High-rigidity pe / pet bicomponent nonwoven fabric and application thereof

Abstract

The application discloses high-stiffness PE / PET double-component non-woven fabric and application thereof. The high-stiffness PE / PET double-component non-woven fabric is prepared from modified PE / PET double-component fibers; the modified PE / PET double-component fibers comprise a skin layer and a core layer; the skin layer comprises LDPE and modified PE; and the core layer comprises PET; the modified PE is obtained by grafting maleic anhyad on metallocene PE, and then grafting styrene and POE on the maleic anhyad. In the application, the styrene and POE are grafted on the metallocene PE through maleic anhyad, then mixed with LDPE to obtain mixed PE, and finally the mixed PE is melted with polyester chips through a double die to prepare the modified PE / PET double-component fibers. The non-woven fabric prepared from the modified PE / PET double-component fibers has good adhesion, no blockage, high stiffness, and is not easy to deform after being folded, and can improve the strength and supportability of filter material when used for flat plate filter material.

Description

Technical Field

[0001] This invention relates to the field of filtration technology, specifically to a high-stiffness PE / PET bicomponent nonwoven fabric and its applications. Background Technology

[0002] Flat plate filters are simple in structure and inexpensive, used as pre-filters in air conditioning systems and in comfort air conditioning systems with low purification requirements. They are used to filter dust particles larger than 5μm. Flat plate filters generally consist of an outer frame, filter media, and a protective mesh. The outer frame can be made of paper, aluminum, or galvanized iron. The filter media includes non-woven fabric, nylon mesh, activated carbon, and metal mesh. The protective mesh can be double-sided powder-coated wire mesh or double-sided galvanized wire mesh. The filter media is primarily non-woven fabric, which is typically composed of multiple layers. For example, the top and bottom layers might be PE non-woven fabric, the middle layer might be PTFE non-woven fabric, and these three layers are pleated to form the filter media. The pleating not only increases the filtration area but also provides some support.

[0003] Bicomponent PE / PET nonwoven fabric is a high-performance material that tightly bonds two different fiber materials. This nonwoven fabric has good air permeability and moisture absorption, as well as excellent tensile and tear resistance. Therefore, bicomponent PE / PET nonwoven fabric has gradually replaced PE nonwoven fabric in filter media. However, bicomponent PE / PET nonwoven fabric is made from two components of PE / PET bonded fibers. After being made into filter media, it suffers from the same problem as PE nonwoven fabric: the material is not stiff enough, and it is difficult for the nonwoven fabric to maintain a good folded state after folding. Therefore, it is necessary to increase the PET content in the bicomponent PE / PET fibers to improve stiffness. However, increasing the PET content requires reducing the PE content, which makes it difficult for the nonwoven fabric to bond well during thermal lamination, thus affecting the porosity of the nonwoven fabric. For example, patent CN1705782A discloses a nonwoven fabric composed of core-sheath composite fibers and its preparation method. The sheath component is obtained by mixing a first polyethylene obtained by a metallocene catalyst and a second polyethylene obtained by a Ziegler-Natta catalyst. The sheath thickness is uneven and randomly varies in both the fiber axial and circumferential directions. The nonwoven fabric made from this core-sheath composite fiber is relatively soft and unsuitable as a pleated filter material. Patent CN1042385A discloses a PE / PET bicomponent adhesive fiber, whose sheath is composed of ethylene / vinyl acetate comonomer or ethylene / acrylate system. Only when the sheath component accounts for a large proportion in the fiber can a good bonding effect be achieved, causing the pore size of the fiber to be bonded or blocked by the low-melting-point PE component during the thermal lamination process of the final nonwoven fabric. Therefore, these PE / PET bicomponent fibers disclosed in the prior art are not suitable for manufacturing filter media for flat panel filters. A high-stiffness PE / PET bicomponent nonwoven fabric is needed that can improve the stiffness of the nonwoven fabric without reducing the PE content, so that it can better maintain the folded state after being pleated as the filter media for flat panel filters. Summary of the Invention

[0004] To address the aforementioned limitations of existing technologies, the present invention aims to provide a high-stiffness PE / PET bicomponent nonwoven fabric and its applications. This invention involves grafting styrene and POE onto metallocene PE using maleic anhydride, followed by mixing with LDPE to obtain a mixed PE. The mixed PE is then melted with polyester chips through a dual-die process to prepare modified PE / PET bicomponent fibers. The nonwoven fabric prepared using these modified PE / PET bicomponent fibers not only exhibits good adhesion and non-clogging properties but also possesses high stiffness, resisting deformation after pleating. When used in flat-panel filter media, it can improve the strength and support of the filter media.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a high-stiffness PE / PET bicomponent nonwoven fabric, wherein the high-stiffness PE / PET bicomponent nonwoven fabric is prepared from modified PE / PET bicomponent fibers; The modified PE / PET bicomponent fiber includes a sheath layer and a core layer, wherein the sheath layer includes LDPE and modified PE, and the core layer includes PET; The modified PE is obtained by grafting maleic anhydride onto metallocene PE, and then grafting styrene and POE onto the maleic anhydride.

[0006] Preferably, the mass ratio of LDPE to modified PE is 1:1 to 5; and the mass percentage of the sheath layer in the modified PE / PET bifid fiber is 20 to 60%.

[0007] Preferably, the modified PE is prepared by the following method: Metallocene PE, maleic anhydride, styrene, POE and initiator are premixed evenly, then melt-grafted using a single-screw extruder, and granulated and dried after extrusion to obtain modified PE granules.

[0008] Preferably, the mass ratio of the metallocene PE, maleic anhydride, styrene and POE is 100:1~5:1~3:0.1~0.5; the initiator is DCP, and the amount of the initiator accounts for 0.1~0.3% of the total mass of the metallocene PE.

[0009] Preferably, the temperature of the PE extruder is 180~275℃, and the temperature of the PET extruder is 255-300℃.

[0010] Preferably, the high-stiffness PE / PET bicomponent nonwoven fabric is prepared by the following method: (1) LDPE and modified PE are mixed evenly to obtain mixed PE. The mixed PE and polyester chips are melted using a double die head, and the drawn fibers are stretched under negative pressure to obtain modified PE / PET bi-component fibers. (2) Modified PE / PET bicomponent fibers are laid by airflow, then hot rolled, and finally wound and slit to obtain high stiffness PE / PET bicomponent nonwoven fabric.

[0011] Preferably, the side-blowing air mixing ratio required for the stretching is 80-95%, and the air temperature is 25-50℃.

[0012] Preferably, the hot rolling temperature is 125-145℃ and the hot rolling pressure is 35-100N / mm.

[0013] A second aspect of the invention provides the application of high-stiffness PE / PET bicomponent nonwoven fabric in improving the stiffness of flat panel filter media and maintaining the pleat morphology.

[0014] In a third aspect, the present invention provides a flat panel filter media, wherein the upper and lower layers of the filter media are high-stiffness PE / PET bicomponent nonwoven fabrics, and the middle layer is PTFE nonwoven fabric.

[0015] The beneficial effects of this invention are: (1) The high stiffness PE / PET bicomponent nonwoven fabric of the present invention has higher porosity under the same areal density. The nonwoven fabric has no clogging points and can improve the filtration effect when used as a filter material for flat plate filters.

[0016] (2) The high stiffness of the PE / PET bicomponent nonwoven fabric of the present invention has high stiffness and tensile strength. As a filter material for flat plate filters, it is not easily deformed after being folded and has good support.

[0017] (3) The preparation method of the present invention is simple. Compared with PE nonwoven fabric, it only has one more step of modification. Moreover, the melt modification preparation method is simple and easy to operate. Attached Figure Description

[0018] Figure 1 Photographs of the nonwoven fabrics prepared in Example 2 and Comparative Examples 1-5 after 15 days of folding. Detailed Implementation

[0019] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0020] As described in the background section, PE is relatively soft, and the nonwoven fabric made from it cannot maintain its wrinkled shape for a long time. To improve the stiffness of the nonwoven fabric, the stiffness of the PE nonwoven fabric needs to be increased. However, the PET content in the bicomponent PE / PET fiber can improve the stiffness of the nonwoven fabric. But as the PET content increases, the PE content must decrease. This makes it difficult for the nonwoven fabric to bond together well during thermal lamination, thus affecting the porosity of the nonwoven fabric and consequently its filtration effect.

[0021] Based on this, the purpose of this invention is to provide a high-stiffness PE / PET bicomponent nonwoven fabric and its applications. This invention first modifies the PE / PET bicomponent fibers. The outer layer of the PE / PET bicomponent fibers includes LDPE and modified PE, and the core layer is PET. The modified PE is obtained by grafting styrene and POE onto metallocene PE using maleic anhydride (MAH). Compared with traditional LDPE, metallocene polyethylene (mPE) has a lower melting point and Vicat softening point. It introduces uniformly distributed and regular short branches of ethyl groups or higher into its linear molecular chain. These branches do not participate in the crystallization process of polyethylene, but are only distributed in the amorphous region. Under the action of an initiator, it is easier to generate tertiary carbon free radicals, which do not destroy the polyethylene lattice structure and facilitate grafting reactions. Furthermore, mPE, after maleic anhydride grafting modification, can serve as a good polyolefin hot melt adhesive matrix resin. Therefore, maleic anhydride is not only used to graft styrene and POE onto mPE, but maleic anhydride grafting alone onto mPE can also improve the hot tack of mPE. However, grafting MAH alone cannot improve the stiffness of nonwoven fabrics. Although adding styrene increases the stiffness, the maintenance of the fold morphology after pleating is unstable. Through continuous experimentation, the inventors discovered that grafting a small amount of POE further stabilizes the fold morphology. Furthermore, this grafting occurs on the short branches of mPE, without affecting the crystallization of polyethylene, and the overall properties of PE are not compromised. Nonwoven fabrics prepared from modified PE / PET bicomponent fibers exhibit high strength, high stiffness, stable fold shape, and high porosity, making them suitable for use as filter media in flat panel filters.

[0022] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0023] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0024] Example 1: Preparation of modified PE 100 kg of metallocene PE (DuPont MVLDPE), 3 kg of maleic anhydride, 2 kg of styrene, 500 g of POE, and 300 g of initiator DCP were mixed evenly in a mixer. The mixing was rapid, with the time controlled within 10 minutes, and the mixer temperature controlled below 90°C. The mixed material was then melt-grafted using a single-screw extruder at a temperature of 180–275°C. After extrusion, the material was granulated and dried to obtain modified PE granules.

[0025] Example 2: Preparation of high-stiffness PE / PET bicomponent nonwoven fabric First, take 20 kg of LDPE granules (melting point 115-129℃, density 0.955 g / cm³). 380 kg of the modified PE granules prepared in Example 1 were mixed evenly to obtain mixed PE. 50 kg of mixed PE and 50 kg of PET (melting point 255-265℃, viscosity 0.4 dl / g~0.65 dl / g) chips were then used to prepare PE / PET bicomponent nonwoven fabric using a spunbond process. The mixed PE and PET chips were melted using a dual-die head at melting temperatures of 265-275℃ and 290-300℃. Negative pressure drawing was performed with side-blown air humidity of 5-25% and air temperature of 30-50℃, achieving a fiber fineness of 1-2.5D. Airflow web formation followed. Hot rolling reinforcement was applied at a mill temperature of 130℃ and a mill pressure of 50 N / mm. Winding and slitting were then carried out, with a single-hole output of 40-60 g / h / m and a drawing air pressure of 0.24-0.27 MPa. Measurements showed that the resulting PE / PET bicomponent nonwoven fabric had a thickness of 0.32±0.05 mm and a basis weight of approximately 50±5 g / m². 2 .

[0026] Comparative Example 1 The difference from Example 2 is that no modified PE was added; LDPE was used entirely. The final product was a PE / PET bicomponent nonwoven fabric with a thickness of 0.32±0.05 mm and a basis weight of approximately 50±5 g / m². 2 .

[0027] Comparative Example 2 The difference from Example 2 is that the modified PE was replaced with an equal amount of metallocene PE (DuPont MVLDPE), i.e., no modification treatment was performed on the mPE. The final product was a PE / PET bicomponent nonwoven fabric with a thickness of 0.32±0.05 mm and a basis weight of approximately 50±5 g / m². 2 .

[0028] Comparative Example 3 (1) Mix 100 kg of metallocene PE (DuPont MVLDPE), 3 kg of maleic anhydride and 300 g of initiator DCP evenly in a mixer. Mix quickly, with the time controlled within 10 min, and the mixer temperature controlled below 90℃. The mixed material is then melt-grafted using a single-screw extruder at a temperature of 180~275℃. After extrusion, granulate and dry to obtain modified PE granules.

[0029] (2) The preparation of the PE / PET bicomponent nonwoven fabric was the same as in Example 2, except that the modified PE particles prepared in this comparative example were used instead of the modified PE prepared in Example 1. The thickness of the PE / PET bicomponent nonwoven fabric was 0.32±0.05 mm, and the basis weight was approximately 50±5 g / m². 2 .

[0030] Comparative Example 4 (1) Mix 100 kg of metallocene PE (DuPont MVLDPE), 3 kg of maleic anhydride, 2 kg of styrene, and 300 g of initiator DCP evenly using a mixer. Mix quickly, keeping the time within 10 min, and keep the mixer temperature below 90 °C. The mixed material is then melt-grafted using a single-screw extruder at a temperature of 180-275 °C. After extrusion, granulate and dry to obtain modified PE granules.

[0031] (2) The preparation of the PE / PET bicomponent nonwoven fabric was the same as in Example 2, except that the modified PE particles prepared in this comparative example were used instead of the modified PE prepared in Example 1. The thickness of the PE / PET bicomponent nonwoven fabric was 0.32±0.05 mm, and the basis weight was approximately 50±5 g / m². 2 .

[0032] Comparative Example 5 (1) Mix 100 kg of metallocene PE (DuPont MVLDPE), 3 kg of maleic anhydride, 2 kg of styrene, and 300 g of initiator DCP evenly using a mixer. Mix quickly, keeping the time within 10 min, and keep the mixer temperature below 90 °C. The mixed material is then melt-grafted using a single-screw extruder at a temperature of 180-275 °C. After extrusion, granulate and dry to obtain granules. Then add 500 g of POE granules and mix evenly to obtain modified PE granules.

[0033] (2) The preparation of the PE / PET bicomponent nonwoven fabric was the same as in Example 2, except that the modified PE particles prepared in this comparative example were used instead of the modified PE prepared in Example 1. The thickness of the PE / PET bicomponent nonwoven fabric was 0.32±0.05 mm, and the basis weight was approximately 50±5 g / m². 2 .

[0034] Experimental Example 1 The stiffness, air permeability, tensile strength, and folding endurance of the nonwoven fabrics prepared in Example 2 and Comparative Examples 1-5 were tested according to the test methods disclosed in patent application number JP2018119649, entitled "Spunbond Nonwoven Fabric for Filters and Manufacturing Method Thereof". Stiffness was tested using a softness tester (Zhejiang Sangong Instrument Co., Ltd., model SGJ197), air permeability was tested using an air permeability tester (Guangzhou Runhu Instrument Co., Ltd., RH-TQZ500), tensile strength was tested using a nonwoven fabric tensile strength tester (Guangzhou Kehong Instrument Technology Co., Ltd., KH-8003A), and folding endurance was tested using a MIT-type folding endurance tester (Guangdong Internesson Instrument Co., Ltd.). The results are shown in Table 1.

[0035] Table 1. Stiffness, air permeability, tensile strength, and flexural strength As shown in Table 1, compared with Comparative Examples 1-5, the nonwoven fabric prepared in Example 2 has higher stiffness, strength, and air permeability than Comparative Examples 1-5. It is worth noting that compared with Comparative Examples 2 and 3, although the stiffness of Comparative Example 4 is improved, the air permeability is reduced; this may be because the addition of styrene affects the adhesion of the nonwoven fabric. Comparative Example 5 does not graft POE; after blending POE with PE, although the stiffness is improved, the air permeability is further reduced, indicating that adding POE without grafting will block the pores of the nonwoven fabric, causing a decrease in air permeability. In contrast, Example 2, after adding a small amount of POE, improves the adhesion of the nonwoven fabric, reduces the problem of pore blockage, improves the air permeability of the nonwoven fabric, and also slightly improves the stiffness of the nonwoven fabric.

[0036] Experimental Example 2 The nonwoven fabrics prepared in Example 2 and Comparative Examples 1-5 were cut to dimensions of 1m x 0.5m. In a clean room (25℃, 50% humidity), the cut nonwoven fabrics were folded using a folding machine at a folding angle of 90°, with a fold length of 2cm. After folding, each nonwoven fabric was placed on a flat table along the fold direction and left to stand for 15 days. After 15 days, the folding angle of each fold was measured using a protractor, and the average value was taken (see Table 2). Figure 1 .

[0037] Table 2 Angle Changes According to Table 2 and Figure 1 It can be seen that, compared with Comparative Examples 1-5, the nonwoven fabric prepared in Example 2 showed the least change in angle, maintaining a nearly vertical angle even after standing for 3 days. In contrast, the angles in Comparative Examples 1-5 were all obtuse, indicating that the nonwoven fabric's wrinkle shape was not well maintained. Comparing Example 2 and Comparative Example 4, it can be seen that the addition of styrene significantly improved the wrinkle morphology maintenance ability, and grafting POE further improved the wrinkle morphology maintenance. Comparative Example 5 used a blend of POE and PE to add POE. Compared with Comparative Example 4, the wrinkle angle remained essentially unchanged, indicating that grafting POE is more effective in maintaining wrinkle morphology than adding POE alone.

[0038] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A high-stiffness PE / PET bicomponent nonwoven fabric, characterized in that, The high-stiffness PE / PET bicomponent nonwoven fabric is prepared from modified PE / PET bicomponent fibers; The modified PE / PET bicomponent fiber includes a sheath layer and a core layer, wherein the sheath layer includes LDPE and modified PE, and the core layer includes PET; The modified PE is obtained by grafting maleic anhydride onto metallocene PE, and then grafting styrene and POE onto the maleic anhydride respectively. The mass ratio of LDPE to modified PE is 1:4; the mass percentage of the sheath layer in the modified PE / PET bifid fiber is 50%. The modified PE is prepared by the following method: Metallocene PE, maleic anhydride, styrene, POE and initiator are premixed evenly, and then melt-grafted using a single-screw extruder. After extrusion, the mixture is granulated and dried to obtain modified PE granules. The mass ratio of metallocene PE, maleic anhydride, styrene and POE is 100:3:2:0.

5. The initiator is DCP, and the amount of the initiator accounts for 0.3% of the total mass of metallocene PE.

2. The high-stiffness PE / PET bicomponent nonwoven fabric according to claim 1, characterized in that, The high-stiffness PE / PET bicomponent nonwoven fabric is prepared by the following method: (1) LDPE and modified PE are mixed evenly to obtain mixed PE. The mixed PE and polyester chips are melted using a double die head, and the drawn fibers are stretched under negative pressure to obtain modified PE / PET bi-component fibers. (2) Modified PE / PET bicomponent fibers are laid by airflow, then hot rolled, and finally wound and slit to obtain high stiffness PE / PET bicomponent nonwoven fabric.

3. The high-stiffness PE / PET bicomponent nonwoven fabric according to claim 2, characterized in that, The required air temperature for the negative pressure stretching is 30-50℃.

4. The high-stiffness PE / PET bicomponent nonwoven fabric according to claim 2, characterized in that, The hot rolling temperature is 130℃, and the hot rolling pressure is 50N / mm.

5. The application of the high-stiffness PE / PET bicomponent nonwoven fabric according to any one of claims 1 to 4 in improving the stiffness of the filter media of flat plate filters and maintaining the pleat morphology.

6. A flat plate filter media, characterized in that, The upper and lower layers of the filter material are high-stiffness PE / PET bicomponent nonwoven fabrics as described in any one of claims 1 to 4, and the middle layer is PTFE nonwoven fabric.

Images