KR102053562B1 - Nano Fibers and Nonwovens - Google Patents

Abstract

An object of this invention is to provide the nanofiber which is excellent in the uniformity of a fiber diameter, and the external appearance at the time of producing a nonwoven fabric, and a nonwoven fabric using the same. The nanofiber of this invention is a nanofiber containing cellulose acylate whose substitution degree becomes 2.75 or more and 2.95 or less.

Description

Nano Fibers and Nonwovens

The present invention relates to nanofibers and nonwoven fabrics using cellulose acylate.

Nanofibers, that is, fibers having a nano order diameter of several nm or more and less than 1000 nm, are used as materials for products such as biofilters, sensors, fuel cell electrode materials, precision filters, and electronic paper. Use development in the field is actively performed.

For example, Patent Document 1 describes, "As a harmful substance removal material which consists of a support body which consists of fibers, a fiber diameter is 10 nm or more and 1 micrometer or less, and the pore diameter of a carrier is 100 micrometers or more and 1 mm or less. [Claim 1], and as the fiber constituting the carrier, fibers and cellulose acylate fibers mainly composed of cellulose esters are described ([Claim 3], [0019] to [0021]).

Patent Document 1: Japanese Unexamined Patent Publication No. 2009-291754

MEANS TO SOLVE THE PROBLEM The present inventors examined the nanofiber produced using the cellulose acylate, and according to the kind of cellulose acylate to be used, when the fiber diameter of the nanofiber produced is inferior to the uniformity of the fiber, and when a nonwoven fabric is produced, It turned out that the external appearance may be inferior.

Therefore, an object of this invention is to provide the nanofiber which is excellent in the uniformity of fiber diameter, and the external appearance at the time of producing a nonwoven fabric, and a nonwoven fabric using the same.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to achieve the said subject, the nanofiber produced using the cellulose acylate which has a specific substitution degree is excellent in the uniformity of fiber diameter, and the external appearance when a nonwoven fabric is produced is also favorable. The present invention was found to be complete.

That is, it discovered that the said subject can be achieved by the following structures.

[1] A nanofiber containing cellulose acylate in which the degree of substitution satisfies the following formula (1).

2.75 ≤ degree of substitution ≤ 2.95 (1)

[2] The nanofiber of [1], wherein the ratio of the average fiber length to the average fiber diameter is 1000 or more.

[3] The nanofiber of [1] or [2] whose average fiber diameter is 50-800 nm.

[4] The nanofiber according to any one of [1] to [3], wherein an average fiber length is 500 µm or more.

[5] The nanofiber according to any one of [1] to [4], wherein the acyl group of the cellulose acylate is an acetyl group.

[6] The nanofiber according to any one of [1] to [5], wherein the amount of hemicellulose in the cellulose acylate is 0.1 to 3.0 mass%.

[7] The nanofiber according to any one of [1] to [6], wherein the viscosity of the solution dissolved in 6% by mass in dichloromethane is 300 mPa · s or more.

[8] A nonwoven fabric composed of the nanofibers according to any one of [1] to [7].

[9] The nonwoven fabric of [8], which is used for a medical filter or a mask.

According to this invention, the nanofiber which is excellent in the uniformity of fiber diameter and the external appearance at the time of producing a nonwoven fabric, and a nonwoven fabric using the same can be provided.

1 is a schematic diagram of an apparatus for manufacturing nanofibers.
2 is a cross-sectional view showing the tip of the nozzle.
FIG. 3: shows the scanning electron microscope (scanning electron microscope) image (magnification: 1800 times) of the nonwoven fabric which consists of nanofibers produced in Example 1. FIG.
4 shows an SEM image (magnification: 1800 times) of a nonwoven fabric made of the nanofibers prepared in Example 2. FIG.
5 shows an SEM image (magnification: 1800 times) of a nonwoven fabric made of the nanofibers prepared in Comparative Example 1. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

Although description of the element | module described below may be made | formed based on typical embodiment of this invention, this invention is not limited to such embodiment.

In addition, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

[Nano Fiber]

The nanofiber of this invention is a nanofiber containing cellulose acylate whose substitution degree satisfy | fills following formula (1).

2.75 ≤ degree of substitution ≤ 2.95 (1)

Here, "nano fiber" in this specification means the fiber whose average fiber diameter measured by the measuring method mentioned later is 10 nm or more and 1000 nm or less.

<Average fiber diameter>

An average fiber diameter means the value measured as follows.

The surface of the nonwoven fabric made of nanofibers is observed on a transmission electron microscope (TEM) or on a scanning electron microscope (SEM).

Observation by an electron microscope image is performed at the magnification selected from 1000 to 5000 times according to the size of the fiber to constitute. However, a sample, observation conditions, and magnification are adjusted so that the following conditions may be satisfied.

(1) One straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect with the straight line X.

(2) A straight line Y perpendicular to the straight line X intersects in the same image, and 20 or more fibers intersect with the straight line Y.

With respect to the electron microscope observation image as described above, at least 20 (that is, at least 40 in total) widths (short diameters of fibers) are read for each of the fibers intersecting the straight line X and the fibers intersecting the straight line Y. In this way, at least 3 sets or more of the above-mentioned electron microscope images are observed, and the fiber diameter of at least 40 * 3 sets (namely, at least 120 pieces) is read.

The average fiber diameter is obtained by averaging the fiber diameters thus read.

<Average fiber length>

The average fiber length of a cellulose fiber means the value measured as follows.

That is, the fiber length of a cellulose fiber can be calculated | required by analyzing the electron microscope observation image used when measuring the average fiber diameter mentioned above.

Specifically, at least 20 (that is, at least 40 in total) fiber lengths are read out for each of the fibers intersected with the straight line X and the fibers intersected with the straight line Y with respect to the electron microscope observation image as described above.

In this way, at least three sets or more of the above-mentioned electron microscope images are observed, and at least 40 * 3 sets (that is, at least 120 pieces) of fiber lengths are read.

The average fiber length is obtained by averaging the fiber lengths thus read.

As described above, the nanofibers of the present invention contain cellulose acylate having a degree of substitution of 2.75 or more and 2.95 or less, which is excellent in uniformity of fiber diameter and improves appearance when a nonwoven fabric is produced.

Although the reason for exhibiting such an effect is not clear in detail, the present inventors guess as follows.

That is, in the present invention, when producing a nanofiber using the field spinning method (hereinafter also referred to as the "electrospinning method"), cellulose acylate having a substitution degree of 2.75 or more and 2.95 or less is used. It is considered that the radiation of the droplets is suppressed by increasing the crystallinity of the rate and the entanglement between the molecules of the cellulose acylate is promoted.

In the nanofiber of the present invention, it is preferable that the ratio of the average fiber length to the average fiber diameter, that is, the aspect ratio (average fiber length / average fiber diameter) is 1000 or more, because it is easy to produce a single nonwoven fabric composed of nanofibers. And, it is more preferable that it is 2500-20000, and it is especially preferable that it is 5000-20000.

In addition, the nanofibers of the present invention preferably have an average fiber diameter of 50 to 800 nm, more preferably 100 to 600 nm because of the high mechanical strength of the fibers and the ease of producing a nonwoven fabric. Moreover, when average fiber diameter is 50-800 nm, effects, such as a size effect, a super molecule arrangement effect, a cell recognition effect, a hierarchical structure effect, can also be anticipated.

Moreover, when the nonwoven fabric is formed, the nanofiber of this invention has an average fiber length of 500 micrometers or more, it is more preferable that it is 1 mm or more, and it is still more preferable that it is 1.5-5 mm.

In the nanofiber of the present invention, the uniformity of the fiber diameter is further improved, and the viscosity of the solution in which 6 mass% is dissolved in dichloromethane (hereinafter, “6%”) is improved because the appearance of the nonwoven fabric becomes better. It is preferable that it is 300 mPa * s or more, It is more preferable that it is 300-1000 mPa * s, It is more preferable that it is 300-900 mPa * s, It is especially preferable that it is 350-800 mPa * s.

The reason why such an effect is obtained is considered to be that when the nanofibers are produced using the electrospinning method, the radiation in the form of droplets can be suppressed, and the skinning of the nozzle can also be suppressed. In particular, the present inventors speculate on the reason why the uniformity of the fiber diameter is improved by controlling the substitution degree of the cellulose acylate and the 6% solution viscosity as follows.

First, in order to form a uniform nanofiber, it is thought that it is important to form a entanglement of a polymer so that a solution may be discharged from a nozzle and a nanofiber will not be cut | disconnected in the process during drying. As a method of controlling the entanglement of the polymer, (a) a method of strengthening the interaction (crystallinity) between molecules (hereinafter abbreviated as "method (a)" in this paragraph), and (b) the length of the molecule It was assumed that the method of lengthening (molecular weight) (hereinafter abbreviated as "method (b)" in this paragraph) is useful. For this reason, in this invention, the substitution degree of cellulose acylate is adjusted in order to perform method (a), and the 6% solution viscosity is adjusted in order to perform method (b). In particular, adjustment of the degree of substitution of cellulose acylate suppresses the formation of rapid entanglement in the late drying, and adjustment of the 6% solution viscosity controls the formation of the entanglement in the initial stage of drying, thereby controlling entanglement throughout the process. Since it can be done, it can be estimated that radiation to a droplet shape can be suppressed and a uniform nanofiber can be produced.

In addition, in this specification, 6% solution viscosity says the value measured by the following procedures.

First, dry cellulose acylate was precisely weighed, and an ostwald viscometer was used for a solution obtained by dissolving 6% by mass of cellulose acylate in a mixed solvent having a mass ratio of dichloromethane and methanol of 91 to 9. The dripping time in degreeC is measured, and it calculates by a following formula.

6% solution viscosity (mPas) = fall time (seconds) x viscometer coefficient

Here, the viscometer coefficient can be obtained by measuring the number of flowing seconds by the same operation as the above solution using the viscometer calibration standard solution, specifically, viscometer coefficient = absolute viscosity (cps) x density of the solution ( 1.235g / cm ³⁾ / density of a standard solution (g / cm ³⁾ / can be obtained by the falling time (in seconds) of the standard solution.

Below, the cellulose acylate contained in the nanofiber of this invention, its synthesis | combining method, and the manufacturing method of the nanofiber of this invention are demonstrated in detail.

[Cellulose acylate]

The cellulose acylate contained in the nanofiber of this invention is cellulose acylate whose substitution degree satisfy | fills following formula (1).

2.75 ≤ degree of substitution ≤ 2.95 (1)

Here, "cellulose acylate" means a part or all of the hydrogen atoms constituting a hydroxyl group of cellulose, i.e., a free hydroxyl group in 2nd, 3rd and 6th positions of a glucose unit bound to β-1,4. Refers to a substituted cellulose ester.

Moreover, "substitution degree" means the substitution degree of the acyl group with respect to the hydrogen atom which comprises the hydroxyl group of cellulose, and can calculate it by comparing the area intensity ratio of the carbon of cellulose acylate measured by ¹³ C-NMR method. have.

<Substituent (acyl)>

As an acyl group, an acetyl group, a propionyl group, a butyryl group, etc. are mentioned specifically ,.

Moreover, only one type (for example, only an acetyl group) may be sufficient as a substituted acyl group, and 2 or more types may be sufficient as it.

In the present invention, in order to improve the uniformity of the fiber diameter and improve the appearance when the nonwoven fabric is produced, when using one kind of acyl group, the acyl group is preferably an acetyl group, and two or more kinds of acyl When using a group, it is preferable that 1 type of acyl groups is an acetyl group. Especially, the aspect in which one type of acyl group is used and an acyl group is an acetyl group is preferable.

<Degree of substitution>

Although the substitution degree of an acyl group is 2.75-2.95 as mentioned above, it is preferable that it is 2.80-2.95, for the reason that the uniformity of a fiber diameter improves more and the external appearance at the time of manufacturing a nonwoven fabric becomes more favorable, it is 2.88-2. It is more preferable that it is 2.95.

In addition, the adjustment method of substitution degree is described in detail in the synthesis method of the cellulose acylate mentioned later.

Ms. Hemicellulose

In this invention, it is preferable that the hemicellulose amount of cellulose acylate is 0.1-3.0 mass%, for the reason that the uniformity of a fiber diameter improves further and the appearance when manufacturing a nonwoven fabric becomes more favorable, it is 0.1-2.0 It is more preferable that it is mass%.

The reason why such an effect is obtained is considered to be that when the nanofibers are produced using the electrospinning method, the crystallinity of the cellulose acylate is increased to suppress the radiation in the droplet form.

In addition, in this specification, the amount of hemicellulose refers to the value computed from the sugar analysis by the Alditol-acetate method (Borchadt, LG; Piper, CV: Tappi, 53, 257-260 (1970)). .

In addition, the adjustment method of hemicellulose amount is described in detail by the synthesis method of the cellulose acylate mentioned later.

<Molecular weight>

Although the number average molecular weight (Mn) of the cellulose acylate contained in the nanofiber of this invention is not specifically limited, From a viewpoint of the mechanical strength of a nanofiber, it is preferable that it is 40000 or more, It is more preferable that it is 40000-150000, 60000- It is more preferable that it is 100000.

Moreover, although the weight average molecular weight (Mw) of cellulose acylate is not specifically limited, From a viewpoint of the mechanical strength of a nanofiber, it is preferable that it is 100000 or more, It is more preferable that it is 100000-500000, It is more preferable that it is 150000-300000. .

In addition, the weight average molecular weight and number average molecular weight in this specification are measured on the following conditions by the gel permeation chromatography (GPC) method.

Device Name: HLC-8220GPC (Tosho)

Type of column: TSK gel Super HZ4000 and HZ2000 (Doso)

Eluent: dimethylformamide (DMF)

Flow rate: 1 ml / min

Detector: RI

Sample concentration: 0.5%

Calibration curve base resin: TSK standard polystyrene (molecular weight 1050, 5970, 18100, 37900, 190000, 706000)

Although content of the cellulose acylate in the nanofiber of this invention is not specifically limited, It is preferable that it is 25 mass% or more with respect to the total mass of a nanofiber, It is more preferable that it is 40-100 mass%, 60-100 mass% Is more preferred.

[Synthesis method of cellulose acylate]

The method for synthesizing cellulose acylate described above is disclosed in Japanese Laid-Open Association (Publication No. 2001-1745, issued March 15, 2001, Invention Association) p. The description of 7-12 is also applicable.

<Raw material>

As a raw material of cellulose, the raw material derived from a hardwood pulp, a softwood pulp, a cotton linter, etc. is mentioned suitably, for example. Especially, the raw material derived from a cotton linter is preferable from the reason that the amount of hemicellulose is small and the nanofiber which improved the uniformity of fiber diameter can be manufactured.

Ms. Hemicellulose

The adjustment of the amount of hemicellulose can be adjusted by refine | purifying the raw material of cellulose by an appropriate method.

For example, the raw material of cellulose is a cooking process by the sulfite cooking method, the kraft cooking method, etc .; Bleaching treatment with oxygen or chlorine bleach; The amount of hemicellulose can be adjusted by performing the purification bleaching process which combined processes, such as an alkali purification process.

Specifically, in the tablet bleaching process which combined the above-mentioned cooking process, bleaching process, and alkali purification process, when performing alkali purification process, it uses the strong alkali aqueous solution of 3-25 mass% at the low temperature of 20-40 degreeC. The method of refine | purifying process is mentioned suitably.

<Activate>

The raw material of cellulose is preferably subjected to a treatment (activation) in contact with an activator prior to acylation.

Specific examples of the activator include acetic acid, propionic acid and butyric acid, and among these, acetic acid is preferred.

It is preferable that the addition amount of an activator is 5%-10000%, It is more preferable that it is 10%-2000%, It is more preferable that it is 30%-1000%.

The addition method can be selected from methods such as spraying, dropping, and dipping.

20 minutes-72 hours are preferable, and, as for activation time, 20 minutes-12 hours are more preferable.

0 degreeC-90 degreeC is preferable, and 20 degreeC-60 degreeC of an activation temperature is more preferable.

Moreover, 0.1-10 mass% of catalysts of acylation, such as a sulfuric acid, can also be added to an activator.

<Acylated>

By reacting the acid anhydride of cellulose with carboxylic acid as Bronsted acid or Lewis acid (see "Physical Dictionary" fifth edition (2000)) as a catalyst, acylating the hydroxyl group of cellulose synthesizes uniform cellulose acylate. It is preferable to carry out, and control of molecular weight is also possible.

The method for obtaining cellulose acylate includes, for example, a method in which two carboxylic acid anhydrides are reacted by mixing or successively adding an acylating agent; A method of using a mixed acid anhydride of two kinds of carboxylic acids (for example, a mixed acid anhydride of acetic acid and propionic acid); A method of reacting with cellulose by forming a mixed acid anhydride (e.g., a mixed acid anhydride of acetic acid and propionic acid) in a reaction system using an acid anhydride of carboxylic acid and another carboxylic acid (for example, an acid anhydride of acetic acid and propionic acid) as a raw material. ; And a method of synthesizing cellulose acylate having a substitution degree of less than 3 and further acylating the remaining hydroxyl group using an acid anhydride or an acid halide.

Moreover, about the synthesis | combination of the cellulose acylate which has a 6th substitution degree, it is described in Unexamined-Japanese-Patent No. 11-5851, Unexamined-Japanese-Patent No. 2002-212338, Unexamined-Japanese-Patent No. 2002-338601, and the like.

(Acid anhydride)

As the acid anhydride of the carboxylic acid, an acid anhydride of a carboxylic acid having 2 to 6 carbon atoms is preferable, and specific examples thereof include acetic anhydride, propionic anhydride, butyric anhydride, and the like.

It is preferable to add 1.1-50 equivalents with respect to the hydroxyl group of a cellulose, It is more preferable to add 1.2-30 equivalents, It is further more preferable to add 1.5-10 equivalents of an acid anhydride.

(catalyst)

It is preferable to use Bronsted acid or Lewis acid as an acylation catalyst, and it is more preferable to use sulfuric acid or perchloric acid.

It is preferable that the addition amount of an acylation catalyst is 0.1-30 mass%, It is more preferable that it is 1-15 mass%, It is more preferable that it is 3-12 mass%.

(menstruum)

It is preferable to use a carboxylic acid as an acylation solvent, It is more preferable to use the carboxylic acid of C2-C7, It is more preferable to use acetic acid, propionic acid, butyric acid, etc. specifically ,. You may use these solvent in mixture.

(Condition)

In order to control the temperature rise by the reaction heat of acylation, it is preferable to cool the acylating agent beforehand.

-50 degreeC-50 degreeC is preferable, -30 degreeC-40 degreeC is more preferable, and -20 degreeC-35 degreeC of an acylation temperature is more preferable.

-50 degreeC or more is preferable, -30 degreeC or more is more preferable, and -20 degreeC or more of the minimum temperature of reaction is more preferable.

0.5 hour-24 hours are preferable, as for acylation time, 1 hour-12 hours are more preferable, and 1.5 hour-10 hours are more preferable.

By controlling the acylation time, the molecular weight can be adjusted.

(Reaction stopper)

After the acylation reaction, it is preferable to add a reaction terminator.

The reaction terminator may be one that decomposes an acid anhydride, and specific examples thereof include water, an alcohol having 1 to 3 carbon atoms, and a carboxylic acid (for example, acetic acid, propionic acid, butyric acid), and water and carboxylic acid. Mixtures of (acetic acid) are preferred.

It is preferable that water is 5-80 mass%, as for the composition of water and a carboxylic acid, it is more preferable that it is 10-60 mass%, and it is more preferable that it is 15-50 mass%.

(corrector)

You may add a neutralizing agent after acylation reaction stops.

Examples of the neutralizing agent include carbonates, hydrogen carbonates, organic acid salts, hydroxides or oxides of ammonium, organic quaternary ammonium, alkali metals, group 2 metals, group 3-12 metals, or group 13-15 elements. Can be. Specifically, carbonate, hydrogen carbonate, acetate or hydroxide of sodium, potassium, magnesium or calcium can be mentioned suitably.

(Partial hydrolysis)

The cellulose acylate obtained by the acylation described above has a total degree of substitution close to approximately 3, but for the purpose of adjusting to a desired degree of substitution (e.g., about 2.8), a small amount of catalyst (e.g., residual sulfuric acid, etc.) In the presence of water) and water, the ester bond can be partially hydrolyzed by holding at 20 to 90 ° C. for several minutes to several days, thereby reducing the degree of acyl substitution of cellulose acylate to a desired degree. In addition, partial hydrolysis can be suitably stopped using a residual catalyst and the said neutralizing agent.

(percolation)

Filtration may be performed in any process from completion of acylation to reprecipitation. It is also preferred to dilute with a suitable solvent prior to filtration.

(Reprecipitation)

The cellulose acylate solution may be mixed with water or an aqueous solution of carboxylic acid (for example, acetic acid, propionic acid, etc.) to reprecipitate. Reprecipitation may be either continuous or batch.

(washing)

It is preferable to wash | clean after reprecipitation. The cleaning can be confirmed by the pH, ion concentration, electrical conductivity, elemental analysis, etc., using water or hot water.

(stabilize)

The cellulose acylate after washing is preferably added with weak alkali (carbonates such as Na, K, Ca, Mg, hydrogen carbonate, hydroxide, oxide).

(dry)

It is preferable to dry the moisture content of cellulose acylate to 50 mass% or less at 50-160 degreeC.

[Manufacturing method of nanofiber]

Although the manufacturing method of the nanofiber of this invention is not specifically limited, For example, the solution in which the cellulose acylate mentioned above is melt | dissolved in a solvent is sent out from the front end of a nozzle at the fixed temperature within the range of 5 degreeC or more and 40 degrees C or less, It can produce by applying a voltage between a solution and a collector, and blowing a fiber from a solution to a collector. The details will be described below with reference to the drawings.

The nanofiber manufacturing apparatus 110 shown in FIG. 1 is for manufacturing the nanofiber 46 from the solution 25 in which cellulose acylate was dissolved in a solvent. The nanofiber manufacturing apparatus 110 includes a spinning chamber 111, a solution supply part 112, a nozzle 13, an integrated part 15, and a power source 65. The radiation chamber 111 accommodates the nozzle 13, a part of the integrated part 15, etc., for example, and is comprised so that sealing is possible, and the solvent gas is prevented from leaking to the exterior. The solvent gas is obtained by evaporation of the solvent of the solution 25.

In addition, a solvent may be single or a mixture which consists of a some compound may be sufficient as it. Examples of the solvent for dissolving cellulose acylate include 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 (NMP), diethyl ether, dioxane, tetrahydro Furan, 1-methoxy-2-propanol, and the like. These may be used independently or may be mixed and used according to the kind of polymer, saturated vapor pressure Ps, the viscosity of the solution 25, etc. In this embodiment, a mixture of dichloromethane and NMP, a mixture of dichloromethane and cyclohexanone, a mixture of acetone and cyclohexanone, and the like are used as the solvent.

The nozzle 13 is arrange | positioned at the upper part in the radiation chamber 111. As shown in FIG. The nozzle 13 is for sending out in the state in which the solution 25 was charged to the first polarity by the power supply 65 as described later. As shown in FIG. 2, the nozzle 13 is comprised from the cylinder, and the solution 25 is sent out from the opening of the front end (it abbreviates as "tip opening" hereafter) 13a. The tip opening 13a is an outlet through which the solution 25 comes out. The nozzle 13 is made of stainless steel having an outer diameter of 0.65 mm and an inner diameter of 0.4 mm, for example, and is cut so that the tip opening edge portion 13b around the tip opening 13a is perpendicular to the barrel direction. The tip opening edge portion 13b, which is this cut surface, is polished flat.

The material of the nozzle 13 may be made of a conductive material such as aluminum alloy, copper alloy, titanium alloy or the like instead of stainless steel. In addition, for the field emission, the solution 25 may come out of the tip opening 13a in a state where a voltage is applied in contact with the metal member at any one place and charged with the first polarity. Therefore, if a voltage is applied at any one location up to the tip opening 13a and charged with the first polarity when exiting the tip opening 13a, the tip opening 13a does not necessarily have to be a conductive material. none.

As shown in FIG. 1, the piping 32 of the solution supply part 112 is connected to the base end of the nozzle 13. The solution supply part 112 is for supplying the above-mentioned solution 25 to the nozzle 13 of the spinning chamber 111. The solution supply part 112 includes the storage container 30, the first temperature controller 133, the pump 31, and the pipe 32. The storage container 30 stores the solution 25. The first temperature controller 133 adjusts the temperature of the stored solution 25 through the storage container 30.

The pump 31 sends the solution 25 from the storage container 30 to the nozzle 13 via the pipe 32. By changing the rotation speed of the pump 31, the flow volume of the solution 25 sent out from the nozzle 13 can be adjusted. In this embodiment, although the flow volume of the solution 25 is set to 3 cm <^3> / hour, a flow volume is not limited to this. By sending the solution 25 to the nozzle 13 by the pump 31, the solution 25 emerges from the tip opening 13a.

In the solution 25 of the storage container 30, the saturated vapor pressure Ps (unit; kPa) of a solvent and the density | concentration C (unit: g / 100cm <^3> ) of cellulose acylate satisfy | fill the following conditions (1). The solution 25 is sent to the nozzle 13 and out of the tip opening 13a in the state which satisfied this condition (1). In this embodiment, in the embodiment, the temperature controller (3) is connected to the pipe 32 and the nozzle 13 so as to be guided from the storage container 30 to the tip opening 13a and out of the tip opening 13a in a state where the condition (1) is satisfied. (Not shown), and guided to the nozzle 13 in a state where the temperature of the solution 25 is maintained at the temperature in the storage container 30 by these temperature controllers, and the tip opening 13a. I am exporting from.

Ps × C≤300 (1)

The saturated vapor pressure Ps (t) of the solvent at the temperature t is obtained by the following formula (2). Here, the number of components of the solvent is n (n is a natural number of 1 or more), and the saturated vapor pressure of the component i (i is a natural number of 1 or more and n or less) at a temperature t is Pi (t) and the solvent of the component i. Let molar fraction in be Xi. When the component number n, the saturated vapor pressure Ps (t) is defined by the following equation. Ps in the above condition (1) obtains the temperature of the solution 25 coming out of the nozzle 13 as the temperature t in the formula (2). In this embodiment, since the temperature of the solution 25 is kept constant until it reaches the front end opening 13a from the storage container 30, the temperature in the storage container 30 is set to the temperature t of Formula (2). The saturated vapor pressure Ps is calculated | required by this. Moreover, concentration C is calculated | required as (Mx100) / V, when the volume of the solution 25 is V (unit; cm <^3> ), and the mass of cellulose acylate is M (unit; g).

It is preferable that saturated vapor pressure Ps exists in the range of 10 kPa or more and 50 kPa or less. When the saturated vapor pressure Ps is 10 kPa or more, the solvent tends to evaporate as compared with the case where the saturated vapor pressure Ps is 10 kPa or less, so that beads of liquid 25 or particles of solid content are not generated. Moreover, when it is 50 kPa or less, since solvent is hard to evaporate compared with the case larger than 50 kPa, solidification by drying of the solution 25 is suppressed.

The first temperature controller 133 adjusts the saturated vapor pressure Ps of the solvent in the solution 25 by adjusting the temperature of the solution 25. In addition, instead of adjusting the temperature of the solution 25, saturated vapor pressure Ps can be adjusted by changing the mixing ratio by making the solvent of the solution 25 into a mixture which consists of several compound.

It is preferable that the temperature of the solution 25 coming out of the nozzle 13 exists in the range of 5 degreeC or more and 40 degrees C or less, and in this embodiment, it is set as 25 degreeC +/- 1 degreeC (in the range of 24 degreeC or more and 26 degrees C or less). have. In order to set the temperature of the solution 25 coming out of the nozzle 13 to the said range, in the storage container 30, it is preferable to adjust and store the solution 25 to the temperature within the range of 5 degreeC or more and 40 degrees C or less. In embodiment, it is 25 degreeC +/- 1 degreeC. When the temperature of the solution 25 is 5 degreeC or more, compared with the case where it is less than 5 degreeC, the solution 25 is hard to gelatinize by low temperature, and the solution 25 stably comes out from the nozzle 13. Moreover, when the temperature of the solution 25 is 40 degrees C or less, compared with the case where it is higher than 40 degreeC, vigorous evaporation (flash) by a solvent exceeds a boiling point hardly occurs, and solidification by drying of the solution 25 is suppressed. do. It is more preferable that the temperature of the solution 25 coming out of the nozzle 13 exists in the range of 10 degreeC or more and 35 degrees C or less, and it is still more preferable to exist in the range which is 15 degreeC or more and 30 degrees C or less.

It is preferable that the viscosity of the solution 25 coming out of the nozzle 13 exists in the range of 1 mPa * s or more and 10 Pa * s or less. The viscosity of the solution 25 can be adjusted by the temperature and the component of the solution 25. When the viscosity is adjusted by the temperature of the solution 25, the temperature of the solution 25 may be adjusted by the first temperature controller 133. Moreover, as a method of adjusting a viscosity with the component of the solution 25, the method of changing the density | concentration C of cellulose acylate, the method of changing a solvent, etc. are mentioned, for example. As a method of changing the solvent, for example, when the solvent is composed of a single substance, changing the kind of the single substance or adding another component to the mixture, or when the solvent is a mixture, at least one of the component and the mixing ratio Change it. The viscosity of the solution 25 coming out of the nozzle 13 is more preferably in the range of 1 mPa · s or more and 5 Pa · s or less, and more preferably in the range of 2 mPa · s or more and 2 Pa · s or less.

It is preferable to provide the nozzle 13 with the cover 134 which covers the front end opening 13a and the 2nd temperature controller 135 for adjusting the temperature inside the cover 134 like this embodiment. . The cover 134 is provided with an opening 134a between the tip opening 13a and the collector 50 for the solution 25 to pass toward the collector 50. By adjusting the internal temperature by the second temperature controller 135, the ambient temperature Ta around the tip opening 13a (around the outlet from which the solution emerges) is adjusted. The circumference is a range that covers at least the Taylor cone 44, for example, preferably within a range of 20 mm from the tip opening 13a. By adjusting this atmospheric temperature Ta, it is preferable to make the difference of the temperature Ts of the solution 25 exiting the front end opening 13a, and atmosphere temperature Ta, ie, Ts-Ta, within -15 degreeC or more and 15 degrees C or less. In the case where Ts-Ta is in the range of -15 ° C or more and 15 ° C or less, evaporation of the solvent is more suitable than in the case outside of this range, so that solidification by drying of the solution 25 is suppressed, and the solution 25 There are no bead-shaped droplets or solid particles. It is more preferable to exist in the range of -10 degreeC or more and 10 degrees C or less, and, as for Ts-Ta, it is still more preferable to exist in the range which is -5 degreeC or more and 5 degrees C or less.

As a method of adjusting the ambient temperature Ta around the front end opening 13a, it is not limited to the method by the cover 134 and the 2nd temperature controller 135 of this embodiment. Instead of the cover 134 and the second temperature controller 135, for example, a gas such as air having a constant temperature is sent to the radiation chamber 111, and the delivery of the entire interior of the radiation chamber 111 is performed. You may adjust atmosphere temperature Ta by adjusting temperature. In addition, in this embodiment, atmospheric temperature Ta is adjusted to 25 degreeC, and the relative humidity of the atmosphere around the front end opening 13a is set to 30% RH.

The concentration C of the cellulose acylate in the solution 25 is preferably in the range of 0.1 g / 100 cm ³ or more and 20 g / 100 cm ³ or less. Thereby, the viscosity of the solution 25 becomes appropriate and the molecules of cellulose acylate are entangled suitably. The concentration C is more preferably 0.5 g / 100 cm ³ or more and 15 g / 100 cm ³ or less, and more preferably 1 g / 100 cm ³ or more and 10 g / 100 cm ³ or less.

The integration part 15 is arrange | positioned below the nozzle 13. The accumulation part 15 has a collector 50, a collector rotating part 51, a support supply part 52, and a support winding part 53. The collector 50 collects the solution 25 from the nozzle 13 as the nanofiber 46, and collects on the support body 60 mentioned later in this embodiment. The collector 50 is comprised with the beltless metal endless belt of stainless steel, for example. The collector 50 is not limited to stainless steel, but may be formed of a material that is charged by application of a voltage by the power supply 65. The collector rotation part 51 is comprised by the pair of rollers 55 and 56, the motor 57, etc. The collector 50 is horizontally spread over a pair of rollers 55 and 56. A motor 57 disposed outside the spinning chamber 111 is connected to the shaft of one roller 55 to rotate the roller 55 at a predetermined speed. By this rotation, the collector 50 moves to circulate between the pair of rollers 55 and 56. In this embodiment, although the moving speed of the collector 50 is set to 10 cm / hour, it is not limited to this.

The support body 60 which consists of a strip | belt-shaped aluminum sheet (aluminum sheet) is supplied to the collector 50 by the support body supply part 52. FIG. The support body 60 in this embodiment is about 25 micrometers in thickness. The support 60 is for obtaining the nonwoven fabric 120 by accumulating (depositing) the nanofibers 46. The support body 60 on the collector 50 is wound up by the support body winding part 53. The support body supply part 52 has the delivery shaft 52a. The support roll 54 is attached to the winding core 23 of the delivery shaft 52a. The support body roll 54 is comprised by the support body 60 being wound up. The support winding portion 53 has a winding shaft 58. The winding shaft 58 is rotated by the motor which is not shown in figure, and winds the support body 60 in which the nonwoven fabric 120 was formed in the winding core 61 to be set. The nonwoven fabric 120 is formed by integrating the nanofibers 46. Thus, this nanofiber manufacturing apparatus 110 has the function of manufacturing the nonwoven fabric 120 in addition to the function of manufacturing the nanofiber 46. It is preferable that the moving speed of the collector 50 and the moving speed of the support 60 be the same so that friction does not occur between both. In addition, the support body 60 may be mounted on the collector 50 to move in accordance with the movement of the collector 50.

In addition, although the nonwoven fabric 120 may be formed by directly integrating the nanofibers 46 on the collector 50, the nonwoven fabric 120 may be affixed and peeled off depending on the material or surface state of the collector 50. There is. For this reason, it is preferable to guide the support body 60 in which the nonwoven fabric 120 is hard to affix on the collector 50 like this embodiment, and to integrate the nanofiber 46 on this support body 60. .

The power supply 65 applies a voltage to the nozzle 13 and the collector 50 to charge the nozzle 13 to the first polarity and to charge the collector 50 to the second polarity opposite to the first polarity. Is a voltage application unit. In this embodiment, although the nozzle 13 is positively charged and the collector 50 is negatively charged, the polarity of the nozzle 13 and the collector 50 may be reversed. By passing through the nozzle 13, the solution 25 charges to the first polarity. In this embodiment, the voltage applied to the nozzle 13 and the collector 50 is 30 kV.

Although the distance L2 of the front end opening 13a of the nozzle 13 and the collector 50 differs in an appropriate value according to the kind of cellulose acylate and a solvent, the mass ratio of the solvent in the solution 25, etc., it is 30 mm or more. The inside of the range of 300 mm or less is preferable, and it is set to 150 mm in this embodiment. Since the distance L2 is 30 mm or more, compared to the case where it is shorter than 30 mm, since the ejection-discharged spinning jet 45 breaks down more firmly by the repulsion by its own charge until it reaches the collector 50, The nanofibers 46 are more surely obtained. In addition, since the solvent is evaporated more reliably by dividing in such a thin manner, the case where the solvent becomes a remaining nonwoven fabric is prevented more reliably. In addition, since the distance L2 is 300 mm or less, since the voltage to apply can be suppressed low compared with the case where it is too long exceeding 300 mm, abnormal discharge is suppressed.

[Non-woven]

The nonwoven fabric of this invention is a nonwoven fabric comprised from the nanofiber of this invention mentioned above, For example, as mentioned above, the nonwoven fabric 120 can be manufactured by the nanofiber manufacturing apparatus 110 shown in FIG.

Moreover, the nonwoven fabric of this invention can also be produced by peeling the deposit of the nanofiber obtained by the electrospinning method from a board | substrate, and heat-processing.

By the curing reaction by heating, the contact portions of the nanofibers are firmly bonded to each other, whereby a non-woven fabric having excellent heat resistance and chemical resistance and high strength is obtained. Moreover, heating conditions are not specifically limited, The conditions heated at 150-250 degreeC for 10 minutes-2 hours are mentioned.

Moreover, the thickness of the nonwoven fabric of this invention can be adjusted suitably by overlapping the quantity which nanofibers deposit, or the nanofiber deposit of a suitable thickness, It is preferable that it is about 30 nm-1 mm, It is more preferable that it is about 100 nm-300 micrometers. .

The nonwoven fabric of the present invention can be used, for example, for applications such as medical filters, masks, heat resistant bag filters, secondary battery separators, secondary battery electrodes, heat insulating materials, filter cloths, and sound absorbing materials.

Among them, cellulose acylate is preferably used as a medical filter or mask from the viewpoint of excellent biocompatibility. Moreover, when using the nonwoven fabric of this invention as a medical filter or a mask, it can expect that a selective resolution will become high. This is because the nanofiber of the present invention has high uniformity of fiber diameter and high uniformity of voids, and thus has excellent physical selective resolution, and cellulose acylate has both hydrophilicity and hydrophobicity, This is because the selection resolution is also high.

Moreover, in the case of a heat resistant bag filter, it can be used as a bag filter for general waste incinerators and industrial waste incinerators.

Moreover, in the case of a secondary battery separator, it can use as a separator for lithium ion secondary batteries.

Moreover, in the case of a secondary battery electrode, it can use as a binder for secondary battery electrode formation by using the deposit of the thermosetting nanofiber before thermosetting. Moreover, the electroconductive nonwoven fabric obtained by disperse | distributing and mixing a powder electrode material to the spinning liquid of this invention, electrospinning it, and thermosetting a deposit can also be used as a secondary battery electrode.

Moreover, in the case of a heat insulating material, it can use as a backup material of a heat resistant brick, and for combustion gas sealing.

Moreover, in the case of a filter cloth, it can use as a filter cloth for micro filters etc. by adjusting the thickness of a nonwoven fabric, etc. suitably, and adjusting the magnitude | size of the hole of a nonwoven fabric. By using the filter cloth, solid content in a fluid such as a liquid or a gas can be separated.

Moreover, in the case of a sound absorption material, it can use as sound absorption materials, such as a wall sound insulation reinforcement and an inner wall sound absorption layer.

Example

The present invention will be described in more detail based on Examples. The materials, usage amounts, ratios, treatment contents, treatment procedures, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the Example shown below.

EXAMPLE 1

The acylating agent and sulfuric acid as a catalyst were mixed with cellulose (raw material: cotton linter), and acylation was carried out while maintaining the reaction temperature at 40 ° C or lower. In addition, as an acylating agent, it can select from acetic acid, acetic anhydride, propionic acid, propionic anhydride, butyric acid, and butyric anhydride individually or in combination of several according to the target substitution degree, In Example 1, acetic acid is used And acylating with an acetyl group (abbreviated as "Ac" in Table 1 below).

After cellulose used as a raw material disappeared and acylation was completed, heating was further continued at 40 degrees C or less, and it adjusted to the desired polymerization degree.

Subsequently, after adding the acetic acid aqueous solution and hydrolyzing the remaining acid anhydride, partial hydrolysis was performed by heating at 60 degrees C or less, and the degree of substitution was adjusted.

The remaining sulfuric acid was neutralized with an excess of magnesium acetate. Cellulose acylate was synthesized by reprecipitation from an aqueous acetic acid solution and further washing in water.

Synthesized cellulose acylate was dissolved in a mixed solvent of 90% dichloromethane and 10% N-methyl-2-pyrrolidone (NMP) to prepare a 4g / 100cm ³ cellulose acylate solution, and FIG. 1 Using the nanofiber manufacturing apparatus 110 shown in the drawing, a nonwoven fabric made of 20 × 30 cm of cellulose acylate nanofibers was produced.

[Examples 2 and 3]

The nonwoven fabric which consists of nanofibers was produced by the method similar to Example 1 except having changed the time of partial hydrolysis and intentionally adjusting the substitution degree by an acetyl group.

EXAMPLE 4

The nonwoven fabric which consists of nanofibers was produced by the method similar to Example 1 except having performed alkaline refining process on the cotton linter of a raw material, and intentionally adjusting the amount of hemicellulose.

[Example 5]

A nonwoven fabric made of nanofiber was produced in the same manner as in Example 1 except that the raw material was changed from a cotton linter to a hardwood pulp.

[Examples 6 and 7]

The nonwoven fabric which consists of nanofibers was produced by the method similar to Example 1 except having changed the reaction time in acylation, and intentionally adjusting the molecular weight.

EXAMPLE 8

The nonwoven fabric which consists of nanofibers was produced by the method similar to Example 1 except having changed the acyl group from the acetyl group to the propionyl group (it abbreviates as "Pr" in Table 1 below).

EXAMPLE 9

A nonwoven fabric made of nanofibers was produced in the same manner as in Example 1 except that the acyl group was changed from an acetyl group to a butyryl group (abbreviated as "Bu" in Table 1 below).

[Comparative Examples 1 and 2]

The nonwoven fabric which consists of nanofibers was produced by the method similar to Example 1 except having changed the time of partial hydrolysis and intentionally adjusting the substitution degree by an acetyl group.

(Comparative Example 3)

A nonwoven fabric made of nanofiber was produced in the same manner as in Example 8 except that the time for partial hydrolysis was changed and the degree of substitution by propionyl group was intentionally adjusted.

(Comparative Example 4)

The nonwoven fabric which consists of nanofibers was produced by the method similar to Example 9 except having changed the time of partial hydrolysis and intentionally adjusting the substitution degree by a butyl group.

About each synthesized cellulose acylate, the degree of substitution, the amount of hemicellulose, the 6% solution viscosity, the number average molecular weight (Mn), the weight average molecular weight (Mw), and the molecular weight distribution (Mw / Mn) were measured by the method described above. did. The results are shown in Table 1 below.

<Evaluation>

Each produced nonwoven fabric was observed using the naked eye and a scanning electron microscope (S-4300, magnification 1800 times, Hitachi Seisakusho Co., Ltd.), and the uniformity of the nonwoven fabric was evaluated in five steps based on the following criteria. The results are shown in Table 1 below. In addition, two or more points can be used practically.

Moreover, the average fiber length and average fiber diameter of nanofiber were measured from the SEM image of each nonwoven fabric by the method mentioned above, and the aspect ratio (average fiber length / average fiber diameter) was computed from these values. The results are shown in Table 1 below.

Moreover, SEM image which observed the nonwoven fabric produced by Examples 1 and 2 and Comparative Example 1 is shown to FIGS.

5 points | pieces: No defect was seen by visual observation and SEM observation.

4 points | pieces: Although a defect is not seen visually, a part with which fiber diameter is nonuniform is seen by SEM.

3 points | pieces: Although a defect is not seen visually, many SEM spots show a nonuniform fiber diameter.

2 points | pieces: Visually, some defects are seen and SEM shows many parts which are non-uniform in fiber diameter.

1 point | piece: Many nonuniformity is seen by both visual observation and SEM.

TABLE 1

When the cellulose acylate whose substitution degree is less than 2.75 was used from the result shown in Table 1, it turned out that uniformity is inferior, regardless of the kind of substituent, the amount of hemicellulose, 6% solution viscosity, etc. (Comparative example 1- 4).

On the other hand, when the cellulose acylate whose substitution degree becomes 2.75 or more and 2.95 or less was used, it turned out that the uniformity of the fiber diameter of a nanofiber is excellent and the external appearance of a nonwoven fabric becomes favorable (Examples 1-9).

In particular, from the comparison of Examples 2, 4, and 5, it was found that the hemicellulose amount was in the range of 0.1 to 3.0, and the uniformity of the fiber diameter of the nanofiber was better, and the appearance of the nonwoven fabric was better.

Moreover, from the contrast of Examples 2, 6, and 7, when the 6% solution viscosity was 300 mPa * s or more, it turned out that the uniformity of the fiber diameter of a nanofiber becomes more favorable and the external appearance of a nonwoven fabric becomes more favorable.

Moreover, from the contrast of Examples 1-3, when substitution degree is 2.80-2.95, it turns out that the uniformity of the fiber diameter of a nanofiber becomes more favorable, and the appearance of a nonwoven fabric becomes more favorable, and substitution degree is 2.88-2.95. It turned out that the uniformity of the fiber diameter of a nanofiber becomes more favorable and the external appearance of a nonwoven fabric becomes more favorable.

13 nozzles
13a tip opening
13b tip opening edge
15 integrated parts
23 winding cores
25 solution
30 storage container
31 pumps
32 piping
44 Taylor Cone
45 spinning jet
46 nanofiber
50 collector
51 Collector Rotator
52 Support Supply
52a transmission shaft
53 support winding
54 support roll
55 roller
56 rollers
57 motor
58 winding shaft
60 support
61 winding core
65 power
110 nanofiber making device
111 radiation chamber
112 Solution supply
120 nonwovens
133 first thermostat
134 cover
134a opening
135 2nd thermostat
P pump
M motor
L2 distance

Claims (9)

Substitution degree satisfy | fills following formula (1), and the viscosity of the solution when 6 mass% of cellulose acylate is melt | dissolved in the mixed solvent which mass ratio of dichloromethane and methanol becomes 91 to 9 is 300 mPa * s or more, Nanofibers containing cellulose acylate.
2.75 ≤ degree of substitution ≤ 2.95 (1) The method according to claim 1,
The nanofiber of which the ratio of average fiber length to average fiber diameter is 1000 or more. The method according to claim 1 or 2,
Nanofiber with an average fiber diameter of 50-800 nm. The method according to claim 1 or 2,
Nanofiber with an average fiber length of at least 500 μm. The method according to claim 1 or 2,
The nanofiber in which the acyl group which the said cellulose acylate has is an acetyl group. The method according to claim 1 or 2,
The nanofiber whose hemicellulose amount of the said cellulose acylate is 0.1-3.0 mass%. delete The nonwoven fabric comprised from the nanofiber of Claim 1 or 2. The method according to claim 8,
Nonwoven fabric used for medical filter or mask.

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