Method for preparing dissolving pulp from bleached bamboo pulp
By using fiber sieving and alkaline eutectic solvent DES refining method, the problem of removing impurities and hemicellulose in bleached bamboo pulp was solved, and high-purity, highly reactive dissolving pulp preparation was achieved.
Patent Information
- Application Number
- CN202511185735.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-22
- Publication Date
- 2025-11-04
AI Technical Summary
Existing technologies are insufficient to efficiently remove impurities and hemicellulose from bleached bamboo pulp, resulting in reduced purity and reactivity of the dissolved pulp, which affects the effectiveness and cost of subsequent processing.
The method employs fiber sieving and alkaline eutectic solvent DES refining. By sieving, impurities are removed, and alkaline DES prepared under specific conditions with choline hydroxide and urea is reacted with bleached bamboo pulp to remove hemicellulose and improve cellulose purity.
The increased α-cellulose content and decreased hemicellulose content improved the purity and reactivity of the dissolving pulp, resulting in a high-purity, highly accessible dissolving pulp.
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Figure CN120889152A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of fiber raw material manufacturing, and particularly relates to a method for preparing dissolving pulp by fiber grading and screening in cooperation with alkali deep eutectic solvent refining bleached bamboo pulp. BACKGROUND Dissolving pulp is a kind of special chemical pulp with high alpha-cellulose purity (> 90%), which is prepared by removing hemicellulose and lignin during pulping. The hemicellulose content is generally 1%-10%, and the lignin content is less than 0.05%. At present, dissolving pulp has been widely used in the production of cellulose derivatives, such as cellulose acetate, nitrocellulose, viscose, rayon, methyl cellulose and carboxymethyl cellulose. Dissolving pulp is usually prepared by pulping and cooking of cotton linters and wood. However, due to the relative scarcity of wood resources in China, bamboo, which is widely distributed, has become an ideal choice for replacing wood to prepare dissolving pulp because of its fast growth rate and cellulose and hemicellulose content comparable to that of broad-leaved wood and softwood. The method for preparing dissolving pulp by refining bleached bamboo pulp has attracted widespread attention and research.
[0002] Bleached bamboo pulp is derived from different parts of bamboo, and the morphology and chemical composition of its fiber cells are different. Among them, the heterogeneous cell part has no value for the preparation of dissolving pulp, and the content of ash and transition metal elements is high, which not only affects the subsequent acidification and ash removal process, but also reduces the quality indicators of the finished pulp. In addition, the fine fiber components produced during pulping are prone to form "solvent competition" with long fibers, which significantly hinders the mass transfer efficiency of chemical agents, leading to a decline in treatment effect and an increase in treatment cost. At present, directly upgrading the pulp to dissolving pulp is a more direct, efficient and economically feasible method. Purification technologies include alkali purification (such as cold / hot alkali extraction), enzyme purification, Nitren purification and ionic liquid purification, etc. Among them, alkali purification as a hemicellulose removal process has been widely used on an industrial scale. However, cold alkali extraction can efficiently remove hemicellulose components to improve cellulose purity, but it can change the crystalline structure of cellulose, resulting in reduced reactivity. Single-step pretreatment process has application potential, but it is difficult to simultaneously achieve high cellulose purity and good reactivity.(B. Arnoul-Jarriault et al. / Industrial Crops and Products 65 (2015) 565–571).
[0003] Therefore, there is an urgent need to develop a method for preparing dissolving pulp from bleached bamboo pulp, which effectively solves the above problems to obtain dissolving pulp with high purity and high quality. SUMMARY
[0004] The present application aims to provide a method for producing dissolving pulp by fiber screening in cooperation with alkali deep eutectic solvent DES refining bleached bamboo pulp, so as to solve the problems in the prior art.
[0005] To achieve the above-mentioned object of the present application, the present application provides the following technical solutions. The present application provides a method for preparing dissolving pulp from bleached bamboo pulp, comprising the following preparation steps: (1) After the bleached bamboo pulp is defibrated under certain rotation speed and pulp concentration, screening is performed, and the good pulp retained in front of a certain mesh screen after a certain screening time; (2) Choline hydroxide and urea are stirred at a certain molar ratio at a certain temperature for a certain time to prepare a transparent basic eutectic solvent DES; (3) The screened pulp and a certain concentration of the basic DES are mixed at a certain liquid ratio, and reacted at a certain temperature for a certain time; (4) After the reaction is completed, the DES is collected by vacuum filtration, and the pulp is washed several times with hot water at a certain temperature to obtain clean pulp.
[0006] Preferably, in step (1), the pulp concentration is 1 wt %-1.25 wt %; and the defibration rotation speed is 5000-10000.
[0007] Preferably, in step (1), the screening is performed using a Bauer-McNett fiber screening instrument.
[0008] Preferably, in step (1), the screening time is 5-20 min; and the mesh number of the screen is 50-200.
[0009] Preferably, in step (2), the molar ratio of choline hydroxide to urea is 1:1-1:35; the step reaction temperature is 60-80℃; and the step stirring time is 30min-90min.
[0010] Preferably, in step (3), the concentration of the basic DES is 35-55wt %.
[0011] Preferably, the solid-liquid ratio is 1:10-1:20 in terms of mass / volume g / mL.
[0012] Preferably, the reaction temperature is 80-100℃; and the reaction time is 30-150min.
[0013] Preferably, in step (4), the hot water temperature for washing the pulp is 70-90℃; and the number of times of washing the pulp is 5-10.
[0014] The present application also provides a dissolving pulp prepared by the above method.
[0015] The present application has the following beneficial effects: (1) By removing the mixed cells in bleached bamboo pulp through fiber screening, fibers with different structures and properties are grouped, which enhances the reaction speed and efficiency of subsequent refining.
[0016] (2) By alkaline DES refining, the content of a-cellulose in bleached bamboo pulp is increased from 88.22% to 95.11%, the content of hemicellulose is reduced from 14.45% to 4.71%, the alkali solubility S18 is reduced from 5.06% to 1.85%, the alkali solubility S10 is reduced from 6.11% to 3.02%, and the water retention value is increased from 90.77% to 138.63%; a dissolved pulp with high a-cellulose content, low hemicellulose content, high purity and good accessibility is obtained by this method. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 Flow chart for preparing dissolved pulp from bleached bamboo pulp. DETAILED DESCRIPTION
[0018] In order to further understand the present application, the following further describes the present application in combination with the accompanying drawings and examples, but the implementation and protection of the present application are not limited thereto. It should be noted that if the following processes are not specifically described in detail, they can be implemented or understood by those skilled in the art with reference to the prior art. If the reagents or instruments used are not marked with the manufacturer, they are considered to be conventional products that can be purchased on the market.
[0019] Test method: The test method of a-cellulose is GB / T2677.10-1995; The test method of hemicellulose is high performance liquid chromatography (HPLC); The test method of alkali solubility is GB / T5401-2018; The test method of water retention value is GB / T29286-2012.
[0020] In bleached bamboo pulp, the content of a-cellulose is 88.22%, the content of hemicellulose is 14.45%, the alkali solubility S18 is 5.06%, the alkali solubility S10 is 6.11%, and the water retention value is 90.77%.
[0021] Example 1: (1) Take 10g bleached bamboo pulp and defibrate 10000 turns at a pulp concentration of 1wt%; (2) Screen for 20min in a Bauer-McNett fiber screening instrument, and retain 2000 current good pulp; (3) React and stir 30min at 70℃ to obtain a transparent alkaline DES by mixing choline hydroxide and urea at a molar ratio of 1:2. (4) 10 g of the screened pulp was mixed with 40 wt% of the alkaline DES at a solid-liquid ratio of 1:15 (g / mL) and reacted at 90°C for 60 min; (5) After the reaction, the DES was collected by vacuum filtration and the pulp was washed with deionized water at 90°C for 10 times to obtain clean dissolving pulp.
[0022] The obtained dissolving pulp had an a-cellulose content of 90.26%, a hemicellulose content of 8.17%, an alkali solubility S18 of 4.31%, an alkali solubility S10 of 5.17%, and a water retention value of 96.75%.
[0023] Example 2: On the basis of Example 1, only the concentration of the alkaline DES was changed to 50 wt%, and the other conditions were the same as in Example 1.
[0024] The obtained dissolving pulp had an a-cellulose content of 95.11%, a hemicellulose content of 5.04%, an alkali solubility S18 of 1.98%, an alkali solubility S10 of 3.24%, and a water retention value of 114.99%.
[0025] Example 3: (1) 12 g of bleached bamboo pulp was defibrated at a pulp concentration of 1.25 wt% for 10,000 revolutions; (2) The pulp was screened in a Bauer-McNett fiber screen for 20 min, and the pulp with a retention of 20,000 revolutions was collected; (3) Choline hydroxide and urea were reacted at a molar ratio of 1:2 at 70°C for 30 min to obtain a transparent alkaline DES; (4) 10 g of the screened pulp was mixed with 50 wt% of the alkaline DES at a solid-liquid ratio of 1:15 (g / mL) and reacted at 100°C for 150 min; (5) After the reaction, the DES was collected by vacuum filtration and the pulp was washed with deionized water at 90°C for 10 times to obtain clean dissolving pulp.
[0026] The obtained dissolving pulp had an a-cellulose content of 94.31%, a hemicellulose content of 4.71%, an alkali solubility S18 of 1.85%, an alkali solubility S10 of 3.02%, and a water retention value of 103.94%.
[0027] Example 4: On the basis of Example 3, only the reaction time of the alkaline DES was changed to 90 min, and the other conditions were the same as in Example 3.
[0028] The obtained dissolving pulp has an alpha-cellulose content of 94.10%, a hemicellulose content of 4.98%, an alkali solubility S18 of 1.93%, an alkali solubility S10 of 3.25%, and a water retention value of 138.63%.
[0029] Example 5: (1) 10 g of bleached bamboo pulp was defibrated at a pulp concentration of 1.25 wt% for 9000 revolutions; (2) screening in a Bauer-McNett fiber screening instrument for 20 min, and collecting the good pulp with a retention of 200 microns; (3) choline hydroxide and urea were reacted at a molar ratio of 1:2 at 70 DEG C for 30 min to obtain a transparent alkaline DES; (4) 10 g of the screened good pulp was mixed with 50 wt% of the alkaline DES at a liquid ratio of 1:18, and reacted at 90 DEG C for 60 min; (5) after the reaction was completed, the DES was collected by vacuum filtration, and the pulp was washed with 90 DEG C deionized water for 10 times to obtain clean dissolving pulp.
[0030] The obtained dissolving pulp has an alpha-cellulose content of 93.96%, a hemicellulose content of 5.33%, an alkali solubility S18 of 2.79%, an alkali solubility S10 of 4.33%, and a water retention value of 111.55%.
[0031] Example 6: On the basis of Example 5, only the liquid-solid ratio of the alkaline DES was changed to 1:20 in terms of mass-volume ratio g / mL, and the other conditions were completely consistent with Example 5.
[0032] The obtained dissolving pulp has an alpha-cellulose content of 93.50%, a hemicellulose content of 5.38%, an alkali solubility S18 of 2.83%, an alkali solubility S10 of 4.38%, and a water retention value of 119.17%.
[0033] Example 7: (1) 10 g of bleached bamboo pulp was defibrated at a pulp concentration of 1.2 wt% to 5 wt% for 10000 revolutions; (2) screening in a Bauer-McNett fiber screening instrument for 20 min, and collecting the good pulp with a retention of 200 microns; (3) choline hydroxide and urea were reacted at a molar ratio of 1:2 at 70 DEG C for 30 min to obtain a transparent alkaline DES; (4) 10 g of the screened good pulp was mixed with 50 wt% of the alkaline DES at a liquid ratio of 1:20 in terms of mass-volume ratio g / mL, and reacted at 100 DEG C for 120 min; (5) After the reaction is completed, the DES is collected by vacuum filtration, and the slurry is washed with deionized water at 90°C for 10 times to obtain clean dissolved pulp.
[0034] In the obtained dissolved pulp, the content of a-cellulose is 93.33%, the content of hemicellulose is 5.14%, the alkali solubility S18 is 2.67%, the alkali solubility S10 is 4.17%, and the water retention value is 112.86%.
[0035] Example 8: (1) 10 g of bleached bamboo pulp is defibrated at a pulp concentration of 1 wt% for 5000 revolutions; (2) The pulp is screened in a Bauer-McNett fiber screening instrument for 5 min, and the pulp with a particle size of 50 microns is collected; (3) Choline hydroxide and urea are reacted and stirred at a molar ratio of 1:1 at 60°C for 30 min to obtain a transparent alkaline DES; (4) 10 g of the screened pulp is mixed with 35 wt% of the alkaline DES at a solid-liquid ratio of 1:10 (g / mL), and the mixture is reacted at 80°C for 30 min; (5) After the reaction is completed, the DES is collected by vacuum filtration, and the slurry is washed with deionized water at 70°C for 5 times to obtain clean dissolved pulp.
[0036] In the obtained dissolved pulp, the content of a-cellulose is 89.11%, the content of hemicellulose is 9.68%, the alkali solubility S18 is 4.99%, the alkali solubility S10 is 6.01%, and the water retention value is 91.31%.
[0037] Example 9: On the basis of Example 8, only the molar ratio of choline hydroxide and urea is changed to 1:3 1:5, and the other conditions are the same as in Example 8.
[0038] In the obtained dissolved pulp, the content of a-cellulose is 89.54%, the content of hemicellulose is 9.38%, the alkali solubility S18 is 4.89%, the alkali solubility S10 is 5.93%, and the water retention value is 92.04%.
[0039] Example 10: On the basis of Example 8, choline hydroxide and urea are reacted and stirred at a molar ratio of 1:1 at 80°C for 90 min to obtain a transparent alkaline DES, and the other conditions are the same as in Example 8.
[0040] In the obtained dissolved pulp, the content of a-cellulose is 89.24%, the content of hemicellulose is 9.48%, the alkali solubility S18 is 4.91%, the alkali solubility S10 is 5.96%, and the water retention value is 92.24%.
[0041] Example 11: (1) Take 10 g of bleached bamboo pulp to be defibrated for 10000 turns at a pulp concentration of 1 wt%; (2) Screen for 20 min in a Bauer-McNett fiber screening instrument, and retain 200 micron good pulp; (3) Stir 60 min at 70℃ to obtain a transparent alkaline DES by reacting choline hydroxide and urea at a molar ratio of 1:2; (4) Mix 10 g of screened good pulp with 55 wt% alkaline DES at a solid-liquid ratio of 1:10 (g / mL) at 80℃ for 60 min; (5) After the reaction is completed, collect the DES by vacuum filtration, and wash the pulp with 70℃ deionized water for 10 times to obtain clean dissolved pulp.
[0042] The obtained dissolved pulp has an α-cellulose content of 94.70%, a hemicellulose content of 4.96%, an alkali solubility S18 of 1.89%, an alkali solubility S10 of 3.14%, and a water retention value of 106.35%.
[0043] In summary, the method for refining bleached bamboo pulp to prepare dissolved pulp by screening and alkaline DES provided by the application has the following beneficial effects: (1) The method removes impurities in the bleached bamboo pulp by fiber screening, and groups fibers with different structures and properties, thereby enhancing the reaction speed and efficiency of subsequent refining; (2) By alkaline DES refining, the α-cellulose content of the bleached bamboo pulp is increased from 88.22% to 95.11%, the hemicellulose content is reduced from 14.45% to 4.71%, the alkali solubility S18 is reduced from 5.06% to 1.85%, the alkali solubility S10 is reduced from 6.11% to 3.02%, and the water retention value is increased from 90.77% to 138.63%; and a dissolved pulp with high α-cellulose content, low hemicellulose content, high purity and good accessibility is obtained.
Claims
1. A method for preparing dissolving pulp from bleached bamboo pulp, characterized in that, The preparation steps include the following: (1) After the bleached bamboo pulp is loosened under certain rotation speed and pulp concentration conditions, it is screened. After a certain screening time, the good pulp is retained in front of a screen with a certain mesh size. (2) Prepare a transparent alkaline eutectic solvent DES by mixing choline hydroxide and urea in a certain molar ratio at a certain temperature for a certain time; (3) The slurry after screening is mixed with a certain concentration of alkaline eutectic solvent DES at a certain material-liquid ratio and reacted at a certain temperature for a certain time; (4) After the reaction is complete, vacuum filter to collect DES, and wash the slurry several times with hot water at a certain temperature to obtain a clean slurry.
2. The method for preparing dissolving pulp from bleached bamboo pulp according to claim 1, characterized in that, In step (1), the pulp concentration is 1 wt%-1.2 wt%-5 wt%; the decomposition revolutions are 5000-10000 revolutions.
3. The method for preparing dissolving pulp from bleached bamboo pulp according to claim 1, characterized in that, The sieving in step (1) is performed using a Bauer-McNett fiber sieve.
4. The method for preparing dissolving pulp from bleached bamboo pulp according to claim 1, characterized in that, The sieving time in step (1) is 5-20 min; the mesh size of the sieve plate for sieving and retaining good pulp is 50-200 mesh.
5. The method for preparing dissolving pulp from bleached bamboo pulp according to claim 1, characterized in that, In step (2), the molar ratio of choline hydroxide to urea is 1:1 to 1:53; the reaction temperature is 60-80℃; and the stirring time is 30-90 min.
6. A method for preparing dissolving pulp from bleached bamboo pulp according to claim 1, characterized in that, The concentration of alkaline DES in step (3) is 35-55 wt%.
7. The method for preparing dissolving pulp from bleached bamboo pulp according to claim 1, characterized in that, In step (3), the material-to-liquid ratio is expressed as a mass-to-volume ratio in g / mL, and is 1:10-1:
20.
8. The method for preparing dissolving pulp from bleached bamboo pulp according to claim 1, characterized in that, The reaction temperature in step (3) is 80-100℃; the reaction time is 30-150min.
9. The method for preparing dissolving pulp from bleached bamboo pulp according to claim 1, characterized in that, The hot water temperature for washing the slurry in step (4) is 70-90℃; the number of washing cycles is 5-10.
10. A dissolving slurry, characterized in that, It is prepared by the method described in any one of claims 1-9.