A wet-laid nonwoven composite filtration material and method of making the same

Abstract

The present application relates to a kind of wet non-woven composite filter material and its preparation method, the method includes: fiber is impregnated pyrrole solution, obtain the fiber solution of adsorbed pyrrole;Pyrrole-adsorbed fiber solution is made into slurry, then add oxidizing agent to slurry and carry out in-situ polymerization, obtain the slurry to be shaped;The wet non-woven composite filter material is prepared by wet forming to the slurry to be shaped.The present application is adsorbed by impregnation method on the surface of fiber pyrrole monomer, under the action of oxidizing agent, in-situ growth polypyrrole conductive layer on the surface of fiber, composite conductive fiber is prepared into filter material using wet forming method, effectively improve the conductive performance of filter material, its resistivity is far less than the resistivity of filter material prepared by adding other conductive fibers in prior art, the present application obtains a kind of filter material with stable and efficient antistatic and filtering performance.

Description

Technical Field

[0001] This invention belongs to the field of filtration and separation materials technology, and particularly relates to a wet nonwoven composite filter material and its preparation method. Background Technology

[0002] Glass fiber wet-laid nonwoven materials, with their high filtration efficiency, superior chemical and thermal stability, and high dust holding capacity, have a wider range of applications in air and liquid filtration and separation, especially in high-end liquid filtration. In recent years, driven by environmental protection and green development needs, the formulations of hydraulic oils and lubricating oils have been improved. The reduction in the use of organometallic additives (such as zinc dithiophosphate) has lowered the conductivity of the oil, increasing the risk of electrostatic charge generation. Hydraulic oil flowing through the system easily generates electrostatic charges at the interface between the oil and non-conductive surfaces, especially since the non-conductive surface area of ​​the filter element is large. As the oil flow rate increases, the charge accumulates. When the charge is large enough, it will discharge via sparks. This can cause localized damage to the filter media, forming porosity, preventing the filtration of dirt particles in the oil, leading to wear on hydraulic components and equipment failure. Simultaneously, the high temperature of the discharge sparks accelerates oil aging and shortens its service life. Furthermore, nearby electronic components can also be damaged by the discharge. To avoid these problems, the charge must be balanced.

[0003] In light of the above background, there are antistatic hydraulic filter products on the market that use antistatic filter materials. In recent years, many researchers have also studied this technology. For example, Chinese patent application CN112452052A introduces conductive fibers such as metal fibers, carbon black fibers, conductive metal compound fibers, and conductive polymer fibers to prepare filter media. By controlling the number of conductive fibers per unit volume, an electrostatic subconductor filter material with antistatic properties is obtained. However, in the actual production process, due to the difference in properties such as density between conductive fibers and glass fibers, the method in this patent application is prone to uneven fiber dispersion, which may lead to the problem that conductive paths cannot be formed in some areas. Moreover, the antistatic performance of the filter material obtained by this patent application is still relatively poor.

[0004] In summary, how to obtain a filter material with stable and efficient antistatic and filtration properties is an urgent problem to be solved. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, this invention provides a wet-laid nonwoven composite filter material and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing a wet-laid nonwoven composite filter material, the method comprising the following steps:

[0007] (1) Impregnate the fiber with pyrrole solution to obtain a fiber solution with pyrrole adsorbed;

[0008] (2) Prepare a slurry by adsorbing pyrrole fiber solution, and then add an oxidant to the slurry for in-situ polymerization to obtain the slurry to be formed;

[0009] (3) The slurry to be formed is wet-formed to obtain wet-process nonwoven composite filter material.

[0010] Preferably, in step (2), an oxidant is added to the slurry to allow pyrrole to polymerize in situ on the fiber surface, thereby generating a composite conductive fiber with fiber as the core layer and polypyrrole as the skin layer in the slurry, and obtaining a slurry containing the composite conductive fiber to be formed.

[0011] Preferably, the oxidant is one or more of ferric chloride, copper chloride, ammonium persulfate, potassium dichromate, hydrogen peroxide, and potassium permanganate; more preferably, the oxidant is ferric chloride.

[0012] Preferably, in step (1), the fiber is a pretreated fiber, which is impregnated with a pyrrole solution to obtain a fiber solution adsorbed with pyrrole; the pretreated fiber is prepared by soaking the fiber in a solvent for 1 to 3 hours, then washing and drying, and optionally performing oxygen plasma treatment to obtain the pretreated fiber; preferably, the solvent is an alcohol or ketone solvent with a boiling point not greater than 100°C, more preferably, the solvent is one or more of methanol, ethanol, isopropanol, acetone, and butanone.

[0013] Preferably, the fiber in step (1) is one or more of chopped glass fiber, fiberglass wool, and organic fiber; preferably, the glass fiber has a length of 2-4 mm and a diameter of 5-7 μm, the fiberglass wool has a length of 5-7 mm and a diameter of 2-4 μm, and the organic fiber has a length of 4-6 mm and a diameter of 12-14 μm; preferably, the fiberglass wool is type 475 fiberglass wool, and the organic fiber is one or more of PET fiber, PAN fiber, PE fiber, and PP fiber; preferably, the fiber is composed of chopped glass fiber, fiberglass wool, and organic fiber in a mass ratio of (8-10):(50-60):(0.5-3).

[0014] Preferably, the impregnation is performed by immersing the fiber in a pyrrole solution for 0.5 to 1.5 hours, followed by ultrasonic treatment for 10 to 30 minutes; the pyrrole solution is an aqueous pyrrole solution; the concentration of pyrrole in the pyrrole solution is 0.01 to 0.8 mol / L, preferably 0.05 to 0.2 mol / L; and / or the molar ratio of the oxidant in step (2) to the pyrrole in the pyrrole solution in step (1) is (0.2 to 0.3):1, preferably 0.238:1.

[0015] Preferably, the in-situ polymerization temperature is 10-30℃, more preferably 15-20℃, and the in-situ polymerization time is 0.1-8h, more preferably 0.5-1h.

[0016] Preferably, in step (2), the slurry contains 0.8 to 1.25‰ by mass of fibers adsorbed with pyrrole, more preferably 1 to 1.25‰.

[0017] Preferably, before wet molding the slurry to be molded, the pH of the slurry to be molded is adjusted to 2.5 to 3.0.

[0018] In a second aspect, the present invention provides a wet-laid nonwoven composite filter material prepared by the preparation method described in the first aspect of the present invention.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] (1) This invention adsorbs pyrrole monomers on the fiber surface by impregnation, and grows a polypyrrole conductive layer in situ on the fiber surface under the action of an oxidant. The composite conductive fiber is then prepared into a filter material by a wet forming method, which effectively improves the conductivity and antistatic properties of the filter material. Its resistivity is much lower than that of filter materials prepared by adding other conductive fibers in the prior art. This solves the problem that traditional glass fiber wet nonwoven materials do not have conductivity and will cause local damage to the filter material due to the accumulation and discharge of static charge during the oil filtration process, reducing the filtration accuracy and causing oil aging. The present invention provides a filter material with stable and efficient antistatic and filtration properties.

[0021] (2) In this invention, polypyrrole is grown in situ on the surface of mixed fibers to obtain composite fibers with conductive properties, which are then prepared as antistatic filter materials. The composite conductive fibers in this invention have a core-sheath structure, with polypyrrole mainly concentrated in the sheath layer and the mixed fibers as the core layer, which can form a stable and efficient conductive channel. The growth of polypyrrole on the fiber surface in this invention does not affect the filtration performance of the filter material, and the filtration performance of the prepared filter material is still excellent. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation process in some specific embodiments of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] In a first aspect, the present invention provides a method for preparing a wet-laid nonwoven composite filter material, the method comprising the following steps:

[0025] (1) Impregnate the fiber with a pyrrole solution to obtain a fiber solution adsorbed with pyrrole; in this invention, the fiber solution adsorbed with pyrrole refers to a solution containing fibers adsorbed with pyrrole.

[0026] (2) Prepare a slurry by adsorbing pyrrole fiber solution, and then add an oxidant to the slurry for in-situ polymerization to obtain the slurry to be formed;

[0027] (3) The slurry to be formed is wet-processed to obtain a wet-process nonwoven composite filter material; in this invention, the wet-processing is wet-process papermaking.

[0028] According to some preferred embodiments, in step (2), an oxidant is added to the slurry to allow pyrrole to polymerize in situ on the fiber surface, thereby generating a composite conductive fiber with fiber as the core layer and polypyrrole as the sheath layer in the slurry, and obtaining a slurry containing the composite conductive fiber to be formed; in this invention, the composite conductive fiber has a core-sheath structure.

[0029] This invention adsorbs pyrrole monomers onto the fiber surface via impregnation. Under the action of an oxidant, a polypyrrole conductive layer is grown in situ on the fiber surface. The composite conductive fiber is then prepared into a filter material using a wet molding method. This effectively improves the conductivity and antistatic properties of the filter material, and its resistivity is much lower than that of filter materials prepared by adding other conductive fibers in existing technologies. This invention grows polypyrrole in situ on the surface of mixed fibers to obtain a conductive composite fiber, which is then prepared into an antistatic filter material. The composite conductive fiber in this invention has a core-sheath structure, with polypyrrole mainly concentrated in the sheath layer and the mixed fibers serving as the core layer, forming a stable and efficient conductive channel. The growth of polypyrrole on the fiber surface does not affect the filtration performance of the filter material; the prepared filter material still exhibits excellent filtration performance and is a filter material with stable and efficient antistatic and filtration properties.

[0030] This invention achieves a more uniform and continuous polypyrrole conductive layer by in-situ polymerization of pyrrole on the fiber surface. This results in more consistent conductivity throughout the filter material, significantly improving its conductivity and antistatic properties. Furthermore, by fixing the polypyrrole to the fiber surface, the conductive layer is more firmly bonded and less susceptible to environmental factors, thus enhancing the filter material's durability and stability. This invention also reveals that directly impregnating wet-formed filter material with a pyrrole solution for in-situ polymerization to form a conductive layer leads to uneven distribution of polypyrrole within and on the surface of the filter material, resulting in a discontinuous conductive layer. This causes unstable conductivity and provides little improvement to the filter material's conductivity. Moreover, impregnating already formed filter material with a pyrrole solution for polymerization can cause the conductive layer to clog the pores of the filter material, affecting its permeability and filtration efficiency. Additionally, the resulting conductive layer is not firmly bonded and is prone to detachment or peeling during use, reducing the filter material's durability.

[0031] According to some preferred embodiments, the oxidant is one or more of ferric chloride, copper chloride, ammonium persulfate, potassium dichromate, hydrogen peroxide, and potassium permanganate; preferably, the oxidant is ferric chloride, such as ferric chloride hexahydrate. In this invention, it is preferred that the oxidant be ferric chloride, as this facilitates the effective oxidization of pyrrole to form a uniform polypyrrole conductive layer on the fiber surface through in-situ polymerization. This, in turn, improves the conductivity and antistatic properties of the wet-laid nonwoven composite filter material. While other oxidants can also produce different composite fibers, their polymerization rate is very slow, making it impossible to effectively polymerize in-situ on the fiber surface to form a polypyrrole conductive layer, resulting in poor conductivity.

[0032] According to some preferred embodiments, in step (1), the fiber is a pretreated fiber, which is impregnated with a pyrrole solution to obtain a fiber solution adsorbed with pyrrole; the pretreated fiber is prepared by soaking the fiber in a solvent for 1-3 hours (e.g., 1, 1.5, 2, 2.5 or 3 hours), then washing and drying, and optionally undergoing oxygen plasma treatment to obtain the pretreated fiber; in this invention, the oxygen plasma treatment is performed in an oxygen atmosphere, with a power of 60-80W, for a time of 5-15 minutes (e.g., 5, 8, 10 or 15 minutes); in this invention, it is preferred to treat the fiber... The process involves oxygen plasma treatment followed by impregnation with a pyrrole solution. This invention has found that oxygen plasma treatment enhances the interaction between pyrrole molecules and fibers, improving the fiber's adsorption of pyrrole and resulting in a more uniform distribution of pyrrole on the fibers. This also facilitates a more uniform in-situ polymerization process, leading to a more uniform and robust polypyrrole conductive layer formed on the fiber surface. This further improves the conductivity and antistatic properties of the wet-laid nonwoven composite filter material. Preferably, the solvent is an alcohol or ketone solvent with a boiling point not exceeding 100°C. More preferably, the solvent is one or more of methanol, ethanol, isopropanol, acetone, and butanone.

[0033] According to some preferred embodiments, the pretreated fiber is prepared by: soaking the fiber in a solvent for 1 to 3 hours, then washing and drying it, and then subjecting the dried fiber to oxygen plasma treatment to obtain the pretreated fiber; in this invention, the washing can be carried out, for example, using deionized water, and the drying can be carried out, for example, by air drying at room temperature (room temperature 15 to 35°C) to constant weight.

[0034] According to some preferred embodiments, the fiber in step (1) is one or more of chopped glass fiber, fiberglass wool, and organic fiber; preferably, the glass fiber has a length of 2-4 mm and a diameter of 5-7 μm, the fiberglass wool has a length of 5-7 mm and a diameter of 2-4 μm, and the organic fiber has a length of 4-6 mm and a diameter of 12-14 μm; preferably, the fiberglass wool is type 475 fiberglass wool, and the organic fiber is PET fiber (polyethylene terephthalate fiber), PAN fiber (polyacrylonitrile fiber), PE fiber (polyethylene fiber), or PP fiber (polypropylene fiber). The organic fiber is selected from one or more of the following: chopped glass fiber, type 475 glass fiber cotton, PET fiber, PAN fiber, PE fiber, PP fiber, etc. The present invention does not specifically limit the source of the chopped glass fiber, type 475 glass fiber cotton, etc., and any commercially available products can be used. In some specific embodiments, the fiber is selected from at least one of the following groups: chopped glass fiber with a length of 3±0.5mm and a diameter of 6±0.5μm, type 475 glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, and organic fiber with a length of 5±0.5mm and a diameter of 13±0.5μm.

[0035] According to some preferred embodiments, the fiber is composed of chopped glass fiber, fiberglass wool and organic fiber in a mass ratio of (8-10):(50-60):(0.5-3).

[0036] According to some preferred embodiments, the wet nonwoven composite filter material contains 5-25% by mass of chopped glass fibers, 50-80% by mass of glass fiber cotton, and / or 0-8% by mass of organic fibers.

[0037] According to some preferred embodiments, the impregnation involves immersing the fibers in a pyrrole solution for 0.5–1.5 hours, followed by ultrasonic treatment for 10–30 minutes. During the impregnation, the mass ratio of the fibers to the pyrrole solution can be, for example, 1:(80–150), preferably 1:100. The pyrrole solution is an aqueous pyrrole solution, which in this invention consists of pyrrole and water. The concentration of pyrrole in the pyrrole solution is 0.01–0.8 mol / L (e.g., 0.01, 0.05, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8 mol / L). The oxidant in step (2) and the pyrrole solution in step (1) contain pyrrole in a molar ratio of (0.2 to 0.3):1 (e.g., 0.2:1, 0.21:1, 0.22:1, 0.23:1, 0.24:1, 0.25:1, 0.26:1, 0.27:1, 0.28:1, 0.29:1 or 0.3:1), with the optimal initial molar ratio of oxidant to pyrrole preferably being 0.238:1.

[0038] According to some preferred embodiments, the in-situ polymerization temperature is 10–30°C (e.g., 10°C, 15°C, 20°C, 25°C, or 30°C), preferably 15–20°C, more preferably 20°C, and the in-situ polymerization time is 0.1–8 h (e.g., 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, or 8 h), preferably 0.5–1.5 h (e.g., 0.5, 1, or 1.5 h), more preferably 0.5 h.

[0039] In this invention, it is preferred to control the concentration of pyrrole in the pyrrole solution to be 0.01–0.8 mol / L, and to carry out in-situ polymerization at a temperature of 10–30°C for a time of 0.1–8 h. This effectively ensures the formation of a uniform and dense polypyrrole conductive layer on the fiber surface, which helps to form a composite core-sheath structure with fiber as the core layer and polypyrrole as the sheath layer. This effectively improves the conductivity and antistatic properties of the wet-laid nonwoven composite filter material. However, if the concentration of the pyrrole solution is too high, or the in-situ polymerization temperature or polymerization time is too long, it will lead to over-polymerization of pyrrole, forming excessively large polypyrrole particles, affecting the uniformity and density of the polypyrrole conductive layer, and adversely affecting the conductivity of the composite conductive fiber.

[0040] According to some preferred embodiments, in step (2), the slurry contains 0.8 to 1.25‰ (e.g., 0.8‰, 0.9‰, 1‰, 1.1‰, 1.2‰ or 1.25‰) of fiber adsorbed with pyrrole, preferably 1 to 1.25‰; in this invention, "‰" means one-thousandth.

[0041] According to some preferred embodiments, before wet molding the slurry to be molded, the pH of the slurry to be molded is adjusted to 2.5-3.0. In this invention, for example, sulfuric acid solution can be used to adjust the pH of the slurry to be molded. This invention does not specifically limit the sulfuric acid solution, as long as the pH of the slurry to be molded is adjusted to the target range. And / or during the wet molding process, a fluorocarbon waterproofing agent is added. Preferably, the fluorocarbon waterproofing agent is a C6 waterproofing agent. Preferably, the amount of the fluorocarbon waterproofing agent is 8-12% (e.g., 8%, 9%, 10%, 11% or 12%) of the mass of the slurry to be molded, preferably 10%.

[0042] According to some specific embodiments, the preparation of the wet-laid nonwoven composite filter material includes the following steps:

[0043] ① Soak the mixed fibers (including type 475 glass fiber cotton, chopped glass fiber and organic fiber) in a solvent, wash off the surface oil, wash with deionized water, and air dry at room temperature (e.g., room temperature 15-35℃) until constant weight; then immerse the mixed fibers in a pyrrole aqueous solution to allow the fiber surface to fully adsorb pyrrole monomers, and obtain a fiber solution adsorbed with pyrrole.

[0044] ② The fiber solution adsorbed with pyrrole is evenly dispersed in water and subjected to decomposition treatment to obtain a slurry. An oxidant is added to the slurry, and a polypyrrole conductive layer is generated in situ on the fiber surface under a certain temperature and time. A composite conductive fiber with fiber as core layer and polypyrrole as skin layer is generated in the slurry, and a slurry containing composite conductive fiber is obtained.

[0045] ③ The pH of the slurry to be formed is adjusted using a sulfuric acid solution (e.g., dilute sulfuric acid), and then a wet-process nonwoven composite filter material is prepared according to a wet-process forming method (i.e., a wet-process papermaking method). In this invention, the wet-process papermaking method is a conventional technique in the field, and this invention does not impose specific limitations. It includes steps such as slurry preparation and papermaking, web forming, sizing, drying, curing, and / or curling. In this invention, for example, the concentration of the sizing agent can be 0.2–0.25 wt‰. In this invention, sizing can be performed, for example, by a curtain coating method, using an acrylic emulsion for sizing treatment. The amount of sizing agent can, for example, account for a certain percentage of the wet-process nonwoven composite filter material. The solid content is 3-6% by mass; in this invention, the acrylic emulsion can be any commercially available acrylic latex, and the solid content of the acrylic latex (acrylic emulsion) can be, for example, 25-50 wt%; in this invention, the drying can be, for example, drying to constant weight at 120±5℃, using a gradient heating method from room temperature to 120±5℃, the gradient heating method being: the heating rate from room temperature to 90℃ is 50±10℃ / min, and the heating rate from 90℃ to 120℃ is 10±5℃ / min; the curing is, for example, curing at 155-165℃ for 7-15 min.

[0046] In a second aspect, the present invention provides a wet-laid nonwoven composite filter material prepared by the preparation method described in the first aspect of the present invention.

[0047] The present invention will be further described below with reference to the embodiments. These embodiments are merely illustrative examples of preferred implementations of the present invention, and the scope of protection of the present invention should not be construed as being limited to these embodiments.

[0048] Example 1

[0049] ① 8.98g of chopped glass fibers with a length of 3±0.5mm and a diameter of 6±0.5μm, 51.87g of 475 type glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, and 1.33g of organic fibers (PET fibers) with a length of 5±0.5mm and a diameter of 13±0.5μm were added to acetone and soaked at room temperature for 2 hours. After washing off the surface oil, the fibers were washed with deionized water and air-dried to constant weight to obtain fibers (mixed fibers). The mixed fibers, after removing the oil and being washed and dried, were placed in a pyrrole aqueous solution (pyrrole solution) and soaked at room temperature for 1 hour. Then, they were ultrasonically treated for 20 minutes to allow the fibers to fully adsorb pyrrole monomers, resulting in a fiber solution adsorbed with pyrrole. The concentration of pyrrole in the pyrrole solution was 0.05mol / L, and the mass ratio of the mixed fibers to the pyrrole solution during room temperature soaking was 1:100.

[0050] ② The fiber solution adsorbed with pyrrole is evenly dispersed in water and subjected to desorption treatment to obtain a slurry. The mass percentage of the fiber adsorbed with pyrrole in the slurry is 1‰. An oxidant, ferric chloride hexahydrate FeCl3·6H2O, is added to the slurry. The reaction temperature is 20℃, which allows pyrrole to polymerize in situ on the fiber surface to form a polypyrrole conductive layer. The in-situ polymerization time is 0.5h. A composite conductive fiber with fiber as the core layer and polypyrrole as the skin layer is generated in the slurry, and a slurry containing the composite conductive fiber is obtained. The molar ratio of the amount of oxidant FeCl3·6H2O to the amount of pyrrole in the pyrrole solution in step ① is 0.238:1.

[0051] ③ The pH of the slurry to be formed is adjusted to 2.5 using dilute sulfuric acid, and then water is added to form a wet substrate at a papermaking concentration of 0.20 wt‰, following the wet papermaking method. The wet substrate is then sized using a curtain coating method, specifically using acrylic emulsion for sizing, with the sizing amount controlled at 3.5 g. The sized substrate is then dried at 120°C until it reaches constant weight, and then cured to obtain a wet nonwoven composite filter material. During drying, a gradient heating method is used to raise the temperature from room temperature to 120°C. The gradient heating rate is 50°C / min from room temperature to 90°C, and 10°C / min from 90°C to 120°C. The curing is carried out at 160°C for 10 min.

[0052] Example 2

[0053] Example 2 is basically the same as Example 1, except that:

[0054] ① 8.98g of chopped glass fibers (3±0.5mm in length, 6±0.5μm in diameter), 51.87g of type 475 fiberglass wool (6±0.5mm in length, 2.5±0.5μm in diameter), and 1.33g of organic fibers (PET fibers) (5±0.5mm in length, 13±0.5μm in diameter) were added to acetone and soaked at room temperature for 2 hours. After washing off the surface oil, the fibers were washed with deionized water and air-dried to constant weight to obtain fibers (mixed fibers). The mixed fibers, after being degreased, washed, and dried, were then subjected to oxygen plasma treatment. The atmosphere of the oxygen plasma treatment was... Oxygen was used, the power was 70W, and the time was 8min to obtain oxygen plasma-treated fibers (pretreated fibers). The pretreated fibers were placed in a pyrrole aqueous solution (pyrrole solution) and soaked at room temperature for 1h, and then ultrasonically treated for 20min to allow the fibers to fully adsorb pyrrole monomers, resulting in a fiber solution with adsorbed pyrrole. This fiber solution with adsorbed pyrrole was used for subsequent steps ② and ③. The concentration of pyrrole in the pyrrole solution was 0.05mol / L, and the mass ratio of the mixed fibers to the pyrrole solution during room temperature soaking was 1:100.

[0055] Example 3

[0056] Example 3 is basically the same as Example 1, except that:

[0057] ① 8.98g of chopped glass fibers with a length of 3±0.5mm and a diameter of 6±0.5μm, 51.87g of type 475 glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, and 1.33g of organic fibers (PET fibers) with a length of 5±0.5mm and a diameter of 13±0.5μm were added to acetone and soaked at room temperature for 2 hours. After washing off the surface oil, the fibers were washed with deionized water and air-dried to constant weight to obtain fibers (mixed fibers). The mixed fibers, after removing the oil and being washed and dried, were placed in a pyrrole aqueous solution (pyrrole solution) and soaked at room temperature for 1 hour. Then, they were ultrasonically treated for 20 minutes to allow the fibers to fully adsorb pyrrole monomers, resulting in a fiber solution adsorbed with pyrrole. The concentration of pyrrole in the pyrrole solution was 0.8mol / L, and the mass ratio of the mixed fibers to the pyrrole solution during room temperature soaking was 1:100.

[0058] ② The fiber solution adsorbed with pyrrole is evenly dispersed in water and subjected to desorption treatment to obtain a slurry. The slurry contains 1‰ of the fiber adsorbed with pyrrole by mass. An oxidant FeCl3·6H2O is added to the slurry, and the pyrrole is polymerized in situ on the fiber surface at a reaction temperature of 30℃ to form a polypyrrole conductive layer. The in situ polymerization time is 1.5h, and a composite conductive fiber with fiber as the core layer and polypyrrole as the skin layer is generated in the slurry, resulting in a slurry containing the composite conductive fiber to be formed. The molar ratio of the amount of oxidant FeCl3·6H2O to the amount of pyrrole contained in the pyrrole solution in step ① is 0.238:1.

[0059] Example 4

[0060] Example 4 is basically the same as Example 1, except that:

[0061] ① 8.98g of chopped glass fibers with a length of 3±0.5mm and a diameter of 6±0.5μm, 51.87g of type 475 glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, and 1.33g of organic fibers (PET fibers) with a length of 5±0.5mm and a diameter of 13±0.5μm were added to acetone and soaked at room temperature for 2 hours. After washing off the surface oil, the fibers were washed with deionized water and air-dried to constant weight to obtain fibers (mixed fibers). The mixed fibers, after removing the oil and being washed and dried, were placed in a pyrrole aqueous solution (pyrrole solution) and soaked at room temperature for 1 hour. Then, they were ultrasonically treated for 20 minutes to allow the fibers to fully adsorb pyrrole monomers, resulting in a fiber solution adsorbed with pyrrole. The concentration of pyrrole in the pyrrole solution was 1mol / L, and the mass ratio of the mixed fibers to the pyrrole solution during room temperature soaking was 1:100.

[0062] ② The fiber solution adsorbed with pyrrole is evenly dispersed in water and subjected to desorption treatment to obtain a slurry. The mass percentage of the fiber adsorbed with pyrrole in the obtained slurry is 1‰. An oxidant FeCl3·6H2O is added to the slurry, and the pyrrole is polymerized in situ on the fiber surface at a reaction temperature of 35℃ to form a polypyrrole conductive layer. The in-situ polymerization time is 8h, and a slurry containing composite conductive fibers is obtained. The molar ratio of the amount of oxidant FeCl3·6H2O to the amount of pyrrole contained in the pyrrole solution in step ① is 0.238:1.

[0063] Example 5

[0064] Example 5 is basically the same as Example 1, except that:

[0065] ② The fiber solution adsorbed with pyrrole is evenly dispersed in water and subjected to desorption treatment to obtain a slurry. The mass percentage of the fiber adsorbed with pyrrole in the obtained slurry is 1‰. Copper chloride dihydrate, an oxidant, is added to the slurry, and the pyrrole is polymerized in situ on the fiber surface at a reaction temperature of 20°C for 0.5 h to obtain the slurry to be formed. The molar ratio of the amount of copper chloride dihydrate to the amount of pyrrole in the pyrrole solution in step ① is 0.238:1.

[0066] Example 6

[0067] Example 6 is basically the same as Example 1, except that:

[0068] ② The fiber solution adsorbed with pyrrole is evenly dispersed in water and subjected to delamination treatment to obtain a slurry. The mass percentage of the fiber adsorbed with pyrrole in the obtained slurry is 1‰. Ammonium persulfate, an oxidant, is added to the slurry, and the pyrrole is polymerized in situ on the fiber surface at a reaction temperature of 20°C for 0.5 h to obtain the slurry to be formed. The molar ratio of the amount of ammonium persulfate to the amount of pyrrole in the pyrrole solution in step ① is 0.238:1.

[0069] Example 7

[0070] Example 7 is basically the same as Example 1, except that:

[0071] ② The fiber solution adsorbed with pyrrole is evenly dispersed in water and subjected to desorption treatment to obtain a slurry. The slurry contains 1‰ of the fiber with adsorbed pyrrole by mass. Potassium dichromate, an oxidant, is added to the slurry, and the pyrrole is polymerized in situ on the fiber surface at a reaction temperature of 20°C for 0.5 h to obtain the slurry to be formed. The molar ratio of the amount of potassium dichromate to the amount of pyrrole contained in the pyrrole solution in step ① is 0.238:1.

[0072] Example 8

[0073] Example 8 is basically the same as Example 1, except that:

[0074] ② The fiber solution adsorbed with pyrrole is evenly dispersed in water and subjected to delamination treatment to obtain a slurry. The slurry contains 1‰ of the fiber with adsorbed pyrrole by mass. Hydrogen peroxide is added to the slurry as an oxidant, and the pyrrole is polymerized in situ on the fiber surface at a reaction temperature of 20°C for 0.5 h to obtain the slurry to be formed. The molar ratio of the amount of hydrogen peroxide to the amount of pyrrole in the pyrrole solution in step ① is 0.238:1.

[0075] Example 9

[0076] Example 9 is basically the same as Example 1, except that:

[0077] ② The fiber solution adsorbed with pyrrole is evenly dispersed in water and subjected to desorption treatment to obtain a slurry. The slurry contains 1‰ of the fiber with adsorbed pyrrole by mass. Potassium permanganate, an oxidant, is added to the slurry, and the pyrrole is polymerized in situ on the fiber surface at a reaction temperature of 20°C for 0.5 h to obtain the slurry to be formed. The molar ratio of the amount of potassium permanganate to the amount of pyrrole contained in the pyrrole solution in step ① is 0.238:1.

[0078] Comparative Example 1

[0079] ① Add 8.98g of short glass fibers with a length of 3±0.5mm and a diameter of 6±0.5μm, 51.87g of 475 type glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, 1.33g of organic fiber (PET fiber) with a length of 5±0.5mm and a diameter of 13±0.5μm, and 1.34g of carbon fiber to acetone and soak at room temperature for 2 hours. After washing off the surface oil, wash with deionized water and air dry naturally to constant weight to obtain mixed fibers.

[0080] ② The mixed fibers are evenly dispersed in water and subjected to a loosening treatment to obtain a slurry. The mass percentage of the mixed fibers in the obtained slurry is 1‰.

[0081] ③ The pH of the slurry was adjusted to 2.5 using dilute sulfuric acid, and then water was added to form a wet substrate at a papermaking concentration of 0.20 wt‰, following the wet papermaking method. The wet substrate was then sizing (coating) using a curtain coating method, specifically using acrylic emulsion for sizing, with the sizing amount controlled at 3.5 g. The sizing substrate was then dried at 120°C until constant weight, and then cured to obtain a wet nonwoven composite filter material. During drying, a gradient heating method was used to raise the temperature from room temperature to 120°C. The gradient heating rate was 50°C / min from room temperature to 90°C, and 10°C / min from 90°C to 120°C. The curing was carried out at 160°C for 10 min.

[0082] Comparative Example 2

[0083] Comparative Example 2 is basically the same as Comparative Example 1, except that:

[0084] ① Add 8.98g of short glass fibers with a length of 3±0.5mm and a diameter of 6±0.5μm, 51.87g of 475 type glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, 1.33g of organic fiber (PET fiber) with a length of 5±0.5mm and a diameter of 13±0.5μm, and 9.98g of PANI conductive fiber (polyaniline fiber) to acetone and soak at room temperature for 2 hours. After washing off the surface oil, wash with deionized water and air dry naturally to constant weight to obtain mixed fibers.

[0085] Comparative Example 3

[0086] Comparative Example 3 is basically the same as Comparative Example 1, except that:

[0087] ① Add 8.98g of short glass fibers with a length of 3±0.5mm and a diameter of 6±0.5μm, 51.87g of 475 type glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, 1.33g of organic fiber (PET fiber) with a length of 5±0.5mm and a diameter of 13±0.5μm, and 5.62g of copper fiber to acetone and soak at room temperature for 2 hours. After washing off the surface oil, wash with deionized water and air dry naturally to constant weight to obtain mixed fibers.

[0088] Comparative Example 4

[0089] Comparative Example 4 is basically the same as Comparative Example 1, except that:

[0090] ① Add 8.98g of short glass fibers with a length of 3±0.5mm and a diameter of 6±0.5μm, 51.87g of 475 type glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, 1.33g of organic fiber (PET fiber) with a length of 5±0.5mm and a diameter of 13±0.5μm, and 6.62g of nylon-based conductive fiber (nylon-based white conductive fiber) to acetone and soak at room temperature for 2 hours. After washing off the surface oil, wash with deionized water and air dry naturally to constant weight to obtain mixed fibers.

[0091] Comparative Example 5

[0092] Comparative Example 5 is basically the same as Comparative Example 1, except that:

[0093] ① Add 8.98g of short glass fibers with a length of 3±0.5mm and a diameter of 6±0.5μm, 51.87g of 475 type glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, 1.33g of organic fiber (PET fiber) with a length of 5±0.5mm and a diameter of 13±0.5μm, and 5.43g of polypyrrole fiber to acetone and soak at room temperature for 2 hours. After washing off the surface oil, wash with deionized water and air dry naturally to constant weight to obtain mixed fibers.

[0094] Comparative Example 6

[0095] ① Add 8.98g of short glass fibers with a length of 3±0.5mm and a diameter of 6±0.5μm, 51.87g of 475 type glass fiber cotton with a length of 6±0.5mm and a diameter of 2.5±0.5μm, and 1.33g of organic fibers (PET fibers) with a length of 5±0.5mm and a diameter of 13±0.5μm to acetone and soak at room temperature for 2 hours. After washing off the surface oil, wash with deionized water and air dry to constant weight to obtain fibers (mixed fibers).

[0096] ② The mixed fibers are evenly dispersed in water and subjected to a loosening treatment to obtain a slurry. The mass percentage of the mixed fibers in the obtained slurry is 1‰.

[0097] ③ The pH of the slurry was adjusted to 2.5 using dilute sulfuric acid, and then water was added to form a wet substrate at a papermaking concentration of 0.20 wt‰, following the wet papermaking method. The wet substrate was then sizing (coating) using a curtain coating method, specifically using acrylic emulsion for sizing, with the sizing amount controlled at 3.5 g. The sizing substrate was dried at 120°C until constant weight, and then cured to obtain wet nonwoven filter material. During drying, a gradient heating method was used to raise the temperature from room temperature to 120°C. The gradient heating rate was 50°C / min from room temperature to 90°C and 10°C / min from 90°C to 120°C. The curing was carried out at 160°C for 10 min.

[0098] ④ The wet nonwoven filter material is immersed in a pyrrole aqueous solution (pyrrole solution) at room temperature for 1 hour, and then ultrasonically treated for 20 minutes to allow the wet nonwoven filter material to fully adsorb pyrrole monomers, resulting in a wet nonwoven filter material solution adsorbed with pyrrole. The concentration of pyrrole in the pyrrole solution is 0.05 mol / L. During room temperature immersion, the mass ratio of the wet nonwoven filter material to the pyrrole solution is 1:100. Then, oxidant ferric chloride hexahydrate FeCl3·6H2O is added to the wet nonwoven filter material solution adsorbed with pyrrole, and a polymerization reaction is carried out at a reaction temperature of 20°C for 0.5 hours. The molar ratio of the amount of oxidant FeCl3·6H2O to the amount of pyrrole in the pyrrole solution is 0.238:1. After the polymerization reaction, the material is washed with deionized water and dried to constant weight to obtain a wet nonwoven composite filter material.

[0099] Comparative Example 7

[0100] Comparative Example 7 is basically the same as Comparative Example 6, except that:

[0101] ④ The wet nonwoven filter material is placed in a pyrrole aqueous solution (pyrrole solution) and soaked at room temperature for 1 hour, followed by ultrasonic treatment for 20 minutes to allow the wet nonwoven filter material to fully adsorb pyrrole monomers, resulting in a wet nonwoven filter material solution adsorbed with pyrrole. The concentration of pyrrole in the pyrrole solution is 0.05 mol / L. During room temperature soaking, the mass ratio of the wet nonwoven filter material to the pyrrole solution is 1:100. Then, oxidant ferric chloride hexahydrate FeCl3·6H2O is added to the wet nonwoven filter material solution adsorbed with pyrrole, and a polymerization reaction is carried out at a reaction temperature of 35°C for 1 hour. The molar ratio of the amount of oxidant FeCl3·6H2O to the amount of pyrrole in the pyrrole solution is 0.238:1. After the polymerization reaction, the material is washed with deionized water and dried to constant weight to obtain a wet nonwoven composite filter material.

[0102] Comparative Example 8

[0103] Comparative Example 8 is basically the same as Comparative Example 6, except that:

[0104] ④ The wet nonwoven filter material was soaked in an aqueous solution of ferric chloride hexahydrate (FeCl3·6H2O) for 1 hour, then sonicated for 20 minutes, and then dried before being placed in a sealed container containing pyrrole monomer for gas-phase polymerization. The gas-phase polymerization temperature was 40°C, the polymerization time was 4 hours, and the amount of pyrrole monomer used was 0.1 mL. The mass ratio of the wet nonwoven filter material to the aqueous solution of ferric chloride hexahydrate (FeCl3·6H2O) was 1:100; the molar ratio of ferric chloride hexahydrate to pyrrole monomer was 0.238:1. After gas-phase polymerization, the material was washed with deionized water and dried to constant weight to obtain the wet nonwoven composite filter material.

[0105] The performance of the wet nonwoven composite filter materials prepared in each embodiment and comparative example was tested, and the results are shown in Table 1.

[0106] Table 1

[0107]

[0108] As can be seen from the results in Table 1, this invention effectively improves the conductivity and antistatic properties of the filter material by growing a polypyrrole conductive layer in situ on the surface of the raw material fibers. The resulting wet-laid nonwoven composite filter material has a surface resistivity as low as 3.9 × 10⁻⁶. 8 Ω~4.8×10 8 Ω, with a volume resistivity as low as 2.6 × 10⁻⁶. 7 ~3.3×10 7Ω·m; When ferric chloride hexahydrate is selected as the oxidant, the surface resistivity and volume resistivity are the lowest. Furthermore, the composite conductive fiber prepared in this invention exhibits a core-sheath structure, with polypyrrole mainly concentrated in the sheath layer. Therefore, the growth of polypyrrole on the fiber surface does not affect the filtration performance of the filter material, and the prepared filter material still exhibits excellent filtration performance with an air permeability of 140–146 mm·s. -1 The average pore size is 5.1–5.2 μm.

[0109] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in each embodiment, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a wet-laid nonwoven composite filter material, characterized in that, The method includes the following steps: (1) The fiber is impregnated with a pyrrole solution to obtain a fiber solution adsorbed with pyrrole; the fiber in step (1) is composed of chopped glass fiber, glass fiber cotton and organic fiber in a mass ratio of (8~10):(50~60):(0.5~3); the impregnation is: the fiber is soaked in the pyrrole solution for 0.5~1.5h, and then ultrasonically treated for 10~30min, the pyrrole solution is a pyrrole aqueous solution, and the concentration of pyrrole in the pyrrole solution is 0.05~0.2mol / L; in step (1), the fiber is a pretreated fiber, and the pretreated fiber is prepared by: soaking the fiber in a solvent for 1~3h, then washing and drying, and then subjecting the dried fiber to oxygen plasma treatment to obtain the pretreated fiber, the atmosphere of the oxygen plasma treatment is oxygen, the power is 60~80W, and the time is 5~15min; (2) Prepare a slurry by adsorbing pyrrole fiber solution, and then add an oxidant to the slurry to make pyrrole polymerize in situ on the fiber surface, so as to generate a composite conductive fiber with fiber as core layer and polypyrrole as skin layer in the slurry, and obtain a slurry containing composite conductive fiber to be formed; the oxidant is ferric chloride; the temperature of the in situ polymerization is 10~30℃, and the time of the in situ polymerization is 0.1~8h; (3) The slurry to be formed is wet-formed to obtain wet-process nonwoven composite filter material.

2. The preparation method according to claim 1, characterized in that: The solvent is an alcohol or ketone solvent with a boiling point not exceeding 100°C.

3. The preparation method according to claim 1, characterized in that: The solvent is one or more of methanol, ethanol, isopropanol, acetone, and butanone.

4. The preparation method according to claim 1, characterized in that: The chopped glass fibers have a length of 2-4 mm and a diameter of 5-7 μm, the glass fiber cotton has a length of 5-7 mm and a diameter of 2-4 μm, and the organic fibers have a length of 4-6 mm and a diameter of 12-14 μm.

5. The preparation method according to claim 1, characterized in that: The fiberglass wool is type 475 fiberglass wool, and the organic fiber is one or more of PET fiber, PAN fiber, PE fiber, and PP fiber.

6. The preparation method according to claim 1, characterized in that: The molar ratio of the oxidant in step (2) to the pyrrole solution in step (1) is (0.2~0.3):

1.

7. The preparation method according to claim 6, characterized in that: The molar ratio of the oxidant in step (2) to the pyrrole solution in step (1) is 0.238:

1.

8. The preparation method according to claim 1, characterized in that: The in-situ polymerization temperature is 15~20℃, and the in-situ polymerization time is 0.5~1h.

9. The preparation method according to claim 1, characterized in that: In step (2), the slurry contains 0.8 to 1.25‰ of fibers adsorbed with pyrrole.

10. The preparation method according to claim 9, characterized in that: In step (2), the slurry contains 1 to 1.25‰ of fibers adsorbed with pyrrole.

11. The preparation method according to claim 1, characterized in that: Before wet molding the slurry to be molded, the pH of the slurry to be molded is adjusted to 2.5~3.

0.

12. A wet nonwoven composite filter material prepared by any one of claims 1 to 11.

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