Energy-saving pulping method based on pretreatment strengthening and segmented enzyme activation

Abstract

The invention discloses an energy-saving pulping method based on pretreatment strengthening and segmented enzyme activation, and belongs to the technical field of pulping and papermaking. According to the pulping method provided by the invention, p-toluenesulfonic acid is added in pretreatment to adjust pH and strengthen enzyme activity, and enzyme is wrapped by using a temperature or pH response type carrier, so that pectinase, cellulase and laccase can be controlled to be released and activated in a proper treatment stage. By accurately controlling the enzyme action sequence, substrate competition is avoided, enzyme inactivation is reduced, the enzymolysis efficiency and the utilization rate are effectively improved, and the COD content of wastewater is reduced; and two-stage pulping and p-toluenesulfonic acid are combined to soften fibers synergistically, so that the power consumption per ton of pulp is reduced. According to the invention, fiber fibrillation is promoted through enzyme treatment, and the tensile strength and the water retention value are effectively improved; the laccase catalyzes crosslinking of lignin, so that the wet strength is remarkably improved. The paper pulp provided by the invention gives consideration to physical properties and environmental protection requirements of high-strength packaging paper manufacturing, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the field of pulp and paper making, and particularly to an energy-saving pulping method based on pretreatment strengthening and segmented enzyme activation. Background Art

[0002] In the process of pulp production, the separation and refinement of fibers are the core steps determining the properties of the formed paper. Traditional mechanical pulping methods rely on physical shear force to achieve fiber dissociation. Although they can improve the fibrillation degree of fibers, there are problems such as high energy consumption (accounting for 20%-35% of the total energy consumption in pulp production), serious equipment wear (the life of the grinding disc is shortened by 30%-50%), and excessive fiber damage (the average fiber length is reduced by 15%-25%), resulting in a decrease in the strength and uniformity of the formed paper. Chemical impregnation methods (such as the sulfate method) destroy the lignin structure through strong alkalis or strong acids to improve fiber separation efficiency, but they will produce highly toxic wastewater (COD up to 5000-8000 mg / L), emissions of volatile organic compounds (such as methanethiol), and chemical residues on fibers (such as chlorinated lignin), seriously threatening the ecological environment and product safety.

[0003] In recent years, the biological enzyme pulping process has become a research hotspot due to its environmental friendliness and high catalytic characteristics. For example, cellulase, xylanase, etc. can specifically degrade the components of the fiber cell wall (such as pectin, hemicellulose), and achieve fiber softening and separation under mild conditions (40-60°C, pH 4.0-7.0), reducing the pulping energy consumption by 20%-40% and reducing fiber damage (the fiber length retention rate is increased by 10%-15%). However, this technology still faces three major bottlenecks:

[0004] (1) Low enzyme synergy efficiency: The synchronous action of the compound enzyme is prone to cause substrate competition (such as the competition between cellulase and xylanase for cellulose), resulting in a 30%-50% decrease in the enzymatic hydrolysis efficiency;

[0005] (2) Poor environmental adaptability: The enzyme activity is limited by fixed pH / temperature conditions (for example, the optimal pH of pectinase is 4.8-5.2, while laccase requires pH 7.0-8.0), and it is difficult to adapt to the dynamic changes of the pulping process;

[0006] (3) Fiber property contradiction: Although enzymatic softening reduces energy consumption, it may overly damage the fiber structure, resulting in the deterioration of drainage performance (the Schopper value decreases by 10%-20%) and wet strength (decreases by 15%-30%).

[0007] In view of the above problems, researchers have tried to improve the technical feasibility through enzyme molecule modification and process optimization. For example, the patent "Production process and application of a bio-enzyme modified high-strength paper (patent publication number CN113564962A)" proposes a compounding scheme of cellulase, xylanase, pectinase and laccase. However, its synchronous enzyme treatment mode fails to solve the problems of substrate competition and stage adaptability, and lacks precise control of the enzyme activity environment, resulting in insignificant improvement in the wet strength of the formed paper and unclear reduction in the electricity consumption per ton of pulp. Summary of the Invention

[0008] The object of the present invention is to provide an energy-saving pulping method based on pretreatment strengthening and staged enzyme activation to solve the problems existing in the above-mentioned prior art. The present invention combines p-toluenesulfonic acid with a bio-enzyme and combines a staged enzyme activation system to precisely control the timing of enzyme action, improve the catalytic efficiency and adaptability of the bio-enzyme, optimize the physical and chemical properties of the pulp, thereby enhancing the packaging performance of paper-based products, and at the same time achieving the production goal of energy conservation and environmental protection.

[0009] To achieve the above object, the present invention provides the following solutions:

[0010] The present invention provides a pulping method with staged enzyme activation, including the following steps:

[0011] Take wood pulp raw materials and mix them with water, add p-toluenesulfonic acid, add a bio-enzyme compounding system, stir at 100 - 300 rpm for 40 - 50 min at a pH of 4.8 - 5.0 and a temperature of 45 - 50 °C to obtain pretreated pulp;

[0012] Heat the pretreated pulp to 55 - 60 °C, concentrate it to an absolutely dry fiber concentration of 40 - 42%, with a disc gap of 0.25 - 0.3 mm, and grind at 3000 - 3200 rpm for 8 - 10 min to obtain high-concentration ground pulp;

[0013] Dilute the high-concentration ground pulp to an absolutely dry fiber concentration of 10% - 12%, and defibrate it at 50 - 55 °C for 15 - 20 min to obtain defibrated pulp;

[0014] Dilute the defibrated pulp to an absolutely dry fiber concentration of 3.5% - 5%, with a disc gap of 0.06 - 0.08 mm, and grind at 2000 - 2200 rpm for 15 - 20 min to obtain low-concentration ground pulp;

[0015] Adjust the pH of the low-concentration ground pulp to 8.5 - 8.8, crosslink it, concentrate it to an absolutely dry fiber concentration of 3.2% - 3.5%, wash it, and dilute and adjust it to obtain the finished pulp for paper machine papermaking.

[0016] Preferably, the mass of the p-toluenesulfonic acid is 0.4% - 0.5% of the mass of the absolutely dry fibers in the wood pulp raw materials.

[0017] Preferably, the bio-enzyme complex system includes 20-25 U / g of cellulase, 12-15 U / g of xylanase, 6-8 U / g of pectinase, and 4-5 U / g of laccase.

[0018] Preferably, the cellulase is encapsulated in a temperature-sensitive hydrogel; the xylanase and the pectinase are respectively encapsulated in low-pH-sensitive microcapsules; the laccase is encapsulated in high-pH-sensitive microcapsules.

[0019] Preferably, the temperature-sensitive hydrogel is poly(N-isopropylacrylamide); the low-pH-sensitive microcapsule is polymethyl methacrylate; the high-pH-sensitive microcapsule is a chitosan-sodium alginate complex.

[0020] Preferably, the dilution is adjusted to adjust the on-machine concentration of the washed pulp to 0.9%-1.0% through the pulp dilution system in the stuff box.

[0021] The present invention also provides a finished pulp obtained by the above pulping method.

[0022] The present invention also provides an application of the above finished pulp in papermaking.

[0023] Preferably, the paper is high-strength packaging paper.

[0024] The present invention also provides a high-strength packaging paper, which is made of the above finished pulp.

[0025] The present invention discloses the following technical effects:

[0026] (1) Intelligent staged enzyme activation system

[0027] In the present invention, enzymes (pectinase → cellulase → laccase) are released step by step through pH / temperature-sensitive carriers, accurately controlling the order of enzyme action, avoiding substrate competition, effectively improving the enzymatic hydrolysis efficiency, and combining two-stage grinding (high consistency + low consistency) and p-toluenesulfonic acid to synergistically soften the fibers, greatly reducing the power consumption per ton of pulp.

[0028] (2) Green environmental protection and efficient resource utilization

[0029] The present invention uses bio-enzymes to replace strong alkali / chlorine-based chemicals, significantly reducing the COD content of wastewater. The microcapsule technology reduces enzyme inactivation and improves enzyme utilization rate; it is compatible with various wood pulp raw materials (softwood, hardwood, etc.), reduces the dependence on high-quality fibers, and significantly optimizes the comprehensive carbon emissions.

[0030] (3) Multi-dimensional strengthening of fiber properties

[0031] The enzyme treatment of the present invention promotes fibrillation of fibers, effectively improving the tensile strength and water retention value; laccase catalyzes the crosslinking of lignin, significantly enhancing the wet strength, taking into account both the physical properties and environmental requirements of high-strength packaging paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0033] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be construed as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0037] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are merely exemplary.

[0038] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0039] The present invention innovatively introduces p-toluenesulfonic acid as an enzyme activity enhancer and designs a "phased enzyme activation system", breaking through the limitations of the prior art. The specific innovation mechanism is as follows:

[0040] (1) Chemical enhancement mechanism: P-toluenesulfonic acid stabilizes the acidic environment (pH 4.5 - 5.5) through the sulfonic acid group, enhances the activity of pectinase, inhibits the non-specific hydrolysis of cellulase in the pretreatment stage, promotes the binding of laccase precursor to the phenolic hydroxyl group of lignin, realizes the pre-activation of lignin, and at the same time penetrates into the amorphous region of the fiber to reduce the crystallinity, providing a basis for fiber plasticization.

[0041] (2) Phased enzyme controlled release: Utilize temperature / pH-responsive carriers (such as polymethacrylate-based materials, poly(N-isopropylacrylamide) hydrogel, chitosan microcapsules) to achieve the sequential release of pectinase (pretreatment stage), cellulase (pulping stage), and laccase (post-treatment stage), avoid substrate competition, and make the fiber fibrillation (improve water retention value) and lignin cross-linking (improve wet strength) synergistically enhance.

[0042] The present invention shows significant advantages in reducing pulping energy consumption (such as electricity consumption per ton of pulp), improving the properties of the formed paper (such as tensile strength), and reducing environmental pollution (such as wastewater COD) through chemical-biological synergistic action and dynamic enzyme controlled release technology, providing an innovative solution for green pulp manufacturing.

[0043] Unless otherwise specified, the concentration of the pulp described in the present invention is the mass fraction of the absolute dry fiber in the pulp.

[0044] Example 1

[0045] 1. Preparation process

[0046] The process flow of the present invention (as Figure 1 shown) includes the following steps:

[0047] Raw material preparation: Select poplar APMP pulp as the wood pulp raw material (absolute dry fiber content 15%), carry out screening and purification, remove impurities, and ensure the uniformity and consistency of the fibers.

[0048] Prepare a bio-enzyme compound system: Use low pH-sensitive microcapsules (polymethyl methacrylate) to wrap pectinase (8U / g) and xylanase (12U / g) respectively, use poly(N-isopropylacrylamide) to wrap cellulase (20U / g), and use a chitosan-sodium alginate composite carrier to wrap laccase (5U / g). The specific preparation methods are as follows:

[0049] (1) Preparation method of low pH-sensitive microcapsules (polymethyl methacrylate) wrapped with pectinase

[0050] a) Raw material preparation

[0051] Preparation of monomer mixture: Methyl methacrylate (MMA) and methacrylic acid (MAA) were mixed at a mass ratio of 7:3 to form a functional comonomer system; Ethylene glycol dimethacrylate (EGDMA) was added to the above monomer mixture, and its addition amount was 1% (w / w) of the total mass of the monomers, serving as a three-dimensional network crosslinking agent; Ammonium persulfate (APS) was dissolved in the reaction system, and its mass concentration was controlled to be 0.5% (w / w) of the total amount of monomers, serving as a free radical polymerization initiator.

[0052] Pre-modulation of enzyme solution: Pectinase was dissolved in phosphate buffer at pH 5.0, and the final concentration of enzyme protein was adjusted to 10 mg / mL to obtain a homogeneous enzyme-loaded solution.

[0053] b) Emulsification and polymerization

[0054] The monomer mixture and the pectinase solution were mixed at a volume ratio of 3:1 (v / v), and sodium dodecyl sulfate (SDS) was added as an emulsifier, and its dosage was 1% (w / w) of the total mass of the mixed system; Under nitrogen protection, the reaction was carried out with stirring (600 rpm) in a 40 °C water bath for 6 h to form a microcapsule suspension; The suspension was centrifuged (8000 rpm, 10 min) to collect the microcapsules, washed 3 times with deionized water, and freeze-dried for later use.

[0055] c) Key parameters

[0056] pH responsiveness: By adjusting the MMA / MAA ratio to control the carboxyl density, carboxyl protonation was achieved at pH 4.8 - 5.2, and the microcapsules swelled to release pectinase;

[0057] Entrapment efficiency: ≥80% (determined by the BCA method for the enzyme content in the microcapsules);

[0058] Enzyme activity retention rate: ≥90% (compared with the activity of free enzyme).

[0059] (2) Preparation method of thermosensitive hydrogel (poly N-isopropylacrylamide) encapsulated cellulase

[0060] a) Preparation of prepolymer solution

[0061] The N-isopropylacrylamide (NIPAM) monomer was dissolved in deionized water to prepare a prepolymer solution with a concentration of 10% (w / v); N,N'-methylenebisacrylamide (MBA) was added to the above solution, and its concentration was controlled to be 0.5% (w / v) to form a crosslinkable prepolymer network; Cellulase was added to a final concentration of 5 mg / mL, and then N,N,N',N'-tetramethylethylenediamine (TEMED) and potassium persulfate (KPS) were added, and their concentrations were 0.1% (v / v) and 0.5% (w / v) respectively, constituting a redox initiation system.

[0062] b) In-situ polymerization

[0063] Place the prepolymer solution in an ice bath, bubble nitrogen for 10 min to remove dissolved oxygen and inhibit side reactions; transfer it to an incubator at 25 °C and let it stand for polymerization for 2 h to form a three-dimensional network hydrogel with thermosensitive properties; cut the hydrogel into particles with a particle size of 1-2 mm, immerse them in phosphate buffer solution (PBS) with pH 6.0 for swelling equilibrium, and obtain a dried hydrogel carrier after freeze-drying.

[0064] c) Temperature-controlled release mechanism

[0065] LCST design: By adjusting the NIPAM / MBA ratio, the lower critical solution temperature (LCST) of the hydrogel is 50 °C;

[0066] Temperature response: When the temperature rises to 50-60 °C, the hydrogel shrinks and releases cellulase;

[0067] Enzyme activity retention rate: ≥85% (compared with free enzyme activity).

[0068] (3) Preparation method of high pH-sensitive microcapsules (chitosan-sodium alginate composite carrier) encapsulating laccase

[0069] a) Raw material preparation

[0070] Preparation of chitosan solution: Dissolve chitosan with a deacetylation degree of ≥90% in 1% (w / v) acetic acid solution (pH 4.0), and adjust its mass volume concentration to 2% (w / v);

[0071] Preparation of sodium alginate solution: Dissolve sodium alginate in deionized water to prepare a solution with a mass volume concentration of 2% (w / v), and adjust the pH to 7.0;

[0072] Modulation of laccase solution: Dissolve laccase in Tris-HCl buffer solution with pH 7.0, and adjust the final concentration of enzyme protein to 5 mg / mL.

[0073] b) Layer-by-layer self-assembly embedding

[0074] Mix the laccase solution and sodium alginate solution at a volume ratio of 1:1 (v / v), and dropwise add them to 2% (w / v) calcium chloride (CaCl2) solution to form sodium alginate-laccase gel beads with a particle size of 1-2 mm; immerse the gel beads in the chitosan solution for 10 min to allow chitosan to adsorb on the surface of the gel beads through electrostatic interaction to form a composite outer layer; repeat the above steps 3 times to form a three-layer chitosan-sodium alginate alternating coating structure, obtain composite microcapsules, and keep them for use after freeze-drying.

[0075] c) pH-responsive release

[0076] Alkaline triggering: When pH ≥ 8.0, the sodium alginate layer dissociates and releases laccase;

[0077] Entrapment efficiency: ≥ 75% (calculated by detecting laccase activity);

[0078] Retention rate of enzyme activity: ≥ 80% (compared with the activity of free laccase).

[0079] Pretreatment: Mix the wood pulp raw material with water, adjust the pulp concentration to 8%, add p-toluenesulfonic acid solution (the mass of p-toluenesulfonic acid is 0.5% of the weight of oven-dry fiber), stabilize the pH of the reaction system at 5.0 through the pH automatic regulation system, and add the bio-enzyme complex system. Heat to 50 °C and stir at 100 rpm for 50 min. In the pretreatment stage, the acidic environment of p-toluenesulfonic acid triggers the release of pectinase and xylanase from the low-pH sensitive microcapsules, preferentially degrading the pectin layer of the fiber primary wall and exposing the secondary wall structure.

[0080] Enzyme treatment: Heat the pulp to 55 °C, and the cellulase encapsulated by the thermosensitive hydrogel is released in stages, synergistically stripping the interface of the S1 / S2 layer of the fiber secondary wall to promote fibrillation.

[0081] High-consistency refining: Concentrate the pulp to a concentration of 42%, use a high-consistency refiner (Andritz double-disc refiner), with a gap of 0.25 mm, a rotational speed of 3200 rpm, and grind for 8 min. This can reduce the power consumption per ton of pulp.

[0082] Defibrillation treatment: Feed the pulp after high-consistency refining into a spiral defibrillator, adjust the pulp concentration to 12%, and defibrillate at 55 °C for 15 min. Eliminate the internal stress of the fiber to avoid fiber breakage during subsequent low-consistency refining.

[0083] Low-consistency refining: Dilute the defibrillated pulp to a concentration of 4%, use a low-consistency refiner (Voith FibreFlow) with a gap of 0.08 mm and a rotational speed of 2200 rpm, and grind for 15 min. Further refine the fiber and improve the water retention value.

[0084] Post-treatment and control of the finished pulp: Adjust the pH of the pulp to 8.5 to trigger the release of laccase from the chitosan-sodium alginate microcapsules, catalyze the oxidative cross-linking of lignin, and improve the wet strength. Subsequently, the pulp is concentrated to 3.5% by a multi-disc concentrator, washed to remove residual enzymes and impurities, and then the online concentration is adjusted to 1.0% through the dilution system of the headbox (Kadant dilution valve), and the pH is adjusted to 6.5 for direct papermaking on the paper machine.

[0085] 2. Effect evaluation:

[0086] (1) Energy consumption optimization: Power consumption per ton of pulp is 750 kW·h;

[0087] (2) Changes in the crystalline region structure of fibers: The fiber crystallinity (measured by XRD) decreased from 62% to 49%;

[0088] (3) Strength improvement: The burst index is 4.5 kPa·m 2 / g, the tensile index is 72 N·m / g, and the wet strength is 10.25 N·m / g;

[0089] (4) Changes in fiber coarseness: The fiber coarseness decreased from 15 mg / m to 12.75 mg / m, a 15% reduction;

[0090] (5) Environmental friendliness: The COD of the wastewater is 850 mg / L, and the degradation rate of p-toluenesulfonic acid after UV / H2O2 treatment is 98%;

[0091] (6) Drainability: The Schopper value is 28°SR.

[0092] Example 2

[0093] 1. Preparation process

[0094] The process flow of the present invention (as Figure 1 shown) includes the following steps:

[0095] Raw material preparation: Select waste paper pulp (OCC, old corrugated cartons) as the wood pulp raw material (the dry fiber content is 18%), and perform screening and purification to remove impurities to ensure the uniformity and consistency of the fibers.

[0096] Preparation of the bio-enzyme complex system: Use low pH-sensitive microcapsules (polymethyl methacrylate) to separately encapsulate pectinase (6 U / g) and xylanase (15 U / g), use poly-N-isopropylacrylamide to encapsulate cellulase (25 U / g), and use a chitosan-sodium alginate composite carrier to encapsulate laccase (4 U / g). The specific preparation method is the same as that in Example 1.

[0097] Pretreatment: Mix the wood pulp raw material with water, adjust the pulp concentration to 6%, add a p-toluenesulfonic acid solution (the mass of p-toluenesulfonic acid is 0.4% of the dry fiber weight), stabilize the pH of the reaction system at 4.8 through a pH automatic adjustment system, and add the bio-enzyme complex system. Heat to 45°C and stir at 300 rpm for 40 min. In the pretreatment stage, the acidic environment of p-toluenesulfonic acid triggers the release of pectinase and xylanase from the low pH-sensitive microcapsules, preferentially degrading the pectin layer of the fiber primary wall and exposing the secondary wall structure.

[0098] Enzyme treatment: Raise the temperature of the pulp to 60°C, and the cellulase encapsulated by the temperature-sensitive hydrogel is released in stages, synergistically with xylanase to peel the S1 / S2 layer interface of the fiber secondary wall and promote fibrillation.

[0099] High-concentration refining: The pulp is concentrated to a concentration of 40%, and a high-concentration disc refiner (Andritz double-disc refiner) is used with a gap of 0.3 mm, a rotational speed of 3000 rpm, and grinding for 10 min. This can reduce the power consumption per ton of pulp.

[0100] De-stressing treatment: The pulp after high-concentration refining enters a spiral de-stresser, and the pulp concentration is adjusted to 10%, and de-stressing is carried out at 50 °C for 20 min. This eliminates the internal stress of the fibers and avoids fiber breakage during subsequent low-concentration refining.

[0101] Low-concentration refining: The de-stressed pulp is diluted to a concentration of 3.5%, and a low-concentration disc refiner (Voith FibreFlow) is used with a gap of 0.06 mm, a rotational speed of 2000 rpm, and grinding for 20 min. This further refines the fibers and improves the water retention value.

[0102] Post-treatment and control of finished pulp: The pH of the pulp is adjusted to 8.8 to trigger the release of laccase from chitosan-alginate microcapsules, which catalyzes the oxidative cross-linking of lignin to improve the wet strength. Subsequently, the pulp is concentrated to 3.2% by a multi-disc concentrator, washed to remove residual enzymes and impurities, and then the headbox concentration is adjusted to 0.9% through a dilution system (Kadant dilution valve) in the pulp chest, and the pH is adjusted to 7.5 and directly used for papermaking on the paper machine.

[0103] 2. Effect evaluation:

[0104] (1) Energy consumption optimization: The power consumption per ton of pulp is 680 kW·h;

[0105] (2) Change in the crystalline region structure of fibers: The crystallinity measured by XRD decreases from 65% to 58%;

[0106] (3) Strength improvement: Ring crush index 8.5 kN / m, tensile index 70 N·m / g, wet strength 8.25 N·m / g;

[0107] (4) Change in fiber coarseness: The fiber coarseness decreases from 12 mg / m to 9.84 mg / m, a decrease of 18%;

[0108] (5) Environmental protection: The COD of the wastewater is 750 mg / L, and the degradation rate of p-toluenesulfonic acid after UV / H2O2 treatment is 95%;

[0109] (6) Drainability: Schopper-Riegler value 25 °SR.

[0110] Comparative example 1 Traditional enzyme treatment process

[0111] Raw material preparation: Poplar APMP pulp is selected as the wood pulp raw material (dry fiber content 15%), and screening and purification are carried out to remove impurities to ensure the uniformity and consistency of the fibers.

[0112] Enzyme compounding: Cellulase (30 U / g) and xylanase (18 U / g) are used.

[0113] Pretreatment: Mix the wood pulp raw material with water, adjust the pulp concentration to 8%, add sulfuric acid solution, adjust the pH of the reaction system to 5.0, and directly add two enzymes. Heat to 50°C and stir at 100 rpm for 50 min.

[0114] High-consistency refining: Concentrate the pulp to a concentration of 42%, use a high-consistency refiner (Andritz double-disc refiner), with a gap of 0.25 mm, a rotational speed of 3200 rpm, and grind for 10 min. This can reduce the power consumption per ton of pulp.

[0115] Defibrination treatment: Feed the pulp after high-consistency refining into a spiral defibrinator, adjust the pulp concentration to 12%, and perform defibrination at 55°C for 15 min.

[0116] Low-consistency refining: Dilute the defibrinated pulp to a concentration of 4%, use a low-consistency refiner (Voith FibreFlow) with a gap of 0.08 mm and a rotational speed of 2200 rpm, and grind for 20 min.

[0117] Post-treatment and control of finished pulp: The pulp is directly concentrated to 3.5% by a multi-disc concentrator. After washing to remove residual enzymes and impurities, adjust the headbox concentration to 1.0% through a dilution system in the filling pond (Kadant dilution valve), and directly use it for papermaking on the paper machine.

[0118] 2. Effect evaluation:

[0119] (1) Energy consumption defect: Power consumption per ton of pulp is 1150 kW·h;

[0120] (2) Change in the crystalline region structure of fibers: The crystallinity remains 62% as measured by XRD;

[0121] (3) Strength defect: Bursting index is 3.2 kPa·m 2 / g, tensile index is 56 N·m / g, and wet strength is 5.0 N·m / g;

[0122] (4) Fiber damage: Fiber coarseness decreases from 15 mg / m to 10.5 mg / m, with a decrease of 30%;

[0123] (5) Environmental protection issue: COD of wastewater is 1800 mg / L (including sulfate concentration of 1200 mg / L);

[0124] (6) Drainability: Schopper-Riegler value is 18°SR.

[0125] Single-stage enzyme treatment process of Comparative Example 2

[0126] 1. Preparation process

[0127] Raw material preparation: Select waste paper pulp (OCC, old corrugated cardboard boxes) as the wood pulp raw material (dry fiber content 18%), and conduct screening and purification to remove impurities to ensure the uniformity and consistency of the fibers.

[0128] Enzyme compounding: Pectinase (10U / g), xylanase (18U / g), and cellulase (28U / g).

[0129] Pretreatment: Mix the wood pulp raw material with water, adjust the pulp concentration to 6%, add a citric acid buffer solution, and directly add the three enzymes at the same time. Adjust the pH of the reaction system to 5.5. Heat to 45°C and stir at 300 rpm for 60 min.

[0130] High-concentration refining: Concentrate the pulp to a concentration of 40%, use a high-concentration disc refiner (Andritz double-disc refiner), with a gap of 0.3 mm, a rotation speed of 3000 rpm, and grind for 12 min.

[0131] Defibrination treatment: Feed the pulp after high-concentration refining into a spiral defibrinator, adjust the pulp concentration to 10%, and perform defibrination at 50°C for 20 min.

[0132] Low-concentration refining: Dilute the defibrinated pulp to a concentration of 3.5%, use a low-concentration disc refiner (Voith FibreFlow) with a gap of 0.06 mm and a rotation speed of 2000 rpm, and grind for 25 min.

[0133] Post-treatment and control of finished pulp: The pulp is directly concentrated to 3.2% by a multi-disc concentrator. After washing to remove residual enzymes and impurities, the headbox concentration is adjusted to 0.9% through a dilution system in the filling chest (Kadant dilution valve) and is directly used for papermaking on the paper machine.

[0134] 2. Effect evaluation:

[0135] (1) Energy consumption defect: Power consumption per ton of pulp is 950 kW·h;

[0136] (2) Change in the crystalline region structure of fibers: The crystallinity measured by XRD decreased from 65% to 60%;

[0137] (3) Strength defect: Ring crush index is 5.5 kN / m, tensile index is 58 N·m / g, and wet strength is 6.0 N·m / g;

[0138] (4) Fiber damage: Fiber coarseness decreased from 15 mg / m to 9.38 mg / m, only a 6% decrease;

[0139] (5) Environmental protection issue: COD in wastewater is 1500 mg / L;

[0140] (6) Drainability: Schopper-Riegler value is 20°SR.

[0141] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A segmented enzyme activated pulping method, characterized in that: The following steps are involved: Mix the wood pulp raw material with water, add p-toluenesulfonic acid, add the bio-enzyme complex system, stir at 100-300 rpm for 40-50 min at a pH of 4.8-5.0 and 45-50° C. to obtain a pretreated pulp; The pretreated pulp is heated to 55-60° C., concentrated to an absolute dry fiber concentration of 40-42%, with a grinding disc gap of 0.25-0.3 mm, and ground at 3000-3200 rpm for 8-10 minutes to obtain a high-concentration grinding pulp; The high-concentration grinding pulp is diluted to an absolute dry fiber concentration of 10%-12%, and delatched for 15-20 minutes at 50-55° C. to obtain delatched pulp; The delatent pulp is diluted to an absolute dry fiber concentration of 3.5%-5%, the grinding disc gap is 0.06-0.08 mm, and the grinding is performed at 2000-2200 rpm for 15-20 minutes to obtain a low-concentration grinding pulp; The pH of the low-concentration grinding slurry is adjusted to 8.5-8.8, cross-linked, concentrated to an absolute dry fiber concentration of 3.2%-3.5%, washed, diluted and adjusted to obtain a finished slurry for papermaking.

2. The pulping method according to claim 1, characterized in that: The mass of the p-toluenesulfonic acid is 0.4%-0.5% of the mass of the absolute dry fibers in the wood pulp raw material.

3. The pulping method according to claim 1, characterized in that: The biological enzyme compound system comprises 20-25 U / g of cellulase, 12-15 U / g of xylanase, 6-8 U / g of pectinase and 4-5 U / g of laccase.

4. The pulping method according to claim 3, characterized in that: The cellulase is encapsulated in a thermosensitive hydrogel; the xylanase and the pectinase are respectively encapsulated in low pH sensitive microcapsules; and the laccase is encapsulated in high pH sensitive microcapsules.

5. The pulping method according to claim 4, characterized in that: The temperature-sensitive hydrogel is poly-N-isopropylacrylamide; the low pH-sensitive microcapsule is polymethyl methacrylate; and the high pH-sensitive microcapsule is a chitosan-sodium alginate complex.

6. The pulping method according to claim 1, characterized in that: The dilution adjustment is to adjust the screen concentration of the washed pulp to 0.9%-1.0% through the pulping tank dilution system.

7. A finished pulp obtained according to the pulping method according to any one of claims 1 to 6.

8. Use of the finished pulp according to claim 7 in paper making.

9. The use according to claim 8, characterized in that The paper is high-strength packaging paper.

10. A high-strength packaging paper, characterized in that: The high-strength packaging paper is made from the finished pulp according to claim 7.

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