Kenaf whole stalk apmp pulp and its preparation method

Abstract

The application provides a whole-stalk kenaf APMP pulp and a preparation method thereof, and the specific steps comprise the following steps: S1, cutting the air-dried whole-stalk kenaf into strips, washing and removing impurities to obtain material a; S2, pre-steaming the material a, and extruding and defibrating the steamed material to obtain material b; S3, impregnating the material b in a pre-impregnation liquid to form pulp, and centrifugally dewatering the pulp to a concentration of 20-30 wt% to obtain pulp a; S4, grinding the pulp a to form high-concentration ground pulp, adding the high-concentration ground pulp into an adjusting liquid a to bleach, and centrifugally dewatering the high-concentration ground pulp to a concentration of 20-30 wt% to obtain pulp b; S5, adding the pulp b into an adjusting liquid b to perform two-stage bleaching, centrifugally dewatering the pulp b to a concentration of 20-30 wt% to form pulp c, diluting the pulp c, grinding the pulp c, washing and screening after the grinding is completed, and obtaining the whole-stalk kenaf APMP pulp. The whole-stalk kenaf APMP pulp has good pulp properties, breaks the dependence of traditional APMP pulping on wood, and alleviates the shortage of domestic pulping wood resources.

Description

Technical Field

[0001] The invention relates to the technical field of pulping and papermaking, and in particular to kenaf whole-stalk APMP pulp and a preparation method thereof. Background Art

[0002] The APMP pulping process is alkaline hydrogen peroxide mechanical pulping, which can complete the pulping and bleaching processes simultaneously. Its main pulping mechanism is the combined action of NaOH and H2O2. NaOH, as an alkaline solvent, helps to destroy the lignin-cellulose bond of plant fibers and promote the loosening of fibers; while H2O2, as a bleaching agent, can improve the whiteness of the pulp while removing lignin. Therefore, the prepared pulp has the advantages of high yield, high whiteness and high strength, and the wastewater pollution control during the production process is relatively easy.

[0003] As the country continues to strengthen forest resource protection and people's environmental awareness continues to improve, in view of the current situation that most domestic APMP pulping companies use wood as raw material, finding new APMP pulping raw materials and improving the current situation of scarce wood resources have become important tasks for the pulp and paper industry.

[0004] Kenaf, as an annual fiber crop, has a short growth cycle and strong adaptability. It can grow well in poor, saline, and arid soil environments and has a high biomass yield. In addition, kenaf has low soil requirements and can be planted on a small land area on a large scale. The water resource consumption and land occupation during the planting process are also relatively small. Therefore, kenaf can not only effectively replace some wood raw materials, but also has strong biodegradability and a relatively low burden on the environment. Compared with wood, kenaf has a higher cellulose content and better mechanical strength and tensile properties, making it very suitable for pulping, especially in the APMP pulping process, which can provide a more stable and efficient fiber separation effect. Compared with other traditional wood raw materials, the pulping process of kenaf is relatively simple and has higher economic benefits and environmental advantages, which can meet the increasingly stringent environmental protection requirements of the modern pulp and paper industry.

[0005] However, current pulping processes still face challenges with pulp quality and performance, particularly in terms of tensile strength and cohesive strength, where performance often varies. Kenaf fibers are relatively fragile, have a high lignin content, and vary in fiber length. These factors impact the pulp's mechanical strength, fiber dispersion, and ultimately, the properties of the paper. Therefore, improving the tensile and cohesive strength of kenaf APMP pulp, and enhancing its consistency and controllability, remains a pressing technical challenge in the current APMP pulping process. Summary of the Invention

[0006] In view of this, the present invention proposes a kenaf whole-stalk APMP pulp and a preparation method thereof to solve the above-mentioned technical problems. The prepared pulp has excellent tensile index and cohesive strength. The present invention can not only alleviate the pressure on wood resources, but also promote the diversified utilization of resources, has high economic benefits and environmental advantages, and is of practical significance.

[0007] The technical solution of the present invention is achieved as follows:

[0008] A method for preparing kenaf whole-stalk APMP pulp, comprising the following steps:

[0009] S1. Raw material preparation: Cut air-dried kenaf stalks into strips, wash and remove impurities to obtain material a;

[0010] S2, pre-steaming and screw extrusion decompression machine extrusion: pre-steaming material a, extruding the steamed material to obtain material b;

[0011] S3, pre-impregnation: adding material b to the pre-impregnation liquid and ultrasonically treating it to form a slurry, washing the slurry, and centrifuging and dehydrating it to a concentration of 20-30 wt% to obtain slurry a;

[0012] S4, one-stage high-consistency refining and bleaching: refining pulp a to form a high-consistency ground pulp, adding the high-consistency ground pulp to the conditioning solution a for bleaching, and centrifugally dehydrating to a concentration of 20-30 wt% to obtain pulp b;

[0013] S5. Secondary bleaching and low-concentration refining: Slurry b is added to regulating liquid b for secondary bleaching, and centrifugally dehydrated to a concentration of 20-30 wt% to form slurry c. Slurry c is diluted and refining is performed, and after refining, it is washed and screened to obtain the target kenaf whole-stalk APMP pulp.

[0014] Furthermore, in step S1, the moisture content of the air-dried kenaf stalks is 8%-15%; the strips have a length of 3-6 cm, a width of 0.3-0.8 cm, and a thickness of 0.3-0.8 cm.

[0015] Furthermore, in step S2, the pre-steaming treatment is performed at 90-100° C. for 40-60 min.

[0016] Furthermore, in step S3, the concentration of the pre-impregnation liquid is 10-15wt%, and the pre-impregnation liquid consists of 1.0-3.0kg / adt of DTPA, 1.0-3.0kg / adt of MgSO4, 10-30kg / adt of NaOH, 10-20kg / adt of H2O2, and 10-15kg / adt of ionic liquid; and the ultrasonic treatment is carried out at 20-40kHz and 90-100°C for 40-60min.

[0017] Furthermore, in step S4, the spacing between the grinding discs is 0.8-1.0 mm, and the concentration is 20-30 wt%.

[0018] Furthermore, in step S4, the concentration of the regulating solution a is 10-15 wt %, and the regulating solution a is composed of 1.0-3.0 kg / adt of DTPA, 1.0-3.0 kg / adt of MgSO4, 10-30 kg / adt of NaOH, and 30-60 kg / adt of H2O2; and the bleaching is performed at 90-100°C for 40-60 min.

[0019] Furthermore, in step S5, the concentration of the regulating solution b is 10-15 wt %, and the regulating solution b consists of 1.0-3.0 kg / adt of DTPA, 1.0-3.0 kg / adt of MgSO 4 , 10-30 kg / adt of NaOH, and 60-100 kg / adt of H 2 O 2 .

[0020] Furthermore, in step S5, the second stage bleaching is performed at 90-100°C for 40-60 minutes; and the pulp c is diluted to 15-20 wt%.

[0021] Furthermore, in step S5, the spacing between the refining discs is 0.6-0.8 mm.

[0022] A kenaf whole-stalk APMP pulp is prepared by the above-mentioned preparation method.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The kenaf whole stalk APMP pulping process of the present invention uses kenaf whole stalks as raw materials, breaks the dependence of traditional APMP pulping on wood, and alleviates the current situation of scarcity of pulping wood resources in China.

[0025] 2. The pre-impregnation liquid of the specific composition of the present invention effectively removes lignin from the whole kenaf stalks and significantly improves the quality of the pulp. The ionic liquid in the pre-impregnation liquid gently softens the whole kenaf stalks, which is beneficial to improving the dispersion of the fibers, reducing aggregation, promoting the efficiency of subsequent refining, reducing the wear on the refining equipment, and improving the pulping efficiency.

[0026] 3. The one-stage high-concentration refining and bleaching of the present invention combines pulping and bleaching into one, completing the bleaching process while pulping. It is simple to operate and has low energy consumption. It not only effectively improves the fiber dispersion of the pulp, but also optimizes the bleaching effect of the pulp. The subsequent two-stage bleaching and low-concentration refining ensure the whiteness of the pulp and make the pulp more evenly dispersed without damaging the fibers.

[0027] 4. The examples show that the APMP pulping process for whole kenaf stalks of the present invention is simple to operate and has low energy consumption. The obtained pulp has obvious advantages in tensile index and cohesive strength compared with APMP pulp prepared from wood, and has better pulp properties. DETAILED DESCRIPTION

[0028] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0029] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0030] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0031] The ionic liquid of the present invention is an imidazolidinyl-based ionic liquid.

[0032] Example 1

[0033] The preparation method of kenaf whole stalk APMP pulp of this embodiment comprises the following specific steps:

[0034] S1. Raw material preparation: Cut air-dried kenaf stalks with a moisture content of 8%-15% into strips with specific specifications of 3-6 cm in length, 0.3-0.8 cm in width, and 0.3-0.8 cm in thickness, and wash with water to remove impurities such as sand and gravel to obtain material a;

[0035] S2, pre-steaming and screw extrusion deflaking machine extrusion: material a is pre-steamed at 95 ° C for 50 minutes, and the pre-steamed material is extruded and deflaked by MSD to obtain material b;

[0036] S3. Pre-impregnation: Material b was added to a 12 wt% pre-impregnation solution consisting of 1.5 kg / adt DTPA, 1.5 kg / adt MgSO4, 10 kg / adt NaOH, 20 kg / adt H2O2, and 12 kg / adt ionic liquid. The solution was ultrasonically treated at 30 kHz and 96°C for 45 min to form a slurry. The slurry was washed and centrifuged to obtain a slurry a.

[0037] S4. One-stage high-consistency refining and bleaching: Slurry a was refined using a disc refiner with a disc spacing of 0.9 mm and a refining concentration of 23 wt%. After forming a high-consistency ground slurry, a 12 wt% conditioning solution a was added. The conditioning solution a consisted of 2.0 kg / adt of DTPA, 2.0 kg / adt of MgSO₄, 15 kg / adt of NaOH, and 50 kg / adt of H₂O₂. The slurry was bleached at 96° C. for 50 min and centrifuged to dehydrate to a slurry concentration of 20 wt% to obtain slurry b.

[0038] S5. Secondary bleaching and low-concentration refining: Slurry b is added with a 12 wt% regulating liquid b, which consists of 3.0 kg / adt of DTPA, 3.0 kg / adt of MgSO4, 20 kg / adt of NaOH, and 70 kg / adt of H2O2. The pulp is bleached for 45 min at 96°C and then centrifuged and dehydrated to a pulp concentration of 20 wt% to form pulp c. The pulp c is diluted to 15 wt% and then refined with a disk spacing of 0.7 mm. After refining, the pulp is washed and screened to obtain kenaf whole-stalk APMP pulp.

[0039] Example 2

[0040] The preparation method of kenaf whole stalk APMP pulp of this embodiment comprises the following specific steps:

[0041] S1. Raw material preparation: Cut air-dried kenaf stalks with a moisture content of 8%-15% into strips with specific specifications of 3-6 cm in length, 0.3-0.8 cm in width, and 0.3-0.8 cm in thickness, and wash with water to remove impurities such as sand and gravel to obtain material a;

[0042] S2, pre-steaming and screw extrusion deflaking machine extrusion: material a is pre-steamed at 100 ° C for 40 minutes, and the pre-steamed material is extruded and deflaked by MSD to obtain material b;

[0043] S3. Pre-impregnation: Material b was added to a 15 wt% pre-impregnation solution consisting of 1.5 kg / adt DTPA, 1.5 kg / adt MgSO4, 10 kg / adt NaOH, 15 kg / adt H2O2, and 10 kg / adt ionic liquid. The solution was ultrasonically treated at 20 kHz and 98°C for 40 min to form a slurry. The slurry was washed and centrifuged to obtain a slurry a.

[0044] S4. One-stage high-consistency refining and bleaching: Slurry a was refined using a disc refiner with a disc spacing of 1.0 mm and a refining concentration of 25 wt%. After forming a high-consistency ground slurry, a 15 wt% conditioning solution a was added. The conditioning solution a consisted of 2.0 kg / adt of DTPA, 2.0 kg / adt of MgSO₄, 15 kg / adt of NaOH, and 45 kg / adt of H₂O₂. The slurry was bleached at 98° C. for 40 min and centrifuged to dehydrate to a slurry concentration of 25 wt% to obtain slurry b.

[0045] S5. Secondary bleaching and low-concentration refining: Slurry b is added with a 15 wt% regulating liquid b, which consists of 3.0 kg / adt of DTPA, 3.0 kg / adt of MgSO4, 20 kg / adt of NaOH, and 80 kg / adt of H2O2. The pulp is bleached for 40 min at 98°C and then centrifuged and dehydrated to a pulp concentration of 25 wt% to form pulp c. The pulp c is diluted to 17 wt% and then refined with a disk spacing of 0.8 mm. After refining, the pulp is washed and screened to obtain kenaf whole-stalk APMP pulp.

[0046] Example 3

[0047] The preparation method of kenaf whole stalk APMP pulp of this embodiment comprises the following specific steps:

[0048] S1. Raw material preparation: Cut air-dried kenaf stalks with a moisture content of 8%-15% into strips with specific specifications of 3-6 cm in length, 0.3-0.8 cm in width, and 0.3-0.8 cm in thickness, and wash with water to remove impurities such as sand and gravel to obtain material a;

[0049] S2, pre-steaming and screw extrusion deflaking machine extrusion: Material a is pre-steamed at 90 ° C for 60 minutes, and the pre-steamed material is extruded and deflaked by MSD to obtain material b;

[0050] S3. Pre-impregnation: Material b was added to a 10 wt% pre-impregnation solution consisting of 1.5 kg / adt DTPA, 1.5 kg / adt MgSO4, 10 kg / adt NaOH, 10 kg / adt H2O2, and 15 kg / adt ionic liquid. The solution was ultrasonically treated at 40 kHz and 90°C for 60 min to form a slurry. The slurry was washed and centrifuged to obtain a slurry a.

[0051] S4. One-stage high-consistency refining and bleaching: Slurry a was refined using a disc refiner with a disc spacing of 0.8 mm and a refining concentration of 30 wt%. After forming a high-consistency ground slurry, a 10 wt% conditioning solution a was added. The conditioning solution a consisted of 2.0 kg / adt of DTPA, 2.0 kg / adt of MgSO₄, 15 kg / adt of NaOH, and 30 kg / adt of H₂O₂. The slurry was bleached at 90° C. for 60 min and centrifuged to dehydrate to a slurry concentration of 30 wt% to obtain slurry b.

[0052] S5. Secondary bleaching and low-concentration refining: Slurry b is added with a 10 wt% regulating liquid b, which consists of 3.0 kg / adt of DTPA, 3.0 kg / adt of MgSO4, 20 kg / adt of NaOH, and 60 kg / adt of H2O2. The pulp is bleached for 60 min at 90°C and then centrifuged and dehydrated to a pulp concentration of 30 wt% to form pulp c. The pulp c is diluted to 20 wt% and then refined with a disk spacing of 0.6 mm. After refining, the pulp is washed and screened to obtain kenaf whole-stalk APMP pulp.

[0053] Comparative Example 1

[0054] The difference from Example 1 is that eucalyptus wood is used as raw material and the APMP pulping process of the present invention is adopted. Other aspects are the same as Example 1.

[0055] Comparative Example 2

[0056] The difference from Example 1 is that acacia wood is used as raw material and the APMP pulping process of the present invention is adopted. Other aspects are the same as Example 1.

[0057] Comparative Example 3

[0058] The pulping was carried out using the method described in patent "CN 1234936C".

[0059] Comparative Example 4

[0060] The pulping was carried out using the method described in patent "CN 1350091A".

[0061] Comparative Example 5

[0062] The difference from Example 1 is that the pre-impregnation liquid lacks ionic liquid, and the rest is the same as Example 1.

[0063] Test example

[0064] The slurries prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to quality characteristics, and the indicators and results are shown in Table 1.

[0065] Table 1

[0066]

[0067] As shown in Table 1, the pulps prepared by the APMP pulping process for whole kenaf stalks in Examples 1-3 of the present invention exhibit excellent pulp properties, with tensile index and cohesive strength significantly superior to those of the wood raw materials used in conventional Comparative Examples 1-2. This indicates that whole kenaf stalks are superior to wood raw materials for APMP pulping. They also outperform the pulps obtained by the pulping processes of Comparative Examples 3 and 4. The pulping process in Comparative Example 3 utilizes chemical thermomechanical pulping, while the APMP pulping process used in the present invention combines pre-steaming and chemical impregnation at atmospheric pressure, combining pulping and bleaching. The bleaching process is simple to operate and energy-efficient, resulting in pulps with excellent pulp properties. The quality characteristics of the APMP pulp obtained by the preparation steps of Comparative Example 4 are significantly different from those of the present invention. The pre-impregnation solution in Comparative Example 5 lacks an ionic liquid, resulting in reduced pulp performance.

[0068] 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 in the scope of protection of the present invention.

Claims

1. A method for preparing kenaf whole stalk APMP pulp, characterized in that: The specific steps include: S1. Raw material preparation: Cut air-dried kenaf stalks into strips, wash and remove impurities to obtain material a; S2, pre-steaming and screw extrusion decompression machine extrusion: pre-steaming material a, extruding the steamed material to obtain material b; S3, pre-impregnation: adding material b to the pre-impregnation liquid and ultrasonically treating it to form a slurry, washing the slurry, and centrifuging and dehydrating it to a concentration of 20-30wt% to obtain slurry a; The concentration of the pre-dip solution is 10-15 wt %, and the pre-dip solution consists of 1.0-3.0 kg / adt of DTPA, 1.0-3.0 kg / adt of MgSO4, 10-30 kg / adt of NaOH, 10-20 kg / adt of H2O2, and 10-15 kg / adt of ionic liquid; the ultrasonic treatment is performed at 20-40 kHz and 90-100° C. for 40-60 min; S4, one-stage high-consistency refining and bleaching: refining pulp a to form a high-consistency ground pulp, adding the high-consistency ground pulp to the conditioning solution a for bleaching, and centrifugally dehydrating to a concentration of 20-30wt% to obtain pulp b; The concentration of the conditioning solution a is 10-15 wt %, and the conditioning solution a is composed of 1.0-3.0 kg / adt of DTPA, 1.0-3.0 kg / adt of MgSO4, 10-30 kg / adt of NaOH, and 30-60 kg / adt of H2O2; the bleaching is performed at 90-100° C. for 40-60 min; S5. Secondary bleaching and low-concentration refining: adding slurry b to conditioning solution b for secondary bleaching, centrifugally dehydrating to a concentration of 20-30 wt% to form slurry c, diluting slurry c, and refining, followed by washing and screening to obtain the target kenaf whole-stalk APMP pulp; The concentration of the regulating liquid b is 10-15 wt %, and the regulating liquid b is composed of 1.0-3.0 kg / adt of DTPA, 1.0-3.0 kg / adt of MgSO4, 10-30 kg / adt of NaOH, and 60-100 kg / adt of H2O2; The second stage bleaching is carried out at 90-100° C. for 40-60 min; the pulp c is diluted to 15-20 wt %.

2. The method for preparing APMP pulp of whole kenaf stalks according to claim 1, wherein: In step S1, the moisture content of the air-dried kenaf stalks is 8%-15%; the strips have a length of 3-6 cm, a width of 0.3-0.8 cm, and a thickness of 0.3-0.8 cm.

3. The method for preparing APMP pulp of whole kenaf stalks according to claim 1, wherein: In step S2, the pre-steaming treatment is carried out at 90-100°C for 40-60 minutes.

4. The method for preparing APMP pulp of whole kenaf stalks according to claim 1, wherein: In step S4, the spacing between the grinding discs is 0.8-1.0 mm, and the concentration is 20-30 wt%.

5. The method for preparing APMP pulp of whole kenaf stalks according to claim 1, wherein: In step S5, the spacing between the refining discs is 0.6-0.8 mm.

6. A kenaf whole-stalk APMP pulp prepared by the preparation method according to any one of claims 1 to 5.

Images