Method of manufacturing pulp from stem of bast plant

Abstract

To provide a pulp manufacturing method using stems after bast removal by pulping stems after removing bast from bast plants.SOLUTION: A pulp manufacturing method using stems after bast removal includes a bast removal step of removing bast from stems of bast plants, a breaking step of cutting stems with bast having been peeled off in the bast removal step, a fiberization step of compressing, shearing, and kneading stems cut to chips in the breaking step in a state where an alkaline solution is included by using a screw 12 for fiberization, and a cleaning step of stirring and disintegrating fiberized stems in a solution.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing pulp using stems after removal of the bast. [Background technology]

[0002] Patent Document 1 discloses a pulp manufacturing method in which chips cut from raw wood (mitsumata) containing bast fibers are steamed under normal or increased pressure together with water containing sulfite and alkaline substances to peel off the bast, the bast is beaten to obtain bast pulp, and the wood is ground to obtain ground pulp.

[0003] Patent Document 2 discloses an apparatus and method for producing pulp by feeding a non-wood raw material (bast) into a twin-screw extruder and subjecting it to physical treatment by the twin-screw extruder and alkaline chemicals. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 63-5520 [Patent Document 2] Japanese Patent Publication No. 2021-134444 Summary of the Invention [Problem to be solved by the invention]

[0005] However, Patent Documents 1 and 2 disclose the pulping of the bast of bast plants. The bare wood of bast plants from which the bast portion has been removed is discarded or used as fuel without being pulped, but in recent years, from the perspective of reducing carbon dioxide emissions, there has been a demand for effective utilization other than incineration.

[0006] An object of the present invention is to provide a method for producing pulp using bast-removed stems, which involves pulping the stems obtained after stripping the bast from a bast plant. [Means for solving the problem]

[0007] The present invention is characterized by comprising a bast removal process in which the bast is stripped from the stems of bast plants; a crushing process in which the stems from which the bast has been stripped in the bast removal process are cut; a fiberization process in which the stems cut and turned into chips in the crushing process are compressed, sheared and kneaded with a screw in a state containing an alkaline solution to turn them into fibers; and a washing process in which the fiberized stems are stirred in the solution to disintegrate them. [Effects of the Invention]

[0008] According to the present invention, by pulping the stems of bast plants, which have not been used until now, it is possible to realize effective use other than incineration from the perspective of reducing carbon dioxide emissions, etc., and pulp can be efficiently produced from the stems of bast plants without placing a burden on the environment. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a flow chart showing a pulp manufacturing method using the stem after bast removal according to an embodiment of the present invention. [Figure 2] The diagram shows the configuration of a twin-screw extruder used in the fiberization process of the pulp manufacturing method using the stem after the bast removal. [Figure 3] Photographs showing hand-made sheets produced by the pulp production method using the stem after bast removal, together with a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] A method for producing pulp from the stems of bast plants according to an embodiment of the present invention includes a bast removal step of stripping the bast from the stems of bast plants, a crushing step of cutting the stems from which the bast has been removed in the bast removal step, a fiberization step of compressing, shearing, and kneading the stems cut into chips in the crushing step with a screw in a state containing an alkaline solution to fiberize the stems, and a washing step of agitating and defibrating the fiberized stems in an alkaline solution. According to this embodiment, pulp can be produced using the stems from which the bast has been removed.

[0011] In addition, in the method for producing pulp from the stems of bast plants, the bast plant is mitsumata. According to this embodiment, pulp can be produced using plain wood of mitsumata.

[0012] In addition, in a method for producing pulp from the stems of bast plants, the fiberization step uses a twin-screw extruder having two screws inside the cylinder, the temperature inside the cylinder is set to a range of 20°C to 80°C, and the liquid ratio, which is the ratio of alkaline solution to the bone dry weight of the stems, is 1:2. This allows fiberization in a short time without blackening. [Example]

[0013] A method for producing pulp from stems of bast plants according to an embodiment of the present invention will now be described. Figure 1(a) is a flow chart showing a method for producing pulp from stems of bast plants according to an embodiment of the present invention.

[0014] The method for producing pulp from the stems of bast plants according to this embodiment includes a bast removal process (S1) in which the bast is stripped from the stems of bast plants, a crushing process (S2) in which the stems from which the bast has been stripped in the bast removal process (S1) are cut, a fiberization process (S3) in which the stems cut into chips in the crushing process (S2) are compressed, sheared, and kneaded with a screw in an alkaline solution to fiberize them, and a washing process (S4) in which the fiberized stems are stirred in an alkaline solution to disintegrate them.

[0015] Examples of bast plants include hemp, flax, paper mulberry, and mitsumata, but in this example, mitsumata is used. Mitsumata branches are harvested between late November and April. Figure 1(b) shows a harvested mitsumata branch. Two- to three-year-old branches are suitable for pulp.

[0016] In the bast removal step (S1), the cut branches are steamed with water for about 3 hours and the bast is stripped off. The bast is stripped of its epidermis, cuticle, and impurities to leave a white bark, which is then processed into pulp through a cooking step and a washing step. The means for stripping off the bast is not particularly limited, and may be performed by a known machine or by hand.

[0017] The pulp manufacturing method of this example uses the trunk after the bast has been removed, i.e., plain wood. Figure 1(c) shows plain wood that has undergone the bast removal step (S1).

[0018] In the crushing step (S2), the stem (white wood) after bast removal is cut into pieces approximately 1 cm long. The stems cut into chips in the crushing step (S2) are preferably immersed in an alkaline solution prior to the fiberization step (S3). The amount (g) of sodium hydroxide added is within a suitable range, but preferably the amount (g) of alkaline substance added is 5% to 10% of the bone-dry weight (g) of the stems. The blending ratio of the alkaline solution to the stems is within a suitable range, depending on the type of alkaline solution and the capacity of the cylinder 11 of the twin-screw extruder 10, but a liquid ratio of the amount (ml) of alkaline solution to the bone-dry weight (g) of the stems is preferably 1:2. In addition to sodium hydroxide (NaOH), sodium carbonate (soda ash, Na2CO3), calcium hydroxide (Ca(OH)2), or calcium carbonate (CaCO3) can also be used as the alkaline substance.

[0019] In the fiber-forming step (S3), a twin-screw extruder 10 (see FIG. 2) is used. FIG. 1(d) shows the trunk portion that has been compressed, sheared, and kneaded to form fibers in the fiber-forming step (S3).

[0020] In the washing step (S4), the fiberized stem is immersed in water and stirred, and soluble components such as pectin are removed using a strainer or the like to isolate the pulp.

[0021] 2 is a diagram showing the configuration of a twin-screw extruder used in the fiber-forming step (S3). As shown in FIG. 2(a), a twin-screw extruder 10 has two screws 12 in a cylinder 11.

[0022] Cylinder 11 has an inlet 13 at one end and an outlet 14 at the other end. A heater (not shown) is provided inside cylinder 11, and the temperature inside cylinder 11 is kept within the range of 20°C to 80°C by the heater. Screw 12 is driven by a rotation drive mechanism 15.

[0023] FIG. 2(b) shows a portion of the screw 12 shown in FIG. 2(a). As shown in FIG. 2(b), the screw 12 is formed with a compression section 12a, a shearing section 12b, and a kneading section 12c. Therefore, when the stem portion cut into chips in the crushing step (S2) is fed into the cylinder 11 through the inlet 13, it is compressed in the compression section 12a, sheared in the shearing section 12b, and kneaded in the kneading section 12c while still containing the alkaline solution. The chipped stem portion is repeatedly compressed, sheared, and kneaded by the screw 12, resulting in fiberization, and is discharged from the outlet 14.

[0024] FIG. 3 is a photograph showing a hand-made sheet produced by the method for producing pulp from the stems of bast plants according to this example, together with a comparative example.

[0025] Comparative Example 1 is a hand-made sheet produced by pressure cooking of bast, Comparative Example 2 is a hand-made sheet produced by fiberizing bast using a twin-screw extruder 10 (produced according to Patent Document 2), and Comparative Example 3 is a hand-made sheet produced by pressure cooking of the stem after removing the bast.

[0026] According to the method for producing pulp from the stems of bast plants in this example, the fibers are thick and short, and have the characteristic of low infrared transmittance, and a hand-made sheet was produced that is closer in hue to egg yolk than bast.

[0027] Furthermore, the pulp production method according to this example has the following characteristics: fewer shives (foreign matter); less side reaction such as blackening due to the lower temperature and shorter treatment time compared to pressure cooking; less discoloration of the fibers; fewer dissolved components (lignin, hemicellulose, pectin, etc.) due to the lower temperature and shorter treatment time compared to pressure cooking, resulting in a higher pulp yield; and fewer side reactions due to the dissolved components, making it easier to effectively utilize in biorefineries. As described above, according to this example, pulp can be produced using the stem after bast removal. [Industrial Applicability]

[0028] According to the present invention, the stems of bast plants, which have not been used until now, can be pulped to obtain egg yolk fibers, and further, the characteristic of low infrared transmittance can be utilized. [Explanation of symbols]

[0029] 10 Twin-screw extruder 11 cylinders 12 screws 13 Inlet 14 Outlet 15 Rotation drive mechanism 12a Compression section 12b Shear section 12c Kneading section

Claims

[Claim 1] a bast removal step of stripping the bast from the stem of the bast plant; a crushing step of cutting the stem from which the bast has been stripped in the bast removing step; a fiberization step in which the stems cut into chips in the crushing step are compressed, sheared, and kneaded with a screw in a state containing an alkaline solution to form fibers; a washing step of agitating the fiberized stems in the alkaline solution to disintegrate them; 1. A method for producing pulp from the stems of bast plants, comprising:

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