Kenaf whole stalk APMP (alkaline peroxide mechanical pulp) and preparation method thereof

Abstract

The invention provides kenaf whole stalk APMP pulp and a preparation method thereof.The preparation method comprises the specific steps that S1, air-dried kenaf whole stalks are cut into strips, washing and impurity removing are conducted, and a material a is obtained; s2, carrying out pre-steaming treatment on the material a, and extruding and defibering the steamed material to obtain a material b; s3, adding the material b into the pre-impregnation liquid for impregnation to form slurry, and performing centrifugal dewatering on the slurry until the concentration is 20-30wt% to obtain slurry a; s4, grinding the pulp a to form high-concentration ground pulp, adding the high-concentration ground pulp into the adjusting liquid a, bleaching, and centrifugally dewatering until the concentration is 20-30wt% to obtain pulp b; s5, the pulp b is added into the adjusting liquid b for second-stage bleaching and centrifugal dewatering till the concentration is 20-30 wt%, pulp c is formed, the pulp c is diluted and ground, cleaning and screening are conducted after grinding is completed, and the kenaf whole stalk APMP pulp is obtained. The kenaf whole stalk APMP pulp has good pulp characteristics, the dependence of traditional APMP pulping on wood is broken through, and the current situation that domestic pulping wood resources are deficient is relieved.

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 at the same time. Its main pulping mechanism is the joint action of NaOH and H2O2. NaOH, as an alkaline solvent, helps to destroy the lignin-cellulose bonds 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 in 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 has become an important task for the pulp and paper industry.

[0004] As an annual fiber crop, kenaf has a short growth cycle and strong adaptability. It can grow well in poor, saline and arid soil environments and has a high biological 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 part of the wood raw materials, but also has strong biodegradability and relatively low burden on the environment. Compared with wood, kenaf has a higher cellulose content and better mechanical strength and tensile properties, which is very suitable for pulping, especially in the APMP pulping process, it 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, in the actual production of the current pulping process, there are still problems with the quality and performance of the pulp, especially in terms of tensile index and cohesive strength, the performance of the pulp is often uneven. Kenaf fibers are relatively fragile, have a high lignin content, and the fibers are of different lengths. These factors will affect the mechanical strength, fiber dispersion, and final paper performance of the pulp. Therefore, how to improve the tensile strength and cohesive strength of kenaf APMP pulp and improve the consistency and controllability of the pulp is still a technical problem that needs to be solved 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 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 has practical significance.

[0007] The technical solution of the present invention is achieved in this way:

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

[0009] S1. Raw material preparation: cutting air-dried kenaf stalks into strips, washing and removing impurities to obtain material a;

[0010] S2, pre-steaming and screw extrusion decompression machine extrusion: pre-steaming material a, extruding and decompressing 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 centrifugally dehydrating it to a concentration of 20-30wt% to obtain slurry a;

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

[0013] S5. Second-stage bleaching and low-concentration refining: add pulp b into regulating liquid b for second-stage bleaching, centrifuge and dehydrate to a concentration of 20-30wt%, form pulp c, dilute pulp c, and perform refining. After refining, wash and screen to obtain the target kenaf whole-stalk APMP pulp.

[0014] Furthermore, in step S1, the water content of the air-dried whole 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 carried out 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 10-15wt%, and the regulating solution a is composed of 1.0-3.0kg / adt of DTPA, 1.0-3.0kg / adt of MgSO4, 10-30kg / adt of NaOH, and 30-60kg / adt of H2O2; and the bleaching is performed at 90-100°C for 40-60min.

[0019] Furthermore, in step S5, the concentration of the regulating solution b is 10-15wt%, and the regulating solution b consists of 1.0-3.0kg / adt of DTPA, 1.0-3.0kg / adt of MgSO4, 10-30kg / adt of NaOH, and 60-100kg / adt of H2O2.

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

[0021] Furthermore, in step S5, the spacing between the grinding 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 stalk as raw material, breaks the dependence of traditional APMP pulping on wood, and alleviates the current situation of shortage of domestic pulping wood resources.

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

[0026] 3. The one-stage high-concentration pulping 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 pulping ensure the whiteness of the pulp and make the pulp more evenly dispersed without damaging the fibers.

[0027] 4. The examples show that the kenaf whole stalk APMP pulping process 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 embodiments are provided below to further illustrate the present invention.

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

[0030] Unless otherwise specified, the materials, reagents, etc. used in the embodiments 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 method for preparing the whole kenaf 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 decomposition machine extrusion: material a is pre-steamed at 95°C for 50 minutes, and the pre-steamed material is extruded and decomposed by MSD to obtain material b;

[0036] S3, pre-impregnation: add material b to a pre-impregnation solution with a concentration of 12wt%, the pre-impregnation solution consists of 1.5kg / adt DTPA, 1.5kg / adt MgSO4, 10kg / adt NaOH, 20kg / adt H2O2, and 12kg / adt ionic liquid, and perform ultrasonic treatment at 30kHz and 96°C for 45min to form a slurry, wash the slurry, and centrifuge and dehydrate it to a concentration of 25wt% to obtain slurry a;

[0037] S4, one-stage high-concentration refining and bleaching: the pulp a is refined by a disc mill, the disc spacing is set to 0.9 mm, the refining concentration is controlled at 23wt%, and after the high-concentration refining pulp is formed, a 12wt% regulating liquid a is added, the regulating liquid a is composed of 2.0kg / adt of DTPA, 2.0kg / adt of MgSO4, 15kg / adt of NaOH, and 50kg / adt of H2O2, bleached at 96°C for 50min, and centrifuged to dehydrate to a pulp concentration of 20wt%, to obtain pulp b;

[0038] S5. Second-stage bleaching and low-concentration refining: add 12wt% regulating liquid b to pulp b, which consists of 3.0kg / adt DTPA, 3.0kg / adt MgSO4, 20kg / adt NaOH and 70kg / adt H2O2, and carry out second-stage bleaching at 96°C for 45min. After the bleaching, centrifuge and dehydrate the pulp to a pulp concentration of 20wt% to form pulp c. Dilute pulp c to 15wt%, and then refine the pulp with a disk spacing of 0.7mm. After the bleaching, wash and screen to obtain kenaf whole-stalk APMP pulp.

[0039] Example 2

[0040] The method for preparing the whole kenaf 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 decomposition machine extrusion: material a is pre-steamed at 100°C for 40 minutes, and the pre-steamed material is extruded and decomposed by MSD to obtain material b;

[0043] S3, pre-impregnation: add material b to a pre-impregnation solution with a concentration of 15wt%, the pre-impregnation solution consists of 1.5kg / adt DTPA, 1.5kg / adt MgSO4, 10kg / adt NaOH, 15kg / adt H2O2, and 10kg / adt ionic liquid, and perform ultrasonic treatment at 20kHz and 98°C for 40min to form a slurry, wash the slurry, and centrifuge and dehydrate it to a concentration of 25wt% to obtain slurry a;

[0044] S4, one-stage high-concentration refining and bleaching: the pulp a is refined by a disc mill, the disc spacing is set to 1.0 mm, the refining concentration is controlled at 25wt%, and after the high-concentration refining pulp is formed, a 15wt% concentration regulating liquid a is added, the regulating liquid a is composed of 2.0kg / adt of DTPA, 2.0kg / adt of MgSO4, 15kg / adt of NaOH, and 45kg / adt of H2O2, bleached at 98°C for 40min, and centrifuged to dehydrate to a pulp concentration of 25wt%, to obtain pulp b;

[0045] S5. Second-stage bleaching and low-concentration refining: add 15wt% regulating liquid b to pulp b, which consists of 3.0kg / adt DTPA, 3.0kg / adt MgSO4, 20kg / adt NaOH and 80kg / adt H2O2. Perform second-stage bleaching at 98°C for 40min, centrifuge and dehydrate to a pulp concentration of 25wt% to form pulp c, dilute pulp c to 17wt%, and then refine with a disk spacing of 0.8mm. Wash and screen after refining to obtain kenaf whole-stalk APMP pulp.

[0046] Example 3

[0047] The method for preparing the whole kenaf 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 decomposition machine extrusion: material a is pre-steamed at 90°C for 60 minutes, and the pre-steamed material is extruded and decomposed by MSD to obtain material b;

[0050] S3, pre-impregnation: add material b to a pre-impregnation solution with a concentration of 10wt%, the pre-impregnation solution consists of 1.5kg / adt DTPA, 1.5kg / adt MgSO4, 10kg / adt NaOH, 10kg / adt H2O2, and 15kg / adt ionic liquid, and perform ultrasonic treatment at 40kHz and 90°C for 60min to form a slurry, wash the slurry, and centrifuge and dehydrate it to a concentration of 25wt% to obtain slurry a;

[0051] S4, one-stage high-concentration refining and bleaching: the pulp a is refined by a disc mill, the disc spacing is set to 0.8 mm, the refining concentration is controlled at 30wt%, and after the high-concentration refining pulp is formed, a 10wt% concentration regulating liquid a is added, the regulating liquid a is composed of 2.0kg / adt of DTPA, 2.0kg / adt of MgSO4, 15kg / adt of NaOH, and 30kg / adt of H2O2, bleached at 90°C for 60min, and centrifuged to dehydrate to a pulp concentration of 30wt%, to obtain pulp b;

[0052] S5. Second-stage bleaching and low-concentration refining: add 10wt% regulating liquid b to pulp b, wherein regulating liquid b consists of 3.0kg / adt DTPA, 3.0kg / adt MgSO4, 20kg / adt NaOH and 60kg / adt H2O2, and carry out second-stage bleaching at 90°C for 60min. After the bleaching, centrifuge and dehydrate the pulp to a pulp concentration of 30wt% to form pulp c. Dilute pulp c to 20wt%, and then refine the pulp with a disk spacing of 0.6mm. After the bleaching, wash and screen 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 the raw material, and the APMP pulping process of the present invention is adopted. The rest is consistent with Example 1.

[0057] Comparative Example 3

[0058] The pulping is carried out by the method in the patent "CN 1234936C".

[0059] Comparative Example 4

[0060] The pulping is carried out by the method in the 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 can be seen from Table 1, the pulp prepared by the kenaf whole stalk APMP pulping process of Examples 1-3 of the present invention has good pulp properties, wherein the tensile index and cohesive strength are significantly better than the wood raw materials of the existing conventional comparative examples 1-2, indicating that the raw material for APMP pulping using kenaf whole stalks is better than wood; and is also better than the pulp obtained by the pulping processes of comparative examples 3 and 4. The pulping process of comparative example 3 is chemical thermomechanical pulping, while the APMP pulping process used in the present invention, wherein pre-steaming and chemical impregnation are both carried out at normal pressure, pulping and bleaching are combined into one, and the bleaching process is completed while pulping, the operation is simple and the energy consumption is low, and the obtained pulp has good pulp properties. The quality characteristics of the APMP pulp obtained by the preparation steps of comparative example 4 are significantly biased relative to the strength of the present invention. The pre-impregnation liquid of comparative example 5 lacks ionic liquid, and the performance of the obtained pulp is also reduced.

[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 protection scope 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: cutting air-dried kenaf stalks into strips, washing and removing impurities to obtain material a; S2, pre-steaming and screw extrusion decompression machine extrusion: pre-steaming material a, extruding and decompressing 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 centrifugally dehydrating it to a concentration of 20-30wt% to obtain slurry a; S4, one-stage high-concentration refining and bleaching: refining pulp a to form a high-concentration refining pulp, adding the high-concentration refining pulp into regulating liquid a for bleaching, and centrifugally dehydrating to a concentration of 20-30wt% to obtain pulp b; S5. Second-stage bleaching and low-concentration refining: add pulp b into regulating liquid b for second-stage bleaching, centrifuge and dehydrate to a concentration of 20-30wt%, form pulp c, dilute pulp c, and perform refining. After refining, wash and screen to obtain the target kenaf whole-stalk APMP pulp.

2. The method for preparing APMP pulp of whole kenaf stalks according to claim 1, characterized in that: In step S1, the water content of the air-dried whole 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, characterized in that: 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, characterized in that: 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; the ultrasonic treatment is carried out at 20-40kHz and 90-100°C for 40-60min.

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

6. The method for preparing APMP pulp of whole kenaf stalks according to claim 1, characterized in that: In step S4, the concentration of the regulating solution a is 10-15wt%, and the regulating solution a is composed of 1.0-3.0kg / adt of DTPA, 1.0-3.0kg / adt of MgSO4, 10-30kg / adt of NaOH, and 30-60kg / adt of H2O2; the bleaching is performed at 90-100°C for 40-60min.

7. The method for preparing APMP pulp of whole kenaf stalks according to claim 1, characterized in that: In step S5, the concentration of the regulating solution b is 10-15wt%, and the regulating solution b is composed of 1.0-3.0kg / adt of DTPA, 1.0-3.0kg / adt of MgSO4, 10-30kg / adt of NaOH, and 60-100kg / adt of H2O2.

8. The method for preparing APMP pulp of whole kenaf stalks according to claim 1, characterized in that: In step S5, the second stage bleaching is performed at 90-100°C for 40-60 minutes; the pulp c is diluted to 15-20wt%.

9. The method for preparing APMP pulp of whole kenaf stalks according to claim 1, characterized in that: In step S5, the spacing between the grinding discs is 0.6-0.8 mm.

10. A kenaf whole-stalk APMP pulp prepared by the preparation method according to any one of claims 1 to 9.

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