JP2018204125A - Method for producing cellulose nanofiber - Google Patents

Abstract

To provide a method for producing a cellulose nanofiber, in which the cellulose nanofiber can be produced in a resource-saving and in a short period of time.SOLUTION: A method for producing a cellulose nanofiber of this invention includes the steps of: recovering papermaking sludge produced in a paper making process and; microfiberizing short fibers contained in the papermaking sludge into the cellulose nanofibers by using a grinding machine in a water-added state. The fiber contained in the papermaking sludge is ground efficiently due to an increase in viscosity of the sludge solution occurred by adding the water.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing cellulose nanofibers, and more particularly to a method for producing cellulose nanofibers using papermaking sludge containing fine fibers.

  Conventionally, the cellulose nanofiber manufactured from the pulp fiber etc. is known. Cellulose nanofibers are excellent in light weight, high strength, thermal stability and the like, and are expected to be used in various applications.

  As a method for producing such cellulose nanofibers, pulp fibers such as wood, fiber raw materials other than wood, and waste paper are confused with persulfates to hydrolyze and swell the pulp fibers. One that is miniaturized in a dispersed state is known (see, for example, Patent Document 1).

JP 2017-043677 A

  However, in the invention described in Patent Document 1, it is necessary to prepare a large amount of wood or the like when producing cellulose nanofibers, which is not preferable from the viewpoint of resource problems and environmental problems.

  Moreover, when manufacturing a cellulose nanofiber from the pulp fiber mixed long and short, there existed a problem that it took a long time until the pulp fiber was disentangled and disentangled finely.

  Therefore, a technical problem to be solved in order to produce cellulose nanofibers in a short time with resource saving arises, and the present invention aims to solve this problem.

  The present invention has been proposed in order to achieve the above object, and the invention according to claim 1 is a method for producing cellulose nanofibers, the step of recovering papermaking sludge generated in the papermaking step, and the papermaking And a step of producing the cellulose nanofiber by refining the short fiber contained in the sludge in a hydrolyzed state.

  According to this configuration, since cellulose nanofibers can be obtained from papermaking sludge as waste generated in the papermaking process, cellulose nanofibers can be produced with resource saving. Furthermore, since the fiber with a short fiber length contained in the papermaking sludge is refined, the cellulose nanofiber can be produced in a short time.

  According to a second aspect of the present invention, there is provided the method for producing cellulose nanofiber according to the first aspect, wherein the papermaking sludge is refined by a grinder.

  According to a third aspect of the present invention, in the configuration of the second aspect, the papermaking sludge is finely ground with a second grindstone having a finer grindstone particle size than the first grindstone after being coarsely ground with the first grindstone. A method for producing cellulose nanofibers to be crushed is provided.

  Invention of Claim 4 provides the manufacturing method of the cellulose nanofiber in which the said short fiber is colored in the structure of any one of Claim 1 to 3.

  Invention of Claim 5 is a structure in any one of Claim 1 to 4. The manufacturing method of the cellulose nanofiber which includes the process of dehydrating the said short fiber before the process of refine | miniaturizing the said short fiber I will provide a.

  According to the present invention, since cellulose nanofibers can be obtained from papermaking sludge as waste generated in the papermaking process, cellulose nanofibers can be produced with resource saving. Furthermore, since the short fibers having a short fiber length contained in the papermaking sludge are refined, cellulose nanofibers can be produced in a short time.

It is a flowchart which shows the procedure of the manufacturing method of the cellulose nanofiber which concerns on this invention. It is a SEM image of the fiber before rough grinding used in one example of the present invention. It is a SEM image of the fiber after rough grinding used in one example of the present invention. It is a SEM image of the fiber after fine grinding used in one example of the present invention.

  The present invention is a method for producing cellulose nanofibers in order to achieve the purpose of producing cellulose nanofibers in a resource-saving manner in a short time, a process for recovering papermaking sludge generated in the papermaking process, and papermaking sludge. And a process of producing cellulose nanofibers by refining the contained short fibers in a hydrolyzed state.

  The manufacturing method of the cellulose nanofiber which concerns on this invention is demonstrated based on drawing. FIG. 1 is a flowchart showing a procedure for producing cellulose nanofibers from wood-derived pulp. In addition, the pulp used as the raw material of a cellulose nanofiber should just contain a cellulose, For example, you may use what used fibers other than wood as a main component, or used paper etc. as a raw material.

[Pulping process]
First, chips taken from wood are digested to take out pulp (cellulose fibers). Then, the foreign material adhering to the pulp is removed, the pulp is washed, and the pulp is bleached. Additives such as known colorants (dyes or pigments) and paper strength enhancers are added to the paper stock obtained by adding pulp.

[Paper making process]
In the paper making process, the stock is made into paper using a known paper machine. For example, a paper product is obtained by uniformly spreading a liquid stock, squeezing and drying the stock, smoothing the surface of the stock, and then winding the stock.

[Sludge collection process]
Paper sludge discharged when the paper stock is expanded or squeezed in the paper making process is collected. The fibers contained in the papermaking sludge have not been fixed on the paper in the papermaking process, and have a shorter fiber length than the fibers contained in the paper product in the papermaking process. Hereinafter, the fibers contained in the papermaking sludge are referred to as “short fibers”.

[Dehydration process]
The recovered papermaking sludge is preferably dehydrated. By reducing the amount of water contained in the papermaking sludge before the refining step described later, the amount of water added when the short fibers are refined can be appropriately managed.

[Miniaturization process]
Gelled cellulose nanofibers are obtained by refining the short fibers so that the fiber width of the short fibers is narrowed to a desired value in a state where the short fibers are hydrated. The refinement of the fiber may be performed by mechanically defibrating the short fiber. For example, the refinement of the fiber is performed using a stone mill type grinder, but is not limited thereto.

  When short fibers are defibrated using a stone mill, a uniform cellulose nanofiber is obtained by gradually grinding the short fibers by the shearing force when passing between the two top and bottom non-porous grindstones. Can be obtained.

  The short fiber defibrated by the stone mill is pulverized so that the fiber width is narrowed and the fiber length is gradually shortened. In this way, although the short fibers are initially precipitated in water, they are diffused into the water to form a suspension as the miniaturization proceeds.

  When water is added to the short fiber, the viscosity of the water containing the short fiber increases, so that when the short fiber is ground with a grinder or the like, a shearing force is easily applied, and the short fiber can be easily defibrated.

  The short fibers are preferably refined stepwise. Specifically, since it is difficult to shorten a short fiber having a fiber width of about 10 μm to a single nano (<10 nm) with one kind of grindstone, for example, the fiber width of the short fiber is reduced to about 1/100 with a grindstone having a coarse particle size. After narrowing, it is preferable to refine the short fibers through a plurality of steps such as further narrowing the fiber width to about 1/100 with a fine-grain grindstone.

  In addition, the above-mentioned coarse grinding and fine grinding should be refined after adding a small amount of water to the short fiber rather than adding a large amount of water to the short fiber to make the desired fiber length at once. By repeating the above, it is possible to uniformly shorten the short fibers contained in the papermaking sludge by gradually miniaturizing the short fibers.

  In addition, when a colorant that colors the paper stock is added, the short fibers are also colored. Colored cellulose nanofibers can be obtained by refining the colored short fibers in a hydrolyzed state.

  After white short fibers are refined to obtain white cellulose nanofibers, it is difficult to uniformly mix the colorant into the high-viscosity cellulose nanofibers even when trying to color the cellulose nanofibers with a colorant or the like. . Moreover, when mixing a coloring agent, it is inevitable that air mixes into cellulose nanofibers. On the other hand, when the short fibers themselves are colored, colored cellulose nanofibers corresponding to the color of the short fibers can be obtained.

  Next, although the cellulose nanofiber which concerns on one Example of this invention is demonstrated, this invention is not limited to this Example.

  Paper sludge discharged in the papermaking process of household paper was collected. As the papermaking sludge, one discharged from a stock mixed with a blue dye was used. That is, the short fibers contained in the papermaking sludge are blue fibers colored with a dye.

  The papermaking sludge was refined using a grinder (manufactured by Masuko Sangyo Co., Ltd., model number: MKCA6-5JR).

  Specifically, first, the first grindstones of counts 16 # to 24 # were attached to the attritor. Then, 13.5 L of pure water was added to 1.5 g of papermaking sludge, and the papermaking sludge was coarsely ground with a first grindstone at a rotational speed of 1200 to 1800 rpm for 2 to 20 minutes. In this example, depending on the progress of the coarse grinding, water addition and coarse grinding of the papermaking sludge were repeated 1 to 6 times.

  The SEM image of the short fiber contained in the papermaking sludge before rough grinding is shown in FIG. The short fibers before coarse grinding shown in FIG. 2 had a fiber width of about 10 μm.

  Moreover, the SEM image of the short fiber after rough grinding is shown in FIG. In addition, the arrow in FIG. 3 has shown one short fiber contained in the papermaking sludge after rough grinding. The short fibers after coarse grinding shown in FIG. 3 had a fiber width of several tens to several hundreds of nanometers.

  That is, the fiber width is narrowed to about 1/100 to 1/1000 by roughly grinding short fibers. Moreover, the fiber length is similarly shortened by the short fiber being defibrated.

  Then, the 2nd grindstone of counts 24 # -120 # was attached to the attritor. Then, the paper sludge was finely ground with a second grindstone at a rotation speed of 1200 to 1800 rpm for 20 to 60 minutes. In this example, the fine grinding of the paper sludge was repeated 1 to 3 times according to the progress of the fine grinding. The gel-like cellulose nanofibers thus obtained had a water content of 98%.

  The SEM image of the short fiber after fine grinding is shown in FIG. In addition, the arrow in FIG. 4 has shown the one short fiber contained in the papermaking sludge after fine grinding. The short fiber after fine grinding shown in FIG. 4 had a fiber width of several to several hundred nm.

  That is, the fiber width is narrowed to about 1/10 to 1/100 by finely grinding the short fibers. The fiber length is also shortened. In addition, it is not necessary for all the short fibers contained in the paper sludge after fine grinding to achieve a single nano, and the entire short fiber is sufficiently defibrated so that at least one short fiber reaches a single nano. If it is.

  The cellulose nanofibers obtained in this manner can be obtained from papermaking sludge as waste generated in the papermaking process, so that the cellulose nanofibers can be produced with resource saving. Furthermore, since the short fiber contained in papermaking sludge is refined | miniaturized, a cellulose nanofiber can be manufactured in a short time.

  Moreover, the colored cellulose nanofiber according to the color of a short fiber can be obtained by manufacturing a cellulose nanofiber using the short fiber colored beforehand.

It should be noted that the present invention can be modified in various ways without departing from the spirit of the present invention other than the structure of the above-described modification, and the present invention naturally extends to the modified structure.

Claims (5)

A method for producing cellulose nanofibers, comprising:
A process of collecting papermaking sludge generated in the papermaking process;
Refining the short fibers contained in the paper sludge in a watered state to produce the cellulose nanofibers;
The manufacturing method of the cellulose nanofiber characterized by including.   The method for producing cellulose nanofiber according to claim 1, wherein the papermaking sludge is refined by a grinder.   3. The cellulose nanofiber according to claim 2, wherein the paper sludge is coarsely ground with a first grindstone and then finely ground with a second grindstone having a smaller grindstone particle size than the first grindstone. Manufacturing method.   The method for producing cellulose nanofiber according to any one of claims 1 to 3, wherein the short fibers are colored. The method for producing cellulose nanofiber according to any one of claims 1 to 4, further comprising a step of dehydrating the short fiber before the step of refining the short fiber.