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

Abstract

The invention relates to a preparation method of bamboo fibers for filter paper, the filter paper containing the bamboo fibers and a preparation method of the filter paper. The preparation method of the bamboo fiber for the filter paper comprises the following steps: (1) selecting bamboo materials; (2) chemical treatment is conducted, specifically, chemical treatment is conducted on the bamboo wood selected in the step (1) through chemical agents; (3) defibering: defibering the material obtained by chemical treatment in the step (2) to obtain coarse slurry; and (4) screening the coarse pulp obtained in the step (3) to obtain the bamboo fibers. The prepared bamboo fiber has the mechanical property of high elastic modulus, and the air filter paper made of the bamboo fiber has the properties of high breathability, high stiffness and high bulk.

Description

Technical Field

[0001] The invention relates to the technical field of pulping, papermaking and filtering materials, and in particular to a method for preparing bamboo fibers for filter paper, filter paper containing the bamboo fibers and a method for preparing the filter paper. Background Art

[0002] The fibers used in existing wood pulp filter paper bases are mainly flash pulp or mercerized pulp of coniferous / broadleaved wood. From the perspective of the morphological characteristics of the fibers themselves, the diameter of coniferous (or broadleaved) fibers is relatively large. Compared with the small straight fibers, it is inevitable that the filter paper base material has structural characteristics such as larger pore size, lower porosity, and greater thickness at the same quantitative, which leads to lower air permeability and filtration accuracy of the filter paper, smaller effective filtration specific surface area, and more difficulty in accommodating more "folds" in the same volume space. At the same time, the filter material of flash pulp fiber has low stiffness and is easy to deform. During use, the filter element is easy to absorb moisture and swell, resulting in "paper folding", which greatly shortens the service life of the filter element.

[0003] Bamboo is "neither hard nor soft, neither grass nor wood". Its fibers are straight and tough, with a combination of hardness and softness, a large aspect ratio, thick cell walls, small cell cavities, smoothness and stiffness. At present, there are technologies for using bamboo pulp or bamboo fiber to prepare filter paper. Some patent applications mention the use of bamboo fiber to make filter paper, but they only propose the use of bamboo pulp fiber, without involving the special preparation of bamboo pulp fiber, and do not consider the current defects of bamboo pulp fiber, such as miscellaneous cells. In fact, the current chemical pulp of bamboo: the fiber is too soft and has many miscellaneous cells; chemical mechanical pulp: there are too many fiber bundles and many miscellaneous cells. Compared with the preparation of filter paper base materials, its fiber rigidity and fiber fineness or fiber size and other properties are not ideal. The resulting filter paper has poor porosity and stiffness.

[0004] Therefore, it is of far-reaching significance to develop a high-quality stiff bamboo fiber to solve the problems and defects of existing wood pulp filter paper. Summary of the invention

[0005] In order to overcome the defects of the above-mentioned prior art, the present invention provides a method for preparing bamboo fiber for filter paper, filter paper containing the bamboo fiber, and a method for preparing filter paper. The preparation of bamboo fiber in the present invention is guided by the performance of the filter paper base material, such as stiffness, air permeability, thickness, pore size / filtration accuracy, etc. The obtained bamboo fiber is slender / thick / small in the cavity, the fiber cell wall lignin content is high, and the lignin content between the fiber cells is low. In addition, the obtained bamboo fiber has excellent elastic modulus, zero-span tensile strength, and hardness, and is particularly suitable for preparing filter paper. The filter paper prepared by the bamboo fiber prepared by the present invention has the advantages of high air permeability, high stiffness, high filtration accuracy and long life.

[0006] Therefore, an 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 the use of the bamboo fiber.

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

[0009] Still another object of the present invention is to provide a method for preparing the filter paper.

[0010] The above-mentioned object of the present invention is achieved by adopting the following technical scheme.

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

[0012] (1) Material selection

[0013] Select bamboo material;

[0014] (2) Chemical treatment

[0015] Using chemical drugs to chemically treat the bamboo selected in step (1);

[0016] (3) Relief

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

[0018] (4) Screening

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

[0020] Preferably, in step (1), the bamboo material is industrial bamboo material, but is not limited thereto. For example, selected from: Melocanna: Melocanna huilis Kurz; Schizostachyum: Schizostachyum funghomii McClure; Bambusa: Bambusa gibba McClure, Bambusa pervariabilis McClure, Bambusa surrecta, Bambusa textilis McClure; Neosinocalamus: Neosinocalamus affinis; Dendrocalamopsis: Dendrocalamopsis daii Keng, Dendrocalamopsis oldhamii Keng; Dendrocalamus: Dendrocalamus minor, Dendrocalamus barbatus, Dendrocalamus farinosus, Dendrocalamus giganteus Munro, Dendrocalamus latiflorus Munro, Dendrocalamusmembranaceus Munro; Gigantochloa: Gigantochloa verticillata; Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis and Phyllostachys edulis. More preferably, the bamboo material is selected from: Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis. More preferably, the bamboo material is selected from: Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis. More preferably, the bamboo material is selected from: Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis. More preferably, the bamboo material is selected from: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis, Phyllostachys edulis. More preferably, the bamboo material is selected from: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis, 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; further preferably 3 to 4 years; most preferably 3.5 years.

[0022] Preferably, in step (1), the bamboo material is a single bamboo material or a mixture of multiple bamboo materials, preferably a single bamboo material.

[0023] Preferably, in step (2), the chemical drug is selected from RSO3Na (R=C 12 ~C 22 alkyl), 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), R2SO3Na(R2=C 12 ~C 16 alkyl), C 12 H 25 SO3Na or C 18 H 29 NaO3S;

[0025] Preferably, in step (2), the chemical is selected from NaOH, Na2S, C 14 H8O2 and C 12 H 25 SO3Na mixture, the mass ratio is 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 SO3Na mixture, the mass ratio is 195-205:22-24:2.5-3.5:0.45-0.55, the mass ratio is preferably 200:23:3:0.5:0.5; NaOH, Na2S and C 12 H 25 SO3Na mixture, the mass ratio is 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 A mixture of SO3Na, with 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 is 18wt% to 25wt% of the absolute dry mass of the bamboo material, 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 in the electric heating is 1:4.0-4.3, preferably 1:4.2; the solid-liquid ratio used in the steam heating is 1:3.5-3.8, preferably 1:3.6.

[0030] The solid-liquid ratio refers to the ratio of the absolute dry weight of the bamboo to be treated to the total water weight of the reaction system, where the total water weight includes the weight of the bamboo water and the weight of the steam condensed water. If the water weight of the reaction system is insufficient, clean water can be added to achieve the above solid-liquid ratio.

[0031] The bamboo and chemicals can be mixed in a reactor or outside a reactor. In large-scale production, mixing in a reactor is preferred, that is, the required chemicals are respectively prepared into solutions of a certain concentration, and quantitatively pumped into the reactor by a metering pump to be mixed with the bamboo.

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

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

[0034] Preferably, the temperature is raised from room temperature to 100°C in 40 minutes, then further raised to 145°C in 55 minutes, then further raised to 165°C in 110 minutes, and kept at this temperature for 35 minutes.

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

[0036] Preferably, the high-concentration decomposition refers to mechanical treatment through high-concentration decomposition equipment to disperse the materials, and the concentration of the high-concentration decomposition is 8wt% to 15wt%, preferably 10wt%.

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

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

[0039] Preferably, in step (4), the screening includes a slotted screen and a hole screen. The screening is to remove undispersed fiber bundles or fiber clusters, miscellaneous cells, microfibers and thin-walled fragments through the slotted screen and the hole screen.

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

[0041] Preferably, the slurry concentration of the mesh screen is ≤1wt% and the pore size is ≤0.4mm; preferably, the slurry 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 step of adjusting the concentration (dilution or concentration). "Concentration" means that if the concentration of the use section needs to be higher, it needs to be concentrated; otherwise, it needs to be diluted, that is, "diluted or concentrated". When the slurry concentration of each section is not appropriate, it is necessary to "adjust the concentration" or "dilution or concentration". The concentration is to remove free water and fine matter according to the slurry concentration through an inclined screen or a round screen device, and the mesh size used is 45 to 100 mesh, preferably 50 to 80 mesh. Preferably, the preparation method also includes the step of pre-treating the selected bamboo before chemical treatment.

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

[0044] Preferably, the slice specifications are 40mm (length) x 30mm (width), preferably 35mm (length) x 25mm (width).

[0045] Preferably, the washing water is clean water (the source of which may be tap water or homemade cleaner stored water, such as from a river, a well, treated recycled water, etc.) or alkaline water (i.e. water with a pH>7).

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

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

[0048] Preferably, the pre-treated bamboo is stored for no more than 4 weeks for chemical treatment.

[0049] In a specific embodiment, the present invention uses physical methods to pre-treat bamboo. Specifically, after the bamboo is cut, branches and leaves are removed by mechanical and physical methods, preferably the stalk ring, intranode (internode septum), and sheath ring (stalk sheath) of the stalk are removed, the internode segment is retained, and the slicing is performed, and impurities such as mud, sand, and stone, part of the waxy film, and part of the water-soluble substances are removed by water washing.

[0050] Among them, the internode segments can be crushed, cracked, shortened and sliced ​​by a slicer, and the slicing specifications are 40mm (length) x 30mm (width), preferably 35mm (length) x 25mm (width), and the bamboo slices have cracks and bevel cuts.

[0051] The water used for washing is recyclable water, preferably clean water, more preferably alkaline water, i.e. alkaline water with a pH value greater than 7, wherein the alkali in the alkaline water includes all substances capable of producing hydroxide ions, not limited to sodium hydroxide. The water temperature for washing is room temperature, and preferably the water temperature is not lower than room temperature by tail gas heating.

[0052] The pre-treated bamboo chips can be used immediately or stacked as spare materials, and the stacking time shall not exceed 4 weeks.

[0053] The preparation method of the bamboo fiber of the present invention is described in detail below.

[0054] First, bamboo materials are selected and bamboo poles are cut, then the bamboo poles are pretreated (mainly physical methods), and then chemically treated to remove lignin, the obtained material is decomposed to obtain a coarse pulp, and the coarse pulp is screened (mainly physical methods) to obtain bamboo fiber.

[0055] Selection of bamboo materials

[0056] The bamboo material of the present invention is mainly industrial bamboo material, but is not limited thereto. The present invention can be selected from: Melocanna: Melocanna huilis Kurz; Schizostachyum: Schizostachyum funghomiiMcClure; Bambusa: Bambusa gibba McClure, Bambusa pervariabilisMcClure, Bambusa surrecta, Bambusa textilis McClure; Neosinocalamus: Neosinocalamus affinis; Dendrocalamopsis: Dendrocalamopsis daii Keng, Dendrocalamopsis oldhamii Keng; Dendrocalamus: Dendrocalamus minor, Dendrocalamus barbatus, Dendrocalamus farinosus, Dendrocalamus farinosus giganteus Munro, Dendrocalamus latiflorus Munro, Dendrocalamus membranaceus Munro; Gigantochloa: Gigantochloa verticillata; Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis.

[0057] Preferred: Bambusa: Ni bamboo, pole bamboo, oil bamboo, green-skinned bamboo; Male bamboo: hanging bamboo, small-leaf dragon bamboo, large-leaf dragon bamboo, large-leaf dragon bamboo, latissimus, yellow bamboo; Phyllostachys: sweet bamboo, moso bamboo, thick-walled bamboo.

[0058] The most preferred ones are: sweet bamboo, hanging bamboo, small-leaf dragon bamboo, and large-leaf dragon bamboo.

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

[0060] Pretreatment of bamboo stems

[0061] After the bamboo poles are felled, mechanical and physical methods are used to remove branches and leaves. Preferably, the culm ring, intranodes (internode septa), and sheath ring (culm sheath) of the culm are removed, the internode segments are retained and cut into short slices, and impurities such as mud, sand, and stones, some waxy films, and some water-soluble substances are removed by water washing.

[0062] The internode segments can be crushed, cracked, shortened and sliced ​​by a slicer. The preferred slicing specifications are 40mm (length) x 30mm (width), and more preferably 35mm (length) x 25mm (width), and the bamboo slices have cracks and bevel cuts.

[0063] The water used for washing is recyclable recycled water. Clean water is preferred. Alkaline water, water with a pH value greater than 7, is more preferred. The alkali in the alkaline water includes all substances that can produce hydroxide ions, not limited to sodium hydroxide. The water temperature is room temperature, and it is preferred to use tail steam heating to keep the water temperature not lower than room temperature.

[0064] The pre-treated bamboo chips can be used immediately or stacked as spare materials, and the stacking time should not exceed 4 weeks. The bamboo material can be a single bamboo material or a mixture of multiple bamboo materials, preferably a single bamboo material.

[0065] Chemical treatment of bamboo

[0066] The bamboo chips obtained through the pretreatment are mixed with chemicals and then chemically treated in a reactor.

[0067] The chemical drugs used are selected from: RSO3Na (R = C 12 ~C 22 alkyl), H2NNaSO3, NaOH, KOH, Ca(OH)2, Na2S, C 14 H 23 O 10 N3, Na2SO3, C 14 The weight of the chemical is 18 wt% to 25 wt% of the absolute dry weight of the bamboo chips to be treated, preferably 20 wt% to 23 wt%.

[0068] The bamboo chips and chemicals can be mixed inside or outside the reactor. In large-scale production, mixing inside the reactor is preferred, that is, the required chemicals are prepared into solutions of a certain concentration, which are quantitatively pumped into the reactor by a metering pump to be mixed with the bamboo chips.

[0069] The reactor is an alkali-resistant medium-low pressure container, including a horizontal tube continuous digester, a liquid circulation displacement digester, a steam ball, and a horizontal or vertical rotary digester, etc. The heating form of the reactor is steam heating or electric heating.

[0070] The solid-liquid ratio during electric heating is 1:4.0-4.3, preferably 1:4.2. The solid-liquid ratio during steam heating is 1:3.5-3.8, preferably 1:3.6. The solid-liquid ratio refers to the ratio of the absolute dry mass of the bamboo chips to be treated to the total water mass of the reaction system, and the total water mass includes the mass of the water in the bamboo chips and the mass of the steam condensed water.

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

[0072] Relief

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

[0074] The deflaking includes high-concentration deflaking and low-concentration deflaking. The high-concentration deflaking is to disperse the fiber clumps by mechanical treatment through high-concentration deflaking equipment, and the concentration of the high-concentration deflaking is 8wt% to 15wt%, preferably 10wt%.

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

[0076] The low-concentration deflaking is a process of dispersing the fiber bundles through an AC or DC motor deflaking device, the rotation speed of the deflaking device is ≥3000 r / min, and the pulp concentration is ≤4%.

[0077] filter

[0078] The screening includes slot screens and hole screens, through which undispersed fiber bundles or fiber clusters, miscellaneous cells, tiny fibers and thin-walled fragments are removed.

[0079] The slot screen parameters are: slurry concentration ≤ 2wt%, slot width ≤ 0.5mm, preferably slurry concentration 0.9wt%~1.1wt%, slot width 0.15mm~0.25mm; the hole screen parameters are: slurry concentration ≤ 1wt%, pore size ≤ 0.4mm, preferably slurry concentration 0.1wt%~0.3wt%, pore size 0.1mm~0.3mm.

[0080] The screened pulp can be concentrated to obtain refined fibers, i.e. bamboo fibers. The concentration is to remove free water and fine matter according to the pulp concentration requirements through an inclined screen or a round screen device, and the mesh size used is 45 to 100 meshes, preferably 50 to 80 meshes. The obtained refined pulp can be directly used as an air filter paper base material or further dehydrated and dried to make pulp boards or pulp blocks for sale as commercial pulp.

[0081] In another aspect, the present invention provides a use of the bamboo fiber prepared by the above method in preparing air filter paper.

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

[0083] In yet another aspect, the present invention provides a method for preparing the filter paper, which comprises: subjecting the bamboo fibers to slurry flow, wet forming, gluing and drying to obtain the filter paper.

[0084] Preferably, the pulping and flow conveying is to prepare the bamboo fibers into a web-loading paper stock of a certain concentration.

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

[0086] Preferably, the wet forming is to form a wet paper base by passing the web-mounted paper stock through a wet forming device such as an inclined screen, a rotary screen or a laboratory sheeter.

[0087] Preferably, the sizing is to attach the sizing material to the wet paper base by dipping, penetrating or coating, so that the wet paper base has higher physical strength after drying. The sizing material 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) (can be purchased, for example, from Shandong Dongda Polymer Co., Ltd.) Preferably, the concentration of the suspension is 20 wt%-30 wt%, preferably 25 wt%.

[0088] Preferably, penetrating sizing is adopted, and the amount of sizing accounts for 5wt% to 10wt% of the absolute dry mass of the substrate fiber, preferably 8wt%.

[0089] Preferably, the sizing is performed when the wet paper basis dryness is 35% to 60%, preferably 50%.

[0090] The drying and shaping is to pass the wet paper base after gluing through drying equipment, finishing equipment, corrugating equipment and line drawing equipment and other processes to achieve the effects of drying, flattening, corrugating, and line drawing on the filter paper.

[0091] Preferably, the drying equipment can use drying cylinders, drying tunnels, flat plates, infrared and other drying methods, preferably a penetrating drying cylinder.

[0092] Preferably, the drying process is carried out in a temperature zoning and temperature increasing manner, and a preheating zone, a drying zone, a curing zone, and a cooling zone may be provided; the heating temperature is 110°C to 155°C, the curing temperature is 150°C to 155°C, and the curing time is 1 to 10 minutes.

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

[0094] The invention originally prepares bamboo fiber suitable for filter paper, and manufactures filter paper with 100% bamboo fiber and excellent filtering performance by using the bamboo fiber.

[0095] The bamboo fiber prepared by the invention has the mechanical property of high elastic modulus, and the air filter paper made by using the bamboo fiber has the properties of high air permeability, high stiffness and high bulk thickness, and the bamboo fiber with such properties of the invention can be used to prepare single bamboo fiber, that is, filter paper of 100% bamboo fiber.

[0096] The bamboo fiber prepared by the present invention can not only produce wood pulp filter materials, but also manufacture special paper or paper base with high strength, high stiffness, friction resistance and other characteristics. The air filter paper manufactured by the bamboo fiber can solve the problems of low air permeability, low stiffness, easy "paper merging" and the like of existing pure wood pulp filter paper, and can replace flash or mercerized coniferous / broadleaf wood pulp to produce wood pulp filter paper.

[0097] The method for preparing bamboo fiber of the present invention uses less chemical drugs, has low energy consumption of water, electricity and steam, and less wastewater pollution load. The filter paper product made of 100% plant fiber raw materials has the environmental protection feature of easy degradation. The manufactured filter element is particularly suitable for air filtration in engine air intake filtration systems of heavy trucks, engineering machinery, etc. and fresh air systems in automobile interiors, tunnels, building interiors and other places.

[0098] The raw materials used in the present invention are easy to obtain, and the product transformation production can be realized by making appropriate technical transformation in the existing pulp mill or paper mill, with low production cost, good product economy and wide applicability.

[0100] The traditional chemical pulping of plant fibers is guided by the performance of traditional paper, mainly based on the physical strength properties of paper, such as tensile strength, tear strength, bursting strength, etc. The focus is on the fiber morphology (slender / thin wall / large cavity), chemical composition (high cellulose content / low lignin content), biological structure (low non-fiber cell content), and the difficulty of fiber pulping and bleaching and the fiber bonding force of paper. The focus is particularly on the softness coefficient of the fiber, and the technical route of pulping is to remove the overall lignin of the raw material as much as possible. The method for preparing bamboo fiber of the present invention is guided by the performance of the filter paper base material as the target, mainly based on the filtering performance of the filter material, such as stiffness, air permeability, thickness, pore size / filtration accuracy, etc. The focus is on the fiber morphology of slender / thick wall / small cavity and the fiber cell wall with high lignin content. The focus is on the rigidity coefficient of the fiber and the elastic modulus of the extracted fiber. The technical route is to remove the lignin between the fiber cells as much as possible and retain the lignin of the fiber cell wall as much as possible. The technical routes, methods and processes adopted by the two are obviously different. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Figure 1 : Scanning electron microscope image of air filter paper made from bamboo fiber prepared by the present invention. DETAILED DESCRIPTION

[0102] The technical scheme of the present invention is further described below in conjunction with specific examples. The examples are only for illustrating the present invention, not for limiting the scope of the present invention, and the embodiments of the present invention are not limited thereto. Any other changes, substitutions, modifications, simplifications, etc. that do not deviate from the technical ideas and method principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention. It also includes the production of pineapple hemp fiber, Manila hemp fiber, rush fiber, etc., which are substantially expanded according to the technical ideas of this patent, and are substantially expanded for application in filter paper manufacturing, etc.

[0103] Unless otherwise specified, the chemicals and devices used in the following examples are commercially available.

[0104] Example 1

[0105] Preparation of bamboo fiber

[0106] Cut the internodes of sweet bamboo (growing period 3.5 years) into bamboo slices about 35mm x 25mm in length and width, soak 1kg of absolutely dry bamboo slices in alkaline water with a pH value of 8-9 for 30 minutes, wash and drain.

[0107] Put it into a 15L electric rotary cooking pot, then add 220g NaOH, 5g Na2S, 1g C 14 H8O2, 0.5gC 12 H 25 SO3Na, for chemical treatment, add clean water at a solid-liquid ratio of 1:4.2, the time and temperature of the chemical treatment are controlled as follows: raise the temperature from room temperature to 100°C in 40 minutes, then continue to raise the temperature to 145°C in 55 minutes, then continue to raise the temperature to 165°C in 110 minutes, and keep it at this temperature for 35 minutes.

[0108] After the cooking, the material was deflated in a high-concentration deflagrator at a concentration of 10%, and then in a high-speed mixer (20,000 r / min) at a concentration of 1%.

[0109] After the deflaking is completed, the pulp is processed by a flat slot screen (slot width 0.15 mm) and a fiber sifter (50 mesh (0.3 mm)). The pulp concentration of the slot screen is 0.9 wt %, and the pulp concentration of the hole screen is 0.1 wt %.

[0110] The properties of the bamboo fiber prepared as above are as follows: elastic modulus is 25.64 Gpa, zero-span tensile strength is 15.52 KN / 15 mm, and hardness is 379.56 MPa.

[0111] Preparation of filter paper

[0112] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, the C3H4O2 emulsion dipping method is used for gluing, and when the paper base dryness is 95%, the gluing amount is 8g / m 2 , curing at 155℃ for 5min.

[0113] The scanning electron microscope image of the filter paper prepared above is as follows: Figure 1 As shown, the performance is as follows: air permeability is 1298mm / s, stiffness is 209mN, bulk is 5.75cm 3 / g, average pore size 49.5μm, initial filtration efficiency 15.3%.

[0114] Example 2

[0115] Preparation of bamboo fiber

[0116] Cut the internodes of the hanging bamboo (growing period 3.5 years) into bamboo strips about 35mm x 25mm in length and width, soak 1 kg of absolute dry mass in alkaline water with a pH value of 8-9 for 30 minutes, wash and drain.

[0117] Put it into a 15L electric rotary cooking pot, then add 200gNaOH, 23gNa2SO3, 3gNa2S, 0.5gC 14 H8O2, 0.5g C 12 -SO3Na, for chemical treatment, add clean water at a solid-liquid ratio of 1:4, the time and temperature of the chemical treatment are controlled as follows: raise the temperature from room temperature to 100°C in 45 minutes, then continue to raise the temperature to 145°C in 50 minutes, then continue to raise the temperature to 165°C in 100 minutes, and keep warm at this temperature for 30 minutes.

[0118] After the cooking, the material was deflated in a high-concentration deflagrator at a concentration of 10%, and then in a high-speed mixer (20,000 r / min) at a concentration of 1%.

[0119] After the deflaking is completed, the pulp is processed by a flat slot screen (slot width 0.15 mm) and a fiber sifter (50 meshes). The pulp concentration of the slot screen is 1.1 wt %, and the pulp concentration of the hole screen is 0.3 wt %.

[0120] The properties of the bamboo fiber prepared as above are as follows: elastic modulus is 24.24 Gpa, zero-span tensile strength is 17.52 KN / 15 mm, and hardness is 396.72 MPa.

[0121] Preparation of filter paper

[0122] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, the C3H4O2 emulsion dipping method is used for gluing, and when the paper base dryness is 95%, the gluing amount is 8g / m 2 , curing at 155℃ for 5min.

[0123] The properties of the filter paper prepared above are as follows: air permeability is 1074 mm / s, stiffness is 206 mN, and bulk thickness is 5.71 cm 3 / g, average pore size 30.4μm, initial filtration efficiency 18.7%.

[0124] Example 3

[0125] Preparation of bamboo fiber

[0126] Cut the internodes of small-leaf dragon bamboo (growing period 3.5 years) into bamboo strips about 35mm x 25mm in length and width, take 1 kg of absolute dry mass and soak it in alkaline water with a pH value of 8-9 for 30 minutes, then wash and drain.

[0127] Put it into a 15L electric rotary cooking pot, then add 200gNaOH, 22gNa2S, 1gC 12 H 25 SO3Na, for chemical treatment, add clean water at a solid-liquid ratio of 1:4.3, the time and temperature of the chemical treatment are controlled as follows: raise the temperature from room temperature to 100°C in 45 minutes, then continue to raise the temperature to 145°C in 60 minutes, then continue to raise the temperature to 165°C in 120 minutes, and keep it at this temperature for 40 minutes.

[0128] After the cooking, the material was deflated in a high-concentration deflagrator at a concentration of 10%, and then in a high-speed mixer (20,000 r / min) at a concentration of 1%.

[0129] After the deflaking is completed, the pulp is processed by a flat slot screen (slot width 0.15 mm) and a fiber sifter (50 meshes). The pulp concentration of the slot screen is 0.9 wt %, and the pulp concentration of the hole screen is 0.1 wt %.

[0130] The properties of the bamboo fiber prepared as above are as follows: elastic modulus is 21.46 Gpa, zero-span tensile strength is 13.32 KN / 15 mm, and hardness is 269.74 MPa.

[0131] Preparation of filter paper

[0132] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, (C4H6O2) n2 (where n2 = 400-800) emulsion dipping method, the glue amount is 8g / m when the paper base dryness is 95%. 2 , curing at 155℃ for 6min.

[0133] The properties of the filter paper prepared above are as follows: air permeability is 787 mm / s, stiffness is 121 mN, and bulk thickness is 5.69 cm 3 / g, average pore size 39.5μm, initial filtration efficiency 12.4%.

[0134] Example 4

[0135] Preparation of bamboo fiber

[0136] Cut the internodes of large-leaf dragon bamboo (growing period 3.5 years) into bamboo strips about 35mm x 25mm in length and width, take 1 kg of absolute dry mass and soak it in alkaline water with a pH value of 8-9 for 30 minutes, then wash and drain.

[0137] Put it into a 15L electric rotary cooking pot, then add 200gNaOH, 23gNa2SO3, 1gC 14 H8O2, 1gH2NNaSO3, for chemical treatment, supplemented with clean water at a solid-liquid ratio of 1:4.2, the time and temperature of the chemical treatment are controlled as follows: heating from room temperature to 100°C in 35min, then continuing to heat to 145°C in 50min, then continuing to heat to 165°C in 110min, and keeping at this temperature for 40min.

[0138] After the cooking, the material was deflated in a high-concentration deflagrator at a concentration of 10%, and then in a high-speed mixer (20,000 r / min) at a concentration of 1%.

[0139] After the deflaking is completed, the pulp is processed by a flat slot screen (slot width 0.15 mm) and a fiber sifter (50 meshes). The pulp concentration of the slot screen is 0.9 wt %, and the pulp concentration of the hole screen is 0.1 wt %.

[0140] The properties of the bamboo fiber prepared as above are as follows: elastic modulus is 20.41 Gpa, zero-span tensile strength is 14.22 KN / 15 mm, and hardness is 250.15 MPa.

[0141] Preparation of filter paper

[0142] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, the (C6H6O·CH2O)x (where x=5-10) emulsion dipping method is used for gluing, and when the paper base dryness is 95%, the gluing amount is 8g / m 2 , curing at 155℃ for 10min.

[0143] The properties of the filter paper prepared above are as follows: air permeability is 552 mm / s, stiffness is 163 mN, and bulk thickness is 5.68 cm 3 / g, average pore size 38.3μm, initial filtration efficiency 13.1%.

[0144] Example 5

[0145] Preparation of bamboo fiber

[0146] The internodes of hanging bamboo (5 years of growth period) and sweet bamboo (3 years of growth period) were selected and cut into bamboo chips of about 35 mm x 25 mm in length and width. One ton of absolutely dry bamboo chips were soaked in alkaline water with a pH value of 8 to 9, washed, and drained.

[0147] Load 25m 3 Distill the ball, then add 450KgNaOH, 2KgC 14 H8O2, 2Kg C 12 H 25 SO3Na, for chemical treatment, add clean water at a solid-liquid ratio of 1:3.6, the time and temperature of the chemical treatment are controlled as follows: raise the temperature from room temperature to 100°C in 40 minutes, then continue to raise the temperature to 145°C in 55 minutes, then continue to raise the temperature to 165°C in 110 minutes, and keep it at this temperature for 35 minutes.

[0148] After the cooking is completed, the material is deflated in a high-concentration deflagrator at a concentration of 8-10%. Then, it is deflated in a high-concentration deflagrator (3500r / min) at a concentration of 1.5%.

[0149] After the degassing is completed, it is processed by a low-concentration cleaner and a 0.20mm slot screen at a concentration of 1.0%, further processed by a 0.20mm hole screen at a concentration of 0.2%, and finally concentrated by a 60-mesh oblique screen to obtain the product.

[0150] The properties (average values) of the bamboo fiber prepared as above are as follows: elastic modulus is 24.32 Gpa, zero-span tensile strength is 16.07 KN / 15 mm, and hardness is 381.97 MPa.

[0151] Preparation of filter paper

[0152] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, the C3H4O2 emulsion curtain coating method is used for gluing, and when the paper base dryness is 95%, the gluing amount is 8g / m 2 , curing at 155℃ for 1min.

[0153] The properties of the filter paper prepared above are as follows: air permeability is 900 mm / s, stiffness is 176 mN, and bulk thickness is 5.67 cm 3 / g, average pore size 37.4μm, initial filtration efficiency 16.2%.

[0154] Example 6

[0155] First, cut the internodes of sweet bamboo (growing period of 6 years) into bamboo chips with a length and width of about 35mm x 25mm. Take 2 tons of absolutely dry bamboo chips and soak them in alkaline water with a pH of 8-9 for 30 minutes, then wash and drain.

[0156] Load 25m 3 Distill the ball, then add 451KgNaOH, 1.5KgC 14 H8O2, 1.5Kg C 12 H 25 SO3Na, for chemical treatment, add clean water at a solid-liquid ratio of 1:3.6, the time and temperature of the chemical treatment are controlled as follows: raise the temperature from room temperature to 100°C in 40 minutes, then continue to raise the temperature to 145°C in 55 minutes, then continue to raise the temperature to 165°C in 110 minutes, and keep it at this temperature for 35 minutes.

[0157] After the cooking is completed, the material is deflated in a high-concentration deflagrator at a concentration of 8-10%. Then, it is deflated in a high-concentration deflagrator (3500r / min) at a concentration of 1.5%.

[0158] After the degassing is completed, it is processed through a low-concentration cleaner and a 0.25mm slot screen at a concentration of 1.0%, further processed through a 0.10mm hole screen at a concentration of 0.2%, and finally concentrated through a 60-mesh oblique screen to obtain the product.

[0159] The properties of the bamboo fiber prepared above are as follows:

[0160] The elastic modulus is 19.36Gpa, the zero-span tensile strength is 12.47KN / 15mm, and the hardness is 227.12MPa.

[0161] Preparation of filter paper

[0162] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, the C3H4O2 emulsion dipping method is used for gluing, and when the paper base dryness is 95%, the gluing amount is 8g / m 2 , curing at 155℃ for 5min.

[0163] The properties of the filter paper prepared above are as follows: air permeability is 528 mm / s, stiffness is 151 mN, and bulk thickness is 5.66 cm 3 / g, average pore size 29.2μm, initial filtration efficiency 11.1%.

[0164] Example 7

[0165] 100% flash dried pulp of a certain commercial softwood is used to make a paper with a basis weight of 93g / m 2 The original paper base. After testing, the air permeability of the original paper base is 554mm / s, the stiffness is 86mN, the bulk is 5.50cm3 / g, the average pore size is 65.2μm, and the initial filtration efficiency is 9.7%.

[0166] The commercial pulp was also used at 70 wt% and mixed with 30 wt% sweet bamboo pulp (prepared in Example 1 of the present invention). The same papermaking method was used to make the same quantitative paper. The obtained base paper had an air permeability of 752 mm / s, a stiffness of 114 mN, and a bulk thickness of 5.60 cm. 3 / g, average pore size 54.7μm, initial filtration efficiency 12.3%.

[0167] This example 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 the expensive commercial softwood flash-dried pulp and generate economic benefits.

[0168] Example 8

[0169] The difference between the present invention and Example 2 is that the growth period of the hanging bamboo used is 2 years.

[0170] The properties of the prepared bamboo fiber are as follows: elastic modulus is 18.52 Gpa, zero-span tensile strength is 15.31 KN / 15 mm, and hardness is 218.63 MPa.

[0171] The properties of the prepared filter paper are as follows: air permeability is 503 mm / s, stiffness is 124 mN, and bulk thickness is 5.46 cm 3 / g, average pore size 25.1μm, initial filtration efficiency 13.3%.

[0172] Example 9

[0173] The difference between the present invention and Example 1 is that the growth period of the sweet bamboo used is 7 years.

[0174] The properties of the prepared bamboo fiber are as follows: elastic modulus is 18.68 Gpa, zero-span tensile strength is 12.15 KN / 15 mm, and hardness is 242.14 MPa.

[0175] The properties of the prepared filter paper are as follows: air permeability 586 mm / s, stiffness 173 mN, bulk thickness 5.69 cm 3 / g, average pore size 30.2μm, initial filtration efficiency 11.5%.

[0176] Example 10

[0177] The only difference between the present invention and Example 1 is that the time and temperature of the chemical treatment are controlled as follows: heating from room temperature to 90°C in 35 minutes, then continuing to heat to 130°C in 50 minutes, then continuing to heat to 165°C in 100 minutes, and keeping at this temperature for 30 minutes.

[0178] The properties of the prepared bamboo fiber are as follows: elastic modulus is 23.62 Gpa, zero-span tensile strength is 14.71 KN / 15 mm, and hardness is 362.22 MPa.

[0179] The properties of the prepared filter paper are as follows: air permeability is 1057 mm / s, stiffness is 190 mN, bulk thickness is 5.68 cm3 / g, average pore size is 36.0 μm, and initial filtration efficiency is 12.2%.

[0180] Embodiment 11

[0181] The only difference between the present invention and Example 1 is that the time and temperature of the chemical treatment are controlled as follows: heating from room temperature to 110°C in 45 minutes, then continuing to heat to 150°C in 60 minutes, then continuing to heat to 165°C in 120 minutes, and keeping at this temperature for 40 minutes.

[0182] The properties of the prepared bamboo fiber are as follows: elastic modulus is 23.34 Gpa, zero-span tensile strength is 14.26 KN / 15 mm, and hardness is 352.32 MPa.

[0183] The properties of the prepared filter paper are as follows: air permeability is 1113 mm / s, stiffness is 186 mN, bulk thickness is 5.70 cm3 / g, average pore size is 35.6 μm, and initial filtration efficiency is 11.4%.

[0184] Example 12

[0185] The only difference between the present invention and Example 1 is that the time and temperature of the chemical treatment are controlled as follows: heating from room temperature to 100°C in 20 minutes, then continuing to heat to 145°C in 40 minutes, then continuing to heat to 165°C in 90 minutes, and keeping at this temperature for 35 minutes.

[0186] The properties of the prepared bamboo fiber are as follows: elastic modulus is 23.92 Gpa, zero-span tensile strength is 14.89 KN / 15 mm, and hardness is 381.51 MPa.

[0187] The properties of the prepared filter paper are as follows: air permeability is 1028 mm / s, stiffness is 193 mN, bulk thickness is 5.72 cm3 / g, average pore size is 36.3 μm, and initial filtration efficiency is 12.6%.

[0188] Example 13 Preparation of bamboo fiber

[0189] The internodes of hanging bamboo (7-8 years of growth period) are cut into bamboo strips with a length and width of about 35 mm x 25 mm. 1 kg of absolute dry mass is soaked in alkaline water with a pH value of 8-9 for 30 minutes, then washed and drained.

[0190] Load into a 15L electric rotary cooking pot, then add 220gNaOH and 23gNa2SO3 for chemical treatment, add clean water at a solid-liquid ratio of 1:4, and the time and temperature of the chemical treatment are controlled as follows: raise the temperature from room temperature to 100°C in 45min, then raise the temperature to 145°C within 50min, then raise the temperature to 165°C in 100min, and keep warm at 165°C for 30min.

[0191] After the cooking is completed, the material is deflated at a concentration of 10% in a high-concentration deflagrator. After cleaning, the coarse slurry is deflagrated at a concentration of 1% in a high-speed mixer (20,000 r / min).

[0192] After the deflaking is completed, it is processed through a flat slit screen (slit width 0.15mm) and a fiber sifter (50 meshes) to obtain the product.

[0193] The properties of the bamboo fiber prepared as above are as follows: elastic modulus is 20.35 Gpa, zero-span tensile strength is 13.78 KN / 15 mm, and hardness is 397.58 MPa.

[0194] Preparation of filter paper

[0195] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, the C3H4O2 emulsion dipping method is used for gluing, and when the paper base dryness is 95%, the gluing amount is 8g / m 2 , curing at 155℃ for 5min.

[0196] The properties of the filter paper prepared above are as follows: air permeability is 442 mm / s, stiffness is 137 mN, and bulk thickness is 5.61 cm 3 / g, average pore size 23.3μm, initial filtration efficiency 11.3%.

[0197] Embodiment 14

[0198] Preparation of bamboo fiber

[0199] The whole stems of southern bamboo (growing period 0.5 years) and sweet bamboo (growing period 7 years) were sliced ​​into about 35 mm x 25 mm in length and width. 0.4 kg of absolute dry mass of southern bamboo slices and 0.6 kg of absolute dry mass of sweet bamboo slices were mixed and soaked in alkaline water with a pH of 8-9 for 30 minutes, washed and drained.

[0200] Put it into a 15L electric rotary cooking pot, then add 250g NaOH, 1g AQ, and add clean water at a solid-liquid ratio of 1:4. The treatment time and temperature are controlled as follows: heat from room temperature to 165℃ in 150min, and keep at 165℃ for 100min.

[0201] After the cooking is completed, the material is deflated in a high-concentration deflagrator at a concentration of 10%. After cleaning, the coarse slurry is deflagrated in a high-speed mixer (20,000 r / min) at a concentration of 1%.

[0202] After the deflaking is completed, it is processed by a flat slit screen (slit width 0.15mm) and a fiber sifter (50 meshes) to obtain the product.

[0203] Preparation of filter paper

[0204] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, the C3H4O2 emulsion dipping method is used for gluing, and when the paper base dryness is 95%, the gluing amount is 8g / m 2 , curing at 155℃ for 5min.

[0205] The properties of the filter paper prepared above are as follows: air permeability is 326 mm / s, stiffness is 110 mN, and bulk thickness is 5.51 cm 3 / g, average pore size 22.5μm, initial filtration efficiency 11.8%.

[0206] Comparative Example 1

[0207] Preparation of bamboo fiber

[0208] The whole stem of the bamboo (growing period 0.8 years) was sliced ​​into about 35 mm x 25 mm in length and width. 1 kg of the absolute dry mass was soaked in alkaline water with a pH of 8 to 9 for 30 minutes, washed and drained.

[0209] Load into a 15L electric rotary cooking pot, then add 200gNaOH and 50gNa2S for chemical treatment, add clean water at a solid-liquid ratio of 1:3.9, and the time and temperature of the chemical treatment are controlled as follows: heat from room temperature to 160°C in 120min, and then keep warm for 120min.

[0210] After the cooking, the material was deflated in a high-concentration deflagrator at a concentration of 10%, and then in a high-speed mixer (20,000 r / min) at a concentration of 1%.

[0211] After the deflaking is completed, it is processed through a flat slit screen (slit width 0.15mm) and a fiber sifter (50 meshes) to obtain the product.

[0212] The properties of the bamboo fiber prepared as above are as follows: elastic modulus is 9.38 Gpa, zero-span tensile strength is 13.63 KN / 15 mm, and hardness is 164.35 MPa.

[0213] Preparation of filter paper

[0214] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, the C3H4O2 emulsion dipping method is used for gluing, and when the paper base dryness is 95%, the gluing amount is 8g / m 2 , curing at 155℃ for 5min.

[0215] The properties of the filter paper prepared above are as follows: air permeability is 154 mm / s, stiffness is 84 mN, and bulk thickness is 5.24 cm 3 / g, average pore size 15.3μm, initial filtration efficiency 9.2%.

[0216] Comparative Example 2 Preparation of bamboo fiber

[0217] The whole stems of Nanzhu (growing period 0.8 years) and Nizhu (growing period 1 year) were sliced ​​into about 35 mm x 25 mm in length and width. 0.5 kg of the absolute dry mass of each was soaked in alkaline water with a pH of 8-9 for 30 minutes, washed and drained.

[0218] Load into a 15L electric rotary cooking pot, then add 250g NaOH and 1g AQ for chemical treatment, add clean water at a solid-liquid ratio of 1:4.5, and the time and temperature of the chemical treatment are controlled as follows: heat from room temperature to 165°C in 150min, and then keep warm at 165°C for 100min.

[0219] After the cooking, the material was deflated in a high-concentration deflagrator at a concentration of 10%, and then in a high-speed mixer (20,000 r / min) at a concentration of 1%.

[0220] After the deflaking is completed, it is processed through a flat slit screen (slit width 0.15mm) and a fiber sifter (50 meshes) to obtain the product.

[0221] Preparation of filter paper

[0222] 100% of the bamboo fiber prepared above was used to make a 93g / m 2 Wet paper base, when the wet paper dryness is 50%, the C3H4O2 emulsion dipping method is used for gluing, and when the paper base dryness is 95%, the gluing amount is 8g / m 2 , curing at 155℃ for 5min.

[0223] The properties of the filter paper prepared above are as follows: air permeability is 172 mm / s, stiffness is 76 mN, and bulk thickness is 5.46 cm 3 / g, average pore size 16.8μm, initial filtration efficiency 9.3%.

[0224] Comparative Example 3

[0225] The only difference between the present invention and Example 2 is that the growth period of the hanging bamboo used is 0.8 years.

[0226] The properties of the prepared bamboo fiber are as follows: elastic modulus is 9.51 Gpa, zero-span tensile strength is 11.86 KN / 15 mm, and hardness is 195.74 MPa.

[0227] The properties of the prepared filter paper are as follows: air permeability is 386 mm / s, stiffness is 96 mN, and bulk thickness is 5.26 cm 3 / g, average pore size 21.2μm, initial filtration efficiency 9.5%.

[0228] Comparative Example 4

[0229] 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 110°C in 35 minutes, then further raised to 150°C in 50 minutes, and kept at this temperature for 30 minutes. After the cooking is completed, the raw materials that have not been cooked are much faster and have not been completely pulped.

[0230] Comparative Example 5

[0231] 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, then further raised to 165°C within 55 minutes, and kept at this temperature for 30 to 40 minutes; the raw materials that are not cooked after the cooking are cooked much faster and are not completely pulped.

[0232] Comparative Example 6

[0233] The only difference between the present invention and Example 1 is that no slot screen or hole screen is used.

[0234] As a result, the obtained bamboo fiber is difficult to be directly applied to the manufacture of filter paper with air filtration performance.

[0235] The applicant further studied the experiment of using a slotted screen instead of a hole screen, and using a hole screen instead of a slotted screen. The results showed that the bamboo fibers prepared by these methods are difficult to manufacture filter paper with air filtering performance.

[0236] Comparative Example 7

[0237] Cut the internodes of sweet bamboo (growing period 3.5 years) into bamboo slices of about 35mm x 25mm in length and width, take 1kg of the absolutely dry bamboo slices and put them into a 15L electric rotary cooking pot. The cooking process is: use 25% alkali (sodium hydroxide), 25% sulfidation, 1:4 liquid ratio, maximum temperature 160℃, heating time 120min, and heat preservation time 120min for cooking. After the cooking is completed, the material is deflated at a concentration of 10% in a high-concentration deflagrator. Then, it is deflagrated at a concentration of 1% in a high-speed mixer (20000r / min).

[0238] The properties of the bamboo fiber prepared above are as follows: elastic modulus is 12.93 Gpa, zero-span tensile strength is 11.64 KN / 15 mm, and hardness is 341.19 MPa. If the pulp is not screened to remove impurities such as cells, it is difficult to manufacture filter paper with air filtration performance.

[0239] Comparative Example 8

[0240] The difference between the present invention and Example 1 is that the slit width is 0.6 mm. The results show that the slurry contains fiber bundles and fiber clusters, and there is no obvious effect of removing the fiber bundles and fiber clusters compared with the original slurry.

[0241] Comparative Example 9

[0242] The only difference between the present invention and Example 1 is that the aperture is 0.5 mm. The results show that the pulp yield is very low, and within the same screening time, the yield is reduced by about 25%, and many good fibers pass through the sieve holes and are not used.

Claims

1. A method for preparing bamboo fiber for filter paper, the method comprising the following steps: (1) Material selection Select bamboo material; (2) Chemical treatment Using chemical drugs to chemically treat the bamboo selected in step (1); (3) Relief The material obtained by the chemical treatment in step (2) is decomposed to obtain a coarse slurry; (4) Screening The coarse pulp obtained in step (3) is screened to obtain bamboo fibers.

2. The preparation method according to claim 1, wherein In step (1), the bamboo material is selected from: Melocanna huilis Kurz; Schizostachyum schizostachyum: Schizostachyum funghomii McClure; Bambusa bambuses: Bambusa gibba McClure, Bambusa pervariabilis McClure, Bambusa surrecta, Bambusa textilis McClure; Neosinocalamus nematodes: Neosinocalamus affinis; Dendrocalamopsis daii Keng, Dendrocalamopsis oldhamii Keng; Dendrocalamus nematodes: Dendrocalamus minor, Dendrocalamus barbatus, Dendrocalamus serrata farinosus, Dendrocalamusgiganteus Munro, Dendrocalamus latiflorus Munro, Dendrocalamusmembranaceus Munro; Gigantochloa: Gigantochloa verticillata; Phyllostachys: Phyllostachys flexuosa, Phyllostachys edulis and Phyllostachys edulis; Preferably, the bamboo material is selected from: Bamboo genus: Ni bamboo, supporting bamboo, oil bamboo, green bamboo; Bamboo genus: hanging bamboo, small-leaf dragon bamboo, large-leaf dragon bamboo, large-leaf dragon bamboo, latifolia bamboo, yellow bamboo; Phyllostachys genus: sweet bamboo, moso bamboo, thick-walled moso bamboo; Preferably, the bamboo material is selected from: sweet bamboo, hanging bamboo, small-leaf dragon bamboo, and large-leaf dragon bamboo; 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; further preferably 3 to 4 years; most preferably 3.5 years; Preferably, in step (1), the bamboo material is a single bamboo material or a mixture of multiple bamboo materials, preferably a single bamboo material.

3. The preparation method according to claim 1 or 2, wherein In step (2), the chemical drug is selected from RSO3Na (R = C 12 ~C 22 alkyl), H2NNaSO3, NaOH, KOH, Ca(OH)2, Na2S, C 14 H 23 O 10 N3, Na2SO3 and C 14 One or more of H8O2; Preferably, the RSO3Na is R1SO3Na (R1=C 14 ~C 22 alkyl), R2SO3Na(R2=C 12 ~C 16 alkyl), C 12 H 25 SO3Na or C 18 H 29 NaO3S; Preferably, in step (2), the mass of the chemical is 18wt% to 25wt% of the absolute dry mass of the bamboo material, preferably 20wt% to 23wt%; Preferably, in step (2), the chemical treatment is carried out in a reactor under heating; Preferably, the heating is steam heating or electric heating; Preferably, the solid-liquid ratio used in the electric heating is 1:4.0-4.3, preferably 1:4.2; the solid-liquid ratio used in the steam heating is 1:3.5-3.8, preferably 1:3.6; Preferably, the reactor is an alkali-resistant medium- and low-pressure container, including a horizontal tube continuous digester, a liquid circulation displacement digester, a steam ball, and a horizontal or vertical rotary digester.

4. The preparation method according to any one of claims 1 to 3, wherein In step (2), the time and temperature of the chemical treatment are controlled as follows: the temperature is raised from room temperature to 90-110° C. within 20-45 minutes, then the temperature is further raised to 130-150° C. within 40-60 minutes, then the temperature is further raised to 165° C. within 90-120 minutes, and the temperature is kept at this temperature for 30-40 minutes; preferably: the temperature is raised from room temperature to 100° C. within 35-45 minutes, then the temperature is further raised to 145° C. within 50-60 minutes, then the temperature is further raised to 165° C. within 100-120 minutes, and the temperature is kept at this temperature for 30-40 minutes; Preferably, the temperature is raised from room temperature to 100°C in 40 minutes, then further raised to 145°C in 55 minutes, then further raised to 165°C in 110 minutes, and kept at this temperature for 35 minutes.

5. The preparation method according to any one of claims 1 to 4, wherein In step (3), the degassing includes high-concentration degassing and low-concentration degassing; Preferably, the high-concentration decomposition refers to mechanical treatment by high-concentration decomposition equipment to disperse the material, and the concentration of the high-concentration decomposition is 8wt% to 15wt%, preferably 10wt%; Preferably, the rotation speed of the degassing equipment used in the low-concentration degassing is ≥3000r / min; Preferably, the concentration of the low-concentration deflaking slurry is ≤4wt%.

6. The preparation method according to any one of claims 1 to 5, wherein In step (4), the screening includes a slotted screen and a hole screen; Preferably, the slurry concentration of the slotted screen is ≤2wt% and the slot width is ≤0.5mm; preferably, the slurry concentration is 0.9wt% to 1.1wt% and the slot width is 0.15mm to 0.25mm; Preferably, the slurry concentration of the mesh screen is ≤1wt% and the pore size is ≤0.4mm; preferably, the slurry concentration is 0.1wt% to 0.3wt% and the pore size is 0.1mm to 0.3mm.

7. The preparation method according to any one of claims 1 to 6, wherein The preparation method further comprises the step of pre-treating the selected bamboo material before chemical treatment; Preferably, the pretreatment comprises: removing branches and leaves from the bamboo, retaining internodes and slicing, and washing and removing impurities; Preferably, the pre-treated bamboo is stored for no more than 4 weeks for chemical treatment.

8. Use of the bamboo fiber prepared by the method according to any one of claims 1 to 7 in preparing air filter paper.

9. An air filter paper comprising bamboo fiber prepared by the method according to any one of claims 1 to 7.

10. A method for preparing the air filter paper according to claim 9, the method comprising: The bamboo fibers are subjected to slurry mixing, wet forming, gluing and drying to obtain the bamboo fibers; Preferably, the slurry flow is to prepare the bamboo fiber into a web-loading paper material of a certain concentration; Preferably, the concentration of the web stock is 0.6wt‰ to 6wt‰, preferably 1 to 2wt‰; Preferably, the wet forming is to form a wet paper base by passing the web-mounted paper stock through a wet forming device such as an inclined screen, a rotary screen or a laboratory sheeter; Preferably, the gluing is to attach the glue to the wet paper base by dipping, penetrating or coating, so that the wet paper base has higher physical strength after drying; wherein the glue 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), (C4H6O2) n2 (n2=400-800); Preferably, penetrating glue is used, and the glue amount accounts for 5wt% to 10wt% of the absolute dry mass of the substrate fiber, preferably 8wt%; Preferably, the gluing is performed when the wet paper basis dryness is 35% to 60%, preferably 50%; The drying and shaping is to pass the wet paper base after gluing through the processes of drying equipment, finishing equipment, corrugating equipment and marking equipment to achieve the effects of drying, flattening, corrugating, marking and other effects of the filter paper; Preferably, the drying equipment can be dried by drying cylinder, drying tunnel, flat plate, infrared, etc., preferably a penetrating drying cylinder; Preferably, the drying process is carried out in a temperature zoning and temperature increasing manner, and a preheating zone, a drying zone, a curing zone, and a cooling zone may be provided; the heating temperature is 110°C to 155°C, the curing temperature is 150°C to 155°C, and the curing time is 1 to 10 minutes.

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