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

Abstract

The present invention relates to a preparation method for a bamboo fiber for filter paper, filter paper containing the bamboo fiber, and a preparation method for the filter paper. The preparation method for a bamboo fiber for filter paper of the present invention comprises the following steps: (1) material selection: selecting bamboo; (2) chemical treatment: using a chemical agent to perform chemical treatment on the bamboo selected in step (1); (3) defibering: defibering the material obtained by means of the chemical treatment in step (2), to obtain coarse pulp; and (4) screening: screening the coarse pulp obtained in step (3) to obtain the bamboo fiber. The bamboo fiber prepared in the present invention has the mechanical property of a high elastic modulus, and the air filter paper manufactured using the bamboo fiber has the properties of high air permeability, high stiffness and high bulk.

Description

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

[0001] The present application relates to the technical fields of pulping and papermaking and filter material, in particular to a preparation method of bamboo fiber for filter paper, a filter paper containing the bamboo fiber and a preparation method of filter paper. BACKGROUND

[0002] The existing filter paper base mainly uses needle leaf wood / broadleaf wood flash pulp or its mercerized pulp. From the morphological characteristics of the fiber itself, the diameter of needle leaf wood (or broadleaf wood) fiber is larger, which inevitably makes the filter paper base material have larger pore size, lower porosity and larger thickness at the same amount, and other structural characteristics, thereby resulting in lower air permeability and filtering precision of the filter paper, smaller effective filtering specific surface area, and more difficult to accommodate 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, and the filter core is easy to absorb moisture and swell during use, resulting in "paper merging", which greatly shortens the service life of the filter core.

[0003] Bamboo is neither grass nor wood, and its fiber is straight and tough, with a large length-width ratio, thick cell wall, small cell cavity, smoothness and stiffness. Currently, there are technologies for preparing filter paper using bamboo pulp or bamboo fiber. Some patent applications mention using bamboo fiber to manufacture filter paper, but they only propose using bamboo pulp fiber and do not involve special preparation of bamboo pulp fiber, nor do they consider the defects of current bamboo pulp fiber, such as mixed cells. In fact, the chemical pulp of current bamboo has the following defects: too soft fiber, too many mixed cells; the chemical mechanical pulp has the following defects: too many fiber bundles, too many mixed cells. Compared with the preparation of filter paper base material, the fiber rigidity and fiber fineness or titer of the bamboo fiber are not ideal. The obtained filter paper has poor porosity and stiffness.

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

[0005] To overcome the defects of the prior art, the present application provides a preparation method of bamboo fiber for filter paper, a filter paper containing the bamboo fiber and a preparation method of the filter paper. The bamboo fiber prepared in the present application is targeted at the performance of filter paper base material, such as stiffness, air permeability, thickness, pore size / filtering accuracy, etc. The obtained bamboo fiber is long and thin, has high lignin content in fiber cell wall, low lignin content between fiber cells, and excellent elastic modulus, zero-distance tensile strength and hardness, and is particularly suitable for preparing filter paper. The filter paper prepared from the bamboo fiber prepared in the present application has the advantages of high air permeability, high stiffness, high filtering accuracy and long service life.

[0006] Therefore, an object of the present application is to provide a preparation method of bamboo fiber for filter paper.

[0007] Another object of the present application is to provide the use of the above-mentioned bamboo fiber.

[0008] Still another object of the present application is to provide a filter paper containing the above-mentioned bamboo fiber.

[0009] Still another object of the present application is to provide a preparation method of the above-mentioned filter paper.

[0010] The above-mentioned objects of the present application are achieved by using the following technical solutions.

[0011] In one aspect, the present application provides a preparation method of bamboo fiber for filter paper, which comprises the following steps:

[0012] (1) Material selection

[0013] Selecting bamboo material;

[0014] (2) Chemical treatment

[0015] Chemically treating the bamboo material selected in step (1) with chemical drugs;

[0016] (3) Dispersing

[0017] Dispersing the material obtained in step (2) to obtain coarse pulp;

[0018] (4) Screening

[0019] Screening the coarse pulp obtained in step (3) to obtain bamboo fiber.

[0020] Preferably, in step (1), the bamboo material is industrial bamboo material, but not limited to. 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, Dendrocalamus membranaceus Munro; Gigantochloa: Gigantochloa verticillata; Phyllostachys: phyllostachys flexuosa, Phyllostachys edulis and Phyllostachys edulis. More preferably, the bamboo material is selected from: Bambusa: Bambusa gibba, Bambusa pervariabilis, Bambusa surrecta, Bambusa textilis; Dendrocalamus: Dendrocalamus minor, Dendrocalamus barbatus, Dendrocalamus farinosus, Dendrocalamus giganteus, Dendrocalamus latiflorus, Dendrocalamus membranaceus; Phyllostachys: phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis. Most preferably, the bamboo material is selected from: phyllostachys flexuosa, Dendrocalamus minor, Dendrocalamus barbatus, Dendrocalamus giganteus.

[0021] Preferably, in step (1), the bamboo material is more than 2 years old, 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 medicine is selected from one or more of 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 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 medicine is selected from a mixture of NaOH, Na2S, C 14 H8O2 and C 12 H 25 SO3Na in a mass ratio of 195-205:4-6:0.8-1.2:0.45-0.55, preferably 200:5:1:0.5; a mixture of NaOH, Na2SO3, Na2S, C 14 H8O2 and C 12 H 25 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; a mixture of NaOH, Na2S and C 12 H 25 SO3Na in a mass ratio of 195-205:21-23:0.8-1.2, preferably 200:22:1; a mixture of NaOH, Na2SO3, C 14 H8O2 and H2NSO3Na in a mass ratio of 195-205:22-24:0.8-1.2:0.8-1.2, preferably 200:23:1:1; a mixture of NaOH, C 14 H8O2 and C 12 H 25 SO3Na in 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 medicine is 18wt% to 25wt%, preferably 20wt% to 23wt%, of the dry mass of the bamboo.

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

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

[0029] Preferably, the electric heating uses a solid-liquid ratio of 1:4.0 to 4.3, preferably 1:4.2; and the steam heating uses a solid-liquid ratio of 1:3.5 to 3.8, preferably 1:3.6.

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

[0031] The mixing of the bamboo and the chemical medicine can be carried out in the reactor or outside the reactor. In large-scale production, it is preferable to use in-reactor mixing, that is, the chemical medicine required is prepared into a solution of a certain concentration, which is pumped into the reactor by a metering pump for mixing with the bamboo.

[0032] Preferably, the reactor is an alkali-resistant medium-low pressure vessel, including a horizontal tube continuous digester, a medicine 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: the temperature is raised from room temperature to 90-110°C within 20-45 min, then the temperature is continuously raised to 130-150°C within 40-60 min, then the temperature is continuously raised to 165°C within 90-120 min, and the temperature is maintained at 165°C for 30-40 min; preferably: the temperature is raised from room temperature to 100°C within 35-45 min, then the temperature is continuously raised to 145°C within 50-60 min, then the temperature is continuously raised to 165°C within 100-120 min, and the temperature is maintained at 165°C for 30-40 min.

[0034] Preferably: the temperature is raised from room temperature to 100°C within 40 min, then the temperature is continuously raised to 145°C within 55 min, then the temperature is continuously raised to 165°C within 110 min, and the temperature is maintained at 165°C for 35 min.

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

[0036] Preferably, the high consistency defibration means mechanical treatment by high consistency defibration equipment to disperse the material, and the consistency of the high consistency defibration is 8wt% to 15wt%, preferably 10wt%.

[0037] Preferably, the rotational speed of the defibration equipment used in the low consistency defibration is ≥3000r / min.

[0038] Preferably, the consistency of the slurry in the low consistency defibration is ≤4wt%.

[0039] Preferably, in step (4), the screening includes slot screen and hole screen. The screening removes un-dispersed fiber bundles or fiber groups, miscellaneous cells, microfibers, and thin-wall fragments, etc. by slot screen and hole screen.

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

[0041] Preferably, the consistency of the slurry in the hole screen is ≤1wt%, and the hole diameter is ≤0.4mm; preferably, the consistency of the slurry is 0.1wt% to 0.3wt%, and the hole diameter is 0.1mm to 0.3mm.

[0042] Preferably, the preparation method further includes the step of adjusting the consistency (dilution or concentration). "Concentration" means that if the consistency of the used section needs to be higher, it needs to be concentrated; otherwise, it needs to be diluted, i.e. "dilution or concentration". When the consistency of the slurry in each section is not suitable, it needs to be "adjusted" or "diluted or concentrated". The concentration is to remove free water and fine materials by inclined screen or round screen device, and the mesh number used is 45 to 100, preferably 50 to 80. Preferably, the preparation method further includes the step of pretreating the selected bamboo before chemical treatment.

[0043] Preferably, the pretreatment includes removing branches and leaves of the bamboo, retaining internode sections and slicing, and washing to remove impurities.

[0044] Preferably, the slicing specification is 40mm (length) x 30mm (width), preferably 35mm (length) x 25mm (width).

[0045] Preferably, the water used for washing is clean water (its source can be tap water or self-made cleaner storage water, such as from rivers, wells, treated recycled water, etc.) 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 temperature of the water used for washing is normal temperature.

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

[0049] In one embodiment, the present application uses physical method to pretreat the bamboo. Specifically, after the bamboo is cut, the branches and leaves are removed by mechanical physical method, preferably the culm ring, node (node interval), and sheath ring (culm sheath) of the culm stem are removed, the node interval is reserved, the bamboo is sliced, and the mud, sand, stone, and other impurities, part of the wax membrane, and part of the water-soluble substances are removed by water washing.

[0050] In the method, the node interval section is pressed, fractured, cut, and sliced by a slicing machine, and the sliced bamboo has a size of 40 mm (length) x 30 mm (width), preferably 35 mm (length) x 25 mm (width), and has a broken crack and an inclined cut.

[0051] The water used for water washing is recycled water, preferably clean water, and more preferably alkaline water with pH > 7. The alkali in the alkaline water includes all substances that can generate hydroxyl ions, and is not limited to sodium hydroxide. The water used for water washing is at room temperature, and the water temperature is not lower than room temperature by using tail gas heating.

[0052] The pretreated bamboo can be used immediately or stacked as standby material, and the stacking time is no more than 4 weeks.

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

[0054] First, the bamboo is selected and cut, then the bamboo is pretreated (mainly by physical method), and then the bamboo is chemically treated to remove lignin. The obtained material is defibered to obtain coarse pulp, the coarse pulp is screened (mainly by physical method), and the bamboo fiber is obtained.

[0055] Selection of bamboo

[0056] The bamboo material of the present application is mainly industrial bamboo material, but is not limited thereto. It can be selected from the group consisting of 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, Dendrocalamus membranaceus Munro, Gigantochloa: Gigantochloa verticillata, Phyllostachys: phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis.

[0057] Preferably: Bambusa: Bambusa gibba, Bambusa pervariabilis, Bambusa surrecta, Bambusa textilis; Dendrocalamus: Dendrocalamus minor, Dendrocalamus barbatus, Dendrocalamus farinosus, Dendrocalamus giganteus, Dendrocalamus latiflorus, Dendrocalamus membranaceus; Phyllostachys: phyllostachys flexuosa, Phyllostachys edulis, Phyllostachys edulis.

[0058] Most preferably: phyllostachys flexuosa, Dendrocalamus minor, Dendrocalamus barbatus, Dendrocalamus farinosus.

[0059] The cutting period of the bamboo material is more than 2 years, 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] Pre-treatment of the bamboo pole

[0061] The bamboo pole is cut down and the branches and leaves are removed by mechanical and physical methods. Preferably, the culm ring, node (node spacing), and sheath ring (culm sheath) of the culm stem are removed, the internode section is retained and cut short and sliced, and mud, sand, stone, and other impurities, part of the wax membrane, and part of the water-soluble substances are removed by water washing.

[0062] The internode section can be crushed, fractured, cut short, and sliced by a slicing machine. The preferred slicing specification is 40 mm (length) x 30 mm (width), and the more preferred slicing specification is 35 mm (length) x 25 mm (width) with a broken crack and an inclined cut.

[0063] The water used for washing is recyclable and reusable water. Preferably, it is clean water. More preferably, it is alkaline water with a pH greater than 7, wherein the alkali includes all substances that can generate hydroxyl ions, not limited to sodium hydroxide. The water temperature is normal temperature, and preferably, tail steam heating is used to make the water temperature not lower than normal temperature.

[0064] The pretreated bamboo pieces can be used immediately or stored as standby material, and the storage 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 material

[0066] The pretreated bamboo pieces are mixed with chemical drugs and subjected to chemical treatment in a reactor.

[0067] The chemical drugs used are selected from the group consisting of RSO3Na (R = C 12 ~ C 22 alkyl), H2NNaSO3, NaOH, KOH, Ca(OH)2, Na2S, C 14 H 23 O 10 N3, Na2SO3, C 14 H8O2. The mass of the chemical drugs is 18wt% to 25wt%, preferably 20wt% to 23wt%, of the absolute dry mass of the bamboo pieces to be treated.

[0068] The mixing of the bamboo pieces and the chemical drugs can be carried out in the reactor or outside the reactor. In large-scale production, it is preferable to mix them in the reactor, that is, to prepare solutions of the required chemical drugs with certain concentrations, and to pump them into the reactor in a certain amount by a metering pump to mix with the bamboo pieces.

[0069] 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. The heating form of the reactor is steam heating or electric heating.

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

[0071] The time and temperature of the chemical treatment are controlled as follows: the temperature is raised from room temperature to 90-110°C in 20-45 min, then the temperature is raised to 130-150°C in 40-60 min, then the temperature is raised to 165°C in 90-120 min, and the temperature is maintained at 165°C for 30-40 min; preferably, the temperature is raised from room temperature to 100°C in 35-45 min, then the temperature is raised to 145°C in 50-60 min, then the temperature is raised to 165°C in 100-120 min, and the temperature is maintained at 165°C for 30-40 min; more preferably, the temperature is raised from room temperature to 100°C in 40 min, then the temperature is raised to 145°C in 55 min, then the temperature is raised to 165°C in 110 min, and the temperature is maintained at 165°C for 35 min. The temperature is raised in a smooth and incremental manner.

[0072] Defibration

[0073] After the chemical treatment, the concentrated black liquor and the pulp are extracted, and the material is adjusted to a suitable concentration for defibration.

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

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

[0076] The low-concentration defibration is a process of dispersing fiber bundles by an alternating current or direct current motor defibration device, and the rotational speed of the defibration device is ≥3000r / min, and the pulp concentration is ≤4%.

[0077] Screening

[0078] The screening includes slot screening and hole screening. The slot screening and the hole screening remove undispersed fiber bundles or fiber clumps, impurity cells, small fibers, and thin-walled fragments, etc.

[0079] The parameters of the slotted screen are: pulp consistency ≤ 2wt%, slot width ≤ 0.5mm, preferably pulp consistency 0.9wt%-1.1wt%, slot width 0.15mm-0.25mm; the parameters of the hole screen are: pulp consistency ≤ 1wt%, hole diameter ≤ 0.4mm, preferably pulp consistency 0.1wt%-0.3wt%, hole diameter 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 materials by an inclined screen or a cylinder screen device according to the pulp consistency requirement, and the mesh number used is 45-100, preferably 50-80. The obtained refined pulp can be directly used as an air filtration paper base material or further dehydrated and dried to produce pulp board or pulp block as a commodity pulp for sale.

[0081] In another aspect, the present application provides a use of the bamboo fibers prepared by the above method in preparing air filtration paper.

[0082] In still another aspect, the present application provides a filtration paper comprising the bamboo fibers prepared by the above method. In the present application, the filtration paper can comprise 100% of the bamboo fibers prepared by the above method, or can comprise a part of the bamboo fibers prepared by the above method.

[0083] In still another aspect, the present application provides a preparation method of the above filtration paper, which comprises: preparing the bamboo fibers into a certain consistency of a web material by a pulp preparation flow, forming a wet paper base by a wet forming method, applying a sizing agent, and drying and shaping, to obtain the filtration paper.

[0084] Preferably, the pulp preparation flow is to prepare the bamboo fibers into a web material of a certain consistency.

[0085] Preferably, the consistency of the web material is 0.6wt‰-6wt‰, preferably 1-2wt‰.

[0086] Preferably, the wet forming method is to make the web material pass through a wet forming device such as an inclined screen, a cylinder screen or a laboratory sheet former, to make a wet paper base.

[0087] Preferably, the sizing is to attach a sizing agent to the wet paper base by immersion, penetration or coating, so that the wet paper base and the dried paper base have higher physical strength. The sizing agent is selected from: C3H6N6 emulsion, C3H4O2 emulsion, C 19 H 42 BrN, (C 11 H 12 O3) n1 (wherein, n1=4-8), (C6H6O·CH2O)x(x=5-10) (which can be purchased, for example, from Shandong Yinglang Chemical Co., Ltd.), (C4H6O2) n2(n2=400-800) (commercially available, for example, from Shandong Dongda Polymer Co., Ltd.). Preferably, the concentration of the suspension is 20wt%-30wt%, preferably 25wt%.

[0088] Preferably, the sizing is performed by penetration, and the sizing amount is 5wt%-10wt% of the dry mass of the base material fibers, preferably 8wt%.

[0089] Preferably, the sizing is performed when the moisture content of the wet paper base is 35%-60%, preferably 50%.

[0090] The drying and setting is a process of drying, smoothing, creping, and marking the filter paper by passing the sized wet paper base through an oven, a finishing device, a creping device, and a marking device.

[0091] Preferably, the oven can be a drying cylinder, a drying channel, a flat plate, or an infrared dryer, and preferably a penetration drying cylinder.

[0092] Preferably, the drying process is performed by temperature zoning and temperature increment, and can include a preheating zone, a drying and curing zone, and a cooling zone. The heating temperature is 110°C-155°C, the curing temperature is 150°C-155°C, and the curing time is 1-10min.

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

[0094] The present application originally prepares bamboo fibers suitable for filter paper, and uses the bamboo fibers to manufacture 100% bamboo fiber filter paper with excellent filtering performance.

[0095] The bamboo fibers prepared by the present application have high elastic modulus, and the air filter paper manufactured using the bamboo fibers has high air permeability, high stiffness, and high bulk thickness. The bamboo fibers with such properties can be used to manufacture single bamboo fiber, i.e., 100% bamboo fiber filter paper.

[0096] The bamboo fibers prepared by the present application can be used to manufacture not only wood pulp filter materials, but also special papers or paper bases with high strength, high stiffness, and friction resistance. The air filter paper manufactured using the bamboo fibers can solve the problems of low air permeability, low stiffness, and easy "paper merging" of existing pure wood pulp filter paper, and can replace flash or mercerized coniferous / broadleaf wood pulp to manufacture wood pulp filter paper.

[0097] The method for preparing the bamboo fibers has low chemical drug consumption, low energy consumption of water, electricity, and steam, and low wastewater pollution load. The filter paper products manufactured using 100% plant fiber raw materials have the environmental protection feature of easy degradation. The manufactured filter core is particularly suitable for air filtration of new air systems in heavy trucks, engineering machinery, and other engine intake filtration systems, and in car interiors, tunnels, and building interiors.

[0098] The raw materials used in the application are easy to obtain, and the product transformation production can be realized by making appropriate technical modifications in the existing pulp mill or paper mill, the production cost is low, the product is economical and suitable for wide application.

[0099] The application can make substantial contributions to new quality productivity, double carbon strategy and bamboo pulp paper integration.

[0100] The traditional chemical pulping of plant fibers is targeted at the performance of traditional paper, mainly based on the physical strength performance of paper, such as tensile strength, tear strength, burst strength, etc., the focus is on the fiber morphology (slim / wall thin / cavity large), chemical composition (high cellulose content / low lignin content), biological structure (low non-fiber cell content) and fiber beating, bleaching difficulty and fiber bonding force of papermaking, and the softness coefficient of the fiber is particularly significant, and the technical route is to remove as much lignin as possible from the raw material. The method for preparing bamboo fibers in the application is targeted at the performance of filter paper base material, mainly based on the filtration performance of filter material, such as stiffness, air permeability, thickness, pore size / filter precision, etc., the focus is on the fiber morphology of slim / wall thick / small cavity and high lignin content fiber cell wall, the rigidity coefficient of the fiber and the elastic modulus of the extracted fiber are significant, and the technical route is to remove as much lignin as possible between fiber cells and retain as much lignin as possible in the fiber cell wall. The technical route, method and process adopted by the two are obviously different. BRIEF DESCRIPTION OF DRAWINGS

[0101] Figure 1: Scanning electron micrograph of air filter paper prepared from bamboo fibers prepared by the application. DETAILED DESCRIPTION

[0102] The technical solutions of the application are further described below in combination with specific embodiments. The embodiments are only for illustrating the application, and are not intended to limit the scope of the application, and the embodiments of the application are not limited thereto. Any changes, substitutions, modifications, simplifications, etc. made without departing from the technical ideas and method principles of the application shall be equivalent replacement ways, and are included in the protection scope of the application. And include the preparation of pineapple hemp fibers, manila hemp fibers, cattail fibers, etc. substantially expanded, and applied to 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 fibers

[0106] The internodes of sweet bamboo (3.5 years old) were cut into bamboo pieces with a length of about 35 mm and a width of about 25 mm. 1 kg of the bamboo pieces with absolute dry weight were soaked in alkaline water with a pH of 8-9 for 30 minutes, washed and drained.

[0107] A 15 L electric heating rotary digester was charged with 220 g of NaOH, 5 g of Na2S, 1 g of C 14 H8O2, and 0.5 g of C 12 H 25 SO3Na, and water was added to make the solid-liquid ratio 1:4.2. The chemical treatment was controlled in terms of time and temperature as follows: the temperature was raised from room temperature to 100°C in 40 minutes, then raised to 145°C in 55 minutes, then raised to 165°C in 110 minutes, and maintained at this temperature for 35 minutes.

[0108] After the cooking was completed, the material was defibrated in a high-concentration defibrator at a concentration of 10%. Then, the material was defibrated in a high-speed mixer (20000 r / min) at a concentration of 1%.

[0109] After the defibration was completed, the material was treated by a flat seam screen (seam width 0.15 mm) and a fiber screen separator (50 mesh (0.3 mm)), and the pulp concentration of the seam screen was 0.9 wt% and the pulp concentration of the hole screen was 0.1 wt%, and the bamboo fibers were obtained.

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

[0111] Preparation of filter paper

[0112] The bamboo fibers prepared above were used to make filter paper at a concentration of 1 wt‰, and the basis weight of the filter paper was 93 g / m 2 at a dryness of 50%. The filter paper was sized by a C3H4O2 emulsion impregnation method at a dryness of 95%, and the sizing amount was 8 g / m 2 at 155°C for 5 minutes.

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

[0114] Example 2

[0115] Preparation of bamboo fibers

[0116] The internodes of the hanging silk bamboo (3.5 years of growth period) are cut into bamboo pieces with a length of about 35 mm and a width of about 25 mm, 1 kg of absolute dry mass is soaked in alkaline water with a pH of 8-9 for 30 minutes, and then washed and drained.

[0117] A 15 L electric heating rotary digester is loaded, and then 200 g of NaOH, 23 g of Na2SO3, 3 g of Na2S, and 0.5 g of C 14 H8O2, 0.5 g of C 12 -SO3Na are added to perform chemical treatment, and clean water is added to make the solid-liquid ratio 1:4, and the time and temperature of the chemical treatment are controlled as follows: the temperature is raised from room temperature to 100°C in 45 min, then the temperature is continuously raised to 145°C in 50 min, then the temperature is continuously raised to 165°C in 100 min, and the temperature is kept at 165°C for 30 min.

[0118] After the cooking is completed, the material is defibrated in a high-concentration defibrator at a concentration of 10%.

[0119] After the defibration is completed, the material is treated by a flat seam screen (seam width 0.15 mm) and a fiber screen separator (50 mesh), the pulp concentration of the seam screen is 1.1 wt%, and the pulp concentration of the hole screen is 0.3 wt%, and the bamboo fibers are obtained.

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

[0121] Preparation of filter paper

[0122] The bamboo fibers prepared above are used to make a filter paper with a basis weight of 93 g / m 2 at a concentration of 1 wt‰, and the filter paper is sized by a C3H4O2 emulsion impregnation method when the wet paper basis has a dryness of 50%, and the sizing amount is 8 g / m 2 when the paper basis has a dryness of 95%, and the filter paper is cured at 155°C for 5 min.

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

[0124] Example 3

[0125] Preparation of bamboo fibers

[0126] The internodes of the small-leaf dragon bamboo (3.5 years of growth period) are cut into bamboo pieces with a length of about 35 mm and a width of about 25 mm, 1 kg of absolute dry mass is soaked in alkaline water with a pH of 8-9 for 30 minutes, and then washed and drained.

[0127] A 15L electric heating rotary digester was charged, then 200g NaOH, 22g Na2S, Ig C 12 H 25 SO3Na were added for chemical treatment, the solid-liquid ratio was 1:4.3, the time and temperature of the chemical treatment were controlled as follows: from normal temperature to 100°C in 45 min, then to 145°C in 60 min, then to 165°C in 120 min, and kept at this temperature for 40 min.

[0128] After the digestion was completed, the material was defibrated in a high consistency defibrator at 10% consistency. Then, it was defibrated in a high speed mixer (20000 r / min) at 1% consistency.

[0129] After the defibration was completed, it was treated by a flat screen (slot width 0.15 mm) and a fiber screen separator (50 mesh), the pulp consistency of the flat screen was 0.9 wt%, and the pulp consistency of the hole screen was 0.1 wt%, and the product was obtained.

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

[0131] Preparation of filter paper

[0132] The bamboo fiber prepared above was used to make filter paper at 100% and 1 wt% consistency, the basis weight of the filter paper was 93 g / m 2 at a dryness of 50%, and the filter paper was sized by a (C4H6O2) n2 emulsion sizing method (wherein n2=400-800), the sizing amount was 8 g / m 2 at a dryness of 95%, and the filter paper was cured at 155°C for 6 min.

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

[0134] Example 4

[0135] Preparation of bamboo fiber

[0136] The internodes of Dendrocalamus latiflorus (growing period 3.5 years) were cut into bamboo pieces with a length of about 35 mm and a width of about 25 mm, 1 Kg of absolute dry mass was soaked in alkaline water with a pH of 8-9 for 30 min, and then washed and drained.

[0137] A 15L electric heating rotary digester was charged, then 200g NaOH, 23g Na2SO3, Ig C 14H2SO4, lg H2NNaSO3, to be chemically treated, with water added at a solid-liquid ratio of 1:4.2, the time and temperature of the chemical treatment being controlled as follows: from normal temperature to 100°C in 35 min, then to 145°C in 50 min, then to 165°C in 110 min, and kept at this temperature for 40 min.

[0138] After the cooking is completed, the material is defibrated at a concentration of 10% in a high-concentration defibrator. Then, it is defibrated at a concentration of 1% in a high-speed mixer (20000 r / min).

[0139] After the defibration is completed, it is treated by a flat-plate slot screen (slot width 0.15 mm) and a fiber screen separator (50 mesh), the pulp concentration of the slot screen being 0.9 wt%, and the pulp concentration of the hole screen being 0.1 wt%, to obtain the product.

[0140] The bamboo fiber prepared above has the following properties: elastic modulus 20.41 Gpa, zero-distance tensile strength 14.22 KN / 15 mm, and hardness 250.15 MPa.

[0141] Preparation of filter paper

[0142] The bamboo fiber prepared above is used to make a filter paper at a concentration of 1 wt‰, the basis weight of the filter paper being 93 g / m 2 The filter paper is impregnated with a (C6H6O·CH2O)x (where x = 5-10) emulsion at a wet paper basis, when the wet paper dryness is 50%, and the amount of the emulsion is 8 g / m 2 when the paper dryness is 95%.

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

[0144] Example 5

[0145] Preparation of bamboo fiber

[0146] The internodes of the hanging-silk bamboo (growing period 5 years) and the sweet bamboo (growing period 3 years) are each cut into bamboo pieces with a length of about 35 mm and a width of about 25 mm, and 1 ton of the bamboo pieces with an absolute dry mass is soaked and washed in alkaline water with a pH of 8-9, and then drained.

[0147] The bamboo pieces are loaded into a 25 m 3 steaming ball, then 450 Kg of NaOH and 2 Kg of C 14 H2SO4, 2 Kg of C 12 H 25SO3Na 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.

[0148] 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).

[0149] 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.

[0150] 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.

[0151] Preparation of filter paper

[0152] The bamboo fiber prepared by 100% above was processed into a 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.

[0153] 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%.

[0154] Example 6

[0155] 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.

[0156] 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 25SO3Na, and water was added to make the solid-liquid ratio 1:3.6, and the chemical treatment was carried out at the following time and temperature: from room temperature to 100°C in 40 min, then to 145°C in 55 min, and then to 165°C in 110 min, and kept at this temperature for 35 min.

[0157] After the cooking, the material was treated by a high consistency defibrator at a consistency of 8-10%. Then, the material was treated by a high consistency defibrator (3500 r / min) at a consistency of 1.5%.

[0158] After the defibration, the material was treated by a low consistency rag eliminator at a consistency of 1.0%, then by a 0.25 mm gap screen, and then by a 0.10 mm hole screen at a consistency of 0.2%, and finally by a 60 mesh inclined screen to obtain the product.

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

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

[0161] Preparation of filter paper

[0162] The bamboo fiber prepared above was used to make a filter paper at a consistency of 2 wt‰ and a basis weight of 93 g / m 2 The filter paper was impregnated with a C3H4O2 emulsion when the wet paper had a dryness of 50%, and the amount of the emulsion on the paper was 8 g / m 2 when the paper had a dryness of 95%, and the paper was cured at 155°C for 5 min.

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

[0164] Example 7

[0165] A commercial softwood flash dry pulp was used to make a base paper at a basis weight of 93 g / m 2 . The air permeability of the base paper was 554 mm / s, the stiffness was 86 mN, the bulk was 5.50 cm3 / g, the average pore size was 65.2 μm, and the initial filtration efficiency was 9.7%.

[0166] The commercial pulp was used to make a base paper at a basis weight of 93 g / m 3 / g, average pore size 54.7 μm, initial filtration efficiency 12.3%.

[0167] This example shows that the performance of the bamboo pulp fiber added in the application is obviously improved, which shows that the bamboo pulp fiber of the application can replace the expensive commercial coniferous flash dry pulp, and economic benefits are generated.

[0168] Example 8

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

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

[0171] The performance of the prepared filter paper is as follows: air permeability is 503 mm / s, stiffness is 124 mN, bulkiness is 5.46 cm 3 / g, average pore size 54.7 μm, initial filtration efficiency 12.3%.

[0172] Example 9

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

[0174] The performance of the prepared bamboo fiber is as follows: elastic modulus is 18.52 Gpa, zero-distance tensile strength is 15.31 KN / 15 mm, hardness is 218.63 MPa.

[0175] The performance of the prepared filter paper is as follows: air permeability is 503 mm / s, stiffness is 124 mN, bulkiness is 5.46 cm 3 / g, average pore size 54.7 μm, initial filtration efficiency 12.3%.

[0176] Example 10

[0177] The difference between the application and Example 1 is only that the time and temperature control of chemical treatment is: from room temperature to 90℃ in 35 min, then continue to heat to 130℃ in 50 min, then continue to heat to 165℃ in 100 min, and keep the temperature for 30 min.

[0178] The performance of the prepared bamboo fiber is as follows: elastic modulus is 18.52 Gpa, zero-distance tensile strength is 15.31 KN / 15 mm, hardness is 218.63 MPa.

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

[0180] Example 11

[0181] The present application differs from Example 1 only in that the time and temperature control of chemical treatment is as follows: from normal temperature to 110°C in 45 min, then continue to heat to 150°C in 60 min, then continue to heat to 165°C in 120 min, and keep the temperature for 40 min.

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

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

[0184] Example 12

[0185] The present application differs from Example 1 only in that the time and temperature control of chemical treatment is as follows: from normal temperature to 100°C in 20 min, then continue to heat to 145°C in 40 min, then continue to heat to 165°C in 90 min, and keep the temperature for 35 min.

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

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

[0188] Preparation of bamboo fiber

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

[0190] A 15L electric heating rotary digester was charged, then 220g NaOH, 23g Na2SO3 were added for chemical treatment, clean water was added to make the solid-liquid ratio 1:4, the time and temperature of the chemical treatment were controlled as follows: from room temperature to 100°C in 45min, then to 145°C in 50min, then to 165°C in 100min, and kept at 165°C for 30min.

[0191] After the digestion was completed, the material was defibrated in a high-concentration defibrator at a concentration of 10%, and after washing, the coarse slurry was defibrated in a high-speed mixer (20000r / min) at a concentration of 1%.

[0192] After defibration, it was treated by a flat plate slot screen (slot width 0.15mm) and a fiber screen separator (50 mesh) to obtain the product.

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

[0194] Preparation of filter paper

[0195] The bamboo fiber prepared above was used to make filter paper at a concentration of 1wt‰, and the basis weight was 93g / m 2 The wet paper base was sized by a C3H4O2 emulsion impregnation method when the wet paper dryness was 50%, and the sizing amount was 8g / m 2 when the paper base dryness was 95%, and the curing temperature was 155°C for 5min.

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

[0197] Example 14

[0198] Preparation of bamboo fiber

[0199] The south bamboo (growth period 0.5 years) and sweet bamboo (growth period 7 years) were cut into pieces with a length of about 35mm x 25mm. 0.4Kg of absolute dry mass of south bamboo pieces and 0.6Kg of absolute dry mass of sweet bamboo pieces were mixed and soaked in alkaline water with a pH of 8-9 for 30min, washed and drained.

[0200] A 15L electric heating rotary digester was charged, then 250g NaOH, 1g AQ were added, and clean water was added to make the solid-liquid ratio 1:4. The time and temperature of the treatment were controlled as follows: from room temperature to 165°C in 150min, and kept at 165°C for 100min.

[0201] After the cooking, the material was defibrated in a high consistency defibrator at 10% consistency. After washing, the pulp was defibrated in a high speed mixer (20000 r / min) at 1% consistency.

[0202] After defibration, the material was treated by a flat screen (0.15 mm gap) and a fiber screen (50 mesh) to obtain the product.

[0203] Preparation of filter paper

[0204] The bamboo fibers prepared above were used to make filter paper at 1 wt% consistency and basis weight 93 g / m 2 The wet paper was sized by C3H4O2 emulsion at 50% dryness, and the sizing amount was 8 g / m 2 at 95% dryness.

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

[0206] Comparative Example 1

[0207] Preparation of bamboo fibers

[0208] The bamboo (0.8 years old) was cut into pieces of about 35 mm x 25 mm. 1 Kg of dry material was soaked in alkaline water (pH 8-9) for 30 minutes, washed and drained.

[0209] The material was loaded into a 15 L electric heating rotary digester, and 200 g of NaOH and 50 g of Na2S were added for chemical treatment. The solid-liquid ratio was 1:3.9, and the chemical treatment was carried out at the following conditions: from room temperature to 160°C in 120 minutes, and then holding for 120 minutes.

[0210] After the cooking, the material was defibrated in a high consistency defibrator at 10% consistency. Then, the pulp was defibrated in a high speed mixer (20000 r / min) at 1% consistency.

[0211] After defibration, the material was treated by a flat screen (0.15 mm gap) and a fiber screen (50 mesh) to obtain the product.

[0212] The properties of the bamboo fibers prepared above were as follows: elastic modulus 9.38 Gpa, zero distance tensile strength 13.63 KN / 15 mm, and hardness 164.35 MPa.

[0213] Preparation of filter paper

[0214] The bamboo fibers prepared above were used to make filter paper at a concentration of 100% by weight at a basis weight of 93 g / m 2 The wet paper base was sized using C3H4O2 emulsion at a paper wetness of 50%, and the sizing amount was 8 g / m 2 at a paper dryness of 95% after curing at 155°C for 5 min.

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

[0216] Preparation of bamboo fibers in Comparative Example 2

[0217] The whole stems of Phyllostachys pubescens (0.8 years of growth) and Dendrocalamus latiflorus (1 year of growth) were sliced into pieces with a length of about 35 mm x 25 mm. 0.5 kg of each of the dry materials was soaked in alkaline water with a pH of 8-9 for 30 min, washed, and drained.

[0218] The materials were loaded into a 15 L electric heating rotary digester, and then 250 g of NaOH and 1 g of AQ were added for chemical treatment. The materials were supplemented with clean water at a solid-to-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°C in 150 min, and then the temperature was maintained at 165°C for 100 min.

[0219] After the digestion was completed, the materials were defiberized at a concentration of 10% in a high-concentration defiberizer. Then, the materials were defiberized at a concentration of 1% in a high-speed mixer (20000 r / min).

[0220] After the defiberization was completed, the materials were treated by a flat-plate slot screen (slot width of 0.15 mm) and a fiber screen separator (50 mesh) to obtain the bamboo fibers.

[0221] Preparation of filter paper

[0222] The bamboo fibers prepared above were used to make filter paper at a concentration of 100% by weight at a basis weight of 93 g / m 2 The wet paper base was sized using C3H4O2 emulsion at a paper wetness of 50%, and the sizing amount was 8 g / m 2 at a paper dryness of 95% after curing at 155°C for 5 min.

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

[0224] Comparative Example 3

[0225] The difference between the present application and Example 2 is that the Phyllostachys nigra used in the present application has a growth period of 0.8 years.

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

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

[0228] Comparative Example 4

[0229] The difference between this comparative example and Example 1 is that the time and temperature control of chemical treatment is as follows: from normal temperature to 110°C in 35 min, then continue to heat to 150°C in 50 min, and keep the temperature for 30 min. The raw material is cooked much faster after the end of cooking, and is not completely pulped.

[0230] Comparative Example 5

[0231] The difference between this comparative example and Example 1 is that the time and temperature control of chemical treatment is as follows: from normal temperature to 100°C in 40 min, then continue to heat to 165°C in 55 min, and keep the temperature for 30-40 min; the raw material is cooked much faster after the end of cooking, and is not completely pulped.

[0232] Comparative Example 6

[0233] The difference between this comparative example and Example 1 is that no slot screen and hole screen are used.

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

[0235] The applicant further studies the experiments of using slot screen without hole screen, and using hole screen without slot screen, and the results show that the bamboo fiber prepared by these methods is difficult to realize the manufacture of filter paper with air filtration performance.

[0236] Comparative Example 7

[0237] The internodes of sweet bamboo (growing period 3.5 years) are cut into bamboo pieces with a length and width of about 35 mm x 25 mm, 1 kg of absolute dry mass of the bamboo pieces is loaded into a 15 L electric heating rotary digester, and the cooking process is as follows: alkali amount (sodium hydroxide) 25%, sulfidity 25%, liquid ratio 1:4, maximum temperature 160°C, heating time 120 min, and holding time 120 min. After the end of cooking, the material is defibered in a high-concentration defiberer at a concentration of 10%. Then, it is defibered in a high-speed mixer (20000 r / min) at a concentration of 1%. ​

[0238] The performance of the bamboo fiber prepared above is as follows: elastic modulus 12.93 Gpa, zero-distance tensile strength 11.64 KN / 15 mm, hardness 341.19 MPa. The slurry has no impurities such as screened-out impurities, and it is difficult to manufacture filter paper with air filtration performance.

[0239] Comparative Example 8

[0240] The difference between the present application and Example 1 is only that the seam width is 0.6 mm. The results show that the slurry has fiber bundles and fiber groups, and there is no obvious effect of removing fiber bundles and fiber groups compared with the original slurry.

[0241] Comparative Example 9

[0242] The difference between the present application and Example 1 is only that the aperture is 0.5 mm. The results show that the slurry yield is very low, and its yield decreases by about 25% in the same screening time, and many good fibers pass through the screen hole and are not utilized.

Claims

1. A method for preparing bamboo fibers for filter paper, comprising the following steps: (1) selecting materials selecting bamboo materials; (2) chemical treatment chemically treating the bamboo materials selected in step (1) with chemicals; (3) defibrating defibrating the material obtained in step (2) to obtain a coarse pulp; (4) screening screening the coarse pulp obtained in step (3) to obtain bamboo fibers.

2. The production method according to claim 1, wherein In step (1), the bamboo materials are selected from the group consisting of: 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, Dendrocalamus membranaceus Munro; Gigantochloa: Gigantochloa verticillata; Phyllostachys: phyllostachys flexuosa, Phyllostachys edulis, and Phyllostachys edulis; Preferably, the bamboo materials are selected from the group consisting of: Bambusa: Bambusa gibba, Bambusa pervariabilis, Bambusa surrecta, Bambusa textilis; Dendrocalamus: Dendrocalamus minor, Dendrocalamus barbatus, Dendrocalamus farinosus, Dendrocalamus giganteus, Dendrocalamus latiflorus, Dendrocalamus membranaceus; Phyllostachys: phyllostachys flexuosa, Phyllostachys edulis, and Phyllostachys edulis; Preferably, the bamboo materials are selected from the group consisting of: phyllostachys flexuosa, Dendrocalamus minor, Dendrocalamus barbatus, Dendrocalamus farinosus, Dendrocalamus giganteus; Preferably, in step (1), the bamboo materials have a growth period of 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 production method according to claim 1 or 2, wherein In step (2), the chemical agent is selected from one or more of 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 H8O2. Preferably, said 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 medicine is 18wt% to 25wt%, preferably 20wt% to 23wt%, of the dry mass of the bamboo material; Preferably, in step (2), the chemical treatment is performed in a reactor under heating; Preferably, the heating is steam heating or electric heating; Preferably, the electric heating uses a solid-liquid ratio of 1:4.0 to 4.3, preferably 1:4.2; the steam heating uses a solid-liquid ratio of 1:3.5 to 3.8, preferably 1:3.6; Preferably, the reactor is an alkali-resistant medium-low pressure container, including a horizontal tube type continuous digester, a medicine liquid circulation displacement type digester, a steam ball, and a horizontal or vertical rotary digester.

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

5. The production method according to any one of claims 1 to 4, wherein, In step (3), the defibration includes high-concentration defibration and low-concentration defibration; Preferably, the high-concentration defibration refers to mechanical treatment to disperse the material through a high-concentration crushing device, and the concentration of high-concentration crushing is 8wt% to 15wt%, preferably 10wt%; Preferably, the rotating speed of the defibration device used in the low-concentration defibration is ≥3000r / min; Preferably, the slurry concentration of the low-concentration defibration is ≤4wt%.

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

7. The production method according to any one of claims 1 to 6, wherein The preparation method further includes a step of pretreating the selected bamboo material before chemical treatment; Preferably, the pretreatment includes removing branches and leaves of the bamboo material, retaining internode segments and slicing, and washing to remove impurities; Preferably, the pretreated bamboo material is stacked for no more than 4 weeks for chemical treatment.

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

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

10. A method of making the air filtration paper of claim 9, the method comprising: The bamboo fibers are sent to sizing, wet forming, sizing and drying to obtain the air filter paper.

11. The production method according to claim 10, wherein The sizing is to prepare the bamboo fibers into a certain concentration of web stock; Preferably, the concentration of the web stock is 0.6wt‰-6wt‰, preferably 1-2wt‰; Preferably, the wet forming is to pass the web stock through a wet forming device such as a inclined wire, a cylinder mold or a laboratory sheet former to form a wet paper base.

12. The production method according to claim 10 or 11, wherein, The sizing is to attach sizing material to the wet paper base by dipping or penetrating or coating, so that the wet paper base and the dried paper base have higher physical strength; wherein the sizing material is selected from: C3H6N6 emulsion, C3H4O2 emulsion, C 19 H 42 BrN, (C 11 H 12 O3) n1 (Wherein, n1=4-8), (C6H6O·CH2O)x(x=5-10), (C4H6O2) n2 (n2=400-800); Preferably, the sizing is performed by penetration, and the sizing amount is 5wt%-10wt% of the dry weight of the base material fibers, preferably 8wt%; Preferably, the sizing is performed when the wet paper base has a dryness of 35%-60%, preferably 50%.

13. The production method according to any one of claims 10 to 12, wherein, The drying is performed by passing the sized wet paper base through a drying device, a finishing device, a creping device and a line drawing device to obtain a dried, flat, creped and line-drawn air filter paper; Preferably, the drying device can be a drying cylinder, a drying channel, a flat plate, an infrared device, and preferably a penetration drying cylinder.

14. The production method according to any one of claims 10 to 13, wherein, The drying process is performed by temperature zoning and temperature increment, and can include a preheating zone, a drying zone, a solidification zone and a cooling zone; the heating temperature is 110°C-155°C, the solidification temperature is 150°C-155°C, and the solidification time is 1-10min.

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