JP6772018B2 - A method for producing ultrafine fibers suitable for ultrafineness, a method for producing ultrafine fibers, ultrafine fibers suitable for ultrafineness, and ultrafine fibers. - Google Patents

Description

The present invention relates to a method for producing an ultrafine fiber suitable for ultrafineness, a method for producing an ultrafine fiber using the ultrafine fiber, an ultrafine fiber suitable for ultrafineness, and an ultrafine fiber.

Fibers are used in a variety of applications. Then, for example, various filters such as water purifiers, air purifiers and masks, battery separators for separating positive electrode materials and negative electrode materials, films such as permeable membranes and protective membranes, skin sticking materials, reinforcing materials for various low-grade sheets, etc. As the fiber used in the above field, in order to improve the performance such as the adsorption force, the fiber is subjected to an ultrafine treatment such as beating treatment to increase the specific surface area.

Further, in recent years, a fiber called nanofiber, which has a diameter of 1 to 100 nm and a length of 100 times or more the diameter, is also known. It is known that nanofibers have new characteristics due to their nano-sized diameter, and applications to various fields are being attempted by taking advantage of this. For example, cellulose nanofibers produced from cellulosic fibers are expected to be applied to various fields such as the above-mentioned filters, films, battery separators, reinforcing materials, etc. due to their characteristics such as low density and high strength and larger specific surface area. ..

For example, as a method for obtaining such cellulose nanofibers, the fibers are micronized by mechanical treatment such as a method of ultrafinening with a high-pressure homogenizer or a method of grinding the fibers between rotating grindstones to obtain cellulose nanofibers. A method is known (Japanese Unexamined Patent Publication No. 2010-216021 (Patent Document 1)).

Japanese Unexamined Patent Publication No. 2010-216021

However, for example, as in the method described in Patent Document 1, in order to make the fiber extremely fine, the processing time is long, a large amount of labor and mechanical energy are required, and all the fibers that have undergone the ultrafine treatment are all. However, it is not possible to make the fiber diameter as fine as desired, and there is room for improvement, such as an increase in the production efficiency of the fine fiber.

Therefore, in order to produce ultrafine fibers such as nanofibers and fibers with extremely small fiber diameters, if not nanofibers, it is necessary to produce ultrafine fibers that do not leave the core of the fibers and shorten the processing time required. Therefore, it is desired to realize a method of reducing labor and energy required for producing ultrafine fibers and increasing the production efficiency of ultrafine fibers.

The method for producing an ultrafine fiber suitable for ultrafine according to the present invention is
It is a method of producing ultrafine fibers suitable for ultrafineness by processing cellulosic fibers.
As the processing treatment, a pressure heating treatment in which the cellulosic fiber is moistened and heated under a pressure of atmospheric pressure or higher, and a pressure heating treatment .
A freeze-thaw treatment is performed in which the cellulosic fibers after the pressure heating treatment are frozen and then thawed .

Further, a method for producing an ultrafine fiber suitable for ultrafine according to the present invention is
It is a method of producing ultrafine fibers suitable for ultrafineness by processing cellulosic fibers.
Freezing and thawing treatment in which the cellulosic fibers are moistened, frozen, and then thawed .
A pressure heating treatment is performed in which the cellulosic fibers after the freeze-thaw treatment are heated under a pressure of atmospheric pressure or higher .

Prior to applying the ultrafine treatment to the fiber, the inventor performs a pressure heating treatment in which the fiber is impregnated and heated under a pressure of atmospheric pressure or higher, and the impregnated fiber is frozen. By applying both or one of the freeze-thaw treatment to thaw after the fiber, the fibrillation property of the fiber by the subsequent micronization treatment is effectively enhanced and the fibrillation is effectively promoted. Was found to improve effectively. Furthermore, it was also found that when the pressure heating treatment and the freeze-thaw treatment are performed in combination, the processing performance of the fibers by the subsequent ultrafine treatment is further effectively enhanced. Therefore, according to these configurations, prior to the ultrafine processing of the fiber, the fiber is subjected to both or one of the pressure heating treatment and the freeze-thaw treatment as a processing treatment, and the ultrafineness suitable for the ultrafineness is applied. Manufactures chemical fibers. If the ultrafine fiber is used for the ultrafine fiber having improved processing performance, the ultrafine fiber can be produced as a whole without leaving the thick core portion of the fiber, and the processing time required can be reduced. By shortening the length, the labor and energy required to produce the ultrafine fibers can be effectively reduced, and the production efficiency of the ultrafine fibers can be effectively increased. Further, according to this configuration, it is possible to obtain ultrafine fibers suitable for producing ultrafine fibers suitable for filters, films, battery separators, reinforcing materials and the like.

As one embodiment, it is preferable to immerse the cellulosic fiber in boiling water under atmospheric pressure or higher for a predetermined time as the pressure heating treatment.

According to this configuration, the pressure heating treatment can be performed using an easily available device such as a pressure cooker.

As one embodiment, it is preferable that the boiling water is a boiled acid aqueous solution.

The inventor has found that by using boiling water as boiling water to boil an acid aqueous solution in the above embodiment, the treatment performance in ultrafine fiber thinning is further effectively enhanced. Then, according to this configuration, it is possible to obtain an ultrafine fiber whose processing performance in ultrafineness is more effectively enhanced.

As one embodiment, it is preferable to generate cracks in the cellulosic fibers in advance.

According to this configuration, the water content of the fiber can be increased, and the treatment performance in ultrafineness can be further effectively enhanced by the pressure heating treatment or the freeze-thaw treatment.

The method for producing the ultrafine fiber according to the present invention is
The ultrafine fibers produced by the above method are subjected to an ultrafine treatment to produce ultrafine fibers.

According to this configuration, it is possible to manufacture ultrafine fibers as a whole without leaving a thick core portion of the fibers, and by shortening the processing time required, the labor and energy required for manufacturing are effectively reduced. Moreover, by using the ultrafine fibers whose production efficiency of the ultrafine fibers is effectively enhanced, the ultrafine fibers can be produced extremely efficiently.

As one embodiment, it is preferable that the average fiber diameter of the obtained ultrafine fibers is 1 to 1000 nm.

According to this configuration, it is possible to obtain ultrafine fibers capable of producing high-performance filters, films, battery separators, reinforcing materials and the like.

The ultrafine fiber suitable for ultrafine according to the present invention is
An ultrafine fiber produced by processing a cellulosic fiber and suitable for ultrafineness.
As the processing treatment, a pressure heating treatment in which the cellulosic fiber is moistened and heated under a pressure of atmospheric pressure or higher, and a pressure heating treatment .
This is an ultrafine fiber subjected to a freeze-thaw treatment in which the cellulosic fiber after the pressure heating treatment is frozen and then thawed.
Further, the ultrafine fiber suitable for ultrafine according to the present invention is
An ultrafine fiber produced by processing a cellulosic fiber and suitable for ultrafineness.
As the processing treatment , a freeze-thaw treatment in which the cellulosic fiber is moistened, then frozen, and then thawed , and
The ultrafine fiber is subjected to a pressure heating treatment in which the cellulosic fiber after the freeze-thaw treatment is heated under a pressure of atmospheric pressure or higher .

That is, by subjecting the fibers to pressure heating treatment and freeze-thaw treatment as in these configurations, ultrafine fibers suitable for ultrafineness can be obtained. Specifically, FIGS. 15 to 17 (fibers after beating, FIG. 15 shows fibers subjected to pressure heating treatment as processing treatment, and FIG. 16 shows pressure heating treatment as processing treatment. As shown in (Fig. 17 shows fibers that have not been processed), the fibers that have been subjected to freeze-thaw treatment and that have undergone pressure heating treatment in FIG. 15 are fibers that have not been processed in FIG. Many cracks can be confirmed in the cross section of the fiber, and the fiber is divided into finer fibers from the surface of the fiber. That is, it can be seen that the fiber is finely torn along the cracks generated inside the fiber. Further, it can be seen that in the fibers subjected to the pressure heating treatment and the freeze-thaw treatment in FIG. 16, the fibers are torn more finely than in FIG. 15 along the cracks generated inside the fibers. As described above, it can be seen that the processing process according to this configuration causes fine cracks inside the fibers, and the fibers are finely split along the fine cracks. That is, the ultrafine fibers subjected to the above processing treatment have fine cracks inside the fibers, and as a result, the production efficiency of the ultrafine fibers is improved.
By performing the above processing treatment, it is possible to obtain an ultrafine fiber having a novel and characteristic structure in which fine cracks are generated inside the fiber, but the fine cracks generated inside the fiber can be obtained. It is extremely difficult to specifically specify the structure, etc. Therefore, the ultrafine fibers according to this configuration are specified only by the content of the processing treatment (pressurization heating treatment or freeze-thaw treatment) applied to the fibers. It is specified in.

The ultrafine fibers according to the present invention are
It is an ultrafine fiber produced by subjecting the ultrafine fiber according to the present invention to a beating treatment.

As described above, the ultrafine fiber according to the present invention has a novel and characteristic structure in which fine cracks are generated inside the fiber, and according to such an ultrafine fiber, chemical treatment is performed. The ultrafine fibers can be easily obtained without causing modification to the fibers. Such ultrafine fibers are specified for the first time by being produced by subjecting the ultrafine fibers to a beating treatment, and the above-mentioned configuration makes it possible to obtain ultrafine fibers in which the cost required for production is reduced. ..

Enlarged view of the sample in Example 1 Enlarged view of the sample in Example 2 Enlarged view of the sample in Example 3 Enlarged view of the sample in Example 4 Enlarged view of the sample in Comparative Example 1 Enlarged view of the sample in Comparative Example 2 Enlarged view of the sample in Example 5 Enlarged view of the sample in Comparative Example 3 Enlarged view of the sample in Example 6 Enlarged view of the sample in Example 7 Enlarged view of the sample in Comparative Example 4 Enlarged cross-sectional view of the fiber in Example 6 Enlarged cross-sectional view of the fiber in Example 7 Enlarged cross-sectional view of the fiber in Comparative Example 4 Enlarged cross-sectional view of the fiber after beating in Example 6 Enlarged cross-sectional view of the fiber after beating in Example 7 Enlarged cross-sectional view of the fiber after beating in Comparative Example 4 The figure which shows the processing flow and the evaluation flow after processing The figure which shows the specific tensile strength of the ultrafine fiber which concerns on this Embodiment

A method for producing an ultrafine fiber suitable for ultrafineness, a method for producing an ultrafine fiber, an ultrafine fiber suitable for ultrafineness, and an embodiment of the ultrafine fiber according to the present invention will be described in detail. In the method according to the present embodiment, the fibers are processed to produce ultrafine fibers suitable for ultrafineness. More specifically, as the processing treatment, either a pressure heating treatment in which the fibers are moistened and heated under a pressure of atmospheric pressure or higher, and a freeze-thaw treatment in which the fibers are moistened and then frozen and then thawed are performed. One of these is performed to produce an ultrafine fiber having improved processing performance in ultrafineness (hereinafter, simply referred to as processing performance). Then, the produced ultrafine fibers are subjected to an ultrafine treatment to produce ultrafine fibers. Hereinafter, this method will be described in more detail.

〔fiber〕
Cellulose-based fibers can be used as the fibers used in this embodiment. Cellulose-based fibers are not particularly limited, and examples thereof include natural cellulosic fibers such as cotton, hemp, and squirrel, wood chemically treated pulp such as kraft pulp and sulfite pulp, semi-chemical pulp, used paper, and recycled pulp thereof. In addition to the cellulosic fibers, the fibers are not particularly limited as long as they are fibers that are made extremely fine by mechanical treatment.

Further, the fiber used in the present embodiment is originally processed (pressurized) in a state where scratches, vertical streaks, vertical stitches, etc. are present on the fiber surface and water is permeated into the scratches, vertical streaks, vertical stitches, etc. Treatment performance can be improved by performing warm treatment or freeze-thaw treatment), but prior to this processing treatment, cracks (cracks, cracks, tears, scratches, vertical streaks, etc.) are generated in the fibers in advance. And more suitable. As a result, the water content of the fiber can be increased, and the treatment performance can be improved by the pressure heating treatment or the freeze-thaw treatment. For example, the crack can be generated by a known beating process. Specifically, known mechanical processing equipment such as a beater, a refiner, a kneader, a sand grinder, a high-pressure homogenizer, a rotary mill, and a jet mill can be used.

[Pressure heating process]
In the pressure heating process, the fibers are moistened and heated under atmospheric pressure or higher. By treating at high temperature and high pressure, the water permeating the fiber surface and the inside expands, and the fiber processing performance can be improved. If the fibers are cracked in advance, water can easily enter the inside of the fibers, and the processing performance of the fibers can be further improved. This pressure heating treatment can be performed by a general autoclave treatment using water, for example, by immersing the fibers in boiling water under atmospheric pressure or higher for a predetermined time. This can be done using a pressure cooker, a pressure cooker, or the like. In addition to this, instead of immersing the fibers in boiling water to heat them, for example, the fibers moistened under atmospheric pressure or higher may be heated by a heater, and the pressure is applied. The specific method of the temperature treatment is not particularly limited as long as the fibers are moistened and heated under a pressure of atmospheric pressure or higher, and the treatment time, treatment temperature, and treatment pressure are not particularly limited. The pressure in the pressure heating treatment is preferably 100 kPa or more, for example. The upper limit is not particularly limited and may be any pressure, but for example, from the viewpoint of processing safety and ease of execution, 1500 kPa or less is preferable. Further, after the pressure heating treatment, the pressure applied to the fibers may be gradually reduced, but after the pressure heating treatment, the pressure applied to the fibers is such that the fibers are moved from under high pressure to atmospheric pressure at once. When the pressure is reduced instantaneously, the processing performance of the fiber can be further improved, and by performing the ultrafine treatment, the fiber can be further divided and defibrated.

When the fibers are immersed in boiling water under atmospheric pressure or higher for a predetermined time, the boiling water is preferably a boiling acid aqueous solution. It is considered that the acid increases the permeability of water to the fibers and enhances the effect of improving the treatment performance. The acid used is not particularly limited, and examples thereof include glycolic acid having a small molecular weight and particularly excellent permeability. Further, even when boiling water is not used, the fibers may be hydrated with an acid aqueous solution. For example, when an aqueous glycolic acid solution is used, its concentration is not particularly limited, but it is preferably in the range of 1 to 20 wt% in consideration of the defibration property of the fiber and the ease of tearing of the fiber, and further, 1 to 20 wt%. 10 wt% is more preferable. This is because the higher the concentration of the aqueous glycolic acid solution, the lower the fiber strength, the easier it is for the fiber itself to tear in the lateral direction (diameter direction) during the processing, and the shorter the fiber length. The range of suitable concentration can be appropriately changed depending on the temperature and pressure conditions for performing the pressure heat treatment and the like.

[Freeze-thaw treatment]
In the freeze-thaw treatment, the fibers are moistened, frozen, and then thawed. By freezing the water-containing fibers, the water contained in the fibers freezes and expands, which can improve the processing performance of the fibers. Similarly, if the fibers are cracked in advance, water can easily enter the inside of the fibers, and the processing performance of the fibers can be further improved. Examples of the method of freezing the fibers include a method of putting the hydrated fibers in a heat insulating container and introducing liquid nitrogen into the heat insulating container. However, the present invention is not limited to this, and the method is not limited as long as the hydrated fiber can be frozen, such as putting the hydrated fiber in a freezer and freezing it or freezing it with dry ice. Is not particularly limited. Then, after the fibers are frozen, the fibers are thawed (thawed) by a usual method such as leaving at room temperature. In addition, in order to accelerate melting, it may be heated by a known heater or the like.

As the processing treatment, both the pressure heating treatment and the freeze-thaw treatment may be performed, or only one of them may be performed. Further, when both are performed, the pressure heating treatment may be performed and then the freeze-thaw treatment may be performed, or the freeze-thaw treatment may be performed and then the pressure heating treatment may be performed.

[Extra-fine processing]
After producing the ultrafine fibers, the ultrafine fibers are subjected to an ultrafine treatment to produce the ultrafine fibers. The degree to which the fibers are made ultrafine may be set according to the intended use and is not particularly limited, but for example, it is preferable that the average fiber diameter of the obtained ultrafine fibers is 1 to 1000 nm. Further, nanofibers may be obtained by performing ultrafine treatment until the average fiber diameter becomes 1 to 100 nm. Since the processing performance of the ultrafine fibers is extremely improved by undergoing the above processing treatment, the time required for ultrafinening the fibers to the target fiber diameter can be shortened, and the processing time required can be shortened. As a result, the labor and energy required are reduced, and the production efficiency of such ultrafine fibers is increased. A known method can be used as the ultrafine treatment, and the treatment is not particularly limited. For example, it may be carried out by the above-mentioned known beating processing means. Specifically, known mechanical processing equipment such as a beater, a refiner, a kneader, a sand grinder, a high-pressure homogenizer, a rotary mill, and a jet mill can be used. Further, since the processing performance of the ultrafine fibers in the present embodiment is extremely improved, it can be efficiently beaten by human power such as a method of hitting or rubbing the fibers with a hammer or a method of rubbing the fibers with a grindstone. The fibers can be made very fine.

[Use]
The ultrafine fibers produced as described above can be used in any available application without particular limitation.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

[Example 1]
In the first embodiment, only the pressure heating treatment is performed as the processing treatment. Specifically, cellulose raw cotton was used as a raw material, and the fibers were cracked in advance by a known appropriate beating treatment. As a pressure heating treatment, the cellulose raw cotton was immersed in boiling water for 60 minutes under a pressure of 144 kPa using a pressure cooker. Then, with the cellulose raw cotton moistened, as an ultrafine treatment, a grindstone (particle size # 240) is used to sandwich the moistened cellulose raw cotton between the grindstones, and while pressing the grindstone with both hands, 10 reciprocations in each of the vertical and horizontal directions and a circle are made. A beating process was performed in which the grindstone was rubbed 20 times each in a clockwise and counterclockwise direction as drawn. FIG. 1 shows a photograph taken by magnifying the sample of Example 1 which was dried by a dryer after the ultrafine treatment at a magnification of 1000 times. An electron microscope was used for taking photographs shown in FIG. 1 and the other figures below.

[Comparative Example 1]
As Comparative Example 1, a product obtained by performing only the same ultrafine processing as in Example 1 without processing is shown. FIG. 5 shows a photograph taken by magnifying the sample of Comparative Example 1 which was dried by a dryer after the ultrafine treatment at a magnification of 1000 times.

Comparing FIGS. 1 and 5, in FIG. 5, those having a fiber diameter of more than 10 μm remain as they are without being defibrated, but in FIG. 1, they are effectively defibrated by a slight ultrafine treatment. It can be seen (see, for example, the arrow in FIG. 1). As described above, it can be seen that the processing performance of the fiber after the pressure heating treatment as the processing treatment is enhanced.

[Example 2]
In Example 2, only the freeze-thaw treatment is performed as the processing treatment. Specifically, cellulose raw cotton was used as a raw material. As a freeze-thaw treatment, liquid nitrogen was introduced into a Dewar flask, and water-impregnated cellulose raw cotton was immersed therein for 5 minutes and then naturally thawed at room temperature. Then, in a state where the raw cellulose cotton was moistened, the same ultrafine treatment as in Example 1 was performed. FIG. 2 shows a photograph taken by magnifying the sample of Example 2 which was dried by a dryer after the ultrafine treatment at a magnification of 1000 times.

Comparing FIG. 2 and FIG. 5 (Comparative Example 1), in FIG. 5, fibers having a fiber diameter of more than 10 μm remain as they are without being defibrated, but in FIG. 2, for example, fibers indicated by arrows in the figure are used. It can be seen that the degree of fiber defibration is higher than in FIG. As described above, it can be seen that the processing performance of the fiber after the freeze-thaw treatment as the processing treatment is enhanced.

Further, when FIG. 1 and FIG. 2 are compared, the degree of fiber defibration is higher in FIG. 1, and from this, when the pressure heating treatment and the freeze-thaw treatment are performed independently, the pressure is increased. It can be said that the heating treatment has a higher effect of improving the processing performance of the fiber.

[Example 3]
In Example 3, both the pressure heating treatment and the freeze-thaw treatment are performed as the processing treatment. Specifically, cellulose raw cotton was used as a raw material in the same manner as described above, and the fibers were cracked in advance by a known appropriate beating treatment. Then, after performing the same pressure heating treatment as in Example 1, the same freeze-thaw treatment as in Example 2 was performed. Then, in a state where the raw cellulose cotton was moistened, the same ultrafine treatment as in Example 1 was performed. FIG. 3 shows a photograph taken by magnifying the sample of Example 3 which was dried by a dryer after the ultrafine treatment at a magnification of 1000 times.

Comparing FIG. 3 and FIG. 5 (Comparative Example 1), it can be seen that in FIG. 3, the defibration is effectively performed by a slight ultrafine processing. As described above, it can be seen that the processing performance of the fibers after the pressure heating treatment and the freeze-thaw treatment as the processing treatment is enhanced.

Further, for comparison, in FIG. 6, as Comparative Example 2, a sample according to a prior art that has been sufficiently subjected to an ultrafine treatment without processing (so to speak, an additional sufficient ultrafineness with respect to the sample of Comparative Example 1). A photograph of the treated sample) taken at a magnification of 1000 times is shown. Comparing FIGS. 3 and 6, it can be seen that the defibration in FIG. 3 is more effective, and it can be confirmed that the excellent processing performance in Example 3 is improved.

Further, when FIG. 3 is compared with FIGS. 1 and 2, it can be seen that FIG. 3 has the highest degree of fiber defibration. From this, it can be seen that the fiber treatment performance can be further improved by performing both the pressure heating treatment and the freeze-thaw treatment.

[Example 4]
In Example 4, basically the same treatment as in Example 1 was carried out, but in the pressure heating treatment, the cellulose raw cotton was immersed in boiling water in which an aqueous glycolic acid solution (concentration: 10 wt%) was boiled. FIG. 4 shows a photograph taken by magnifying the sample of Example 4 which was dried by a dryer after the ultrafine treatment at a magnification of 1000 times.

As is clear from FIG. 4, it can be seen that the fibers are effectively defibrated by a slight ultrafine treatment. Comparing FIG. 1 (Example 1) with FIG. 4, it can be said that the fiber shown in FIG. 4 has a higher degree of defibration. From this, it can be seen that in the pressure heating treatment, the fiber treatment performance can be further improved by using boiling water obtained by boiling an acid aqueous solution (glycolic acid aqueous solution).

[Example 5]
In Example 5, the state of the sample before the ultrafine treatment is shown. Specifically, after the cellulose raw cotton was beaten, only the so-called core portion which was not fibrillated was separated from the fiber after the beating treatment, and the core portion was used as a sample. Further, in this sample, the fibers were preliminarily cracked by a known appropriate beating treatment in the same manner as described above. Then, in the same manner as in Example 4, in the pressure heating treatment, the sample was immersed in boiling water in which an aqueous glycolic acid solution (concentration: 5 wt%) was boiled for 30 minutes under a pressure of 144 kPa using a pressure cooker. I let you. FIG. 7 shows a photograph taken by magnifying the sample of Example 5 which was dried by a dryer after the pressure heating treatment at a magnification of 5000 times.

Comparing FIG. 7 with FIG. 8 showing a photograph of the core portion of Example 5 before the pressurization heating treatment (Comparative Example 3) taken at a magnification of 5000 times, the pressurization of FIG. 8 is performed. From the state before the heat treatment, it can be seen in FIG. 7 that the core portion of the fiber is effectively defibrated. As described above, it can be seen that the processing performance of the fiber is enhanced by performing the pressure heating treatment.

[Examples 6 and 7, Comparative Example 4]
Further, an example in which the above processing treatment is performed on the lyocell fiber having a fineness of 1.7 dtex will be described. In the following, as a processing treatment, the lyocell fiber is subjected to a pressure heating treatment in which water heated to 165 ° C. is impregnated for 1 hour under a pressure of 700 kPa using an autoclave device. Then, the same pressure heating treatment as in Example 6 and then the same freeze-thaw treatment as in Example 2 was referred to as Example 7, and the one not subjected to the processing treatment was described as Comparative Example 4. To do.

First, the state of the fiber after the processing is shown with reference to FIGS. 9 to 11. 9 to 11 are photographs of lyocell fibers of each example magnified 1000 times, FIG. 9 shows lyocell fibers of Example 6, FIG. 10 shows Example 7, and FIG. 11 shows lyocell fibers of Comparative Example 4. Comparing FIGS. 9 to 11, in FIGS. 9 and 10 showing the processed fibers, vertical stripes extending in the length direction are formed on the surface of each fiber, and the surface is divided into nano-sized ultrafine fibers. You can see that it is saying. Further, when FIG. 9 and FIG. 10 are compared, it can be seen that in FIG. 10, which shows the fibers further subjected to the freeze-thaw treatment as the processing treatment, the fibers are further divided into ultrafine fibers.

Next, the influence of the processing on the fibers will be described with reference to FIGS. 12 to 17. 12 to 14 are photographs of the cross section of the lyocell fiber of each example magnified 5000 times, FIG. 12 shows the cross section of the lyocell fiber of Example 6, FIG. 13 shows the cross section of Example 7, and FIG. 14 shows the cross section of the lyocell fiber of Comparative Example 4. Comparing FIGS. 12 to 14, it can be seen that the fibers shown in FIGS. 12 and 13 that have been processed have fine holes in the cross section. It can be seen that this hole corresponds to a crevice in the fiber, that is, in the processed fiber, a large number of cracks are generated inside the fiber along the length direction of the fiber.

FIGS. 15 to 17 show a state after further beating the fibers (about 1 hour with a beater), and show a cross section of the lyocell fibers of each example after the beating treatment magnified 5000 times. FIG. 15 shows a cross section of a lyocell fiber of Example 6, FIG. 16 shows a cross section of Example 7, and FIG. 17 shows a cross section of a lyocell fiber of Comparative Example 4. Comparing FIGS. 15 to 17, in FIG. 15, which shows the fibers subjected to the pressure heating treatment as the processing treatment, more cracks can be confirmed in the cross section of the fibers as compared with FIG. 17 showing the fibers not subjected to the processing treatment. Also, it can be seen that the surface of the fiber is divided into finer fibers. That is, it can be seen that the fiber is finely torn along the cracks generated inside the fiber. Further, in FIG. 16 showing the fibers subjected to the pressure heating treatment and the freeze-thaw treatment as the processing treatment, the fibers are torn more finely than in FIG. 15 along the cracks generated inside the fibers. Recognize. As described above, it can be seen that the processing of the present embodiment causes fine cracks inside the fibers, and the fibers are finely split along the fine cracks. That is, it can be seen that the production efficiency of the ultrafine fibers is enhanced by performing the processing treatment due to the occurrence of fine cracks inside the fibers.

Next, using Table 1, the strength of the ultrafine fibers produced from the processed fibers will be described. Table 1 shows the area of each sheet after each of the fibers of Examples 6 and 7 and Comparative Example 4 was beaten with a beater at a load of 2 kg for 6 hours as an ultrafine treatment. The data of quantity (weight per unit area), thickness, density, and tensile strength and specific tensile strength obtained by performing a tensile test are shown.

As is clear from Table 1, the fibers of Examples 6 and 7 that have been processed have a higher specific tensile strength than the fibers of Comparative Example 4 that have not been processed. In particular, the fibers of Example 7 which were subjected to freeze-thaw treatment in addition to pressure heating treatment as processing treatment had the specific tensile strength more than twice as high as that of the fibers of Comparative Example 4. It has been found that when each fiber becomes extremely thin, the strength is increased by increasing the number of constituent fibers per unit volume, and the fibers of Examples 6 and 7 are replaced with the fibers of Comparative Example 4. In comparison, it can be seen that ultrafine fiber is progressing. By producing the ultrafine fibers using the ultrafine fibers processed in this way, the ultrafine fibers can be produced extremely efficiently, and as a result, the strength of the produced ultrafine fibers is increased. It is also possible.

Furthermore, the test results of the specific tensile strength of the sheet made from paper using the ultrafine fibers obtained by beating the ultrafine fibers that have been subjected to processing such as pressure heating treatment and freeze-thaw treatment are shown. It is shown with reference to FIGS. FIG. 18 shows an experimental sample preparation method and an evaluation flow performed to confirm the effect of the processing, and in FIG. 18 (and FIG. 19), “G” indicates a lyocell fiber in which no pretreatment was performed. As shown in FIG. 18, the lyocell fiber is directly subjected to the beating process described later. "GA" is a lyocell fiber that has been subjected to pressure heating treatment and beating treatment. Specifically, it is an autoclave (capacity 120 liters, steam heating type) as pressure heating treatment (high temperature / high pressure treatment). It is a lyocell fiber after being immersed in boiling water for 1 hour under a pressure of 0.6 MPa. "GA-N1" and "GA-N2" are lyocell fibers that have been beaten by performing a pressure heating treatment and a freeze-thaw treatment, and are specifically referred to as "GA". After performing the same pressure heating treatment, in "GAN1", as a freeze-thaw treatment (freezing treatment), liquid nitrogen is used and left at a temperature of -196 ° C. for 10 minutes and then thawed. , "GA-N2" was subjected to a freeze-thaw treatment using a domestic freezer and left at a temperature of −15 ° C. for 1 hour before thawing. Then, beating treatment with a beater is performed for each lyocell fiber for a predetermined time (1 hour, 2 hours, and 4 hours), and for each treatment time (1 hour, 2 hours, and 4 hours), Kumagai Riki Kogyo Using a square sheet machine manufactured by Co., Ltd., sheets having a size of 250 mm × 250 mm and a basis weight of 20 g / m ² were prepared, and the physical properties of each sheet were measured. Tables 2 to 5 show the physical property values of each sheet.

FIG. 19 shows the results of tensile tests performed on each sheet, and shows the relationship between the processing time and the specific tensile strength (N / m · g). In addition, as the ultrafineness progresses, the specific tensile strength also increases as described above, that is, the specific tensile strength has a correlation with the fiber diameter of the sheet, and is an index of how much the ultrafineness has progressed. Is the value.

As is clear from FIG. 19, the fibers (“GA”, “GA-N1”, “GA-N2”) that have been processed by pressure heating treatment or freeze-thaw treatment are The specific tensile strength is clearly higher than that of the unprocessed fiber (“G”). That is, it is shown that the fibers (“GA”, “GA-N1”, “GA-N2”) that have been processed are more ultrafine. In addition, fibers that are only subjected to pressure heating treatment (“GA”) and fibers that are subjected to freeze-thaw treatment in addition to pressure heating treatment (“GAN1”, “GA”). -N2 "), the specific tensile strength at the time of the beating treatment for 2 hours was clearly higher in the fibers subjected to the freeze-thaw treatment in addition to the pressure heating treatment, and the fibers were frozen. It can be seen that the ultrafineness is progressing by also performing the melting treatment. The specific tensile strength of "GA-N1" and "GA-N2" decreased after 4 hours, but this was due to excessive beating treatment and the fibers in the length direction. It is considered that this is due to the fact that the fibers have been shortened due to tearing. However, this shortening of the fibers means that the fibers have become extremely fine by the time the 4-hour beating process is completed, and the force applied to make the fibers extremely fine works to tear the fibers. It can be said that this is due to the fact that it reflects the high production efficiency of ultrafine fibers produced by "GA-N1" and "GA-N2".

The beater used in this evaluation experiment was Niagara Falls (TAPPI standard type) manufactured by Kumagai Riki Kogyo Co., Ltd., but the beating by the beater in this evaluation is an example of the beating method, and the device used for the beating process is Not limited to beaters. Moreover, the purpose of this evaluation experiment is to show that the processing method of the present invention has a remarkably excellent effect in improving beating characteristics and obtaining ultrafine fibers by comparing with a sample without processing. It is in. Therefore, the apparatus used for the beating process and the beating conditions are appropriately selected according to the intended use.

It should be understood that the embodiments disclosed herein are exemplary in all respects and the scope of the invention is not limited thereto. Those skilled in the art will be able to easily understand that modifications can be made as appropriate without departing from the spirit of the present invention. Therefore, another embodiment modified without departing from the spirit of the present invention is naturally included in the scope of the present invention.

The present invention can be used, for example, to micronize fibers.

Claims (9)

It is a method of producing ultrafine fibers suitable for ultrafineness by processing cellulosic fibers.
As the processing treatment, a pressure heating treatment in which the cellulosic fiber is moistened and heated under a pressure of atmospheric pressure or higher, and a pressure heating treatment.
A method of performing a freeze-thaw treatment in which the cellulosic fibers after the pressure heating treatment are frozen and then thawed. It is a method of producing ultrafine fibers suitable for ultrafineness by processing cellulosic fibers.
Freezing and thawing treatment in which the cellulosic fibers are moistened, frozen, and then thawed.
A method of performing a pressure heating treatment in which the cellulosic fibers after the freeze-thaw treatment are heated under a pressure of atmospheric pressure or higher. The method according to claim 1 or 2, wherein as the pressure heating treatment, the cellulosic fibers are immersed in boiling water under atmospheric pressure or higher for a predetermined time. The method according to claim 3, wherein the boiling water is a boiling acid aqueous solution. The method according to any one of claims 1 to 4, wherein the cellulosic fiber is cracked in advance. A method for producing ultrafine fibers by subjecting the ultrafine fibers produced by the method according to any one of claims 1 to 5 to an ultrafine treatment. The method according to claim 6, wherein the average fiber diameter of the obtained ultrafine fibers is 1 to 1000 nm. An ultrafine fiber produced by processing a cellulosic fiber and suitable for ultrafineness.
As the processing treatment, a pressure heating treatment in which the cellulosic fiber is moistened and heated under a pressure of atmospheric pressure or higher, and a pressure heating treatment.
An ultrafine fiber subjected to a freeze-thaw treatment in which the cellulosic fiber after the pressure heating treatment is frozen and then thawed. An ultrafine fiber produced by processing a cellulosic fiber and suitable for ultrafineness.
As the processing treatment, a freeze-thaw treatment in which the cellulosic fiber is moistened, then frozen, and then thawed, and
An ultrafine fiber subjected to a pressure heating treatment in which the cellulosic fiber after the freeze-thaw treatment is heated under a pressure of atmospheric pressure or higher.