WO2017080470A1 - Polytetrafluoroethylene fiber tubular membranes - Google Patents

Abstract

A polytetrafluoroethylene fiber tubular membrane comprises: a polytetrafluoroethylene material body, wherein the polytetrafluoroethylene is in fibrous shape with the fiber diameter of greater than 200 nm and less than or equal to 2000 nm; the body has cavities with diameters of 10 to 2000 nm and cavity walls formed in a three-dimensional manner surrounding the cavities; and the cavities are uniformly distributed, with each of the cavities being penetrated through in a three-dimensional manner, wherein the cavities being uniformly distributed means that each of the cavities is uniformly distributed at any unit level volume of porous material; wherein porosity is greater than or equal to 75%, transmittance greater than or equal to 50%, tensile strength greater than or equal to 28N / mm ², and water pressure resistance greater than or equal to 4kg / cm ².

Description

Polytetrafluoroethylene fiber tubular membrane Technical field

The present invention relates to a porous material, in particular to a polytetrafluoroethylene fiber tubular membrane.

Background technique

A solid containing a certain number of pores is called a porous material and is a material that forms a network structure by through or closed pores. Compared with continuous medium materials, porous materials generally have the advantages of low relative density, high specific strength, high specific surface area, light weight, sound insulation, heat insulation and good permeability. Depending on the size of the pores, the porous material can be divided into microporous (pore size less than 2 nm) material, mesoporous (pore size 2-50 nm) material and macroporous (pore size greater than 50 nm) material.

Porous materials are classified according to their materials and can be classified into metal porous materials and non-metallic porous materials. Non-metallic porous materials generally have the characteristics of large specific surface area, small density, small thermal conductivity, small relative density, and high porosity. They are used in catalysts (including carriers), adsorbents, heat preservation, heat insulation, sewage and waste gas treatment, filtration of liquids, and Gas (even bacteria), lightweight building materials, environmental protection, soil improvement, chemical industry and other fields have broad application prospects. Among them, the polytetrafluoroethylene porous membrane material has a wide application range due to its temperature stability, chemical stability, electrical insulation, flame retardancy and self-lubricating properties. However, due to the randomness and irregularity of the pore structure, it still cannot satisfy many application properties.

In many applications, the porous material itself needs to be uniform, its pore size and pore distribution are uniform, so that the performance is uniform, but in fact, many porous materials do not meet this requirement, and their uniformity complements; although some materials claim to be self-proclaimed Achieve higher uniformity, but its uniformity is still uniformity on a large volume scale. If it is measured by a small volume scale, for example, if a plurality of three-dimensional bodies having a volume of not more than one cubic centimeter are taken on the material, respectively, The quality, the degree of uniformity is still very large, thus causing various properties of the polytetrafluoroethylene porous membrane material such as strength, elastic modulus, flux and the like, which seriously affect its function.

Summary of the invention

The object of the present invention is to provide a polytetrafluoroethylene fiber tubular membrane which is structurally suitable, controllable and highly uniform.

The object of the invention is achieved by the following measures:

A polytetrafluoroethylene fiber tubular membrane comprising a body of polytetrafluoroethylene material, a polytetrafluoroethylene fiber, 200 nm < fiber diameter ≤ 2000 nm, a body having a pore diameter of 10 nm to 2000 nm, and a three-dimensional space surrounding the hole The cavity wall formed by the cavity has a uniform distribution of pores, and each cavity is three-dimensionally penetrated. The uniform distribution of the cavity means that each cavity is uniformly distributed under arbitrary unit volume on the porous material; the porosity is 75%. The light transmittance is 50% or more, the tensile strength is 28 N/mm ² or more, and the water pressure resistance is 4 kg/cm ² or more.

Specifically, the above polytetrafluoroethylene fiber tubular membrane has a pore diameter of 200 to 2000 nm and is three-dimensionally empty. A cavity wall formed around the cavity, a lower cavity of 10 to 150 nm is disposed on the cavity wall, and each of the holes is three-dimensionally penetrated and each of the holes is also connected to each other; the cavity is uniformly distributed, the cavity Uniform distribution means that the pores are uniformly distributed at any unit volume on the porous material.

Specifically, the above unit-level volume means a cubic centimeter-level or cubic millimeter-level or smaller unit-level volume.

More specifically, the uniform distribution of the above-mentioned cavities means that each of the three-dimensional bodies having a volume of not more than one cubic centimeter and the same size on the porous material is substantially equivalent in mass.

More specifically, the above-mentioned mass is substantially equivalent to a plurality of three-dimensional bodies having a volume of not more than one cubic centimeter and the same size, which are respectively referred to as a mass, and an average value of their masses is obtained, and any three-dimensional mass is relatively The absolute value of the deviation from the mass average is not more than 4% of the average of the three-dimensional body mass.

Further, the three-dimensional bodies of the same size having a volume of not more than one cubic millimeter on the multi-stage material are substantially equivalent in mass.

More specifically, the mass is substantially equivalent to a plurality of three-dimensional bodies of the same size having a volume of not more than one cubic millimeter on the porous material, respectively referred to as masses, and an average value of their masses is obtained, and any three-dimensional mass is obtained. The absolute value of the deviation from the mass average is not more than 4% of the average of the three-dimensional body mass.

Preferably, the polytetrafluoroethylene fiber tubular membrane is composed of a multi-stage porous material, the body is a cavity which is classified by a material pore size, and a cavity wall which surrounds the cavity in a three-dimensional space, and a lower cavity is arranged on the cavity wall. The cavities of each stage are each three-dimensionally penetrated and the cavities of the respective stages are also mutually connected. More specifically, the next level of porous material constitutes the wall of the cavity of the upper stage. The cavity wall of the upper cavity is composed of a multi-stage porous material of its lower stage or a composite of porous materials of the lower stage, so that the material can meet specific functional requirements.

Specifically, each stage of the porous material of the material body is self-contained as a continuous structure. The maximum outer boundary of each level of porous material is comparable to the entire material body space boundary. That is, each grade of porous material can exist in the bulk as a first-order independent porous material, and has its own physical and chemical properties. Such a structure can make the physical and chemical properties of the porous materials of different levels different, and have different physical and chemical properties in the entire space of the relatively fixed materials, and better meet various functional requirements.

Beneficial effect

1. The present invention provides a polytetrafluoroethylene fiber tubular membrane having a porous structure, and the structural form thereof is clarified, and the hierarchical structure of the pore cavity and the uniform structure thereof can satisfy various functional requirements.

2. The present invention provides a specific and clear measurement method for the uniform distribution of the pores of the polytetrafluoroethylene fiber tubular membrane, and it is clarified that the pores of the porous material and the multi-stage structure are uniformly distributed on the scale of the small unit volume. Sexually, such a porous structure is highly uniform, thereby ensuring uniformity of the properties of the porous material.

3. The polytetrafluoroethylene fiber tubular membrane of the present invention is three-dimensionally penetrated, including three-dimensional communication of each level of holes, and holes of each level It is three-dimensionally connected to each other and has good penetration, which can fully meet the functional requirements of materials.

4. The polytetrafluoroethylene fiber tubular film of the present invention is a hydrophobic surface having a multistage roughness structure. The surface water contact angle can reach 165° or more.

5. Polytetrafluoroethylene film has diffuse reflection phenomenon, polytetrafluoroethylene porous fiber membrane, such as pore distribution, hierarchical structure, porosity, pore shape and other structural characteristics, processes, etc. and transmittance, mechanical strength, water pressure resistance and other films Related to performance, the PTFE tubular film of the invention has bright and bright film, bright and smooth luster, no support, stable shape and controllable thickness, and is applied to the membrane distillation process with a flux of >38 L/m ² ·h. The rejection is 99.8% or more, the tensile strength is 32 N/mm ² or more, and the water pressure resistance is 8 kg/cm ² or more.

detailed description

BEST MODE FOR CARRYING OUT THE INVENTION A detailed embodiment is given on the premise of the technical solution of the present invention, but the scope of protection of the present invention is not limited to the following embodiments. It is obvious that various alternatives or modifications can be made without departing from the spirit and scope of the inventions of the present invention. .

Example 1

The polytetrafluoroethylene fiber tubular membrane of the invention has a secondary pore structure, wherein the cavity wall of the first-stage cavity uniformly distributed and interpenetrating has a second-stage cavity uniformly distributed and mutually penetrated, and two The stepped holes also penetrate each other, and the through holes are three-dimensionally penetrated. Each level of porous material of the material body is self-contained as a continuous structure. The total effective porosity is 75%, the fiber diameter is 500 nm ± 20 nm, the macroporous average pore diameter is 1000 nm, and there are through-holes having an average pore diameter of 50 nm on the cavity wall of the macropores.

9 pieces of 10 mm × 10 mm × 10 mm three-dimensional bodies of the same size were placed on the porous material by mechanical processing, and the mass was tested with a METTLER TOLEDO XP26 Microbalance balance. The results are shown in Table 1, wherein the reading and averaging were performed. The absolute value of the deviation of the value is expressed as a percentage, and the value is the absolute value of the deviation from the average value divided by the mass average value. As can be seen from Table 1, the mass deviation is not more than 4%.

Light transmittance measurement: The LCD5200 photoelectric characteristic tester was used to scan the 380-780 nm band according to the distribution characteristics of the solar light bands published by GBT2680-1994, and calculate the light transmittance of the sample to visible light.

Table 1

Part Number	Quality (mg)	Absolute value (%) relative to the mean
1	702.041	0.6%
2	718.803	1.8%
3	694.760	1.6%
4	713.819	1.1%
5	692.565	1.9%
6	702.937	0.4%

7	709.609	0.5%
8	702.409	0.5%
9	717.962	1.7%
Mass average	706.101

The preparation method of the polytetrafluoroethylene porous material is:

(1) a polytetrafluoroethylene emulsion having a solid content of 60%, a chitosan having a particle size of 50 nm, a gelatin solution of 9% (mass ratio), and a starch emulsion of 18 wt%, uniformly mixed, in a mass ratio of 55:30:9:5, Formulated into a spinning solution;

(2) preparing a polytetrafluoroethylene precursor film by electrospinning in an oriented electrospinning fiber device under vacuum conditions, and treating at 110 ° C for 20 min under vacuum;

(3) The precursor film is wound up to 5 layers to a cylinder support mold of 4-25 mm in diameter, and sent to a tube furnace for sintering in a vacuum or a protective atmosphere. The sintering is sequentially sintered by program temperature control at 8 ° C / min. The temperature is raised from room temperature to 170 ° C, incubated at 170 ° C for 50 min; at a rate of 8 ° C / min to 280 ° C, 280 ° C for 60 min; at a rate of 2 ° C / min to 360 ° C, incubated at 360 ° C for 15 min; The temperature was raised to 400 ° C at a rate of 8 ° C / min, and incubated at 400 ° C for 80 min.

(4) After the sintering, the program was temperature-controlled and cooled, and a porous polytetrafluoroethylene fiber tubular film having a two-stage pore structure was obtained according to a conventional technique, and the thickness was 176 μm, and the film diameter was 4-25 mm.

The PTFE fiber tubular membrane does not need support, has stable shape and controllable thickness, and can be used for gas-liquid separation and liquid-liquid separation to achieve precise grading filtration, for example, it is suitable for filtration of two-component or multi-component gas (liquid) body. The flux is large, the rejection rate is high, and it is not easy to be polluted (such as multi-liquid immersion membrane pollution), and has the advantages of high efficiency and long-term efficiency. The film water contact angle was 169°, the light transmittance was 58%, the tensile strength was 30 N/mm ² or more, and the water pressure resistance was 5 kg/cm ² or more.

For example, in membrane distillation applied to acid/alcohol-water-non-volatile solute system, the total flux can reach above 38kg/m ² ·h, and the non-volatile solute rejection in the system is above 99.8%. Volatile alcohol/acid separation factor = [alcohol / acid mass fraction in distillate × (1 - raw material liquid alcohol / acid mass fraction)] ÷ [raw material liquid alcohol / acid mass fraction × (1- distillate alcohol / acid mass fraction)] can reach 10 the above.

Example 2

The polytetrafluoroethylene fiber tubular membrane of the present invention has a three-stage pore structure, wherein the cavity wall of the first-stage cavity uniformly distributed and interpenetrating has a second-stage cavity uniformly distributed and mutually penetrating, and two The stepped holes also penetrate each other, and the through holes are three-dimensionally penetrated. Each level of porous material of the material body is self-contained as a continuous structure. The total effective porosity is 80%, the fiber diameter is 700±20 nm, the macroporous average pore diameter is 1500 nm, and there are average secondary pores of 100 nm in the cavity wall of the macropores, and there is an average on the pore walls of the second-order pores. A third-stage hole having a pore diameter of 10 nm.

9 pieces of 10 mm × 10 mm × 10 mm three-dimensional bodies of the same size were placed on the porous material by mechanical processing, and the mass was tested with a METTLER TOLEDO XP26 Microbalance balance. The results are shown in Table 1, wherein The absolute value of the deviation of the average value is expressed as a percentage, and the value is the absolute value of the deviation from the average value divided by the mass average value. As can be seen from Table 2, the mass deviation is not more than 4%.

Table 2

Part Number	Quality (mg)	Absolute value (%) relative to the mean
1	557.800	2.3%
2	548.313	0.5%
3	541.019	0.8%
4	539.175	1.1%
5	543.269	0.4%
6	547.043	0.3%
7	542.618	0.5%
8	540.604	0.9%
9	549.056	0.7%
Mass average	545.433

The preparation method of the polytetrafluoroethylene porous material is:

(1) mixing PTFE fine powder, polyethylene glycol having a molecular weight of 1000, stirring and heating to 380 ° C, stirring for 60 min, rapidly cooling to room temperature for crushing, and pulverizing at minus Celsius to obtain polytetrafluoroethylene particles;

(2) Dispersing a polytetrafluoroethylene particle having a particle diameter of 200 nm into a 60% solid content emulsion, and uniformly mixing it with a particle size of 100 nm chitosan, a 9% (mass ratio) chitosan solution, and a 15 wt% starch emulsion. According to the mass ratio of 55:30:9:5, it is formulated into a spinning solution;

(3) preparing a polytetrafluoroethylene precursor film by electrospinning in an oriented electrospinning fiber device under vacuum conditions, and treating at 110 ° C for 20 min under vacuum;

(4) The precursor film is wound into 5 layers to a cylinder supporting mold of 4-25 mm in diameter, and sent to a tube furnace for sintering in a vacuum or a protective atmosphere. The sintering is sequentially sintered by a program controlled temperature section at 8 ° C / min. The temperature is raised from room temperature to 180 ° C, incubated at 180 ° C for 60 min; at a rate of 8 ° C / min to 300 ° C, at 300 ° C for 60 min; at a rate of 2 ° C / min to 360 ° C, at 360 ° C for 20 min; The temperature was raised to 400 ° C at a rate of 8 ° C / min, and incubated at 400 ° C for 80 min.

(5) After the sintering, the program is temperature-controlled and cooled, and the porous polytetrafluoroethylene fiber tubular film having a three-stage pore structure is obtained according to a conventional technique, and has a thickness of 180 μm and a fiber tubular membrane diameter of 4-25 mm.

The PTFE fiber tubular membrane does not need support, has stable shape and controllable thickness, and can be used for gas-liquid separation and liquid-liquid separation to achieve precise grading filtration, for example, it is suitable for filtration of two-component or multi-component gas (liquid) body. The flux is large, the rejection rate is high, and it is not easy to be polluted (such as multi-liquid immersion membrane pollution), and has the advantages of high efficiency and long-term efficiency. The film water contact angle was 173°, the light transmittance was 60%, the tensile strength was 28 N/mm ² or more, and the water pressure resistance was 6 kg/cm ² or more.

For example, in membrane distillation for multi-component (or mixed) alcohol/acid-water-non-volatile solute systems, the total flux can reach above 40 kg/m ² ·h, and the non-volatile solute rejection in the system is above 99.9%. Alcohol/acid separation factor = [alcohol/acid mass fraction in distillate × (1 - stock liquid alcohol / acid mass fraction)] ÷ [feed liquid alcohol / acid mass fraction × (1-distillate alcohol / acid mass fraction )] can reach more than 10.

Claims (11)

1. A polytetrafluoroethylene fiber tubular membrane comprising a body of polytetrafluoroethylene material, a polytetrafluoroethylene fiber, 200 nm < fiber diameter ≤ 2000 nm, a body having a pore diameter of 10 nm to 2000 nm, and a three-dimensional space surrounding the hole The cavity wall formed by the cavity has a uniform distribution of pores, and each cavity is three-dimensionally penetrated. The uniform distribution of the cavity means that each cavity has a uniform distribution under arbitrary unit volume on the porous material; porosity ≥75 %, the light transmittance is 50% or more, the tensile strength is 28 N/mm ² or more, and the water pressure resistance is 4 kg/cm ² or more.
2. The polytetrafluoroethylene fiber tubular membrane according to claim 1, comprising a cavity having a pore diameter of 200 to 2000 nm and a cavity wall formed in a three-dimensional space around the cavity, wherein the cavity wall is provided with a lower cavity of 10 to 150 nm, and each hole is provided. The cavities are each three-dimensionally penetrated and the cavities of each stage also penetrate each other; the cavities are uniformly distributed, and the uniform distribution of the cavities means that the cavities are uniformly distributed under arbitrary unit volume on the porous material.
3. The polytetrafluoroethylene fiber tubular film according to claim 1 or 2, wherein the unit-level volume means a cubic centimeter-scale or cubic millimeter-order or smaller unit-level volume.
4. The polytetrafluoroethylene fiber tubular membrane according to claim 1, 2 or 3, wherein the uniform distribution of the pores refers to any three-dimensional body having a volume of not more than one cubic centimeter and the same size on the porous material. Their quality is basically the same.
5. The polytetrafluoroethylene fiber tubular membrane according to claim 4, wherein the mass is substantially equivalent to a plurality of three-dimensional bodies having a volume of not more than one cubic centimeter and the same size, which are respectively referred to as a mass, and obtained The average of their masses, and the absolute value of the deviation of any three-dimensional body mass from the mass average is not more than 4% of the average of the three-dimensional body mass.
6. The polytetrafluoroethylene fiber tubular film according to any one of claims 1 to 5, wherein the three-dimensional bodies of the same size having a volume of not more than one cubic millimeter on the multi-stage material are substantially equal in mass.
7. The polytetrafluoroethylene fiber tubular membrane according to claim 6, wherein the mass is substantially equivalent to a plurality of three-dimensional bodies of the same size having a volume of not more than one cubic millimeter which are allowed on the porous material, respectively, said mass thereof, The average of their masses, and the absolute value of the deviation of any three-dimensional body mass from the mass average is not more than 4% of the average of the three-dimensional body mass.
8. The polytetrafluoroethylene fiber tubular membrane according to any one of claims 1 to 7, which is composed of a multi-stage porous material, the body is a cavity which is classified by a material pore size, and a cavity wall which surrounds the cavity in a three-dimensional space. The lower cavity is arranged on the wall of the cavity, and the holes of each stage are respectively three-dimensionally penetrated and the holes of each stage also penetrate each other.
9. The polytetrafluoroethylene fiber tubular membrane according to any one of claims 1 to 8, wherein the lower porous material constitutes a cavity wall of the upper first cavity.
10. The polytetrafluoroethylene fiber tubular membrane according to any one of claims 1 to 8, wherein the wall of the upper cavity is composed of a plurality of porous materials of the lower stage.
11. The polytetrafluoroethylene fiber tubular membrane according to any one of claims 1 to 8, wherein the cavity wall of the upper pore cavity is composed of a composite material of the lower layers of the porous material.