A method for improving pulp yield by adding amino acids

Abstract

This invention relates to the field of papermaking, and particularly to a pulping method that significantly improves cellulose retention by adding amino acids. The method includes the following steps: mixing bamboo raw materials with a ternary eutectic solvent in a specific ratio and reacting the mixture in a microwave apparatus; subsequently washing the mixture with acetone solution, anhydrous ethanol, and deionized water until neutral, and then drying the mixture to obtain fiber residue, which is the target pulp. The ternary eutectic solvent is prepared as follows: mixing choline chloride, amino acids, and L-lactic acid solution in a specific ratio and continuously heating and stirring until a clear and transparent solution is formed, thus obtaining the ternary eutectic solvent. The clean pulping process using bamboo as a raw material provided by this invention produces very little black liquor and no harmful gases during the process. The waste and pulping waste liquor generated can be recycled and reused through evaporation or other methods.

Description

Technical Field

[0001] This invention relates to the field of papermaking, and in particular to a pulping method that significantly improves cellulose retention by adding amino acids. Background Technology

[0002] In the currently developed and mature pulping processes, pulping routes using wood as the main raw material account for as much as 95%. The rapid development of the paper industry has put enormous pressure on the sustainable supply of global forest resources. Researchers and industry professionals are constantly improving pulping technology while broadening the sources of raw materials for pulping and papermaking in order to increase pulp yield and pulp quality.

[0003] my country is rich in bamboo resources. Bamboo fiber properties are similar to those of coniferous wood, making it an excellent raw material for pulping and capable of replacing some wood pulp. Patent CN116145457B first treats bamboo with steam pre-hydrolysis, followed by alkaline cooking, oxygen-alkali bleaching, and pulping processes to produce bleached bamboo pulp with a yield of approximately 31%. Patent CN116695479A first pre-impregnates bamboo chips with warm black liquor, then replaces the warm black liquor with hot black liquor to reach a temperature of 125–135°C, before adding hot white liquor at 150°C or higher for cooking, resulting in a final yield of 46%–49%. In recent years, eutectic solvents have begun to be used in the preparation of high-quality pulp. Patent CN116200959B mixes bamboo and rice straw in a certain proportion, then cooks the mixture under specific conditions using a eutectic solvent composed of choline chloride and DL-menthol, achieving a pulp yield of 50%–54%. Eutectic solvents are clear, transparent, homogeneous solvents formed by the bonding of two or three components through hydrogen bond interactions between hydrogen bond donors and acceptors. Eutectic solvents possess advantages such as being non-toxic, recyclable, and stable. Research on clean pulping processes for bamboo pulp using eutectic solvents has significant practical implications for the pulp and paper industry.

[0004] However, existing pulping technologies using bamboo as the main raw material have at least the following drawbacks:

[0005] Because cellulose, hemicellulose, and lignin are tightly bound together in bamboo raw materials, existing pulping technologies often employ more vigorous cooking conditions to remove a large amount of lignin. However, this process also leads to partial degradation of cellulose, reducing pulp yield. While the mild pulping technologies developed at present have solved some of the problems of existing technologies, they still have many drawbacks, such as the high environmental pollution load, cumbersome processing, and low yield of traditional alkaline cooking, and the high cost of reagents used in new eutectic solvents, which also result in a decrease in cellulose yield. Summary of the Invention

[0006] To address the aforementioned drawbacks, this invention provides a method for preparing pulp from bamboo raw materials by cooking with a ternary eutectic solvent. This method has the advantages of readily available reagents, environmental friendliness, and high pulp yield.

[0007] This invention provides a method for preparing pulp from bamboo raw materials by cooking with a ternary eutectic solvent, comprising the following steps:

[0008] S1 mixes bamboo raw materials with a ternary eutectic solvent in a certain proportion and reacts them in a microwave oven at 120℃~140℃ and 500W~700W for 10min~30min.

[0009] S2 was then washed sequentially with acetone solution, anhydrous ethanol, and deionized water until neutral, and then dried to obtain fiber residue, which is the target sizing agent.

[0010] The preparation method of the ternary eutectic solvent is as follows: under the condition of 70℃~90℃, choline chloride, amino acid and L-lactic acid solution are mixed in proportion and heated and stirred continuously until a clear and transparent solution is formed to obtain the ternary eutectic solvent.

[0011] In a specific embodiment, the bamboo raw material is selected from moso bamboo, ci bamboo, etc., and is crushed to 30-50 mesh to initially obtain the bamboo raw material.

[0012] In a preferred embodiment, the acetone solution in S2 is a 50% acetone solution.

[0013] In a specific embodiment, the amino acid is one or more selected from L-arginine, L-tyrosine, L-glycine, L-alanine, L-proline, L-valine, and L-threonine.

[0014] In a preferred embodiment, the mixing ratio of choline chloride, amino acids, and L-lactic acid is 1:0.01-0.1:2-18. More preferably, it is 1:0.03-0.08:6-15; even more preferably, it is 1:0.05:9.

[0015] In a specific embodiment, the mixing ratio of choline chloride, amino acids and L-lactic acid is 1:0.0-4-0.06:7-11; specifically 1:0.05:9.

[0016] Preferably, in S1, the reaction is carried out in a microwave apparatus at 125°C to 135°C and 500W to 700W for 15 to 25 minutes. More specifically, for example, the temperature is 130°C, the microwave power is 600W, and the reaction is carried out for 20 minutes under these conditions.

[0017] The present invention also provides a slurry obtained by the method.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] Compared with existing technologies, the method for preparing bamboo pulp using ternary eutectic solvent-assisted microwave treatment of bamboo in this invention improves pulp yield by pretreating bamboo with a eutectic solvent. This invention also uses a microwave reactor to assist cooking under defined conditions, significantly shortening cooking time and greatly improving cooking efficiency. By carefully controlling the power, cooking time, and temperature of the microwave reactor, this invention achieves both effective cooking and prevents excessive damage to the internal structure of the raw materials by microwaves.

[0020] Furthermore, the addition of amino acids can significantly improve pulp retention and effectively enhance the pulping effect of eutectic solvents. The principle is that amino acids can form intermolecular hydrogen bonds with one of the three hydroxyl groups on the same side of cellulose, thereby preventing choline cations and protons, or chloride and carboxylic acid anions in the eutectic solvent, from simultaneously forming three hydrogen bonds with the three hydroxyl groups on the same side of cellulose, thus inhibiting cellulose degradation.

[0021] Therefore, the clean pulping process using bamboo as a raw material provided by this invention produces very little black liquor and no harmful gases during the process. The waste and pulping waste liquor generated can be recycled and reused through evaporation and other methods. Detailed Implementation

[0022] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0023] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0024] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0025] Example 1

[0026] 1. Material preparation: Crush the bamboo into powder to 40 mesh to complete the material preparation;

[0027] 2. Synthesis of a eutectic solvent: A eutectic solvent was synthesized using choline chloride, L-arginine, and L-lactic acid in a molar ratio of 1:0.05:9. The three components were mixed in a flask, placed in an 80°C oil bath, and stirred until a clear, transparent solution was formed.

[0028] 3. Pretreatment: Add 40-mesh bamboo powder to a flask containing a eutectic solvent at a mass ratio of 1:20. Place the flask in a microwave reactor, adjust the temperature to 130℃ and the microwave power to 600W, and maintain this condition for 20 minutes. After the pretreatment, a mixed slurry is obtained.

[0029] 4. Washing: Wash the mixed slurry with 50% acetone solution at a volume of 3 times that of the eutectic solvent. The washing operation is carried out using a vacuum filter. After the acetone washing is completed, continue to wash the slurry with anhydrous ethanol. After the washing solution becomes colorless, continue to wash with deionized water until the pH value of the washing solution is neutral.

[0030] 5. Drying: Place the slurry obtained in step (4) in an oven and dry for 24 hours to obtain the target slurry.

[0031] Example 2

[0032] 1. Material preparation: Crush the bamboo into powder to 40 mesh to complete the material preparation;

[0033] 2. Synthesis of a eutectic solvent: A eutectic solvent was synthesized using choline chloride, L-tyrosine, and L-lactic acid in a molar ratio of 1:0.05:9. The three components were mixed in a flask, placed in an 80°C oil bath, and stirred until a clear, transparent solution was formed.

[0034] 3. Pretreatment: Add 40-mesh bamboo powder to a flask containing a eutectic solvent at a mass ratio of 1:20. Place the flask in a microwave reactor, adjust the temperature to 130℃ and the microwave power to 600W, and maintain this condition for 20 minutes. After the pretreatment, a mixed slurry is obtained.

[0035] 4. Washing: Wash the mixed slurry with 50% acetone solution at a volume of 3 times that of the eutectic solvent. The washing operation is carried out using a vacuum filter. After the acetone washing is completed, continue to wash the slurry with anhydrous ethanol. After the washing solution becomes colorless, continue to wash with deionized water until the pH value of the washing solution is neutral.

[0036] 5. Drying: Place the slurry obtained in step (4) in an oven and dry for 24 hours to obtain the target slurry.

[0037] Example 3

[0038] 1. Material preparation: Crush the bamboo into powder to 40 mesh to complete the material preparation;

[0039] 2. Synthesis of a eutectic solvent: A eutectic solvent was synthesized using choline chloride, L-glycine, and L-lactic acid in a molar ratio of 1:0.05:9. The three components were mixed in a flask, placed in an 80°C oil bath, and stirred until a clear, transparent solution was formed.

[0040] 3. Pretreatment: Add 40-mesh bamboo powder to a flask containing a eutectic solvent at a mass ratio of 1:20. Place the flask in a microwave reactor, adjust the temperature to 130℃ and the microwave power to 600W, and maintain this condition for 20 minutes. After the pretreatment, a mixed slurry is obtained.

[0041] 4. Washing: Wash the mixed slurry with 50% acetone solution at a volume of 3 times that of the eutectic solvent. The washing operation is carried out using a vacuum filter. After the acetone washing is completed, continue to wash the slurry with anhydrous ethanol. After the washing solution becomes colorless, continue to wash with deionized water until the pH value of the washing solution is neutral.

[0042] 5. Drying: Place the slurry obtained in step (4) in an oven and dry for 24 hours to obtain the target slurry.

[0043] Example 4

[0044] 1. Material preparation: Grind the bamboo into powder to 40 mesh to complete the material preparation;

[0045] 2. Synthesis of a eutectic solvent: A eutectic solvent was synthesized using choline chloride, L-glycine, and L-lactic acid in a molar ratio of 1:0.05:9. The three components were mixed in a flask, placed in an 80°C oil bath, and stirred until a clear, transparent solution was formed.

[0046] 3. Pretreatment: Add 40-mesh bamboo powder to a flask containing a eutectic solvent at a mass ratio of 1:20. Place the flask in a microwave reactor, adjust the temperature to 130℃ and the microwave power to 600W, and maintain this condition for 20 minutes. After the pretreatment, a mixed slurry is obtained.

[0047] 4. Washing: Wash the mixed slurry with 50% acetone solution at a volume of 3 times that of the eutectic solvent. The washing operation is carried out using a vacuum filter. After the acetone washing is completed, continue to wash the slurry with anhydrous ethanol. After the washing solution becomes colorless, continue to wash with deionized water until the pH value of the washing solution is neutral.

[0048] 5. Drying: Place the slurry obtained in step (4) in an oven and dry for 24 hours to obtain the target slurry.

[0049] Comparative Example 1

[0050] 1. Material preparation: Crush the bamboo into powder to 40 mesh to complete the material preparation;

[0051] 2. Synthesis of a eutectic solvent: A eutectic solvent was synthesized using choline chloride and L-lactic acid in a molar ratio of 1:9. The three components were mixed in a flask, placed in an 80°C oil bath, and stirred until a clear, transparent solution was formed.

[0052] 3. For the various operations and parameter settings in the pulping process, please refer to Example 1 above.

[0053] The pulp yield results obtained from the above pulping process are shown in Table 1 below.

[0054] Table 1. Slurry yield results

[0055] Example 1 64％ Example 2 58％ Example 3 59％ Example 4 61％ Comparative Example 1 48％

[0056] As shown in the table above, this invention uses moso bamboo and eutectic bamboo as raw materials. After microwave-assisted eutectic solvent pretreatment, the pulp yield is around 60%, while the pulp yield of the comparative example is less than 50%. This indicates that when amino acids are added as cellulose protectants, using eutectic solvents with choline chloride and L-lactic acid as hydrogen bond acceptors and donors can effectively protect cellulose from degradation during cooking and improve pulp yield.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing pulp from bamboo raw materials by cooking with a ternary eutectic solvent, characterized in that, The method includes the following steps: S1 mixes bamboo raw materials with a ternary eutectic solvent in a certain proportion and reacts them in a microwave oven at 120℃~140℃ and 500W~700W for 10min~30min. S2 was then washed sequentially with acetone solution, anhydrous ethanol, and deionized water until neutral, and then dried to obtain fiber residue, which is the target sizing agent. The preparation method of the ternary eutectic solvent is as follows: under the condition of 70℃~90℃, choline chloride, amino acids and L-lactic acid solution are mixed in a molar ratio of 1:0.01-0.1:2-18 and heated and stirred continuously until a clear and transparent solution is formed to obtain the ternary eutectic solvent. The amino acid is one or more of L-arginine, L-tyrosine, and L-glycine.

2. The method as described in claim 1, characterized in that, The raw materials are selected from moso bamboo or ci bamboo, and are crushed to 30-50 mesh to obtain the initial raw materials.

3. The method as described in claim 1, characterized in that, The acetone solution in S2 is a 50% acetone solution.

4. The method as described in claim 1, characterized in that, The molar ratio of the mixture of choline chloride, amino acids and L-lactic acid is 1:0.03-0.08:6-15.

5. The method as described in claim 4, characterized in that, The molar ratio of the mixture of choline chloride, amino acids and L-lactic acid is 1:0.04-0.06:7-11.

6. The method as described in claim 5, characterized in that, The molar ratio of choline chloride, amino acids and L-lactic acid is 1:0.05:

9.

7. The method as described in claim 1, characterized in that, In S1, the reaction is carried out in a microwave oven at 125℃~135℃ and 500W~700W for 15min~25min.

8. The method as described in claim 1, characterized in that, In S1, the reaction was carried out in a microwave oven at 130°C and 600W for 20 minutes.

9. The slurry obtained by the method according to any one of claims 1 to 8.