KR102212974B1 - Sheet and sheet manufacturing method - Google Patents

Abstract

A sheet having more improved mechanical strength, and a sheet manufacturing method for manufacturing the sheet are provided.
The nonwoven fabric as an example of the sheet includes a first nanofiber and a second nanofiber. The first nanofiber is formed from a first cellulose polymer. The second nanofiber is formed of a second cellulose polymer. The first cellulose-based polymer and the second cellulose-based polymer are cellulose-based polymers different from each other, and have a glass transition point different from each other by at least 50°C.

Description

Sheet and sheet manufacturing method

The present invention relates to a sheet and a method for producing a sheet.

Sheets formed of fibers are known, and examples of the fibers include so-called nanofibers having a nano-order diameter of several nm or more and less than 1000 nm. Sheets formed of such fibers are actively developed for use in various fields.

As the sheet, there is a nonwoven fabric, for example. For example, Japanese Patent Application Laid-Open No. 2009-095787 discloses a nonwoven fabric comprising a first fiber that is a nanofiber and a second fiber having a diameter of 1 μm or more. As the polymer of the first fiber, cellulose acylate having an acyl group substitution degree in the range of 2.0 or more and 3.0 or less is described, and as the polymer of the second fiber, PMMA (polymethyl methacrylate) is described. In this Japanese Patent Application Laid-Open No. 2009-095787, a nonwoven fabric is manufactured by collecting the first fiber and the second fiber. In addition, Japanese Patent Application Laid-Open No. 2012-036517 discloses a nonwoven fabric made of cellulose fibers having an average fiber diameter of 0.1 to 20 μm and cellulose nanofibers having an average fiber diameter of less than 100 nm. Chemically synthesized cellulose fibers can be used as materials for cellulose fibers and cellulose nanofibers, and such cellulose fibers include cellulose acetate, cellulose propionate, cellulose butyrate, carboxyalkylcellulose, and the like. As carboxyalkylcellulose, carboxymethylcellulose and carboxyethylcellulose are described.

However, as a method of manufacturing nanofibers, an electric field emission method is known. The field spinning method is also referred to as an electrospinning method, and is performed using a field spinning device (also referred to as an electrospinning device) having a nozzle, a collector, and a power source (see, for example, Japanese Unexamined Patent Publication No. 2009-095787). In this field emission device, a voltage is applied between the nozzle and the collector by a power source, so that, for example, the nozzle is negatively charged and the collector is charged positively.

When the raw material solution is discharged from the nozzle while voltage is applied, conical projections made of a solution called Taylor cone are 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 ejects from the tip of the Taylor cone to form a spinning jet. The spinning jet moves to the collector by coulomb force, is collected as nanofibers on the collector, and a nonwoven fabric composed of nanofibers is formed on the collector.

When a nonwoven fabric is formed from nanofibers obtained by an electric field spinning method, it cannot be said that the mechanical strength of the nonwoven fabric is sufficient. For example, when used as a so-called wiping cloth for wiping, fluffs are formed on the surface of the nonwoven fabric, and/or fiber pieces detached from the nonwoven fabric remain attached to the surface of the object to be wiped. . The nonwoven fabric described in JP 2009-095787 A and JP 2012-036517 A also has a certain mechanical strength, but the use is further expanded when the mechanical strength is further improved.

Accordingly, an object of the present invention is to provide a sheet with improved mechanical strength, and a sheet manufacturing method for manufacturing the sheet.

The sheet of the present invention contains a first nanofiber and a second nanofiber. The first nanofiber is formed from a first cellulose polymer. The second nanofiber is formed of a second cellulose polymer having a glass transition point different from the first cellulose polymer by at least 50°C.

In the case where the sheet is a nonwoven fabric, the present invention shows a particularly remarkable effect.

The first cellulose-based polymer is preferably a first cellulose acylate, and the present invention is particularly effective when the degree of substitution of the acyl group of the first cellulose acylate is in the range of 2.4 or more and 3.0 or less. The effect of the present invention is particularly great when the first cellulose acylate has an acetyl group as an acyl group.

The second cellulose-based polymer preferably has a glass transition point lower than that of the first cellulose acylate by at least 50°C.

The second cellulose polymer is preferably any one of second cellulose acylate, nitrocellulose, ethylcellulose, and carboxymethylethylcellulose. It is preferable that the 2nd cellulose acylate is any one of cellulose propionate, cellulose butyrate, and cellulose acetate propionate.

It is preferable that the mass ratio of the first nanofibers is in the range of 20% or more and 90% or less.

The sheet manufacturing method of the present invention includes a first extraction step, a second extraction step, and a collection step, and a sheet is manufactured by collecting the first nanofibers and the second nanofibers. In the first liquid extraction step, the first solution in a charged state is discharged from the first nozzle. In the second liquid extraction step, the second solution in a charged state is discharged from the second nozzle. The collecting step is, by attracting the first solution from the first nozzle and the second solution from the second nozzle to a collector charged with a polarity opposite to the first solution and the second solution or having a potential of zero. The first nanofibers formed of the polymer and the second nanofibers formed of the second cellulose polymer are collected. The first solution contains a first cellulose polymer and a solvent. The second solution contains a second cellulose polymer having a glass transition point different from the first cellulose polymer by at least 50°C, and a solvent.

The sheet of the present invention is excellent in mechanical strength, and according to the sheet manufacturing method of the present invention, a sheet having improved mechanical strength is obtained.

1 is a schematic perspective view of a nonwoven fabric according to the present invention.
It is an explanatory drawing explaining the outline of a nonwoven fabric manufacturing facility and a connection relationship between a solution preparation unit and a nozzle unit.
3 is a schematic diagram of a nonwoven fabric manufacturing apparatus.

The nonwoven fabric 10 shown in FIG. 1 is an example of a sheet. In this example, the nonwoven fabric 10 is composed of only the first nanofibers 11 and the second nanofibers 12 having different materials from the first nanofibers 11. However, the nonwoven fabric should just include the first nanofibers 11 and the second nanofibers 12, and in addition to the first nanofibers 11 and the second nanofibers 12, any of these Other nanofibers different from each other may be provided. The first nanofibers 11 and the second nanofibers 12 have a diameter in the range of 50 nm or more and 2000 nm or less, and are approximately 400 nm in this embodiment. The diameters of the first nanofiber 11 and the second nanofiber 12 may be the same or different.

The first nanofibers 11 are formed of a first cellulose polymer 15 (see Fig. 2). The second nanofiber 12 is formed of a second cellulose-based polymer 16 (see Fig. 2) different from the first cellulose-based polymer 15, and the second cellulose-based polymer 16 is a first cellulose-based polymer. The glass transition point differs from the polymer 15 by at least 50°C. That is, the difference in the glass transition point between the first cellulose polymer 15 and the second cellulose polymer 16 is 50°C or more. Nanofibers formed of a cellulose polymer having a lower glass transition point play a function of improving the mechanical strength of the nonwoven fabric. In this example, the second cellulose-based polymer 16 has a glass transition point compared to the first cellulose-based polymer 15 so that the second nanofiber 12 plays a function of improving the mechanical strength of the nonwoven fabric 10. It is made low.

The second nanofibers 12 are fixed to the first nanofibers 11 overlapping in the thickness direction and/or the first nanofibers 11 in contact with the surface direction of the nonwoven fabric. In this way, the first nanofibers 11 are fixed via the second nanofibers 12. By this fixation, the nonwoven fabric 10 is superior in mechanical strength as compared to the nonwoven fabric composed of only the first nanofibers 11. For this reason, when the nonwoven fabric 10 is used as a wiping cloth, for example, fluffing of the nonwoven fabric 10, separation of fiber pieces, breakage, and the like are suppressed. In addition, suppression of fluff generation means that the occurrence of fluff on the surface of the nonwoven fabric 10 is suppressed, and suppression of separation of fiber pieces means that the separation of the fiber pieces from the nonwoven fabric 10 is suppressed, and suppression of breakage means , It means that the nonwoven fabric 10 is difficult to tear. Since both the first nanofibers 11 and the second nanofibers 12 are made of a cellulose-based polymer, compared to the case where only one of the first nanofibers 11 and the second nanofibers 12 are made of a cellulose-based polymer, the field emission method is used as in this example to be described later. In the case of manufacturing a nonwoven fabric by using, since the first nanofibers 11 and the second nanofibers 12 are fixed in a stronger state, the nonwoven fabric 10 excellent in mechanical strength is surely obtained.

It is preferable that the first cellulose polymer 15 is a cellulose acylate. Cellulose acylate as the first cellulose polymer 15 is referred to as first cellulose acylate. The first cellulose acylate preferably has an acyl group substitution degree of 2.4 or more and 3.0 or less, more preferably 2.78 or more and 2.94 or less, and more preferably 2.87 or more and 2.94 or less. Cellulose acylate is a cellulose ester in which some or all of the hydrogen atoms constituting the hydroxyl group of cellulose are substituted with an acyl group. The degree of substitution of cellulose acylate in which all of the hydrogen atoms are substituted is 3.

It is preferable that the 1st cellulose acylate has an acetyl group as an acyl group, that is, acetyl cellulose is preferable. As acetylcellulose, cellulose diacetate (triacetylcellulose, hereinafter referred to as TAC) or cellulose diacetate (diacetylcellulose) having an acyl substitution degree in the range of 2.4 or more and 3.0 or less is preferable.

The second cellulose-based polymer 16 is preferably any one of cellulose acylate, nitrocellulose, ethylcellulose, and carboxymethylethylcellulose. As a result, the first nanofibers 11 and the second nanofibers 12 are fixed with greater strength, and as a result, the first nanofibers 11 are fixed more strongly through the second nanofibers 12. Therefore, it becomes the nonwoven fabric 10 with improved mechanical strength. In addition, cellulose acylate as the second cellulose polymer 16 is referred to as second cellulose acylate.

It is preferable that the 2nd cellulose acylate is any one of cellulose propionate, cellulose butyrate, and cellulose acetate propionate. As a result, the first nanofiber 11 and the second nanofiber 12 become a nonwoven fabric 10 adhered with greater strength.

The nonwoven fabric 10 preferably has a mass ratio of the first nanofibers 11 in the range of 20% or more and 90% or less, and thereby the mechanical strength as the nonwoven fabric 10 is more reliably improved. The mass ratio (unit: %) of the first nanofibers 11 is (M11/M10)×100 when the mass of the nonwoven fabric 10 is M10 and the mass of the first nanofibers 11 is M11. It is a percentage obtained by the formula of The mass ratio of the first nanofibers 11 is more preferably in the range of 40% or more and 90% or less, and more preferably in the range of 50% or more and 80% or less.

The nonwoven fabric 10 can be used as, for example, a wiping cloth, a filter, a medical nonwoven fabric (referred to as a drape) applied to a wound or the like. In addition, although the sheet of this example is the nonwoven fabric 10, it is not limited to this as long as it is a sheet provided with the 1st nanofiber 11 and the 2nd nanofiber 12, For example, a woven fabric, a knitted fabric, etc. may be sufficient.

The nonwoven fabric 10 is manufactured by the following method, for example. The nonwoven fabric manufacturing equipment 20 shown in FIG. 2 is an example of a sheet manufacturing equipment, and is for manufacturing the nonwoven fabric 10 using an electric field spinning method. The nonwoven fabric manufacturing equipment 20 includes a solution preparation unit 21 and a nonwoven fabric manufacturing apparatus 22. In addition, the details of the nonwoven fabric manufacturing apparatus 22 are shown in another drawing, and in FIG. 2, only a part of the nonwoven fabric manufacturing apparatus 22 is shown.

The solution preparation unit 21 is for preparing a first solution 25 forming the first nanofiber 11 and a second solution 26 forming the second nanofiber 12, and the first preparation It has a part 27 and a second preparation part 28. The first preparation unit 27 prepares the first solution 25 by dissolving the first cellulose polymer 15 in a solvent (hereinafter referred to as a first solvent) 31 of the first cellulose polymer ( Prepare). The second preparation unit 28 prepares the second solution 26 by dissolving the second cellulose-based polymer 16 in a solvent of the second cellulose-based polymer (hereinafter referred to as a second solvent) 32 ( Prepare).

In this embodiment, a mixture of dichloromethane and methanol is used as the first solvent 31, and the second solvent 32 is also a mixture of dichloromethane and methanol. When cellulose acylate is used as the first cellulose polymer (15) and the second cellulose polymer (16), as the first solvent (31) and the second solvent (32), 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 individually or may be mixed and used depending on the kind of cellulose acylate. When nitrocellulose is used as the second cellulose polymer 16, methanol and/or butanol are preferable as the second solvent 32. Also in the case of using ethylcellulose as the second cellulose-based polymer and in the case of using carboxymethylethylcellulose, methanol and/or butanol are similarly preferable as the second solvent 32.

In this example, the nonwoven fabric manufacturing equipment 20 is provided with pipes 33a to 33c connecting the solution preparation unit 21 and the nonwoven fabric manufacturing apparatus 22, and the nonwoven fabric manufacturing apparatus 22 is separated from each other. It has nozzles 36a to 36c arranged in a state. The pipes 33a and 33c are for guiding the first solution 25, and the pipe 33b is for guiding the second solution 26. The pipe (33a) connects the first preparation portion (27) and the nozzle (36a), the pipe (33b) connects the second preparation portion (28) and the nozzle (36b), and the pipe (33c) connects the first preparation portion The part 27 and the nozzle 36c are connected. Thus, the first solution 25 comes out from the nozzle 36a and the nozzle 36c, and the second solution 26 comes out from the nozzle 36b. The first solution 25 from the nozzle 36a and the nozzle 36c forms the first nanofibers 11, and the second solution 26 from the nozzle 36b forms the second nanofibers 12. To form. In the following description, when the pipe 33a, the pipe 33b, and the pipe 33c are not distinguished, it will be described as the pipe 33. Moreover, when the nozzle 36a, the nozzle 36b, and the nozzle 36c are not distinguished, it describes as the nozzle 36.

In addition, in this example, a long support 37 is used for integration of the first nanofiber 11 and the second nanofiber 12 and support of the nonwoven fabric, and the support 37 is moved in the longitudinal direction. . Details of the support 37 will be described later using other drawings, but the horizontal direction in Fig. 2 is the width direction of the support 37, and the depth direction of the paper in Fig. 2 is the moving direction of the support 37 to be. The nozzles 36a to 36c are arranged in a row in the width direction of the support body 37 in this order. It is preferable that the 2nd solution 26 comes out from the nozzle 36b between the nozzle 36a which discharges the 1st solution 25, and the nozzle 36c, and it is the same also in this example. As a result, the nonwoven fabric 10 having a more uniform weight per unit area can be obtained. As a result, excellent mechanical strength is expressed, and it becomes difficult to tear, for example. The weight per unit area is the mass per unit area of the nonwoven fabric. In this example, the number of nozzles 36 is three, but the number of nozzles 36 is not limited thereto. Further, each of the pipes 33a to 33c is provided with a pump 38 that sends the first solution 25 or the second solution 26 to the nozzle 36. By changing the rotation speed of the pump 38, the flow rates of the first solution 25 and the second solution 26 coming out of the nozzles 36a to 36c are adjusted.

The nozzles 36a to 36c are held by the holding member 41, and the nozzle unit 42 of the nonwoven fabric manufacturing apparatus 22 is constituted by the holding member 41 and the nozzle 36. The nonwoven fabric manufacturing apparatus 22 will be described with reference to FIG. 3. In Fig. 3, a case seen from the nozzle 36a side of Fig. 2 is shown, and in order to avoid complication of the drawing, only the nozzle 36a is used for the nozzle 36, and only the first solution 25 is used for the solution. In the illustration, the nozzle 36b, the nozzle 36c, and the second solution 26 are omitted. The nonwoven fabric manufacturing apparatus 22 includes a spinning chamber 45, the above-described nozzle unit 42, an integration unit 50, a power supply 51, and the like. The radiation chamber 45 accommodates, for example, the nozzle unit 42 and a part of the accumulating portion 50, and is configured to be sealed, thereby preventing the solvent gas from leaking to the outside. The solvent gas is obtained by vaporizing the first solvent 31 of the first solution 25 and the second solvent 32 of the second solution 26.

The nozzle unit 42 is disposed above the spinning chamber 45. The tip of the nozzle 36 from which the first solution 25 or the second solution 26 is delivered is directed toward a collector 52 disposed below the nozzle 36 in FIG. 3. When the first solution 25 and the second solution 26 come out from the opening formed at the tip of the nozzle 36 (hereinafter referred to as the tip opening), the first solution 25 or the second solution By (26), a substantially conical tailor cone 53 is formed.

The integration unit 50 is disposed below the nozzle 36. The accumulating portion 50 includes a collector 52, a collector rotating portion 56, a support supplying portion 57, and a support winding portion 58. The collector 52 attracts the first solution 25 and the second solution 26 from the nozzle 36 and collects them as the first nanofibers 11 and the second nanofibers 12. In an embodiment, it collects on the support body 37 mentioned later. The collector 52 is constituted by an endless belt formed of a metal strip. The collector 52 may be formed of a material that is charged by applying a voltage by the power source 51, and is made of, for example, stainless steel. The collector rotation unit 56 is constituted by a pair of rollers 61 and 62, a motor 60, and the like. The collector 52 extends horizontally over a 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 the roller 61 is rotated at a predetermined speed. By this rotation, the collector 52 moves as if circulating between the rollers 61 and 62. In this embodiment, although the moving speed of the collector 52 is 10 cm/hour, it is not limited to this.

A support body 37 made of a strip-shaped aluminum sheet is supplied to the collector 52 by a support body supply unit 57. The support 37 is for obtaining as the nonwoven fabric 10 by accumulating the first nanofibers 11 and the second nanofibers 12. The support body supply part 57 has a delivery shaft 57a. A support roll 63 is attached to the delivery shaft 57a. The support body roll 63 is constituted by the support body 37 being wound around the winding core 64. The support body winding part 58 has a winding shaft 67. The take-up shaft 67 is rotated by a motor (not shown), and the support 37 on which the nonwoven fabric 10 is formed is wound around the set take-up core 68. As described above, this nonwoven fabric manufacturing apparatus 22 has a function of manufacturing the first nanofibers 11 and the second nanofibers 12, and the function of manufacturing the nonwoven fabric 10, and is a nanofiber by field spinning method. And production of a nonwoven fabric is performed. Further, the support 37 may be placed on the collector 52 and moved by the movement of the collector 52.

In addition, the nonwoven fabric 10 may be formed by directly integrating the first nanofibers 11 and the second nanofibers 12 on the collector 52, but the material forming the collector 52 or the collector 52 Depending on the surface condition, etc., the nonwoven fabric 10 may stick and it is difficult to peel it off. For this reason, as in the present embodiment, the support 37 which is difficult to adhere to the nonwoven fabric 10 is guided onto the collector 52, and the first nanofiber 11 and the second nanofiber are on the support 37 It is desirable to integrate (12).

The power source 51 applies a voltage to the nozzle 36 and the collector 52, thereby charging the nozzle 36 to a first polarity, and the collector 52 to a second polarity opposite to the first polarity. It is a voltage application section that charges by By passing through the charged nozzle 36, the first solution 25 and the second solution 26 are charged and come out of the nozzle 36 in a charged state. Further, in this example, the holding member 41 and the nozzle 36 are connected to each other, and by connecting the power source 51 to the holding member 41, a voltage is applied to the nozzle 36 via the holding member 41. Although is applied, the method of applying the voltage to the nozzle 36 is not limited thereto. For example, a voltage may be applied to each nozzle 36 by connecting the power source 51 to each of the nozzles 36. In this embodiment, the nozzle 36 is positively charged and the collector 52 is negatively charged, but the polarities of the nozzle 36 and the collector 52 may be opposite. Further, the potential of the collector 52 may be grounded to be zero. In this embodiment, the voltage applied to the nozzle 36 and the collector 52 is 30 kV. By this charging, the first solution 25 or the second solution 26 is ejected from the Taylor cone 53 as a spinning jet 69 toward the collector 52. Further, in this example, the first solution 25 and the second solution 26 are charged by applying a voltage to the nozzle 36, but in the pipe 33, the first solution 25 and the second solution 26 are charged. ) May be charged to guide the first solution 25 and the second solution 26 in a charged state to the nozzle 36.

The distance L2 between the nozzle 36 and the collector 52 is the type of the first cellulose polymer 15 and the second cellulose polymer 16 and the first solvent 31 and the second solvent 32. , The appropriate value differs depending on the mass ratio of the first solvent 31 in the first solution 25 and the mass ratio of the second solvent 32 in the second solution 26, but not less than 30 mm and 300 mm It is preferable within the following range, and it is set to 180 mm in this embodiment.

The voltage applied to the nozzle 36 and the collector 52 is preferably 2 kV or more and 40 kV or less, and from the viewpoint of forming the first nanofibers 11 and the second nanofibers 12 to be thin, the voltage is possible within this range. One higher is preferred.

The operation of the above configuration will be described. A voltage is applied to the nozzle 36 and the collector 52 circulating and moving by the power source 51. Thereby, the nozzle 36 is positively charged as the first polarity, and the collector 52 is negatively charged as the second polarity. The first solution 25 and the second solution 26 are continuously supplied to the nozzle 36 from the solution preparation unit 21, and the support 37 is continuously supplied to the moving collector 52. The first solution 25 passes through each of the nozzles 36a and 36c to be positively charged, which is the first polarity, and in a charged state, comes out from the tip openings of the nozzles 36a and 36c. (The first withdrawal step). The second solution 26 is charged with a first polarity by passing through the nozzle 36b and, in a charged state, comes out from the tip opening of the nozzle 36b (second liquid extraction step).

The collector 52 attracts the first solution 25 and the second solution 26 from the tip opening in a state charged with the first polarity. Thereby, a tailor cone 53 is formed in the tip opening, and the spinning jet 69 is ejected toward the collector 52 from the tailor cone 53. The radiation jets 69 charged with the first polarity, while facing the collector 52, are divided into smaller diameters due to repulsion by their own charges, and the first nanofibers 11 and the first nanofibers 11 and the It is collected as the second nanofibers 12 (collecting step). On the support 37, the first nanofibers 11 do not adhere to each other even when they come into contact with each other, or the strength of adherence is small even when they are adhered. However, the second cellulose-based polymer 16 of the second nanofibers 12 reaches the support 37 because the glass transition point is 50°C or more lower than the first cellulose-based polymer 15 of the first nanofibers 11. Viscosity (stickiness) remains even at one point in time, and due to this, it is strongly adhered to the first nanofiber 11.

The collected first nanofibers 11 and second nanofibers 12 are sent to the supporter winding unit 58 together with the supporter 37 as a nonwoven fabric 10. The nonwoven fabric 10 is wound around the winding core 68 in a state overlapped with the support 37. After the take-up core 68 is removed from the take-up shaft 67, the non-woven fabric 10 is separated from the support 37. The nonwoven fabric 10 obtained in this way is long, but may be cut into a desired size afterwards, for example.

You may perform heat treatment for heating the obtained nonwoven fabric 10. Accordingly, the strength of adhesion between the first nanofibers 11 and the second nanofibers 12 is increased, or a portion that has not been fixed in the collection step is fixed. In addition, when performing heat treatment, it is preferable to heat the nonwoven fabric 10 at a temperature between the glass transition point of the first cellulose polymer 15 and the glass transition point of the second cellulose polymer 16.

In this example, a belt circulating in circulation was used as the collector 52, but the collector is not limited to the belt. For example, the collector may be a fixed flat plate or a cylindrical rotating body. Even in the case of a collector made of a flat plate or a cylindrical body, it is preferable to use the support 37 so that the nonwoven fabric can be easily separated from the collector. In addition, in the case of using a rotating body, since a conventional nonwoven fabric made of nanofibers is formed on the circumferential surface of the rotating body, the normal non-woven fabric is separated from the rotating body after spinning, and cut into a desired size and shape to obtain a nonwoven product. I can.

The fabric as a sheet can be manufactured by a method of making the heald opening motion by means of a cam and a tappet (a device that contacts the cam and transmits the motion of the cam). The knitted fabric as a sheet can be manufactured by forming a loop (loop) with a thread and connecting it two-dimensionally.

Example

[Example 1] to [Example 18]

The nonwoven fabric 10 was continuously manufactured by the nonwoven fabric manufacturing equipment 20, and it was set as Examples 1-18. The first cellulose-based polymer 15 and the second cellulose-based polymer 16 used are described in the “first nanofiber” and “second nanofiber” columns in Table 1. Both the first solvent 31 and the second solvent 32 were mixtures of dichloromethane and methanol as described above, and the mass ratio was set to dichloromethane:methanol=87:13. The concentration of the first cellulose polymer 15 in the first solution 25 is 4% by mass, and the concentration of the second cellulose polymer 16 in the second solution 26 is 7% by mass. did. When the mass of the first cellulose polymer 15 or the second cellulose polymer 16 is M1 and the mass of the first solvent 31 or the second solvent 32 is M2, {M1/(M1+M2)}×100. The voltage applied to each nozzle 36 and the collector 52 by the power source 51 was set to 30 kV as described above. The average value of the diameter of the first nanofibers 11 and the average value of the diameters of the second nanofibers 12 were 600 nm, respectively. The average value of the diameter was determined by measuring the diameter of 100 nanofibers from an image captured with a scanning electron microscope and calculating the average value.

When cellulose acylate is used as the cellulose-based polymer, it is described as "CA" in the "material" column of Table 1. When the material is cellulose acylate, if the acyl group is an acetyl group, write "Ac" in the "acyl group" column, write "Pr" if it is a propionyl group, and write "Bu" if it is a butane oil group. do. In addition, the "acyl group content" (unit is %) of the 2nd nanofiber is the catalog value of Eastman Chemical Company as it is described.

For the obtained nonwoven fabric 10, as an evaluation of mechanical strength, the touch and detachment of the fiber piece were evaluated. The evaluation method and evaluation criteria are as follows.

1. Touch

A sample having a size of approximately 50 mm x 50 mm was cut out from the obtained long nonwoven fabric 10. After confirming the feeling of elasticity by touching this sample with a finger, the fibers in the region touched with the finger were visually observed and evaluated according to the following criteria. A and B pass, and C and D fail. The results are shown in the "touch" column of Table 1.

A; There was a sense of elasticity, and the fibers were clearly visible with the naked eye.

B; The elasticity was slightly weak, but the fiber was visible, and there was no problem in practical use.

C; There was no sense of elasticity, and the fibers could only be checked with the naked eye.

D; No elasticity or fiber was observed.

2. Fiber side tally

A sample having a size of approximately 50 mm x 50 mm was cut out from the obtained long nonwoven fabric 10. This sample was reciprocated five times on the surface of the resin plate while applying a load of 1.47 N (=150 gf). The surface of the resin plate was visually observed and evaluated according to the following criteria. A and B pass, and C and D fail. The results are shown in the column of "Desorption of fiber pieces" in Table 1.

A; No fiber piece was found.

B; Although the fiber piece was confirmed, the amount was very small and there was no problem in practical use.

C; The aggregate (lump) of the fiber piece was confirmed.

D; A large amount of fiber pieces and aggregates of fiber pieces were identified.

[Table 1]

[Comparative Example 1]-[Comparative Example 9]

The material of the first nanofiber and the material of the second nanofiber were changed, or a nonwoven fabric was manufactured with only the first nanofiber, and these were used as Comparative Examples 1 to 9. Each material is shown in Table 1. In Table 1, when polypropylene is used as the material, it is described as "PP" in the "Material" column. In addition, in the case where the nonwoven fabric is manufactured only with the first nanofibers, "-" is indicated in each column of the second nanofiber. Other conditions were the same as in Examples. In addition, the second solvent for dissolving polypropylene is a mixture of dichloromethane and methanol, and the mass ratio is set to dichloromethane:methanol = 87:13. In the second solution using polypropylene, the concentration of polypropylene was 7% by mass.

Using the same method and standard as in Examples, the tactile feel and the separation of the fiber pieces were evaluated as evaluation of the mechanical strength. The evaluation results are shown in Table 1.

Claims (18)

A first nanofiber formed of a first cellulose-based polymer,
A sheet comprising a second nanofiber formed of a second cellulose polymer having a glass transition point different from the first cellulose polymer by at least 50°C. The method according to claim 1,
Non-woven sheet. The method according to claim 1,
The first cellulose-based polymer is a sheet of first cellulose acylate. The method according to claim 2,
The first cellulose-based polymer is a sheet of first cellulose acylate. The method of claim 3,
The first cellulose acylate is a sheet having an acyl group substitution degree of 2.4 or more and 3.0 or less. The method of claim 4,
The first cellulose acylate is a sheet having an acyl group substitution degree of 2.4 or more and 3.0 or less. The method of claim 3,
The first cellulose acylate is a sheet having an acetyl group as an acyl group. The method of claim 4,
The first cellulose acylate is a sheet having an acetyl group as an acyl group. The method of claim 5,
The first cellulose acylate is a sheet having an acetyl group as an acyl group. The method of claim 6,
The first cellulose acylate is a sheet having an acetyl group as an acyl group. The method according to any one of claims 3 to 10,
The second cellulose-based polymer has a glass transition point lower than that of the first cellulose acylate by at least 50°C. The method of claim 11,
The second cellulose-based polymer is a sheet of any one of second cellulose acylate, nitrocellulose, ethylcellulose, and carboxymethylethylcellulose. The method of claim 12,
The second cellulose acylate sheet is any one of cellulose propionate, cellulose butyrate, and cellulose acetate propionate. The method according to any one of claims 1 to 10,
The mass ratio of the first nanofibers is in the range of 20% or more and 90% or less. The method of claim 11,
The mass ratio of the first nanofibers is in the range of 20% or more and 90% or less. The method of claim 12,
The mass ratio of the first nanofibers is in the range of 20% or more and 90% or less. The method of claim 13,
The mass ratio of the first nanofibers is in the range of 20% or more and 90% or less. In the sheet manufacturing method for manufacturing a sheet by collecting the first nanofiber and the second nanofiber,
A first liquid discharge step of discharging the first solution in a charged state from the first nozzle,
A second liquid discharge step of discharging the second solution in a charged state from the second nozzle,
The first solution and the second solution by attracting the first solution from the first nozzle and the second solution from the second nozzle to a collector charged with a polarity opposite to that of the first solution and the second solution or whose potential is zero 1 A collecting step of collecting the first nanofibers formed of a cellulose-based polymer and the second nanofibers formed of a second cellulose-based polymer,
The first solution includes the first cellulose-based polymer and a solvent,
The second solution includes the second cellulose polymer having a glass transition point different from the first cellulose polymer by at least 50°C, and a solvent.

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