Multistage enhanced air filtration wet spunlace material and preparation method thereof

Abstract

The invention discloses a multi-stage enhanced air filtering wet spunlace material and a preparation method thereof, and belongs to the technical field of filtering materials. The material is of a multi-layer composite structure and comprises a porous fiber layer composed of plant pulp fibers and ultra-short jute fibers and a heat fusion layer composed of three layers of gradient structures. The hot fusion layer comprises a windward layer composed of PET hollow fibers and low-melting-point polyester fibers, a transition layer composed of cotton fibers and low-melting-point polyester fibers, and a refined filtration layer composed of superfine PP fibers and low-melting-point polyester fibers. The preparation method comprises the steps of wet forming of the porous layer, dry carding of the heat fusion layer, multi-stage gradient spunlace composite reinforcement and drying heat setting. Through double-layer compounding and gradient function design, the filtering precision, the dust holding capacity, the mechanical strength and the structural stability of the material are synergistically improved, and meanwhile the material has the advantages of being low in resistance, environmentally friendly and capable of being washed with water and repeatedly used and is suitable for various occasions with the high requirement for the air filtering performance.

Description

Technical Field

[0001] This invention relates to the field of filter materials technology, and mainly to a multi-stage enhanced air filtration wet spunlace material and its preparation method. Background Technology

[0002] Air filters are crucial gas filtration elements widely used in automotive engine intake systems, industrial ventilation, laboratory clean environments, and various precision operating rooms requiring air purification. Their core function is to efficiently trap airborne particulate matter (such as dust, pollen, and industrial dust) to protect machinery, ensure air quality, and safeguard personnel health.

[0003] Currently, nonwoven materials are widely used in the filtration field. For example, meltblown nonwoven fabrics or spunbond / meltblown / spunbond (SMS) composite nonwoven fabrics are used as filter layers because their fibers are finer and their pore structure is richer, giving them an advantage in improving filtration accuracy. However, these materials are mostly made of petroleum-based synthetic fibers (such as polypropylene and polyester), which have poor biodegradability. At the same time, their overall structure often suffers from insufficient strength and stiffness, or their performance deteriorates significantly after repeated use and washing, resulting in a limited service life. Traditional paper filter cartridges generally suffer from low strength, poor stiffness, and high resistance.

[0004] Therefore, developing an air filter material that combines high filtration efficiency, low air resistance, high strength, high rigidity, structural stability, and environmental friendliness and reusability is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a multi-stage enhanced air filtration wet spunlace material and its preparation method. This material, through a unique double-layer composite and gradient structure design, achieves a synergistic improvement in filtration accuracy, dust holding capacity, mechanical strength, and structural stability, while also possessing advantages such as low resistance, environmental friendliness, and reusability.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] In a first aspect, the present invention provides a multi-stage enhanced air filtration wet spunlace material, which is a multi-layer composite structure including a porous fiber layer and a thermal fusion layer; the porous fiber layer is composed of plant pulp fiber and ultra-short hemp fiber; the thermal fusion layer is a three-layer gradient structure including an air-facing layer, a transition layer and a fine filter layer; the air-facing layer is composed of PET hollow fiber and low-melting-point polyester fiber, the transition layer is composed of cotton fiber and low-melting-point polyester fiber, and the fine filter layer is composed of ultra-fine PP fiber and low-melting-point polyester fiber.

[0008] Preferably, the plant pulp fibers in the porous fiber layer include one or more of wood pulp fibers, hemp pulp fibers, bamboo pulp, and cotton pulp. Further, the porous fiber layer comprises 0% to 80% by mass, and the ultra-short hemp fibers comprise 20% to 100% by mass.

[0009] Preferably, the length of the ultra-short hemp fiber is 5mm to 20mm.

[0010] Preferably, the mass ratio of plant pulp fiber to ultra-short hemp fiber in the porous fiber layer is 3:7.

[0011] Preferably, in the windward layer, the mass percentage of PET hollow fiber is 50% to 70%, with the remainder being low-melting-point polyester fiber; in the transition layer, the mass percentage of cotton fiber is 50% to 70%, with the remainder being low-melting-point polyester fiber; and in the fine filter layer, the mass percentage of ultrafine PP fiber is 70% to 90%, with the remainder being low-melting-point polyester fiber.

[0012] Reason: The windward layer uses "PET hollow fiber" to achieve low resistance and dust holding capacity; the transition layer uses "cotton fiber" to form complex filtration channels using its natural three-dimensional curl; and the fine filtration layer uses "ultra-fine PP fiber" with fine fibers and dense structure, which further improves the final filtration efficiency of the material.

[0013] Preferably, the fineness of the ultrafine PP fiber is 0.8d to 1.2d.

[0014] Preferably, the unit area mass ratio of the air-facing layer, transition layer, and fine filtration layer of the thermal fusion layer is 1:1.5:1.

[0015] Preferably, the total unit area mass of the multi-stage reinforced air filter wet spunlace material is 80 g / m² to 200 g / m².

[0016] Secondly, the present invention provides a method for preparing the above-mentioned multi-stage enhanced air filter wet spunlace material, comprising the following steps: (1) Preparation of porous plant fiber layer: Plant pulp fiber and ultra-short hemp fiber are mixed and dispersed in a hydraulic pulper in a certain proportion to prepare a pulp with a concentration of 0.8wt% to 1.2wt%. The pulp is then wet-formed by an inclined screen forming device to obtain a porous plant fiber layer. (2) Preparation of heat-fused layer fiber web: Hollow fibers, heat-fused fibers and cotton fibers are opened, mixed and carded according to the proportion of windward layer, transition layer and fine filter layer to make a dry fiber web with a three-layer structure; (3) Composite and hydroentangled reinforcement: The porous plant fiber layer and the thermally fused fiber web are superimposed and reinforced sequentially through three hydroentangled units: - First hydroentanglement unit (pre-straining): Pressure 20-50 bar; - Second hydroentanglement unit (main piercing): Pressure 40-90 bar; - Third hydroentanglement unit (precision hydroentanglement): Pressure 60-100 bar; The water-based needle insertion sequence consists of one pre-insertion, three main needle insertions, and two fine needle insertions. (4) Drying and heat setting: The hydroentangled reinforced composite material is sent into the drying oven and dried at 170°C for 50 seconds to fully melt the hot melt fibers and complete the interlayer bonding.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Significant advantages of composite filtration: Through a dual composite design of "natural fiber porous layer + synthetic fiber gradient functional layer", the advantages of filtration functions are complemented. Tests show that its filtration accuracy is improved by two orders of magnitude compared with traditional filter media, and its dust holding capacity is increased by more than 40%.

[0018] 2. Outstanding low-resistance and high-efficiency characteristics: The gradient structure design achieves a smooth transition from coarse to fine filtration, reducing sudden airflow resistance. At the same filtration efficiency, air resistance can be reduced by 25-30%.

[0019] 3. Excellent structural stability: The multi-stage gradient hydroentangling process, combined with heat-setting of hot-melt fibers, enhances fiber entanglement and interlayer bonding. The material's interlayer peel strength is ≥1.5 N / cm, heat shrinkage rate is <0.3% (150℃×30min), and it exhibits good dimensional stability.

[0020] 4. Enhanced mechanical properties: The combination of natural hemp fiber and synthetic fiber, along with the optimized hydroentangling process, increases the stiffness of the material by about 80% compared to conventional products, resulting in better processing adaptability.

[0021] 5. Environmentally friendly and economical: The material contains ≥60% natural fibers, making it more easily degradable. The overall structure is robust, washable, and reusable more than 5 times, extending its service life and reducing operating costs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process of the present invention.

[0023] Figure 2 This is a schematic diagram of the structure of the multi-stage enhanced air filtration wet spunlace material described in this invention.

[0024] In the diagram: 1-Windward layer, 2-Transition layer, 3-Fine filtration layer, 4-Porous fiber layer. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0026] General Implementation Examples See Figure 2 A multi-stage reinforced air filtration wet spunlace material is disclosed, comprising, from bottom to top, a porous fiber layer 4 and a heat-fusion layer. The heat-fusion layer consists of an air-facing layer 1, a transition layer 2, and a fine filter layer 3. The porous fiber layer 4 is composed of 30% hemp pulp fiber and 70% ultra-short hemp fiber with a length of 10 mm. In the heat-fusion layer, the air-facing layer 1 is composed of 60% PET hollow fiber and 40% low-melting-point polyester fiber (LPET); the transition layer 2 is composed of 60% cotton fiber and 40% low-melting-point polyester fiber; and the fine filter layer 3 is composed of 80% ultra-fine PP fiber with a fineness of 1.0d and 20% low-melting-point polyester fiber. The total unit area mass of this material is 120 g / m², and the unit area mass ratio of the three layers of the heat-fusion layer is air-facing layer: transition layer: fine filter layer = 1:1.5:1.

[0027] See Figure 1 Its preparation method includes: (1) Preparation of porous fiber layer: Hemp pulp fiber and ultra-short hemp fiber are put into a hydraulic pulper in proportion to make a uniform pulp with a concentration of about 1.0wt%, which is then dehydrated and shaped by an inclined mesh forming device to obtain a porous fiber layer web.

[0028] (2) Preparation of heat fusion layer: The fiber raw materials required for the windward layer, transition layer and fine filter layer are opened by an opening machine, mixed in proportion in a cotton mixing box, and then carded into a web by a carding machine, and the three layers of fiber web are stacked together.

[0029] (3) Hydroentangling composite: The porous fiber layer web is laid under the thermal fusion layer web and fed into the hydroentangling production line together. It passes through the first hydroentangling unit (pressure 35 bar, one pre-spinning), the second hydroentangling unit (pressure 75 bar, three main spinning), and the third hydroentangling unit (pressure 75 bar, two fine spinning) in sequence for hydroentanglement reinforcement.

[0030] (4) Drying and shaping: The hydroentangled reinforced wet composite material is sent into a hot air oven and dried at 170°C for 50 seconds. During this process, the low-melting-point polyester fibers melt and act as an "adhesive", further strengthening the interlayer bonding. Finally, it is wound up by a winding device to obtain the finished product.

[0031] Example 1 A multi-stage reinforced air filtration wet spunlace material comprises a porous fiber layer consisting of 20% hemp pulp fiber and 80% ultra-short hemp fiber (8-12 mm in length); in the heat-fusion layer, the air-facing layer consists of 65% PET hollow fiber and 35% low-melting-point polyester fiber, the transition layer consists of 55% cotton fiber and 45% low-melting-point polyester fiber, and the fine filter layer consists of 85% ultra-fine PP fiber and 15% low-melting-point polyester fiber. The total unit area mass of the material is 110 g / m².

[0032] Its preparation methods include: (1) Preparation of porous fiber layer: Hemp pulp and ultra-short hemp fibers are mixed in a hydraulic pulper to make pulp. The pulp concentration is controlled at 1.0 wt%. After forming by inclined wire mesh, a porous fiber layer mesh with a unit area mass of 65 g / m² is obtained.

[0033] (2) Preparation of thermal fusion layer: The fibers of the windward layer, transition layer and fine filter layer are opened, mixed and combed to form a three-layer gradient fiber web with a total unit area mass of 45 g / m².

[0034] (3) Hydroentangling composite: The porous fiber layer and the thermally fused layer are laminated, and the following steps are performed sequentially: - First hydroentanglement unit: pressure 35 bar; - Second hydroentanglement unit: Pressure 75 bar; - Third hydroentanglement unit: pressure 75 bar; (4) Drying and shaping: Dry in an oven at 170℃ for 50 seconds to fully melt the hot melt fibers and complete the interlayer bonding, then roll up to obtain the finished product.

[0035] Example 2 A multi-stage reinforced air filtration wet spunlace material differs from Example 1 in that the proportion of ultra-short hemp fibers in the porous fiber layer is adjusted to 60%, and the proportion of hemp pulp fibers is 40%, while other processes remain the same.

[0036] Example 3 A multi-stage reinforced air filtration wet spunlace material differs from Example 1 in that the unit area mass ratio of the three-layer structure of the thermal fusion layer is adjusted to windward layer: transition layer: fine filter layer = 1:1.5:1.2. Other processes remain the same.

[0037] Comparative Example 1 A filter material, which differs from Example 1 in that it does not have a heat fusion layer, but is only a porous fiber layer wet hydroentangled material, with a unit area mass adjusted to 110 g / m².

[0038] Comparative Example 2 A filter material differs from Example 1 in that the hydroentangling process is carried out under a single pressure (60 bar) and the hydroentangling pass ratio is 1:1:1.

[0039] Comparative Example 3 A filter material differs from Example 1 in that: low-melting-point polyester fiber is not used in the heat fusion layer, but ordinary polyester fiber is used instead, while the other processes are the same.

[0040] Test data comparison and analysis Test objective: Based on Example 1, compare and test it with Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3 respectively to evaluate its filtration performance, mechanical properties and structural stability.

[0041] Test method: (1) Filtration efficiency: The filtration efficiency for PM0.3 was tested according to EN1822 standard; (2) Air resistance: Initial resistance was measured at a test wind speed of 5.3 m / s; (3) Stiffness: Measured according to GB / T 22364-2008 standard; (4) Interlayer peel strength: determined according to GB / T 2791 standard; (5) Heat shrinkage rate: The dimensional change rate was measured after placing the product in an oven at 150℃ for 30 minutes.

[0042] Test Result Analysis: 1. Comparing Example 1 and Example 2, when the proportion of hemp fiber decreased from 80% to 60%, the filtration efficiency decreased from 99.98% to 99.85%, and the air resistance increased from 28Pa to 32Pa, indicating that appropriately increasing the hemp fiber content helps to improve filtration accuracy and reduce resistance.

[0043] 2. Comparing Example 1 and Example 3, after adjusting the three-layer ratio, the stiffness of Example 3 was slightly improved, but the filtration efficiency and air resistance were both reduced.

[0044] 3. Comparing Example 1 and Comparative Example 1, the material without a heat fusion layer showed a significant decrease in filtration efficiency, air resistance, and stiffness, and the interlayer peel strength could not be measured, which fully demonstrates the necessity of the double-layer composite structure design of the present invention.

[0045] 4. Comparing Example 1 and Comparative Example 2, the material using a single hydroentangling pressure is significantly inferior to Example 1 in terms of interlayer peel strength and thermal shrinkage rate, indicating that the multi-level gradient hydroentangling process plays an important role in enhancing interlayer bonding and material stability.

[0046] 5. Comparing Example 1 and Comparative Example 3, the material that does not use hot melt fiber in the heat fusion layer performed the worst in terms of interlayer peel strength and thermal shrinkage rate, proving that the contribution of hot melt fiber to interlayer bonding during high-temperature heat setting is indispensable.

[0047] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0048] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-stage reinforced air filtration wetlaid spunlace material, characterized by: The material is a multi-layer composite structure, comprising a porous fiber layer and a thermal fusion layer; the porous fiber layer is composed of plant pulp fiber and ultra-short hemp fiber; the thermal fusion layer is a three-layer gradient structure, comprising a windward layer, a transition layer and a fine filtration layer; the windward layer is composed of PET hollow fiber and low-melting point polyester fiber, the transition layer is composed of cotton fiber and low-melting point polyester fiber, and the fine filtration layer is composed of ultra-fine PP fiber and low-melting point polyester fiber.

2. The multi-stage enhanced air filtration hydro-entangled material of claim 1, wherein: In the porous fiber layer, the plant pulp fiber includes one or more of wood pulp fiber, hemp pulp fiber, bamboo pulp, and cotton pulp.

3. The multi-stage enhanced air filtration hydro-entangled material of claim 1, wherein: The length of the ultra-short hemp fiber is 5mm-20mm.

4. The multi-stage enhanced air filtration hydro-entangled material of claim 1 or 2 or 3, wherein: In the porous fiber layer, the mass ratio of plant pulp fiber to ultra-short hemp fiber is 3:

7.

5. The multi-stage enhanced air filtration hydro-entangled material of claim 1, wherein: In the windward layer, the mass percentage of PET hollow fiber is 50%-70%, and the rest is low-melting point polyester fiber; in the transition layer, the mass percentage of cotton fiber is 50%-70%, and the rest is low-melting point polyester fiber; in the fine filtration layer, the mass percentage of ultra-fine PP fiber is 70%-90%, and the rest is low-melting point polyester fiber.

6. The multi-stage enhanced air filtration hydroentangled material of claim 1 or 5, wherein: The fineness of the ultra-fine PP fiber is 0.8d-1.2d.

7. The multi-stage enhanced air filtration hydro-entangled material of claim 1, wherein: The mass ratio of the windward layer, the transition layer and the fine filtration layer of the thermal fusion layer per unit area is 1:1.5:

1.

8. The multi-stage enhanced air filtration hydro-entangled material of claim 1, wherein: The total mass per unit area of the material is 80g / m²-200g / m².

9. A process for the production of a multi-stage reinforced air filtration wetlaid material according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: (1) Preparation of porous fiber layer web: plant pulp fiber and ultra-short hemp fiber are mixed and dispersed in a hydraulic pulper according to a proportion to prepare a slurry with a concentration of 0.8wt%-1.2wt%, and a porous fiber layer web is obtained by wet forming through an inclined screen former; (2) Preparation of thermal fusion layer web: the fibers required for the windward layer, the transition layer and the fine filtration layer are opened, mixed and carded respectively to prepare a dry-laid web with a three-layer structure; (3) Composite and water jet reinforcement: the porous fiber layer web and the thermal fusion layer web are superimposed and reinforced in turn through three water jet units; the pressure of the first water jet unit is 20-50bar, the pressure of the second water jet unit is 40-90bar, and the pressure of the third water jet unit is 60-100bar; the water jet passes through one pre-jet, three main jets and two fine jets; (4) Drying and heat setting: the composite material after water jet reinforcement is dried at 170℃ for 50 seconds to make the hot melt fiber melt and complete the interlayer bonding.

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