Polyester non-woven fabric and preparation method and application thereof

Abstract

The invention relates to the technical field of reverse osmosis membrane supports, in particular to a polyester non-woven fabric and a preparation method and application thereof.The preparation method comprises the steps that S1, polyester main body fibers and polyester adhesive fibers are used as raw materials to prepare high-quantitation original cloth M0 and low-quantitation original cloth H0; carrying out hot pressing pretreatment on the H0 to obtain a product H0 '; s2, overlapping and hot-pressing M0 and H0 'to obtain a composite non-woven fabric M1H1; s3, the M1H1 is impregnated with a functional solution, and the functional solution contains para-aramid nanofibers and nano calcium carbonate modified by hexadecyl trimethyl ammonium bromide; and then carrying out cold pressing on the composite non-woven fabric impregnated with the functional solution to obtain the nano-material modified composite non-woven fabric. And S4, carrying out secondary hot pressing treatment to obtain the polyester non-woven fabric. The polyester non-woven fabric can effectively avoid the problems of excessive curling, excessive permeation of a polysulfone solution and the like during curing after being coated with polysulfone, and is more beneficial to application in a reverse osmosis membrane.

Description

Technical Field

[0001] This invention relates to a polyester nonwoven fabric, its preparation method and application, belonging to the field of reverse osmosis membrane support technology. Background Technology

[0002] Reverse osmosis technology is a membrane separation process that uses pressure difference as the driving force to separate the solvent from the solution. The reverse osmosis membrane, as the core component of reverse osmosis technology, is an artificial semi-permeable membrane with specific characteristics, made by simulating biological semi-permeable membranes. It boasts advantages such as good separation performance, thinness, and high pressure resistance, and has been widely used in seawater desalination, demineralization, wastewater treatment, and concentration separation. It has also found extensive applications in the power, food and beverage, pharmaceutical, chemical, and petroleum industries, generating significant socio-economic benefits.

[0003] Reverse osmosis membranes mainly consist of three parts: a support layer, a polysulfone-based membrane, and a polyamide desalination layer. The support layer provides the interfacial reaction environment, mechanical strength, and stability for the preparation and application of the reverse osmosis membrane; therefore, research on the support layer is crucial for improving the performance of reverse osmosis membranes. The reverse osmosis membrane preparation process involves coating the support layer with a polysulfone solution, followed by drying in a water bath and drying oven to solidify the polysulfone on the support layer surface. Finally, the membrane is wound up to obtain the support layer containing the polysulfone-based membrane. This support layer then undergoes interfacial polymerization and other processes to obtain the reverse osmosis composite membrane.

[0004] Currently, non-woven fabric is mainly used as the support layer for reverse osmosis membranes. However, non-woven fabric support materials prepared by different materials and processes have significant performance differences. How to optimize the production conditions and product quality of reverse osmosis membranes by improving the preparation process of non-woven fabric support materials has become a current research focus.

[0005] Patent application CN112663399A discloses a wet-laid nonwoven fabric for a reverse osmosis membrane support substrate in water treatment and its preparation method. This patent uses PET main fibers and core-sheath structured hot-melt bonding fibers as raw materials. It employs a wet-laid nonwoven fabric process, involving fiber dispersion, inclined wire forming, drying in a drying cylinder, and then offline hot-melt pressing to form a single unit, thus preparing the wet-laid nonwoven fabric for a reverse osmosis membrane support substrate in water treatment. However, the wet-laid nonwoven fabric prepared in this way suffers from large pore size and poor pore size distribution concentration, which affects the consistency of the coating during subsequent reverse osmosis membrane preparation. It also easily causes over-permeation, leading to polysulfone solution penetrating to the back of the nonwoven fabric, ultimately resulting in defects in the prepared reverse osmosis membrane. Furthermore, the coating cost is high and the production efficiency is low, making it difficult to meet the needs of actual production.

[0006] Patent application CN101765456A proposes a nonwoven substrate for reverse osmosis membranes, consisting of spunbond fabric made of continuous long fibers, with multiple layers of spunbond fabric bonded together by thermal bonding; or a spunbond fabric made of composite continuous long fibers composed of various components, combined with meltblown nonwoven fabric produced by meltblowing. Both methods involve multi-layer stacking and heat-pressurization to create the substrate nonwoven fabric for reverse osmosis membranes. While this method can solve the surface fuzzing problem of the substrate nonwoven fabric and achieve the required longitudinal to transverse tensile strength ratio of 2.7:1, it is not ideal for overcoming the curling that occurs during the curing of the substrate nonwoven fabric after polysulfone coating. Furthermore, both spunbond and meltblown nonwoven fabrics exhibit uneven pore sizes in the fiber web formation. This technology also requires complex and diverse equipment, is difficult to control, and involves significant investment. Additionally, the polyester nonwoven fabrics commonly used in reverse osmosis membranes generally have rough or fuzzy surfaces, resulting in rough surfaces or pinholes after recoating by downstream customers.

[0007] Therefore, there is an urgent need to develop a polyester nonwoven fabric to solve the problems of large investment, complex process, rough surface and fuzzing of polyester nonwoven fabric, excessive curling and excessive penetration during curing after polysulfone coating of polyester nonwoven fabric. Summary of the Invention

[0008] This invention addresses the shortcomings of existing technologies by providing a polyester nonwoven fabric, its preparation method, and its application. The polyester nonwoven fabric possesses excellent mechanical properties, a smooth surface, uniform thickness, and more uniform pore size, free of pinholes. This effectively avoids problems such as excessive permeation during polysulfone solution coating and excessive curling of the polyester nonwoven fabric after polysulfone solution curing, thus making it more suitable for application in reverse osmosis.

[0009] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a method for preparing polyester nonwoven fabric, wherein the preparation method is as follows: S1. Preparation and Pretreatment of Raw Fabric Two types of polyester nonwoven fabrics with different basis weights are obtained by disintegrating and stirring the polyester main fiber and polyester bonding fiber, followed by inclined wire wet forming, pressing and drying. These are high basis weight fabric M0 and low basis weight fabric H0. The low basis weight original fabric H0 is pretreated by hot pressing to obtain product H0'; S2, Composite Hot Pressing High basis weight original fabric M0 and low basis weight original fabric H0' after hot pressing pretreatment are stacked and hot pressed to obtain composite nonwoven fabric, namely product M1H1. S3, Functional Solution Treatment A functional solution containing para-aramid nanofibers and hexadecyltrimethylammonium bromide-modified nano-calcium carbonate was impregnated onto a composite nonwoven fabric M1H1; then, the composite nonwoven fabric impregnated with the functional solution was cold-pressed to obtain a nanomaterial-modified composite nonwoven fabric. S4. The second hot pressing process yields the polyester nonwoven fabric, which is the final product M2H2.

[0010] Furthermore, in step S1, the quantitative amount of the high-quantity original fabric M0 is 40-55 g / m³. 2 The basis weight of low basis weight original fabric H0 is 15-30 g / m³. 2 ; When preparing high basis weight fabric M0, the polyester main fiber is 65-85 parts and the polyester bonding fiber is 15-35 parts by weight. When preparing low-weight base fabric H0, the polyester main fiber is 70-80 parts by weight and the polyester bonding fiber is 20-30 parts by weight.

[0011] Furthermore, in step S1, when preparing the high-weight base fabric M0, the fineness of the polyester main fiber is 0.5 dtex-1.0 dtex, and the length of the polyester main fiber is 3-6 mm. When preparing low-weight base fabric H0, the fineness of the polyester main fiber is 1.0 dtex-1.5 dtex, and the length of the polyester main fiber is 3-6 mm; When preparing high basis weight base fabric M0 and low basis weight base fabric H0, the fineness of the polyester bonding fiber is 1.2dtex-1.5dtex, and the length of the polyester bonding fiber is 3-6mm.

[0012] Furthermore, in step S1, during the hot pressing pretreatment, a two-roll hot press is used, with a temperature of 130-170℃, a pressure of 50-80N / mm, and a speed of 5-10m / min, wherein the hot pressing rollers are all steel rollers.

[0013] Furthermore, in step S2, during the stacking hot pressing, a two-roller hot press is used, with a temperature of 180-220℃, a pressure of 60-90N / mm, and a speed of 5-15m / min, wherein the upper roller is a nylon roller and the lower roller is a steel roller.

[0014] Furthermore, the preparation method of the functional solution is as follows: (1) Preparation of para-aramid nanofiber solution and modified nano-calcium carbonate: Para-aramid chopped fibers and potassium hydroxide were added to dimethyl sulfoxide, and then water was added to disperse them evenly to obtain the para-aramid nanofiber solution; wherein the weight ratio of para-aramid chopped fibers, dimethyl sulfoxide, water and potassium hydroxide was (1-3):(80-100):(0.01-0.08):(0.15-4).

[0015] Nano-calcium carbonate was added to deionized water, ultrasonicated, and the pH was adjusted to 4-5 with dilute hydrochloric acid to obtain a nano-calcium carbonate suspension. Hexadecyltrimethylammonium bromide aqueous solution was slowly added dropwise to the nano-calcium carbonate suspension, stirred and ultrasonicated, and then modified nano-calcium carbonate was obtained by solid-liquid separation and drying. (2) Preparation of functional solutions: Modified nano-calcium carbonate was added to a para-aramid nanofiber solution and ultrasonically stirred until homogeneous. The solution was then diluted and dispersed in water to induce a protonation-reduction reaction in the para-aramid nanofibers, resulting in a functional solution of nano-calcium carbonate@para-aramid nanofibers with a nano-calcium carbonate core and a para-aramid nanofiber shell. The mass of the nano-calcium carbonate was 50%-70% of the mass of the para-aramid nanofibers. The mass concentration of the para-aramid nanofibers in the functional solution was 0.1-0.3%.

[0016] Furthermore, in step S3, the cold pressing adopts a two-roll hot press with a temperature of 25-30℃, a linear pressure of 40-60N / mm, and a speed of 5-10m / min. All hot press rollers are steel rollers.

[0017] After step S3, the amount of functional solution impregnated on the composite nonwoven fabric is 10-15% of the dry weight of the composite nonwoven fabric. Further, in step S4, the second hot-pressing treatment uses a two-roller hot press at a temperature of 180-220℃, a pressure of 70-110 N / mm, and a speed of 5-15 m / min. The upper roller is a steel roller, and the lower roller is a nylon roller.

[0018] The present invention also discloses a polyester nonwoven fabric, wherein the polyester nonwoven fabric is prepared according to the preparation method described in the present invention; The polyester nonwoven fabric includes a medium-density portion M2 and a high-density portion H2 in the thickness direction, wherein the density of the medium-density portion M2 is 0.69-0.75 g / cm³. 3 The density of the high-density portion H2 is 0.79-0.95 g / cm³. 3 The density difference between the high-density portion H2 and the medium-density portion M2 is 0.1-0.2 g / cm³. 3 .

[0019] The present invention also discloses an application of polyester nonwoven fabric as a support material for reverse osmosis membranes.

[0020] The beneficial effects of this invention are: 1. The polyester nonwoven fabric of this invention comprises a medium-density portion M2 and a high-density portion H2 in the thickness direction, wherein the upper surface of the medium-density portion M2 is the coating surface of the polysulfone solution. This product structure design with a suitable density difference in the thickness direction ensures that the polysulfone solution effectively impregnates the interior of the polyester nonwoven fabric, providing excellent fixation for the polysulfone film (the polysulfone solution is impregnated on the polyester nonwoven fabric, and the polysulfone film is fixed on the polyester nonwoven fabric through steps such as water bath and drying), while simultaneously preventing the polysulfone solution from penetrating to the back of the polyester nonwoven fabric (i.e., excessive penetration). Furthermore, the product structure design of the polyester nonwoven fabric with a suitable density difference in the thickness direction in this invention also effectively prevents delamination of the polyester nonwoven fabric (when the density difference between the two layers is large, the final product is at risk of delamination; when the density difference between the two layers is small, the penetration of the polysulfone solution cannot be effectively prevented).

[0021] Meanwhile, by impregnating the polyester nonwoven fabric with a functional solution, para-aramid nanofibers are incorporated into the fabric. Cold pressing then helps the para-aramid nanofibers penetrate more evenly within the fabric. During the second hot pressing process, the para-aramid nanofibers act as an adhesive, further preventing delamination of the polyester nonwoven fabric.

[0022] 2. During the preparation of polyester nonwoven fabric, pinholes, fuzzing, or surface roughness are easily encountered, which reduces the quality of the product when polysulfone solution is applied.

[0023] (1) The method of preparing polyester nonwoven fabric in this invention, which uses the sequence of lamination hot pressing, functional solution treatment, and second hot pressing, can effectively improve the smoothness, mechanical properties, pore size, and thickness uniformity of the polyester nonwoven fabric, and effectively avoid the generation of pinholes and fuzzing in the polyester nonwoven fabric. The specific analysis is as follows: After lamination hot pressing, the bonding strength between polyester fibers in M1H1 is greater than that between fibers in M0 and H0' before lamination hot pressing, and a fiber skeleton is formed between the polyester fibers in M1H1. After functional solution treatment of M1H1, the water in the functional solution wets M1H1, and the water evaporates when heated to generate micro-vapor pressure, similar to steam ironing, making the surface more uniform and smooth. In addition, the polyester bonding fibers after water wetting are easy to soften and have a certain fluidity. The polyester bonding fibers are more uniformly wrapped on the surface of the polyester main fibers, the bonding area between fibers is larger, the bonding is tighter, which greatly reduces the problem of fuzzing on the surface of the polyester nonwoven fabric, and the smoothness and mechanical properties of the polyester nonwoven fabric are also significantly improved. At the same time, the polyester bonding fibers are more evenly wrapped around the surface of the polyester main fibers, which makes the fiber gaps or pore sizes in the polyester nonwoven fabric more uniform, thereby improving the thickness uniformity and effectively avoiding the occurrence of pinholes. This also prevents the polyester nonwoven fabric from over-penetrating when coated with polysulfone solution.

[0024] (2) If the conventional method is used: first, functional solution treatment is performed, then lamination and hot pressing are performed, and finally a second hot pressing is performed. Although the smoothness of the polyester nonwoven fabric can be improved to a certain extent, this processing method is prone to causing uneven pore size and fiber distribution of the polyester nonwoven fabric, which in turn causes other problems such as uneven thickness and reduced mechanical properties of the polyester nonwoven fabric. The specific analysis is as follows: After functional solution treatment, the water in the functional solution will wet M0 and H0'. When M0 and H0' are lamination and hot pressing in this state, the fiber skeleton in M0 is still unstable and the structure is loose. The water in it will quickly dissipate at high temperature and cannot form micro-steam pressure, so it cannot achieve the effect of "steam ironing" in this invention. The smoothness of the polyester nonwoven fabric is not significantly improved. At the same time, after M0 is wetted with water and then lamination and hot pressing are performed, the polyester bonding fibers will be excessively softened and flowed under the action of water and hot pressing, causing the fiber gaps to be partially blocked or the fiber distribution to be uneven. This will lead to problems such as excessive penetration of polysulfone solution or increased thickness unevenness and reduced mechanical properties.

[0025] 3. In the functional solution used in the preparation method of this invention, the surface of nano-calcium carbonate has a certain positive charge, and the para-aramid nanofiber solution is an anionic system before protonation reduction. Therefore, when the aramid nanofibers undergo protonation reduction in water, they form a composite nanomaterial with nano-calcium carbonate as the core and para-aramid nanofibers as the shell through electrostatic interaction. The composite nanomaterial modifies the polyester nonwoven fabric, giving it good hydrophilicity. In addition, the composite nanomaterial penetrates into the interior of the polyester nonwoven fabric, and its redistribution within the internal space of the polyester nonwoven fabric results in a more uniform pore size.

[0026] 4. The polyester nonwoven fabric of the present invention has a suitable density difference in the thickness direction, which makes the polyester nonwoven fabric have stronger mechanical properties. It can effectively resist the bending force generated by the single-sided shrinkage of the coating surface when the polyester nonwoven fabric is coated with polysulfone solution and cured, and solve the problem of excessive curling of polyester nonwoven fabric after coating with polysulfone film.

[0027] In summary, the polyester nonwoven fabric prepared by this invention has a simple and controllable process, effectively avoiding the problems of excessive penetration of polysulfone solution and excessive curling during the curing of the polyester nonwoven fabric coated with polysulfone solution. At the same time, the polyester nonwoven fabric has excellent mechanical properties, uniform pore size, no pinholes, smooth surface, uniform thickness, and good hydrophilicity. Attached Figure Description

[0028] Figure 1 This is a flow chart of the polyester nonwoven fabric preparation process described in this invention; Figure 2 This is a schematic diagram of the structure of the polyester nonwoven fabric described in this invention. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.

[0030] Unless otherwise defined, 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 invention pertains. The terminology used is for describing particular embodiments only and is not intended to limit the invention.

[0031] like Figure 1 As shown, a method for preparing a polyester nonwoven fabric is described, wherein the preparation method is as follows: S1. Preparation and Pretreatment of Raw Fabric Two types of polyester nonwoven fabrics with different basis weights are obtained by disintegrating and stirring the polyester main fiber and polyester bonding fiber, followed by inclined wire wet forming, pressing and drying. These are high basis weight fabric M0 and low basis weight fabric H0. The low basis weight original fabric H0 is pretreated by hot pressing to obtain product H0'; S2, Composite Hot Pressing High basis weight original fabric M0 and low basis weight original fabric H0' after hot pressing pretreatment are stacked and hot pressed to obtain composite nonwoven fabric, namely product M1H1. S3, Functional Solution Treatment A functional solution containing para-aramid nanofibers and hexadecyltrimethylammonium bromide-modified nano-calcium carbonate was impregnated onto a composite nonwoven fabric M1H1. The impregnated composite nonwoven fabric was then cold-pressed to obtain a nanomaterial-modified composite nonwoven fabric. The cold pressing was performed using a two-roll hot press at a temperature of 25-30℃, a linear pressure of 40-60 N / mm, and a speed of 5-10 m / min. All hot press rollers were steel rollers.

[0032] S4. The second hot pressing process yields the polyester nonwoven fabric, which is product M2H2.

[0033] Specifically, in step S1, the basis weight of the high-basis-weight original fabric M0 is 40-55 g / m³. 2 The basis weight of low basis weight original fabric H0 is 15-30 g / m³. 2 ; When preparing high basis weight fabric M0, the polyester main fiber is 65-85 parts and the polyester bonding fiber is 15-35 parts by weight. When preparing low-weight base fabric H0, the polyester main fiber is 70-80 parts by weight and the polyester bonding fiber is 20-30 parts by weight.

[0034] Specifically, in step S1, when preparing the high-weight base fabric M0, the fineness of the polyester main fiber is 0.5 dtex-1.0 dtex, and the length of the polyester main fiber is 3-6 mm; When preparing low-weight base fabric H0, the fineness of the polyester main fiber is 1.0 dtex-1.5 dtex, and the length of the polyester main fiber is 3-6 mm; When preparing high basis weight base fabric M0 and low basis weight base fabric H0, the fineness of the polyester bonding fiber is 1.2dtex-1.5dtex, and the length of the polyester bonding fiber is 3-6mm.

[0035] More specifically, the preparation process of high-weight base fabric M0 is as follows: 65-85 parts by weight of polyester main fibers (0.5 dtex-1.0 dtex, 3-6 mm) and 15-35 parts by weight of polyester binder fibers (1.2 dtex-1.5 dtex, 3-6 mm) are loosened, stirred, and then subjected to inclined wire wet forming, pressing, and drying to obtain high-weight base fabric M0 with a basis weight of 40-55 g / m². 2 .

[0036] The preparation process of low-weight base fabric H0 is as follows: 70-80 parts by weight of polyester main fibers (1.0 dtex-1.5 dtex, 3-6 mm) and 20-30 parts by weight of polyester binder fibers (1.2 dtex-1.5 dtex, 3-6 mm) are loosened, stirred, and then subjected to inclined wire mesh wet forming, pressing, and drying to obtain low-weight base fabric H0 with a basis weight of 15-30 g / m². 2 .

[0037] Specifically, in step S1, during the hot pressing pretreatment, a two-roller hot press is used, with a temperature of 130-170℃, a pressure of 50-80N / mm, and a speed of 5-10m / min; wherein, the hot pressing rollers are all steel rollers.

[0038] Specifically, in step S2, during the lamination and hot pressing, a two-roller hot press is used, with a temperature of 180-220℃, a pressure of 60-90 N / mm, and a speed of 5-15 m / min. The upper roller is a nylon roller, and the lower roller is a steel roller.

[0039] Specifically, the preparation method of the functional solution is as follows: (1) Preparation of para-aramid nanofiber solution and modified nano-calcium carbonate: Para-aramid chopped fibers and potassium hydroxide were added to dimethyl sulfoxide, and then water was added to disperse them evenly to obtain the para-aramid nanofiber solution; wherein the weight ratio of para-aramid chopped fibers, dimethyl sulfoxide, water and potassium hydroxide was (1-3):(80-100):(0.01-0.08):(0.15-4).

[0040] Nano-calcium carbonate was added to deionized water, sonicated, and the pH was adjusted to 4-5 with dilute hydrochloric acid to obtain a nano-calcium carbonate suspension. Hexadecyltrimethylammonium bromide was dissolved in a small amount of warm water (35℃) to obtain a hexadecyltrimethylammonium bromide aqueous solution. The hexadecyltrimethylammonium bromide aqueous solution was slowly added dropwise to the nano-calcium carbonate suspension, and the mixture was magnetically stirred at 60℃ for 2 hours. After sonication for 15 minutes, solid-liquid separation was performed by centrifugation, and the mixture was vacuum dried (drying temperature 60℃) to obtain modified nano-calcium carbonate. The mass ratio of the calcium carbonate suspension to the hexadecyltrimethylammonium bromide aqueous solution was 1:1, and the mass of hexadecyltrimethylammonium bromide was twice the mass of the nano-calcium carbonate. Specifically, the nano-calcium carbonate was purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with product number 105387 and particle size of 20-110nm.

[0041] (2) Preparation of functional solutions: Modified nano-calcium carbonate was added to a para-aramid nanofiber solution and ultrasonically stirred until homogeneous. The solution was then diluted with water and stirred until homogeneous, causing the para-aramid nanofibers to undergo a protonation-reduction reaction. This yielded a functional solution of nano-calcium carbonate@para-aramid nanofibers with nano-calcium carbonate as the core and para-aramid nanofibers as the shell. Among them, nano calcium carbonate The mass is 50%-70% of the mass of para-aramid nanofibers. The mass concentration of para-aramid nanofibers in the functional solution is 0.1-0.3%.

[0042] The para-aramid short-cut fibers used in this embodiment of the invention have a fineness of 2D and a length of 7mm, and were purchased from Taihe New Materials.

[0043] Specifically, after step S3, the amount of functional solution impregnated on the composite nonwoven fabric is 10-15% of the dry weight of the composite nonwoven fabric.

[0044] Specifically, in step S4, the second hot pressing process uses a two-roller hot press with a temperature of 180-220℃, a pressure of 70-110 N / mm, and a speed of 5-15 m / min. The upper roller is a steel roller, and the lower roller is a nylon roller.

[0045] like Figure 2 As shown, a polyester nonwoven fabric is prepared according to the preparation method described in this invention; The polyester nonwoven fabric includes a medium-density portion M2 and a high-density portion H2 in the thickness direction, wherein the density of the medium-density portion M2 is 0.69-0.75 g / cm³. 3 The density of the high-density portion H2 is 0.79-0.95 g / cm³. 3 The density difference between the high-density portion H2 and the medium-density portion M2 is 0.1-0.2 g / cm³. 3 The upper surface of the medium-density section is the surface to be coated with polysulfone solution for subsequent applications.

[0046] An application of a polyester nonwoven fabric, wherein the polyester nonwoven fabric is used as a support material for a reverse osmosis membrane.

[0047] Example 1 A method for preparing a polyester nonwoven fabric, wherein the preparation method comprises: S1. Preparation and pretreatment of the original fabric: The preparation process of high-weight base fabric M0 is as follows: 70 parts by weight of polyester main fiber (0.8 dtex, 5 mm) and 30 parts by weight of polyester binder fiber (1.2 dtex, 5 mm) are loosened, stirred, and then subjected to inclined wire wet forming, pressing, and drying to obtain high-weight base fabric M0 with a basis weight of 50 g / m². 2 .

[0048] The preparation process of low-weight base fabric H0 is as follows: 75 parts by weight of polyester main fiber (1.3 dtex, 5 mm) and 25 parts by weight of polyester binder fiber (1.2 dtex, 5 mm) are loosened, stirred, and then subjected to inclined wire mesh wet forming, pressing, and drying to obtain low-weight base fabric H0 with a basis weight of 20 g / m². 2 .

[0049] The low basis weight raw fabric H0 is subjected to hot pressing pretreatment. During the hot pressing pretreatment, the temperature is 150℃, the pressure is 60N / mm, and the speed is 5m / min. The hot pressing pretreatment uses a two-roll hot press, in which the hot pressing rollers are all steel rollers.

[0050] S2, Lamination Hot Pressing: High-weight base fabric M0 is laminated and hot-pressed with low-weight base fabric H0' after hot-pressing pretreatment to obtain composite nonwoven fabric, i.e., product M1H1; the lamination and hot-pressing process is carried out at a temperature of 200℃, a pressure of 75N / mm, and a speed of 10m / min. The upper roller is a nylon roller, and the lower roller is a steel roller.

[0051] S3, Functional Solution Treatment: A functional solution containing para-aramid nanofibers and hexadecyltrimethylammonium bromide-modified nano-calcium carbonate was impregnated onto a composite nonwoven fabric M1H1. The impregnated composite nonwoven fabric was then cold-pressed to obtain a nanomaterial-modified composite nonwoven fabric. The cold pressing was performed using a two-roll hot press at a temperature of 25°C, a linear pressure of 40 N / mm, and a speed of 8 m / min. All hot press rollers were steel rollers.

[0052] After the above steps, the amount of functional solution impregnated on the composite nonwoven fabric is 15% of the dry weight of the composite nonwoven fabric. In the functional solution, the mass concentration of para-aramid nanofibers is 0.2%, and the mass of nano-calcium carbonate is 50% of the mass of para-aramid nanofibers.

[0053] When preparing the para-aramid nanofiber solution, the weight ratio of para-aramid chopped fibers, dimethyl sulfoxide, water and potassium hydroxide is 2:95:0.05:2.

[0054] S4. The second hot-pressing process yields the polyester nonwoven fabric. During the second hot-pressing process, the temperature is 200℃, the pressure is 100 N / mm, and the machine speed is 8 m / min.

[0055] Example 2 A method for preparing a polyester nonwoven fabric, wherein the preparation method comprises: S1. Preparation and pretreatment of the original fabric: The preparation process of high-weight base fabric M0 is as follows: 65 parts by weight of polyester main fiber (0.5 dtex, 6 mm) and 35 parts by weight of polyester binder fiber (1.2 dtex, 3 mm) are loosened, stirred, and then subjected to inclined wire wet forming, pressing, and drying to obtain high-weight base fabric M0 with a basis weight of 40 g / m². 2 .

[0056] The preparation process of low-weight base fabric H0 is as follows: 70 parts by weight of polyester main fiber (1.0 dtex, 6 mm) and 30 parts by weight of polyester binder fiber (1.2 dtex, 3 mm) are loosened, stirred, and then subjected to inclined wire mesh wet forming, pressing, and drying to obtain low-weight base fabric H0 with a basis weight of 30 g / m². 2 .

[0057] The low basis weight original fabric H0 is subjected to hot pressing pretreatment. The hot pressing pretreatment is carried out at a temperature of 170℃, a pressure of 50N / mm, and a speed of 10m / min.

[0058] S2, Lamination Hot Pressing: High basis weight virgin fabric M0 is combined with low basis weight virgin fabric H0 after hot pressing pretreatment. ’ The composite nonwoven fabric is obtained by laminating and hot pressing; the temperature during lamination and hot pressing is 220℃, the pressure is 70N / mm, and the speed is 10m / min.

[0059] S3, Functional Solution Treatment: A functional solution containing para-aramid nanofibers and hexadecyltrimethylammonium bromide-modified nano-calcium carbonate is impregnated onto a composite nonwoven fabric. The impregnated composite nonwoven fabric is then cold-pressed to obtain a nanomaterial-modified composite nonwoven fabric. The cold pressing is performed using a two-roll hot press at a temperature of 28°C, a linear pressure of 45 N / mm, and a speed of 6 m / min. All hot press rollers are steel rollers.

[0060] After impregnation with the functional solution, the amount of functional solution impregnated on the composite nonwoven fabric is 10% of the dry weight of the composite nonwoven fabric.

[0061] In the functional solution, the mass concentration of para-aramid nanofibers is 0.3%, and the mass of nano-calcium carbonate is 60% of the mass of para-aramid nanofibers.

[0062] When preparing the para-aramid nanofiber solution, the weight ratio of para-aramid chopped fibers, dimethyl sulfoxide, water and potassium hydroxide is 3:100:0.08:4.

[0063] S4. The second hot-pressing process yields the polyester nonwoven fabric. During the second hot-pressing process, the temperature is 220℃, the pressure is 90N / mm, and the speed is 10m / min.

[0064] Example 3 A method for preparing a polyester nonwoven fabric, wherein the preparation method comprises: S1. Preparation and pretreatment of the original fabric: The preparation process of high-weight base fabric M0 is as follows: 85 parts by weight of polyester main fiber (1.0 dtex, 3 mm) and 15 parts by weight of polyester binder fiber (1.5 dtex, 6 mm) are loosened, stirred, and then subjected to inclined wire mesh wet forming, pressing, and drying to obtain high-weight base fabric M0 with a basis weight of 55 g / m². 2 .

[0065] The preparation process of low-weight base fabric H0 is as follows: 80 parts by weight of polyester main fiber (1.5 dtex, 3 mm) and 20 parts by weight of polyester binder fiber (1.5 dtex, 6 mm) are loosened, stirred, and then subjected to inclined wire mesh wet forming, pressing, and drying to obtain low-weight base fabric H0 with a basis weight of 15 g / m². 2 .

[0066] The low basis weight original fabric H0 is subjected to hot pressing pretreatment. The hot pressing pretreatment is carried out at a temperature of 130℃, a pressure of 80N / mm, and a speed of 5m / min.

[0067] S2, Lamination Hot Pressing: High basis weight virgin fabric M0 is combined with low basis weight virgin fabric H0 after hot pressing pretreatment. ’ The composite nonwoven fabric is obtained by laminating and hot pressing; the lamination and hot pressing is carried out at a temperature of 180℃, a pressure of 90N / mm, and a speed of 15m / min.

[0068] S3, Functional Solution Treatment: A functional solution containing para-aramid nanofibers and hexadecyltrimethylammonium bromide-modified nano-calcium carbonate is impregnated onto a composite nonwoven fabric. The impregnated composite nonwoven fabric is then cold-pressed to obtain a nanomaterial-modified composite nonwoven fabric. The cold pressing is performed using a two-roll hot press at a temperature of 30°C, a linear pressure of 60 N / mm, and a speed of 10 m / min. All hot press rollers are steel rollers.

[0069] After impregnation with the functional solution, the amount of functional solution impregnated on the composite nonwoven fabric is 12% of the dry weight of the composite nonwoven fabric.

[0070] In the functional solution, the mass concentration of para-aramid nanofibers is 0.1%, and the mass of nano-calcium carbonate is 70% of the mass of para-aramid nanofibers.

[0071] When preparing the para-aramid nanofiber solution, the weight ratio of para-aramid chopped fibers, dimethyl sulfoxide, water and potassium hydroxide is 1:80:0.01:0.15.

[0072] S4. The second hot-pressing process yields the polyester nonwoven fabric. During the second hot-pressing process, the temperature is 180℃, the pressure is 110N / mm, and the speed is 15m / min.

[0073] Comparative Example 1 Polyester nonwoven fabric was prepared using the same method as in Example 1, except that no pretreatment step was performed in step S1 of Comparative Example 1. Furthermore, the polyester nonwoven fabric in Comparative Example 1 has the same density in the thickness direction, i.e., the density difference is 0. The specific preparation process is as follows: S1. Preparation of the original fabric: The preparation process of high-weight base fabric M0 is as follows: 70 parts by weight of polyester main fiber (0.8 dtex, 5 mm) and 30 parts by weight of polyester binder fiber (1.2 dtex, 5 mm) are loosened, stirred, and then subjected to inclined wire wet forming, pressing, and drying to obtain high-weight base fabric M0 with a basis weight of 50 g / m². 2 .

[0074] The preparation process of low-weight base fabric H0 is as follows: 75 parts by weight of polyester main fiber (1.3 dtex, 5 mm) and 25 parts by weight of polyester binder fiber (1.2 dtex, 5 mm) are loosened, stirred, and then subjected to inclined wire wet forming, pressing, and drying to obtain high-weight base fabric M0 with a basis weight of 20 g / m². 2 .

[0075] S2, Lamination Hot Pressing: High basis weight original fabric M0 and low basis weight original fabric H0 are laminated and hot-pressed to obtain composite nonwoven fabric; the lamination and hot-pressing process conditions are the same as in Example 1.

[0076] S3, Functional Solution Treatment: The process conditions are the same as in Example 1.

[0077] S4. The second hot-pressing process yields the polyester nonwoven fabric.

[0078] The process conditions are the same as in Example 1.

[0079] Comparative Example 2 Polyester nonwoven fabric was prepared using the same method as in Example 1, except that steps S2 and S3 were reversed in Comparative Example 2. The specific preparation process is as follows: S1. Preparation and pretreatment of the original fabric: The process conditions are the same as in Example 1.

[0080] S2, Functional Solution Treatment: M0 and H0 ’ The nanofibers were impregnated separately with a functional solution containing para-aramid nanofibers and hexadecyltrimethylammonium bromide-modified nano-calcium carbonate; then Mo and H0 were impregnated separately. ’ Cold pressing separates the high-basis-weight original fabric M0 from the low-basis-weight original fabric H0 after hot pressing pretreatment. ’ The amounts of functional solution used for impregnation are M0 and H0. ’ 15% of the dry weight. The cold pressing conditions are the same as those in step S3 of Example 1.

[0081] The preparation method and concentration of the functional solution are the same as in Example 1.

[0082] S3, Lamination Hot Pressing: The Mo and H0 treated with the functional solution in step S2 ’ The composite nonwoven fabric, namely product M1H1, is obtained by hot pressing and lamination. The hot pressing process conditions are the same as those in step S2 of Example 1.

[0083] S4. The second hot-pressing process yields the polyester nonwoven fabric. The specific process is the same as in Example 1.

[0084] Comparative Example 3 Polyester nonwoven fabric was prepared using the same method as in Example 1, except that the linear pressure in step S1 of Comparative Example 3 was 40 N / mm, resulting in a density difference of <0.1 g / cm³ between the high-density and medium-density portions of the final polyester nonwoven fabric. 3 The specific preparation process is as follows: S1. Preparation and pretreatment of the original fabric: The preparation process of high-quantity virgin fabric M0 is the same as in Example 1.

[0085] The preparation process of low-quantity original fabric H0 is the same as in Example 1.

[0086] The low basis weight raw fabric H0 is subjected to hot pressing pretreatment. During the hot pressing pretreatment, the temperature is 150℃, the pressure is 40N / mm, and the speed is 5m / min. The hot pressing pretreatment uses a two-roll hot press, in which the hot pressing rollers are all steel rollers.

[0087] S2, Lamination Hot Pressing: High basis weight virgin fabric M0 is combined with low basis weight virgin fabric H0 after hot pressing pretreatment. ’ The composite nonwoven fabric is obtained by laminating and hot pressing; the process conditions for laminating and hot pressing are the same as those in Example 1.

[0088] S3, Functional Solution Treatment: The process conditions are the same as in Example 1.

[0089] S4. The second hot-pressing process yields the polyester nonwoven fabric.

[0090] The process conditions are the same as in Example 1.

[0091] Comparative Example 4 Polyester nonwoven fabric was prepared using the same method as in Example 1, except that in step S1 of Comparative Example 4, the pressure of the hot-pressing pretreatment was increased, so that the density difference between the high-density and medium-density portions of the final polyester nonwoven fabric was >0.2 g / cm³. 3 The specific preparation process is as follows: S1. Preparation and pretreatment of the original fabric: The preparation process of high-quantity virgin fabric M0 is the same as in Example 1.

[0092] The preparation process of low-quantity original fabric H0 is the same as in Example 1.

[0093] The low basis weight original fabric H0 is subjected to hot pressing pretreatment. The hot pressing pretreatment is carried out at a temperature of 150℃, a pressure of 100N / mm, and a speed of 5m / min.

[0094] S2, Lamination Hot Pressing: The process conditions are the same as in Example 1.

[0095] S3, Functional Solution Treatment: The process conditions are the same as in Example 1.

[0096] S4. The second hot-pressing process yields the polyester nonwoven fabric.

[0097] The process conditions are the same as in Example 1.

[0098] Comparative Example 5 Polyester nonwoven fabric was prepared using the same method as in Example 1, except that the functional solution treatment step S3 was not performed in Comparative Example 5. The specific preparation process is as follows: S1. Preparation and pretreatment of the original fabric: The process conditions are the same as in Example 1.

[0099] S2, Lamination Hot Pressing: The process conditions are the same as in Example 1.

[0100] S3. The second hot-pressing process yields the polyester nonwoven fabric.

[0101] The process conditions are the same as step S4 in Example 1.

[0102] Comparative Example 6 Polyester nonwoven fabric was prepared using the same method as in Example 1, except that the functional solution in Comparative Example 6 did not contain para-aramid nanofibers. Other process conditions were the same as in Example 1. The specific preparation process of the functional solution is as follows: (1) Preparation of modified nano-calcium carbonate: Nano-calcium carbonate was added to deionized water, ultrasonically treated, and the pH was adjusted to 4-5 with dilute hydrochloric acid to obtain a nano-calcium carbonate suspension. Hexadecyltrimethylammonium bromide was dissolved in a small amount of warm water (35℃) to obtain a hexadecyltrimethylammonium bromide aqueous solution. The hexadecyltrimethylammonium bromide aqueous solution was slowly added dropwise to the nano-calcium carbonate suspension, and the mixture was magnetically stirred at 60℃ for 2 hours. Then, it was ultrasonically treated for 15 minutes. The solid and liquid were separated by centrifugation, and the modified nano-calcium carbonate was obtained by vacuum drying (drying temperature 60℃). (2) Preparation of functional solutions: Modified nano-calcium carbonate was added to water and ultrasonically stirred until homogeneous. It was then diluted in water and stirred until homogeneous to obtain a functional solution with a nano-calcium carbonate mass concentration of 0.1%.

[0103] Comparative Example 7 Polyester nonwoven fabric was prepared using the same method as in Example 1, except that the functional solution in Comparative Example 7 did not contain hexadecyltrimethylammonium bromide-modified nano-calcium carbonate. Other process conditions were consistent with those in Example 1. The specific preparation process of the functional solution is as follows: (1) Preparation of para-aramid nanofiber solution: Para-aramid chopped fibers and potassium hydroxide were added to dimethyl sulfoxide, and then water was added to disperse them evenly to obtain the para-aramid nanofiber solution. When preparing the para-aramid nanofiber solution, the weight ratio of para-aramid chopped fibers, dimethyl sulfoxide, water and potassium hydroxide was 2:95:0.05:2.

[0104] (2) Preparation of functional solutions: The para-aramid nanofiber solution from step (1) was diluted in water and stirred until homogeneous, causing the para-aramid nanofibers to undergo a protonation-reduction reaction to obtain the final functional solution. The mass concentration of the para-aramid nanofibers in the functional solution was 0.2%.

[0105] Comparative Example 8 Polyester nonwoven fabric was prepared using the same method as in Example 1, except that cold pressing was not performed in step S3 of Comparative Example 8. Other process conditions were the same as in Example 1.

[0106] The polyester nonwoven fabrics prepared in the above examples and comparative examples were subjected to performance tests, and the test methods involved are as follows: I. Polysulfone Solution Permeation: The polyester nonwoven fabrics prepared in the above examples and comparative examples were cut into A4 size. A polysulfone solution was coated onto the polyester nonwoven fabric fixed to a stainless steel plate. After 2 seconds, the fabric was immersed in pure water at 20°C for phase separation. After washing and dehydration, the fabric was dried in a hot air dryer at 80°C to obtain a polysulfone film. The thickness of the polyester nonwoven fabric after coating with the polysulfone film was 190 μm. The polysulfone solution consisted of 20 wt% polysulfone and 80 wt% dimethylformamide. The polysulfone was purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., item number 428302. The dimethylformamide was purchased from Maclean's, item number D757658.

[0107] The evaluation will be conducted using the following criteria: Good: No resin was found adhering to the stainless steel plate. Poor: Resin was found adhering to the stainless steel plate.

[0108] II. Curl Height Test Method: Collect three samples (20cm longitudinally × 20cm transversely) from any part of the polyester nonwoven fabric with polysulfone film attached obtained in the above steps. Place the smoothest side of each sample facing upwards on a flat platform. Measure the distance from the midpoint of each curled side of each sample to the platform (measurement in units of 0.5mm). Calculate the average value of the measured data, and then round off to the second decimal place to determine the curl height of the polyester nonwoven fabric.

[0109] 3. Number of hairs raised by friction: Use a friction brush with a width of 2.5cm and a length of 7cm at a speed of 0.2-0.3N / cm. 2 The pressure is pressed vertically onto the nonwoven fabric, and rubbed once along the longitudinal direction of the nonwoven fabric at a speed of 55 cm / s. After rubbing, the result is visually measured over 1 meter. 2 The number of hairs that detach from the surface due to friction is taken as the percentage per 1m. 2 The number of bristles. The bristles in the friction brush are made of ester monofilaments, with a length of 18mm, a diameter of 200µm, and a bending stiffness of 0.3gf.cm. 2 / filament. The density of the filaments in the friction brush is 550 filaments / cm. 2 .

[0110] IV. Other testing methods are as follows: 1. Quantitative testing: Detected according to the method in GB / T 451.2; 2. Medium / high density layer thickness: Measured using a high-resolution three-dimensional X-ray microscopy system (BRUKER 3D XRM), instrument model SKYSCAN 1272; 3. Medium / high density layer density = Medium / high density layer quantity / Medium / high density layer thickness; 4. Total thickness: Refer to GB / T 451.3 standard; 5. Total thickness non-uniformity rate (CV): CV = (sample standard deviation / mean) × 100%; Sample standard deviation ;in, s Indicates the sample standard deviation. x i Indicates the first i One sample point, This represents the sample mean. n Indicates the number of samples.

[0111] 6. Tensile strength: Tested according to the method of GB / T 12914; 7. Interlayer bond strength: Tested according to the method of GB / T 26203; 8. Peel strength of polysulfone film: tested according to GB / T 34444 method; 9. Breathability: Tested according to the method of GB / T 24218.15; 10. Hydrophilicity: The reference standard is AATCC 79-2010 (use a stopwatch to record a certain water absorption time; the shorter the time, the better the wettability of the sample). 11. Smoothness: The reference standard is GB / T 456-2002; 12. Pinhole count: Tested according to the method in T / ZGM 002-2024. The basis weight, thickness, density, air permeability, and tensile strength of the polyester nonwoven fabrics in the above examples and comparative examples were tested or calculated, and the results are recorded in the tables. Specific test results are shown in Tables 1, 2, and 3 below.

[0112] Table 1 Test data of basis weight, thickness, and density properties of polyester nonwoven fabric

[0113] Table 2. Relevant mechanical properties and air permeability of polyester nonwoven fabrics

[0114] Table 3. Test results of other properties of polyester nonwoven fabrics

[0115] As can be seen from the data in the table above, the polyester nonwoven fabrics prepared by the preparation method described in this invention in Examples 1-3 have excellent mechanical properties, high smoothness, uniform thickness, good hydrophilicity, uniform pore size, and no pinholes. This can effectively avoid problems such as excessive curling of the polyester nonwoven fabric and excessive permeation of the polysulfone solution during curing after coating with polysulfone solution, thus making it more suitable for application in reverse osmosis membranes.

[0116] A comparison of the data from Comparative Example 1 and Example 1 shows that the polyester nonwoven fabric in Comparative Example 1 has a density of 0.72 g / cm³ in the thickness direction. 3 Its pinhole count is significantly higher than that of Example 1, which leads to the polysulfone solution seeping into the back of the polyester nonwoven fabric during coating. The density of commercially available conventional products is 0.72 g / cm³. 3 Polysulfone solution can easily penetrate to the back of the polyester nonwoven fabric. In Example 1, by setting two different densities in the thickness direction of the polyester nonwoven fabric, this situation of polysulfone solution penetrating to the back of the nonwoven fabric is effectively avoided. The density difference in Example 1 also results in a much lower curl height of the polyester nonwoven fabric compared to Comparative Example 1, and the tensile strength of the polyester nonwoven fabric and the peel strength of the polysulfone film are also greater than those in Comparative Example 1.

[0117] A comparison of the data from Comparative Example 2 and Example 1 shows that, after reversing steps S2 and S3, the unevenness of the polyester nonwoven fabric thickness (CV value) in Comparative Example 2 is much greater than that in Example 1. Furthermore, the tensile strength, smoothness, interlayer bonding strength, and peel strength of the polysulfone film in Comparative Example 2 are significantly lower than those in Example 1. Moreover, the number of pinholes in the polyester nonwoven fabric in Comparative Example 2 is significantly greater than that in Example 1, leading to the polysulfone solution penetrating to the back of the polyester nonwoven fabric during coating. In Example 1, the polysulfone solution penetration of the polyester nonwoven fabric was good.

[0118] Example 1 describes a process for preparing polyester nonwoven fabric involving first lamination and hot pressing, followed by functional solution treatment and a second hot pressing. After lamination and hot pressing, the bonding strength between polyester fibers in M1H1 in Example 1 is greater than that of M0 and H0' without lamination and hot pressing, allowing the polyester fibers in M1H1 to form a fiber skeleton. Based on this, a second functional solution wetting treatment is applied. The water evaporates upon heating, generating micro-steam pressure, similar to steam ironing, resulting in a more uniform and smooth surface. Furthermore, the water in the functional solution softens the polyester bonding fibers and gives them a certain degree of fluidity, allowing them to more evenly coat the surface of the main polyester fibers. This results in a larger bonding area and tighter bond between fibers, significantly reducing surface fuzzing and improving the mechanical properties of the polyester nonwoven fabric. Simultaneously, the more even coating of the polyester bonding fibers on the surface of the main polyester fibers makes the fiber gaps and pore sizes more uniform, effectively preventing pinholes and thus avoiding the problem of polysulfone solution easily penetrating to the back of the polyester nonwoven fabric during coating.

[0119] In Comparative Example 2, a processing method involving first treating with a functional solution, followed by overlapping hot pressing, and then a second hot pressing is employed. First, the water in the functional solution wets Mo and H0'. At this stage, the fiber skeleton in the polyester nonwoven fabric Mo is still unstable and has a loose structure. The moisture evaporates rapidly at high temperatures, failing to create micro-steam pressure and thus failing to achieve a "steam ironing" effect similar to that in Example 1. Although it can improve surface smoothness, its smoothness is less than that of Example 1. Simultaneously, after Mo and H0' are wetted with water in the functional solution and then hot-pressed, the polyester bonded fibers become excessively softened and flow under the influence of moisture and hot pressing, causing partial blockage of fiber gaps or uneven fiber distribution. Although the second hot pressing further adjusted the structure of the polyester nonwoven fabric, the degree of adjustment was limited. Ultimately, the uneven fiber distribution led to uneven thickness, which further reduced the mechanical properties and interlayer bonding strength of the polyester nonwoven fabric. At the same time, the uneven fiber distribution of the polyester nonwoven fabric caused uneven fiber gaps or pore sizes, resulting in pinholes. Consequently, the polysulfone solution could easily penetrate to the back of the polyester nonwoven fabric during the coating process, affecting its use.

[0120] A comparison of the data from Comparative Example 3 and Example 1 shows that the density difference of the polyester nonwoven fabric in the thickness direction in Comparative Example 3 is less than 0.1 g / cm³. 3 The number of pinholes in Comparative Example 3 was greater than that in Example 1, which caused the polysulfone solution to penetrate to the back side of the polyester nonwoven fabric during the coating process. The tensile strength or interlayer bond strength of the polyester nonwoven fabric and the peel strength of the polysulfone film in Comparative Example 3 were also lower than those in Example 1. At the same time, the curl height in Comparative Example 3 was higher than that in Example 1.

[0121] A comparison of the data from Comparative Example 4 and Example 1 shows that the density difference of the polyester nonwoven fabric in Comparative Example 4 in the thickness direction is greater than 0.2 g / cm. 3 In this case, the interlayer bonding strength, tensile strength, and peel strength of the polysulfone film of the polyester nonwoven fabric are much lower than those of Example 1, and the polyester nonwoven fabric is prone to delamination, affecting its use.

[0122] A comparison of the data from Comparative Example 5 and Example 1 shows that Comparative Example 5 did not undergo functional solution treatment. Therefore, the smoothness, interlayer bonding strength, tensile strength, and peel strength of the polysulfone film in Comparative Example 5 are significantly lower than those in Example 1. The number of pinholes in the polyester nonwoven fabric of Comparative Example 5 is greater than that of Example 1, which leads to the polysulfone solution easily penetrating to the back of the polyester nonwoven fabric during coating, affecting its use. Furthermore, the number of friction fuzz roots and the curl height of the polyester nonwoven fabric in Comparative Example 5 are significantly higher than those in Example 1.

[0123] A comparison of the data from Comparative Example 6 and Example 1 shows that the functional solution in Comparative Example 6 lacks para-aramid nanofibers. Therefore, the tensile strength, interlayer bonding strength, and peel strength of the polysulfone film in Comparative Example 6 are lower than those in Example 1, while the crimp height of the polyester nonwoven fabric in Comparative Example 6 is significantly higher than that in Example 1. This is because the para-aramid nanofibers in the polyester nonwoven fabric of Example 1 melt or soften during hot pressing, acting as a bond to the surrounding polyester fibers, resulting in a stronger bond between the polyester fibers. Consequently, the mechanical properties of the polyester nonwoven fabric and the peel strength of the polysulfone film are higher than those in Comparative Example 6. Simultaneously, during coating, the number of pinholes in the polyester nonwoven fabric of Comparative Example 6 is greater than that in Example 1, leading to poor penetration of the polysulfone solution during coating. This clearly demonstrates that the melting or softening of the para-aramid nanofibers during hot pressing in Example 1 adjusts the fiber gaps or internal pore size of the polyester nonwoven fabric, making the fiber gaps or pore size more uniform, reducing pinhole formation, and thus preventing the polysulfone solution from penetrating to the back of the polyester nonwoven fabric.

[0124] A comparison of the data from Comparative Example 7 and Example 1 shows that when the functional solution in Comparative Example 7 does not contain modified calcium carbonate, the hydrophilicity of the polyester nonwoven fabric is significantly lower than that in Example 1.

[0125] A comparison of the data from Comparative Example 8 and Example 1 shows that, in Comparative Example 8, without cold pressing during the functional solution treatment, the interlayer bonding strength, tensile strength, and peel strength of the polysulfone film are lower than in Example 1. Furthermore, the number of pinholes in the polyester nonwoven fabric in Comparative Example 8 is greater than in Example 1, resulting in poor polysulfone solution penetration during coating. This is because without cold pressing, the para-aramid nanofibers are not evenly distributed in the thickness direction of the product, thus failing to effectively perform their bonding and pore size adjustment functions.

[0126] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing polyester nonwoven fabric, characterized in that, The preparation method is as follows: S1. Preparation and pretreatment of the original fabric: Two types of polyester nonwoven fabrics with different basis weights are obtained by disintegrating and stirring the polyester main fiber and polyester bonding fiber, followed by inclined wire wet forming, pressing and drying. These are high basis weight fabric M0 and low basis weight fabric H0. The low basis weight original fabric H0 is pretreated by hot pressing to obtain product H0'; S2, Lamination Hot Pressing: High basis weight original fabric M0 and low basis weight original fabric H0' after hot pressing pretreatment are stacked and hot pressed to obtain composite nonwoven fabric, namely product M1H1. S3, Functional Solution Treatment: A functional solution containing para-aramid nanofibers and hexadecyltrimethylammonium bromide-modified nano-calcium carbonate was impregnated onto a composite nonwoven fabric M1H1; then, the composite nonwoven fabric impregnated with the functional solution was cold-pressed to obtain a nanomaterial-modified composite nonwoven fabric. S4. The second hot pressing process yields the polyester nonwoven fabric, which is product M2H2.

2. The method for preparing a polyester nonwoven fabric according to claim 1, characterized in that, In step S1, the basis weight of the high-basis-weight original fabric M0 is 40-55 g / m³. 2 The basis weight of low basis weight original fabric H0 is 15-30 g / m³. 2 ; When preparing high basis weight fabric M0, the polyester main fiber is 65-85 parts and the polyester bonding fiber is 15-35 parts by weight. When preparing low-weight base fabric H0, the polyester main fiber is 70-80 parts by weight and the polyester bonding fiber is 20-30 parts by weight.

3. The method for preparing a polyester nonwoven fabric according to claim 1, characterized in that, In step S1, when preparing the high-weight base fabric M0, the fineness of the polyester main fiber is 0.5 dtex-1.0 dtex, and the length of the polyester main fiber is 3-6 mm. When preparing low-weight base fabric H0, the fineness of the polyester main fiber is 1.0 dtex-1.5 dtex, and the length of the polyester main fiber is 3-6 mm; When preparing high basis weight base fabric M0 and low basis weight base fabric H0, the fineness of the polyester bonding fiber is 1.2dtex-1.5dtex, and the length of the polyester bonding fiber is 3-6mm.

4. The method for preparing a polyester nonwoven fabric according to claim 1, characterized in that, In step S1, during the hot pressing pretreatment, a two-roll hot press is used, with a temperature of 130-170℃, a pressure of 50-80N / mm, and a speed of 5-10m / min. The hot press rollers are all steel rollers.

5. The method for preparing a polyester nonwoven fabric according to claim 1, characterized in that, In step S2, during the hot pressing of the lamination, a two-roller hot press is used, with a temperature of 180-220℃, a pressure of 60-90N / mm, and a speed of 5-15m / min. The upper roller is a nylon roller, and the lower roller is a steel roller.

6. The method for preparing a polyester nonwoven fabric according to claim 1, characterized in that, The preparation method of the functional solution is as follows: (1) Preparation of para-aramid nanofiber solution and modified nano-calcium carbonate: Para-aramid chopped fibers and potassium hydroxide were added to dimethyl sulfoxide, and then water was added to disperse them evenly to obtain the para-aramid nanofiber solution; wherein the weight ratio of para-aramid chopped fibers, dimethyl sulfoxide, water and potassium hydroxide was (1-3):(80-100):(0.01-0.08):(0.15-4). Nano-calcium carbonate was added to deionized water, ultrasonicated, and the pH was adjusted to 4-5 with dilute hydrochloric acid to obtain a nano-calcium carbonate suspension. Hexadecyltrimethylammonium bromide aqueous solution was slowly added dropwise to the nano-calcium carbonate suspension, stirred and ultrasonicated, and then modified nano-calcium carbonate was obtained by solid-liquid separation and drying. (2) Preparation of functional solutions: Modified nano-calcium carbonate is added to a para-aramid nanofiber solution and ultrasonically and stirred until homogeneous. Then, it is diluted and dispersed in water to obtain a functional solution. The mass of nano-calcium carbonate is 50%-70% of the mass of para-aramid nanofibers. The mass concentration of para-aramid nanofibers in the functional solution is 0.1-0.3%.

7. The method for preparing a polyester nonwoven fabric according to claim 1, characterized in that, In step S3, the cold pressing is carried out using a two-roll hot press, with a temperature of 25-30℃, a linear pressure of 40-60N / mm, and a speed of 5-10m / min. All hot press rollers are steel rollers. After step S3, the amount of functional solution impregnated on the composite nonwoven fabric is 10-15% of the dry weight of the composite nonwoven fabric.

8. The method for preparing a polyester nonwoven fabric according to claim 1, characterized in that, In step S4, during the second hot pressing process, a two-roller hot press is used, with a temperature of 180-220℃, a pressure of 70-110N / mm, and a speed of 5-15m / min. The upper roller is a steel roller, and the lower roller is a nylon roller.

9. A polyester nonwoven fabric, characterized in that, The polyester nonwoven fabric is prepared according to the preparation method described in any one of claims 1-8; The polyester nonwoven fabric includes a medium-density portion M2 and a high-density portion H2 in the thickness direction, wherein the density of the medium-density portion M2 is 0.69-0.75 g / cm³. 3 The density of the high-density portion H2 is 0.79-0.95 g / cm³. 3 The density difference between the high-density portion H2 and the medium-density portion M2 is 0.1-0.2 g / cm³. 3 .

10. An application of the polyester nonwoven fabric according to claim 9, characterized in that, The polyester nonwoven fabric is used as a support material for the reverse osmosis membrane.

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