A method for pulping based on coconut shell raw material and its application in corrugated packaging material production

Abstract

This invention belongs to the field of comprehensive utilization of biomass resources and pulping and papermaking technology, and relates to a pulping method based on coconut shell raw materials and its application in the production of corrugated packaging materials. The method includes: processing coconut shell raw materials through a twin-screw extrusion and kneading process to obtain a mixture; obtaining coconut fiber components through multi-stage sieving; subjecting the coconut fibers to hot water or alkaline cooking; grinding with a high-consistency disc mill or defragmenting with a fiber delamination machine, and sieving to obtain coconut pulp. The obtained coconut pulp is mixed with recycled fiber pulp, chemical additives are added, and the mixture is then used to produce corrugated base paper or boxboard. This invention achieves efficient and clean separation of coconut shell fibers through a combination of twin-screw extrusion and kneading + pre-hydrolysis / alkaline cooking + high-consistency refining / defragmentation processes, resulting in high pulp yield, good fiber morphology, and a maximum ring crush index of 8.3 N·m / g and a maximum bursting index of 3.4 kPa·m. 2 / g, opening up a new source of low-cost, renewable fiber raw materials for the pulp and paper industry.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization of biomass resources and pulping and papermaking technology, specifically relating to a pulping method based on coconut shell raw materials and its application in the production of corrugated packaging materials. Background Technology

[0002] Corrugated materials (corrugated base paper, linerboard) are the basic raw materials for manufacturing packaging products such as cartons. Currently, the production of corrugated materials mainly relies on wood fibers (including recycled waste paper pulp and virgin wood pulp). The production capacity of virgin wood pulp suffers from structural deficiencies and a high dependence on imports, resulting in high production costs. At the same time, the cost of obtaining high-quality recycled fiber raw materials in the paper industry is constantly rising, highlighting the increasing pressure on raw material security and cost control. Furthermore, the quality of recycled waste paper is inconsistent, and its utilization rate is low. Fiber quality deteriorates due to repeated recycling, leading to unstable product quality and increased use of chemical auxiliaries and water treatment costs. Therefore, developing and utilizing widely available, renewable, and low-cost virgin fiber raw materials has become an important direction for the pulp and paper industry, especially in the packaging materials sector, to achieve sustainable development.

[0003] Many leading companies have invested in chemical pulp projects in hopes of obtaining high-quality, low-cost chemical wood pulp. However, the so-called "low cost" is often based on large-scale production and stable timber resource prices, and actual production still faces multiple constraints. Over-reliance on timber resources leads to multiple pressures, including sustainable management of forest resources, tight raw material supply, and cost fluctuations. The production of chemical wood pulp involves large amounts of chemicals, high energy consumption, and heavy wastewater treatment loads, with continuously rising environmental protection investments further increasing overall production costs. Therefore, actively developing and utilizing non-wood fiber raw materials and developing high-yield, low-pollution pulping technologies adapted to their characteristics are of vital importance for alleviating the raw material shortage in the paper industry, ensuring the security and stability of the industrial supply chain, and reducing dependence on imported resources.

[0004] Coconut shells, as a large-volume agricultural processing residue, possess robust and resilient fibers, making them a highly promising non-wood fiber resource. Some studies have attempted to apply coconut shell fibers to composite materials or papermaking, but traditional processing methods have significant limitations: for example, while all-chemical pulping yields high-quality pulp, it consumes large amounts of chemicals, has high energy consumption, and generates heavy wastewater pollution; simple mechanical grinding methods are insufficient to effectively separate the tightly bound fiber bundles from impurities such as lignin and hemicellulose in coconut shells, resulting in coarse, hard fibers with uneven length distribution, poor papermaking performance, and difficulty in water filtration, failing to meet the requirements of high-speed paper machines for pulp water filtration and paper strength in corrugated material production.

[0005] Therefore, there is a need to develop a comprehensive process that can efficiently, cleanly, and economically convert coconut shell waste into fiber pulp suitable for industrial production of corrugated materials. This process must ensure a high fiber yield while achieving appropriate separation and softening of the coconut shell fibers, so that they retain sufficient inherent strength and are well-compatible with existing mainstream waste paper pulp, ultimately producing corrugated material products that meet performance standards and are cost-effective. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a pulping method based on coconut shell raw materials and its application in the production of corrugated packaging materials. The method employs a combined process including twin-screw extrusion and kneading, pre-hydrolysis / alkali cooking, and high-consistency grinding / delamination to achieve appropriate separation and softening of coconut shell fibers. This overcomes the dual defects of existing technologies, such as heavy pollution and high energy consumption in all-chemical pulping, and coarse and hard fibers and poor paper performance in simple mechanical grinding.

[0007] The technical solution of this invention is: The first aspect of this invention discloses a pulping method based on coconut shell raw materials, comprising the following steps: (1) Pretreatment: After adjusting the coconut shell raw material to a suitable moisture content, it is processed by a twin-screw extruder to obtain a mixture. (2) Screening: The mixture is screened to separate the coconut fiber component and the usable sheet coconut coir tissue; (3) Cooking: The coconut fiber components obtained in step (2) are subjected to hot water cooking or alkaline cooking to obtain the cooking material; (4) Grinding: The cooked material is ground using a high-concentration disc mill or decomposed using a fiber decomposition machine, and then screened to obtain coconut pulp.

[0008] Preferably, the coconut shell raw material is selected from at least one of coconut shell pericarp and coconut fiber.

[0009] The coconut shell pericarp mentioned is either the pericarp of a young coconut or the pericarp of a mature dried coconut. The pericarp of a mature dried coconut is the lignified coconut shell after the inner pericarp of a mature coconut has been removed, retaining the fibrous layer of the pericarp. When using it, the coconut shell pericarp needs to be cut into pieces with a side length of 3-4 cm using a cutting machine. Impurities are removed by spraying and the solution is concentrated. The pieces of coconut shell are then washed with a mist of hot water to remove dust, debris, sand, and other impurities. The moisture content of the coconut shell is then adjusted to 65%-80%.

[0010] Preferably, the purpose of using a twin-screw extruder to process coconut shell raw materials in step (1) above is to use two parallel, counter-rotating, and meshing screw elements to dynamically extrude the conveyed material. The material is extruded and kneaded under high concentration and high pressure conditions, and the coconut shell structure is broken and disintegrated to form a mixture of coconut coir and partially disintegrated coconut fibers, which are then further broken down and separated into fiber bundles or single fibers. More preferably, the material dryness at the feed inlet of the extruder is 20%-35%, the pressure in the extrusion zone is 10-25MPa, the screw speed is 300-420rpm, and the dryness at the discharge outlet is 25%-40%.

[0011] Preferably, the screening in step (2) above includes multi-level screening, which includes: 1) Use a sieve with an aperture of ≤1mm to screen the mixed materials. The retained material is coconut fiber, and the undersize material is shredded and torn coconut fiber and coconut coir. The sieve type is conical or stepped structure. 2) Continue sieving the material undersize from step 1) using a 0.5-0.6mm mesh sieve. The retained material consists of radially cut and axially torn bundles of coconut fiber. 3) Continue sieving the material from step 2) using a 0.10-0.35mm sieve. The retained material consists of partially broken coconut fiber and large-flake coconut coir components. 4) Add water to the sieved material from step 3) to concentrate it to 1.0%, and use a 0.10-0.35mm sieve to screen it, retaining a small amount of broken coconut fiber and most of the coconut coir fragments.

[0012] Preferably, in step (3), when hot water cooking is used, the fiber component is immersed in hot water at 85-90℃ for 20-60 minutes, with an immersion concentration of 3%-8%. After immersion, it is dewatered using a two-roll extruder to a solid content of 15%-20%, and then heated to 140-170℃ and kept at that temperature for 15-60 minutes. The dewatering equipment is a high-throughput, continuous-production two-roll extrusion filter, and the concentration of the material after dewatering is controlled at 25-35%. When using alkaline cooking, add NaOH solution during the twin-screw extrusion and kneading process. The amount of NaOH used is 3%-22% of the dry material mass. Adjust the liquid ratio to 1:4-1:7 during cooking and heat to 130-160℃ for 30-120 minutes.

[0013] Preferably, the pulp concentration of the high-consistency disc mill described in step (4) above is 15%-25%, the disc-mill gap is 0.3mm-0.5mm, and the disc-mill tooth structure is preferably a series of slurry fins to effectively retain fiber length. The disc should be designed with two grinding zones from the center to the outer diameter, serving the purposes of slurrying and refining respectively. The grinding grooves in the refining zone should preferably be semi-closed. Typical disc types include... Figure 1As shown; after grinding, the pulp is screened using a slotted sieve with a size of 0.10mm-0.25mm. The unscreened pulp is thickened to 5%-15% and then ground again. The ground pulp is then mixed with the screened pulp to obtain coconut pulp.

[0014] The second aspect of the present invention discloses a method for preparing coconut pulp using the above-described preparation method.

[0015] The second aspect of this invention discloses the application of the aforementioned coconut pulp in the fabrication of corrugated packaging materials.

[0016] Preferably, the coconut pulp in a mass ratio of 1:9 to 7:3 is mixed with recycled fiber pulp, chemical additives are added, and corrugated packaging material is obtained by papermaking. The corrugated packaging material includes corrugated base paper or boxboard. The recycled fiber pulp is obtained by decontamination, purification, screening and pulping of old boxboard or carton processing trimmings, with a freeness of 32-45°SR.

[0017] Preferably, the chemical excipients include one or more of cationic starch, AKD (alkyl ketene dimer) or ASA (alkenyl succinic anhydride), polyacrylamide (PAM / CPAM), and bentonite; the degree of substitution (DS) of the cationic starch is 0.01-0.15, and the dosage is 0.1%-1.5% of the oven-dry fiber mass; the dosage of AKD or ASA is 0.1%-0.5% of the oven-dry fiber mass; and the dosage of polyacrylamide is 0.01%-0.05% of the oven-dry fiber mass. The above chemical excipients are mainly used as sizing agents, reinforcing agents, retention aids, and filtration aids. For specific addition methods and dosages, please refer to the examples.

[0018] The advantages and beneficial effects of this invention are: (1) This invention adopts a combined pulping process of "twin-screw extrusion and kneading + pre-hydrolysis / alkali cooking + high-consistency refining / de-scraping". Twin-screw extrusion and kneading is used as the core pretreatment method. It utilizes high concentration, high pressure and strong shearing to efficiently dissociate the pericarp in coconut shell, breaking through the limitations of low efficiency of traditional simple cutting and soaking pretreatment. Subsequently, the fiber components and coconut coir components are separated step by step through a four-stage screening system, so that materials of different forms can be classified and utilized. In the cooking stage, hot water cooking or alkaline cooking can be selected according to the target pulp performance requirements. The former is more environmentally friendly, and the latter is more conducive to obtaining high-strength pulp. Finally, high-consistency disc milling is used for grinding, combined with sieve screening and regrinding process, so as to achieve uniform pulp quality while retaining fiber length to the maximum extent. This combined process organically integrates physical kneading, chemical pretreatment and mechanical grinding, overcoming the dual defects of heavy pollution and high energy consumption of all-chemical pulping and coarse and hard fibers and poor paper performance of simple mechanical grinding.

[0019] (2) The coconut pulp prepared by this invention has excellent fiber morphology and physicochemical properties. It has good adjustability to adapt to the papermaking requirements of different paper types. When this coconut pulp is mixed with recycled fiber pulp, it exhibits good compatibility and papermaking performance, and can meet the comprehensive requirements of pulp water permeability and paper strength for corrugated base paper and boxboard production.

[0020] (3) The density of the corrugated base paper and boxboard produced by this invention can reach 0.58 to 0.78 g / cm. 3 The ring crush index reaches a maximum of 8.3 N·m / g, and the burst strength index reaches a maximum of 3.4 kPa·m. 2 / g, with a maximum folding endurance of 48 times, and water absorption controlled between 48 and 63 g / m². 2 This invention employs a clean production process combining physical kneading and low-alkali cooking, resulting in low chemical consumption and minimal wastewater treatment load. Using coconut shells, a high-volume agricultural processing residue, as raw material, it replaces imported wood pulp and high-quality waste paper pulp, effectively alleviating the paper industry's over-reliance on wood fiber and the problem of waste paper pulp quality degradation. It opens up a new source of low-cost, renewable fiber raw materials for the pulp and paper industry, demonstrating significant resource recycling value and promising prospects for industrialization. Attached Figure Description

[0021] Figure 1 This is a diagram showing the tooth profile of the two grinding zones of the high-concentration disc mill used in this invention. Figure 2 The image shows the cell microstructure obtained by washing the coconut pulp from Example 1 using a 200-mesh pulp bag.

[0022] Figure 3 Microstructure of the coconut pulp prepared in Example 7; Figure 4 The image shows the microscopic morphology of coconut fibers and some miscellaneous cells in the coconut pulp prepared in Example 8. Detailed Implementation

[0023] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0024] Example 1 A pulping method based on coconut shell raw materials includes the following steps: (1) Coconut shell pretreatment: The inner husk of a young coconut (with the inner shell removed) has a moisture content of 78%. It is cut into pieces with a side length of about 3-4 cm and sieved through a 5-mesh screen to remove debris, sand, and other small impurities. An 80 mm diameter screw is selected and the speed is adjusted to 360 rpm. The pieces of young coconut husk are directly fed into the feed inlet of a twin-screw extruder. The material is extruded and conveyed to the twin-screw working area by the feed screw, and then sequentially enters three sets of conveying and extrusion kneading zones. The pressure in the extrusion zone is 15 MPa. The material is discharged from the outlet with a dryness of 33%, resulting in a mixture of coconut coir and partially disintegrated coconut shreds.

[0025] (2) Screening the mixture: 1) Add water to the above mixture to concentrate it to 2.5%, and sieve it using a 0.8 mm sieve. The retained material is the radially cut coconut fiber. 2) Use a 0.5mm mesh sieve to screen the material undersize from step 1), and retain the radially cut and axially torn coconut fiber bundles; 3) The material undersize from step 2) is screened using a 0.35mm sieve, and the retained material consists of partially broken coconut fiber and large-structure coconut coir components; 4) Add water to the sieve material from step 3) to concentrate it to 1.0%, and use a 0.10mm sieve to screen it. The retained material is a small amount of broken coconut fiber and most of the coconut coir fragments.

[0026] (3) Soaking and steaming: The retentates from steps (2) 1), 2), and 3) are combined and homogenized. Then, they are soaked in hot water at 90°C for 30 minutes with a soaking concentration of 5%. After soaking, the soaked substrate is dehydrated to a solid content of 15% using a two-roller extruder. Then, the temperature is raised to 150°C and kept at that temperature for 30 minutes to obtain the cooking material. (4) Grinding: A high-concentration disc mill is used (the tooth profile structure of the two grinding zones of the disc in a high-concentration disc mill is shown in the figure). Figure 1 As shown, the cooked feed was ground into a pulp with a pulp concentration of 25% and a disc mill gap of 0.30 mm. The pulp was then screened using a 0.15 mm slotted sieve. The unscreened pulp was concentrated to 12% and then ground again and mixed with the screened pulp to obtain coconut pulp.

[0027] Figure 2 The microscopic morphology of the cells obtained by washing the coconut fiber pulp prepared in Example 1 with a 200-mesh pulp bag shows that the coconut fiber in the coconut shell has been dissociated, and some fibers even retain a large aspect ratio. At the same time, a large number of large tissue sheet cells in the coconut coir are still retained in the pulp.

[0028] The coconut pulp prepared in Example 1 is used to make corrugated base paper, comprising: 1) Take Class A waste corrugated cardboard as raw material, remove impurities such as tape and nails, and crush it into paper scraps of about 5×5 cm. Then, use a hydraulic pulper to break it down into dispersed recycled fiber pulp.

[0029] 2) Screen the above recycled fiber pulp using a 0.35mm sieve to remove smaller impurities (unshredded paper, shredded tape, plastic, and sand, etc.). Use a Walley beater to adjust the freeness of the recycled fiber pulp to 35. 0 SR; 3) Mix coconut fiber pulp and recycled fiber pulp at a mass ratio of 3:7, add water to thicken to 0.7%, and then add the following chemical additives in sequence: add a mixture of pre-emulsified cationic starch and AKD, where the amount of pre-emulsified cationic starch is 0.5% (degree of substitution DS is 0.15), and the amount of AKD is 0.3% of the oven-dry fiber mass. Then turn on the homogenizer and stir for 120s at a stirring speed of 150 rpm; then add CPAM emulsion (solid content 38%, molecular weight 6.2 million, charge density 3.4 mmol / g), the amount of which is 0.03% of the oven-dry fiber mass, and adjust the speed to 180 rpm and stir for 30s. The prepared pulp is then sheeted using the rapid Kaiser method, with a sheeting quantity of 90 g / m³. 2 After drying for 10 minutes, a corrugated base paper sample was obtained and placed in a constant temperature and humidity environment (23±1℃, 50±2% RH) for testing.

[0030] The coconut fiber pulp prepared in Example 1 was light brown, with a yield of 89.2% after cooking and grinding. The pulp ash content was 1.31%, the color was L=70.8, a=6.3, b=21.4, the kappa value was 103, the average fiber length was 0.543 mm, the width was 32.1 μm, the aspect ratio was 17, and the freeness was 216 mL. The physical properties of the corrugated base paper sample were tested, and the density was 0.62 g / cm³. 3 The ring crush index is 6.5 N·m / g, and the burst strength index is 1.7 kPa·m. 2 / g, folding endurance 26 times, water absorption Cobb 60s 59 g / m 2 .

[0031] Example 2 A pulping method based on coconut shell raw materials, the only difference of Example 1 is the difference in step (4), specifically: a high-consistency disc mill is used to grind the cooked material, the grinding concentration is 25%, the disc mill gap is adjusted to 0.20 mm, the pulp after grinding is screened by a 0.10 mm sieve, the unscreened pulp is concentrated to 5% and then ground again and mixed with the screened pulp to obtain coconut pulp.

[0032] The coconut pulp prepared in Example 2 was used to make corrugated base paper, differing from Example 1 only in step 3). Specifically, the coconut pulp and recycled fiber pulp were mixed at a mass ratio of 3:7 and concentrated to 0.7%. The following chemical additives were added sequentially: a mixture of pre-emulsified cationic starch and ASA was added, wherein the amount of pre-emulsified cationic starch was 0.4% of the oven-dry fiber mass (degree of substitution 0.15), and the amount of ASA was 0.4% of the oven-dry fiber mass. The homogenizer was then turned on and stirred for 120 seconds at a stirring speed of 150 rpm. Then, CPAM emulsion (38% solids content, 6.2 million molecular weight, charge density 3.4 mmol / g) was added at 0.05% of the oven-dry fiber mass, and the stirring speed was adjusted to 200 rpm for 30 seconds. The prepared pulp was then used for rapid Kaiser method sheet making, with a sheet basis weight of 90 g / m³. 2 After drying for 10 minutes, a corrugated base paper sample was obtained and placed in a constant temperature and humidity environment (23±1℃, 50±2% RH) for testing.

[0033] The coconut pulp prepared in Example 2 was light brown, with a yield of 81.0% after cooking and grinding. The pulp ash content was 1.44%, the color was L=68.3, a=5.9, b=20.6, the kappa value was 96, the average fiber length was 0.514 mm, the width was 30.3 μm, the aspect ratio was 17, and the fiber freeness was 184 mL. The physical properties of the paper sample were tested, and the results were: density 0.66 g / cm³. 3 The ring crush index is 5.2 N·m / g, and the burst strength index is 1.5 kPa·m. 2 / g, 17 folds endurance, Cobb water absorption 60s 54 g / m 2 .

[0034] Example 3 A pulping method based on coconut shell raw materials includes the following steps: (1) Coconut shell pretreatment: The inner husk of a young coconut (without the inner shell) is removed. Its moisture content is 78%. It is cut into pieces with sides approximately 3-4 cm long. A 5-mesh sieve is used to remove debris, sand, and other small impurities. An 80mm diameter screw is selected, and the rotation speed is adjusted to 360 rpm. The coconut husk pieces are directly fed into the feed inlet of a twin-screw extruder. The material is extruded and conveyed by the feed screw to the twin-screw working area, and then sequentially enters six sets of conveying and extrusion / kneading zones. The pressure in the extrusion zone is 15 MPa. The material is discharged from the outlet with a dryness of 35%, resulting in a mixture of coconut coir and partially disintegrated coconut fibers.

[0035] (2) Screening the mixture: 1) Add water to the above mixture to concentrate it to 2.5%, and sieve it using a 0.5 mm sieve. The retained material is a bundle of coconut fiber that is radially cut and partially stripped axially. 2) The material undersize from step 1) is screened using a 0.35mm sieve, and the retained material consists of a large amount of broken coconut fiber and large-structure coconut coir components; 3) Adjust the concentration of the sieve material from step 2) to 1.0%, and use a 0.10mm sieve for screening. The retained material is a small amount of broken coconut fiber and most of the coconut coir fragments, while the sieve material is mechanically processed coconut shell fiber pulp and coconut coir powder obtained by extrusion and kneading.

[0036] (3) Soaking and steaming: Combine the retentates from steps (2) 1) and 2) and homogenize them. Then, soak them in hot water at 90°C for 30 minutes with a soaking concentration of 5%. After soaking, use a two-roller extruder to dehydrate the soaked substrate to a solid content of 15%. Then, heat it to 150°C and keep it at that temperature for 30 minutes to obtain the cooking material. (4) Grinding: The cooked material is ground using a high-concentration disc mill with a grinding concentration of 25% and a disc mill gap of 0.30 mm. The ground slurry is then screened using a 0.10 mm sieve. The unscreened slurry is concentrated to 5% and then ground again and mixed with the screened slurry to obtain coconut slurry.

[0037] The coconut pulp prepared in Example 3 is used to make corrugated base paper, and the only difference between it and Example 1 is step 3), which is as follows: The sieved material from step 3) of step (2), the coconut fiber slurry from step (4), and the recycled fiber slurry are mixed at a mass ratio of 1:2:7 and concentrated to 0.7%. The following chemical additives are then added sequentially: a mixture of pre-emulsified cationic starch and AKD, wherein the amount of pre-emulsified cationic starch is 0.5% of the dry fiber mass (degree of substitution 0.15), and the amount of AKD is 0.3% of the dry fiber mass. The homogenizer is then turned on and stirred for 120 seconds at a stirring speed of 150 rpm. Then, CPAM emulsion (38% solid content, 6.2 million molecular weight, 3.4 mmol / g charge density) is added at 0.05% of the dry fiber mass, and the stirring speed is adjusted to 180 rpm for 30 seconds. The prepared slurry is then sheeted using the rapid Kaiser method, with a sheeting quantity of approximately 90 g / m³. 2 After drying for 10 minutes, a corrugated base paper sample was obtained and placed in a constant temperature and humidity environment (23±1℃, 50±2% RH) for testing.

[0038] The coconut pulp in Example 3 was brown, with a yield of 74.5% after cooking and grinding, an ash content of 1.60%, a color of L=65.8, a=5.1, b=19.7, a kappa value of 92, an average fiber length of 0.528 mm, a width of 31.5 μm, an aspect ratio of 17, and a fiber freeness of 225 mL. The physical properties of the corrugated base paper sample were tested, and the density was 0.65 g / cm³. 3 The ring crush index is 4.9 N•m / g, and the burst strength index is 1.8 kPa•m. 2 / g, 30 folds endurance, Cobb water absorption 60s 61 g / m 2 .

[0039] Example 4 A pulping method based on coconut shell raw materials includes the following steps: (1) Coconut shell pretreatment: Take the inner peel of mature dried coconut shells after removing the inner shell. Its moisture content is 62%. Cut it into blocks with a side length of about 3 cm. Use a 5-mesh sieve to remove small impurities such as debris and sand from the material. Use hot water spray to wash away dust and adjust the moisture content to 80%. Select an 80 mm diameter screw and adjust the speed to 360 rpm. Feed the block coconut shells to the feed port of the twin-screw extruder. The material is extruded and conveyed to the twin-screw working area by the feed screw. The working area is set with three sets of conveying and extrusion kneading zones. The pressure of the extrusion zone is 20 MPa. The material is discharged from the discharge port with a dryness of 30%, and a mixture of coconut shreds and coconut coir is obtained.

[0040] (2) Screening the mixture: Add water to the mixture to concentrate it to 2.0%, and the remaining steps are the same as step (2) in Example 1.

[0041] (3) Impregnation and cooking: Combine the retentates from step (2) 1), 2), and 3) and homogenize them. Then impregnate them in hot water at 85°C for 40 minutes with an impregnation concentration of 5%. After impregnation, use a two-roller extruder to dehydrate the impregnated substrate to a solid content of 18%. Then raise the temperature to 160°C and hold the pressure for 30 minutes to obtain the cooking material.

[0042] (4) Pulping: Two high-concentration disc mills are connected in series to pulverize the cooking material. The pulverization concentration is 25%, the disc mill gap is 0.40 mm, and the pulverized material is screened by a 0.10 mm sieve. The unscreened pulverized material is concentrated to 5% and then retold and mixed with the screened pulverized material to obtain coconut slurry.

[0043] The coconut pulp prepared in Example 4 is used to make corrugated base paper, including: Take the retentate from step (2) 4), coconut fiber slurry, and recycled fiber slurry and mix them in a mass ratio of 1:2:7. Thicken the mixture to 0.75% and add the following chemical additives in sequence for slurry preparation: add a mixture of pre-emulsified cationic starch and ASA, wherein the amount of pre-emulsified cationic starch is 0.5% of the dry fiber mass (degree of substitution is 0.18) and the amount of ASA is 0.4% of the dry fiber mass. Then turn on the homogenizer and stir for 120s at a stirring speed of 160rpm. Then add 0.04% of the dry fiber mass of cationic polyacrylamide (CPAM, solid content 40%, molecular weight 8 million, charge density 3.2mmol / g), and adjust the speed to 200rpm and stir for 20s. Then add 0.3% of the dry fiber mass of bentonite, and adjust the speed to 150rpm and stir for 15s to form a CPAM-bentonite microparticle flocculation system. The prepared slurry is then sheeted using the rapid Kaiser method, and the sheeting quantity is approximately 90g / m³. 2 After drying for 12 minutes, a corrugated base paper sample was obtained and placed in a constant temperature and humidity environment (23±1℃, 50±2% RH) for testing.

[0044] Example 4 prepared a brown coconut pulp with a yield of 84.7% after cooking and grinding. The pulp ash content was 1.82%, the color was L=62.1, a=4.3, b=16.8, the kappa value was 125, the average fiber length was 0.572 mm, the width was 29.7 μm, the aspect ratio was 20, and the freeness was 316 mL. The physical properties of the paper sample were tested, and the results were: density 0.58 g / cm³. 3 The ring crush index is 6.3 N·m / g, and the burst strength index is 2.0 kPa·m. 2 / g, folding endurance 34 times, water absorption Cobb 60s 63 g / m 2 .

[0045] Example 5 A pulping method based on coconut fiber includes the following steps: (1) Pretreatment of coconut flakes: Brown coconut fiber (moisture content 14%) is cut into fiber bundles about 4cm long. It is then screened with an 8-mesh vibrating screen to remove debris and coconut coir. Hot water spray is used to remove dust and adjust the moisture content to 70%. An 80mm diameter screw is selected and its speed is adjusted to 360rpm. The coconut fiber is fed into the feed inlet of a twin-screw extruder. The material is extruded and conveyed to the twin-screw working area by the feed screw. The working area has four sets of conveying and extrusion / kneading zones. The pressure in the extrusion zone is 25MPa. The material is discharged from the outlet with a dryness of 28%, yielding coconut fiber.

[0046] (2) Soaking and steaming: The coconut fiber material after the above extrusion and kneading treatment was soaked in hot water at 90℃ for 30 minutes with a soaking concentration of 5%. After soaking, the soaked substrate was dehydrated to a solid content of 18% using a two-roller extruder. Then, the temperature was raised to 160℃ and the pressure was maintained for 30 minutes to obtain the cooking feed.

[0047] (3) Grinding: The cooked material was ground using a high-concentration disc mill with a grinding concentration of 25% and a disc mill gap of 0.30 mm. The ground slurry was then screened using a 0.15 mm slotted sieve. The unscreened slurry was concentrated to 8% and then ground again before being mixed with the screened slurry to obtain coconut slurry.

[0048] The coconut pulp prepared in Example 5 is used to make carton paperboard, and the only difference between it and Example 1 is step 3), which is as follows: 1) Packing of boxboard: Take Class A waste boxboard as raw material, remove tape, nails and other impurities, break it into paper pieces of about 5×5 cm, and then use a hydraulic pulper to break it down into dispersed recycled fiber pulp.

[0049] 2) Screen the above fiber pulp using a 0.35mm slotted sieve to remove smaller impurities (unshredded paper, shredded tape, plastic, and sand, etc.), and adjust the pulp to a freeness of 35 using a Walley beater. 0 SR; 3) Mix coconut fiber pulp and recycled fiber pulp at a mass ratio of 2:8, thicken to 0.75%, and then add the following chemical additives for pulp conditioning: a mixture of pre-emulsified cationic starch and AKD, wherein the amount of pre-emulsified cationic starch is 0.4% of the oven-dry fiber mass (degree of substitution 0.15), and the amount of AKD is 0.4% of the oven-dry fiber mass. Then, turn on the homogenizer and stir for 120 seconds at a stirring speed of 160 rpm. Next, add cationic polyacrylamide (CPAM, solid content 38%, molecular weight 6.2 million, charge density 3.4 mmol / g) to the pulp at 0.03% of the oven-dry fiber mass, and adjust the stirring speed to 200 rpm and stir for 20 seconds. Remove the prepared pulp from the homogenizer and use the rapid Kaiser method to form sheets, with a sheet yield of approximately 90 g / m³. 2 After drying for 12 minutes, a paperboard sample was obtained and placed in a constant temperature and humidity environment (23±1℃, 50±2% RH) for inspection.

[0050] The coconut pulp prepared in Example 5 was brownish-brown, with a yield of 83.9% after cooking and grinding. The pulp ash content was 1.47%, the color was L=62.9, a=5.3, b=17.4, the kappa value was 138, the average fiber length was 0.601 mm, the width was 31.3 μm, the aspect ratio was 19, and the freeness was 242 mL. The physical properties of the corrugated cardboard sample were tested, and the results were: density 0.62 g / cm³. 3 The ring crush index is 6.8 N•m / g, and the burst strength index is 1.6 kPa•m. 2 / g, 18 folds endurance, Cobb water absorption 60s 52 g / m 2 .

[0051] Example 6 A pulping method based on coconut fiber includes the following steps: (1) Pretreatment of coconut fiber: Take brown coconut fiber (moisture content 14%), cut it into fiber bundles about 4cm long, and use an 8-mesh vibrating screen to remove debris and coconut coir. Soak the sieved coconut fiber in hot water at 90℃ for 60 minutes with a soaking concentration of 8% to remove most of the hot water extract. After pre-soaking, use a double roller extruder to dewater the material and adjust the moisture content to 70% for later use.

[0052] (2) Twin-screw extrusion and kneading: Select an 80mm diameter screw and adjust the speed to 300rpm. Feed the pre-impregnated coconut flakes into the feed inlet of the twin-screw extrusion and kneading machine. The working area is set up with three sets of conveying and extrusion kneading zones. Use a pump to inject 3% NaOH solution of the material's dry weight into the conveying zone and mix it thoroughly with the material in the kneading zone. The pressure in the extrusion zone is 20MPa. Finally, the material is discharged with a dryness of 28%, and the coconut flakes are obtained.

[0053] (3) Cooking: Place the coconut shreds material after the above extrusion and kneading process into a cooker, add hot water to adjust the cooking liquid ratio to 1:5, raise the temperature to 150℃ and hold the pressure for 30 minutes.

[0054] (4) Grinding and screening: The cooked material was ground using a high-concentration disc mill with a grinding concentration of 25% and a disc mill gap of 0.40 mm. The ground slurry was screened using a 0.15 mm slotted sieve. The unscreened slurry was concentrated to 8% and then ground again and mixed with the screened slurry to obtain coconut slurry.

[0055] The coconut pulp prepared in Example 6 is used to make boxboard. The only difference from Example 1 is that step 1) uses domestic waste AA grade old boxboard as raw material, and step 3) is as follows: take coconut pulp and recycled fiber pulp at a mass ratio of 2:8, adjust the concentration to 0.75%, and add the following chemical additives in sequence for pulp conditioning treatment: add a mixture of pre-emulsified cationic starch and AKD, wherein the amount of cationic starch is 0.4% of the oven-dry fiber mass (degree of substitution is 0.15), and the amount of AKD is 0.4% of the oven-dry fiber mass. Then turn on the homogenizer and stir for 120s at a stirring speed of 160 rpm; then add pregelatinized cationic starch (degree of substitution is 0.06) to the pulp at 0.03% of the oven-dry fiber mass, which is 1.2% of the oven-dry fiber mass, and add cationic polyacrylamide (CPAM, solid content 38%, molecular weight 6.2 million, charge density 3.4 mmol / g), and adjust the speed to 200 rpm and stir for 20s. The prepared slurry was taken out of the homogenizer and formed into flakes using the rapid Kaiser method, with a flake quantity of approximately 120 g / m³. 2 After drying for 12 minutes, a paperboard sample was obtained and placed in a constant temperature and humidity environment (23±1℃, 50±2% RH) for inspection.

[0056] Example 6: The coconut pulp prepared by hot water pre-impregnation, alkaline cooking and grinding is dark brown. The yield after cooking and grinding is 78.1%, the pulp ash content is 1.28%, the color is L=52.3, a=4.5, b=11.2, the pulp kappa value is 93, the average fiber length is 0.627 mm, the width is 28.1 μm, the aspect ratio is 22, and the freeness is 235 mL. The physical properties of the corrugated cardboard sample were tested, and the results were: density 0.68 g / cm³. 3 The ring crush index is 7.1 N•m / g, and the burst strength index is 2.1 kPa•m. 2 / g, 30 folds endurance, Cobb water absorption 60s 52 g / m 2 .

[0057] Example 7 A pulping method based on coconut fiber includes the following steps: (1) Pretreatment of coconut flakes: Same as in Example 6; (2) Twin-screw extrusion and kneading: Select an 80mm diameter screw and adjust the speed to 300rpm. Feed the pre-impregnated coconut shreds into the feed inlet of the twin-screw extrusion and kneading machine. The working area is set up with three sets of conveying and extrusion kneading zones. Use a pump to inject a NaOH solution with 12% of the material's dry weight into the conveying zone and mix it thoroughly and evenly with the material in the kneading zone. The pressure in the extrusion zone is 20 MPa. Finally, the material is discharged with a dryness of 28%.

[0058] (3) Cooking: Place the coconut shreds material after the above extrusion and kneading treatment into a cooker, add hot water to adjust the cooking liquid ratio to 1:5, raise the temperature to 150℃ and hold the pressure for 60 minutes.

[0059] (4) Grinding and screening: Same as in Example 6.

[0060] Figure 3 The microstructure of the coconut pulp prepared in Example 7 shows that after alkaline cooking, the fiber surface is smooth, the fiber fibrillation is moderate, and the fiber length is well preserved.

[0061] The coconut pulp prepared in Example 7 is used to make carton paperboard. The only difference between Example 6 and Example 7 is step 3). Specifically, coconut pulp and recycled fiber pulp are mixed at a mass ratio of 2:8, concentrated to 0.75%, and the following chemical additives are added sequentially for pulp conditioning: a mixture of pre-emulsified cationic starch and ASA is added, wherein the amount of pre-emulsified cationic starch is 0.4% of the dry fiber mass (degree of substitution is 0.15), and the amount of ASA is 0.4% of the dry fiber mass. Then, the homogenizer is turned on and stirred for 120s at a stirring speed of 160rpm; 2) 1.2% of the dry fiber mass of pregelatinized cationic starch (degree of substitution is 0.06) and 0.03% of the dry fiber mass of cationic polyacrylamide (CPAM, solid content 38%, molecular weight 6.2 million, charge density 3.4mmol / g) are added to the pulp, and the stirring speed is adjusted to 200rpm and stirred for 20s. The prepared slurry was taken out of the homogenizer and formed into flakes using the rapid Kaiser method, with a flake quantity of approximately 120 g / m³. 2 After drying for 12 minutes, a paperboard sample was obtained and placed in a constant temperature and humidity environment (23±1℃, 50±2% RH) for inspection.

[0062] Example 7: The coconut pulp prepared by hot water pre-impregnation, alkaline cooking and grinding is brown. The yield after cooking and grinding is 66.3%, the ash content of the pulp is 1.12%, the color is L=43.5, a=4.1, b=9.8, the kappa value of the pulp is 78, the average fiber length is 0.584 mm, the width is 23.5 μm, the aspect ratio is 25, and the freeness is 412 mL. The physical properties of the corrugated cardboard sample were tested, and the results were: density 0.72 g / cm³. 3 The ring crush index is 7.4 N•m / g, and the burst strength index is 2.6 kPa•m. 2 / g, folding endurance 34 times, water absorption Cobb 60s 53 g / m 2 .

[0063] Example 8 A pulping method based on coconut fiber includes the following steps: (1) Pretreatment of coconut flakes: Same as in Example 6.

[0064] (2) Twin-screw extrusion and kneading: Select an 80mm diameter screw and adjust the speed to 300rpm. Feed the pre-impregnated coconut shreds into the feed inlet of the twin-screw extrusion and kneading machine. The working area is set up with three sets of conveying and extrusion kneading zones. Use a pump to inject 20% of the material's dry weight of NaOH solution into the conveying zone and mix it thoroughly with the material in the kneading zone. The pressure in the extrusion zone is 20 MPa. Finally, the material is discharged with a dryness of 25%.

[0065] (3) Cooking: Place the coconut shreds material after the above extrusion and kneading treatment into a cooker, add hot water to adjust the cooking liquid ratio to 1:6, raise the temperature to 160℃ and hold the pressure for 90 minutes.

[0066] (4) Decomposition and screening: The cooked material was decomposed using a Wali pulper with a decomposition concentration of 1.5%. The pulping was carried out for 20 minutes without applying a pulping load. The pulp was then screened using a 0.10 mm sieve. The unscreened pulp was concentrated to 5% and then re-ground (grinding disc gap 0.3 mm) and mixed with the screened pulp. The mixed pulp was washed to obtain coconut pulp.

[0067] Figure 4 The image shows the microscopic morphology of coconut fibers and some impurity cells in the coconut pulp prepared in Example 8. It indicates that the fiber surface is smooth and non-fiber impurity cells are thoroughly removed after high-alkali cooking.

[0068] The coconut pulp prepared in Example 8 is used to make carton paperboard, comprising: 1) Take AA-grade old corrugated cardboard as raw material, remove impurities such as tape and nails, break it into paper pieces of about 5×5 cm, and then use a hydraulic pulper to break it down into dispersed recycled fiber pulp.

[0069] 2) Screen the above recycled fiber pulp with a 0.35mm sieve to remove smaller impurities (unshredded paper, shredded tape, plastic, and sand, etc.), and mix it with the coconut pulp obtained in step (4) at a mass ratio of 6:4. Use a Walley pulper to adjust the pulp to a freeness of 38°SR and thicken it to 0.8%. Add the following chemical additives in sequence for pulp conditioning: add a mixture of pre-emulsified cationic starch and AKD. The amount of pre-emulsified cationic starch is 0.4% of the dry fiber mass (degree of substitution is 0.15), and the amount of AKD is 0.4% of the dry fiber mass. Then turn on the homogenizer and stir for 120s at a stirring speed of 160rpm. Add 1.2% of the dry fiber mass of pregelatinized cationic starch (degree of substitution is 0.06) and 0.03% of the dry fiber mass of cationic polyacrylamide (CPAM, solid content 38%, molecular weight 6.2 million, charge density 3.4mmol / g) to the pulp and adjust the speed to 200rpm. Stir at rpm for 20 seconds.

[0070] The prepared slurry was taken out of the homogenizer and formed into flakes using the rapid Kaiser method, with a flake quantity of approximately 120 g / m³. 2 After drying for 12 minutes, a paperboard sample was obtained and placed in a constant temperature and humidity environment (23±1℃, 50±2% RH) for inspection.

[0071] Example 8: The coconut pulp prepared by hot water pre-impregnation, alkaline cooking and decomposition is brown. The yield after cooking and grinding is 57.2%, the pulp ash content is 0.84%, the color is L=58.7, a=4.8, b=18.5, the pulp kappa value is 42, the average fiber length is 0.612 mm, the width is 21.7 μm, the aspect ratio is 28, and the freeness is 633 mL. The physical properties of the corrugated cardboard sample were tested, and the results were: density 0.75 g / cm³. 3 The ring crush index is 7.8 N•m / g, and the burst strength index is 3.4 kPa•m. 2 / g, folding endurance 48 times, water absorption Cobb 60s is 48g / m³ 2 .

[0072] Example 9 A pulping method based on coconut fiber includes the following steps: (1) Pretreatment of coconut flakes: Same as in Example 6.

[0073] (2) Twin-screw extrusion and kneading: Select an 80mm diameter screw and adjust the speed to 300rpm. Feed the pre-impregnated coconut shreds into the feed inlet of the twin-screw extrusion and kneading machine. The working area is set up with three sets of conveying and extrusion kneading zones. Use a pump to inject 20% of the material's dry weight of NaOH solution into the conveying zone and mix it thoroughly with the material in the kneading zone. The pressure in the extrusion zone is 20MPa. Finally, the material is discharged with a dryness of 25%.

[0074] (3) Steaming: Place the coconut shreds material after the above extrusion and kneading treatment into a steamer, add hot water to adjust the steaming liquid ratio to 1:6, raise the temperature to 160℃ and keep it warm for 90 minutes.

[0075] (4) Decomposition and screening: The cooked material was decomposed using a Wali pulper with a decomposition concentration of 1.5%. The pulping was carried out for 20 minutes without applying a pulping load. The pulp was then screened using a 0.10 mm sieve. The unscreened pulp was concentrated to 5% and then re-ground (grinding disc gap 0.3 mm) and mixed with the screened pulp. The mixed pulp was washed to obtain coconut pulp.

[0076] The coconut pulp-based cardboard prepared in Example 9 comprises: 1) Using AOCC-13 (US waste paper No. 13) as raw material, remove impurities such as tape and nails, and break it into paper pieces of about 5×5 cm. Then, use a hydraulic pulper to break it down into dispersed fibers. Screen the pulp with a 0.35mm slotted sieve to remove smaller impurities (unpulped paper pieces, shredded tape, plastic, and sand, etc.) to obtain recycled US waste paper pulp.

[0077] 2) Mix the recycled US waste pulp with the coconut pulp obtained in step (4) at a mass ratio of 6:4, and use a Walley pulper to adjust the mixed pulp to a freeness of 40. 0 SR was concentrated to 0.8%, and the following chemicals and excipients were added sequentially for slurry preparation: a mixture of pre-emulsified cationic starch and AKD was added, with the amount of pre-emulsified cationic starch being 0.6% of the oven-dry fiber mass (degree of substitution 0.15) and the amount of AKD being 0.4% of the oven-dry fiber mass. The homogenizer was then turned on and stirred for 120 seconds at a speed of 160 rpm. 1.5% of the oven-dry fiber mass of pre-gelatinized cationic starch (degree of substitution 0.06) and 0.04% of the oven-dry fiber mass of cationic polyacrylamide (CPAM, solid content 38%, molecular weight 8 million, charge density 3.1 mmol / g) were added to the slurry, and the stirring speed was adjusted to 200 rpm for 20 seconds. The prepared slurry was removed from the homogenizer and sheeted using the rapid Kaiser method, with a sheet yield of approximately 120 g / m³. 2 After drying for 12 minutes, a paperboard sample was obtained and placed in a constant temperature and humidity environment (23±1℃, 50±2% RH) for inspection.

[0078] Example 9: The coconut pulp prepared by hot water pre-impregnation, alkaline cooking and decomposition is brown. The yield after cooking and grinding is 57.2%, the pulp ash content is 0.84%, the color is L=58.7, a=4.8, b=18.5, the pulp kappa value is 42, the average fiber length is 0.612 mm, the width is 21.7 μm, the aspect ratio is 28, and the freeness is 633 mL. The physical properties of the corrugated cardboard sample were tested, and the results were: density 0.78 g / cm³. 3 The ring crush index is 8.3 N•m / g, and the burst strength index is 3.4 kPa•m. 2 / g, folding endurance 48 times, water absorption Cobb 60s 49 g / m 2 .

[0079] Comparative Example 1 The only difference from Example 6 is that step (2) of twin-screw extrusion and kneading is omitted.

[0080] The coconut pulp prepared in Comparative Example 1 was used to make boxboard, and the preparation method was the same as in Example 6.

[0081] The coconut pulp prepared in Comparative Example 1 was brownish-brown, with a yield of 80.7% after cooking and grinding. The pulp ash content was 1.35%, the color was L=57.6, a=5.2, b=13.8, the kappa value was 112, the average fiber length was 0.591 mm, the width was 31.7 μm, the aspect ratio was 18.6, and the freeness was 248 mL. The physical properties of the corrugated cardboard sample were tested, and the results were: density 0.59 g / cm³. 3 The ring crush index is 6.3 N•m / g, and the burst strength index is 1.8 kPa•m. 2 / g, folding endurance 23 times, water absorption Cobb 60s 58 g / m 2 .

[0082] Comparative Example 2 The only difference from Example 1 is that step (3) of soaking and cooking is omitted. The retained materials in step (2) 1), 2), and 3) are directly combined and homogenized. Then, a high-consistency disc mill is used to grind the pulp directly. The pulp concentration is 25%, the disc mill gap is 0.30 mm, and the pulp after grinding is screened with a 0.15 mm sieve. The unscreened pulp is concentrated to 12% and then ground again and mixed with the screened pulp to obtain coconut pulp.

[0083] The coconut pulp prepared in Comparative Example 2 was used to make corrugated base paper, and the preparation method was the same as in Example 1.

[0084] Comparative Example 2: The coconut pulp obtained by extrusion, kneading and grinding is yellowish-brown, with coarse and hard fibers. The yield after grinding is 80.5%, the pulp ash content is 1.38%, the color L = 67.4, a = 6.1, b = 20.6, the pulp kappa value is 115, the average fiber length is 0.448 mm, the width is 38.4 μm, the aspect ratio is 11.7, and the freeness is 187 mL. The physical properties of the corrugated base paper were tested as follows: density 0.51 g / cm³. 3 The ring crush index is 3.8 N•m / g, and the burst strength index is 1.1 kPa·m. 2 / g, folding endurance 9 times, water absorption Cobb 60s 78 g / m 2 .

[0085] Comparative Example 3 The only difference from Example 1 is that in step (4), the cooked material is concentrated to 4%, and a low-concentration disc mill is used for grinding. The disc mill gap is adjusted to 0.20 mm. The ground slurry is screened using a 0.10 mm sieve. The unscreened slurry is concentrated to 6% and then ground again and mixed with the screened slurry to obtain coconut slurry.

[0086] The coconut pulp prepared in Comparative Example 3 was used to make corrugated base paper, and the preparation method was the same as in Example 1.

[0087] The coconut pulp prepared by Comparative Example 3 after cooking and low-concentration grinding was yellowish-brown, with a yield of 87.2% after cooking and grinding, an ash content of 1.28%, a color of L=71.2, a=6.1, b=20.8, a kappa value of 112, an average fiber length of 0.519 mm, a width of 31.8 μm, an aspect ratio of 16.3, and a freeness of 258 mL. The physical properties of the corrugated base paper were tested as follows: density 0.64 g / cm³. 3 The ring crush index is 5.2 N•m / g, and the burst strength index is 1.5 kPa·m. 2 / g, 19 folds endurance, Cobb water absorption 60s 63 g / m 2 .

[0088] Comparative Example 4 The only difference from Example 1 is that steps (1) and (2) are performed as follows: Take brown coconut fiber (commercially available, moisture content 11%), cut it into fiber bundles about 4cm long, use an 8-mesh vibrating screen to remove debris, and rinse with hot water spray to remove floating dust.

[0089] The coconut pulp prepared in Comparative Example 4 was used to make corrugated base paper, and the preparation method was the same as in Example 1.

[0090] The coconut pulp obtained by Comparative Example 4 after cooking and grinding is dark brown. The yield after cooking and grinding is 78.2%, the ash content of the pulp is 1.83%, the color is L=58.4, a=4.9, b=15.6, the kappa value of the pulp is 142, the average fiber length is 0.578 mm, the width is 32.7 μm, the aspect ratio is 18, and the freeness is 251 mL. The physical properties of the corrugated base paper were tested as follows: density 0.59 g / cm³. 3 The ring crush index is 5.4 N•m / g, and the burst strength index is 1.3 kPa·m. 2 / g, 12 folding strength, Cobb 60s water absorption is 78 g / m³ 2 .

[0091] Comparative Example 5 The only difference from Example 1 is that step (1) is different. Step (1) is as follows: Coconut shell pretreatment: Take the inner husk of the green coconut after removing the inner shell. Its moisture content is 78%. Cut it into pieces with a side length of about 3-4cm. Use a 5-mesh sieve to remove debris, sand and other small impurities from the material. Select an 80mm diameter screw and adjust the speed to 360rpm. Feed the pieces of green coconut shell directly into the feed inlet of the twin-screw extruder. The material is extruded and conveyed to the twin-screw working area by the feeding screw, and then enters three sets of conveying and extrusion kneading zones in sequence. Replace the twin-screw sleeve element so that the pressure in the extrusion kneading zone is 5MPa. The material is discharged from the outlet with a dryness of 20%.

[0092] The coconut pulp prepared in Comparative Example 5 was used to make corrugated base paper, and the preparation method was the same as in Example 1.

[0093] The coconut pulp obtained by Comparative Example 5 after cooking and grinding was light brown. After discharge, the material still contained a large amount of undisintegrated lumpy coconut shell tissue. The fine pulp yield after cooking and grinding was 68.3%, the pulp ash content was 1.42%, the color was L=70.1, a=5.8, b=21.2, the pulp kappa value was 108, the average fiber length was 0.552 mm, the width was 36.4 μm, the aspect ratio was 15.2, and the freeness was 268 mL. The test results for the physical properties of the corrugated base paper sample were as follows: density 0.53 g / cm³. 3 The ring crush index is 4.2 N•m / g, and the burst strength index is 1.1 kPa·m. 2 / g, 12 folds endurance, Cobb water absorption 60s 75 g / m 2 .

[0094] Comparative Example 6 The only difference from Example 1 is that step (1) is different. Step (1) is as follows: Coconut shell pretreatment: Take the inner husk of the green coconut after removing the inner shell. Its moisture content is 78%. Cut it into pieces with a side length of about 3-4cm. Use a 5-mesh sieve to remove debris, sand and other small impurities from the material. Select an 80mm diameter screw and adjust the speed to 360rpm. Feed the pieces of green coconut shell directly into the feed inlet of the twin-screw extruder. The material is extruded and conveyed to the twin-screw working area by the feed screw. Replace the twin-screw sleeve element to make the pressure in the extrusion and kneading zone 30MPa. Then, it enters the three sets of conveying and extrusion and kneading zones in sequence. The material is discharged from the outlet with a dryness of 35%.

[0095] The coconut pulp prepared in Comparative Example 6 was used to make corrugated base paper, and the preparation method was the same as in Example 1.

[0096] The coconut pulp obtained by Comparative Example 6 after cooking and grinding was light brown, with a yield of 68.3% after cooking and grinding, an ash content of 1.24%, a color of L=71.2, a=6.5, b=22.0, a kappa value of 98, an average fiber length of 0.387 mm, a width of 30.5 μm, an aspect ratio of 13, and a freeness of 175 mL. The physical properties of the corrugated base paper were tested as follows: density 0.69 g / cm³. 3 The ring crush index is 3.8 N•m / g, and the burst strength index is 1.2 kPa·m. 2 / g, folding endurance 8 times, water absorption Cobb 60s 65 g / m 2 .

[0097] Comparative Example 7 A pulping method based on coconut fiber differs from Example 7 only in step (2): Twin-screw extrusion and kneading: Select an 80mm diameter screw and adjust the speed to 300rpm. Feed the pre-impregnated coconut fiber into the feed inlet of the twin-screw extruder. The working area is set up with three sets of conveying and extrusion / kneading zones. A pump injects a 1% NaOH solution (based on the material's oven-dry weight) into the conveying zone, where it is thoroughly mixed with the material in the kneading zone. The pressure in the extrusion zone is 20MPa. Finally, the material is discharged with a dryness of 28%.

[0098] The coconut pulp prepared in Comparative Example 7 was used to make boxboard, and the preparation method was the same as in Example 7.

[0099] The coconut pulp prepared in Comparative Example 7 was brownish-brown, with a yield of 81.3% after cooking and grinding. The pulp ash content was 1.35%, the color was L=58.6, a=5.2, b=10.8, the kappa value was 124, the average fiber length was 0.586 mm, the width was 30.2 μm, the aspect ratio was 18.8, and the freeness was 268 mL. The physical properties of the corrugated cardboard sample were tested, and the results were: density 0.64 g / cm³. 3 The ring crush index is 6.3 N•m / g, and the burst strength index is 1.7 kPa•m. 2 / g, folding endurance 20 times, water absorption Cobb 60s is 58 g / m³ 2 .

[0100] Comparative Example 8 A pulping method based on coconut fiber differs from Example 7 only in step (2): Twin-screw extrusion and kneading: Select an 80mm diameter screw and adjust the speed to 300rpm. Feed the pre-impregnated coconut fiber into the feed inlet of the twin-screw extruder. The working area is set up with three sets of conveying and extrusion / kneading zones. A pump injects a NaOH solution with 25% of the material's dry weight into the conveying zone. The pressure in the extrusion zone is 20MPa, and the material is thoroughly mixed in the kneading zone. Finally, the material is discharged with a dryness of 25%.

[0101] The coconut pulp prepared in Comparative Example 8 was used to make boxboard, and the preparation method was the same as in Example 7.

[0102] The coconut pulp prepared in Comparative Example 8 was light brown, with a yield of 43.8% after cooking and grinding, an ash content of 0.71%, a color of L=56.8, a=4.5, b=20.1, a kappa value of 35, an average fiber length of 0.485 mm, a width of 19.6 μm, an aspect ratio of 25, and a freeness of 698 mL. The physical properties of the paper sample were tested, and the results were: density 0.78 g / cm³. 3 The ring crush index is 6.5 N•m / g, and the burst strength index is 3.1 kPa•m. 2 / g, folding endurance 42 times, water absorption Cobb 60s 53g / m 2 .

[0103] Comparative Example 9 A pulping method based on coconut fiber differs from Example 7 only in that step (3) employs low-temperature, long-time cooking, specifically as follows: Place the coconut shreds material after the above extrusion and kneading process into a steamer, add hot water to adjust the cooking liquid ratio to 1:5, raise the temperature to 120℃ and hold the pressure for 180 minutes.

[0104] The coconut pulp prepared in Comparative Example 9 was used to make boxboard, and the preparation method was the same as in Example 7.

[0105] The coconut pulp prepared in Comparative Example 9 was dark brown, with a yield of 63.8% after cooking and grinding, an ash content of 1.35%, a color of L=39.2, a=4.8, b=9.2, a kappa value of 92, an average fiber length of 0.514 mm, a width of 26.8 μm, an aspect ratio of 19, and a freeness of 385 mL. The physical properties of the corrugated cardboard sample were tested, and the results were: density 0.67 g / cm³. 3 The ring crush index is 6.2 N•m / g, and the burst strength index is 2.0 kPa•m. 2 / g, folding endurance 22 times, water absorption Cobb 60s 58 g / m 2 .

[0106] Comparative Example 10 A pulping method based on coconut fiber differs from Example 7 only in that step (3) uses high-temperature short-time cooking. The coconut fiber material after the above extrusion and kneading treatment is placed in a cooker, hot water is added to adjust the cooking liquid ratio to 1:5, and the temperature is raised to 170°C and kept warm for 15 minutes.

[0107] The coconut pulp prepared in Comparative Example 10 was used to make boxboard, and the preparation method was the same as in Example 7.

[0108] The coconut pulp prepared in Comparative Example 10 was light brown, with a yield of 68.2% after cooking and grinding, an ash content of 1.37%, a color of L=57.8, a=4.7, b=19.5, a kappa value of 92, an average fiber length of 0.512 mm, a width of 28.9 μm, an aspect ratio of 18, and a freeness of 328 mL. The physical properties of the paper sample were tested, and the results were: density 0.64 g / cm³. 3 The ring crush index is 5.8 N•m / g, and the burst strength index is 2.1 kPa•m. 2 / g, folding endurance 26 times, water absorption Cobb 60s 62 g / m 2 .

[0109] The test results of the pulp and paper samples of the examples and comparative examples are shown in Table 1.

[0110] Table 1

[0111] Compared with Example 6, Comparative Example 1 did not use twin-screw extrusion and kneading, but directly ground the pulp. The fibers were more easily broken when separated by the disc mill, resulting in shorter length, higher content of fine components, lower yield, and poorer papermaking filtration. More hemicellulose was retained, resulting in poorer filtration, increased bulk, and a significant decrease in paper strength.

[0112] Compared with Example 1, In Comparative Example 2, omitting the cooking step resulted in the lignin between fibers not being softened. This made the fibers easier to cut during direct pulping, causing the average fiber length to decrease from 0.543 mm to 0.448 mm, while the fiber width increased to 38.4 μm, indicating difficulty in fiber bundle dissociation. The paper density decreased from 0.62 g / cm³. 3 Reduced to 0.51 g / cm³ 3 The ring crush index decreased from 6.5 N·m / g to 3.8 N·m / g, and the burst strength index decreased from 1.7 kPa·m. 2 / g down to 1.1 kPa·m 2 / g, folding endurance decreased from 26 times to 9 times, and water absorption decreased from 59 g / m2 Increased to 78 g / m 2 This indicates that hot water cooking plays a crucial role in softening lignin, protecting fiber length, and improving paper strength. In Comparative Example 3, during low-consistency refining, the fibers were subjected to stronger shear forces at lower concentrations, resulting in a decrease in average fiber length from 0.543 mm to 0.519 mm and an increase in free fiber content from 216 mL to 258 mL, indicating insufficient fiber fibrillation. The ring crush index decreased from 6.5 N·m / g to 5.2 N·m / g, and the bursting strength index decreased from 1.7 kPa·m. 2 / g down to 1.5 kPa·m 2 / g, the folding endurance decreased from 26 times to 19 times. This indicates that high-consistency refining is beneficial for preserving fiber length and obtaining better paper strength.

[0113] Comparative Example 4: Commercially available coconut fiber is mature, with a high lignin content and stiff fibers. It has not undergone twin-screw extrusion and kneading, resulting in stiff fibers and poor hot water impregnation / alkali cooking effects. Direct grinding with a high-consistency disc mill results in low fiber bundle dissociation efficiency. Under the same pulping conditions, the axial shortening of fibers and fine fiberization of powder are more obvious, leading to a decrease in fine pulp yield, high color, and poor paper strength. At the same time, commercially available fibers are more expensive.

[0114] In Comparative Example 5, when the extrusion pressure was too low, the material still contained a large amount of undissociated lumpy coconut shell tissue, and the fiber dissociation was insufficient. The yield decreased from 89.2% to 68.3%, the fiber width increased to 36.4 μm, and the degree of fiber liberation increased to 268 mL. The paper density decreased from 0.62 g / cm³. 3 Reduced to 0.53 g / cm 3 The ring crush index decreased from 6.5 N·m / g to 4.2 N·m / g, and the burst strength index decreased from 1.7 kPa·m. 2 / g down to 1.1 kPa·m 2 / g. This indicates that effective dissociation of coconut shell fibers cannot be achieved when the extrusion pressure is below 10MPa.

[0115] In Comparative Example 6, when the extrusion pressure was too high, the fibers were subjected to excessive shearing. The average fiber length decreased significantly from 0.543 mm to 0.387 mm, and the aspect ratio decreased from 17 to 13, indicating severe fiber breakage. The yield decreased from 89.2% to 68.3%, and the free fiber content decreased to 175 mL. Although the compactness improved slightly, the ring crush index decreased from 6.5 N·m / g to 3.8 N·m / g, and the folding endurance decreased from 26 times to 8 times. This demonstrates that when the extrusion pressure exceeds 25 MPa, fiber damage is severe, and the paper strength decreases significantly.

[0116] Compared with Example 7: Comparative Example 7, which does not use alkali, has a similar yield, slightly shorter fibers, and similar paper properties, but its alkali consumption and low-concentration black liquor treatment do not meet economic principles. In addition, compared with Example 6 which uses 3% NaOH, the physical properties of this process are significantly worse. Comparative Example 8 showed that increasing the alkali dosage significantly reduced the yield, fiber strength, and fiber length, with some physical strength indicators showing a slight decrease. From the perspectives of alkali cost, pulping yield, and paper properties, it is clear that increasing the alkali dosage to 25% offers no advantage.

[0117] Comparative Example 9 showed a low chemical reaction rate under low-temperature conditions. Although the cooking time was extended to 180 min, lignin removal was still insufficient (kappa number 92), resulting in inadequate fiber softening and dissolution. Prolonged soaking led to the accumulation of hemicellulose and cellulose dissolution, resulting in a yield (63.8%) lower than that of Example 7. The fiber length was also shorter (0.541 mm), and the paper ring crush index (6.2), bursting index (2.0), and folding endurance (22 times) were all inferior to those of Example 7.

[0118] Comparative Example 10 showed a violent but uneven high-temperature short-time cooking reaction, with excessive degradation of the surface fibers and insufficient treatment of the core fibers, resulting in a low yield. The average fiber length was shortened, but the ring crush index, bursting index, and folding endurance were all lower than in Example 7, indicating severely uneven fiber strength and a decline in overall performance. The temperature-time combination of this application achieves an optimal balance between moderate lignin removal, uniform fiber softening, and fiber strength retention; this synergistic effect is unpredictable.

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pulping method based on coconut shell raw materials, characterized in that, Includes the following steps: (1) Pretreatment: After adjusting the moisture content of the coconut shell raw material, it is processed by a twin-screw extruder to obtain a mixture. (2) Screening: The mixture is screened to separate the coconut fiber component and the usable sheet coconut coir tissue; (3) Cooking: The coconut fiber components obtained in step (2) are subjected to hot water cooking or alkaline cooking to obtain the cooking material; (4) Grinding: The cooked material is ground using a high-concentration disc mill or decomposed using a fiber decomposition machine, and then screened to obtain coconut pulp.

2. The pulping method according to claim 1, characterized in that, The coconut shell raw material mentioned in step (1) is selected from at least one of the coconut shell peel and coconut fiber.

3. The pulping method according to claim 1, characterized in that, The processing conditions of the twin-screw extrusion kneading machine in step (1) are: material dryness at the inlet 20%-35%, extrusion zone pressure 10-25MPa, screw speed 300-420rpm, and material dryness at the outlet 25%-40%.

4. The pulping method according to claim 2, characterized in that, The screening in step (2) includes multi-level screening, which includes: 1) The mixture was screened using a sieve with an aperture of ≤1mm, and the retained material was coconut fiber; 2) Use a 0.5-0.6mm mesh sieve to screen the material undersize from step 1), and retain the radially cut and axially torn coconut fiber bundles; 3) Use a 0.10-0.35mm sieve to screen the material undersize from step 2), and retain the partially broken coconut fiber and large-flake coconut coir components. 4) Add water to the sieved material from step 3) to dilute it, and then use a 0.10-0.35mm sieve to screen it, retaining a small amount of broken coconut fiber and most of the coconut coir fragments.

5. The pulping method according to claim 1, characterized in that, In step (3), when hot water is used for cooking, the fiber component is immersed in hot water at 85-90℃ for 20-60 minutes with an immersion concentration of 3%-8%. After immersion, it is dehydrated to a solid content of 15%-20%, and then heated to 140-170℃ and kept warm for 15-60 minutes. When using alkaline cooking, add NaOH solution during the twin-screw extrusion and kneading process. The amount of NaOH used is 3%-22% of the dry material mass. Adjust the liquid ratio to 1:4-1:7 during cooking and heat to 130-160℃ for 30-120 minutes.

6. The pulping method according to claim 1, characterized in that, In step (4), the high-concentration disc mill has a pulp concentration of 15%-25% and a disc mill gap of 0.3mm-0.5mm. After grinding, the pulp is screened using a slotted screen with a slot size of 0.10-0.25mm. The unscreened pulp is concentrated to 5%-15% and then re-ground. The re-ground pulp is mixed with the screened pulp to obtain coconut pulp.

7. A coconut milk paste, characterized in that, It is obtained by the preparation method according to any one of claims 1-6.

8. The application of the coconut pulp as described in claim 7 in the fabrication of corrugated packaging materials.

9. The application according to claim 8, characterized in that, The coconut pulp with a mass ratio of 1:9-7:3 is mixed with recycled fiber pulp, chemical additives are added, and corrugated packaging material is obtained by papermaking. The corrugated packaging material includes corrugated base paper or boxboard. The recycled fiber pulp is obtained by decontamination, purification, screening and pulping of old boxboard or carton processing trimmings, with a beating degree of 32-45°SR.

10. The application according to claim 9, characterized in that, The chemical excipients include one or more of cationic starch, AKD or ASA, polyacrylamide, and bentonite.

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