Manufacturing method of bulky fiber sheet and bulky fiber sheet

Abstract

To provide a manufacturing method of a bulky fiber sheet without applying mechanical external force to the fiber sheet.SOLUTION: A manufacturing method includes: applying a cellulose nanofiber dispersion solution to a fiber sheet made in a wet state, the sheet having been subjected to a step of immersing the sheet into water; and then drying the fiber sheet.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a bulky fiber sheet and a bulky fiber sheet. [Background technology]

[0002] Conventionally, a bulky fiber sheet has been known in which unevenness is formed by applying a mechanical external force to a fiber sheet, such as by spraying water on the fiber sheet unwound from a roll to make it moist, and then clamping the fiber sheet between a pair of embossing rolls (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-94067 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention is based on a viewpoint completely different from that of the above-mentioned background art, and has an object to provide a method for producing a bulky fiber sheet without applying an external mechanical force to the fiber sheet. [Means for solving the problem]

[0005] The method for producing a bulky fiber sheet according to the present invention includes the steps of: It is made of paper made by papermaking pulp fibers whose main component is cellulose. This method involves applying a cellulose nanofiber dispersion liquid in a linear, dotted or combination of these patterns to a wet fiber sheet that has been impregnated with water, and then drying the fiber sheet.The areas where the cellulose nanofiber dispersion liquid is applied shrink more than areas where it is not applied, and the difference in shrinkage rate causes the fiber sheet to bend, thereby imparting a bulky uneven shape.

[0006] The bulky fiber sheet according to the present invention has a linear, dotted, or combination thereof pattern, It is made of paper made by papermaking pulp fibers whose main component is cellulose. The surface of the fiber sheet is partially covered with cellulose nanofibers, and the cellulose nanofibers are in at least the surface layer of the fiber sheet. pulp The gaps between the fibers are filled. pulp The cellulose nanofibers are more densely packed than fibers, and the portions covered with the cellulose nanofibers are curved, giving them a bulky, uneven shape. Effect of the Invention

[0007] According to the present invention, a bulky fiber sheet can be produced without applying an external mechanical force to the fiber sheet. [Brief description of the drawings]

[0008] [Figure 1] 1 is a photograph showing the surface of an example of a bulky fiber sheet produced by a bulky fiber sheet production method according to an embodiment of the present invention. [Diagram 2] 3 is a photograph showing the back surface of an example of a bulky fiber sheet produced by the bulky fiber sheet producing method according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a photograph showing a pattern for applying a cellulose nanofiber dispersion when producing the bulky fiber sheet of FIG. 1 and FIG. 2. [Figure 4] 4 is a photograph showing the surface of another example of a bulky fiber sheet produced by the bulky fiber sheet producing method according to an embodiment of the present invention. [Diagram 5] 4 is a photograph showing the back surface of another example of a bulky fiber sheet produced by the bulky fiber sheet producing method according to an embodiment of the present invention. [Figure 6] FIG. 6 is a photograph showing a pattern for applying a cellulose nanofiber dispersion when producing the bulky fiber sheet of FIG. 4 and FIG. 5. [Figure 7] 3 is an SEM image of fine paper used for a fiber sheet in the bulky fiber sheet manufacturing method according to an embodiment of the present invention. [Figure 8] 3 is an SEM image of fine paper in a wet state in the method for producing a bulky fiber sheet according to an embodiment of the present invention. [Figure 9] 1 is an SEM image of a portion of moistened fine paper onto which a cellulose nanofiber dispersion has been applied in a method for producing a bulky fiber sheet according to an embodiment of the present invention. [Figure 10] 1 is an SEM image of the boundary between an area where a cellulose nanofiber dispersion is applied to a moistened fine paper and an area where the cellulose nanofiber dispersion is not applied, in a bulky fiber sheet manufacturing method according to an embodiment of the present invention. [Figure 11] 2 is an SEM image of a portion where a cellulose nanofiber dispersion is applied and dried in the method for producing a bulky fiber sheet according to an embodiment of the present invention. [Figure 12] 2 is an SEM image after drying of a portion where a cellulose nanofiber dispersion liquid is not applied in the method for producing a bulky fiber sheet according to an embodiment of the present invention. [Figure 13] 1 is an SEM image of a boundary between an area where a cellulose nanofiber dispersion is applied and an area where it is not applied after drying in a bulky fiber sheet production method according to an embodiment of the present invention. [Figure 14] FIG. 2 is an SEM image of the areas where a cellulose nanofiber dispersion is applied and the areas where it is not applied, after drying, with the magnification reduced so that these areas can be seen in the field, in the bulky fiber sheet manufacturing method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Preferred embodiments of the present invention will now be described.

[0010] In this embodiment, after a process of impregnating the fiber sheet with water, a bulky fiber sheet is produced by imparting an uneven shape to the fiber sheet without applying an external mechanical force to the fiber sheet.

[0011] Examples of fiber sheets include paper made by bonding vegetable fibers and other fibers, but it is preferable to use paper obtained by papermaking from pulp fibers mainly composed of cellulose. Among them, it is preferable to use Western paper made by machine from a stock containing beaten pulp fibers, more preferably uncoated paper, and particularly preferably fine paper.

[0012] The fiber sheet can be impregnated with water by spraying water on the fiber sheet, immersing the fiber sheet in water, etc. By impregnating the fiber sheet with water, the interfiber bonds are weakened and the fiber sheet becomes wet and swollen with water, and the water content of the fiber sheet can be appropriately adjusted by dehydrating under reduced pressure, etc., as necessary.

[0013] Next, a cellulose nanofiber dispersion is applied to the fiber sheet that has been moistened by the above steps and that has absorbed a necessary and sufficient amount of water to weaken the bonds between the fibers. The cellulose nanofiber dispersion can be applied in any pattern, for example, in a line pattern, a dot pattern, or a combination of these.

[0014] Cellulose nanofibers are generally natural materials derived from plants that have been defibrated into extremely fine fibers with diameters of 3 to 100 nm and an aspect ratio of at least 100. The cellulose nanofiber dispersion used in this embodiment is preferably a dispersion prepared by dispersing cellulose nanofibers in water at a ratio of 0.01 to 15% by weight, more preferably 0.1 to 10% by weight, and particularly preferably 0.5 to 2% by weight.

[0015] According to this embodiment, a cellulose nanofiber dispersion is applied to a wet fiber sheet, and then the fiber sheet is dried, thereby imparting a concave-convex shape to the fiber sheet. The principle of this method will be discussed below with reference to images taken with a scanning electron microscope (SEM images).

[0016] Here, Figure 7 is an SEM image of the high-quality paper used for the fiber sheet, Figure 8 is an SEM image of the high-quality paper in a wet state, Figure 9 is an SEM image of a portion of the wet high-quality paper where cellulose nanofiber dispersion was applied, Figure 10 is an SEM image of the boundary between the portion of the wet high-quality paper where cellulose nanofiber dispersion was applied and the portion where it was not applied, Figure 11 is an SEM image of the portion where cellulose nanofiber dispersion was applied after drying, Figure 12 is an SEM image of the portion where it was not applied after drying, Figure 13 is an SEM image of the boundary between the portion where cellulose nanofiber dispersion was applied and the portion where it was not applied, and Figure 14 is an SEM image of these portions after drying, with the magnification reduced so that the portion where cellulose nanofiber dispersion was applied and the portion where it was not applied could be seen.

[0017] Comparing FIG. 7 with FIG. 8, in the case of wet wood-free paper, the pulp fibers are observed to be raised, and it can be seen that the bonds between the fibers are weakened. Comparing FIG. 9 with FIG. 10, it can be seen that the pulp fibers are covered with cellulose nanofibers in the area where the cellulose nanofiber dispersion was applied, and it is presumed that the cellulose nanofibers have penetrated into the voids in the pulp fiber network. Comparing FIG. 9 to FIG. 13, it can be seen that the cellulose nanofibers after drying are more densely aggregated than the pulp fibers, filling the gaps between the pulp fibers at least in the surface layer. Furthermore, FIG. 14 clearly shows the area where the cellulose nanofiber dispersion was applied and the surface of the fiber sheet, which indicates that the pattern of the cellulose nanofiber dispersion applied is maintained on the surface of the fiber sheet even after the cellulose nanofiber dispersion was applied.

[0018] Based on these findings, it is believed that as the cellulose nanofibers dry, they aggregate more densely than the pulp fibers, and as a result, the pulp fibers are pulled together by them, causing the areas where the cellulose nanofiber dispersion was applied to shrink more than the areas where it was not applied, and that the difference in shrinkage rate causes partial bending of the fiber sheet, giving it an uneven shape.

[0019] In this embodiment, the bulky fiber sheet produced by imparting an uneven shape in this manner has a surface partially covered with cellulose nanofibers, and the cellulose nanofibers are denser than the fibers, filling the gaps between the fibers at least in the surface layer of the fiber sheet. The portion covered with the cellulose nanofibers is bent and has a bulky uneven shape, and is expected to be used as a cushioning material utilizing its bulkiness, as well as for various applications such as decorative materials such as wallpaper and packaging materials. Furthermore, if paper obtained by papermaking pulp fibers mainly composed of cellulose is used as the fiber sheet, in combination with the use of a dispersion prepared by dispersing cellulose nanofibers in water, the environmental load at the time of disposal due to unintended environmental leakage is smaller than that of persistent petroleum-based plastics due to biodegradability, and further, since it is made of a single material mainly composed of cellulose, it can be collected as waste paper and recycled, and the effort of removing foreign matter can be reduced at that time. EXAMPLES

[0020] Next, the present invention will be described in more detail with reference to specific examples.

[0021] [Example 1] The wood-free paper was immersed in water for 2 minutes and then dehydrated under reduced pressure for 30 seconds. Next, a cellulose nanofiber dispersion prepared by dispersing cellulose nanofibers in water at a ratio of 2% by weight was applied to the moistened wood-free paper in a lattice pattern of vertical and horizontal lines as shown in Figure 3. The wood-free paper was then dried to obtain the bulky fiber sheet shown in Figures 1 and 2.

[0022] [Example 2] A bulky fiber sheet as shown in FIGS. 4 and 5 was obtained in the same manner as in Example 1, except that the cellulose nanofiber dispersion was applied in a dotted pattern as shown in FIG.

[0023] Although the present invention has been described above by showing preferred embodiments, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

Claims

1. A method for producing a bulky fiber sheet, characterized in that a cellulose nanofiber dispersion is applied to a wet fiber sheet made of paper obtained by papermaking pulp fibers whose main component is cellulose, in a linear, dotted, or combination of these patterns, and the fiber sheet is then dried, causing the areas coated with the cellulose nanofiber dispersion to shrink more than the areas not coated with the cellulose nanofiber dispersion, and the difference in shrinkage rate causes the fiber sheet to bend, thereby imparting a bulky uneven shape.

2. 2. The method for producing a bulky fiber sheet according to claim 1, wherein the cellulose nanofiber dispersion is prepared by dispersing cellulose nanofibers in water at a ratio of 0.01 to 15% by weight.

3. A bulky fiber sheet, characterized in that the surface of a fiber sheet made of paper obtained by papermaking pulp fibers whose main component is cellulose is partially covered with cellulose nanofibers in a linear, scattered, or combination of these patterns, the cellulose nanofibers are more densely aggregated than the pulp fibers so as to fill the gaps between the pulp fibers in at least the surface layer of the fiber sheet, and the portions covered with the cellulose nanofibers are curved and have a bulky, uneven shape.

Images