Preparation method of bamboo fiber for filter paper, filter paper containing the bamboo fiber, and preparation method of filter paper

Abstract

The application relates to a preparation method of a bamboo fiber for filter paper, a filter paper containing the bamboo fiber and a preparation method of the filter paper. The preparation method of the bamboo fiber for filter paper comprises the following steps: (1) selecting bamboo materials; (2) chemically treating the bamboo materials selected in the step (1) by using chemical medicines; (3) defibrating the material obtained in the step (2) to obtain a coarse pulp; and (4) screening the coarse pulp obtained in the step (3) to obtain the bamboo fiber. The bamboo fiber prepared by the application has the mechanical property of high elastic modulus, and the air filter paper manufactured by using the bamboo fiber has the properties of high air permeability, high stiffness and high bulk thickness.

Description

Technical Field

[0001] This invention relates to the fields of pulp and paper making and filter materials technology, specifically to a method for preparing bamboo fiber for filter paper, filter paper containing the bamboo fiber, and a method for preparing filter paper. Background Technology

[0002] The fibers used in existing wood pulp filter paper bases are mainly flash pulp or mercerized pulp from coniferous / broadleaf wood. From the morphological characteristics of the fibers themselves, coniferous (or broadleaf) fibers have a larger diameter. Compared to straight fibers with smaller diameters, this inevitably results in filter paper base materials with larger pore sizes, lower porosity, and greater thickness for the same basis weight. This leads to lower air permeability and filtration accuracy, a smaller effective filtration surface area, and difficulty in accommodating a large number of folds within the same volume. Simultaneously, flash pulp fibers have low stiffness and are prone to deformation. During use, the filter cartridges easily absorb moisture and swell, causing "paper clumping" and significantly shortening the lifespan of the filter cartridges.

[0003] Bamboo, "neither rigid nor flexible, neither grass nor wood," possesses fibers that are both stiff and tough, exhibiting a balance of strength and flexibility. It has a large length-to-width ratio, thick cell walls, small cell lumens, and is smooth yet rigid. Currently, there are technologies for using bamboo pulp or bamboo fiber to prepare filter paper. Some patent applications mention using bamboo fiber to manufacture filter paper, but they only specify the use of bamboo pulp fiber without addressing the specific preparation of bamboo pulp fiber or considering the current defects of bamboo pulp fiber, such as impurities like cells. In fact, current chemical pulp of bamboo has fibers that are too soft and contain many impurities; chemimechanical pulp has too many fiber bundles and contains many impurities. Compared to the base materials for filter paper, the fiber rigidity and fineness or denier of these materials are not ideal. The resulting filter paper has poor porosity and stiffness.

[0004] Therefore, developing a high-quality, rigid bamboo fiber to solve the problems and defects of existing wood pulp filter paper is of profound significance. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a method for preparing bamboo fiber for filter paper, a filter paper containing the bamboo fiber, and a method for preparing the filter paper. The bamboo fiber prepared in this invention is guided by the properties of the filter paper base material, such as stiffness, air permeability, thickness, and pore size / filtration accuracy. The resulting bamboo fiber is slender with thick walls and small cavities, has high lignin content in the fiber cell walls, and low lignin content between fiber cells. Furthermore, the resulting bamboo fiber exhibits excellent elastic modulus, zero-pitch tensile strength, and hardness, making it particularly suitable for filter paper preparation. Filter paper prepared using the bamboo fiber obtained by this invention possesses advantages such as high air permeability, high stiffness, high filtration accuracy, and long lifespan.

[0006] Therefore, one object of the present invention is to provide a method for preparing bamboo fiber for filter paper.

[0007] Another object of the present invention is to provide uses for the above-mentioned bamboo fiber.

[0008] Another object of the present invention is to provide a filter paper comprising the above-mentioned bamboo fiber.

[0009] Another object of the present invention is to provide a method for preparing the above-mentioned filter paper.

[0010] The above-mentioned objective of the present invention is achieved by the following technical solution.

[0011] On one hand, the present invention provides a method for preparing bamboo fiber for filter paper, the method comprising the following steps:

[0012] (1) Material selection

[0013] Select bamboo materials;

[0014] (2) Chemical treatment

[0015] The bamboo material selected in step (1) was chemically treated with chemical agents;

[0016] (3) Relief

[0017] The material obtained from the chemical treatment in step (2) is decomposed to obtain coarse slurry;

[0018] (4) Filtering

[0019] The coarse pulp obtained in step (3) is screened to obtain bamboo fiber.

[0020] Preferably, in step (1), the bamboo material is industrial bamboo, but is not limited thereto. For example, it is selected from: *Melocanna* (pear bamboo): *Melocanna huilis* Kurz; *Schizostachyum* (sand bamboo): *Schizostachyum funghomii* McClure; *Bambusa* (beard bamboo): *Bambusa gibba* McClure, *Bambusa pervariabilis* McClure, *Bambusa surrecta*, *Bambusa textilis* McClure; *Neosinocalamus* (beard bamboo): *Neosinocalamus affinis*; *Dendrocalamopsis* (green bamboo): *Dendrocalamopsis daii* Keng, *Dendrocalamopsis oldhamii* Keng; *Dendrocalamus* (mist bamboo): *Dendrocalamus minor*, *Dendrocalamus barbatus*, *Dendrocalamus farinosus*, *Dendrocalamus giganteus* Munro, Dendrocalamus latiflorus Munro, Dendrocalamus membranaceus Munro; Gigantochloa: Gigantochloa verticillata; Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, and Phyllostachys edulis. More preferably, the bamboo is selected from: Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis; Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis. More preferably, the bamboo is selected from: Phyllostachys: Phyllostachys nigra, Phyllostachys edulis, Phyllostachys edulis; Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis, Phyllostachys edulis, Phyllostachys edulis; Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis, Phyllostachys edulis, Phyllostachys edulis, Phyllostachys edulis. Most preferably, the bamboo is selected from: Phyllostachys flexuosa, Phyllostachys flexuosa, Phyllostachys edulis, and Phyllostachys edulis.

[0021] Preferably, in step (1), the growth period of the bamboo is more than 2 years, for example more than 3 years; preferably 3 to 6 years; more preferably 3 to 5 years; even more preferably 3 to 4 years; and most preferably 3.5 years.

[0022] Preferably, in step (1), the bamboo material is a single type of bamboo or a mixture of multiple types of bamboo, with a single type of bamboo being more preferred.

[0023] Preferably, in step (2), the chemical drug is selected from RSO3Na (R=C 12 ~C 22 Alkyl groups), H2NNaSO3, NaOH, KOH, Ca(OH)2, Na2S, C 14 H 23 O 10 N3, Na2SO3 and C 14 One or more of H8O2.

[0024] Preferably, the RSO3Na is R1SO3Na (R1 = C 14 ~C 22 Alkyl group), R2SO3Na (R2=C) 12 ~C 16 alkyl groups), C 12 H 25 SO3Na or C 18 H 29 NaO3S;

[0025] Preferably, in step (2), the chemical agent is selected from NaOH, Na2S, C 14 H8O2 and C 12 H 25 A mixture of SO3Na, with a mass ratio of 195–205:4–6:0.8–1.2:0.45–0.55, preferably 200:5:1:0.5; NaOH, Na2SO3, Na2S, C 14 H8O2 and C 12 H 25 A mixture of SO3Na in a mass ratio of 195–205:22–24:2.5–3.5:0.45–0.55, preferably 200:23:3:0.5:0.5; NaOH, Na2S, and C 12 H 25 A mixture of SO3Na, with a mass ratio of 195–205:21–23:0.8–1.2, preferably 200:22:1; NaOH, Na2SO3, C 14 A mixture of H8O2 and H2NSO3Na, with a mass ratio of 195–205:22–24:0.8–1.2:0.8–1.2, preferably 200:23:1:1; NaOH, C 14 H8O2 and C 12 H 25 The mixture of SO3Na has a mass ratio of 220-230:0.5-1.5:0.5-1.5, preferably 225:1:1.

[0026] Preferably, in step (2), the mass of the chemical drug is 18wt% to 25wt% of the oven-dry mass of the bamboo, and more preferably 20wt% to 23wt%.

[0027] Preferably, in step (2), the chemical treatment is carried out in a reactor under heating.

[0028] Preferably, the heating is steam heating or electric heating.

[0029] Preferably, the solid-liquid ratio used for electric heating is 1:4.0 to 4.3, more preferably 1:4.2; the solid-liquid ratio used for steam heating is 1:3.5 to 3.8, more preferably 1:3.6.

[0030] The solid-liquid ratio refers to the ratio of the oven-dry mass of the bamboo to be treated to the total water mass of the reaction system. The total water mass includes the mass of the bamboo's moisture and the mass of steam condensate. If the water mass of the reaction system is insufficient, clean water can be added to achieve the aforementioned solid-liquid ratio.

[0031] The mixing of bamboo and chemical agents can be carried out either inside or outside the reactor. For large-scale production, mixing inside the reactor is preferred. That is, the required chemical agents are prepared into solutions of a certain concentration and then quantitatively pumped into the reactor to be mixed with the bamboo.

[0032] Preferably, the reactor is an alkali-resistant medium-low pressure vessel, including a horizontal tube continuous cooker, a liquid circulation replacement cooker, a steam ball, and a horizontal or vertical rotary cooker, etc.

[0033] Preferably, in step (2), the time and temperature of the chemical treatment are controlled as follows: the temperature is increased from room temperature to 90-110°C within 20-45 minutes, then increased to 130-150°C within 40-60 minutes, and then increased to 165°C within 90-120 minutes, and held at this temperature for 30-40 minutes; preferably, the temperature is increased from room temperature to 100°C within 35-45 minutes, then increased to 145°C within 50-60 minutes, and then increased to 165°C within 100-120 minutes, and held at this temperature for 30-40 minutes.

[0034] The preferred method is to raise the temperature from room temperature to 100°C in 40 minutes, then raise it to 145°C in 55 minutes, and then raise it to 165°C in 110 minutes, and hold it at that temperature for 35 minutes.

[0035] Preferably, in step (3), the dewatering includes high-concentration dewatering and low-concentration dewatering.

[0036] Preferably, the high-concentration disintegration refers to the mechanical processing of the material by a high-concentration disintegration device to disperse the material, and the concentration of the high-concentration disintegration is 8wt% to 15wt%, preferably 10wt%.

[0037] Preferably, the rotation speed of the dewatering equipment used in the low-concentration dewatering is ≥3000 r / min.

[0038] Preferably, the concentration of the low-concentration slurry is ≤4wt%.

[0039] Preferably, in step (4), the screening includes a slit screen and a perforated screen. The screening removes undispersed fiber bundles or clumps, miscellaneous cells, microfibers, and thin-walled fragments by using the slit screen and the perforated screen.

[0040] Preferably, the slurry concentration of the slit screen is ≤2wt% and the slit width is ≤0.5mm; more preferably, the slurry concentration is 0.9wt% to 1.1wt% and the slit width is 0.15mm to 0.25mm.

[0041] Preferably, the pulp concentration of the sieve is ≤1wt% and the pore size is ≤0.4mm; more preferably, the pulp concentration is 0.1wt% to 0.3wt% and the pore size is 0.1mm to 0.3mm.

[0042] Preferably, the preparation method further includes a concentration (dilution or concentration) step. "Concentration" refers to the process of thickening (concentrating) the pulp if a higher concentration is required for the desired stage, and conversely, dilution if a lower concentration is needed. The concentration is achieved by removing free water and fine particles using an inclined or circular screen device, with a mesh size of 45-100 mesh, preferably 50-80 mesh. Preferably, the preparation method also includes a pretreatment step of the selected bamboo material before chemical treatment.

[0043] Preferably, the pretreatment includes: removing branches and leaves from the bamboo, retaining the internodes and slicing them, and washing with water to remove impurities.

[0044] Preferably, the slice size is 40mm (length) x 30mm (width), and more preferably 35mm (length) x 25mm (width).

[0045] Preferably, the water used for washing is clean water (which may be tap water or self-made, cleaner stored water, such as water from rivers, wells, or treated recycled water) or alkaline water (i.e., water with pH > 7).

[0046] Preferably, the alkali in the alkaline water is selected from sodium hydroxide, potassium hydroxide, for example, sodium hydroxide.

[0047] Preferably, the water temperature for washing is room temperature.

[0048] Preferably, the pretreated bamboo is stacked for no more than 4 weeks for chemical treatment.

[0049] In one specific implementation, the present invention employs a physical method to pretreat bamboo. Specifically, after the bamboo is felled, branches and leaves are removed using mechanical and physical methods. Preferably, the culm rings, internodes (septa), and sheath rings (culm sheaths) are removed, while the internode segments are retained. The bamboo is then sliced ​​and washed with water to remove impurities such as mud, sand, and stones, as well as some waxy membranes and some water-soluble substances.

[0050] The internodes can be crushed, split, shortened, and sliced ​​using a slicing machine. The slices are 40mm (length) x 30mm (width), preferably 35mm (length) x 25mm (width), and the bamboo slices have cracks and beveled cuts.

[0051] The water used for washing is recyclable water, preferably clean water, and more preferably alkaline water, i.e., alkaline water with a pH > 7. The alkalinity in the alkaline water includes all substances that can generate hydroxide ions, not limited to sodium hydroxide. The water temperature for washing is room temperature, preferably heated by exhaust gas to ensure that the water temperature is not lower than room temperature.

[0052] Pre-treated bamboo strips can be used immediately or stored as spare material, with a storage time not exceeding 4 weeks.

[0053] The method for preparing bamboo fiber according to the present invention is described in detail below.

[0054] First, bamboo is selected and the bamboo culms are cut. Then, the bamboo culms are pretreated (mainly by physical methods). After that, they are chemically treated to remove lignin. The resulting material is then decomposed to obtain coarse pulp. The coarse pulp is then screened (mainly by physical methods) to obtain bamboo fiber.

[0055] Bamboo selection

[0056] The bamboo material used in this invention is primarily industrial bamboo, but is not limited thereto. You can select from: *Melocanna* (pear bamboo): *Melocanna huilis* Kurz; *Schizostachyum* (sand bamboo): *Schizostachyum funghomii* McClure; *Bambusa* (beard bamboo): *Bambusa gibba* McClure, *Bambusa pervariabilis* McClure, *Bambusa surrecta*, *Bambusa textilis* McClure; *Neosinocalamus* (beard bamboo): *Neosinocalamus affinis*; *Dendrocalamopsis* (green bamboo): *Dendrocalamopsis daii* Keng, *Dendrocalamopsis oldhamii* Keng; *Dendrocalamus* (mist bamboo): *Dendrocalamus minor*, *Dendrocalamus barbatus*, *Dendrocalamus farinosus*, *Dendrocalamus* giganteus Munro, Dendrocalamus latiflorus Munro, Dendrocalamus membranaceus Munro; Gigantochloa: Gigantochloa verticillata; Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis.

[0057] Preferred species: Bambusa genus: Bambusa textilis, Bambusa lanceolata, Bambusa oleifera, Bambusa textilis var. chinensis; Bambusa genus: Bambusa textilis, Bambusa textilis var. chinensis, Bambusa textilis var. chinensis, Bambusa textilis var. chinensis, Bambusa textilis var. chinensis; Bambusa textilis genus: Bambusa textilis var. chinensis, ...

[0058] The best choices are: sweet bamboo, hanging bamboo, small-leaf bamboo, and large-leaf bamboo.

[0059] The growth period for harvesting bamboo is 2 years or more, for example, more than 3 years. More preferably, it is 3 to 6 years. Even more preferably, it is 3 to 4 years. Most preferably, it is 3.5 years.

[0060] Pretreatment of bamboo poles

[0061] After the bamboo culms are felled, branches and leaves are removed using mechanical and physical methods. Preferably, the culm rings, internodes (septa), and sheath rings (culm sheaths) are removed, while the internode segments are retained and cut into short slices. The bamboo is then washed with water to remove impurities such as mud, sand, and stones, as well as some waxy membranes and some water-soluble substances.

[0062] The internodes can be crushed, split, shortened, and sliced ​​using a slicer. The preferred slice size is 40mm (length) x 30mm (width), and more preferably 35mm (length) x 25mm (width). The bamboo slices should have cracks and beveled cuts.

[0063] The water used for washing is recyclable recycled water. Clean water is preferred. Alkaline water, with a pH > 7, is even better. The alkalinity in the alkaline water includes all substances that can generate hydroxide ions, not limited to sodium hydroxide. The water temperature is room temperature; preferably, tail steam heating is used to ensure the water temperature is not lower than room temperature.

[0064] Pre-treated bamboo strips can be used immediately or stored as spare material, but the storage time should not exceed 4 weeks. The bamboo material can be a single type of bamboo or a mixture of multiple types of bamboo, with a single type of bamboo being preferred.

[0065] Chemical treatment of bamboo

[0066] The pretreated bamboo strips are mixed with chemical agents and then chemically processed in a reactor.

[0067] The chemical reagents used were selected from: RSO3Na (R=C 12 ~C 22 Alkyl groups), H2NNaSO3, NaOH, KOH, Ca(OH)2, Na2S, C 14 H 23 O 10 N3, Na2SO3, C 14 H8O2. The mass of the chemical agent is 18wt% to 25wt% of the oven-dry mass of the bamboo strips to be treated, preferably 20wt% to 23wt%.

[0068] The mixing of bamboo chips and chemical drugs can be carried out either inside or outside the reactor. For large-scale production, mixing inside the reactor is preferred. That is, the required chemical drugs are prepared into solutions of a certain concentration and then quantitatively pumped into the reactor to be mixed with the bamboo chips.

[0069] The reactor is an alkali-resistant, low-to-medium pressure vessel, including a horizontal tube continuous cooker, a chemical solution circulation and replacement cooker, a steam ball, and a horizontal or vertical rotary cooker. The reactor is heated by steam or electricity.

[0070] When heated electrically, the solid-liquid ratio is 1:4.0 to 4.3, preferably 1:4.2. When heated with steam, the solid-liquid ratio is 1:3.5 to 3.8, preferably 1:3.6. The solid-liquid ratio refers to the ratio of the oven-dry mass of the bamboo strips to be treated to the total mass of water in the reaction system. The total mass of water includes the mass of the moisture in the bamboo strips and the mass of the steam condensate.

[0071] The time and temperature of the chemical treatment are controlled as follows: The temperature is increased from room temperature to 90-110°C within 20-45 minutes, then further increased to 130-150°C within 40-60 minutes, followed by further increased to 165°C within 90-120 minutes, and held at this temperature for 30-40 minutes; preferably: the temperature is increased from room temperature to 100°C within 35-45 minutes, then further increased to 145°C within 50-60 minutes, followed by further increased to 165°C within 100-120 minutes, and held at this temperature for 30-40 minutes; more preferably: the temperature is increased from room temperature to 100°C within 40 minutes, then further increased to 145°C within 55 minutes, followed by further increased to 165°C within 110 minutes, and held at this temperature for 35 minutes. The heating time and the temperature reached are a steady increasing process.

[0072] Disperse

[0073] After the chemical treatment is completed, it is necessary to extract the concentrated black liquor and washing pulp, and adjust the material to a suitable concentration for dissolution.

[0074] The fiber dispersion includes high-concentration dispersion and low-concentration dispersion. The high-concentration dispersion is achieved by mechanically dispersing the fiber clumps using a high-concentration dispersing device. The concentration of the high-concentration dispersing is 8 wt% to 15 wt%, preferably 10 wt%.

[0075] After high-consistency pulping, the pulp is washed and further diluted to a suitable concentration for pulping, followed by low-consistency pulping. The dilution is achieved by adjusting the pulp concentration to a suitable consistency (1-4 wt%) using clean water.

[0076] The low-concentration debonding is a process of dispersing fiber bundles using AC or DC motor debonding equipment, with the debonding equipment rotating at a speed ≥3000 r / min and the pulp concentration ≤4%.

[0077] filter

[0078] The screening includes slit sieves and perforated sieves. Undispersed fiber bundles or clumps, miscellaneous cells, microfibers, and thin-walled fragments are removed by slit sieves and perforated sieves.

[0079] The parameters for the slotted sieve are: pulp concentration ≤ 2wt% and slot width ≤ 0.5mm, preferably pulp concentration 0.9wt%~1.1wt% and slot width 0.15mm~0.25mm; the parameters for the perforated sieve are: pulp concentration ≤ 1wt% and aperture ≤ 0.4mm, preferably pulp concentration 0.1wt%~0.3wt% and aperture 0.1mm~0.3mm.

[0080] The screened pulp can be concentrated to obtain fine fibers, namely bamboo fiber. The concentration involves removing free water and fine particles using an inclined or cylindrical screen device according to the required pulp concentration. The mesh size used is 45-100 mesh, preferably 50-80 mesh. The resulting fine pulp can be used directly as a base material for air filter paper or further dehydrated and dried to produce pulp boards or blocks for sale as commercial pulp.

[0081] On the other hand, the present invention provides the use of bamboo fiber prepared by the above method in the preparation of air filter paper.

[0082] In another aspect, the present invention provides a filter paper comprising bamboo fiber prepared by the above method. In the present invention, the filter paper may comprise 100% bamboo fiber prepared by the above method, or it may comprise a portion of bamboo fiber prepared by the above method.

[0083] In another aspect, the present invention provides a method for preparing the above-mentioned filter paper, the method comprising: feeding the bamboo fiber through pulping, wet forming, gluing and drying to obtain the filter paper.

[0084] Preferably, the pulping and feeding process involves preparing the bamboo fiber into a web paper material of a certain concentration.

[0085] Preferably, the concentration of the paper stock is 0.6wt‰ to 6wt‰, and more preferably 1 to 2wt‰.

[0086] Preferably, the wet forming process involves forming a wet paper base from the paper stock using a wet forming device such as an inclined wire, a rotary wire, or a laboratory sheeter.

[0087] Preferably, the adhesive is applied by dipping, penetrating, or coating the wet paper substrate to give the wet paper substrate higher physical strength after drying. The adhesive is selected from: C3H6N6 emulsion, C3H4O2 emulsion, C... 19 H 42 BrN、(C 11 H 12 O3) n1 (where n1 = 4~8), (C6H6O·CH2O)x (x = 5~10) (available for purchase, for example, from Shandong Yinglang Chemical Co., Ltd.), (C4H6O2) n2(n2 = 400-800) (available for purchase, for example, from Shandong Dongda Polymer Co., Ltd.). Preferably, the concentration of the suspension is 20wt%-30wt%, more preferably 25wt%.

[0088] Preferably, a through-type adhesive is used, and the amount of adhesive applied accounts for 5 wt% to 10 wt% of the oven-dry weight of the substrate fiber, preferably 8 wt%.

[0089] Preferably, the sizing is applied when the wet paper has a dryness of 35% to 60%, more preferably 50%.

[0090] The drying and shaping process involves passing the glued wet paper base through processes such as drying equipment, finishing equipment, corrugating equipment, and marking equipment to achieve the effects of drying, flattening, corrugating, and marking the filter paper, resulting in a shaped product.

[0091] Preferably, the drying equipment can use drying cylinders, drying tunnels, flat plates, infrared drying, etc., and preferably uses a through-type drying cylinder.

[0092] Preferably, the drying process is carried out in a temperature zone and temperature increment manner, and can be divided into a preheating zone, a drying zone, a curing zone and a cooling zone; the heating temperature is 110℃~155℃, the curing temperature is 150℃~155℃, and the curing time is 1~10min.

[0093] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0094] This invention innovatively prepares bamboo fiber suitable for use in filter paper, and uses this bamboo fiber to manufacture 100% bamboo fiber filter paper with excellent filtration performance.

[0095] The bamboo fiber prepared by this invention has high elastic modulus mechanical properties. The air filter paper made from it has high air permeability, high stiffness, and high bulk. Moreover, the bamboo fiber with these properties can be used to prepare filter paper made from single bamboo fiber, that is, 100% bamboo fiber.

[0096] The bamboo fiber prepared by this invention can not only produce wood pulp filter materials, but also manufacture specialty papers or paper bases with high strength, high stiffness, and abrasion resistance. The air filter paper made from it can solve the problems of low air permeability, low stiffness, and easy "paper bridging" of existing pure wood pulp filter paper, and can replace flash or mercerized softwood / broadwood pulp in the production of wood pulp filter paper.

[0097] This invention provides a method for preparing bamboo fiber that uses minimal chemical reagents, consumes little water, electricity, and steam, and generates minimal wastewater pollution. The filter paper product, made from 100% plant fiber raw materials, is easily biodegradable and environmentally friendly. The manufactured filter cores are particularly suitable for air filtration in the intake air filtration systems of heavy-duty trucks and construction machinery, as well as in fresh air systems in car interiors, tunnels, and building interiors.

[0098] The raw materials used in this invention are readily available, and the product can be transformed into production with appropriate technical modifications in existing pulp mills or paper mills. The production cost is low, the product is economical, and it has wide applicability.

[0099] Traditional chemical pulping of plant fibers is performance-oriented, primarily focusing on the physical strength properties of paper, such as tensile strength, tear strength, and bursting strength. It emphasizes fiber morphology (long / thin-walled / large-cavity), chemical composition (high cellulose content / low lignin content), biological structure (low non-fibrous cell content), ease of pulping and bleaching, and fiber binding strength in the finished paper. Particular attention is paid to the fiber's flexibility, with a focus on removing as much lignin as possible from the raw material. This invention, however, uses a bamboo fiber preparation method that prioritizes the performance of filter paper materials, focusing on filtration properties such as stiffness, air permeability, thickness, and pore size / filtration accuracy. It emphasizes the long / thick-walled / small-cavity fiber morphology and high-lignin-content fiber cell walls, with significant attention to fiber rigidity and the elastic modulus of the extracted fibers. The method aims to remove as much lignin as possible from between fiber cells while retaining as much lignin as possible within the fiber cell walls. The technical approaches, methods, and processes employed by these two methods differ significantly. Attached Figure Description

[0100] Figure 1 Scanning electron microscope image of air filter paper made from bamboo fiber prepared according to the present invention. Detailed Implementation

[0101] The technical solution of the present invention will be further described below with reference to specific embodiments. These embodiments are merely illustrative of the present invention and not intended to limit its scope, and the implementation schemes of the present invention are not limited thereto. Any changes, substitutions, modifications, simplifications, etc., made without departing from the technical concept and method principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. This also includes the substantial extension of the technical concept of this patent in the production of pineapple fiber, Manila hemp fiber, rush fiber, etc., and their substantial application in filter paper manufacturing, etc.

[0102] Unless otherwise specified, the chemical reagents and apparatus used in the following examples are commercially available.

[0103] Example 1

[0104] Preparation of bamboo fiber

[0105] Cut the internodes of sweet bamboo (3.5 years of growth period) into bamboo strips about 35mm x 25mm in length and width. Soak 1kg of the dried bamboo strips in alkaline water with pH 8-9 for 30 minutes, then wash and drain.

[0106] Load the contents into a 15L electric rotary cooker, then add 220g NaOH, 5g Na2S, and 1g C. 14 H8O2, 0.5gC 12 H 25 SO3Na was used for chemical treatment, with clean water added at a solid-liquid ratio of 1:4.2. The time and temperature of the chemical treatment were controlled as follows: the temperature was increased from room temperature to 100°C in 40 minutes, then increased to 145°C in 55 minutes, and then increased to 165°C in 110 minutes, and held at this temperature for 35 minutes.

[0107] After cooking, the material is diluted to a 10% concentration in a high-concentration diluent. Then, it is diluted to a 1% concentration in a high-speed mixer (20,000 r / min).

[0108] After the slurry is cleared, it is processed by a flat sieve (slit width 0.15mm) and a fiber sieve (50 mesh (0.3mm)). The slurry concentration of the sieve is 0.9wt% and that of the perforated sieve is 0.1wt%, which is the final product.

[0109] The properties of the bamboo fiber prepared above are as follows: elastic modulus of 25.64 GPa, zero-pitch tensile strength of 15.52 KN / 15 mm, and hardness of 379.56 MPa.

[0110] Preparation of filter paper

[0111] The bamboo fiber prepared by 100% above was processed into a paper weight of 93 g / m³ at a concentration of 1 wt‰. 2 For wet paper base, sizing is applied using the C3H4O2 emulsion impregnation method when the wet paper has a dryness of 50%. When the paper base has a dryness of 95%, the sizing amount is 8 g / m². 2 Cur at 155℃ for 5 minutes.

[0112] The scanning electron microscope image of the filter paper prepared above is shown below. Figure 1 As shown, the performance is as follows: air permeability is 1298 mm / s, stiffness is 209 mN, and bulk is 5.75 cm. 3 / g, average pore size 49.5μm, initial filtration efficiency 15.3%.

[0113] Example 2

[0114] Preparation of bamboo fiber

[0115] Cut the internodes of the bamboo (3.5 years of growth period) into bamboo strips about 35mm x 25mm in length and width. Take 1kg of the oven-dry weight and soak it in alkaline water with pH 8-9 for 30 minutes. Then wash and drain.

[0116] Load the contents into a 15L electric rotary cooker, then add 200g NaOH, 23g Na2SO3, 3g Na2S, and 0.5g C. 14 H8O2, 0.5g C 12 -SO3Na was used for chemical treatment, with water added at a solid-liquid ratio of 1:4. The time and temperature of the chemical treatment were controlled as follows: the temperature was increased from room temperature to 100°C in 45 minutes, then increased to 145°C in 50 minutes, and then increased to 165°C in 100 minutes, and held at this temperature for 30 minutes.

[0117] After cooking, the material is diluted to a 10% concentration in a high-concentration diluent. Then, it is diluted to a 1% concentration in a high-speed mixer (20,000 r / min).

[0118] After the slurry is cleared, it is processed by a flat sieve (slit width 0.15mm) and a fiber sieve (50 mesh). The slurry concentration of the sieve is 1.1wt% and that of the perforated sieve is 0.3wt%, which is the final product.

[0119] The properties of the bamboo fiber prepared above are as follows: elastic modulus of 24.24 GPa, zero-pitch tensile strength of 17.52 KN / 15 mm, and hardness of 396.72 MPa.

[0120] Preparation of filter paper

[0121] The bamboo fiber prepared by 100% above was processed into a paper weight of 93 g / m³ at a concentration of 1 wt‰. 2 For wet paper base, sizing is applied using the C3H4O2 emulsion impregnation method when the wet paper has a dryness of 50%. When the paper base has a dryness of 95%, the sizing amount is 8 g / m². 2 Cur at 155℃ for 5 minutes.

[0122] The properties of the filter paper prepared above are as follows: air permeability 1074 mm / s, stiffness 206 mN, and bulk 5.71 cm. 3 / g, average pore size 30.4μm, initial filtration efficiency 18.7%.

[0123] Example 3

[0124] Preparation of bamboo fiber

[0125] Cut the internodes of small-leaved bamboo (3.5 years of growth period) into bamboo strips about 35mm x 25mm in length and width. Take 1kg of the oven-dry weight and soak it in alkaline water with pH 8-9 for 30 minutes. Then wash and drain.

[0126] Load the contents into a 15L electric rotary cooker, then add 200g NaOH, 22g Na2S, and 1g C. 12 H 25 SO3Na was used for chemical treatment, with water added at a solid-liquid ratio of 1:4.3. The time and temperature of the chemical treatment were controlled as follows: the temperature was increased from room temperature to 100°C in 45 minutes, then increased to 145°C in 60 minutes, and then increased to 165°C in 120 minutes, and held at this temperature for 40 minutes.

[0127] After cooking, the material is diluted to a 10% concentration in a high-concentration diluent. Then, it is diluted to a 1% concentration in a high-speed mixer (20,000 r / min).

[0128] After the slurry is cleared, it is processed by a flat sieve (slit width 0.15mm) and a fiber sieve (50 mesh). The slurry concentration of the sieve is 0.9wt% and that of the perforated sieve is 0.1wt%, which is the final product.

[0129] The properties of the bamboo fiber prepared above are as follows: elastic modulus of 21.46 GPa, zero-pitch tensile strength of 13.32 KN / 15 mm, and hardness of 269.74 MPa.

[0130] Preparation of filter paper

[0131] The bamboo fiber prepared by 100% above was processed into a paper weight of 93 g / m³ at a concentration of 1 wt‰. 2 For wet paper base, (C4H6O2) is used when the wet paper has a dryness of 50%. n2 (Where n2 = 400~800) Emulsion impregnation method for sizing, with a paper base dryness of 95%, the sizing amount is 8g / m². 2 Cur at 155℃ for 6 minutes.

[0132] The properties of the filter paper prepared above are as follows: air permeability 787 mm / s, stiffness 121 mN, and bulk 5.69 cm. 3 / g, average pore size 39.5μm, initial filtration efficiency 12.4%.

[0133] Example 4

[0134] Preparation of bamboo fiber

[0135] Cut the internodes of the large-leaf bamboo (3.5-year growth period) into bamboo strips about 35mm x 25mm in length and width. Take 1kg of the oven-dry weight and soak it in alkaline water with a pH of 8-9 for 30 minutes. Then wash and drain.

[0136] Load the contents into a 15L electric rotary cooker, then add 200g NaOH, 23g Na2SO3, and 1g C. 14 H8O2 and 1g H2NNaSO3 were used for chemical treatment, and water was added at a solid-liquid ratio of 1:4.2. The time and temperature of the chemical treatment were controlled as follows: the temperature was raised from room temperature to 100℃ in 35 minutes, then raised to 145℃ in 50 minutes, and then raised to 165℃ in 110 minutes, and held at this temperature for 40 minutes.

[0137] After cooking, the material is diluted to a 10% concentration in a high-concentration diluent. Then, it is diluted to a 1% concentration in a high-speed mixer (20,000 r / min).

[0138] After the slurry is cleared, it is processed by a flat sieve (slit width 0.15mm) and a fiber sieve (50 mesh). The slurry concentration of the sieve is 0.9wt% and that of the perforated sieve is 0.1wt%, which is the final product.

[0139] The properties of the bamboo fiber prepared above are as follows: elastic modulus of 20.41 GPa, zero-pitch tensile strength of 14.22 KN / 15 mm, and hardness of 250.15 MPa.

[0140] Preparation of filter paper

[0141] The bamboo fiber prepared by 100% above was processed into a paper weight of 93 g / m³ at a concentration of 1 wt‰. 2 For wet paper base, sizing is applied using the (C6H6O·CH2O)x (where x = 5~10) emulsion impregnation method when the wet paper dryness is 50%. When the paper base dryness is 95%, the sizing amount is 8 g / m². 2 Cur at 155℃ for 10 minutes.

[0142] The properties of the filter paper prepared above are as follows: air permeability 552 mm / s, stiffness 163 mN, and bulk 5.68 cm. 3 / g, average pore size 38.3μm, initial filtration efficiency 13.1%.

[0143] Example 5

[0144] Preparation of bamboo fiber

[0145] Select internodes of *Bambusa textilis* (5-year growth period) and *Bambusa serrata* (3-year growth period) and cut them into bamboo strips approximately 35mm x 25mm in length and width. Take 1 ton of oven-dry weight of each bamboo strip and soak and wash them in alkaline water with a pH of 8-9, then drain them.

[0146] Load 25m 3 Steam the balls, then add 450 kg of NaOH and 2 kg of C. 14 H8O2, 2 kg C 12 H 25 SO3Na was used for chemical treatment, with water added at a solid-liquid ratio of 1:3.6. The time and temperature of the chemical treatment were controlled as follows: the temperature was increased from room temperature to 100°C in 40 minutes, then increased to 145°C in 55 minutes, and then increased to 165°C in 110 minutes, and held at this temperature for 35 minutes.

[0147] After cooking, the material is decomposed at a concentration of 8-10% in a high-concentration decomposer. Then, it is further decomposed at a concentration of 1.5% in a high-concentration decomposer (3500 r / min).

[0148] After the sludge removal is completed, it is then treated with a low-concentration slag remover and a 0.20mm slotted screen at a concentration of 1.0%, further treated with a 0.20mm perforated screen at a concentration of 0.2%, and finally concentrated through a 60-mesh inclined screen to obtain the final product.

[0149] The properties (average values) of the bamboo fiber prepared above are as follows: elastic modulus of 24.32 GPa, zero-pitch tensile strength of 16.07 KN / 15 mm, and hardness of 381.97 MPa.

[0150] Preparation of filter paper

[0151] The bamboo fiber prepared by 100% above was processed into a papermaking weight of 93 g / m³ at a concentration of 2 wt‰. 2 For wet paper base, sizing is applied using a C3H4O2 emulsion curtain coating method when the wet paper has a dryness of 50%. When the paper base has a dryness of 95%, the sizing amount is 8 g / m². 2 Cur at 155℃ for 1 minute.

[0152] The properties of the filter paper prepared above are as follows: air permeability is 900 mm / s, stiffness is 176 mN, and bulk is 5.67 cm. 3 / g, average pore size 37.4μm, initial filtration efficiency 16.2%.

[0153] Example 6

[0154] First, cut the internodes of sweet bamboo (6-year growth period) into bamboo strips about 35mm x 25mm in length and width. Take 2 tons of the dry weight of the bamboo strips and soak them in alkaline water with a pH of 8-9 for 30 minutes, then wash and drain them.

[0155] Load 25m 3 Steam the balls, then add 451 kg of NaOH and 1.5 kg of C. 14 H8O2, 1.5Kg C 12 H 25 SO3Na was used for chemical treatment, with water added at a solid-liquid ratio of 1:3.6. The time and temperature of the chemical treatment were controlled as follows: the temperature was increased from room temperature to 100°C in 40 minutes, then increased to 145°C in 55 minutes, and then increased to 165°C in 110 minutes, and held at this temperature for 35 minutes.

[0156] After cooking, the material is decomposed at a concentration of 8-10% in a high-concentration decomposer. Then, it is further decomposed at a concentration of 1.5% in a high-concentration decomposer (3500 r / min).

[0157] After the sludge removal is completed, it is then treated with a low-concentration slag remover and a 0.25mm slotted screen at a concentration of 1.0%, further treated with a 0.10mm perforated screen at a concentration of 0.2%, and finally concentrated through a 60-mesh inclined screen to obtain the final product.

[0158] The properties of the bamboo fiber prepared above are as follows:

[0159] The elastic modulus is 19.36 GPa, the zero-pitch tensile strength is 12.47 KN / 15 mm, and the hardness is 227.12 MPa.

[0160] Preparation of filter paper

[0161] The bamboo fiber prepared by 100% above was processed into a papermaking weight of 93 g / m³ at a concentration of 2 wt‰. 2 For wet paper base, sizing is applied using the C3H4O2 emulsion impregnation method when the wet paper has a dryness of 50%. When the paper base has a dryness of 95%, the sizing amount is 8 g / m². 2 Cur at 155℃ for 5 minutes.

[0162] The properties of the filter paper prepared above are as follows: air permeability 528 mm / s, stiffness 151 mN, and bulk 5.66 cm. 3 / g, average pore size 29.2μm, initial filtration efficiency 11.1%.

[0163] Example 7

[0164] The sheet material, made from 100% flash-dried coniferous pulp, has a basis weight of 93 g / m³. 2 The base paper is tested and found to have an air permeability of 554 mm / s, stiffness of 86 mN, bulk of 5.50 cm³ / g, average pore size of 65.2 μm, and initial filtration efficiency of 9.7%.

[0165] Using the same 70wt% commercial pulp, and blended with 30wt% sweet bamboo pulp (prepared from Example 1 of this invention), and using the same papermaking method to produce the same basis weight, the resulting base paper has an air permeability of 752 mm / s, a stiffness of 114 mN, and a bulk of 5.60 cm. 3 / g, average pore size 54.7μm, initial filtration efficiency 12.3%.

[0166] This embodiment shows that the performance is significantly improved after adding the bamboo pulp fiber of the present invention, indicating that the bamboo pulp fiber of the present invention can replace expensive commercial conifer flash-dried pulp and generate economic benefits.

[0167] Example 8

[0168] The only difference between this invention and Example 2 is that the bamboo used has a growth period of 2 years.

[0169] The properties of the prepared bamboo fiber are as follows: elastic modulus of 18.52 GPa, zero-pitch tensile strength of 15.31 KN / 15 mm, and hardness of 218.63 MPa.

[0170] The properties of the prepared filter paper are as follows: air permeability 503 mm / s, stiffness 124 mN, and bulk 5.46 cm. 3 / g, average pore size 25.1μm, initial filtration efficiency 13.3%.

[0171] Example 9

[0172] The only difference between this invention and Example 1 is that the sweet bamboo used has a growth period of 7 years.

[0173] The properties of the prepared bamboo fiber are as follows: elastic modulus of 18.68 GPa, zero-pitch tensile strength of 12.15 KN / 15 mm, and hardness of 242.14 MPa.

[0174] The properties of the prepared filter paper are as follows: air permeability 586 mm / s, stiffness 173 mN, and bulk 5.69 cm. 3 / g, average pore size 30.2μm, initial filtration efficiency 11.5%.

[0175] Example 10

[0176] The difference between this invention and Example 1 is only that the time and temperature of the chemical treatment are controlled as follows: the temperature is increased from room temperature to 90°C in 35 minutes, then increased to 130°C in 50 minutes, and then increased to 165°C in 100 minutes, and held at this temperature for 30 minutes.

[0177] The properties of the prepared bamboo fiber are as follows: elastic modulus of 23.62 GPa, zero-pitch tensile strength of 14.71 KN / 15 mm, and hardness of 362.22 MPa.

[0178] The properties of the prepared filter paper are as follows: air permeability of 1057 mm / s, stiffness of 190 mN, bulk of 5.68 cm3 / g, average pore size of 36.0 μm, and initial filtration efficiency of 12.2%.

[0179] Example 11

[0180] The difference between this invention and Example 1 is only that the time and temperature of the chemical treatment are controlled as follows: the temperature is increased from room temperature to 110°C in 45 minutes, then increased to 150°C in 60 minutes, and then increased to 165°C in 120 minutes, and held at this temperature for 40 minutes.

[0181] The properties of the prepared bamboo fiber are as follows: elastic modulus of 23.34 GPa, zero-pitch tensile strength of 14.26 KN / 15 mm, and hardness of 352.32 MPa.

[0182] The properties of the prepared filter paper are as follows: air permeability of 1113 mm / s, stiffness of 186 mN, bulk of 5.70 cm3 / g, average pore size of 35.6 μm, and initial filtration efficiency of 11.4%.

[0183] Example 12

[0184] The difference between this invention and Example 1 is only that the time and temperature of the chemical treatment are controlled as follows: the temperature is increased from room temperature to 100°C in 20 minutes, then increased to 145°C in 40 minutes, and then increased to 165°C in 90 minutes, and held at this temperature for 35 minutes.

[0185] The properties of the prepared bamboo fiber are as follows: elastic modulus of 23.92 GPa, zero-pitch tensile strength of 14.89 KN / 15 mm, and hardness of 381.51 MPa.

[0186] The properties of the prepared filter paper are as follows: air permeability of 1028 mm / s, stiffness of 193 mN, bulk of 5.72 cm3 / g, average pore size of 36.3 μm, and initial filtration efficiency of 12.6%.

[0187] Example 13 Preparation of bamboo fiber

[0188] Cut the internodes of the bamboo (7-8 years old) into bamboo strips about 35mm x 25mm in length and width. Take 1kg of the oven-dry weight and soak it in alkaline water with pH 8-9 for 30 minutes. Then wash and drain.

[0189] The contents were placed into a 15L electric rotary cooker, and then 220g NaOH and 23g Na2SO3 were added for chemical treatment. Water was added at a solid-liquid ratio of 1:4. The time and temperature of the chemical treatment were controlled as follows: the temperature was raised from room temperature to 100℃ in 45 minutes, then raised to 145℃ in 50 minutes, then raised to 165℃ in 100 minutes, and held at 165℃ for 30 minutes.

[0190] After cooking, the material is diluted to a concentration of 10% in a high-concentration diluent. After washing, the coarse slurry is diluted to a concentration of 1% in a high-speed mixer (20,000 r / min).

[0191] After the sieving process is completed, the product is processed through a flat sieve (0.15mm slit width) and a fiber sieve (50 mesh) to obtain the final product.

[0192] The properties of the bamboo fiber prepared above are as follows: elastic modulus of 20.35 GPa, zero-pitch tensile strength of 13.78 KN / 15 mm, and hardness of 397.58 MPa.

[0193] Preparation of filter paper

[0194] The bamboo fiber prepared by 100% above was processed into a paper weight of 93 g / m³ at a concentration of 1 wt‰. 2 For wet paper base, sizing is applied using the C3H4O2 emulsion impregnation method when the wet paper has a dryness of 50%. When the paper base has a dryness of 95%, the sizing amount is 8 g / m². 2 Cur at 155℃ for 5 minutes.

[0195] The properties of the filter paper prepared above are as follows: air permeability 442 mm / s, stiffness 137 mN, and bulk 5.61 cm. 3 / g, average pore size 23.3μm, initial filtration efficiency 11.3%.

[0196] Example 14

[0197] Preparation of bamboo fiber

[0198] Bamboo stalks (0.5-year growth period) and sweet bamboo (7-year growth period) were sliced ​​into pieces approximately 35mm x 25mm in length and width. 0.4kg of oven-dry bamboo stalk slices and 0.6kg of oven-dry sweet bamboo stalk slices were mixed and soaked in alkaline water with a pH of 8-9 for 30 minutes, then rinsed and drained.

[0199] The contents were placed into a 15L electric rotary cooker, then 250g NaOH and 1g AQ were added, and water was added at a solid-liquid ratio of 1:4. The processing time and temperature were controlled as follows: the temperature was increased from room temperature to 165℃ in 150 minutes, and then held at 165℃ for 100 minutes.

[0200] After cooking, the material is diluted to a concentration of 10% in a high-concentration diluent. After washing, the coarse slurry is diluted to a concentration of 1% in a high-speed mixer (20,000 r / min).

[0201] After the sieving process is completed, the product is obtained after being processed by a flat sieve (0.15mm slit width) and a fiber sieve (50 mesh).

[0202] Preparation of filter paper

[0203] The bamboo fiber prepared by 100% above was processed into a paper weight of 93 g / m³ at a concentration of 1 wt‰. 2 For wet paper base, sizing is applied using the C3H4O2 emulsion impregnation method when the wet paper has a dryness of 50%. When the paper base has a dryness of 95%, the sizing amount is 8 g / m². 2 Cur at 155℃ for 5 minutes.

[0204] The properties of the filter paper prepared above are as follows: air permeability 326 mm / s, stiffness 110 mN, and bulk 5.51 cm. 3 / g, average pore size 22.5μm, initial filtration efficiency 11.8%.

[0205] Comparative Example 1

[0206] Preparation of bamboo fiber

[0207] Bamboo stalks (0.8-year growth period) are sliced ​​into pieces approximately 35mm x 25mm in length and width. 1kg of the oven-dried weight is soaked in alkaline water with a pH of 8-9 for 30 minutes, then rinsed and drained.

[0208] The contents were placed into a 15L electric rotary cooker, and then 200g NaOH and 50g Na2S were added for chemical treatment. Water was added at a solid-liquid ratio of 1:3.9. The time and temperature of the chemical treatment were controlled as follows: the temperature was raised from room temperature to 160℃ in 120 minutes, and then kept at that temperature for 120 minutes.

[0209] After cooking, the material is diluted to a 10% concentration in a high-concentration diluent. Then, it is diluted to a 1% concentration in a high-speed mixer (20,000 r / min).

[0210] After the sieving process is completed, the product is processed through a flat sieve (0.15mm slit width) and a fiber sieve (50 mesh) to obtain the final product.

[0211] The properties of the bamboo fiber prepared above are as follows: elastic modulus of 9.38 GPa, zero-pitch tensile strength of 13.63 KN / 15 mm, and hardness of 164.35 MPa.

[0212] Preparation of filter paper

[0213] The bamboo fiber prepared by 100% above was processed into a paper weight of 93 g / m³ at a concentration of 1 wt‰. 2 For wet paper base, sizing is applied using the C3H4O2 emulsion impregnation method when the wet paper has a dryness of 50%. When the paper base has a dryness of 95%, the sizing amount is 8 g / m². 2 Cur at 155℃ for 5 minutes.

[0214] The properties of the filter paper prepared above are as follows: air permeability 154 mm / s, stiffness 84 mN, and bulk 5.24 cm. 3 / g, average pore size 15.3μm, initial filtration efficiency 9.2%.

[0215] Comparative Example 2: Preparation of bamboo fiber

[0216] The entire culm of *Phyllostachys edulis* (0.8-year growth period) and *Phyllostachys nigra* (1-year growth period) were sliced ​​into pieces approximately 35mm x 25mm in length and width. 0.5kg of each sample (octane-dry weight) was soaked in alkaline water with a pH of 8-9 for 30 minutes, then rinsed and drained.

[0217] The contents were placed into a 15L electric rotary cooker, and then 250g NaOH and 1g AQ were added for chemical treatment. Water was added at a solid-liquid ratio of 1:4.5. The time and temperature of the chemical treatment were controlled as follows: the temperature was raised from room temperature to 165℃ in 150 minutes, and then kept at 165℃ for 100 minutes.

[0218] After cooking, the material is diluted to a 10% concentration in a high-concentration diluent. Then, it is diluted to a 1% concentration in a high-speed mixer (20,000 r / min).

[0219] After the sieving process is completed, the product is processed through a flat sieve (0.15mm slit width) and a fiber sieve (50 mesh) to obtain the final product.

[0220] Preparation of filter paper

[0221] The bamboo fiber prepared by 100% above was processed into a paper weight of 93 g / m³ at a concentration of 1 wt‰. 2 For wet paper base, sizing is applied using the C3H4O2 emulsion impregnation method when the wet paper has a dryness of 50%. When the paper base has a dryness of 95%, the sizing amount is 8 g / m². 2 Cur at 155℃ for 5 minutes.

[0222] The properties of the filter paper prepared above are as follows: air permeability 172 mm / s, stiffness 76 mN, and bulk 5.46 cm. 3 / g, average pore size 16.8μm, initial filtration efficiency 9.3%.

[0223] Comparative Example 3

[0224] The only difference between this invention and Example 2 is that the bamboo used has a growth period of 0.8 years.

[0225] The properties of the prepared bamboo fiber are as follows: elastic modulus of 9.51 GPa, zero-pitch tensile strength of 11.86 KN / 15 mm, and hardness of 195.74 MPa.

[0226] The properties of the prepared filter paper are as follows: air permeability 386 mm / s, stiffness 96 mN, and bulk 5.26 cm. 3 / g, average pore size 21.2μm, initial filtration efficiency 9.5%.

[0227] Comparative Example 4

[0228] The difference between this comparative example and Example 1 lies in the control of the chemical treatment time and temperature: the temperature was increased from room temperature to 110°C in 35 minutes, and then further increased to 150°C in 50 minutes, and held at this temperature for 30 minutes. After cooking, the uncooked raw materials were cooked much faster and did not fully solidify into a paste.

[0229] Comparative Example 5

[0230] The difference between this comparative example and Example 1 is that the time and temperature of the chemical treatment are controlled as follows: the temperature is raised from room temperature to 100°C within 40 minutes, and then raised to 165°C within 55 minutes, and held at this temperature for 30 to 40 minutes; after the cooking is completed, the raw materials that have not been fully cooked are cooked much faster and have not completely turned into a pulp.

[0231] Comparative Example 6

[0232] The only difference between this invention and Embodiment 1 is that no slotted screen or perforated screen is used.

[0233] As a result, the obtained bamboo fiber is difficult to directly apply to the manufacture of filter paper with air filtration properties.

[0234] The applicant further investigated experiments using slit screens without perforated screens and using perforated screens without slit screens. The results showed that the bamboo fibers prepared by these methods were difficult to manufacture into filter paper with air filtration properties.

[0235] Comparative Example 7

[0236] Cut the internodes of sweet bamboo (3.5 years old) into strips approximately 35mm x 25mm in length and width. Take 1kg of oven-dry bamboo strips and place them into a 15L electric rotary cooker. The cooking process is as follows: 25% alkali (sodium hydroxide), 25% sulfidation, 1:4 liquor ratio, maximum temperature 160℃, heating time 120min, and holding time 120min. After cooking, the material is diluted to a 10% concentration in a high-concentration diluent. Then, it is diluted to a 1% concentration in a high-speed mixer (20000r / min).

[0237] The properties of the bamboo fiber prepared above are as follows: elastic modulus of 12.93 GPa, zero-pitch tensile strength of 11.64 KN / 15 mm, and hardness of 341.19 MPa. Since the pulp was not screened to remove impurities such as cells, it is difficult to manufacture filter paper with air filtration properties.

[0238] Comparative Example 8

[0239] The only difference between this invention and Example 1 is that the seam width is 0.6 mm. The results show that the slurry contains fiber bundles and fiber clumps, and there is no significant effect on removing fiber bundles and fiber clumps compared to the original slurry.

[0240] Comparative Example 9

[0241] The only difference between this invention and Example 1 is that the pore size is 0.5 mm. Results showed that the slurry yield was very low; within the same screening time, the yield decreased by approximately 25%, with many good fibers passing through the sieve unused.

Claims

1. An air filter paper, comprising bamboo fibers prepared by the following method: (1) selecting bamboo materials; selecting bamboo materials; (2) chemical treatment chemically treating the bamboo materials selected in step (1) with chemicals; (3) defibration defibrating the materials obtained in step (2) to obtain coarse pulp; (4) screening screening the coarse pulp obtained in step (3) to obtain bamboo fibers; In step (1), the bamboo materials are selected from sweet bamboo, hanging silk bamboo, small-leaf dragon bamboo, and large-leaf dragon bamboo; the growth period of the bamboo materials is 3-6 years; In step (2), the chemicals include NaOH and at least one selected from H2NNaSO3, C14H8O2, and RSO3Na, wherein R is an alkyl group with 12-16 carbon atoms; the mass of the chemicals is 18-25 wt% of the absolute dry mass of the bamboo materials; the chemical treatment is performed in a reactor under heating; the time and temperature of the chemical treatment are controlled as follows: the temperature is raised from room temperature to 90-110℃ within 20-45 min, then the temperature is continuously raised to 130-150℃ within 40-60 min, then the temperature is continuously raised to 165℃ within 90-120 min, and the temperature is maintained at 165℃ for 30-40 min; In step (3), the defibration includes high-concentration defibration and low-concentration defibration; wherein The high-concentration defibration refers to mechanical treatment of the materials to disperse them by using a high-concentration defibration device, and the concentration of the high-concentration defibration is 8-15 wt%; The rotating speed of the defibration device used in the low-concentration defibration is ≥3000 r / min; The pulp concentration of the low-concentration defibration is ≤4 wt%; In step (4), the screening includes slot screening and hole screening; The pulp concentration of the slot screening is ≤2 wt%, and the slot width is ≤0.5 mm; The pulp concentration of the hole screening is ≤1 wt%, and the hole diameter is ≤0.4 mm; The preparation method further comprises a step of pretreating the selected bamboo materials before the chemical treatment; The pretreatment includes: removing branches and leaves of the bamboo materials, retaining internode segments and slicing, and soaking and washing the bamboo slices in alkaline water with a pH of 8-9, and then draining.

2. The air filter paper according to claim 1, wherein, In step (1), the growth period of the bamboo materials is 3-5 years.

3. The air filter paper according to claim 1, wherein, In step (1), the growth period of the bamboo materials is 3-4 years.

4. The air filter paper according to claim 1, wherein, In step (1), the growth period of the bamboo materials is 3.5 years.

5. The air filtration paper of claim 1, wherein, In step (1), the bamboo materials are single bamboo materials or a mixture of multiple bamboo materials.

6. The air filtration paper of claim 1, wherein, In step (2), the RSO3Na is C12H25SO3Na.

7. The air filtration paper of claim 1, wherein, In step (2), the chemicals further include Na2S and Na2SO3.

8. The air filtration paper of claim 1, wherein, In step (2), the mass of the chemicals is 20-23 wt% of the absolute dry mass of the bamboo materials.

9. The air filtration paper of claim 1, wherein, The heating is steam heating or electric heating; the solid-liquid ratio used in the electric heating is 1:4.0-4.3; the solid-liquid ratio used in the steam heating is 1:3.5-3.8; the reactor is an alkali-resistant medium-low pressure container, including a horizontal tube type continuous digester, a liquid circulation displacement type digester, a steam ball, and a horizontal or vertical rotary digester.

10. The air filter paper according to claim 9, wherein, The solid-liquid ratio used for electric heating is 1:4.2; the solid-liquid ratio used for steam heating is 1:3.

6.

11. The air filtration paper of claim 1, wherein, In step (2), the time and temperature of the chemical treatment are controlled as follows: the temperature is raised from room temperature to 100°C within 35 to 45 minutes, then raised to 145°C within 50 to 60 minutes, and then raised to 165°C within 100 to 120 minutes, and held at this temperature for 30 to 40 minutes.

12. The air filtration paper of claim 1, wherein, In step (2), the time and temperature of the chemical treatment are controlled as follows: the temperature is increased from room temperature to 100°C within 40 minutes, then increased to 145°C within 55 minutes, and then increased to 165°C within 110 minutes, and held at this temperature for 35 minutes.

13. The air filtration paper of claim 1, wherein, In step (3), the concentration of the high-concentration dehydrogenase is 10 wt%.

14. The air filtration paper of claim 1, wherein, In step (4), the slurry concentration of the slotted screen is 0.9wt% to 1.1wt%, and the slot width is 0.15mm to 0.25mm; the slurry concentration of the perforated screen is 0.1wt% to 0.3wt%, and the perforation diameter is 0.1mm to 0.3mm.

15. A method of making the air filtration paper of any one of claims 1 to 14, the method comprising: The bamboo fiber is obtained by processing it through pulping and conveying, wet forming, gluing, and drying. The pulp preparation and feeding process involves preparing the bamboo fiber into a web paper material of a certain concentration, with the concentration of the web paper material being 0.6wt‰ to 6wt‰. The wet forming process involves forming a wet paper base from the paper stock using a wet forming device such as an inclined wire, a rotary wire, or a laboratory sheet forming machine. The adhesive application involves attaching the adhesive to the wet paper base through a penetrating or coating process, so that the wet paper base and the dried paper base have higher physical strength. The drying and shaping process involves passing the glued wet paper base through a drying device, a finishing device, a corrugating device, and a marking device to achieve the drying, flattening, corrugating, and marking effects of the filter paper, resulting in a shaped product. The drying device employs a drying cylinder, drying tunnel, flat plate, or infrared drying method.

16. The method of making according to claim 15, wherein, The concentration of the paper material used for online printing is 1-2 wt‰.

17. The method of making according to claim 15, wherein, The adhesive is selected from: (C11H12O3)n1, where n1 = 4~8; (C6H6O·CH2O)x, where x = 5~10; (C4H6O2)n2, where n2 = 400~800.

18. The method of making according to claim 15, wherein, A through-feeding method is used, with the amount of glue applied being 5 wt% to 10 wt% of the oven-dry weight of the substrate fiber; the glue is applied when the wet paper has a dryness of 35% to 60%.

19. The method of making according to claim 15, wherein, A through-type gluing method is used, with the gluing amount accounting for 8 wt% of the oven-dry weight of the substrate fibers; gluing is applied when the wet paper has a dryness of 50%.

20. The method of making according to claim 15, wherein, A through-type drying cylinder is used.

21. The method of making according to claim 15, wherein, The drying process is carried out in a temperature zone and temperature increment manner, with a preheating zone, a drying zone, a curing zone and a cooling zone; the heating temperature is 110℃~155℃, the curing temperature is 150℃~155℃, and the curing time is 1~10min.

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