Clean zero-carbon filter element and preparation method thereof

Abstract

The invention provides a net zero-carbon filter element and a preparation method thereof, and belongs to the field of degradable filter elements. The CaO modified PLA resin particles are prepared through a melt coating method and a melt blending process, CaO particle aggregation and leakage can be effectively prevented, and the uniformity of a filtering material and a filtering element organization structure is guaranteed; besides, the biodegradability of PLA (polylactic acid) is fully utilized, environmental residues of waste filter materials are reduced from the source, and long-term pollution caused by traditional non-degradable materials is avoided; meanwhile, by means of the carbon capture function of CaO, carbon-containing substances generated by PLA degradation can be accurately and automatically captured in the element degradation process, carbon emission is prevented, the dual value of degradation carbon control and efficient filtering is achieved, and the aim of zero carbon in the whole life cycle of a filtering material is achieved.

Description

Technical Field

[0001] This invention relates to the field of biodegradable filter elements, and more specifically to a net-zero carbon filter element and its preparation method. Background Technology

[0002] Filter elements, as key components in separation, purification, environmental protection, and industrial production, are widely used in industrial production, environmental protection, and daily life, covering scenarios such as air filtration, water purification, and solid-liquid separation. Traditional filter elements are mostly made of petroleum-based polymer materials such as polypropylene (PP) and polyethylene (PE) through processes such as melt-blowing and spunbonding. Although they have good mechanical properties and filtration efficiency, they have two major drawbacks: First, the materials themselves are difficult to degrade naturally, and after disposal, they easily form "white pollution," exacerbating the burden on the ecological environment; second, they have high carbon emissions throughout their entire life cycle, relying on fossil fuels throughout the entire process from raw material mining and processing to product disposal.

[0003] Currently, in the field of biodegradable filter elements, degradation functionality is mostly achieved through improved material formulations. Patent CN103111123A discloses a biodegradable filter core for printed circuit boards, composed of a porous framework and filter yarns. Material degradation is achieved by adding photocatalysts and biodegradable agents to substrates such as polyethylene and polypropylene, solving the long-term pollution problem of traditional filter cores. However, this technology still uses petroleum-based plastics as the substrate, the degradation process does not involve a carbon footprint offsetting mechanism, and the preparation process relies on traditional energy sources, failing to achieve full life-cycle carbon neutrality. In the field of green process optimization, patent CN119793075A discloses a method for manufacturing a green and energy-saving nitrided plastic sintered filter plate. It improves the performance of ultra-high molecular weight polyethylene materials through two nitriding treatments and uses waste recycling processes to reduce resource waste, reflecting an environmentally friendly production process. However, this technology uses non-degradable polyethylene substrates, lacks carbon capture functionality, and does not achieve full-process green energy coverage, remaining a "end-of-life carbon reduction" rather than a "net-zero" technology route.

[0004] In terms of technology, carbon footprint control and functional integration of filter elements face a dual challenge: the existing filter material preparation processes are out of sync with low-carbon goals, and the processing of most biodegradable filter elements still relies on fossil fuels, resulting in a lack of systematic design for carbon footprint control; at the same time, commonly used rigid structural materials (such as block activated carbon, rigid ceramic-based adsorbents, and solid amine block carriers) cannot be adapted to the melt-blown, spunbond, and wet nonwoven fabrication processes of flexible filter elements, and it is difficult to effectively control carbon during the element degradation process, which can easily lead to carbon emissions during degradation. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a net zero carbon filter element and its preparation method, aiming to solve the problems that existing filter elements cannot simultaneously meet the requirements of biodegradation, carbon self-capture during degradation and high-efficiency filtration.

[0006] In a first aspect, this application provides a method for preparing a net-zero carbon filter element, comprising the following steps: S1. CaO nanoparticles and PLA1 were melt-coated to obtain CaO@PLA composite masterbatch; S2. The CaO@PLA composite masterbatch and PLA2 are melt-blended to obtain CaO-modified PLA resin; S3. The CaO-modified PLA resin is used to prepare the filter cartridge shell and the flow guiding layer through a hot melt injection molding process; the CaO-modified PLA resin is first used to prepare nanofibers, and then the filter layer is prepared through a non-woven process. S4. The filter element is obtained by assembling the filter housing, the flow guiding layer and the filter layer through a hot welding process.

[0007] In the technical solution of this application embodiment, CaO@PLA composite masterbatch is prepared by melt coating technology, and then melt-blended with PLA to obtain CaO-modified PLA resin. The resin is then processed by hot melt processing and hot welding to obtain a filter element. Preparing a masterbatch from CaO particles and PLA, and then melt-blending it with a PLA matrix, effectively solves the problem of uneven dispersion of CaO nanoparticles and polymer matrix, which leads to fluctuations in material properties. By designing the composite masterbatch and the PLA in the matrix to have matching molecular weights, it can be ensured that CaO will not be exposed during melt processing. The hot melt processing and hot welding process solves the problems of complex component assembly processes and poor bonding stability, simplifying the preparation process and improving product consistency. Furthermore, this technology fully utilizes the biodegradability of PLA to reduce environmental residues from waste filter materials at the source, avoiding long-term pollution caused by traditional non-degradable materials. At the same time, relying on the carbon capture function of CaO, it can precisely capture carbon-containing substances generated by PLA degradation during the element degradation process, preventing carbon emissions and achieving the dual value of "degradation and carbon control + high-efficiency filtration," helping to achieve the net-zero carbon goal throughout the filter material's entire life cycle. By integrating the carbon capture function of CaO during degradation with the biodegradability of PLA, combined with a gradient pore size nanofiber membrane structure, it achieves self-capture of carbon during the degradation process of the filter element, environmental compatibility throughout its entire life cycle, and high-efficiency filtration performance.

[0008] In some embodiments, in step S1, the molecular weight of PLA1 is 150,000 to 300,000 Daltons; in step S2, the molecular weight of PLA2 is 100,000 to 250,000 Daltons, and is more than 50,000 Daltons lower than the molecular weight of PLA1.

[0009] In this embodiment, by setting the molecular weight relationship between the two PLAs, the molecular weight of PLA1 is higher than that of PLA2. During the subsequent melt blending process, a large number of PLA1 microphases will be formed in PLA2, which are not completely miscible. This is beneficial to the uniform dispersion of CaO nanoparticles in the PLA polymer and is not easy to leak out.

[0010] In some embodiments, in step S1, the mass ratio of CaO nanoparticles to PLA1 is 1:2~20.

[0011] In this embodiment, CaO nanoparticles and PLA1 are mixed in a specific ratio so that the CaO nanoparticles can be uniformly distributed in the PLA1 matrix in the form of a dispersed phase, which facilitates the preparation of a composite masterbatch of PLA1 coated with CaO nanoparticles.

[0012] In some embodiments, in step S2, the mass ratio of the CaO@PLA composite masterbatch to PLA2 is 30:70.

[0013] In this embodiment, a specific ratio of CaO@PLA composite masterbatch and PLA2 is mixed so that the CaO@PLA composite masterbatch can be uniformly distributed in the PLA2 matrix in the form of a dispersed phase, which facilitates the obtaining of CaO modified PLA resin.

[0014] In some embodiments, in step S2, the melting temperature in the melt blending process is 175~190℃, and the melting time is 5~30min.

[0015] In this embodiment, by using specific melt blending conditions, the high-melting-point CaO@PLA1 composite masterbatch can be uniformly dispersed in the low-melting-point, high-flowability PLA2.

[0016] In some embodiments, in step S3, the melting temperature in the hot melt injection molding process is 180~200℃.

[0017] In this embodiment, by using specific hot melt injection molding conditions, the modified PLA resin composed of CaO nanoparticles, high-melting-point PLA1 and low-melting-point PLA2 can have excellent flow molding ability in the injection molding process, without affecting the uniform dispersion of low-content CaO nanoparticles and PLA1 in the resin.

[0018] In some embodiments, in step S4, the welding temperature in the hot welding process is 170~190℃, the welding pressure is 2~8MPa, and the welding time is 10~60s.

[0019] In this embodiment, specific welding conditions are used to seal and bond the filter cartridge shell, flow guide layer, and filter layer made of CaO-modified PLA resin at the joints without affecting the initial structure of each component.

[0020] In some embodiments, in step S1, the melt coating technology includes surface modification of CaO nanoparticles and high shear force melt blending, and the melt coating processing temperature is 185~210℃.

[0021] In this embodiment, CaO nanoparticles are coated into PLA1 in a dry nitrogen environment using melt coating technology, with the melt coating processing temperature set to 185~210℃, to form CaO@PLA composite masterbatch.

[0022] Secondly, this application provides a net-zero carbon filter element, which is prepared by the above-mentioned method for preparing a net-zero carbon filter element. The net-zero carbon filter element includes a filter element shell, a flow guiding layer, and a filter layer. The materials of the filter element shell, the flow guiding layer, and the filter layer are PLA resin containing CaO@PLA composite masterbatch. The net-zero carbon filter element has a carbon neutralization effect throughout its entire life cycle.

[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0025] Figure 1 This is a life cycle diagram of the filter element prepared in the embodiments of this application. Detailed Implementation

[0026] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] To address the challenges of existing filter elements simultaneously achieving biodegradation, carbon self-capture during degradation, and high-efficiency filtration, this application provides a net-zero carbon filter element and its preparation method. A CaO@PLA composite masterbatch is prepared using melt coating technology, then melt-blended with PLA to obtain CaO-modified PLA resin. The resin is then processed using hot melt processing and hot welding to fabricate the filter element. Preparing a uniformly blended composite masterbatch of CaO particles and PLA, followed by melt mixing with a PLA matrix, effectively solves the problem of uneven dispersion of CaO nanoparticles in the polymer matrix, leading to fluctuations in material properties. By designing the molecular weights of PLA in the masterbatch and matrix to match, it ensures that CaO will not leak out during melt processing. The hot melt processing and hot welding process overcomes the drawbacks of existing filter elements, which involve complex processing and assembly of components (shell, flow guide layer, filter media), use of adhesives, low bonding strength, easy detachment, and the introduction of harmful substances. Furthermore, this technology fully utilizes the biodegradability of PLA to reduce environmental residues from waste filter materials at the source, avoiding long-term pollution caused by traditional non-degradable materials. Simultaneously, relying on the carbon capture function of CaO, it can precisely capture carbon-containing substances generated during PLA degradation, preventing carbon emissions and achieving the dual value of "degradation-controlled carbon + high-efficiency filtration," contributing to the achievement of net-zero carbon goals throughout the filter material's lifecycle. By integrating the carbon capture function of CaO during degradation with the biodegradability of PLA, combined with a gradient-pore-size nanofiber membrane structure, it achieves self-capture of carbon during filter element degradation, environmental compatibility throughout its lifecycle, and high-efficiency filtration performance, expanding its application scenarios in high-end fields such as environmental protection, electronics, and biology.

[0029] On the one hand, this application provides a method for preparing a net-zero carbon filter element, comprising the following steps: S1. CaO nanoparticles and PLA1 were melt-coated to obtain CaO@PLA composite masterbatch; S2. The CaO@PLA composite masterbatch and PLA2 are melt-blended to obtain CaO-modified PLA resin; S3. The CaO-modified PLA resin is used to prepare the filter cartridge shell and the flow guiding layer through a hot melt injection molding process; the CaO-modified PLA resin is first used to prepare nanofibers, and then the filter layer is prepared through a non-woven process. S4. The filter element is obtained by assembling the filter housing, the flow guiding layer and the filter layer through a hot welding process.

[0030] In the technical solution of this application embodiment, CaO@PLA composite masterbatch is prepared by melt coating technology, and then melt-blended with PLA to obtain CaO-modified PLA resin. The resin is then processed by hot melt processing and hot welding to obtain a filter element. Preparing a composite masterbatch from CaO particles and PLA, and then melt-blending it with a PLA matrix, effectively solves the problem of uneven dispersion of CaO nanoparticles and polymer matrix, which leads to fluctuations in material properties. By designing the PLA in the masterbatch and matrix to have matching molecular weights, it can be ensured that CaO will not be exposed during melt processing. The hot melt processing and hot welding process solves the problems of complex component assembly processes and poor bonding stability, simplifying the preparation process and improving product consistency. Furthermore, this technology fully utilizes the biodegradability of PLA to reduce environmental residues from waste filter materials at the source, avoiding long-term pollution caused by traditional non-degradable materials. At the same time, relying on the carbon capture function of CaO, it can precisely capture carbon-containing substances generated by PLA degradation during the element degradation process, preventing carbon emissions and achieving the dual value of "degradation and carbon control + high-efficiency filtration," helping to achieve the net-zero carbon goal throughout the filter material's entire life cycle. By integrating the carbon capture function of CaO during degradation with the biodegradability of PLA, combined with a gradient pore size nanofiber membrane structure, it achieves self-capture of carbon during the degradation process of the filter element, environmental compatibility throughout its entire life cycle, and high-efficiency filtration performance.

[0031] Furthermore, in some embodiments, in step S1, the molecular weight of PLA1 is 150,000 to 300,000 Daltons; in step S2, the molecular weight of PLA2 is 100,000 to 250,000 Daltons, and is more than 50,000 Daltons lower than the molecular weight of PLA1.

[0032] In the technical solution of this application embodiment, by setting the molecular weight relationship of the two PLAs, the molecular weight of PLA1 is higher than that of PLA2. During the later melt blending process, a large number of PLA1 microphases will be formed in PLA2, which are not completely miscible. This is beneficial to the uniform dispersion of CaO nanoparticles in PLA polymer and is not easy to leak out.

[0033] Furthermore, in some embodiments, in step S1, the mass ratio of the CaO nanoparticles to PLA1 is 1:2~20.

[0034] Furthermore, in some embodiments, the CaO nanoparticles have a particle size of 10~100nm.

[0035] In the technical solution of this application embodiment, CaO nanoparticles and PLA1 are mixed in a specific ratio so that the CaO nanoparticles can be uniformly distributed in the PLA1 matrix in the form of a dispersed phase, which facilitates the acquisition of a composite masterbatch of PLA1 coated with CaO nanoparticles.

[0036] Furthermore, in some embodiments, in step S2, the mass ratio of the CaO@PLA composite masterbatch to PLA2 is 30:70.

[0037] In the technical solution of this application embodiment, a specific ratio of CaO@PLA composite masterbatch and PLA2 is mixed so that the CaO@PLA composite masterbatch can be uniformly distributed in the PLA2 matrix in the form of a dispersed phase, which facilitates the obtaining of CaO modified PLA resin.

[0038] Furthermore, in some embodiments, in step S2, the melting temperature in the melt blending process is 175~190℃, and the melting time is 5~30min.

[0039] In the technical solution of this application embodiment, by using specific melt blending conditions, the high-melting-point CaO@PLA1 composite masterbatch can be uniformly dispersed in the low-melting-point, high-fluidity PLA2.

[0040] Furthermore, in some embodiments, in step S3, the melting temperature in the hot melt injection molding process is 180~200℃.

[0041] In the technical solution of this application embodiment, through specific hot melt injection molding conditions, the modified PLA resin composed of CaO nanoparticles, high-melting-point PLA1 and low-melting-point PLA2 can have excellent flow molding ability in the injection molding process, and does not affect the uniform dispersion of low-content CaO nanoparticles and PLA1 in the resin.

[0042] Further, in some embodiments, in step S3, the preparation method of the nanofibers includes the following steps: mixing resin and cellulose acetate butyrate (CAB) at a mass ratio of 3:7, spinning the mixture at 210°C and a spinning speed of 10 m / min using a twin-screw spinning machine to obtain composite fibers, and then adding acetone as an extractant to remove CAB to obtain nanofibers of CaO-modified PLA resin.

[0043] Furthermore, in some embodiments, in step S4, the welding temperature in the hot welding process is 170~190℃, the welding pressure is 2~8MPa, and the welding time is 10~60s.

[0044] In the technical solution of this application embodiment, through specific welding conditions, the filter cartridge shell, flow guiding layer and filter layer made of CaO modified PLA resin are sealed and bonded at the joint without affecting the initial structure of each component.

[0045] Furthermore, in some embodiments, in step S1, the melt coating technology includes surface modification of CaO nanoparticles and high shear force melt blending, and the melt coating processing temperature is 185~210℃. Furthermore, in some embodiments, the melt coating technology specifically includes the following steps: under dry nitrogen protection, CaO particle powder with a diameter of 50~100nm is dried at 250~300℃ for 2~4h, and then placed in an ethanol solution of silane coupling agent with a mass fraction of 1~3wt% (the mass ratio of CaO to ethanol solution is 1:10~20), and the surface is wet modified at 60~80℃ for 2~4h, and then dried to obtain hydrophobic CaO; PLA1 was vacuum dried at 80-90℃ for 6-8 hours to achieve a moisture content of <50ppm. Hydrophobic CaO was premixed with the dried PLA1 particles at a ratio of 1:10-100 and then fed into a twin-screw extruder (L / D≥40, screw speed 200-400rpm, temperature from the feed zone to the extruder head increased sequentially from 160℃ to 210℃) for melt blending. The extruded melt sample was water-cooled and pelletized to obtain CaO@PLA composite masterbatch.

[0046] In the technical solution of this application embodiment, CaO nanoparticles are coated into PLA1 in a dry nitrogen environment by melt coating technology, with the melt coating processing temperature set to 185~210℃, to form CaO@PLA composite masterbatch.

[0047] Secondly, this application provides a net-zero carbon filter element, which is prepared using the above-mentioned method for preparing a net-zero carbon filter element. The net-zero carbon filter element includes a filter element shell, a flow guiding layer, and a filter layer. The materials of the filter element shell, the flow guiding layer, and the filter layer are PLA masterbatches containing CaO@PLA composite microcapsules. The net-zero carbon filter element has a carbon neutrality effect throughout its entire life cycle.

[0048] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0049] Example 1 Example 1 provides a method for preparing a net-zero carbon filter element, the specific steps of which are as follows: Melt coating: 1g of CaO powder with a diameter of 50nm was dried at 250℃ for 3h, and then placed in an ethanol solution of 2wt% silane coupling agent (the mass ratio of CaO to ethanol solution was 1:15). The surface was wet modified at 80℃ for 2h, and then dried to obtain hydrophobic CaO. PLA1 (molecular weight 200,000) was vacuum dried at 90℃ for 6h. The hydrophobic CaO and the dried PLA1 particles were premixed at a ratio of 1:5 and then fed into a twin-screw extruder (L / D of 40, screw speed of 200rpm, and temperature from the feed zone to the extruder head increased from 160℃ to 210℃) for melt blending. The extruded melt sample was water-cooled and pelletized to obtain CaO@PLA composite masterbatch.

[0050] Preparation of CaO-modified PLA resin: CaO@PLA composite masterbatch and PLA2 (molecular weight 150,000) were added to a twin-screw extruder at a mass ratio of 30:70 and melt-blended at 180℃ for 15 min to obtain CaO-modified PLA resin.

[0051] Filter cartridge shell / flow guide layer: The filter cartridge shell (size φ50mm×100mm) and flow guide layer (mesh structure, pore size 50~100μm) are prepared by hot melt injection molding (temperature 190℃) using CaO modified PLA resin.

[0052] Filter layer: CaO-modified PLA resin and cellulose acetate butyrate were mixed at a mass ratio of 3:7 and spun at 210℃ and 10m / min using a twin-screw spinning machine to obtain composite fibers with a fiber diameter of 3μm; after extraction with acetone, nanofibers with an average diameter of 230nm were obtained, and then the nanofibers were coated to form a fiber membrane material, thus obtaining the filter layer (average pore size of 250 nm).

[0053] Assemble the filter element: Stack the filter cartridge shell, the flow guide layer (2 pieces, placed on the upper and lower sides of the filter media respectively), and the filter layer in sequence: bottom of the shell → lower flow guide layer → filter media → upper flow guide layer → top of the shell (leaving a welding surface for bonding); use a hot plate welding machine, with the welding head completely bonded to the welding surface of the shell (2mm wide), welding temperature 180℃, apply a pressure of 5MPa, and hold for 30s to obtain the filter element.

[0054] The life cycle diagram of the filter element obtained in this embodiment is as follows: Figure 1 As shown.

[0055] Depend on Figure 1It can be seen that the filter element prepared in this embodiment goes through the entire life cycle of biomass source - corn growth, green manufacturing of calcium oxide, manufacturing of CaO modified PLA resin, manufacturing of CaO modified PLA resin-based nonwoven fabric material / filter element shell / filter element, transportation, application and biodegradation. Considering the carbon emission effect of each link, the carbon emission of the filter element prepared in this embodiment during its life cycle is calculated to be -3.67 + (1.39~1.99) + (1.3~2.5) + (0.1~0.3) + 0 = -0.89~1.12 kg CO2e / kg, achieving net zero carbon.

[0056] Examples 2-3 and Comparative Examples 1-3 Examples 2-3 and Comparative Examples 1-3 each provide a method for preparing a net-zero carbon filter element. The difference between Example 1 and Example 2 is that the molecular weights of PLA1 and PLA2 are different, as shown in Table 1. The other aspects are roughly the same as in Example 1 and will not be repeated here.

[0057] The test methods for the data in the table are as follows: tensile strength and elongation at break are tested according to the method in GB / T 1040.2-2022, and carbon emission intensity during degradation is tested according to the alkaline absorption-titration method in standard GB / T 19277.1.

[0058] Table 1. Molecular weight and performance results of PLA1 and PLA2 in Examples 1-3 and Comparative Examples 1-3. As shown in Table 1, in Example 2, the overall material has a higher molecular weight, resulting in slower degradation, a lower CO2 release rate, and more complete absorption under the same CaO conditions, thus achieving the lowest net emissions and enabling phased carbon negative emissions. In Example 3, the overall material has a lower molecular weight PLA, leading to a relatively faster degradation rate, with the CO2 release rate exceeding the CaO absorption rate, resulting in increased net emissions. Considering the molecular weight ranges of PLA1 and PLA2 in Examples 1-3, the mechanical properties and net emissions of the material are relatively balanced. In Comparative Example 1, the molecular weight of PLA2 is greater than that of PLA1, and the low fluidity of PLA2 makes it difficult to evenly disperse the CaO@PLA1 component, which affects the P... The weakening force of the LA1 matrix phase increases, resulting in a loss of mechanical properties. CaO's absorption of CO2 is not uniform and sufficient, leading to an increase in net emissions. In Comparative Example 2, the molecular weight of PLA2 is much smaller than that of PLA1. PLA2's excessive fluidity causes the CaO@PLA1 component to agglomerate rapidly, reducing the reinforcing effect and causing severe loss of mechanical properties. CaO's absorption of CO2 is even less sufficient, resulting in a significant increase in net emissions. In Comparative Example 3, although the molecular weight is well-matched and the CO2 release rate is very low, absorption is sufficient under the same CaO, and net emissions are very low. However, the excessively high molecular weight of PLA2 leads to low elongation at break and insufficient toughness of the filter element, affecting its practical use.

[0059] Examples 4-5 and Comparative Examples 4-5 Examples 4-5 and Comparative Examples 4-5 each provide a method for preparing a net-zero carbon filter element. The difference from Example 1 is that the mass ratio of CaO nanoparticles to PLA1 is different, as shown in Table 2. The other steps are roughly the same as in Example 1 and will not be repeated here.

[0060] Table 2 shows the mass ratio and performance results of CaO nanoparticles to PLA1 in Examples 4-5 and Comparative Examples 4-5. As shown in Table 2, the CaO content in Example 4 is high, with a ratio of 1:2 to PLA1. The sufficient CaO significantly absorbs CO2, resulting in negative net emissions. In Example 5, the CaO content is low, with a ratio of 1:20 to PLA1. The reduction in CaO leads to a slight increase in net emissions. In Comparative Example 4, the CaO content is too high, with a ratio of 1:1 to PLA1. Although the amount of CaO is large and the theoretical absorption capacity is strong (-0.6), the excess leads to severe aggregation, resulting in a decrease in mechanical properties. In actual degradation, it may not be able to effectively contact and absorb CO2. This data reveals a theoretically optimal but practically infeasible ratio. In Comparative Example 5, the CaO content is too low, with a ratio of 1:25 to PLA1. The amount of CaO is severely insufficient, resulting in the highest net emissions.

[0061] In summary, this application provides a net-zero carbon filter element and its preparation method. A CaO@PLA composite masterbatch is prepared using melt coating technology, and then melt-blended with PLA to obtain a CaO-modified PLA resin. This resin is then processed using hot melt processing and hot welding to prepare the filter element. Preparing a composite masterbatch from CaO particles and PLA, followed by melt mixing with a PLA matrix, effectively solves the problem of uneven dispersion of CaO nanoparticles in the polymer matrix, which leads to fluctuations in material properties. By designing the composite masterbatch and the PLA in the resin matrix to have matching molecular weights, it ensures that CaO will not be exposed during melt processing. The hot melt processing and hot welding process solves the problems of complex element assembly and poor bonding stability, simplifying the preparation process and improving product consistency. Furthermore, this technology fully utilizes the biodegradability of PLA to reduce environmental residues from waste filter materials at the source, avoiding long-term pollution caused by traditional non-degradable materials. At the same time, relying on the carbon capture function of CaO, it can precisely capture carbon-containing substances generated by PLA degradation during the element degradation process, preventing carbon emissions and achieving the dual value of "degradation and carbon control + high-efficiency filtration," helping to achieve the net-zero carbon goal throughout the filter material's entire life cycle. By integrating the carbon capture function of CaO during degradation with the biodegradability of PLA, combined with a gradient pore size nanofiber membrane structure, it achieves self-capture of carbon during the degradation process of the filter element, environmental compatibility throughout its entire life cycle, and high-efficiency filtration performance.

[0062] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a net-zero carbon filter element, characterized in that, Includes the following steps: S1. CaO nanoparticles and PLA1 were melt-coated to obtain CaO@PLA composite masterbatch; S2. The CaO@PLA composite masterbatch and PLA2 are melt-blended to obtain CaO-modified PLA resin; S3. The CaO-modified PLA resin is used to prepare the filter cartridge shell and the flow guiding layer through a hot melt injection molding process; the CaO-modified PLA resin is first used to prepare nanofibers, and then the filter layer is prepared through a non-woven process. S4. The filter element is obtained by assembling the filter housing, the flow guiding layer and the filter layer through a hot welding process.

2. The method for preparing the net-zero carbon filter element according to claim 1, characterized in that, In step S1, the molecular weight of PLA1 is 150,000 to 300,000 Daltons.

3. The method for preparing the net-zero carbon filter element according to claim 1, characterized in that, In step S2, the molecular weight of PLA2 is 100,000 to 250,000 Daltons, and is more than 50,000 Daltons lower than the molecular weight of PLA1.

4. The method for preparing the net-zero carbon filter element according to claim 1, characterized in that, In step S1, the mass ratio of CaO nanoparticles to PLA1 is 1:2~20.

5. The method for preparing the net-zero carbon filter element according to claim 1, characterized in that, In step S2, the mass ratio of the CaO@PLA composite masterbatch to PLA2 is 30:

70.

6. The method for preparing the net-zero carbon filter element according to claim 1, characterized in that, In step S2, the melting temperature in the melt blending process is 175~190℃, and the melting time is 5~30min.

7. The method for preparing the net-zero carbon filter element according to claim 1, characterized in that, In step S3, the melting temperature in the hot melt injection molding process is 180~200℃.

8. The method for preparing the net-zero carbon filter element according to claim 1, characterized in that, In step S4, the welding temperature in the hot welding process is 170~190℃, the welding pressure is 2~8MPa, and the welding time is 10~60s.

9. The method for preparing the net-zero carbon filter element according to claim 1, characterized in that, In step S1, the melt coating technology includes surface modification of CaO nanoparticles and high shear force melt blending, and the melt coating processing temperature is 185~210℃.

10. A net-zero carbon filter element, characterized in that, The net-zero carbon filter element is prepared by the preparation method of any one of claims 1 to 9. The net-zero carbon filter element includes a filter cartridge shell, a flow guiding layer, and a filter layer. The materials of the filter cartridge shell, the flow guiding layer, and the filter layer are modified PLA resin containing CaO. The net-zero carbon filter element has a carbon neutrality effect throughout its entire life cycle.

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