A method for improving the high-yield pulp properties of bamboo

Abstract

This invention provides a method for improving the properties of high-yield bamboo pulp, comprising: (1) bamboo softening, using Na2SO3 to treat bamboo strips at a certain temperature to soften their structure; (2) mechanical extrusion, using spiral mechanical equipment to extrude the softened bamboo strips to tear and break them apart; (3) impregnation treatment, using H2O2 to treat the mechanically extruded bamboo strips to improve their whiteness; then, the bamboo material undergoes subsequent refining, de-flaking, and washing. The high-yield bamboo pulp preparation method of this invention can achieve a pulp yield of over 75%, a whiteness of 25% to 30% ISO, and a freeness of 20 to 25°SR, and has a wide range of applications; in addition, the two-stage chemical treatment using Na2SO3 + H2O2 can convert residual Na2SO3 in the system into Na2SO4 under the action of H2O2, thereby reducing SO3 in the wastewater. 2‑ The content of [something] effectively reduces the difficulty of wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of pulp and paper technology, and in particular relates to a method for improving the performance of high-yield bamboo pulp. Background Technology

[0002] Bamboo's fiber morphology and chemical composition exhibit good pulping and papermaking performance. In terms of pulping performance and pulp strength, bamboo is an excellent plant fiber raw material for papermaking, second only to coniferous wood and close to broadleaf wood. With the development of the papermaking industry, replacing wood with bamboo to alleviate the pressure on the industry's demand for timber raw materials and meeting the requirements of ecological environmental protection provides a broad development opportunity for bamboo pulp papermaking. For a long time, the technology of using bamboo, a non-wood plant, as a fiber raw material to manufacture pulp has received considerable attention.

[0003] With the implementation of my country's ban on waste paper imports, there is a severe shortage of raw materials for packaging paperboard production made from waste paper. To compensate for the shortfall in imported waste paper, the market demand for high-yield bamboo pulp has increased rapidly. Currently, the most mature bamboo pulping method is the sulfate chemical process, which produces bamboo pulp with good performance but high cost. Therefore, it is only used for the production of medium- and high-grade paper and paperboard. The production of packaging paperboard can only use inexpensive high-yield pulp and waste paper pulp. High-yield pulp is produced using a pulping method that involves slight chemical treatment followed by mechanical refining. Currently, the chemical treatment in the production of high-yield bamboo pulp usually uses NaOH. Due to the dense structure of bamboo, the high alkali content results in a dark pulp color, with a pulp brightness of only about 15% ISO and difficulty in bleaching. Using Na2SO3 to treat bamboo chips produces a lighter pulp color, with an unbleached pulp brightness of 25%–30% and easy bleaching. However, the Na2SO3 treatment process produces wastewater containing a large amount of SO3. 2- This increases the difficulty and cost of wastewater treatment, thus limiting the application of Na2SO3 treatment processes.

[0004] Therefore, a method to improve the performance of high-yield bamboo pulp is urgently needed in the industry. Summary of the Invention

[0005] This invention provides a method for improving the properties of high-yield bamboo pulp, employing a two-stage chemical treatment using Na2SO3 + H2O2. This not only improves the pulp's brightness and freeness but also removes residual SO3 from the wastewater. 2- Oxidized to SO4 2- SO3 was eliminated 2- Its impact on wastewater treatment can effectively reduce the difficulty and cost of wastewater treatment.

[0006] This invention is achieved through the following technical solution:

[0007] This invention discloses a method for improving the high yield of bamboo pulp, comprising the following steps:

[0008] (1) Softening treatment: Mix bamboo strips with Na2SO3 aqueous solution containing NaOH and treat at a temperature of 105-165℃ to soften the bamboo strips;

[0009] (2) Mechanical extrusion: The bamboo strips softened in step (1) are extruded by using spiral mechanical equipment to extrude the bamboo strips to cause them to tear and break apart;

[0010] (3) Impregnation treatment: Mix the bamboo material after step (2) with H2O2 to further soften it and improve its whiteness; then, perform grinding, de-flammation and washing processes.

[0011] Further, in step (1), the amount of Na2SO3 relative to bamboo is 5% to 10%, and the amount of NaOH relative to bamboo is 1% to 3%; the solid-liquid ratio during softening is 1:2.5 to 4.5, the softening temperature is 105 to 165℃, and the softening time is 0.5 to 6.0h.

[0012] Furthermore, the extrusion in step (2) is performed by using a spiral extruder to extrude and tear the bamboo, with a compression ratio of 3 to 4:1.

[0013] Further, in step (3), the amount of H2O2 relative to the bamboo material is 6% to 12%, the pH is 10.5 to 12.5, the water content is 65% to 75%, the reaction temperature is 45 to 65℃, and the reaction time is 30 to 60 min.

[0014] The beneficial effects of this invention are as follows:

[0015] The high-yield bamboo pulp produced using this invention achieves a pulp yield of over 75%, a whiteness of over 25%, and a freeness of over 20°SR. It eliminates the need for bleaching and can be used to produce unbleached bamboo pulp paper for calligraphy and painting, sacrificial paper, and other products. Furthermore, the pulping wastewater is free of SO3. 2- The residue can be recovered and treated using alkali recovery methods, allowing for the resource utilization of organic pollutants; alternatively, it can be treated using biological methods to eliminate SO3. 2- It has an inhibitory effect on microorganisms, making wastewater treatment easier and cheaper. Detailed Implementation

[0016] To make the technical problem to be solved, the technical solution and the beneficial effects of the present invention clearer, an embodiment of the present invention is described in detail below.

[0017] Example 1

[0018] The method for improving the high yield of bamboo pulp includes the following steps:

[0019] (1) Softening treatment: Na2SO3 is used at 5% to 8% relative to bamboo, and NaOH is used at 3% relative to bamboo; the solid-liquid ratio during softening is 1:3.5, the softening temperature is 135℃, and the softening time is 4.5h;

[0020] (2) Mechanical extrusion: The bamboo strips softened in step (1) are extruded by using a spiral device to extrude and tear the bamboo strips. The compression ratio of the spiral is 3.5:1.

[0021] (3) Impregnation treatment: Mix the bamboo material after crushing in step (2) with 10% of its weight of H2O2, adjust the pH to 12.0, the moisture content to 70%, the temperature to 60℃, and treat for 45 minutes.

[0022] After impregnation, the bamboo pulp undergoes further refining, desulfurization, and washing. The pulp achieves a brightness of 30% ISO and a freeness of 25°SR. Residual SO3 is present in the wastewater generated during the pulping process. 2- The content is very low, and the wastewater can be treated by alkali recovery, so that the NaOH used in bamboo chip processing can be recycled.

[0023] Comparative Example 1

[0024] Currently, traditional high-yield bamboo pulping methods employ a two-stage process of "NaOH cooking + mechanical refining." After NaOH cooking, the bamboo chips are dark in color, typically below 15% ISO and with a freeness of around 15°SR, making it difficult to achieve a pulp yield of over 70%. If used for the production of unbleached bamboo pulp for calligraphy and painting paper, sacrificial paper, etc., the pulp also needs to be bleached, further reducing the yield and increasing production costs and pollutant generation.

[0025] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the claims. Furthermore, the above description should be understood and implemented by those skilled in the art; therefore, any modifications made based on the disclosure of this invention should be included within the scope of these claims.

Claims

1. A method for improving the high-yield pulp properties of bamboo, comprising the following steps: (1) Softening treatment: Bamboo strips are mixed with Na2SO3 aqueous solution containing NaOH. The amount of Na2SO3 used in the Na2SO3 aqueous solution is 5%~10% of the mass of bamboo, and the amount of NaOH is 1%~3% of the mass of bamboo. The bamboo strips are softened by high temperature treatment. The solid-liquid ratio of bamboo strips to the solution is 1:2.5~4.

5. The softening temperature is 105~165℃ and the softening time is 0.5~6.0h to obtain softened bamboo strips. (2) Mechanical extrusion: The softened bamboo strips are extruded and torn, and then extruded and broken into fibers to obtain broken bamboo material; (3) Impregnation treatment: Soak the shredded bamboo material in H2O2 solution for impregnation treatment. The amount of H2O2 used is 6%~12% of the mass of the shredded bamboo material. The pH during impregnation treatment is 10.5~12.5, the water content is 65%~75%, the reaction temperature is 45~65℃, and the reaction time is 30~60min. Then, grind, remove impurities and wash to obtain the final product.

2. The method according to claim 1, wherein: The extrusion in step (2) is performed using a screw extruder.

3. The method according to claim 2, wherein: The compression ratio of the extrusion is 3~4:

1.

4. A high-yield bamboo pulp obtained by the method according to any one of claims 1 to 3.