A method for preparing clean, natural-colored bamboo velvet pulp

Abstract

This invention discloses a method for preparing clean, unbleached bamboo fiber pulp. The method includes: loosening unbleached KP bamboo pulp boards; then feeding the pulp into a screening machine for classification, during which sodium hydroxide is added for swelling and softening; diluting the classified long-fiber pulp and performing flotation; washing and concentrating the flotated pulp in a vacuum washer; and finally forming unbleached bamboo fiber pulp boards. This invention does not use bleaching agents throughout the entire process, thus eliminating the generation of persistent organic pollutants at the source; through the effective combination of screening, classification, flotation, and washing processes, non-cellulose impurities such as hemicellulose and ash are thoroughly removed, purifying the fiber. This invention features a simple process, is clean and environmentally friendly, and produces products with excellent performance, showing promising prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of pulp and paper technology, specifically relating to a method for preparing clean, unbleached bamboo pulp, and more particularly to a method for preparing unbleached bamboo pulp using unbleached sulfate (KP) bamboo pulp board as raw material through processes such as decomposition, sieving, flotation, washing, and papermaking. Background Technology

[0002] Fluff pulp is a specialized pulp used to produce various absorbent hygiene products (such as feminine hygiene products, baby diapers, adult incontinence products, nursing pads, disposable nursing pads, etc.). Its characteristics include low burst strength, softness and comfort, elasticity, good water absorption and retention, high bulk, high single fiber strength, high purity, easy napping and disintegration, low dust content, and good antibacterial, antimicrobial, and anti-allergenic properties.

[0003] Currently, the main raw material for fluff pulp production is bleached wood pulp, with some use of bleached cotton linter pulp. Industry experts believe that coniferous wood is the best raw material for fluff pulp production. However, the production of wood and cotton linters is limited by factors such as planting area, growth cycle, ecological balance, production costs, and environmental protection. Furthermore, the supply of cotton and wood fiber raw materials cannot meet the raw material needs of related industries. Therefore, developing new natural cellulose fibers to compensate for the shortage of raw materials has become a very practical and urgent issue.

[0004] Bamboo resources are abundant, characterized by wide distribution, strong adaptability, rapid growth, early maturity, biodegradability, good antibacterial and bacteriostatic properties, and continuous utilization. The pulping and papermaking characteristics of bamboo fiber fall between those of softwood and hardwood fibers; the fibers are long and thin, with an average length of 1.5–2.0 mm. Based on these excellent characteristics, bamboo is inherently well-suited for producing fluff pulp.

[0005] Currently, commercially available fluff pulp is primarily bleached pulp, often using chlorine-based bleaching agents, and some even contain prohibited additives such as fluorescent whitening agents. This not only increases the amount of chemicals used in the bleaching stage and the investment in equipment, leading to decreased pulp yield and increased costs, but also makes the treatment of bleaching wastewater (containing large amounts of toxic chlorinated organic compounds such as chloroform, chlorophenols, chlorodioxins, and furans) difficult, causing harm to the ecological environment and organisms. Furthermore, during the fluffing process, the fibers undergo depolymerization and degradation during bleaching, resulting in a large amount of fluffing dust, which not only affects the working environment but also the physical and mental health of operators and the product qualification rate.

[0006] Existing technologies have attempted to prepare fluff pulp from unbleached bamboo pulp, but they generally suffer from the following problems: (1) complex process flow and low production efficiency; (2) large amount of chemicals used and insufficient environmental friendliness; (3) low product purity and incomplete removal of non-cellulose impurities such as cells, hemicellulose, and ash; (4) difficulty in achieving a balance between the comprehensive performance of the product (water absorption, fluffiness, antibacterial properties, etc.). Therefore, there is an urgent need to develop a method for preparing unbleached bamboo fiber fluff pulp that is simple in process flow, clean and environmentally friendly, and produces products with excellent performance. Summary of the Invention

[0007] The purpose of this invention is to address the technical problems existing in the production technology of bamboo pulp, such as reliance on imported raw materials, serious pollution during the bleaching process, excessive dust from bleached pulp, and difficulty in effectively removing non-cellulose impurities such as hemicellulose and ash from bamboo pulp, and to provide a method for preparing clean, natural-colored bamboo pulp.

[0008] This invention uses natural-colored KP bamboo pulp board as raw material and, through a process route of decomposition, screening, flotation, washing, and papermaking, effectively removes non-cellulose impurities and fully purifies the fibers, producing natural-colored bamboo wool pulp with low bursting strength, excellent liquid absorption, high bulkiness, easy napping and disintegration, low dust, and strong antibacterial and antimicrobial properties.

[0009] To achieve the above-mentioned objectives, the specific technical solution of this invention is as follows: A method for preparing clean, unbleached bamboo velvet pulp includes the following steps: (1) Decomposition: The natural KP bamboo pulp board is decomposed thoroughly and evenly to obtain pulp; this operation can preserve the original length of the fiber as much as possible and reduce the fiber from being cut.

[0010] (2) Screening machine: The slurry obtained in step (1) is fed into a Paul screening machine for classification to obtain long fiber slurry; the classification temperature is room temperature, the time is 2~20 min, and the pressure is normal; after classification, the mass concentration of the slurry is 0.5~2.5%; (3) Flotation: The long fiber slurry obtained in step (2) is diluted with water and then put into a flotation machine for flotation. The slurry mass concentration is controlled at 0.8~1.5%, the temperature is room temperature, and the time is 8~20 min. (4) Washing: The pulp obtained in step (3) is washed and concentrated by a vacuum washer, and the washing waste liquid is removed; (5) Papermaking: The pulp obtained in step (4) is put into the pulp board papermaking workshop. A bactericide is added to the pulp mixing tank and a debonding agent is added to the wire box. The rest of the papermaking process is similar to that of ordinary papermaking pulp board papermaking, and the pulp is made into natural bamboo wool pulp board.

[0011] In a preferred embodiment of this application, in step (1) of the method for preparing clean, unbleached bamboo fiber pulp, the equipment used for the decomposition is an intermittent medium-consistency or high-consistency hydraulic decomposition machine, and the resulting pulp is medium-consistency decomposition pulp or high-consistency decomposition pulp; the mass concentration of the medium-consistency decomposition pulp is 6%~12%, and the mass concentration of the high-consistency decomposition pulp is 12%~22%; the decomposition temperature is room temperature.

[0012] In a preferred embodiment of this application, in step (2) of the method for preparing clean, unbleached bamboo fiber pulp, sodium hydroxide is added to the pulp to be graded during the grading process; the amount of sodium hydroxide is 0.2-1.5% relative to the oven-dry pulp mass. More preferably, an appropriate amount of alkaline sodium hydroxide is added to the pulp to be graded, mainly because alkaline sodium hydroxide effectively swells and softens the fibers, which can change the morphology and flexibility of the fibers, facilitate the effective grading of long and short fibers, and help maintain the fiber length.

[0013] In a preferred embodiment of this application, in step (3) of the method for preparing clean, unbleached bamboo wool pulp, a collector is added during the flotation process; the collector is any one of fatty alcohol polyoxyethylene ether, ethylene oxide-propylene oxide copolymer or alkylphenol polyoxyethylene ether; the amount of collector is 0.1~1.5% relative to the dry pulp mass.

[0014] The flotation is used to remove hydrophobic non-cellulose impurities with particle diameters in the range of 10 to 250 μm from the fiber slurry.

[0015] The principle of flotation is based on the different wettability of components such as fibers, ash, organic solvent extracts, and short-chain cellulose. Hydrophobic particles agglomerate onto air bubbles due to the repulsive force of water, float to the liquid surface, and are then removed. A collector is preferably added during the flotation process. The collector can be any one of fatty alcohol polyoxyethylene ether, ethylene oxide-propylene oxide copolymer, or alkylphenol polyoxyethylene ether, and the amount used is 0.1~1.5% relative to the oven-dry pulp mass. The function of the collector is to agglomerate smaller impurities into larger agglomerates (particle diameter in the range of 10~250 μm) and impart a hydrophobic surface, facilitating their removal by flotation.

[0016] As a preferred embodiment of this application, in step (4) of the method for preparing a clean, natural bamboo wool pulp, the washing process involves using two vacuum washing machines to thoroughly wash and concentrate the pulp, thereby removing hydrophilic non-cellulose impurities with a particle diameter of less than 10 μm.

[0017] The combination of flotation and washing serves a complementary purpose—flotation removes hydrophobic non-cellulose impurities with particle diameters ranging from 10 to 250 μm, while washing removes hydrophilic non-cellulose impurities with particle diameters less than 10 μm. Washing is scheduled after flotation to remove any hydrophilic, smaller impurities that were not completely removed during the flotation stage, thus further purifying the fibers.

[0018] In a preferred embodiment of this application, in step (5) of the method for preparing clean, unbleached bamboo fiber pulp, the bactericide is an alkyl imidazoline quaternary ammonium salt (such as imidazoline quaternary ammonium salt of lauric acid, imidazoline quaternary ammonium salt of oleic acid, and imidazoline quaternary ammonium salt of castor oil, etc., which are specific fatty acid-type imidazoline quaternary ammonium salts, which are non-toxic, readily biodegradable, and have good water solubility); the amount of bactericide used is 0.1~1.5% relative to the oven-dry pulp mass. In this application, in addition to its bactericidal properties, the bactericide can also soften fibers, eliminate static electricity, has excellent emulsifying and dispersing properties, and is biodegradable.

[0019] In a preferred embodiment of this application, in step (5) of the method for preparing clean, unbleached bamboo fiber pulp, the unbonding agent is any one of sodium fatty alcohol polyoxyethylene ether sulfate, sodium alkyl diphenyl ether sulfonate, or polyethylene oxide; the amount of unbonding agent is 0.1-2.5% relative to the oven-dry pulp mass. The role of the unbonding agent in this application is to impart a charge to the fiber surface or adsorb onto the fiber surface to form a hydrated film, allowing the fibers to slide past each other without contacting each other, reducing inter-fiber hydrogen bonding, lowering the paper bonding strength, making it easier to disperse during subsequent napping processing, reducing fiberization energy consumption, and reducing dust.

[0020] This invention also protects a natural bamboo wool pulp prepared by any of the above methods or combinations of method steps.

[0021] As a preferred embodiment of this application, the unbleached bamboo wool pulp (treated pulp) obtained by the above method has a bursting strength of 590~750 kPa, a water absorption time of 4.5~8.0 s, a water absorption of 9.0~20.0 g / g, a dichloromethane extract content of 0.1~0.2%, a pentosan content of ≤5%, an ash content of ≤0.5%, and a dry bulk of 17~22 cm. 3 / g, heavy metal ion content arsenic (As) ≤0.1 mg·kg -1 Lead (Pb) ≤ 0.5 mg·kg -1 The levels of cadmium (Cd) and mercury (Hg) were not detected.

[0022] Compared with existing technologies, the beneficial effects of this invention are: 1. This invention does not use harmful chemical reagents such as bleaching agents and fluorescent whitening agents throughout the entire process, thus eliminating the generation of persistent organic pollutants (such as chloroform, chlorophenols, chlorodioxins and furans) at the source, maintaining the pure and natural color characteristics of fluff pulp, and is a healthy and environmentally friendly product.

[0023] 2. This invention utilizes abundant bamboo resources to replace wood and cotton linters in the production of high-value-added fluff pulp products. It solves the problem that the production of natural raw materials such as cotton linters and wood is limited by factors such as planting area, growth cycle, and ecological balance, thus enriching the raw material sources for fluff pulp production and reducing production costs.

[0024] 3. This invention effectively overcomes the inherent weaknesses of bamboo raw materials, such as high hemicellulose content, high ash content, high organic solvent extract, and many impurity cells, by using a combination of physical and chemical methods—retaining fiber length through loosening, screening and grading long and short fibers, and complementary flotation and washing for impurity removal—and significantly improves fiber purity and uniformity.

[0025] 4. The unbleached bamboo wool pulp (treated pulp) prepared by this invention has low burst strength (590~750 kPa), excellent liquid absorption (water absorption time 4.5~8.0 s, water absorption 9.0~20.0 g / g), high bulkiness (17~22 cm³ / g), dichloromethane extract 0.1~0.2%, pentosaccharide content ≤5%, ash content ≤0.5%, easy to fluff and dissociate, and less dust during fluffing, fully meeting the requirements of wool pulp products.

[0026] 5. The heavy metal ion content (arsenic (As)) of the unbleached bamboo wool pulp obtained by this invention is ≤0.1 mg·kg⁻¹. -1 Lead (Pb) ≤ 0.5 mg·kg -1 The levels of cadmium (Cd) and mercury (Hg) were not detected.

[0027] 6. The process of this invention is simple, has high production efficiency, low investment, and uses clean and environmentally friendly chemicals. It can achieve a coordinated balance between sustainable development and environmental protection in the paper industry, and has good economic, environmental and social benefits. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0030] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] In this invention, some conventional operating equipment, devices and components have been omitted or only briefly described.

[0032] Unless otherwise specified in the examples, the conditions shall be performed in accordance with the standard conditions or the conditions recommended by the manufacturer.

[0033] In this application, any percentage not marked indicates its weight percentage content.

[0034] In this application, all unspecified proportional relationships are mass ratios.

[0035] The trapping agent, ethylene oxide-propylene oxide copolymer, can be selected from Jiangsu Haian Petrochemical Plant (brand: Haishihua). Common PE3100, PE3500, PE3800, PE4200, and Shanghai Kaibite Chemical Co., Ltd.'s AEO-3, AEO-4, AEO-5, AEO-6, AEO-7 are all applicable to this application. The debonding agent, sodium fatty alcohol polyoxyethylene ether sulfate, can be selected from Bangpu Chemical (Shandong) BP-8001 or Kao (KAO) EMAL2227S.

[0036] Any steps or apparatus not described in detail are prior art or have no substantial impact on the effectiveness of this application.

[0037] Example 1: A method for preparing clean, unbleached bamboo velvet pulp includes the following steps: (1) Decomposition: Commercially available unbleached KP bamboo pulp board was decomposed using an intermittent medium-consistency hydraulic decomposer to obtain medium-consistency decomposed pulp with a concentration of 10% at room temperature. The commercially available unbleached KP bamboo pulp board has an α-cellulose content of 82-90%, an intrinsic viscosity of 900-1300 mL / g, a kappa value of 12-18, an ash content of 2-3%, a pentosan content of 8-14%, and a dichloromethane extract of approximately 1.5%.

[0038] (2) Screening machine: The slurry after disintegration is fed into a Paul screener for processing to obtain long fiber pulp. The grading temperature is room temperature, the time is 10 min, and the pressure is normal. After grading, the mass concentration of the pulp is 2.5%. Sodium hydroxide is added to the pulp that needs to be graded, and its dosage is 0.7% relative to the oven-dry pulp mass. (3) Flotation: The graded long pulp was diluted with water and then entered a flotation machine for flotation. Ethylene oxide-propylene oxide copolymer (Shanghai Kaibite Chemical Co., Ltd. AEO-3) was added as a collector. The flotation conditions were: pulp mass concentration 0.8%, temperature room temperature, time 20 min, and the amount of collector relative to the oven-dry pulp mass was 1.5%.

[0039] (4) Washing: The flotation pulp is washed and concentrated by two vacuum washing machines, and the washing waste liquid is discharged.

[0040] (5) Papermaking: The washed pulp enters the pulp board making workshop. The bactericide imidazoline quaternary ammonium salt of lauric acid (0.5% relative to the oven-dry pulp mass) is added to the pulp mixing tank. The debonding agent sodium fatty alcohol polyoxyethylene ether sulfate (Bangpu Chemical BP-8001, 2.5% relative to the oven-dry pulp mass) is added to the wire box. The pulp is then made into natural bamboo wool pulp board.

[0041] The performance indicators of the prepared unbleached bamboo fiber pulp are as follows: bursting strength 704 kPa, intrinsic viscosity 892 mL / g, dichloromethane extract 0.1%, water absorption time 5.5 s, water absorption 12.6 g / g, pentosaccharides 4.3%, ash content 0.4%, dry bulk 19 cm³ / g, average fiber length 1.85 mm, and heavy metal ion content of arsenic (As) 0.06 mg·kg⁻¹, while lead (Pb) 0.2 mg·kg⁻¹, cadmium (Cd) and mercury (Hg) were not detected.

[0042] Example 2: A method for preparing clean, unbleached bamboo velvet pulp, the preparation steps of which are the same as in Example 1, the only difference being: In step (2), the sieving and grading time is 2 min, and the pulp mass concentration is 2.0%; sodium hydroxide is added to the pulp that needs to be graded, and its dosage is 1.5% relative to the oven-dry pulp mass; In step (3), the flotation slurry concentration is 1.5%, the time is 8 min, and the collector is alkylphenol polyoxyethylene ether, with a dosage of 1.0%. In step (5), the amount of bactericide used is 0.1%, and the debonding agent is polyethylene oxide (CAS: 68441-17-8, catalog number: P823142), with a usage of 0.1%.

[0043] The performance indicators of the prepared unbleached bamboo fiber pulp are as follows: bursting strength 636 kPa, intrinsic viscosity 710 mL / g, dichloromethane extract 0.17%, water absorption time 7.8 s, water absorption 10.4 g / g, pentosaccharides 3.5%, ash content 0.5%, dry bulk 18 cm³ / g, average fiber length 2.15 mm, and heavy metal ion content of arsenic (As) 0.04 mg·kg⁻¹, while lead (Pb) 0.4 mg·kg⁻¹, cadmium (Cd) and mercury (Hg) were not detected.

[0044] Example 3: A method for preparing clean, unbleached bamboo velvet pulp, the preparation steps of which are the same as in Example 1, the only difference being: In step (2), the screening and grading time is 20 min, and the pulp mass concentration is 0.5%; sodium hydroxide is added to the pulp that needs to be graded, and its dosage is 0.2% relative to the oven-dry pulp mass; In step (3), the flotation slurry concentration is 1.2%, the time is 15 min, and the collector is fatty alcohol polyoxyethylene ether (Yangtze BASF AEO7) at a dosage of 0.1%. In step (5), the amount of bactericide used is 0.35%, and the amount of unbonding agent is sodium alkyl diphenyl ether sulfonate, which is 1.8%.

[0045] The performance indicators of the prepared unbleached bamboo fiber pulp are as follows: bursting strength 685 kPa, intrinsic viscosity 890 mL / g, dichloromethane extract 0.12%, water absorption time 4.7 s, water absorption 16.8 g / g, pentosaccharides 4.6%, ash content 0.3%, dry bulk 21 cm³ / g, average fiber length 2.08 mm, and heavy metal ion content of arsenic (As) 0.07 mg·kg⁻¹, while lead (Pb) 0.3 mg·kg⁻¹, cadmium (Cd) and mercury (Hg) were not detected.

[0046] Comparative Example 1: Comparison of alkali addition and non-alkali addition in screening and grading No alkali group: A method for preparing clean, natural bamboo wool pulp, the preparation steps are the same as in Example 1, the only difference being that sodium hydroxide is not added in step (2).

[0047] The performance indicators of the obtained unbleached bamboo wool pulp are as follows: bursting strength 976 kPa, water absorption time 8.5 s, water absorption 5.8 g / g, pentosan content 5.4%, ash content 0.51%, and dry bulkiness 15 cm. 3 / g, with an average fiber length of 1.67 mm.

[0048] Alkali-added group (Example 1): burst strength 704 kPa, intrinsic viscosity 892 mL / g, dichloromethane extract 0.1%, water absorption time 5.5 s, water absorption 12.6 g / g, pentosans 4.3%, ash content 0.4%, dry bulk 19 cm³ / g, average fiber length 1.85 mm.

[0049] Compared with the non-alkali group, the alkali-added group showed: burst strength decreased by 27.9%, water absorption time decreased by 3 seconds, water absorption increased by approximately 1.17 times, pentosans decreased by 20.4%, ash content decreased by 21.6%, dry bulk increased by 26.7%, and average fiber length increased by 10.8%. This indicates that alkali addition effectively segregates fibers of different lengths, purifies the fibers, reduces interfiber bonding, and improves bulk and water absorption.

[0050] Comparative Example 2: Comparison of flotation with and without flotation agents Group without trapping agent: A method for preparing clean, natural bamboo wool pulp, the preparation steps are the same as in Example 1, the only difference being that no trapping agent is added in step (3).

[0051] The performance indicators of the prepared unbleached bamboo fiber pulp are as follows: bursting strength 824 kPa·m² / g, water absorption time 6.3 s, water absorption 6.4 g / g, pentosans 5.0%, and ash content 0.6%.

[0052] The group with the trapping agent (Example 1) had a bursting strength of 704 kPa, a water absorption time of 5.5 s, a water absorption of 12.6 g / g, a pentosan content of 4.3%, and an ash content of 0.4%.

[0053] Compared with the group without a flotation agent, the group with the flotation agent showed a 14.6% decrease in burst strength, a nearly 1-second decrease in water absorption time, a 96.9% increase in water absorption, a 14.0% decrease in pentosans, and a 33.3% decrease in ash content. This indicates that the flotation agent effectively promoted the removal of hydrophobic impurities and improved the purity of the pulp.

[0054] Comparative Example 3: Comparison of front box with and without debonding agent Group without debonding agent: A method for preparing clean, natural bamboo wool pulp, the preparation steps are the same as in Example 1, the only difference being that no debonding agent is added in step (5).

[0055] The performance indicators of the prepared unbleached bamboo wool pulp are: bursting strength 989 kPa, dry bulkiness 11 cm³ / g.

[0056] Group with added unbonding agent (Example 1): burst strength 704 kPa, dry bulk 19 cm³ / g.

[0057] Compared with the group without the unbonding agent, the bursting strength of the group with the unbonding agent decreased by 28.8%, while the dry bulk increased by 72.7%. This indicates that the unbonding agent effectively reduced the hydrogen bonds between fibers and lowered the interfiber bonding force.

[0058] In summary, the clean preparation method of unbleached bamboo fluff pulp provided by this invention uses abundant bamboo as raw material. The process is simple, easy to operate, requires low investment, and uses clean and environmentally friendly chemicals. The resulting unbleached bamboo fluff pulp has characteristics such as low burst strength, excellent absorbency, high bulkiness, easy fluffing and disintegration, low dust, and strong antibacterial properties, fully meeting the requirements of fluff pulp products. It can be used in the production of absorbent sanitary products such as feminine hygiene products, baby diapers, adult incontinence products, nursing pads, and disposable nursing pads, and can also be used in the production of cellulose derivative products.

[0059] This invention fully utilizes abundant bamboo resources to replace imported wood pulp, effectively reducing production costs and alleviating the pressure of relying on imported raw materials for fluff pulp production. It offers significant economic, environmental, and social benefits and has broad prospects for industrial application. The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

[0060] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A method for preparing clean, unbleached bamboo velvet pulp, characterized in that, Includes the following steps: (1) Decomposition: The unbleached KP bamboo pulp board is thoroughly and evenly decomposed to obtain pulp; (2) Screening machine: The slurry obtained in step (1) is fed into a Paul screening machine for classification to obtain long fiber slurry; the classification temperature is room temperature, the time is 2~20 min, and the pressure is normal; after classification, the mass concentration of the slurry is 0.5~2.5%; (3) Flotation: The long fiber slurry obtained in step (2) is diluted with water and then put into a flotation machine for flotation. The slurry mass concentration is controlled at 0.8~1.5%, the temperature is room temperature, and the time is 8~20 min. (4) Washing: The pulp obtained in step (3) is washed and concentrated by a vacuum washer, and the washing waste liquid is removed; (5) Papermaking: The pulp obtained in step (4) is put into the pulp board papermaking workshop, bactericide is added to the pulp mixing tank, and debonding agent is added to the wire mesh box to form a natural bamboo wool pulp board.

2. The method for preparing clean, unbleached bamboo fiber pulp according to claim 1, characterized in that: The equipment used for decomposition in step (1) is an intermittent medium-consistency or high-consistency hydraulic decomposition machine, and the resulting pulp is medium-consistency decomposition pulp or high-consistency decomposition pulp; the mass concentration of medium-consistency decomposition pulp is 6%~12%, and the mass concentration of high-consistency decomposition pulp is 12%~22%; the decomposition temperature is room temperature.

3. The method for preparing clean, unbleached bamboo fiber pulp according to claim 1, characterized in that: In step (2), sodium hydroxide is added to the slurry that needs to be graded during the grading process; the amount of sodium hydroxide is 0.2 to 1.5% of the dry slurry mass.

4. The method for preparing clean, unbleached bamboo fiber pulp according to claim 1, characterized in that: In step (3), a collector is added during the flotation process; the collector is any one of fatty alcohol polyoxyethylene ether, ethylene oxide propylene oxide copolymer or alkylphenol polyoxyethylene ether; the amount of collector is 0.1~1.5% of the oven-dry pulp mass.

5. The method for preparing clean, unbleached bamboo fiber pulp according to claim 1, characterized in that: In step (3), the flotation is used to remove hydrophobic non-cellulose impurities with particle diameters in the range of 10 to 250 μm from the fiber slurry.

6. The method for preparing clean, unbleached bamboo fiber pulp according to claim 1, characterized in that: In step (4), two vacuum washing machines are used to thoroughly wash and concentrate the pulp to remove hydrophilic non-cellulose impurities with a particle diameter of less than 10 μm.

7. The method for preparing clean, unbleached bamboo fiber pulp according to claim 1, characterized in that: In step (5), the bactericide is an alkyl imidazoline quaternary ammonium salt; the amount of bactericide used is 0.1~1.5% relative to the dry pulp mass.

8. The method for preparing clean, unbleached bamboo fiber pulp according to claim 1, characterized in that: The unbonding agent mentioned in step (5) is any one of sodium fatty alcohol polyoxyethylene ether sulfate, sodium alkyl diphenyl ether sulfonate or polyethylene oxide; the amount of unbonding agent is 0.1~2.5% relative to the weight of oven-dry pulp.

9. A natural-colored bamboo wool pulp prepared by any one of claims 1 to 8.

10. The unbleached bamboo wool pulp according to claim 9, characterized in that: The unbleached bamboo fiber pulp has a bursting strength of 590~750 kPa, a water absorption time of 4.5~8.0 s, a water absorption capacity of 9.0~20.0 g / g, a dichloromethane extract content of 0.1~0.2%, a pentosaccharide content of ≤5%, an ash content of ≤0.5%, a dry bulk of 17~22 cm³ / g, and a heavy metal ion content of arsenic of ≤0.1 mg·kg⁻¹. -1 Lead ≤0.5 mg·kg -1 The levels of cadmium and mercury were not detected.