Traditional mulberry and paper mulberry bark pulp and rapid preparation method thereof

Abstract

The invention relates to the technical field of pulping and papermaking, in particular to traditional mulberry bark pulp and a rapid preparation method thereof. A rapid preparation method of traditional mulberry and paper mulberry bark pulp comprises the following steps that paper mulberry bark is soaked and then cleaned for use; then, first-stage cooking and second-stage cooking are performed, and finally, the cooked skin materials are placed in water to be cleaned, so that the traditional mulberry and paper mulberry skin pulp is obtained. Compared with a traditional sodium hydroxide cooking process, the preparation method of the mulberry and paper mulberry bark pulp makes remarkable progress in the aspects of improving the comprehensive performance of paper and optimizing the production efficiency and environmental friendliness. The physical properties of the paper prepared by the technical scheme are remarkably improved, and the folding strength, the aging resistance and other key indexes are remarkably superior to those of the paper prepared by a traditional sodium hydroxide cooking process. According to the technical scheme, the production period is greatly shortened, and the efficiency is remarkably improved. And meanwhile, a full-chlorine-free clean production process is realized, and the development direction of clean production and circular economy in the current pulping and papermaking industry is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pulp and papermaking, and more particularly to a traditional mulberry bast pulp and a rapid preparation method thereof. BACKGROUND

[0002] As an important material carrier of Chinese civilization, mulberry bast paper has carried the cultural functions of classics inheritance, painting and calligraphy art, and document archives since the Han Dynasty. Traditional handmade paper using mulberry bast fiber as the main raw material still plays an irreplaceable role in the fields of painting creation and special archive paper. However, the existing traditional mulberry bast paper pulp manufacturing technology still relies on the traditional process route of soaking, lime steaming, bleaching, and rinsing, and has problems such as long production cycle (usually taking 12-15 days), complex process, and high labor intensity. The document “Influence of Raw Materials and Pulping Process on the Performance of Jingxian Bast Paper” (Journal of Fudan University (Natural Science Edition) Vol. 62 No. 5 October 2023) discloses a method of using caustic soda cooking to shorten the process, but this method introduces sodium hypochlorite bleaching, which has increasingly strict limitations on chlorine-containing wastewater discharge and adsorbable organic halide pollution under environmental protection regulations, and is difficult to meet the technical needs of contemporary clean production and efficient pulping. Moreover, strong alkali cooking and sodium hypochlorite bleaching can cause damage to the internal chemical structure of the paper, which is more obvious during the aging process. SUMMARY

[0003] The present application provides a rapid preparation method of traditional mulberry bast pulp to overcome the defects of the prior art.

[0004] The present application also provides a traditional mulberry bast pulp.

[0005] To solve the above technical problems, the technical solutions of the present application are as follows: A rapid preparation method of traditional mulberry bast pulp, comprising the following steps: S1, soaking and then cleaning the bast, for standby use; S2, first-stage cooking: loading the cleaned bast into a cooking pot, adding cooking liquid A to the cooking pot at a liquid ratio of 1 kg : 8-20 L, and then adding sodium silicate for cooking; the first-stage cooking conditions are: heating the cooking pot to 90-100℃, maintaining for 2-2.5 hours, and then cooling to 70-80℃ for 6-7 hours; S3, second-stage cooking: directly adding sodium carbonate, hydrogen peroxide, and sodium silicate to the cooking pot after the first-stage cooking is completed; the second-stage cooking conditions are: heating to 90-100℃, maintaining for 1.5-2 hours, and then cooling to 70-80℃ for 6-7 hours; S4, washing treatment: cleaning the cooked bast in water to obtain the traditional mulberry bast pulp.

[0006] In step S2, the cooking liquor A contains sodium carbonate, hydrogen peroxide, and water. The concentration of sodium carbonate in cooking liquor A is 5.5~6.5 g / L, and the concentration of hydrogen peroxide is 3.5~4.5 g / L. The amount of sodium silicate added is 0.5%~1.5% of the oven-dry weight of the paper mulberry bark. In step S3, the amount of sodium carbonate and hydrogen peroxide added again is based on the volume of cooking liquor A in step S2, with 3.5-4 g of sodium carbonate added per liter and 2-2.2 g of hydrogen peroxide added per liter, based on the volume of cooking liquor A in step S2; the amount of sodium silicate added is 0.5%-1.5% of the oven-dry weight of paper mulberry bark in step S2. Preferably, in step S1, the soaking time is not less than 2 hours.

[0007] Preferably, in step S2, the concentration of sodium carbonate in the cooking liquid A is 5.8~6.2 g / L and the concentration of hydrogen peroxide is 3.8~4.2 g / L.

[0008] Preferably, the liquid ratio in step S2 is 1 kg : 15~20 L.

[0009] Preferably, the heating rate in step S2 is 1~3℃ / min.

[0010] Preferably, in step S3, the amount of sodium carbonate and hydrogen peroxide added again is 3.5 g of sodium carbonate per liter based on the volume of cooking liquor A in step S2, and the amount of hydrogen peroxide added again is 2 g per liter based on the volume of cooking liquor A in step S2; the amount of sodium silicate added is 1% of the oven-dry mulberry bark mass in step S2. Preferably, the heating rate in step S3 is 1~3℃ / min.

[0011] Preferably, the cleaning in step S4 includes cleaning with hot water at a temperature of 65~70℃, followed by cleaning with room temperature cold water.

[0012] Preferably, the cleaning time in step S4 is 8 to 10 minutes.

[0013] Preferably, the cleaning in step S4 includes cleaning until the pH of the cleaning solution is 7-8.

[0014] Traditional methods for producing paper mulberry bark are time-consuming and cumbersome. This invention presents a chlorine-free, short-process pulping system: through a two-stage, gentle deligninization process, the production cycle is significantly shortened compared to traditional methods; a synergistic system of sodium carbonate, hydrogen peroxide, and sodium silicate is employed to achieve selective lignin dissolution at low temperatures (≤100℃), avoiding severe oxidative degradation of cellulose macromolecules; this system eliminates the generation of adsorbable organic halides and carcinogenic chlorinated compounds at the source, achieving a synergistic improvement in clean production and fiber strength.

[0015] In this invention, the mild delignin-removing effect of the sodium carbonate and hydrogen peroxide system effectively reduces the degradation of cellulose macromolecules, while the buffering and stabilizing effect of sodium silicate protects the fiber strength, making the paper fiber structure more uniform and tough, thus meeting the stringent requirements for paper durability in high-end applications such as calligraphy and painting.

[0016] The paper prepared by this invention is particularly suitable for high-value-added specialty paper fields such as calligraphy and painting paper and archival storage paper, and has good economic and social benefits for inheriting my country's traditional papermaking techniques and promoting industrial upgrading.

[0017] Compared with the prior art, the beneficial effects of the technical solution of the present invention are: The mulberry bark pulp preparation method described in this invention represents a significant improvement over the traditional sodium hydroxide cooking process in terms of enhancing overall paper performance, optimizing production efficiency, and improving environmental friendliness. The paper produced using this invention exhibits significantly improved physical properties, with key indicators such as folding endurance and anti-aging performance being significantly superior to those produced using the traditional sodium hydroxide cooking process.

[0018] The technical solution of this invention significantly shortens the production cycle and greatly improves efficiency. It also achieves a completely chlorine-free clean production process. This not only enables the pulp brightness to reach over 75%, but also aligns with the current development direction of clean production and circular economy in the pulp and paper industry. Attached Figure Description

[0019] Figure 1 This is a picture of the traditional mulberry bark pulp preparation process. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0021] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0022] The present invention will be further described below: A rapid method for preparing traditional mulberry bark pulp includes the following steps: S1. Soak the paper mulberry bark in water and then wash it; set aside. S2, First stage of cooking: Put the washed paper mulberry bark into the cooking pot, add cooking liquid A to the cooking pot, the liquid ratio is 1kg : 8~20 L, and then add sodium silicate for cooking; The conditions for the first stage of cooking are: heat the cooking pot to 90~100℃, maintain for 2~2.5 hours, and then cool down to 70~80℃ and keep warm for 6~7 hours; S3. Second stage of cooking: After the first stage of cooking is completed, sodium carbonate, hydrogen peroxide and sodium silicate are added directly to the cooking pot again. The conditions for the second stage of cooking are: heat up to 90~100℃, maintain for 1.5~2 hours, then cool down to 70~80℃ and keep warm for 6~7 hours. S4. Washing treatment: The boiled leather is washed in water to obtain traditional mulberry bark pulp.

[0023] In step S2, the cooking liquor A contains sodium carbonate, hydrogen peroxide, and water. The concentration of sodium carbonate in cooking liquor A is 5.5~6.5 g / L, and the concentration of hydrogen peroxide is 3.5~4.5 g / L. The amount of sodium silicate added is 0.5%~1.5% of the oven-dry weight of the paper mulberry bark. In step S3, the amount of sodium carbonate and hydrogen peroxide added again is based on the volume of cooking liquor A in step S2, with 3.5~4 g of sodium carbonate added per liter and 2~2.2 g of hydrogen peroxide added per liter, based on the volume of cooking liquor A in step S2; the amount of sodium silicate added is 0.5%~1.5% of the dry weight of paper mulberry bark in step S2.

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Example 1

[0025] A rapid method for preparing traditional mulberry bark pulp includes the following steps: S1 Take the paper mulberry bark, soak it in room temperature (25℃) water for 2 hours, then wash it and set aside.

[0026] S2 First stage of cooking: The cleaned paper mulberry bark is placed into the cooking pot, and then cooking liquid A is poured into the cooking pot. The concentration of sodium carbonate in cooking liquid A is 6 g / L and the concentration of hydrogen peroxide is 4 g / L. The liquid ratio is 1 kg : 20 L (kg of oven-dried paper mulberry bark material : cooking liquid A). Then 1% sodium silicate is added (based on the mass of oven-dried paper mulberry bark, that is, 10 kg of sodium silicate is added for every 1 t of oven-dried paper mulberry bark material). The cooking conditions are as follows: the temperature is increased to 95℃ at a rate of 2℃ / min, kept at that temperature for 2 hours, and then the temperature is reduced to 70℃ and kept at that temperature for 6 hours to complete the first stage of cooking.

[0027] S3 Second stage cooking: Continue to add the following agents to the cooking pot: add 3.5 g / L sodium carbonate, 2 g / L hydrogen peroxide (based on the volume of cooking liquid A in S2, add 3.5 g of sodium carbonate and 2 g of hydrogen peroxide per liter), and add 1% sodium silicate (based on the weight of oven-dried paper mulberry bark in S2, i.e., add 10 kg of sodium silicate per ton of oven-dried paper mulberry bark). The cooking conditions are as follows: the temperature is increased to 95℃ at a rate of 2℃ / min, held for 1.5 h, then decreased to 70℃ and held for 6 h to complete the second stage of cooking.

[0028] S4 involves washing the steamed bark in 70°C hot water for 10 minutes to remove the gum, and then rinsing it in room temperature (25°C) water to obtain traditional mulberry bark pulp.

[0029] Using traditional mulberry bark pulp at 23 g / m 2 For quantitative papermaking, wet paper webs are prepared using a Kaiser process paper sheet forming device. The wet paper webs are pressed in a paper press for 5 minutes (400 kPa). The pressed wet paper webs are then flatly brushed onto the drying plate of a flatbed dryer and dried at 60°C for 5 minutes before being peeled off to obtain mulberry bark paper. The physicochemical properties are then tested.

[0030] Example 2 A rapid method for preparing traditional mulberry bark pulp includes the following steps: S1 Take the paper mulberry bark, soak it in room temperature (25℃) water for 2 hours, then wash it and set aside.

[0031] S2 First stage of cooking: The cleaned paper mulberry bark is placed into the cooking pot, and then cooking liquid A is poured into the cooking pot. The concentration of sodium carbonate in cooking liquid A is 5.5 g / L, the concentration of hydrogen peroxide is 3.5 g / L, and the liquid ratio is 1 kg : 8 L (kg of oven-dried paper mulberry bark: cooking liquid A). Then 1% sodium silicate is added (based on the mass of oven-dried paper mulberry bark, that is, 10 kg of sodium silicate is added for every 1 t of oven-dried paper mulberry bark). The cooking conditions are as follows: the temperature is increased to 95℃ at a rate of 2℃ / min, kept at that temperature for 2 hours, and then the temperature is reduced to 70℃ and kept at that temperature for 6 hours to complete the first stage of cooking.

[0032] S3 Second stage cooking: Continue to add the following agents to the cooking pot: add 3.5 g / L sodium carbonate, 2 g / L hydrogen peroxide (based on the volume of cooking liquid A in S2), and add 1% sodium silicate (based on the weight of oven-dried paper mulberry bark in S2, i.e., 10 kg of sodium silicate per 1 t of oven-dried paper mulberry bark). The cooking conditions are as follows: the temperature is increased to 95℃ at a rate of 2℃ / min, held for 1.5 h, then decreased to 70℃ and held for 6 h to complete the second stage of cooking.

[0033] S4 involves washing the steamed bark in 70°C hot water for 10 minutes to remove the gum, and then rinsing it in room temperature (25°C) water to obtain traditional mulberry bark pulp.

[0034] The papermaking method and testing are the same as in Example 1.

[0035] Example 3 A rapid method for preparing traditional mulberry bark pulp includes the following steps: S1 Take the paper mulberry bark, soak it in room temperature (25℃) water for 2 hours, then wash it and set aside.

[0036] S2 First stage of cooking: The cleaned paper mulberry bark is placed into the cooking pot, and then cooking liquid A is poured into the cooking pot. The concentration of sodium carbonate in cooking liquid A is 6.5 g / L and the concentration of hydrogen peroxide is 4.5 g / L. The liquid ratio is 1 kg : 15 L (kg of oven-dried paper mulberry bark material : cooking liquid A). Then 1% sodium silicate is added (based on the mass of oven-dried paper mulberry bark, that is, 10 kg of sodium silicate is added for every 1 t of oven-dried paper mulberry bark material). The cooking conditions are as follows: the temperature is increased to 95℃ at a rate of 2℃ / min, kept at that temperature for 2 hours, and then the temperature is reduced to 70℃ and kept at that temperature for 6 hours to complete the first stage of cooking.

[0037] S3 Second stage cooking: Continue to add the following agents to the cooking pot: add 4.0 g / L sodium carbonate, 2.2 g / L hydrogen peroxide (based on the volume of cooking liquid A in S2), and add 1% sodium silicate (based on the weight of oven-dried paper mulberry bark in S2, i.e., 10 kg of sodium silicate per 1 t of oven-dried paper mulberry bark). The cooking conditions are as follows: the temperature is increased to 95℃ at a rate of 2℃ / min, held for 1.5 h, then decreased to 70℃ and held for 6 h to complete the second stage of cooking.

[0038] S4 involves washing the steamed bark in 70°C hot water for 10 minutes to remove the gum, and then rinsing it in room temperature (25°C) water to obtain traditional mulberry bark pulp.

[0039] The papermaking method and testing are the same as in Example 1.

[0040] Comparative Example 1 A method for preparing pulp from mulberry bark by cooking with sodium hydroxide includes the following steps: (1) Soaking: Soak the paper mulberry bark raw material in room temperature water for 24 hours, changing the water once during the period, so that the moisture content of the raw material reaches 70%.

[0041] (2) Cooking: Sodium hydroxide cooking process is adopted, and the specific parameters are as follows: Alkali dosage: Based on the oven-dried weight of paper mulberry bark, the dosage of sodium hydroxide (NaOH) is 17%; Liquid ratio: 1:8 (mass of oven-dried paper mulberry bark (kg) : volume of water (L)); Heating program: After heating to 75℃, keep warm for 12 hours; Control the cooking hardness to 16 (the kappa value at the end of cooking is 16). Residual alkali: 6% residual alkali in the black liquor after cooking (residual alkali content is 6%); (3) Washing: Take out the steamed paper mulberry bark, rinse it with 70℃ hot water for 10 minutes to remove the outer skin and gum, and then wash it with room temperature running water; (4) Composting: The leather material washed in step (3) is piled up at room temperature for 4 days, with a pile temperature of 45~55℃, and turned over once a day; (5) Bleaching: At room temperature (25℃), the leather obtained in step (4) is bleached for 7 hours with an effective chlorine content of 4% sodium hypochlorite aqueous solution. The liquid ratio is 1 kg: 10 L (dry weight of leather kg: volume of sodium hypochlorite aqueous solution L). The pH value at the bleaching endpoint is 10.

[0042] (6) Pulping: Using conventional methods, the bleached pulp (5) is placed in a pulping device. After 40 minutes of cutting and stirring by the pulping device, pulp with a freeness of 40°SR is obtained. Impurities are removed by a sand remover and a round screen to obtain mulberry bark pulp.

[0043] The papermaking method and testing are the same as in Example 1.

[0044] The total process cycle of this comparative example is more than twice that of the example, resulting in lower production efficiency.

[0045] Comparative Example 2 This comparative example is similar to Example 1, except that the second stage of cooking in step S3 is not used.

[0046] Comparative Example 3 This comparative example is similar to Example 1, except that in step S2, the concentration of sodium carbonate in cooking liquid A is 3 g / L and the concentration of hydrogen peroxide is 2 g / L; in step S3, the second stage of cooking is: the following agents are added to the cooking pot: 2 g / L sodium carbonate and 1 g / L hydrogen peroxide are added.

[0047] Analysis and testing: Whiteness was determined according to GB / T 7974-2013 Determination of Blue Light Diffuse Reflectance Factor D65 Brightness of Paper, Paperboard and Pulp (Diffuse / Vertical Method, Outdoor Daylight Conditions); Aging Resistance Whiteness was determined according to GB / T 464-2008 Accelerated Dry Heat Aging of Paper and Paperboard; Folding Endurance was determined according to GB / T 457-2008 Folding Endurance of Paper and Paperboard. The test results are shown in the table below: Table 1. Detection Results Data for Examples and Comparative Examples

[0048] Results analysis: Examples 1-3 of this invention achieve rapid preparation of traditional mulberry bark pulp in a shorter cycle and realize completely chlorine-free clean production. The pulp brightness reaches over 75.6%, while mechanical strength and aging resistance are also significantly improved. In particular, Example 1, using a liquor ratio of 1:20 and pulping conditions of 6 g / L sodium carbonate and 4 g / L hydrogen peroxide, achieves the best overall pulp performance: brightness reaches 78.7%, aging resistance brightness decreases by only 0.3%, and longitudinal folding endurance reaches 1271 times, an improvement of 171% compared to Comparative Example 1 (469 times).

[0049] Comparative Example 1 uses traditional caustic soda cooking and sodium hypochlorite bleaching (liquid ratio 1:8), resulting in a pulp whiteness of only 64.2%, which is significantly lower than the technical solution of this invention. The aging resistance whiteness decreases by 5.0%, and the folding endurance is 469 times (only 36%~46% of that of this invention).

[0050] As can be seen from Comparative Example 2, because the second stage of cooking was not carried out, the raw materials could not be fully dissociated / could not be formed into paper, so subsequent testing could not be performed.

[0051] As can be seen from Comparative Example 3, the pulp obtained without adopting the technical solution of the present invention has significantly reduced whiteness and mechanical properties, as well as significantly reduced aging resistance.

[0052] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A rapid preparation method for traditional mulberry bark pulp, characterized in that, Includes the following steps: S1. Soak the paper mulberry bark in water and then wash it; set aside. S2, First stage of cooking: Put the cleaned paper mulberry bark into the cooking pot, add cooking liquid A to the cooking pot, the liquid ratio is 1 kg : 8~20 L, and then add sodium silicate for cooking; the conditions for the first stage of cooking are: heat the cooking pot to 90~100℃, maintain for 2~2.5 hours, and then cool down to 70~80℃ and keep warm for 6~7 hours; S3. Second stage of cooking: After the first stage of cooking is completed, sodium carbonate, hydrogen peroxide and sodium silicate are added directly to the cooking pot again; The conditions for the second stage of cooking are: heat up to 90~100℃, maintain for 1.5~2 hours, then cool down to 70~80℃ and keep warm for 6~7 hours. S4. Washing process: Wash the steamed paper mulberry bark in water to obtain traditional paper mulberry bark pulp; In step S2, the cooking liquor A contains sodium carbonate, hydrogen peroxide, and water. The concentration of sodium carbonate in cooking liquor A is 5.5~6.5 g / L, and the concentration of hydrogen peroxide is 3.5~4.5 g / L. The amount of sodium silicate added is 0.5%~1.5% of the oven-dry weight of the paper mulberry bark. In step S3, the amount of sodium carbonate and hydrogen peroxide added again is based on the volume of cooking liquor A in step S2, with 3.5-4 g of sodium carbonate added per liter and 2-2.2 g of hydrogen peroxide added per liter, based on the volume of cooking liquor A in step S2; the amount of sodium silicate added is 0.5%-1.5% of the dry weight of paper mulberry bark in step S2.

2. The rapid preparation method of traditional mulberry bark pulp according to claim 1, characterized in that, In step S1, the soaking time shall not be less than 2 hours.

3. The rapid preparation method of traditional mulberry bark pulp according to claim 1, characterized in that, In step S2, the concentration of sodium carbonate in the cooking liquid A is 5.8~6.2 g / L and the concentration of hydrogen peroxide is 3.8~4.2 g / L.

4. The rapid preparation method of traditional mulberry bark pulp according to claim 1, characterized in that, The liquid ratio in step S2 is 1 kg : 15~20 L.

5. The rapid preparation method of traditional mulberry bark pulp according to claim 1, characterized in that, The heating rate in step S2 is 1~3℃ / min; the heating rate in step S3 is 1~3℃ / min.

6. The rapid preparation method of traditional mulberry bark pulp according to claim 1, characterized in that, In step S3, the amount of sodium carbonate and hydrogen peroxide added again is based on the volume of cooking liquid A in step S2, with 3.5g of sodium carbonate added per liter and 2g of hydrogen peroxide added per liter; the amount of sodium silicate added is 1% of the dry mulberry bark mass in step S2.

7. The rapid preparation method of traditional mulberry bark pulp according to claim 1, characterized in that, The cleaning process in step S4 includes cleaning with hot water at a temperature of 65~70℃, followed by rinsing with room temperature cold water.

8. A traditional mulberry bark pulp prepared by the rapid preparation method according to any one of claims 1-7.

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