Method for preparing chemimechanical pulp by dipping gold arundo donax in hot alkali and method for constructing chemimechanical pulp model by dipping gold arundo donax in hot alkali

Abstract

The invention belongs to the technical field of pulping and papermaking, and particularly discloses a method for preparing chemimechanical pulp by dipping bamboo reed in hot alkali and a method for constructing a model of the chemimechanical pulp, and the method comprises the following steps: putting absolutely dry raw materials of the bamboo reed into a sealing bag, adding water, sealing, and carrying out high-pressure sterilization; the method comprises the following steps: carrying out extrusion defibering and hot alkali dipping on the gold arundo donax subjected to high-pressure sterilization, and then collecting a treatment solution, in the hot alkali dipping process, alkali in hot alkali liquor is NaOH, in terms of Na2O, the use amount of the alkali is 4-8%, the temperature is 90-100 DEG C, and the dipping time is 30-60 minutes; carrying out segmented pulp grinding on the residual solid; and washing the ground pulp, heating for latency elimination, screening to obtain fine pulp, and pulping to obtain the product. After appropriate hot alkali dipping, paper made of the golden reed chemimechanical pulp can be comparable with wheat straw chemimechanical pulp paper in physical performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of pulp and paper making, and particularly relates to a method for preparing chemimechanical pulp from Arundo donax by hot alkali impregnation and a method for constructing a model thereof. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] The paper-making industry is an important basic raw material industry in China, which is closely related to fields such as the national economy, cultural dissemination, industrial production, and national defense construction. However, there are significant imbalances in the current pulp raw material structure in China, and the dependence on imported wood pulp has been maintained at over 60% for a long time, severely restricting the independent and controllable development of the industry. Therefore, it is urgent to optimize the pulp raw material structure and develop new alternative raw materials to reduce the external dependence and ensure the safety and stability of the industrial chain.

[0004] In recent years, as a high-yield and widely adaptable plant resource, Arundo donax has been widely planted in the north and south of China, with an annual production capacity of up to 150 million plants. Research shows that Arundo donax has excellent fiber properties, and key indicators such as fiber content, length-width ratio, and wall cavity ratio are all superior to the standards of traditional pulp raw materials, having good pulp-making applicability. Promoting the application of Arundo donax in the paper-making industry helps to reduce the dependence on imported wood pulp and optimize the raw material supply structure.

[0005] However, due to the natural differences in the component composition, tissue structure, and compactness of different batches of Arundo donax, even with the same pulp-making process parameters, there may still be large fluctuations in the fiber properties of the resulting pulp. This uncertainty easily leads to an increase in energy consumption during the pulp-making process or unstable paper quality, affecting production efficiency and product consistency. Currently, the industry mainly relies on experience to adjust process parameters and lacks scientific and accurate prediction methods, making it difficult to achieve stable control of pulp fiber quality. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for preparing chemimechanical pulp from Arundo donax by hot alkali impregnation and a method for constructing a model thereof. The present invention realizes the accurate prediction of the xylose dissolution amount during the hot alkali impregnation treatment process, and this model can provide certain reference significance for the preparation of Arundo donax chemimechanical pulp.

[0007] To achieve the above purpose, the present invention is realized through the following technical solutions: In the first aspect, the present invention provides a method for preparing chemimechanical pulp from Arundo donax by hot alkali impregnation, including the following steps: Put the dry raw materials of Arundo donax into a sealed bag, add water, seal it, and perform high-pressure sterilization; After subjecting the autoclaved Arundo donax to extrusion and fibrillation, and hot alkali impregnation, the treatment liquor is collected. During hot alkali impregnation, the alkali in the hot alkali liquor is NaOH, and the dosage of active alkali during impregnation accounts for 4%-8% of the absolute dry raw material (calculated as Na2O), that is, the alkali dosage in the hot alkali impregnation stage is 4%-8%, the temperature is 90-100 °C, and the impregnation time is 30-60 min, so that the xylose content in the obtained treatment liquor is 1.1-1.5 g / L; The remaining solid is ground in stages; After washing the ground pulp, it is heated to eliminate potential, screened to obtain fine pulp, and then beaten to obtain the product.

[0008] After appropriate hot alkali impregnation, the paper made from Arundo donax chemimechanical pulp can be comparable to the physical properties of wheat straw chemimechanical pulp paper.

[0009] In some embodiments, during hot alkali impregnation, the alkali in the hot alkali liquor is NaOH, calculated as Na2O, the alkali dosage is 5%-8%, the temperature is 90-100 °C, and the impregnation time is 40-60 min, so that the xylose content in the obtained treatment liquor is 1.2-1.4 g / L.

[0010] Preferably, during hot alkali impregnation, the alkali in the hot alkali liquor is NaOH, calculated as Na2O, the alkali dosage is 5%-7%, the temperature is 90-95 °C, and the impregnation time is 40-60 min.

[0011] In some embodiments, the Arundo donax is subjected to sun drying, cutting and then autoclaving.

[0012] Preferably, the cut Arundo donax is in a strip structure with a width of 40-60 mm.

[0013] Preferably, autoclaving is to place the sealed bag containing the mixture of Arundo donax and water in an autoclave and treat it at 90-100 °C for 30-60 min.

[0014] In some embodiments, the liquor ratio during hot alkali impregnation is 1:3-5, preferably 1:4.

[0015] The liquor ratio refers to the ratio of the mass of the absolute dry raw material to the total volume of the liquid.

[0016] In some embodiments, the fixed compression ratio used during extrusion and fibrillation is 1:3-5, preferably 1:4.

[0017] The fixed compression ratio refers to the ratio of the volume of the first screw groove in the screw feeding section to the volume of the last screw groove in the homogenization section, and this ratio represents the degree of compression of the material during the whole process of passing through the screw.

[0018] In some embodiments, during segmented refining, the tooth spacing in the first segment is 0.4-0.7 mm, and the tooth spacing in the second segment is 0.1-0.3 mm.

[0019] In some embodiments, the delatching temperature is 55-70°C, and the delatching time is 30-50 minutes; preferably, the delatching temperature is 55-65°C, and the delatching time is 35-45 minutes.

[0020] In some embodiments, the freeness after beating is 40±2°SR.

[0021] In a second aspect, the present invention provides a method for constructing a model for preparing chemical mechanical pulp by hot alkali impregnation of golden arundo donax, comprising the following steps: Put the absolutely dry raw materials of golden reed bamboo into a sealed bag, add water, seal it, and sterilize it under high pressure; After the high-pressure sterilized golden reed bamboo is squeezed and fluffed, hot alkali is impregnated, and the treatment liquid is collected, wherein the hot alkali impregnation is performed under different alkali amounts and different treatment times; The xylose content in the treated solution was determined, and the relationship between the hot alkali soaking conditions and the xylose dissolution amount was analyzed using the least squares method to obtain a hot alkali soaking-xylose dissolution amount model. When the xylose content in the treated liquid reaches 1.2-1.4 g / L, the hot alkali impregnation conditions are determined according to the hot alkali impregnation-xylose dissolution model; The golden bamboo can be treated according to the determined hot alkali soaking conditions.

[0022] The present invention found that: in the hot alkali soaking of golden reed, there is a significant correlation between the amount of alkali used, the treatment time and the amount of xylose dissolved. The established equation has high accuracy and can be used to optimize the process parameters of the hot alkali soaking stage of golden reed.

[0023] When the xylose content in the treatment solution reaches 1.2-1.4 g / L, especially 1.25-1.35 g / L, and further about 1.3 g / L, the corresponding hot alkali impregnation conditions are optimal.

[0024] In some embodiments, the regression equation of the hot alkali maceration-xylose dissolution model is: , in, , ; Y is the theoretical xylose concentration in the treatment solution; X j The amount of alkali used in the hot alkali impregnation stage; X t This is the treatment time of the hot alkali impregnation stage.

[0025] In some embodiments, the method for detecting xylose content is: Adjust the pH value of the treatment solution to 3 - 4 with dilute sulfuric acid. After centrifugation, take the supernatant and mix it with sulfuric acid and water for digestion. The digestion temperature is 120 - 125 °C and the digestion time is 50 - 70 min; After the digestion is completed, dilute the digestion solution and determine the xylose content using an ion chromatograph.

[0026] In some embodiments, during the hot alkali impregnation process, the alkali in the hot alkali solution is NaOH. Calculated as Na₂O, the alkali dosage is 4% - 8%, the temperature is 90 - 100 °C, and the impregnation time is 30 - 60 min.

[0027] Preferably, during extrusion and defibration, the fixed compression ratio is 1:4.

[0028] The beneficial effects obtained from one or more of the above embodiments of the present invention are as follows: (1) The present invention has found through research that: after appropriate hot alkali impregnation, the physical properties of the paper made from Arundo donax L. chemi - mechanical pulp can be comparable to those of wheat straw chemi - mechanical pulp paper. The bulk of the paper made under the optimal conditions is 26.01 cm 3 / g, the ring crush index is 9.708 N·m / g, the tear index is 3.786 mN·m 2 / g, the tensile index is 23.190 N·m / g, and the breaking length is 2.366 km.

[0029] (2) The present invention has found through research that: during the hot alkali impregnation of Arundo donax L., there is a significant correlation among the alkali dosage, treatment time, and xylose dissolution amount. The established equation has high accuracy and can be used to optimize the process parameters in the hot alkali impregnation stage of Arundo donax L.

[0030] (3) Use Matlab software to fit the data obtained from the experiment. The R 2 of the model is 0.9861, the mean square error is 0.0017. Using the F - test method, it is known that the regression equation is highly significant at the 0.01 level, the fitting effect is excellent, and the prediction results are credible.

[0031] The preparation method of the present invention is simple, highly practical, and easy to promote. Detailed Embodiments

[0032] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0033] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention rather than limitations.

[0034] In the following examples, all reagents are commercially available products.

[0035] Example 1 1. Air-dry Arundo donax L. and cut it into strips about 50 mm long, and measure its moisture content. 2. Take 200 g of absolutely dry raw material and put it into a sealed bag. According to a liquor ratio of 1:5, add an appropriate amount of deionized water, put it into an autoclave, and treat it at 100 °C for 40 min. 3. Use a screw extruder for extrusion and defibration, fix the compression ratio at 1:4, and perform two-stage extrusion. 4. Perform hot alkali impregnation under the conditions of an alkali charge of 6%, a treatment time of 50 min, a treatment temperature of 95 °C, and a liquor ratio of 1:4. After the impregnation is completed, collect the treatment liquor. 5. Pulverize the Arundo donax L. in step 4. The tooth pitch of the first stage is 0.5 mm, and the tooth pitch of the second stage is 0.2 mm. After washing the defibrated pulp several times, let it rest at 60 °C for 40 min, then dehydrate the pulp to a dryness of 20% - 30%, and use a screen pulp machine to screen the coarse pulp to obtain fine pulp. After balancing the moisture content, measure the moisture content of the pulp.

[0036] 6. Take 30 g of absolutely dry fine pulp, add deionized water until the pulp concentration is 10%, and use a PFI refiner to treat the fine pulp to increase its beating degree to 40 ± 2 °SR.

[0037] 7. Use a sheet former to form the pulp in step 6 into a paper with a basis weight of 100 g / cm 3 ².

[0038] 8. Place the paper formed in step 7 in a thermo-hygrostat at a temperature of 23 ± 1 °C and a relative humidity of 50 ± 2% for 24 h. Then measure the bulk thickness, ring crush index, tear index, tensile index, and breaking length of the paper.

[0039] 9. Adjust the pH of the treatment liquor collected in step 4 to 3.5 with dilute sulfuric acid, take 1 mL of the supernatant after centrifugation and put it into a digestion tube, add 70 μL of 72% H₂SO₄ solution and 0.93 mL of pure water, put it into a digester, and acidify it at 121 °C for 60 min. After the acidification is completed, dilute the supernatant by an appropriate multiple, and use an ion chromatograph to measure the xylose content.

[0040] The fine pulp yield of the Arundo donax L. chemimechanical pulp obtained in this example is 64.27%, and the bulk thickness of the formed paper is 26.01 cm 3 / g, the ring crush index is 9.708 N·m / g, the tear index is 3.786 mN·m 2 / g, the tensile index is 23.190 N·m / g, and the breaking length is 2.366 km. The xylose content in the treatment liquid is 1.3390 g / L.

[0041] Example 2 1. Air-dry the Arundo donax var. sinensis and cut it into strips about 50 mm long. Measure its moisture content; 2. Take 200 g of absolutely dry raw materials and put them into a sealed bag. According to the liquor ratio of 1:5, add an appropriate amount of deionized water, put it into an autoclave, and treat it at 100 °C for 40 min; 3. Use a screw extruder for extrusion and defibration, fix the compression ratio at 1:4, and perform two-stage extrusion; 4. Perform hot alkali impregnation under the conditions of an alkali charge of 6%, a treatment time of 60 min, a treatment temperature of 95 °C, and a liquor ratio of 1:4. After the impregnation is completed, collect the treatment liquid; 5. Pulp the Arundo donax var. sinensis in step 4. The tooth pitch of the first stage is 0.5 mm, and the tooth pitch of the second stage is 0.2 mm. After washing the defibrated pulp several times, defoam it at 60 °C for 40 min, then dehydrate the pulp to a dryness of 20% - 30%, and use a screen pulp machine to screen the coarse pulp to obtain fine pulp. After balancing the moisture, measure the moisture content of the pulp.

[0042] 6. Take 30 g of absolutely dry fine pulp, add deionized water until the pulp concentration is 10%, and use a PFI refiner to treat the fine pulp to increase the beating degree to 40 ± 2 °SR.

[0043] 7. Use a sheet former to form the pulp in step 6 into a paper with a basis weight of 100 g / cm 3 of paper.

[0044] 8. Place the paper formed in step 7 in a thermo-hygrostat at a temperature of 23 ± 1 °C and a relative humidity of 50 ± 2% for 24 h. Then detect the bulk density, ring crush index, tear index, tensile index, and breaking length of the paper.

[0045] 9. Adjust the pH of the treatment liquid collected in step 4 to 3.5 with dilute sulfuric acid, take 1 mL of the supernatant after centrifugation and put it into a digestion tube, add 70 μL of 72% H2S04 solution and 0.93 mL of pure water, put it into a digester, and acidify it at 121 °C for 60 min. After the acidification is completed, dilute the supernatant by an appropriate multiple, and use an ion chromatograph to measure the xylose content.

[0046] The fine pulp yield of the Arundo donax var. sinensis chemimechanical pulp obtained in this example is 65.03%, and the bulk density of the formed paper is 22.12 cm 3 / g, the ring crush index is 9.805 N·m / g, and the tear index is 3.983 mN·m 2 / g, the tensile index is 24.358 N·m / g, and the breaking length is 2.468 km. The xylose content in the treatment liquid is 1.4048 g / L.

[0047] Example 3 Compared with Example 1, the difference in this example is that in step 4, the hot alkali impregnation uses an alkali dosage of 7% and a treatment time of 40 min.

[0048] The fine pulp yield of the Arundo donax L. chemimechanical pulp obtained in this example is 63.85%, and the bulk of the formed paper is 22.89 cm 3 / g, the ring crush index is 10.002 N·m / g, and the tear index is 4.006 mN·m 2 / g, the tensile index is 30.927 N·m / g, and the breaking length is 3.156 km. The xylose content in the treatment liquid is 1.3253 g / L.

[0049] Comparative Example 1 Compared with Example 1, the difference in this comparative example is that in step 4, the hot alkali impregnation uses an alkali dosage of 4%, a treatment time of 35 min, and a treatment temperature of 85 °C.

[0050] The fine pulp yield of the Arundo donax L. chemimechanical pulp obtained in this comparative example is 70.02%, and the bulk of the formed paper is 33.491 cm 3 / g, the ring crush index is 3.3724 N·m / g, and the tear index is 0.447 mN·m 2 / g, the tensile index is 4.945 N·m / g, and the breaking length is 0.5046 km. The xylose content in the treatment liquid is 0.5532 g / L.

[0051] Comparative Example 2 Compared with Example 1, the difference in this comparative example is that in step 4, the hot alkali impregnation uses an alkali dosage of 6%, a treatment time of 35 min, and a treatment temperature of 85 °C.

[0052] The fine pulp yield of the Arundo donax L. chemimechanical pulp obtained in this comparative example is 69.30%, and the bulk of the formed paper is 31.011 cm 3 / g, the ring crush index is 5.835 N·m / g, and the tear index is 1.002 mN·m 2 / g, the tensile index is 10.372 N·m / g, and the breaking length is 1.058 km. The xylose content in the treatment liquid is 0.9491 g / L.

[0053] Comparative Example 3 Compared with Example 1, the difference in this comparative example is that in step 4, the hot alkali impregnation uses an alkali dosage of 6%, a treatment time of 50 min, and a treatment temperature of 85 °C.

[0054] The fine pulp yield of the Arundo donax L. chemical mechanical pulp obtained in this comparative example was 63.93%, the bulk of the formed paper was 25.05 cm 3 / g, the ring crush index was 8.038 N·m / g, the tear index was 3.107 mN·m 2 / g, the tensile index was 20.312 N·m / g, and the breaking length was 2.073 km. The xylose content in the treatment liquid was 1.1462 g / L.

[0055] Example 4 Model construction example: 1. Conduct 20 groups of experiments under different hot alkali impregnation conditions, and measure the xylose content in the treatment liquid. The specific experiments are shown in Table 1. The k-th sampling condition is recorded as: the alkali dosage X jk , the treatment time X tk , and the corresponding xylose dissolution amount is y k ; 2. Assume the regression equation is: ; Among them, , , a 1, a 2, a 3, a 4, a 5, b is the undetermined coefficient, then the error equation is: , Among them, k = 1, 2, 3,..., n; According to the least squares principle, it is necessary to satisfy the minimum error between the experimental data and the theoretical value, that is, to make the formula minimum. Use Matlab software to calculate the above equation, and finally obtain: ; Among them, , ; Y is the theoretical xylose concentration in the treatment liquid; X j is the alkali dosage in the hot alkali impregnation stage; X t is the treatment time in the hot alkali impregnation stage.

[0056] 3. According to the standard deviation estimator of the measurement data is very small, and the error between the actual value and the measurement value is small. The R of the equation 2The correlation coefficient is 0.9861 and the mean square error is 0.0017, indicating that the equation has a high accuracy. It shows that: the regression equation of the present invention can be used to predict the xylose dissolution amount corresponding to different treatment conditions in the hot alkali impregnation stage of Arundo donax L., so as to guide the subsequent pulping process; it is known by the F-test method that the regression is highly significant at the 0.01 level, indicating that it is feasible to study the law of xylose dissolution amount of Arundo donax L. in the hot alkali impregnation stage by the least squares method.

[0057] Table 1 Xylose dissolution amount under different treatment conditions

[0058] When the xylose content in the treatment liquid reaches about 1.3 g / L, the prepared paper has excellent physical properties. According to the hot alkali impregnation - xylose dissolution amount model, the process parameters of different alkali dosages and treatment times in the hot alkali impregnation stage can be obtained when the xylose content in the treatment liquid meets the standard, providing theoretical guidance for actual production.

[0059] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing chemi-mechanical pulp by hot alkali impregnation of Arundo donax, characterized in that: It includes the following steps: Put the absolute dry raw materials of Arundo donax into a sealed bag, add water, seal it, and carry out high-pressure sterilization; After squeezing and defibrating the Arundo donax subjected to high-pressure sterilization and hot alkali impregnation, collect the treatment liquid. During hot alkali impregnation, the alkali in the hot alkali liquid is NaOH, calculated as Na2O, the alkali dosage is 4%-8%, the temperature is 90-100 °C, and the impregnation time is 30-60 min, so that the xylose content in the obtained treatment liquid is 1.1-1.5 g / L; Carry out segmented pulping on the remaining solid; After washing the ground pulp, heat it to eliminate slime, screen it to obtain fine pulp, and after beating, it is obtained.

2. The method for preparing chemical mechanical pulp by hot alkali impregnation of Arundo donax as claimed in claim 1, wherein: The Arundo donax is subjected to high-pressure sterilization after being dried in the sun and cut; Preferably, the cut Arundo donax is in a strip structure with a width of 40-60 mm; Preferably, for high-pressure sterilization, put the sealed bag containing the mixture of Arundo donax and water into an autoclave, and treat it at 90-100 °C for 30-60 min.

3. The method for preparing a chemi-mechanical pulp by hot alkali impregnation of Arundo donax as claimed in claim 1, wherein: The liquor ratio during hot alkali impregnation is 1:3-5, preferably 1:4; Preferably, during hot alkali impregnation, the alkali in the hot alkali liquid is NaOH, calculated as Na2O, the alkali dosage is 5%-8%, the temperature is 90-100 °C, and the impregnation time is 40-60 min, so that the xylose content in the obtained treatment liquid is 1.2-1.4 g / L; Preferably, during hot alkali impregnation, the alkali in the hot alkali liquid is NaOH, calculated as Na2O, the alkali dosage is 5%-7%, the temperature is 90-95 °C, and the impregnation time is 40-60 min.

4. The method for preparing chemical mechanical pulp by hot alkali impregnation of Arundo donax as claimed in claim 1, wherein: The fixed compression ratio used during extrusion and defibration is 1:3-5, preferably 1:4; Preferably, during segmented pulping, the tooth pitch of the first stage is 0.4-0.7 mm, and the tooth pitch of the second stage is 0.1-0.3 mm.

5. The method for preparing chemical mechanical pulp by hot alkali impregnation of Arundo donax as claimed in claim 1, wherein: The temperature for eliminating slime is 55-70 °C, and the time for eliminating slime is 30-50 min; preferably, the temperature for eliminating slime is 55-65 °C, and the time for eliminating slime is 35-45 min.

6. The method for preparing a chemimechanical pulp by hot alkali impregnation of Arundo donax as claimed in claim 1, wherein: The beating degree after beating is 40±2 °SR.

7. A method for constructing a model for preparing chemimechanical pulp by hot alkali impregnation of Arundo donax L., characterized in that: It includes the following steps: Put the absolute dry raw materials of Arundo donax into a sealed bag, add water, seal it, and carry out high-pressure sterilization; After squeezing and defibrating the Arundo donax subjected to high-pressure sterilization and hot alkali impregnation, collect the treatment liquid. The hot alkali impregnation is carried out under different alkali dosages and different treatment times; Measure the xylose content in the treatment liquid, analyze the relationship between the hot alkali impregnation conditions and the xylose dissolution amount by the least squares method, and obtain a hot alkali impregnation-xylose dissolution amount model; When the xylose content in the treatment liquid reaches 1.2-1.4 g / L, determine the hot alkali impregnation conditions according to the hot alkali impregnation-xylose dissolution amount model; Treat the Arundo donax according to the determined hot alkali impregnation conditions, and that's it.

8. The model construction method for preparing chemical mechanical pulp by hot alkali impregnation of Arundo donax as claimed in claim 7, characterized in that: The regression equation of the hot alkali impregnation-xylose dissolution model is: ， Among them, , ; Y is the theoretical xylose concentration in the treatment liquid; X j is the alkali dosage in the hot alkali impregnation stage; X t is the treatment time in the hot alkali impregnation stage; Preferably, when Y is 1.25-1.35 g / L, it corresponds to the optimal hot alkali impregnation conditions.

9. The method for constructing a model for preparing a chemi-mechanical pulp by hot alkali impregnation of Arundo donax as claimed in claim 7, wherein: The detection method for the xylose content is: Adjust the pH value of the treatment liquid to 3-4 with dilute sulfuric acid, after centrifugation, take the supernatant and mix it with sulfuric acid and water, carry out digestion, the digestion temperature is 120-125 °C, and the digestion time is 50-70 min; After digestion is completed, the digestion solution is diluted, and the xylose content is determined by an ion chromatograph.

10. The method for constructing a model for preparing chemi-mechanical pulp by hot alkali impregnation of Arundo donax as claimed in claim 7, wherein: During the hot alkali impregnation process, the alkali in the hot alkali solution is NaOH, calculated as Na2O, the alkali dosage is 4% - 8%, the temperature is 90 - 100 °C, and the impregnation time is 30 - 60 min; Preferably, during extrusion and defibration, the fixed compression ratio is 1:4.

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