Chemical-mechanical pulp based on mixed wood and preparation process of chemical-mechanical pulp
By using a mixed wood pulping process, the problems of insufficient raw materials and declining poplar quality in the paper industry have been solved, and chemimechanical pulp with high brightness, high bulk, and high tensile index has been produced, achieving cost control and efficiency improvement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-06
- Publication Date
- 2026-04-10
AI Technical Summary
my country's paper industry suffers from a shortage of raw materials, with an abundance of grass-based materials and a scarcity of wood-based materials. This results in a limited variety of paper types and poor quality. Furthermore, rising poplar prices and declining cellulose quality increase usage costs. The traditional pulping model, which relies on a single raw material, leads to inefficiency.
Using mixed wood raw materials, including broad-leaved woods such as poplar, sycamore, and willow, and through processes such as screening, washing, pre-steaming, pre-impregnation, high-consistency pulping, and staged bleaching, the pulping parameters are optimized to achieve high cellulose and hemicellulose content, low impurities, and reduced consumption of bleaching chemicals and pulping energy consumption.
The prepared chemimechanical pulp has high whiteness, good bulk, and high tensile index, and its comprehensive performance is superior to that of traditional single poplar pulp. It breaks the traditional pulping mode that relies on a single raw material and achieves cost advantages and quality stability.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemimechanical pulp technology, specifically relating to a chemimechanical pulp based on mixed wood and its preparation process. Background Technology
[0002] The fundamental characteristics of plant fiber raw materials for pulp and paper production in my country are: insufficient raw materials, abundant grass-based raw materials, and scarce wood-based raw materials. As my country is a major agricultural country, 65% to 75% of its total pulp production is made from grass-based raw materials. However, paper produced from grass-based raw materials has limited variety and poor quality, resulting in small-scale paper mills and low-grade products. From a developmental perspective, using wood fiber as the primary raw material is an inevitable requirement of modern papermaking technology and economic laws, and represents the experience and development direction of the global papermaking industry. Today, the global papermaking industry has formed a high-speed, high-efficiency, high-quality, low-pollution, continuous, and automated production system; in terms of raw material structure, it has established a production system with wood as the main fiber raw material, accounting for 90%, while in my country it is less than 10%. Therefore, a crucial reason for the current level of production and technology in the global papermaking industry is the vigorous development of pulp and paper production using wood-based raw materials.
[0003] Papermaking wood raw materials mainly fall into two categories: hardwoods and softwoods. Hardwoods are white and have a high cellulose content, making them easy to cook, bleach, and pulp. They also impart excellent properties to paper, such as high bulk, high opacity, high uniformity, high softness, and high absorbency. Softwood fibers are typically longer, averaging over 2 mm in length. These long fibers help form the fiber network structure in paper, improving its strength and durability. Hardwoods are used far more extensively than softwoods in papermaking, and poplar is currently the most widely used hardwood raw material in chemimechanical pulping. However, with the continuous rise in poplar chip prices and increasingly fierce market competition, and because poplar chips often have insufficient growth years, the content and quality of cellulose and hemicellulose in the fiber raw material are reduced, while the content of alcohols, esters, and gums is higher, leading to a decline in quality and increased usage costs. Summary of the Invention
[0004] This invention provides a chemimechanical pulp based on mixed wood and its preparation process, which not only ensures the quality stability of the mixed pulp, but also maximizes the cost advantage of the new raw materials, breaking the traditional pulping mode that relies on a single raw material.
[0005] The technical solution of this invention is as follows: The first aspect discloses a process for preparing chemimechanical pulp based on mixed wood, including the following steps: screening and washing of raw materials, pre-steaming, pre-impregnation, reaction in a reaction chamber, high-consistency pulping, anti-latency treatment, screening and purification, concentration, bleaching, and storage and re-concentration, specifically: 1) Raw material screening and washing: Select broad-leaved wood with cellulose content ≥45%, lignin content ≤25%, and total cellulose and hemicellulose content exceeding 70% as raw material wood; wash the raw material wood with washing water temperature ≥92℃, and then pre-steam it with pre-steaming chamber temperature 125-130℃, pre-steaming chamber pressure 0.3-0.4MPa, and time 15-20min; 2) Pre-impregnation: Pre-impregnation temperature ≥85℃, NaOH dosage is 3-4% of the dry wood mass, bleaching agent dosage is 0.4-0.5% of the dry wood mass, stabilizer dosage is 0.4-0.5% of the dry wood mass, chelating agent dosage is 0.1-0.2% of the dry wood mass, reaction time is 30-60 min; 3) High-consistency refining: The pulp concentration at the feed is ≥40%, and the fiber bundle content of the pulp after high-consistency refining is ≤2.0%. A dual-disc refiner is used, and the refining gap is 0.2-0.3mm. 4) Bleaching: A staged bleaching process is adopted. In the first stage of bleaching, the dosage of NaOH is 1-2% of the oven-dry pulp mass, the dosage of bleaching agent is 2-3% of the oven-dry pulp mass, the dosage of stabilizer is 0.3-0.4% of the oven-dry pulp mass, and the dosage of chelating agent is 0.08-0.12% of the oven-dry pulp mass. The reaction time is 55-65 min, and the bleaching temperature is 70-80℃. In the second stage of bleaching, the dosage of NaOH is 0.4-0.6% of the oven-dry pulp mass, the dosage of bleaching agent is 1-2% of the oven-dry pulp mass, the dosage of stabilizer is 0.1-0.3% of the oven-dry pulp mass, and the dosage of chelating agent is 0.04-0.06% of the oven-dry pulp mass. The reaction time is 30-40 min, and the bleaching temperature is 60-70℃.
[0006] Preferably, the broad-leaved wood is poplar and at least one of London plane tree, eucalyptus, acacia and willow.
[0007] Preferably, the broadleaf timber comprises the following raw materials by weight percentage: 90% poplar and 10% London plane tree.
[0008] Preferably, the broadleaf timber comprises the following raw materials in weight percentages: 65% poplar, 10% eucalyptus, 10% acacia and 5% willow.
[0009] Preferably, the stabilizer is one or more of sodium silicate, magnesium sulfate, and sodium tripolyphosphate.
[0010] Preferably, the bleaching agent is one of H2O2, sodium dithionite, or formamidinium sulfinic acid.
[0011] Preferably, the chelating agent is diethyltriaminepentaacetic acid (DTPA).
[0012] Secondly, the process for preparing the chemimechanical pulp described above is disclosed.
[0013] Compared with the prior art, the present invention has the following advantages: 1. Innovation of low-consumption and high-efficiency pulping raw materials: Breaking through the limitations of traditional poplar raw materials, we have developed broad-leaved woods such as London plane trees and willows with cellulose and hemicellulose content of over 70% and low non-fiber impurities. Their high pre-bleaching whiteness characteristics reduce the consumption of bleaching chemicals, and their low lignin content reduces pulping energy consumption and grinding chip wear. This achieves synergistic optimization of "raw material characteristics - pulping efficiency - cost control" and solves the dual problems of declining poplar quality and rising costs.
[0014] 2. Precise Raw Material Matching Process: An innovative approach is adopted, combining poplar with new raw materials such as London plane trees and willow in batches. Through a combination of pre-impregnation (≥85℃), high-consistency pulping (≥40% concentration), and segmented bleaching (high-consistency bleaching to medium-consistency bleaching), process parameters are dynamically adjusted according to the raw material ratios to achieve precise matching of different raw material characteristics. This process ensures the quality stability of the mixed pulp while maximizing the cost advantages of the new raw materials, breaking away from the traditional pulping model that relies on a single raw material.
[0015] 3. The mechanical pulp prepared by this invention has a brightness of 80% ISO or higher and a bulk of ≥2.0 cm. 3 / g, dust level ≤20mm 2 / m 2 With a tensile index ≥40 N·m / g, its overall performance is superior to that of traditional single poplar wood pulp. Detailed Implementation
[0016] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of this invention.
[0017] Example 1 The chemimechanical pulp preparation process based on mixed wood includes the following steps: raw material screening and washing, pre-steaming, pre-impregnation, reaction chamber reaction, high-consistency pulping, anti-latency treatment, screening and purification, concentration, bleaching, and storage and re-concentration. 1) Raw material screening and washing: Select broad-leaved wood with a cellulose content of 50%, a lignin content of 24%, and a total cellulose and hemicellulose content of 72%, with a mass percentage of 90% poplar and 10% London plane tree as raw wood; wash the raw wood with washing water at 92℃, and then pre-steam it at 125℃ in the pre-steaming chamber at a pressure of 0.3MPa for 20 minutes; 2) Pre-impregnation: Pre-impregnation temperature 90℃, NaOH dosage is 4% of the dry wood mass, bleaching agent H2O2 dosage is 0.5% of the dry wood mass, stabilizer magnesium sulfate dosage is 0.4% of the dry wood mass, chelating agent diethyltriaminepentaacetic acid (DTPA) dosage is 0.15% of the dry wood mass, reaction time 50 min; 3) High-consistency pulping: The pulp concentration at the start of the pulping process is 40%, and the fiber bundle content of the pulp after high-consistency pulping is 2%. A dual-disc pulping machine is used, and the pulping gap is 0.3 mm. 4) Bleaching: A staged bleaching process is adopted. In the first stage of bleaching, the dosage of NaOH is 2% of the oven-dry pulp mass, the dosage of bleaching agent H2O2 is 3% of the oven-dry pulp mass, the dosage of stabilizer magnesium sulfate is 0.4% of the oven-dry pulp mass, and the dosage of chelating agent diethyltriaminepentaacetic acid (DTPA) is 0.12% of the oven-dry pulp mass. The reaction time is 60 min, and the bleaching temperature is 80℃. In the second stage of bleaching, the dosage of NaOH is 0.6% of the oven-dry pulp mass, the dosage of bleaching agent H2O2 is 1% of the oven-dry pulp mass, the dosage of stabilizer is 0.3% of the oven-dry pulp mass, and the dosage of chelating agent diethyltriaminepentaacetic acid (DTPA) is 0.06% of the oven-dry pulp mass. The reaction time is 35 min, and the bleaching temperature is 70℃.
[0018] Example 2 The chemimechanical pulp preparation process based on mixed wood includes the following steps: raw material screening and washing, pre-steaming, pre-impregnation, reaction chamber reaction, high-consistency pulping, anti-latency treatment, screening and purification, concentration, bleaching, and storage and re-concentration. 1) Raw material screening and washing: Select broadleaf wood with a cellulose content of 48%, a lignin content of 22%, and a total cellulose and hemicellulose content of 71%, and select poplar, eucalyptus, acacia and willow wood by weight percentage of 65%, eucalyptus, acacia and willow as raw wood; wash the raw wood with washing water temperature of 95℃, and then pre-steam it with a pre-steaming chamber temperature of 128℃, a pre-steaming chamber pressure of 0.4MPa and a time of 15min; 2) Pre-impregnation: Pre-impregnation temperature 88℃, NaOH dosage is 3% of the dry wood mass, bleaching agent H2O2 dosage is 0.4% of the dry wood mass, stabilizer magnesium sulfate dosage is 0.5% of the dry wood mass, chelating agent diethyltriaminepentaacetic acid (DTPA) dosage is 0.2% of the dry wood mass, reaction time 60 min; 3) High-consistency pulping: The pulp concentration at the feed is 42%, and the fiber bundle content of the pulp after high-consistency pulping is 1.8%. A dual-disc pulper is used with a pulping gap of 0.2 mm. 4) Bleaching: A staged bleaching process is adopted. In the first stage of bleaching, the dosage of NaOH is 1.5% of the oven-dry pulp mass, the dosage of bleaching agent H2O2 is 2.5% of the oven-dry pulp mass, the dosage of stabilizer magnesium sulfate is 0.3% of the oven-dry pulp mass, and the dosage of chelating agent diethyltriaminepentaacetic acid (DTPA) is 0.10% of the oven-dry pulp mass. The reaction time is 65 min, and the bleaching temperature is 75℃. In the second stage of bleaching, the dosage of NaOH is 0.6% of the oven-dry pulp mass, the dosage of bleaching agent H2O2 is 1.5% of the oven-dry pulp mass, the dosage of stabilizer is 0.2% of the oven-dry pulp mass, and the dosage of chelating agent diethyltriaminepentaacetic acid (DTPA) is 0.05% of the oven-dry pulp mass. The reaction time is 40 min, and the bleaching temperature is 65℃.
[0019] Comparative Example 1 The raw material used is 100% poplar wood, and the remaining preparation methods and steps are the same as in Example 1.
[0020] Comparative Example 2 The raw materials used are 50% poplar and 50% eucalyptus, and the remaining preparation methods and steps are the same as in Example 1.
[0021] Comparative Example 3 In step 2), the pre-impregnation temperature is adjusted to 80°C, and the remaining preparation methods and steps are the same as in Example 1.
[0022] Comparative Example 4 In step 3), the pulp concentration is 38%, and the remaining preparation methods and steps are the same as in Example 1.
[0023] Comparative Example 5 In step 4), a single-stage bleaching process is used, with the dosage being the sum of the dosages in the two stages in the example, and the time also being the sum of the two stages.
[0024] The chemical mechanical pulps prepared in the above embodiments and comparative proportions were subjected to relevant performance tests, as shown in Table 1.
[0025] The chemimechanical pulp prepared in the above examples and comparative examples has a papermaking yield of 60 g / m³ under standard industry conditions. 2 The pulp was equilibrated under standard temperature and humidity conditions, and its whiteness, bulk, dust content and tensile index were tested. The results are shown in Table 1.
[0026] Table 1
[0027] As shown in Table 1, the chemimechanical pulps prepared using the mixed wood raw materials and optimized process described in this invention in Examples 1 and 2 exhibit excellent performance in terms of whiteness, bulk, low dust content, and strength (tensile index). Specific details are as follows: In Comparative Example 1, all properties were slightly lower than those in Example 1. This invention not only solves the problem of the lack of single poplar raw materials, but also produces pulp that is superior to pure poplar in terms of whiteness and pine height.
[0028] In Comparative Example 2, eucalyptus fibers were shorter and had a denser lignin structure. When mixed with poplar, the proportions were not optimized, resulting in decreased inter-fiber bonding and poor pulp uniformity, thus affecting paper strength and optical properties. Furthermore, eucalyptus has a high extractive content; if not sufficiently removed during pretreatment, it can lead to increased chemical consumption and staining during bleaching, resulting in decreased whiteness and increased dustiness.
[0029] In Comparative Example 3, the pre-impregnation temperature was reduced to below 85°C, which led to a decrease in the penetration and reaction efficiency of chemicals (NaOH, H2O2, etc.) on the wood chips. In particular, the softening and partial removal of hemicellulose and lignin were insufficient, resulting in increased energy consumption in subsequent pulping, rough fiber separation, and ultimately affecting the bulk and strength of the pulp.
[0030] In Comparative Example 4, insufficient pulp concentration led to reduced inter-fiber friction, incomplete fiber bundle separation, and insufficient retention of long fibers, thereby reducing the bulk and tensile index of the paper.
[0031] In Comparative Example 5, the bleaching efficiency was low and the drug utilization rate was poor, resulting in a significant reduction in whiteness and strength.
[0032] In summary, this invention achieves a significant improvement in the overall performance of chemimechanical pulp by combining optimized raw material selection, precise control of process parameters, and segmented bleaching process, and has obvious industrial application value.
Claims
1. A process for preparing chemimechanical pulp based on mixed wood, comprising the following steps: screening and washing of raw materials, pre-steaming, pre-impregnation, reaction in a reaction chamber, high-consistency refining, anti-flammability, screening and purification, concentration, bleaching, and storage and re-concentration, characterized in that, 1) Raw material screening and washing: Select broad-leaved wood with cellulose content ≥45%, lignin content ≤25%, and total cellulose and hemicellulose content exceeding 70% as raw material wood; wash the raw material wood with washing water temperature ≥92℃, and then pre-steam it with pre-steaming chamber temperature 125-130℃, pre-steaming chamber pressure 0.3-0.4MPa, and time 15-20min; 2) Pre-impregnation: Pre-impregnation temperature ≥85℃, NaOH dosage is 3-4% of the dry wood mass, bleaching agent dosage is 0.4-0.5% of the dry wood mass, stabilizer dosage is 0.4-0.5% of the dry wood mass, chelating agent dosage is 0.1-0.2% of the dry wood mass, reaction time is 30-60 min; 3) High-consistency refining: The pulp concentration at the feed is ≥40%, and the fiber bundle content of the pulp after high-consistency refining is ≤2.0%. A dual-disc refiner is used, and the refining gap is 0.2-0.3mm. 4) Bleaching: A staged bleaching process is adopted. In the first stage of bleaching, the dosage of NaOH is 1-2% of the oven-dry pulp mass, the dosage of bleaching agent is 2-3% of the oven-dry pulp mass, the dosage of stabilizer is 0.3-0.4% of the oven-dry pulp mass, and the dosage of chelating agent is 0.08-0.12% of the oven-dry pulp mass. The reaction time is 55-65 min, and the bleaching temperature is 70-80℃. In the second stage of bleaching, the dosage of NaOH is 0.4-0.6% of the oven-dry pulp mass, the dosage of bleaching agent is 1-2% of the oven-dry pulp mass, the dosage of stabilizer is 0.1-0.3% of the oven-dry pulp mass, and the dosage of chelating agent is 0.04-0.06% of the oven-dry pulp mass. The reaction time is 30-40 min, and the bleaching temperature is 60-70℃.
2. The chemimechanical pulp preparation process based on mixed wood as described in claim 1, characterized in that, Broadleaf timber includes poplar and at least one of London plane tree, eucalyptus, acacia and willow.
3. The chemimechanical pulp preparation process based on mixed wood as described in claim 2, characterized in that, The broadleaf timber comprises the following raw materials by weight percentage: 90% poplar and 10% London plane tree.
4. The chemimechanical pulp preparation process based on mixed wood as described in claim 2, characterized in that, The broadleaf timber comprises the following raw materials in weight percentages: 65% poplar, 10% eucalyptus, 10% acacia and 5% willow.
5. The chemimechanical pulp preparation process based on mixed wood as described in claim 1, characterized in that, The stabilizer is one or more of sodium silicate, magnesium sulfate, and sodium tripolyphosphate.
6. The chemimechanical pulp preparation process based on mixed wood as described in claim 1, characterized in that, The bleaching agent is one of H2O2, sodium dithionite, or formamidinium sulfinic acid.
7. The chemimechanical pulp preparation process based on mixed wood as described in claim 1, characterized in that, The chelating agent is diethyltriaminepentaacetic acid (DTPA).
8. The chemimechanical pulp prepared by the process according to any one of claims 1-7.