A method for improving hardwood alkaline peroxide mechanical pulp APMP refining

Abstract

The present invention belongs to the technical field of pulping and papermaking engineering, and particularly relates to a method for improving the refining of hardwood alkaline peroxide mechanical pulp (APMP). The treatment method is to concentrate the pulp after coarse grinding in the APMP process to a suitable pulp concentration, add LiOH / THF solution for ultrasonic treatment, wash and concentrate the treated pulp, and then the pulp enters the disc mill for refining treatment. The ultrasonic treatment conditions of LiOH / THF solution are mild and easy to implement, which can effectively swell and soften the coarsely ground pulp fibers and improve the performance of the refined pulp. This technology can reduce the energy consumption of refining, reduce the cutting of fibers, improve the physical strength of pulp, strengthen the softening and bonding properties of the conduit, and correspondingly improve the papermaking performance of pulp, thereby reducing production costs.

Description

Technical Field

[0001] The invention belongs to the technical field of pulping and papermaking engineering, and relates to a method for improving APMP refining of hardwood. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Broadleaf wood generally refers to trees of dicotyledonous plants, including poplar, eucalyptus, birch and acacia, which are important raw materials for pulping and papermaking fibers. In terms of pulping methods, there are chemical pulp and high-yield pulp for primary pulp. Alkaline peroxide mechanical pulp (APMP) is an important high-yield pulping method. Compared with chemical pulp, APMP pulping equipment investment is low, pulping yield is high, wastewater pollution load is low, and some performance indicators of pulp are superior, such as high bulk, stiffness, ink absorption and opacity. Therefore, APMP pulp has developed rapidly and its application field has been continuously expanded. It is widely used in printing papers such as newsprint, household paper, packaging paper, offset book paper, low-weight coated paper and super calendered paper. There are also some problems in the production and application of APMP pulp, mainly including high pulping energy consumption, large fiber cutting degree, high fine fiber content, poor water filtration performance, low physical strength and poor whiteness stability. These disadvantages limit the further development and application of APMP pulp.

[0004] The APMP pulping process is divided into two steps: first, the wood chips are dissociated into single fibers, minimizing the generation of fragments and maintaining the fiber length. At this stage, the pulping concentration should be higher and the pulping gap should be larger, so that the wood chips are dissociated under the action of mutual friction and the fiber cutting is reduced, which is the coarse pulping process; followed by further dissociation and fibrillation of fiber bundles and fibers. The fibers should be subjected to more mechanical action to increase the number of times the fibers contact the toothed disc blade per unit time. The pulping concentration should be lower and the disc grinding gap should be smaller, which is the fine pulping stage. From the perspective of the pulping process, fine pulping has a great influence on the pulping energy consumption and pulp properties. Fiber modification is one of the important ways to improve the fine pulping process and product quality of hardwood APMP pulp. Summary of the invention

[0005] In order to improve the production and product quality of hardwood APMP pulp, the present invention provides a method for improving the refining of APMP pulp.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a method for improving hardwood alkaline hydroperoxide mechanical pulp (APMP) refining, comprising:

[0008] Concentrating the coarsely ground slurry to obtain a concentrated slurry;

[0009] The concentrated slurry is subjected to short-term ultrasonic treatment using a LiOH / THF solution, washed, and concentrated to obtain a slurry;

[0010] The slurry is finely ground to obtain.

[0011] The second aspect of the present invention provides refined pulp prepared by the above-mentioned method for improving hardwood alkaline hydroperoxide mechanical pulp (APMP) refining.

[0012] The third aspect of the present invention provides the use of LiOH / THF solution in improving the refining performance of hardwood alkaline hydroperoxide mechanical pulp APMP, wherein the performance includes: refining energy consumption, water filtration performance, physical strength, surface strength of paper sheets, and papermaking performance of pulp.

[0013] Beneficial effects of the present invention

[0014] (1) The fiber treatment conditions are mild and easy to implement. The present invention can reduce the energy consumption of pulping, reduce the cutting effect of fibers and the generation of fine fibers, improve the water filtration performance and physical strength of pulp; strengthen the softening of vascular cells, improve the surface strength of paper sheets, and correspondingly help improve the papermaking performance of pulp.

[0015] (2) The preparation method of the present invention is simple, practical and easy to promote. DETAILED DESCRIPTION

[0016] It should be noted that the following detailed descriptions are illustrative and 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 meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0017] A technology for improving the fine grinding of APMP pulp includes the following steps: concentrating the pulp after coarse grinding to a pulp concentration of 25-35%, using LiOH / THF (tetrahydrofuran) solution for short-time ultrasonic treatment, washing the treated pulp, concentrating it to a pulp concentration of 20-25%, and then the pulp enters a disc mill for fine grinding treatment.

[0018] APMP pulp has a high yield, the fiber components are well preserved, the cell wall structure is dense, the fiber is a layered structure, the outer primary wall P layer and the secondary wall outer layer S1 fine fibers are randomly arranged in a mesh structure, the lignin is a guaiac-based and syringyl structural unit, the P and S1 layer structures are dense, and the resistance to mechanical and chemical actions is large, which limits the water absorption and swelling, fine fiberization and filament brooming effect of the secondary wall middle layer S2. Therefore, a higher beating energy is required to break up P and S1 first, otherwise it is difficult to obtain a suitable beating degree and an ideal fiber morphology. This not only increases the refining energy consumption, but also excessive beating energy causes excessive fiber cutting, resulting in a large number of fine fibers. Ultrasonic treatment with LiOH / THF solution can effectively swell the interface of microfibers, weaken the connection, loosen the connection between lignin and hemicellulose between microfibers, and specifically loosen the P and S1 layers of pulp fibers, which is beneficial for removal in the subsequent refining stage. The weakening between microfibers can promote the absorption, swelling and fibrillation effect of the S2 layer in the middle layer of the secondary wall.

[0019] In some embodiments, the raw material is hardwood APMP pulp after a coarse grinding.

[0020] In some embodiments, the concentration of the LiOH / THF solution is 1-3% (m / v).

[0021] In some embodiments, the treatment conditions are: LiOH / THF solution dosage 0.05-0.12 g / g slurry, ultrasonic time 20-80 s, temperature 40-60 °C.

[0022] In some embodiments, the pulping process of the APMP pulp includes: wood chip steaming, one-stage extrusion, one-stage chemical impregnation, two-stage extrusion, two-stage chemical impregnation, coarse pulping, washing, fine pulping, and de-latency removal.

[0023] In some embodiments, the hardwood includes: poplar, eucalyptus, acacia, birch.

[0024] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0025] Example 1

[0026] Poplar APMP pulp was produced by conventional two-stage extrusion and impregnation treatment, and the process was as follows: steaming of poplar wood chips → one-stage extrusion → one-stage chemical impregnation → two-stage extrusion → two-stage chemical impregnation → coarse grinding → washing → fine grinding → latent elimination. The conditions for the first-stage chemical treatment were: NaOH dosage 3.1%, H2O2 dosage 3.0%, Na2SiO3 dosage 2.3%, MgSO4 dosage 0.04%, EDTA dosage 0.2%, temperature 65°C, liquid ratio 1:4, time 60 min. The process conditions for the second-stage chemical treatment were: NaOH dosage 3.2%, H2O2 dosage 3.3%, Na2SiO3 dosage 2.5%, MgSO4 dosage 0.04%, EDTA dosage 0.3%, temperature 70°C, liquid ratio 1:4, time 60 min. Then coarse grinding, washing, fine grinding and latent elimination were carried out to obtain poplar APMP pulp. The pulp beating degree obtained under this treatment process was 47.5 O SR, energy consumption is 1423 kW•h / t pulp, brightness is 76.7% ISO, bulk thickness is 2.26 cm 3 ·g -1 , bursting index 2.76 KPa•m 2 •g -1 , tensile index 43.5 N·m / g, tear index 2.75 mN·m 2 •g -1 , surface strength 0.81 m / s.

[0027] The technology of the present invention is used to produce poplar APMP pulp. The steaming, extrusion, chemical impregnation and rough grinding of poplar wood chips are the same as the conventional treatments mentioned above. After rough grinding, the pulp is concentrated to a pulp concentration of 30%. The concentration of LiOH / THF solution is 2% (m / v), the amount of LiOH / THF solution is 0.08 g / g pulp, the ultrasonic time is 80 s, the temperature is 50 ° C, and after LiOH / THF solution treatment, the pulp is concentrated to a pulp concentration of 20% for fine grinding. Then, the latent removal treatment is performed to obtain APMP pulp. The pulp beating degree obtained under the treatment process is 47.6 O SR, energy consumption is 1256 kW•h / t pulp, brightness is 76.8% ISO, bulk thickness is 2.27 cm 3 ·g -1 , bursting index 2.92KPa•m 2 •g -1 , tensile index 49.3 N·m / g, tear index 2.98 mN·m 2 •g -1 , surface strength 1.05 m / s.

[0028] Example 2

[0029] Eucalyptus APMP pulp is produced by conventional one-stage extrusion impregnation treatment, and the process is: eucalyptus chips steaming → extrusion → chemical impregnation → coarse grinding → washing → fine grinding → de-latency removal. The chemical treatment conditions are: NaOH dosage 3.5%, H2O2 dosage 3.3%, Na2SiO3 dosage 2.5%, MgSO4 dosage 0.05%, EDTA dosage 0.3%, temperature 75°C, liquid ratio 1:4, time 70min. Then coarse grinding, washing, fine grinding and de-latency removal treatment are carried out to obtain eucalyptus APMP pulp. The pulp beating degree obtained under this treatment process is 43.2 O SR, energy consumption is 1517 kW•h / t pulp, brightness is 74.2%ISO, bulk thickness is 2.52 cm 3 ·g -1 , bursting index 2.32 KPa•m 2 •g -1 , tensile index 38.2 N·m / g, tear index 2.32 mN·m 2 •g -1 , surface strength 0.68m / s.

[0030] The technology of the present invention is used to produce eucalyptus APMP pulp. The steaming, extrusion, chemical impregnation and rough grinding of eucalyptus chips are the same as the conventional treatments mentioned above. After rough grinding, the pulp is concentrated to a pulp concentration of 35%. The concentration of LiOH / THF solution is 1% (m / v), the amount of LiOH / THF solution is 0.12 g / g pulp, the ultrasonic time is 60 s, the temperature is 60 ° C, and after LiOH / THF solution treatment, the pulp is concentrated to a pulp concentration of 22% for fine grinding. Then, the latent removal treatment is performed to obtain APMP pulp. The pulp beating degree obtained under the treatment process is 43.4 O SR, energy consumption is 1328 kW•h / t pulp, brightness is 74.8% ISO, bulk thickness is 2.67 cm 3 ·g -1 , bursting index 2.58KPa•m 2 •g -1 , tensile index 42.6 N·m / g, tear index 2.58 mN·m 2 •g -1 , surface strength 0.85 m / s.

[0031] Example 3

[0032] Acacia APMP pulp was prepared by conventional two-stage extrusion and impregnation treatment, and the process was: steaming of acacia wood chips → one-stage extrusion → one-stage chemical impregnation → two-stage extrusion → two-stage chemical impregnation → rough grinding → washing → fine grinding → latent elimination. The conditions for the first-stage chemical treatment were: NaOH dosage 3.2%, H2O2 dosage 3.1%, Na2SiO3 dosage 2.4%, MgSO4 dosage 0.04%, EDTA dosage 0.2%, temperature 68℃, liquid ratio 1:4, time 65 min. The process conditions for the second-stage chemical treatment were: NaOH dosage 3.3%, H2O2 dosage 3.4%, Na2SiO3 dosage 2.4%, MgSO4 dosage 0.04%, EDTA dosage 0.2%, temperature 72℃, liquid ratio 1:4, time 64 min. Then rough grinding, washing, fine grinding and latent elimination were carried out to obtain Acacia APMP pulp. Under this treatment process, the pulp beating degree is 45.2 O SR, energy consumption is 1376 kW•h / t pulp, brightness is 75.1% ISO, bulk thickness is 2.29 cm 3 ·g -1 , bursting index 2.86 KPa•m 2 •g -1 , tensile index 46.2 N·m / g, tear index 2.89 mN·m 2 •g -1 , surface strength 0.85 m / s.

[0033] The technology of the present invention is used to produce acacia APMP pulp. The steaming, extrusion, chemical impregnation and rough grinding of acacia wood chips are the same as the conventional treatments mentioned above. After rough grinding, the pulp is concentrated to a pulp concentration of 25%. The concentration of LiOH / THF solution is 3% (m / v), the amount of LiOH / THF solution is 0.10 g / g pulp, the ultrasonic time is 40 s, the temperature is 45 ° C, and after LiOH / THF solution treatment, the pulp is concentrated to a pulp concentration of 25% for fine grinding. Then, the latent removal treatment is carried out to obtain acacia APMP pulp. The pulp beating degree obtained under the treatment process is 45.3 O SR, energy consumption is 1208 kW•h / t pulp, brightness is 75.5% ISO, bulk thickness is 2.32 cm 3 ·g -1 , bursting index 2.98 KPa•m 2 •g -1 , tensile index 49.3 N·m / g, tear index 2.99 mN·m 2 •g -1 , surface strength 1.12 m / s.

[0034] Example 4

[0035] Birch APMP pulp is produced by conventional one-stage extrusion impregnation treatment, and the process is: birch chip steaming → extrusion → chemical impregnation → coarse grinding → washing → fine grinding → delatency removal. The chemical treatment conditions are: NaOH dosage 3.4%, H2O2 dosage 3.2%, Na2SiO3 dosage 2.3%, MgSO4 dosage 0.04%, EDTA dosage 0.4%, temperature 72°C, liquid ratio 1:4, time 68min. Then coarse grinding, washing, fine grinding and delatency removal treatment are carried out to obtain birch APMP pulp. The pulp beating degree obtained under this treatment process is 42.7 O SR, energy consumption is 1523 kW•h / t pulp, brightness is 75.3%ISO, bulk thickness is 2.54 cm 3 ·g -1 , bursting index 2.35 KPa•m 2 •g -1 , tensile index 37.6 N·m / g, tear index 2.45 mN·m 2 •g -1 , surface strength 0.71m / s.

[0036] The birch APMP pulp is produced by the technology of the present invention. The steaming, extrusion, chemical impregnation and rough grinding of birch chips are the same as the conventional treatments mentioned above. After rough grinding, the pulp is concentrated to a pulp concentration of 28%. The concentration of LiOH / THF solution is 2.4% (m / v), the amount of LiOH / THF solution is 0.05 g / g pulp, the ultrasonic time is 20 s, the temperature is 40 °C, and after LiOH / THF solution treatment, the pulp is concentrated to a pulp concentration of 24% for fine grinding. Then, the latent removal treatment is performed to obtain APMP pulp. The pulp beating degree obtained under the treatment process is 43.1 O SR, energy consumption is 1326 kW•h / t pulp, brightness is 75.7% ISO, bulk thickness is 2.64 cm 3 ·g -1 , bursting index 2.62KPa•m 2 •g -1 , tensile index 41.2 N·m / g, tear index 2.67 mN·m 2 •g -1 , surface strength 1.02 m / s.

[0037] The chemical treatment conditions and process parameters listed in the above Examples 1-4 are only a part listed to illustrate the technical solution of the present invention. The technical solution of the present invention is not limited to the above-mentioned chemical dosage and treatment process. The choice of chemical dosage is diverse. Regardless of the combination of dosages, the treatment technology provided by the present invention can produce high-quality pulp and greatly reduce production costs. This can be inferred by technicians in this field based on the above records. Because it is impossible to list them all, no more examples are given here.

Claims

1. A method for improving hardwood alkaline peroxide mechanical pulp (APMP) refining, characterized in that: include: Concentrating the coarsely ground slurry to obtain a concentrated slurry; The concentrated slurry is subjected to short-term ultrasonic treatment using a LiOH / THF solution, washed, and concentrated to obtain a slurry; The specific conditions of the short-time ultrasonic treatment are as follows: the amount of LiOH / THF solution is 0.05-0.12 g / g slurry, the ultrasonic time is 20-80s, and the temperature is 40-60°C; The slurry is finely ground to obtain.

2. The method for improving hardwood alkaline hydroperoxide mechanical pulp (APMP) refining according to claim 1, characterized in that: The coarsely ground pulp is pulp obtained by coarsely grinding APMP of hardwood.

3. The method for improving hardwood alkaline hydroperoxide mechanical pulp (APMP) refining according to claim 1, characterized in that: The concentrated pulp has a pulp concentration of 25-35%.

4. The method for improving hardwood alkaline peroxide mechanical pulp (APMP) refining according to claim 1, characterized in that: The concentration of LiOH / THF solution was 1-3% m / v.

5. The method for improving hardwood alkaline peroxide mechanical pulp (APMP) refining as claimed in claim 1, characterized in that: The slurry concentration is 20-25%.

6. The method for improving hardwood alkaline hydroperoxide mechanical pulp (APMP) refining according to claim 1, characterized in that: The pulping process of the APMP refined pulp includes: wood chip steaming, one-stage extrusion, one-stage chemical impregnation, two-stage extrusion, two-stage chemical impregnation, coarse pulping, washing, refined pulping, and latent removal.

7. The method for improving hardwood alkaline peroxide mechanical pulp (APMP) refining according to claim 1, characterized in that: The broadleaf wood includes: poplar, eucalyptus, acacia and birch.

8. Refined pulp prepared by the method for improving hardwood alkaline hydroperoxide mechanical pulp (APMP) refining as described in any one of claims 1 to 7.

9. Application of the method according to any one of claims 1 to 7 in improving the refining performance of hardwood alkaline hydroperoxide mechanical pulp (APMP), characterized in that: The properties include: pulping energy consumption, water filtration performance, physical strength, surface strength of paper sheets, and papermaking performance of pulp.