Method for removing black bark of bast pulp raw material by ultrasonic wave and chemical treatment and application thereof

Abstract

This invention discloses a method for removing the black outer layer of bast pulping raw materials using ultrasonic synergistic chemical treatment and its application, belonging to the field of pulp and paper raw material pretreatment technology. The method specifically includes the following steps: adding bast raw materials and sodium hydroxide to a penetrant, followed by ultrasonic synergistic treatment to obtain bast raw materials with the surface black outer layer removed. This invention achieves the decomposition and removal of the black outer layer of bast raw materials by transferring ultrasonic energy to the penetrant, generating microbubbles and causing liquid oscillation, synergistically with sodium hydroxide. This improves the quality of the raw materials and processing efficiency, providing a theoretical basis and technical support for the subsequent pulping of bast raw materials and the high-value application of bast-based raw materials.

Description

Technical Field

[0001] This invention belongs to the field of pulp and paper raw material pretreatment technology, and particularly relates to a method for removing the black skin of the epidermal layer of bast pulp raw materials by ultrasonic synergistic chemical treatment and its application. Background Technology

[0002] Compared to raw materials such as wood, bamboo, and grass, plant bast papermaking raw materials consist of a bast outer layer (i.e., black bark) and an inner bast bark. The bast outer layer contains almost no fiber or cellulose. The presence of this black bark during pulping consumes a large amount of chemicals and is difficult to remove after pulping, leading to decreased pulp yield and brightness, as well as lower pulp cleanliness. Therefore, black bark removal is a crucial step in the pulping process of bark papermaking raw materials. To ensure full utilization of plant bast, black bark removal needs to be performed at the beginning of pulping.

[0003] Existing technologies generally employ two methods to separate the black bark from the inner bast layer: the first is a manual removal method, such as scraping the outer black bark with a scraper or similar tool during material preparation; the second is a chemical removal method, for example, Chinese patent application 200910114339.3 discloses a method for rapid separation of the outer bast layer of mulberry bark. This method involves first soaking the raw material in a soaking solution at 20-80℃ for 0.5-48 hours, followed by boiling. The chemical additives added during boiling are one of soda ash, sodium silicate, or trisodium phosphate. Boiling is carried out at 85-100℃ under normal pressure for 0.5-1.5 hours. Finally, the bark is washed with a rotary washing machine, pressed with a press, and screened with a filter to remove impurities from the bast layer. The first method described above is labor-intensive, inefficient, and results in significant loss of inner bast fibers during the peeling process. The second method uses more chemical raw materials and is complex to operate; while it can remove the surface black bast layer, it generates a large amount of waste, causing environmental pollution, and has high production costs. Furthermore, the quality of the resulting inner bast layer is poor, and it degrades the fibers of the inner bast layer. Currently, separating the surface black bast layer is a major challenge in the field of bast utilization. Therefore, there is an urgent need to provide an effective method for removing the surface black bast layer from raw materials. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for removing the black outer layer of bast pulping raw materials using ultrasonic-assisted chemical treatment, and its application. This invention utilizes ultrasonic energy transferred to a penetrant to generate microbubbles and induce liquid oscillation, which, in conjunction with sodium hydroxide, decomposes and removes the black outer layer of the bast raw materials. This improves the quality of the raw materials and processing efficiency, providing a theoretical basis and technical support for subsequent pulping of bast raw materials and the high-value application of bast-based raw materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for removing the black outer layer of bast pulping raw materials using ultrasonic-assisted chemical treatment specifically includes the following steps: Bast material and sodium hydroxide are added to the permeation solution, and after ultrasonic synergistic treatment, bast material with the surface black skin removed is obtained.

[0007] Preferably, the mass ratio of the bast material to sodium hydroxide is 70-150:1.

[0008] Preferably, the mass ratio of the bast material to sodium hydroxide is 100:1.

[0009] Preferably, the impregnation ratio of the bast material to the permeating liquid is 1:10-80.

[0010] Preferably, the permeate is a fatty alcohol polyoxyethylene ether, and the concentration of the permeate is 1-10 g / L.

[0011] Preferably, the molecular weight of the fatty alcohol polyoxyethylene ether is 350-450.

[0012] Preferably, the molecular weight of the fatty alcohol polyoxyethylene ether is 400.

[0013] Preferably, the conditions for ultrasonic treatment are: ultrasonic frequency of 5-80KHz, power of 300W, treatment temperature of 20-60℃, and treatment time of 2-9h.

[0014] Preferably, the bast material is at least one of the following: bark of Pterocarya stenoptera, bark of Rhododendron molle, and bark of Broussonetia papyrifera.

[0015] The above-described method for removing the black skin from the outer layer of bast pulping raw materials using ultrasonic-assisted chemical treatment is applied in the papermaking industry.

[0016] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: (1) The bast raw material prepared by the method of the present invention can not only reduce the amount of chemicals used in the pulping process, but also obtain a pulp with higher purity and higher whiteness. (2) The method of the present invention uses ultrasonic combined with chemical treatment of bast raw materials, which promotes the development of bast raw material pulping and alleviates the problem of pulping and papermaking resource shortage to a certain extent. (3) The method of the present invention is easy to operate, simple in process, and low in energy consumption. At the same time, it can improve the cleanliness and whiteness of pulp, making it suitable for large-scale production. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 The images show raw materials of *Pterocarya stenoptera* bark, *Raphanus sativus* bark, and *Broussonetia papyrifera* bark, which are chemically treated in this embodiment of the invention; where a is *Pterocarya stenoptera* bark; b is *Raphanus sativus* bark; and c is *Broussonetia papyrifera* bark. Figure 2 The images show raw materials of *Pterocarya stenoptera* bark, *Raphanus sativus* bark, and *Broussonetia papyrifera* bark treated only with ultrasonic waves, according to embodiments of the present invention; where a is *Pterocarya stenoptera* bark; b is *Raphanus sativus* bark; and c is *Broussonetia papyrifera* bark. Figure 3 The image shows the raw materials of *Pterocarya stenoptera* bark, *Raphanus sativus* bark, and *Broussonetia papyrifera* bark after ultrasonic synergistic chemical treatment according to an embodiment of the present invention. In the image, a is *Pterocarya stenoptera* bark; b is *Raphanus sativus* bark; and c is *Broussonetia papyrifera* bark. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 This invention provides a method for removing the black outer layer of bast raw materials using ultrasonic-assisted chemical treatment, the specific steps of which are as follows: Take 10g of *Pterocarya stenoptera* bark and 0.1g of sodium hydroxide and add them to a fatty alcohol polyoxyethylene ether solution (concentration 1g / L, molecular weight of fatty alcohol polyoxyethylene ether is about 400). The impregnation ratio of *Pterocarya stenoptera* bark to fatty alcohol polyoxyethylene ether solution is 1:10. Soak in ultrasound for 3 hours at a temperature of 40℃, a power of 300W and a frequency of 40KHz.

[0021] Example 2 This invention provides a method for removing the black outer layer of bast raw materials using ultrasonic-assisted chemical treatment, the specific steps of which are as follows: Take 10g of peony bark raw material and 0.1g of sodium hydroxide and add it to a fatty alcohol polyoxyethylene ether solution (concentration of 5g / L, molecular weight of fatty alcohol polyoxyethylene ether is about 400). The impregnation ratio of peony bark raw material to fatty alcohol polyoxyethylene ether solution is 1:80. Soak in ultrasound for 9 hours at a temperature of 60℃, a power of 300W and a frequency of 10KHz.

[0022] Example 3 This invention provides a method for removing the black outer layer of bast raw materials using ultrasonic-assisted chemical treatment, the specific steps of which are as follows: Take 10g of paper mulberry bark raw material and 0.1g of sodium hydroxide and add them to a fatty alcohol polyoxyethylene ether solution (concentration of 2g / L, molecular weight of fatty alcohol polyoxyethylene ether is about 400). The impregnation ratio of the paper mulberry bark raw material to the fatty alcohol polyoxyethylene ether solution is 1:30. Soak in ultrasound for 2 hours at a temperature of 40℃, a power of 300W and a frequency of 80KHz.

[0023] Meanwhile, comparative studies were conducted using only chemical treatment and only ultrasonic treatment. The processing techniques for the relevant bast raw materials, Pterocarya stenoptera bark, Paeonia lactiflora bark, and Broussonetia papyrifera bark, corresponded to those in Examples 1-3, serving as single-factor controls. Related product images are shown below. Figure 1-3 ; The bast raw materials from Examples 1-3 were subjected to chemical treatment only, ultrasonic treatment only, and ultrasonic combined with chemical treatment, respectively. After being pulped, the bast raw materials were sieved through a 0.1 mm flat plate sieve and a 16 mesh grading sieve before papermaking. The paper whiteness was measured according to GB / T22879-2008, and the dust area of ​​the paper was measured according to GB / T 1541-2013. The pulping process conditions for bast fiber raw materials after ultrasonic-assisted chemical treatment are as follows: 16% NaOH, 0.1% AQ, liquor ratio 1:6, maximum temperature 155℃, heating time 1.5h, and holding time 3.5h. The pulping process conditions for bast fiber raw materials after only chemical and ultrasonic treatment are as follows: 20% NaOH, 0.1% AQ, liquor ratio 1:6, maximum temperature 155℃, heating time 1.5h, and holding time 3.5h. The relevant results are shown in Table 1. Table 1. Test results of cleanliness and whiteness of pulp after bast raw material pulping

[0024] from Figures 1-3 As can be seen, the bark of *Pterocarya stenoptera* and *Broussonetia papyrifera* has a dense epidermal structure, making it difficult for the drug to penetrate when treated with only 0.1g of NaOH, resulting in the outer bark remaining almost intact. When treated with only ultrasound, the effect of ultrasound makes the bark structure looser, causing it to peel off. When sodium hydroxide and ultrasound are treated simultaneously, ultrasound treatment facilitates the penetration of sodium hydroxide solution, increases the dissolution of pectin and lignin in the bark, and causes most of the outer bark to peel off. As shown in Table 1, after caustic soda-anthraquinone cooking, the dust area of ​​the pulp from *Pterocarya stenoptera* bark, *Daphne odora* bark, and *Broussonetia papyrifera* bark, which underwent chemical treatment, was 3589.2 mm². 2 ·m -2 3193.5mm 2 ·m -2and 3460.5mm 2 ·m -2 After ultrasonic treatment, the dust area of ​​pulp from *Pterocarya stenoptera* bark, *Daphne odora* bark, and *Broussonetia papyrifera* bark was 3226.7 mm². 2 ·m -2 2439.2mm 2 ·m -2 and 2836.9mm 2 ·m -2 After treatment with a combination of ultrasonic and chemical methods, the dust area of ​​pulp from *Pterocarya stenoptera* bark, *Daphne odora* bark, and *Broussonetia papyrifera* bark was 1465.6 mm². 2 ·m -2 1223.5mm 2 ·m -2 and 1083.6mm 2 ·m -2 It can be seen that compared with chemical treatment and ultrasonic treatment, the dust area of ​​the pulp of *Pterocarya stenoptera* bark, *Raphanus sativus* bark, and *Broussonetia papyrifera* bark treated with a combination of ultrasonic and chemical treatment is significantly reduced, and the amount of chemicals used during pulping is also reduced, indicating that this method is effective in removing the black bark from the surface layer of bast raw materials.

[0025] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for removing the black outer layer of bast pulping raw materials by ultrasonic-assisted chemical treatment, characterized in that, Specifically, the following steps are included: Bast material and sodium hydroxide are added to the permeation solution, and after ultrasonic synergistic treatment, bast material with the surface black skin removed is obtained.

2. The method for removing the black outer layer of bast pulping raw materials by ultrasonic-assisted chemical treatment according to claim 1, characterized in that, The mass ratio of the bast material to sodium hydroxide is 70-150:

1.

3. The method for removing the black outer layer of bast pulping raw materials by ultrasonic-assisted chemical treatment according to claim 1, characterized in that, The mass ratio of the bast material to sodium hydroxide is 100:

1.

4. The method for removing the black outer layer of bast pulping raw materials by ultrasonic-assisted chemical treatment according to claim 1, characterized in that, The impregnation ratio of the bast material to the permeating liquid is 1:10-80.

5. The method for removing the black outer layer of bast pulping raw materials by ultrasonic-assisted chemical treatment according to claim 1, characterized in that, The permeate is an aqueous solution of fatty alcohol polyoxyethylene ether, and the concentration of the permeate is 1-10 g / L.

6. The method for removing the black outer layer of bast pulping raw materials by ultrasonic-assisted chemical treatment according to claim 4, characterized in that, The molecular weight of the fatty alcohol polyoxyethylene ether is 350-450.

7. The method for removing the black outer layer of bast pulping raw materials by ultrasonic-assisted chemical treatment according to claim 4, characterized in that, The molecular weight of the fatty alcohol polyoxyethylene ether is 400.

8. The method for removing the black outer layer of bast pulping raw materials by ultrasonic-assisted chemical treatment according to claim 1, characterized in that, The conditions for ultrasonic treatment are: ultrasonic frequency of 5-80KHz, power of 300W, treatment temperature of 20-60℃, and treatment time of 2-9h.

9. The method for removing the black outer layer of bast pulping raw materials by ultrasonic-assisted chemical treatment according to claim 1, characterized in that, The bast material is at least one of the following: bark of Pterocarya stenoptera, bark of Rhododendron molle, and bark of Broussonetia papyrifera.

10. The application of the method for removing the black skin layer of bast pulping raw materials by ultrasonic synergistic chemical treatment according to any one of claims 1-9 in the papermaking field.

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