CN116808853A - Hydrophobic oleophobic PTFE membrane and preparation method and application thereof - Google Patents

Abstract

The invention provides a hydrophobic oleophobic PTFE film, a preparation method and application thereof, wherein the preparation method comprises the following steps: mixing: mixing and stirring polytetrafluoroethylene resin powder, aviation kerosene and a crosslinking agent, adding a silane waterproof oil repellent agent, continuously mixing and stirring, and carrying out ultrasonic treatment at 30Hz for 2 hours to obtain a mixture A; extrusion: extruding the mixed material A into a columnar mould material through an extruder; calendering: preparing a polytetrafluoroethylene membrane from the columnar mould material through a calender, and heating to remove aviation kerosene; biaxial stretching: simultaneously transversely stretching and longitudinally stretching the polytetrafluoroethylene membrane from which aviation kerosene is removed; and (5) heat setting: and (3) performing heat setting on the biaxially stretched PTFE film to obtain the hydrophobic oleophobic PTFE film.

Description

Hydrophobic and oleophobic PTFE membrane, preparation method and application

Technical field

The invention relates to the technical field of polymer materials, and in particular to a hydrophobic and oleophobic PTFE membrane and its preparation method and application.

Background technique

As the country's requirements for air pollutant control become increasingly stringent, in order to achieve ultra-low emissions, membrane-coated filter materials are increasingly used. PTFE membrane (polytetrafluoroethylene microporous membrane) is a microporous film produced by special processes such as premixing, extrusion, calendering, and biaxial stretching using polytetrafluoroethylene dispersion resin. It has unique node fibrillation, It has the characteristics of smooth surface, chemical resistance, breathable and impermeable, large air permeability, flame retardant, high temperature resistance, strong acid and alkali resistance, non-toxic, etc. The filter material coated with PTFE has high filtration efficiency, up to 99.99%, and has small pore size. , low relative density, high film strength, breathable and waterproof, chemical corrosion resistance, high biocompatibility, etc., and are widely used in biomedical materials, clothing, industrial filter materials and other fields;

The currently disclosed patented technical solution adopts the process of mixing - calendering - deoiling - transverse stretching of the film. The specific steps are: place the PTFE resin and lubricant in a high-temperature mixer to mix and mature to obtain a paste. material; the paste is extruded through the extruder equipment to obtain the primary material; the primary material is first longitudinally stretched at a temperature of 150-350°C to prepare a base film, and then stretched on a transverse stretching machine to a width of 1 -3m PTFE biaxially stretched microporous membrane; under the alkaline catalysis of NaOH, the PEFT membrane is infiltrated with an ethanol solution of polybutyl acrylate to hydrolyze the surface of the PEFT membrane; the surface of the PTFE microporous composite membrane is sprayed with fluororesin suspension emulsion And drying; sintering and shaping. However, because conventional waterproof and oil-repellent agents cannot form physical cross-linking on the surface of the PTFE membrane, the surface of the membrane-coated filter material cannot achieve high-level waterproofing and oil-repellent, and it comes into contact with low surface tension liquids (ammonium bisulfate, petroleum coke, heavy oil, etc.) When used, the liquid-proof sealing performance is poor. This type of low surface tension liquid will adhere to and block the PTFE microporous membrane, reduce its air permeability, and may cause serious damage to it. On the other hand, this type of liquid adheres to the surface of the membrane and agglomerates with dust. The dust then agglomerates with the liquid, eventually forming a sticky bag situation, causing the resistance of the filter bag to continue to rise and eventually fail. This limits the use of PTFE-coated filter media to a certain extent, hinders the realization of ultra-low emissions from such industrial boilers, and increases the company's costs and environmental risks.

Contents of the invention

The purpose of the present invention is to provide a hydrophobic and oleophobic PTFE membrane that has good resistance to low surface tension liquids, thereby ensuring long-term operation of the PTFE-coated filter material under high dust conditions.

Another object of the present invention is to provide a method for preparing a hydrophobic and oleophobic PTFE membrane, which has a simple process and is suitable for industrial production.

The third object of the present invention is to provide an application of a hydrophobic and oleophobic PTFE membrane. The PTFE filter membrane can be used in the field of air filtration. It has an obvious microporous structure and good hydrophobic and oleophobic properties, and is suitable for gas-solid separation of oil-containing gases. separation.

The present invention solves its technical problems by adopting the following technical solutions.

The invention proposes a preparation method of a hydrophobic and oleophobic PTFE membrane, which includes the following steps:

S1, mixing: After mixing polytetrafluoroethylene resin powder, aviation kerosene, and cross-linking agent, add silane waterproof and oil-repellent agent, continue mixing and stirring, and ultrasonic treatment at 30Hz for 2 hours to prepare mixture A;

S2, extrusion: Extrude the mixture A through the extruder into a columnar mold material;

S3, Calendering: After passing the cylindrical mold material through a calender to form a polytetrafluoroethylene diaphragm, it is heated to remove aviation kerosene;

S4, biaxial stretching: the polytetrafluoroethylene diaphragm after removing aviation kerosene is stretched transversely and longitudinally at the same time;

S5, heat setting: heat setting the biaxially stretched PTFE film to obtain a hydrophobic and oleophobic PTFE film.

The invention also proposes a hydrophobic and oleophobic PTFE membrane prepared by the above preparation method.

The invention also proposes an application of the hydrophobic and oleophobic PTFE membrane prepared by the above preparation method in filter materials, which includes the following steps:

(1) Prepare composite filter material;

(2) Hot-press the hydrophobic and oleophobic PTFE membrane on the surface of the composite filter material. The hot-pressing temperature is 250-330°C, the hot-pressing pressure is 0.5-0.8MPa, and the hot-pressing time is 4-6 s to obtain a hydrophobic and oleophobic membrane. PTFE coated composite filter material;

The hydrophobic and oleophobic PTFE membrane produced by the invention has good resistance to low surface tension liquids, thereby ensuring long-term operation of the PTFE-coated filter material under high dust conditions, and the resistance will not increase significantly.

The PTFE filter membrane prepared by the invention can be used in the field of air filtration. It has an obvious microporous structure, a porosity of more than 85%, a concentrated pore size distribution of 0.1-3 μm, very good stability, and good air permeability. The air permeability was tested under the condition of 127Pa. 60-80mm/s, has good hydrophobic and oleophobic properties, and is suitable for gas-solid separation of oil-containing gases.

Description of the drawings

In order to explain the technical solutions of the embodiments of the present invention more clearly, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a flow chart for the preparation of a hydrophobic and oleophobic PTFE membrane according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the examples, the conditions should be carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.

The following is a detailed description of a hydrophobic and oleophobic PTFE membrane according to the embodiment of the present invention, as well as its preparation method and application.

The embodiment of the present invention provides a method for preparing a hydrophobic and oleophobic PTFE membrane, which includes the following steps:

S1, mixing: After mixing polytetrafluoroethylene resin powder, aviation kerosene, and cross-linking agent, add silane waterproof and oil-repellent agent, continue mixing and stirring, and ultrasonic treatment at 30Hz for 2 hours to prepare mixture A;

S2, extrusion: Extrude the mixture A through the extruder into a columnar mold material;

S3, Calendering: After passing the cylindrical mold material through a calender to form a polytetrafluoroethylene diaphragm, it is heated to remove aviation kerosene;

S4, biaxial stretching: the polytetrafluoroethylene diaphragm after removing aviation kerosene is stretched transversely and longitudinally at the same time;

S5, heat setting: heat setting the biaxially stretched PTFE film to obtain a hydrophobic and oleophobic PTFE film.

Further, in a preferred embodiment of the present invention, in step S1, the preparation method of the silane-based waterproof and oil-repellent agent is: under nitrogen protection, add perfluorobutylethylene and triethoxysilane according to a molar ratio of 1:1.05-1.15 is added to the xylene solution, refluxed at 80-90°C for 20-24h under the catalysis of 0.5-1‰Pt, filtered, and distilled under reduced pressure at a vacuum of 0.07-0.08Mpa and a temperature of 110-130°C. Solvent to obtain silane-based waterproof and oil-repellent agent.

Further, in a preferred embodiment of the present invention, in step S2, the extrusion pressure is 5-8MPa, and the extrusion rate is 300-400mm/min.

Preferably, the cylindrical blank is put into the extrusion equipment, and the circular sliver is extruded at the copper die and stainless steel die of the extrusion equipment through the oil cylinder and the extrusion shaft of the extrusion equipment, and the cylindrical mold material is extruded. The diameter of the material is 18-25mm. The round sliver is fed between the upper and lower calendering rollers and is calendered into a tape with a width of 200-300mm and a thickness of 0.2-0.3mm. The extrusion compression ratio is 50- 120. During the entire process, the materials need to be kept in warm water at 80-90°C.

Further, in a preferred embodiment of the present invention, in step S3, the rolling temperature is 40-70°C, the rolling speed is 13-16m/min, the heating temperature is 300-340°C, and the polytetrafluoroethylene film The thickness of the sheet is 30-50μm.

Further, in a preferred embodiment of the present invention, in step S4, the transverse stretching ratio is 3-5 times, and the longitudinal stretching ratio is 5-8 times.

Further, in a preferred embodiment of the present invention, in step S5, the heat setting temperature is 300-340°C, and the heat setting time is 8-15 minutes.

Further, in a preferred embodiment of the present invention, in step S1, the cross-linking agent is one or both of polyisocyanate and polyvinyl butyral.

Further, in a preferred embodiment of the present invention, step S5 further includes: rolling up the heat-set PTFE film, and the thickness of the hydrophobic and oleophobic PTFE film is 5-8 μm.

The invention also provides a hydrophobic and oleophobic PTFE membrane prepared by the above preparation method.

The present invention also provides the application of the hydrophobic and oleophobic PTFE membrane prepared by the above preparation method in filter materials, which is characterized in that it includes the following steps:

(1) Prepare composite filter material;

(2) Hot-press the hydrophobic and oleophobic PTFE membrane on the surface of the composite filter material. The hot-pressing temperature is 250-330°C, the hot-pressing pressure is 0.5-0.8MPa, and the hot-pressing time is 4-6 s to obtain a hydrophobic and oleophobic membrane. PTFE coated composite filter material.

Preferably, the composite filter material includes a surface layer, a bottom layer and a base fabric layer. The surface layer is made of polyphenylene sulfide fiber and polytetrafluoroethylene fiber blended, and the bottom layer is made of polyphenylene sulfide fiber and polytetrafluoroethylene fiber. Fiber, the base fabric layer is a network structure formed by interweaving warp and weft of polytetrafluoroethylene yarn; the base fabric layer is located between the surface layer and the bottom layer, and the surface layer, base fabric layer and bottom layer are fixed by a needle punching machine. Then after calendering and singeing treatment, the composite filter material is obtained.

Preferably, the mass ratio of the polyphenylene sulfide fiber to the polytetrafluoroethylene fiber is 1-2:1.

The features and performance of the present invention will be described in further detail below with reference to examples.

Embodiment 1

Preparation method of hydrophobic and oleophobic PTFE membrane

(1) Preparation of waterproof and oil-repellent agent: Under nitrogen protection, add perfluorobutylethylene and triethoxysilane to the xylene solution at a molar ratio of 1:1.1, and reflux at 80°C for 22 hours under the catalysis of 0.5‰Pt. , filtered, with a vacuum degree of 0.07Mpa, and the solvent was distilled under reduced pressure at a temperature of 110°C to obtain perfluorobutyltriethoxysilane. The principle is a hydrosilylation reaction. An addition reaction occurs between Si-H-containing silicon compounds and unsaturated organic compounds to generate organosilicon compounds.

(2) Mixing: After mixing polytetrafluoroethylene resin powder, aviation kerosene, and polyisocyanate for 5 hours, add a waterproof and oil-repellent agent and continue mixing and stirring for 10 hours, and ultrasonic treatment at 30 Hz for 2 hours at an ultrasonic frequency of 50 Hz to prepare mixture A. The polytetrafluoroethylene resin is polytetrafluoroethylene particles that have been screened with a 300-mesh screen. The mass of polytetrafluoroethylene resin is 65% of the mass of mixture A, and the mass of aviation kerosene is 15% of the mass of mixture A. , the mass of polyisocyanate is 3% of the mass of Mixture A, and the mass of waterproof and oil-repellent agent is 17% of the mass of Mixture A.

(3) Extrusion: Extrude mixture A through an extruder into a columnar mold material, with an extrusion pressure of 6MPa and an output rate of 300mm/min.

(4) Calendering: Pass the cylindrical mold material through a calender to form a polytetrafluoroethylene diaphragm with a thickness of 40 μm. The rolling temperature of the calender is 60°C, and the calendering speed is 15m/min. After calendering and film formation, heating is continued to remove aviation kerosene. The heating temperature is 320°C.

(5) Biaxial stretching: The polytetrafluoroethylene diaphragm after removing aviation kerosene is stretched transversely and longitudinally at the same time. The transverse stretch ratio is 4 times, and the longitudinal stretch ratio is 6 times.

(6) Heat setting: Heat setting the biaxially stretched PTFE film to obtain a hydrophobic and oleophobic PTFE film. The heat setting temperature is 330°C and the heat setting time is 8 minutes.

(7) Winding to form a film: Wind up the heat-set PTFE film. The thickness of the hydrophobic and oleophobic PTFE film is 5-8 μm.

Preparation of hydrophobic and oleophobic PTFE-coated composite filter material:

(1) Preparation of composite filter material: The composite filter material includes a surface layer, a base fabric layer and a bottom layer laminated in sequence. The base fabric layer is fixed between the surface layer and the bottom layer through a needle punching machine, and then undergoes calendering and singeing treatment. The light temperature is 250°C, the hot pressing pressure is 0.35MPa, and the hot pressing time is 3 seconds. The needle punched felt is obtained, which is the composite filter material. The surface layer is made of a blend of polyphenylene sulfide fiber and polytetrafluoroethylene fiber, and the bottom layer is made of polyphenylene sulfide fiber and polytetrafluoroethylene fiber. The mass ratio of polyphenylene sulfide fiber to polytetrafluoroethylene fiber is 2:1. The fibers are opened, mixed, carded, and laid to obtain a uniform fiber network. The base fabric layer is a network structure formed by interweaving the warp and weft of polytetrafluoroethylene yarns. Among them, the preparation method of composite filter material can also adopt technology.

(2) Hot-press the hydrophobic and oleophobic PTFE membrane prepared in this example on the surface of the composite filter material. The hot-pressing temperature is 260°C, the hot-pressing pressure is 0.5MPa, and the hot-pressing time is 4 seconds to prepare hydrophobic and oleophobic PTFE. Coated composite filter material.

Embodiment 2

Preparation method of hydrophobic and oleophobic PTFE membrane

Preparation of waterproof and oil-repellent agent: Under nitrogen protection, add perfluorohexylethylene and triethoxysilane to the xylene solution at a molar ratio of 1:1.05, reflux at 80°C for 24 hours under the catalysis of 1‰Pt, filter, and vacuum The temperature is 0.075Mpa, and the solvent is distilled under reduced pressure at a temperature of 120°C to obtain perfluorohexyltriethoxysilane. The principle is a hydrosilylation reaction, in which Si-H-containing silicon compounds react with unsaturated organic compounds to form organosilicon compounds.

(2) Mixing: Mix polytetrafluoroethylene resin powder, aviation kerosene, and polyvinyl butyral for 8 hours, add a waterproof and oil-repellent agent, continue mixing and stirring for 12 hours, and ultrasonicate at 50Hz for 3 hours to prepare Mixture A. . The polytetrafluoroethylene resin is polytetrafluoroethylene particles that have been screened with a 300-mesh screen. The mass of polytetrafluoroethylene resin is 60% of the mass of mixture A, and the mass of aviation kerosene is 10% of the mass of mixture A. , the mass of polyvinyl butyral is 6% of the mass of Mixture A, and the mass of waterproof and oil-repellent agent is 23% of the mass of Mixture A. The waterproof and oil-repellent agent is the silane-based waterproof and oil-repellent agent prepared in step (1). Among them, the preparation method of composite filter material can also adopt technology.

(3) Extrusion: Extrude mixture A through an extruder into a columnar mold material, with an extrusion pressure of 6MPa and an output rate of 300mm/min.

(4) Calendering: Pass the cylindrical mold material through a calender to form a polytetrafluoroethylene diaphragm with a thickness of 40 μm. The rolling temperature of the calender is 60°C, and the calendering speed is 15m/min. After calendering and film formation, heating is continued to remove aviation kerosene. The heating temperature is 320°C.

(5) Biaxial stretching: The polytetrafluoroethylene diaphragm after removing aviation kerosene is stretched transversely and longitudinally at the same time. The transverse stretch ratio is 4 times, and the longitudinal stretch ratio is 6 times.

(6) Heat setting: Heat setting the biaxially stretched PTFE film to obtain a hydrophobic and oleophobic PTFE film. The heat setting temperature is 330°C and the heat setting time is 8 minutes.

(7) Winding to form a film: Wind up the heat-set PTFE film. The thickness of the hydrophobic and oleophobic PTFE film is 5-8 μm.

Preparation of hydrophobic and oleophobic PTFE-coated composite filter material:

(1) Preparation of composite filter material: The composite filter material includes a surface layer, a base fabric layer and a bottom layer laminated in sequence. The base fabric layer is fixed between the surface layer and the bottom layer through a needle punching machine, and then undergoes calendering and singeing treatment. The light temperature is 250°C, the hot pressing pressure is 0.35MPa, and the hot pressing time is 3 seconds. The needle punched felt is obtained, which is the composite filter material. The surface layer is made of a blend of polyphenylene sulfide fiber and polytetrafluoroethylene fiber, and the bottom layer is made of polyphenylene sulfide fiber and polytetrafluoroethylene fiber. The mass ratio of polyphenylene sulfide fiber to polytetrafluoroethylene fiber is 2:1. The fibers are opened, mixed, carded, and laid to obtain a uniform fiber network. The base fabric layer is a network structure formed by interweaving the warp and weft of polytetrafluoroethylene yarns. Among them, the preparation method of composite filter material can also adopt technology.

(2) Hot-press the hydrophobic and oleophobic PTFE membrane prepared in this example on the surface of the composite filter material. The hot-pressing temperature is 260°C, the hot-pressing pressure is 0.5MPa, and the hot-pressing time is 4 seconds to prepare hydrophobic and oleophobic PTFE. Coated composite filter material.

Embodiment 3

Preparation method of hydrophobic and oleophobic PTFE membrane

(1) Preparation of waterproof and oil-repellent agent: Under nitrogen protection, add perfluorooctylethylene and triethoxysilane to the xylene solution at a molar ratio of 1:1.15, and reflux at 90°C for 20 hours under the catalysis of 1‰Pt. , filtered, with a vacuum degree of 0.08Mpa, and the solvent was distilled under reduced pressure at a temperature of 130°C to obtain perfluorodecyltriethoxysilane. The principle is a hydrosilylation reaction, in which Si-H-containing silicon compounds react with unsaturated organic compounds to form organosilicon compounds.

(2) Mixing: After mixing polytetrafluoroethylene resin powder, aviation kerosene, and cross-linking agent for 3 hours, add a waterproof and oil-repellent agent and continue mixing and stirring for 12 hours, and ultrasonic treatment for 3 hours at an ultrasonic frequency of 40 Hz to prepare Mixture A. The polytetrafluoroethylene resin is polytetrafluoroethylene particles that have been screened through a 300-mesh screen. The cross-linking agent includes polyisocyanate and polyvinyl butyral. The mass ratio of polyisocyanate and polyvinyl butyral is 1 :1. The mass of polytetrafluoroethylene resin is 69% of the mass of mixture A, the mass of aviation kerosene is 10% of the mass of mixture A, the mass of cross-linking agent is 3% of the mass of mixture A, and the mass of waterproof and oil-repellent agent is 18% of the mass of Mixture A. The waterproof and oil-repellent agent is the silane-based waterproof and oil-repellent agent prepared in step (1). Among them, the preparation method of composite filter material can also adopt technology.

(3) Extrusion: Extrude mixture A through an extruder into a columnar mold material, with an extrusion pressure of 6MPa and an output rate of 300mm/min.

(4) Calendering: Pass the cylindrical mold material through a calender to form a polytetrafluoroethylene diaphragm with a thickness of 40 μm. The rolling temperature of the calender is 60°C, and the calendering speed is 15m/min. After calendering and film formation, heating is continued to remove aviation kerosene. The heating temperature is 320°C.

(5) Biaxial stretching: The polytetrafluoroethylene diaphragm after removing aviation kerosene is stretched transversely and longitudinally at the same time. The transverse stretch ratio is 4 times, and the longitudinal stretch ratio is 6 times.

(6) Heat setting: Heat setting the biaxially stretched PTFE film to obtain a hydrophobic and oleophobic PTFE film. The heat setting temperature is 330°C and the heat setting time is 8 minutes.

(7) Winding to form a film: Wind up the heat-set PTFE film. The thickness of the hydrophobic and oleophobic PTFE film is 5-8 μm.

Preparation of hydrophobic and oleophobic PTFE-coated composite filter material:

(1) Preparation of composite filter material: The composite filter material includes a surface layer, a base fabric layer and a bottom layer laminated in sequence. The base fabric layer is fixed between the surface layer and the bottom layer through a needle punching machine, and then undergoes calendering and singeing treatment. The light temperature is 250°C, the hot pressing pressure is 0.35MPa, and the hot pressing time is 3 seconds. The needle punched felt is obtained, which is the composite filter material. The surface layer is made of a blend of polyphenylene sulfide fiber and polytetrafluoroethylene fiber, and the bottom layer is made of polyphenylene sulfide fiber and polytetrafluoroethylene fiber. The mass ratio of polyphenylene sulfide fiber to polytetrafluoroethylene fiber is 2:1. The fibers are opened, mixed, carded, and laid to obtain a uniform fiber network. The base fabric layer is a network structure formed by interweaving the warp and weft of polytetrafluoroethylene yarns. Among them, the preparation method of composite filter material can also adopt technology.

(2) Hot-press the hydrophobic and oleophobic PTFE membrane prepared in this example on the surface of the composite filter material. The hot-pressing temperature is 260°C, the hot-pressing pressure is 0.5MPa, and the hot-pressing time is 4 seconds to prepare hydrophobic and oleophobic PTFE. Coated composite filter material.

Embodiment 4

Preparation method of hydrophobic and oleophobic PTFE membrane

(1) Preparation of waterproof and oil-repellent agent: Under nitrogen protection, add perfluorooctylethylene and triethoxysilane to the xylene solution at a molar ratio of 1:1.15, and reflux at 90°C for 20 hours under the catalysis of 1‰Pt. , filtered, with a vacuum degree of 0.08Mpa, and the solvent was distilled under reduced pressure at a temperature of 130°C to obtain perfluorodecyltriethoxysilane. The principle is a hydrosilylation reaction, in which Si-H-containing silicon compounds react with unsaturated organic compounds to form organosilicon compounds.

(2) Mixing: After mixing polytetrafluoroethylene resin powder, aviation kerosene, and cross-linking agent for 3 hours, add a waterproof and oil-repellent agent and continue mixing and stirring for 12 hours, and ultrasonic treatment at 60 Hz for 3 hours at an ultrasonic frequency of 60 Hz to prepare the mixture. A. The polytetrafluoroethylene resin is polytetrafluoroethylene particles that have been screened through a 300-mesh screen. The cross-linking agent includes polyisocyanate and polyvinyl butyral. The mass ratio of polyisocyanate and polyvinyl butyral is 1 :1. The mass of polytetrafluoroethylene resin is 69% of the mass of mixture A, the mass of aviation kerosene is 10% of the mass of mixture A, the mass of cross-linking agent is 3% of the mass of mixture A, and the mass of waterproof and oil-repellent agent is 18% of the mass of Mixture A. The waterproof and oil-repellent agent is the silane-based waterproof and oil-repellent agent prepared in step (1).

(2) Extrusion: Extrude mixture A through an extruder into a columnar mold material, with an extrusion pressure of 8MPa and an output rate of 400mm/min.

(3) Calendering: Pass the cylindrical mold material through a calender to form a polytetrafluoroethylene diaphragm with a thickness of 50 μm. The rolling temperature of the calender is 70°C, and the calendering speed is 16m/min. After calendering and film formation, heating is continued to remove aviation kerosene. The heating temperature is 340°C.

(4) Biaxial stretching: The polytetrafluoroethylene diaphragm after removing aviation kerosene is stretched transversely and longitudinally at the same time. The transverse stretch ratio is 5 times, and the longitudinal stretch ratio is 8 times.

(5) Heat setting: Heat setting the biaxially stretched PTFE film to obtain a hydrophobic and oleophobic PTFE film. The heat setting temperature is 340°C and the heat setting time is 15 minutes.

(6) Rolling to form a film: Roll up the heat-set PTFE film. The thickness of the hydrophobic and oleophobic PTFE film is 5-8 μm.

Preparation of hydrophobic and oleophobic PTFE-coated composite filter material:

(1) Preparation of composite filter material: The composite filter material includes a surface layer, a base fabric layer and a bottom layer laminated in sequence. The base fabric layer is fixed between the surface layer and the bottom layer through a needle punching machine, and then undergoes calendering and singeing treatment. The light temperature is 250°C, the hot pressing pressure is 0.35MPa, and the hot pressing time is 3 seconds. The needle punched felt is obtained, which is the composite filter material. The surface layer is made of a blend of polyphenylene sulfide fiber and polytetrafluoroethylene fiber, and the bottom layer is made of polyphenylene sulfide fiber and polytetrafluoroethylene fiber. The mass ratio of polyphenylene sulfide fiber to polytetrafluoroethylene fiber is 2:1. The fibers are opened, mixed, carded, and laid to obtain a uniform fiber network. The base fabric layer is a network structure formed by interweaving the warp and weft of polytetrafluoroethylene yarns.

(2) Hot-press the hydrophobic and oleophobic PTFE membrane prepared in this example on the surface of the composite filter material. The hot-pressing temperature is 330°C, the hot-pressing pressure is 0.8MPa, and the hot-pressing time is 6 seconds to prepare hydrophobic and oleophobic PTFE. Coated composite filter material.

Comparative ratio

Preparation method of hydrophobic and oleophobic PTFE membrane

(1) Mixing: After mixing polytetrafluoroethylene resin powder, aviation kerosene, and polyisocyanate for 5 hours, add deionized water and continue mixing and stirring for 10 hours, and ultrasonic treatment for 2 hours at an ultrasonic frequency of 50 Hz to prepare Mixture A. The polytetrafluoroethylene resin is polytetrafluoroethylene particles that have been screened with a 300-mesh screen. The mass of polytetrafluoroethylene resin is 69% of the mass of mixture A, and the mass of aviation kerosene is 10% of the mass of mixture A. , the mass of polyisocyanate is 3% of the mass of Mixture A, and the deionized water is 18% of the mass of Mixture A.

(2) Extrusion: Extrude mixture A through an extruder into a columnar mold material, with an extrusion pressure of 6MPa and an output rate of 300mm/min.

(3) Calendering: Pass the cylindrical mold material through a calender to form a polytetrafluoroethylene diaphragm with a thickness of 40 μm. The rolling temperature of the calender is 60°C, and the calendering speed is 15m/min. After calendering and film formation, heating is continued to remove aviation kerosene. The heating temperature is 320°C.

(4) Biaxial stretching: The polytetrafluoroethylene diaphragm after removing aviation kerosene is stretched transversely and longitudinally at the same time. The transverse stretch ratio is 4 times, and the longitudinal stretch ratio is 6 times.

(5) Heat setting: Heat setting the biaxially stretched PTFE film to obtain a hydrophobic and oleophobic PTFE film. The heat setting temperature is 330°C and the heat setting time is 8 minutes.

(6) Rolling to form a film: Roll up the heat-set PTFE film. The thickness of the hydrophobic and oleophobic PTFE film is 5-8 μm.

Preparation of hydrophobic and oleophobic PTFE-coated composite filter material:

(1) Preparation of composite filter material: The composite filter material includes a surface layer, a base fabric layer and a bottom layer laminated in sequence. The base fabric layer is fixed between the surface layer and the bottom layer through a needle punching machine, and then undergoes calendering and singeing treatment. The light temperature is 250°C, the hot pressing pressure is 0.35MPa, and the hot pressing time is 3 seconds. The needle punched felt is obtained, which is the composite filter material. The surface layer is made of a blend of polyphenylene sulfide fiber and polytetrafluoroethylene fiber, and the bottom layer is made of polyphenylene sulfide fiber and polytetrafluoroethylene fiber. The mass ratio of polyphenylene sulfide fiber to polytetrafluoroethylene fiber is 2:1. The fibers are opened, mixed, carded, and laid to obtain a uniform fiber network. The base fabric layer is a network structure formed by interweaving the warp and weft of polytetrafluoroethylene yarns.

(2) Hot-press the hydrophobic and oleophobic PTFE membrane prepared in this example on the surface of the composite filter material. The hot-pressing temperature is 260°C, the hot-pressing pressure is 0.5MPa, and the hot-pressing time is 4 s to prepare the PTFE composite filter material. .

The properties of the composite filter materials prepared in Examples 1 to 3 and Comparative Examples were measured.

Table 1 Test results

Measured using the standards "GBT4745-2012 Testing and Evaluation of Textile Waterproof Properties by Water Wet Method" and "GB/T19977-2014 Textile Oil Repellency and Hydrocarbon Resistance Test"

Example 1 Level 3 Level 3 Level 3 Example 2 Level 5 Level 5 Level 5 Example 3 Level 3 Level 3 Level 3 Example 4 Level 3 Level 3 Level 3 Comparative ratio level 2 level 2 level 2

Table 2 is the waterproof performance evaluation table of the composite filter materials prepared in Examples 1 to 3 and Comparative Examples.

It can be seen from Table 2 that the water-wetting grade of the composite filter material prepared in Example 1 is level 3, the water-wetting level of the composite filter material prepared in Example 2 is level 5, and the composite filter material prepared in Example 3 Its water-wetting grade is level 3, and the water-wetting grade of the composite filter material prepared in the comparative example is level 2. When the proportion of waterproof and oil-repellent agent is increased, the anti-wetting performance of the composite filter material is enhanced.

Table 3 is the oil repellent performance evaluation table of the composite filter materials prepared in Examples 1 to 3 and Comparative Examples.

It can be seen from Table 3 that the oil repellency level of the composite filter material prepared in Example 1 is level 3, the oil repellency level of the composite filter material prepared in Example 2 is level 6, and the oil repellency level of the composite filter material prepared in Example 3 is level 6. The oil repellency level is level 3, and the oil repellency level of the composite filter material prepared in the comparative example is level 2. When the content of waterproof and oil-repellent agent increases, the oil-repellent grade of the composite filter material increases.

The following description of the above technical solution is as follows:

The hydrophobic and oleophobic PTFE membrane produced by the invention has good resistance to low surface tension liquids, thereby ensuring long-term operation of the PTFE-coated filter material under high dust conditions, and the resistance will not increase significantly.

When the polytetrafluoroethylene resin content is lower than this 60%, the strength of the finished PTFE membrane will be reduced, affecting its film-forming properties and service life. During the test, the actual film-forming rate was lower than 40%. When the vinyl resin content is higher than this 69%, it will reduce the waterproof and oil-repellent level and the breathability of the finished PTFE membrane. During the test, the actual waterproofing was less than level 3, the oil resistance was less than level 3, and the air permeability was lower than 60mm/s (127Pa test conditions ), when the content of waterproof and oil-repellent agent is less than 15%, the waterproof and oil-repellent performance of the finished PTFE membrane will be reduced. During the test, the actual measured waterproofness was less than level 3, the oil resistance was less than level 2, and the air permeability was less than 50mm/s (127Pa test Conditions), when the content of waterproof and oil-repellent agent is higher than 25%, the strength of the finished PTFE membrane will be reduced, and the actual film formation rate measured during the test was lower than 55%.

The PTFE filter membrane prepared by the invention can be used in the field of air filtration. It has obvious microporous structure, very good stability, good air permeability, good hydrophobic and oleophobic properties, and is suitable for gas-solid separation of oil-containing gases.

The composite filter material includes a surface layer, a bottom layer and a base fabric layer. The surface layer is made of polyphenylene sulfide fiber and polytetrafluoroethylene fiber blended, and the bottom layer is made of polyphenylene sulfide fiber and polytetrafluoroethylene fiber. The base fabric layer is a network structure formed by interlacing warp and weft of polytetrafluoroethylene yarns. The base fabric layer is located between the surface layer and the bottom layer. The surface layer, the base fabric layer and the bottom layer are fixed by acupuncture machinery, and then undergo a calendering and singeing treatment to obtain a composite filter material.

To sum up, the composite filter material prepared in Example 1 has a water-soaking grade of level 3, the composite filter material prepared in Example 2 has a water-wetting grade of level 5, and the composite filter material prepared in Example 3 has a water-soaking grade of The water level is level 3, and the water-wetting level of the composite filter material prepared in the comparative example is level 2. When the proportion of waterproof and oil-repellent agent is increased, the anti-wetting performance of the composite filter material is enhanced. The oil-repellent grade of the composite filter material prepared in Example 1 is level 3, and the oil-repellent grade of the composite filter material prepared in Example 2 is The oil repellency level of the composite filter material prepared in Example 3 is level 3, and the oil repellency level of the composite filter material prepared in the comparative example is level 2. When the content of waterproof and oil-repellent agent increases, the oil-repellent grade of the composite filter material increases.

The above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solution to deviate from the spirit and scope of the technical solution of each embodiment of the present invention.

Claims (10)

1. A method for preparing a hydrophobic and oleophobic PTFE membrane, which is characterized in that it includes the following steps: S1, mixing: After mixing polytetrafluoroethylene resin powder, aviation kerosene, and cross-linking agent, add silane waterproof and oil-repellent agent, continue mixing and stirring, and ultrasonic treatment at 30Hz for 2 hours to prepare mixture A; S2, extrusion: Extrude the mixture A through the extruder into a columnar mold material; S3, Calendering: After passing the cylindrical mold material through a calender to form a polytetrafluoroethylene diaphragm, it is heated to remove aviation kerosene; S4, biaxial stretching: the polytetrafluoroethylene diaphragm after removing aviation kerosene is stretched transversely and longitudinally at the same time; S5, heat setting: heat setting the biaxially stretched PTFE film to obtain a hydrophobic and oleophobic PTFE film. 2. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that: in step S1, the preparation method of the silane waterproof and oil repellent agent is: under nitrogen protection, perfluorobutylethylene and triethoxysilane are added to the xylene solution at a molar ratio of 1:1.05-1.15, refluxed at 80-90°C for 20-24h under the catalysis of 0.5-1‰Pt, filtered, and placed in a vacuum of 0.07-0.08Mpa and a temperature of The solvent is removed by distillation under reduced pressure at 110-130°C to obtain a silane-based waterproof and oil-repellent agent. 3. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that in step S2, the extrusion pressure is 5-8MPa, and the extrusion rate is 300-400mm/min. 4. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that: in step S3, the rolling temperature is 40-70°C, the rolling speed is 13-16m/min, and the heating temperature is 300-300°C. 340°C, the thickness of the polytetrafluoroethylene membrane is 30-50 μm. 5. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 4, characterized in that in step S4, the transverse stretching ratio is 3-5 times and the longitudinal stretching ratio is 5-8 times. 6. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that: in step S5, the heat setting temperature is 300-340°C, and the heat setting time is 8-15 minutes. 7. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that: in step S1, the cross-linking agent is one or both of polyisocyanate and polyvinyl butyral. 8. The preparation method of the hydrophobic and oleophobic PTFE membrane according to claim 1, characterized in that: step S5 further includes: winding up the heat-set PTFE film, and the thickness of the hydrophobic and oleophobic PTFE membrane is 5 -8μm. 9. A hydrophobic and oleophobic PTFE membrane prepared by the preparation method according to any one of claims 1 to 8. 10. The application of a hydrophobic and oleophobic PTFE membrane prepared by the preparation method according to any one of claims 1 to 8 in filter materials, characterized in that it includes the following steps: (1) Prepare composite filter material; (2) Hot-press the hydrophobic and oleophobic PTFE membrane on the surface of the composite filter material. The hot-pressing temperature is 250-330°C, the hot-pressing pressure is 0.5-0.8MPa, and the hot-pressing time is 4-6 s to obtain a hydrophobic and oleophobic membrane. PTFE coated composite filter material.