A self-supporting high-stiffness filament electrostatic cotton material and a method for preparing the same

Abstract

The application provides a self-supporting high-stiffness filament electrostatic cotton material and a preparation method thereof, and relates to the technical field of filter materials.The material comprises a polypropylene filament electrostatic cotton filter layer and a bicomponent spun-bond skeleton material which is connected to the filter layer in a composite manner.The filter layer is a filament electrostatic cotton formed by melt spinning of a polypropylene and an electret material blend and consolidation through a needle punching process.The skeleton material is a skin-core structure filament, the core layer is polyethylene terephthalate, and the skin layer is one or more of HDPE, polypropylene or a low-melting copolyester.The filter layer and the skeleton material are integrated through a needle punching process to form an integrated structure, and the skin layer is melted to form a bonding structure through a glazing treatment, and the material is subjected to a corona electret treatment, so that the material has both filtration performance and structural strength without the need for spraying glue, and has significant advantages and application prospects in the field of air filtration.

Description

Technical Field

[0001] This invention relates to the field of filter material technology, and in particular to a self-supporting, high-stiffness long-filament electrostatic cotton material and its preparation method, specifically involving the spinning process of a two-component spunbond nonwoven fabric and the needle-punching, consolidation, and heat treatment process. Background Technology

[0002] With the increasing demand for air filtration, long-filament electrostatic cotton materials are widely used in air purification, fresh air systems, and industrial filtration due to their excellent electrostatic adsorption properties. Long-filament electrostatic cotton is usually made of polypropylene material through melt spinning to form long filaments, which are then solidified into a web through a needle punching process and subjected to electrostatic electret treatment to give the material the ability to electrostatically adsorb fine particulate matter.

[0003] However, long-filament electrostatic cotton itself has a loose structure, weak inter-fiber bonding, and is prone to pilling, making it difficult to use as a standalone filter material directly in filter structures. To improve the material's mechanical strength and stability, existing technologies typically combine electrostatic cotton with a support material. For example, electrostatic cotton can be bonded to a support layer using methods such as spraying, hot rolling, or ultrasonic bonding to achieve structural support. Alternatively, needle-punching can be used to prepare the electrostatic cotton filter material, which is then combined with a support layer to enhance structural stability. Another approach is to use a multi-layer composite structure, layering electrostatic cotton with meltblown, spunbond, and support layers to balance filtration performance and mechanical strength. In addition, there are technical solutions that use bicomponent long filaments with a core-sheath structure to form the support material, thereby improving the overall mechanical properties of the material.

[0004] While the aforementioned technical solutions have improved the performance of the materials to some extent, they still have the following shortcomings: They generally rely on spraying adhesives or multi-layer composite processes to achieve structural bonding; the introduction of adhesives can easily clog filter channels, thus affecting filtration efficiency and posing environmental risks due to the release of volatile organic compounds; the filter layer and the skeleton layer are mostly relatively independent structures, forming a whole through subsequent composite processes, resulting in insufficient interfacial bonding stability and a tendency for delamination, fuzzing, or performance degradation during use; it is difficult to simultaneously achieve high filtration performance and high rigidity in structural design; simply reinforcing the skeleton structure often leads to increased material resistance or decreased bulkiness; furthermore, multi-layer composite and adhesive processes complicate the preparation process and increase production costs, hindering large-scale stable production.

[0005] Therefore, how to enable filament electrostatic cotton materials to maintain good electrostatic filtration performance while possessing sufficient structural rigidity without relying on adhesive spraying, thereby achieving self-supporting applications of the materials and simplifying the preparation process, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a self-supporting, high-stiffness filament electrostatic cotton material and its preparation method. This invention primarily utilizes a composite structure of a polypropylene filament electrostatic cotton filter layer and a core-sheath structured bicomponent spunbond skeleton material. A needle-punching process is used to create a stable, integrated structure between the filter layer and the skeleton material. Furthermore, a calendering treatment activates the low-melting-point components in the skeleton material's sheath, causing them to form a molten bond at fiber intersections, thus replacing traditional adhesive bonding methods. Simultaneously, corona electret treatment is combined to ensure the material maintains excellent electrostatic adsorption properties while achieving stable structural support, unifying filtration and support functions, and simplifying the preparation process.

[0007] The technical means employed in this invention are as follows:

[0008] A self-supporting, high-stiffness filament electrostatic cotton material includes: Filter layer; And a two-component spunbond skeleton material that is compositely connected with the filter layer; The filter layer is a long-filament electrostatic cotton formed by blending polypropylene and electret material, followed by melt spinning and needle punching. The bicomponent spunbond skeleton material is a core-sheath structure filament, with the core layer being polyethylene terephthalate and the sheath layer being one or more of HDPE, polypropylene, or low-melting-point copolyester, and the melting point of the sheath layer being lower than that of the core layer. The filter layer and the skeleton material are combined to form an integrated structure through a needle punching process. The skeleton material is heat-treated to melt the skin layer and form a bonding structure at the fiber intersection.

[0009] Furthermore, the fiber fineness of the skin layer of the bicomponent spunbond skeleton material is 20~35μm.

[0010] Furthermore, the fiber diameter of the filter layer is 15~25μm.

[0011] Furthermore, the weight of the self-supporting, high-stiffness filament electrostatic cotton material is 30~200 g / m². 2 .

[0012] Furthermore, the main component of the electret material is polypropylene, and the effective components include one or more of barium titanate, calcium titanate, strontium titanate, and hafnium oxide, and include a dispersing agent, wherein the dispersing agent is magnesium stearate.

[0013] This invention also discloses a method for preparing the above-mentioned self-supporting high-stiffness filament electrostatic cotton material, comprising the following steps: S1. Filter layer preparation: Polypropylene is mixed with electret material and then melt-spun. After cooling and stretching, it forms filaments and lays them into a web. After one or more needle punchings, it forms a polypropylene filament electrostatic cotton filter layer. S2. Preparation of framework materials: After the skin material and core material are melted and extruded separately, they are spun into a skin-core structure filament through composite spinning, and then cooled, drawn and hot rolled to form a two-component spunbond skeleton material. S3, Composite and Functional Processing: The filter layer and the skeleton material are needle-punched together, and the composite material is calendered to melt and bond the skin of the skeleton material. Then, corona electret treatment is performed to obtain a self-supporting, high-stiffness long-filament electrostatic cotton material.

[0014] Further, in step S1, the mass ratio of polypropylene to electret material is 90~99wt%:1~10wt%.

[0015] Furthermore, in step S2, the core layer material is PET, with an intrinsic viscosity of 0.6~0.7 dL / g and a melting point of 260℃.

[0016] Furthermore, in step S3, the heat treatment involves heating one or both sides of the material with a heated roller to activate the low-melting-point components of the skin to form bonding points.

[0017] Furthermore, in step S3, the corona electret treatment involves injecting charge into the material using a high-voltage electric field, thereby enabling the filter layer to possess electrostatic adsorption properties.

[0018] Compared with the prior art, the present invention has the following advantages: 1. This invention combines a polypropylene filament electrostatic cotton filter layer with a two-component spunbond skeleton material with a core-sheath structure through needle punching and calendering to form a molten bond structure at the fiber intersections of the low-melting-point components in the skeleton material's sheath layer, thereby creating an integrated structure. This achieves structural stability of the material without relying on adhesive spraying, avoiding the filtration performance degradation and volatile organic compound (VOC) hazards caused by traditional adhesive bonding processes.

[0019] 2. This invention uses a needle-punching process to consolidate and disperse polypropylene filaments, enabling the material to maintain a certain loose structure while possessing good fiber bonding strength, thereby achieving both low filtration resistance and high dust holding capacity, and improving the overall filtration performance of the material.

[0020] 3. This invention combines electret material with polypropylene through blending and spinning, along with corona electret treatment, to enable the material to maintain a stable charge inside, thereby endowing the material with electrostatic adsorption capacity for fine particles, improving filtration efficiency and enhancing performance stability.

[0021] 4. This invention uses spunbond filament structure as the main component unit, which can effectively reduce fiber shedding compared with short fiber materials, thereby reducing the risk of secondary pollution and improving the reliability of the material in filtration applications.

[0022] In summary, this invention improves the material structure and preparation method, enabling the polypropylene filament electrostatic cotton filter layer and the two-component spunbond skeleton material to form an integrated structure. This achieves a balance between structural stability and filtration performance without the need for adhesive spraying, resulting in a filament electrostatic cotton material that combines good filtration performance, low resistance, and a certain degree of stiffness, while possessing sufficient mechanical strength for direct use in filter molding.

[0023] The preparation process of this invention is simple and environmentally friendly, and the prepared materials have significant advantages and application prospects in fields such as air filtration. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart illustrating the preparation process of a self-supporting, high-stiffness filament electrostatic cotton material according to the present invention. Detailed Implementation

[0026] 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 some embodiments of the present invention, and not all 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 scope of protection of the present invention.

[0027] like Figure 1 As shown, the preparation method of a self-supporting high stiffness long filament electrostatic cotton material of the present invention mainly includes three stages: filter layer preparation, skeleton material preparation, composite treatment and functionalization treatment.

[0028] First, a polypropylene filament electrostatic cotton filter layer is prepared. Polypropylene masterbatch and electret material are mixed in a certain proportion and then melt-extruded through a screw extruder. The mixture is then spun into continuous filaments through a spinning assembly. After cooling and stretching, the filaments are evenly laid on a mesh belt and then consolidated and dispersed through one or more needle punching processes to form a filament nonwoven filter layer with a fluffy structure.

[0029] Secondly, a bicomponent spunbond skeleton material was prepared. The sheath and core materials were melt-extruded separately using independent extrusion systems, and then processed through a composite spinning assembly to form a sheath-core structure filament. The core layer was polyethylene terephthalate (PET), and the sheath was a low-melting-point polymer. After cooling, drawing, and hot rolling, the resulting filament yielded a bicomponent spunbond skeleton material with certain structural stability.

[0030] Then, the filter layer and the skeleton material are combined using a needle punching device to form an integrated structure. The combined material is then subjected to a calendering process using a heated roller, which melts the low-melting-point components in the skeleton material's outer layer and forms a bonding structure at the fiber intersections, thereby improving the overall structural stability of the material.

[0031] Finally, the composite material is subjected to corona electret treatment to form a stable charge distribution inside the material, thereby endowing it with the ability to electrostatically adsorb fine particles, resulting in a self-supporting, high-stiffness, long-filament electrostatic cotton material.

[0032] Example 1 The present invention provides a method for preparing a self-supporting, high-stiffness filament electrostatic cotton material, which is carried out according to the following steps: S1. Filter layer preparation The polypropylene is a homopolymer polypropylene material with a melt index of 50 g / 10 min (230℃ / 2.16 kg). The main component of the electret material is polypropylene, and the effective components include barium titanate and calcium titanate, with magnesium stearate added as a dispersant.

[0033] Polypropylene masterbatch and electret material were mixed at a mass ratio of 95:5. The mixture was melt-extruded by a screw extruder at 230°C, and then filaments were formed through a spinning assembly. After cooling and stretching, the filaments were laid into a web and then solidified through two needle punching processes to form a long-filament electrostatic cotton filter layer with a fiber diameter of approximately 18 μm.

[0034] S2, Preparation of framework materials The core layer material is PET, with a melting point of approximately 260℃ and an intrinsic viscosity of 0.65 dL / g; the sheath material is a low-melting-point copolyester. The sheath and core layers are melt-extruded separately and then spun into core-sheath structure filaments through composite spinning. These filaments are then cooled, drawn, and hot-rolled to form the skeleton material, with a fiber fineness of approximately 25 μm.

[0035] S3, Composite and Processing The filter layer and the skeleton material are composited using a needle-punching process, followed by single-sided heat treatment with a smooth roller at 140°C to melt the skin and form bonding points. Then, corona electret treatment with 80kV is applied to obtain the final material, with a basis weight of 80g / m³. 2 .

[0036] The resulting material has good structural stability and can be directly used for filter molding.

[0037] Example 2 This invention provides a method for preparing a self-supporting, high-stiffness filament electrostatic cotton material, which is prepared according to the following steps: S1. Filter layer preparation The polypropylene is a homopolymer polypropylene material with a melt index of 70 g / 10min at 230℃ / 2.16kg.

[0038] The main component of the electret material is polypropylene, and the active components include strontium titanate and hafnium oxide.

[0039] Polypropylene masterbatch and electret material are mixed at a mass ratio of 92:8, melt-extruded at 235℃, spun, cooled, drawn and laid into a web, and then solidified through three needle punching processes to form a filter layer with a fiber diameter of approximately 20μm.

[0040] S2, Preparation of framework materials The core layer is PET with an intrinsic viscosity of 0.6 dL / g; the sheath layer is HDPE. The core-sheath structure filaments are formed by bicomponent spinning, and then the skeleton material is formed by drawing and hot rolling. The fiber fineness is approximately 30 μm.

[0041] S3, Composite and Processing The two layers of material were bonded together using a needle-punching method, followed by double-sided heat treatment with a 150°C roller to fully melt the outer layer and form a connecting structure. Afterward, a corona electret treatment was performed using a 90kV voltage, resulting in a material basis weight of 120g / m². 2 .

[0042] Example 3 This invention provides a method for preparing a self-supporting, high-stiffness filament electrostatic cotton material, which is prepared according to the following steps: S1. Filter layer preparation The polypropylene is a homopolymer polypropylene material with a melt index of 90 g / 10 min at 230℃ / 2.16 kg. The main component of the electret material is polypropylene, and the active ingredient includes barium titanate, with magnesium stearate added as a dispersant.

[0043] Polypropylene masterbatch and electret material are mixed at a mass ratio of 90:10, melt-extruded at 225℃ to form filaments, cooled and stretched, laid into a web, and then solidified by multiple needle punches to form a filter layer with a fiber diameter of approximately 22μm.

[0044] S2, Preparation of framework materials The core layer is PET with an intrinsic viscosity of 0.7 dL / g; the outer layer is polypropylene. The skeleton material is formed through composite spinning, drawing, and hot rolling, with a fiber fineness of approximately 35 μm.

[0045] S3, Composite and Processing After the two layers of material are needle-punched together, they are subjected to single-sided heat treatment with a 135℃ smooth roller to locally melt the skin layer and form a dotted bonding structure. Subsequently, corona electret treatment is performed with a voltage of 70kV, and the resulting material has a basis weight of 160g / m². 2 The resulting material has a good fluffy structure and stable filtration performance.

[0046] In summary, as can be seen from the above embodiments, the present invention, by combining the filter layer with the skeleton material and performing hot stamping treatment, enables the material to form a stable structure without the need for adhesive spraying, thereby simultaneously meeting the requirements of filtration performance and structural strength.

[0047] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-supporting, high-stiffness, long-filament electrostatic cotton material, characterized in that, include: Filter layer; And a two-component spunbond skeleton material that is compositely connected with the filter layer; The filter layer is a long-filament electrostatic cotton formed by blending polypropylene and electret material, followed by melt spinning and needle punching. The bicomponent spunbond skeleton material is a core-sheath structure filament, with the core layer being polyethylene terephthalate and the sheath layer being one or more of HDPE, polypropylene, or low-melting-point copolyester, and the melting point of the sheath layer being lower than that of the core layer. The filter layer and the skeleton material are combined to form an integrated structure through a needle punching process. The skeleton material is heat-treated to melt the skin layer and form a bonding structure at the fiber intersection.

2. The self-supporting, high-stiffness filament electrostatic cotton material according to claim 1, characterized in that, The fiber fineness of the skin layer of the bicomponent spunbond skeleton material is 20~35μm.

3. The self-supporting, high-stiffness filament electrostatic cotton material according to claim 1, characterized in that, The fiber diameter of the filter layer is 15~25μm.

4. The self-supporting high-stiffness long-filament electrostatic cotton material according to claim 1, characterized in that, The weight of the self-supporting, high-stiffness long-filament electrostatic cotton material is 30~200g / m². 2 .

5. The self-supporting, high-stiffness filament electrostatic cotton material according to claim 1, characterized in that, The main component of the electret material is polypropylene, and the effective components include one or more of barium titanate, calcium titanate, strontium titanate, and hafnium oxide, and include a dispersing agent, wherein the dispersing agent is magnesium stearate.

6. A method for preparing a self-supporting, high-stiffness filament electrostatic cotton material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Filter layer preparation: Polypropylene is mixed with electret material and then melt-spun. After cooling and stretching, it forms filaments and lays them into a web. After one or more needle punchings, it forms a polypropylene filament electrostatic cotton filter layer. S2. Preparation of framework materials: After the skin material and core material are melted and extruded separately, they are spun into a skin-core structure filament through composite spinning, and then cooled, drawn and hot rolled to form a two-component spunbond skeleton material. S3, Composite and Functional Processing: The filter layer and the skeleton material are needle-punched together, and the composite material is calendered to melt and bond the skin of the skeleton material. Then, corona electret treatment is performed to obtain a self-supporting, high-stiffness long-filament electrostatic cotton material.

7. The preparation method according to claim 6, characterized in that, In step S1, the mass ratio of polypropylene to electret material is 90~99wt%:1~10wt%.

8. The preparation method according to claim 6, characterized in that, In step S2, the core layer material is PET, with an intrinsic viscosity of 0.6~0.7 dL / g and a melting point of 260℃.

9. The preparation method according to claim 6, characterized in that, In step S3, the heat treatment involves heating one or both sides of the material with a heat roller to activate the low-melting-point components of the skin layer to form bonding points.

10. The preparation method according to claim 9, characterized in that, In step S3, the corona electret treatment involves injecting charge into the material using a high-voltage electric field, thereby enabling the filter layer to possess electrostatic adsorption properties.

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