be made of a material that is charged when a voltage is applied by the power supply 51, and is made of, for example, stainless steel. The collector rotating unit 56 includes a pair of

rollers

61 and 62, a motor 60, and the like. The collector 52 is stretched horizontally around the pair of

rollers

61 and 62. A motor 60 disposed outside the spinning chamber 45 is connected to the shaft of one roller 61 and rotates the roller 61 at a predetermined speed. This rotation causes the collector 52 to move and circulate between the

rollers

61 and 62. In the present embodiment, the moving speed of the collector 52 is, for example, 0.2 m / min, but is not limited thereto.

The support body 37 made of a strip-shaped aluminum sheet is supplied to the collector 52 by the support body supply section 57. The support 37 is for collecting the fibers 11 and obtaining the sheet material 16. The support body supply unit 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 a support 37 around a core 64. The support winding unit 58 has a winding shaft 67. The winding shaft 67 is rotated by a motor (not shown), and the support body 37 on which the sheet material 16 is formed is wound around the core 68 to be set. As described above, the sheet material forming apparatus 22 has a function of forming the fiber 11 and a function of forming the sheet material 16, and the fiber and the sheet material are manufactured by the electrospinning method. The support 37 may be placed on the collector 52 and moved by moving the collector 52.

The sheet material 16 may be formed by directly collecting the fibers 11 on the collector 52. However, depending on the material forming the collector 52 or the surface state of the collector 52, the fiber sheet 10 may be attached and attached. It may be difficult to remove. For this reason, as in the present embodiment, it is preferable to guide the support body 37 on which the sheet material 16 is difficult to stick onto the collector 52 and to integrate the fiber 11 on the support body 37.

The power source 51 applies a voltage to the nozzle 36 and the collector 52, thereby charging the nozzle 36 to the first polarity and charging the collector 52 to the second polarity opposite to the first polarity. Part. By passing through the charged nozzle 36, the solution 25 is charged and exits the nozzle 36 in a charged state. In this example, the holding member 41 and the nozzle 36 are electrically connected, and the voltage is applied to the nozzle 36 via the holding member 41 by connecting the power source 51 to 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 36 by connecting a power source 51 to each nozzle 36. In this embodiment, the nozzle 36 is charged positively (+) and the collector 52 is negatively charged (−). However, the polarity of the nozzle 36 and the collector 52 may be reversed. The collector 52 side may be grounded and the potential may be set to zero. The solution 25 is ejected from the Taylor cone 53 toward the collector 52 as a spinning jet 69 by charging due to application of voltage. In this example, the solution 25 is charged by applying a voltage to the nozzle 36, but the solution 25 may be charged in the pipe 33 and the charged solution 2 may be guided to the nozzle 36.

The distance L between the nozzle 36 and the collector 52 varies depending on the type of the cellulosic polymer 15 and the solvent 26 and the mass ratio of the solvent 26 in the solution 25, but is preferably in the range of 30 mm to 500 mm. In this embodiment, it is set to 150 mm, for example.

The voltage applied to the nozzle 36 and the collector 52 is preferably 5 kV or more and 200 kV or less, and from the viewpoint of forming the fiber 11 to be thin, the voltage is preferably as high as possible within this range. In this embodiment, it is 40 kV, for example.

The operation of the sheet material forming facility 20 will be described. A voltage is applied by the power source 51 to the nozzle 36 and the collector 52 that circulates and moves. As a result, the nozzle 36 is positively charged as the first polarity, and the collector 52 is negatively charged as the second polarity. The solution 25 is continuously supplied from the solution preparation unit 21 to the nozzle 36, and the support 37 is continuously supplied onto the moving collector 52. The solution 25 is charged positively as the first polarity by passing through each of the nozzles 36a to 36c, and exits from the tip openings of the nozzles 36a to 36c in a charged state.

The collector 52 attracts the solution 25 that has exited from the tip opening while being charged to the first polarity. Thereby, a Taylor cone 53 is formed at the tip opening, and the spinning jet 69 is ejected from the Taylor cone 53 toward the collector 52. The spinning jet 69 charged to the first polarity splits into a smaller diameter due to repulsion due to its own charge and / or extends to a smaller diameter while drawing a spiral trajectory while heading toward the collector 52. Then, the fiber 11 is collected as the sheet material 16 on the support 37 (collecting step).

In this example, the solution 25 is ejected from the nozzle 36 toward the support 37, but the solution 25 may be ejected by a method that does not use a nozzle. For example, there is an electro bubble spinning method or a wire fixed electrode method. The electro bubble spinning method is a method of forming a fiber 11 by supplying a compressed gas to the solution 25 and applying a voltage to the generated bubbles to cause the solution 25 to fly linearly from the bubble surface. The method is introduced. The wire fixed electrode method is a method of forming the fiber 11 by applying a solution to a wire having both ends fixed and applying a voltage between the wire and the collector. A fiber forming apparatus using this wire fixed electrode method is sold by El Marco Co., Ltd., for example.

A large amount of solvent 26 is evaporated from the spinning jet 69 toward the collector 52 so that the fibers 11 do not adhere to each other on the support 37 even if they are in contact with each other, or the adhesion is kept small even if they are adhered. It is preferable to make it.

The collected fiber 11 is sent to the support winding portion 58 together with the support 37 as the elastic sheet material 16. The fiber sheet 10 is wound around the core 68 in a state where the fiber sheet 10 overlaps the support 37. After the winding core 68 is removed from the winding shaft 67, the sheet material 16 is separated from the support 37. The sheet material 16 obtained in this way is long, but after that, for example, it may be cut into a desired size, and in this example, it is cut into, for example, a circle.

5 is for forming the fiber sheet 10 from the sheet material 16. The temperature adjusting device 81 shown in FIG. The temperature adjustment device 81 includes a housing part 82 and a temperature adjustment mechanism 83. The accommodating portion 82 accommodates the sheet material 16 therein. In this example, the accommodation unit 82 is provided with a mounting table 86 on which the sheet material 16 is placed. However, the configuration of the accommodation unit 82 is not particularly limited, and a commercially available thermostat or the like may be used. The temperature adjustment mechanism 83 adjusts the temperature inside the accommodating portion 82, thereby heating, cooling, or holding the sheet material 16 accommodated therein at a constant temperature. In the present embodiment, the temperature inside the accommodating portion 82 set by the temperature adjustment mechanism 83 is regarded as the temperature of the sheet material 16.

The fiber sheet 10 is formed from the sheet material 16 by the following method. First, the sheet material 16 is held by a frame 87. The frame 87 is a tension applying member that applies tension to the sheet material 16. A tension | tensile_strength is provided with respect to the sheet | seat material 16 in a surface direction (direction of XY plane) (tensile provision process). The tension is preferably suppressed to a level that does not cause wrinkles and sagging in the sheet material 16, and the area of the sheet material 16 (the surface area along the XY plane) is preferably as small as possible. The frame 87 is a circular shape that holds the sheet material 16 in a state where the sheet material 16 is exposed at the center, but the tension applying member can apply the above-described tension that does not change the area of the sheet material 16. The frame 87 is not limited. However, the tension applying member preferably retains the entire periphery rather than retaining a part of the periphery of the sheet material 16 so as not to cause wrinkles and sagging more reliably in heating and cooling described later.

The sheet material 16 held by the frame 87 and applied with tension is accommodated in the accommodating portion 82. The sheet material 16 is heated by the temperature adjustment mechanism 83 through the accommodating portion 82. The sheet material 16 is heated in a state where tension is applied, and the fibers 11 are bonded to each other in the sheet material 16 whose temperature has been increased, whereby the fiber sheet 10 is obtained (heating process). Thus, a tension | tensile_strength provision process has a heating process.

By heating in a state where tension is applied, the fiber sheet 10 having an average pore diameter DA in the range of 2 μm or more and 20 μm or less and a predetermined void ratio of 90% or more is obtained, and the angle θ formed is 20 Less than °. Further, the fibers 11 are bonded to each other, so that the fiber pieces are prevented from being detached during use such as filtration. Note that the longer the time of the heating step, the smaller the angle θ can be made. However, considering the viewpoint of suppressing the fiber 11 from being excessively melted, the time for the heating step is preferably within a range of 10 seconds to 1200 seconds, and more preferably within a range of 30 seconds to 900 seconds. preferable. The time for the heating process is a time for maintaining the temperature of the sheet material 16 at a set temperature.

Here, the melting point of the cellulose polymer 15 is Tm (unit is ° C.), and the glass transition point is Tg (unit is ° C.). In the heating step, the sheet material 16 is preferably heated to a temperature of Tg or more and Tm or less. By heating to a temperature equal to or higher than Tg, the fibers 11 are softened and the fibers 11 are easily fused (bonded by melting) as compared with the case of heating to a temperature lower than Tg. Further, by heating to a temperature below Tm, it is more reliably prevented that the fiber 11 is formed into a film without voids or carbonized due to excessive melting of the fiber 11 as compared with the case of heating to a temperature higher than Tm. Can be removed.

The tension applying step preferably includes a cooling step after the heating step. That is, it is preferable to cool the fiber sheet 10 obtained in the heating step in a state where tension is applied (cooling step). Thereby, the predetermined hole ratio of the fiber sheet 10 is easily held by the state immediately after the heating step. The tension is preferably released after the cooling step.

In this example, a circulating belt is used as the collector 52, but the collector is not limited to a belt. For example, the collector may be a fixed flat plate or a cylindrical rotating body. Also in the case of a collector made of a flat plate or a cylindrical body, it is preferable to use the support body 37 so that the sheet material 16 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. Therefore, after spinning, the cylindrical sheet material is extracted from the rotating body, and is formed into a desired size and shape. Cut it.

[Example 1] to [Example 7]
The fiber sheet 10 was manufactured using the sheet material forming equipment 20 and the temperature adjusting device 81, and Examples 1 to 7 were obtained. The cellulosic polymer 15 used is described in the “Polymer” column of Table 1. In Table 1, when the acyl group of the cellulose acylate used as the polymer is a propionyl group, it is described as “Pr”, and when it is a butanoyl group, it is described as “Bu”. The “acyl group content” (unit: wt%) in Table 1 is the catalog value of Eastman Chemical Company as it is.

Solvent 26 was a mixture of dichloromethane and methanol as described above, and the mass ratio was dichloromethane: methanol = 87: 13. The concentration of the cellulose polymer 15 in the solution 25 was 8% by mass. This concentration is obtained by {M1 / (M1 + M2)} × 100, where M1 is the mass of the cellulose polymer 15 and M2 is the mass of the solvent 26.

The heating process was performed during the tension application process. The temperature of the sheet material 16 set in the heating step and the time for which the temperature is maintained are described in the “temperature” column and “time” column of “heating step” in Table 1. The average diameter of the fiber 11 was 1.8 μm. The average value of the diameters was obtained by measuring the diameters of 100 fibers 11 from an image taken with a scanning electron microscope and calculating the average value.

The obtained fiber sheet 10 was evaluated for filtration accuracy and fiber piece detachment. Evaluation methods and evaluation criteria are as follows. The evaluation results are shown in Table 1. In addition, the SEM image of the cross section in the thickness direction of the fiber sheet 10 obtained in Example 1 is shown in FIG.

1. Filtration accuracy 1 mass% of crosslinked acrylic polydisperse particles (manufactured by Soken Chemical Co., Ltd.) having an average particle diameter of 10 μm were dispersed in pure water and filtered with a fiber sheet 10. The particle size distribution of each liquid before and after filtration was measured using a particle size distribution measuring device (manufactured by BECKMAN COULTER Co., Ltd.). From the obtained particle size distribution before and after filtration, the trapping rate of particles larger than the average pore diameter DA of the fiber sheet 10 is obtained as {{(number of particles before filtration) − (number of particles after filtration)} / (number of particles before filtration). )] × 100%, and evaluated according to the following criteria. A and B are acceptable and C and D are unacceptable.
A: The capture rate is 85% or more.
B: The capture rate is 75% or more and less than 85%.
C: The capture rate is 65% or more and less than 75%.
D: The capture rate is 65% or less.

2. Detachment of fiber piece The fiber sheet 10 was attached to a stainless line holder (KS-47 manufactured by Advantech Co., Ltd.), and 1 L (liter) of pure water was filtered. The filtered liquid (filtrate) was captured by a grid filter. The entire surface of the grid filter on the capturing side was observed with a microscope, the number of fiber pieces was counted, and evaluated according to the following criteria. A and B are acceptable and C and D are unacceptable. The results are shown in the “fiber piece detachment” column of Table 1.
A: The number of fiber pieces was 0 or more and 5 or less.
B: The number of fiber pieces was 6 or more and 10 or less.
C: The number of fiber pieces was 11 or more and 20 or less.
D: The number of fiber pieces was 21 or more.

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

[Comparative Example 1] to [Comparative Example 4]
The heating process was not performed, or the temperature of the sheet material 16 in the heating process was changed, and these were designated as Comparative Examples 1 to 3. Moreover, the comparative example 4 was implemented as a manufacturing method without a tension | tensile_strength provision process.

¡Evaluation of filtration accuracy and detachment of fiber pieces was performed by the same method and standard as in the examples. The evaluation results are shown in Table 1. In addition, the SEM image of the cross section in the thickness direction of the fiber sheet obtained by the comparative example 2 is shown in FIG.

DESCRIPTION OF SYMBOLS 10 Fiber sheet 10A

1st sheet surface

11, 11a, 11b, 11c, ... Fiber 12 Hole 15 Cellulose polymer 16 Sheet material 20 Sheet material formation equipment 21 Solution preparation part 22 Sheet material formation apparatus 25 Solution 26 Solvent 33a- 33c Piping 36a to 36c Nozzle 37 Support body 38 Pump 41 Holding member 42 Nozzle unit 45 Spinning chamber 50 Accumulation section 51 Power supply 52 Collector 53 Taylor cone 56 Collector rotation section 57 Support body supply section 57a Delivery shaft 58 Support body winding section 60

Motor

61, 62 Roller 63 Support roll 64 Winding core 67 Winding shaft 68 Winding core 69 Spinning jet 81 Temperature adjusting device 82 Housing portion 83 Temperature adjusting mechanism 86 Mounting table 87 Frame L Distance

Claims

In fiber sheets that are made of fiber and have holes,
The average pore diameter of the pores is in the range of 2 μm to 20 μm,
A fiber sheet in which, when the average hole diameter is DA, a ratio of the holes having a hole diameter in the range of DA × 0.80 to DA × 1.20 is at least 90%.
The fiber sheet according to claim 1, wherein θ is 20 ° or less when an angle formed by the fiber and a sheet surface of the fiber sheet is θ and 0 ° ≦ θ ≦ 90 °.
The fiber sheet according to claim 1 or 2, wherein the fiber is formed of a cellulosic polymer.
The fiber sheet according to claim 3, wherein the cellulosic polymer is cellulose acylate.
The fiber sheet according to claim 4, wherein the cellulose acylate is any one of cellulose acetate propionate, cellulose acetate butyrate, and cellulose triacetate.
In a fiber sheet manufacturing method for collecting fibers and manufacturing a fiber sheet in which holes are formed,
The fiber formed of the polymer is captured as a sheet material by attracting a charged solution containing a polymer and a solvent to a collector which is charged with a polarity opposite to that of the solution or whose potential is zero. Collecting process to collect,
A tension applying step for applying tension to the sheet material;
A heating step of bonding the fibers by heating the sheet material in a state in which the tension is applied;
A fiber sheet manufacturing method comprising:
A cooling step of cooling the fiber sheet obtained in the heating step in a state where a tension is applied;
The fiber sheet manufacturing method according to claim 6, wherein the tension is released after the cooling.
The fiber sheet manufacturing method according to claim 6 or 7, wherein in the heating step, the sheet material is heated to a glass transition point or more and a melting point or less of the polymer.