Disclosure of Invention
Therefore, the invention aims to overcome the defects that polytetrafluoroethylene microporous membranes with better strength, filtering efficiency and air permeability are difficult to prepare by a simple process in the prior art, and further provides an extrusion die, a polytetrafluoroethylene film, a preparation method and application thereof.
For this purpose, the invention provides the following technical scheme.
The invention provides an extrusion die for preparing a polytetrafluoroethylene film, which comprises a first shell and a second shell which are communicated;
The first shell is provided with at least one cavity;
at least two different roughnesses are provided on the surface of the cavity which is in contact with the material.
Further, at least a first area and a second area are arranged on the surface of the cavity body contacted with the material, and the roughness of the first area is different from that of the second area;
the first area is formed by encircling a first arc line, a second arc line, a first bus and a second bus;
The second area is formed by encircling a third arc line, a fourth arc line, a first bus and a second bus.
The arc length of the first arc line is 1/10-1/2 of the circumference of the closed curve;
the roughness is 0.01-50.
The first shell is at least provided with a first cavity and a second cavity, and the second cavity is sleeved in the first cavity;
The roughness of the inner surface of the first cavity is different from the roughness of the inner surface of the second cavity, and/or,
The roughness of the inner surface of the first cavity is different from the roughness of the outer surface of the second cavity, and/or,
The roughness of the inner surface of the first cavity and the roughness of the inner surface of the second cavity are different from the roughness of the outer surface of the second cavity.
The first shell is provided with a material inlet and a material outlet;
the adjacent cavities are fixedly connected at the material inlet and the material outlet.
The cavity is in a truncated cone shape, and the ratio of the inner diameter of the section where the material inlet is located to the inner diameter of the section where the material outlet is located is 2-17.
The invention also provides a preparation method of the polytetrafluoroethylene film, which adopts the extrusion die and comprises the following steps,
And extruding, calendaring and stretching the blank to obtain the polytetrafluoroethylene film.
The preparation method of the green body comprises the steps of mixing polytetrafluoroethylene resin with an oil agent, and then performing blank making to obtain the green body, wherein the mass ratio of the polytetrafluoroethylene resin to the oil agent is 100 (10-40).
The oil may be, but is not limited to, aviation kerosene, paraffin oil, and the like.
The extrusion step in this preparation method was performed using the extrusion die described above.
In the stretching step, stretching is carried out to 2-12 times of the original length along the material flowing direction;
Stretching the material to 4-28 times of the original length in a direction orthogonal to the material flow direction;
the sheet is formed after the calendering, and the thickness of the sheet is 100-300 mu m.
The invention also provides a polytetrafluoroethylene film prepared by the preparation method.
In addition, the invention also provides a polytetrafluoroethylene film prepared by the preparation method or application of the polytetrafluoroethylene film in air filtration, liquid filtration, hydrogen energy or electronic communication.
The technical scheme of the invention has the following advantages:
1. The extrusion die for preparing the polytetrafluoroethylene film comprises a first shell and a second shell which are communicated, wherein the first shell is at least provided with a cavity, and at least two different roughnesses are arranged on the surface of the cavity contacted with materials. The polytetrafluoroethylene film prepared by the extrusion die has the advantages of high strength, high filtering efficiency, good air permeability and the like, and can be prepared without adopting a complex process.
At least two different roughnesses are arranged on the surface of a cavity in the extrusion die, so that the shearing action on materials can be increased, the fibrosis of a PTFE film is improved, the number of fibrils is increased, the strength and the filtering efficiency of the film are further improved, and the materials can be subjected to different shearing forces through the different roughnesses on the surface of the cavity, so that the PTFE film forms different microstructures in different directions.
2. According to the extrusion die provided by the invention, the size of the surface of the cavity where the roughness is located is controlled, so that the die can be adjusted and designed according to the requirements of different apertures, elongation at break and air permeability of the PTFE film.
3. The polytetrafluoroethylene film is obtained by extruding, calendaring and stretching a blank, and the roughness of the extrusion die is controlled by the extrusion die, so that the process treatment difficulty is not increased while the film fibrosis is improved, the strength, the filtration efficiency and the air permeability of the film are improved, and the process operability is ensured. The polytetrafluoroethylene film obtained by the invention has the pore diameter of less than 2 mu m, the elongation at break of more than 190 percent and the air permeability of 20-100L/dm2 min.
4. According to the preparation method of the polytetrafluoroethylene film, the PTFE film with different pore diameters, elongation at break and air permeability can be obtained by controlling the stretching proportion, so that the application requirements of different fields or different working conditions in the same field are met.
Detailed Description
The following examples are provided for a better understanding of the present invention and are not limited to the preferred embodiments described herein, but are not intended to limit the scope of the invention, any product which is the same or similar to the present invention, whether in light of the present teachings or in combination with other prior art features, falls within the scope of the present invention.
The specific experimental procedures or conditions are not noted in the examples and may be followed by the operations or conditions of conventional experimental procedures described in the literature in this field. The reagents or apparatus used were conventional reagent products commercially available without the manufacturer's knowledge.
In the description of the present invention, it should be noted that the positional or positional relationship indicated by the terms such as "upper", "lower", "horizontal", "inner", "outer", etc. are based on the positional or positional relationship shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, unless explicitly stated or limited otherwise, the term "coupled" shall be interpreted as broadly, and may be, for example, fixedly coupled, detachably coupled, integrally coupled, mechanically coupled, electrically coupled, directly coupled, indirectly coupled via an intermediate medium, or in communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
Example 1
The embodiment provides an extrusion die, which comprises a first shell 1 and a second shell 2 which are communicated,
As shown in fig. 1, the first housing 1 is provided with at least one cavity 1-1, the cavity comprises a material inlet 1-1-1 and a material outlet 1-1-2, after the material enters the first housing 1, the material is extruded and discharged from the material outlet to enter the second housing 2, and at least two different roughnesses are arranged on the surface of the cavity contacted with the material. When the extrusion die is used for preparing the polytetrafluoroethylene film, the film has the advantages of high strength, high filtering efficiency, good air permeability and the like, and meanwhile, the extrusion die has no special requirements on the processing technology of the polytetrafluoroethylene film and does not need to adopt complex procedures.
Specifically, at least two different roughnesses are set on the cavity surface, the roughness (Ra) is any one value of 0.01-50, and Ra can be at least one value of 0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, 6.3, 12.5, 25 and 50, and the number and the value of the roughness are not particularly limited in this embodiment. In this embodiment, the cavity is in the shape of a cylinder, such as a cylinder, a round table, and the like, preferably a round table, and when the cavity is a round table, the ratio of the inner diameter of the section where the material inlet is located to the inner diameter of the section where the material outlet is located is 2-17, and the material of the cavity can be, but is not limited to, brass, stainless steel, and the like. The second shell is a cylinder, such as a cylinder, a round table and the like, preferably a cylinder, and the material of the second shell can be, but is not limited to, brass, stainless steel and the like.
At least two different roughnesses are arranged on the surface of the cavity, so that materials can be subjected to different shearing forces, the fibrosis of the materials is improved, and the strength, the filtering efficiency and the air permeability of the PTFE film are further improved. The difference of fibrosis can be realized at different positions of the structure by controlling the ratio D of the maximum inner diameter Db of the cavity to the inner diameter of the second shell, and the aperture of the PTFE membrane can be effectively regulated by controlling the ratio of the maximum inner diameter to the minimum inner diameter of the cavity, so that the filter membranes with different filtering performances can be prepared.
As an improved implementation mode, at least a first area and a second area are arranged on the surface of the cavity, the roughness of the first area is different from that of the second area, the first area is formed by encircling a first arc line, a second arc line, a first bus bar and a second bus bar, the second area is formed by encircling a third arc line, a fourth arc line and the first bus bar and the second bus bar, and the arc length of the first arc line is any value of 1/10-1/2 of the circumference of a closed curve, such as 1/10, 1/8, 1/4 and the like.
Fig. 2 shows a modified embodiment, according to the inner diameter from large to small, a plurality of cavities, which can be 2, 3, 4, etc., are sleeved in the first shell 1 in sequence, and the spacing between adjacent cavities in the vertical direction is at least 3mm.
In the embodiment, the first shell is provided with a first cavity 1-1 and a second cavity 1-2, the second cavity 1-2 is sleeved in the first cavity 1-1, at least two different roughnesses are arranged on the surfaces of the first cavity 1-1 and the second cavity 1-2, which are in contact with materials, specifically, at least two different roughnesses are arranged on the inner surface of the first cavity 1-1, or the inner surface of the first cavity 1-1 and the inner surface of the second cavity 1-2 are different, or the inner surface of the first cavity 1-1 and the outer surface of the second cavity 1-2 are different, or the inner surface of the first cavity 1-1, the inner surface of the second cavity 1-2 and the outer surface of the second cavity 1-3 are different, or the inner surface of the second cavity 1-2 and the outer surface of the second cavity 1-2 are different, or the inner surface of the second cavity 1-2 is provided with at least two different roughnesses, or the two different roughnesses can be implemented.
According to the embodiment, the number of fibrils and the degree of fibrosis in the extrusion process can be improved by arranging the cavities with different roughness, and the strength, the filtering efficiency and the air permeability of the PTFE film are further improved.
As an improved implementation mode, the first cavity and the second cavity are both provided with a material inlet and a material outlet, the first cavity and the second cavity are fixedly connected through welding spots 3 at the material inlet and the material outlet, specifically, the material inlet is at least provided with one welding spot fixedly connected, and the material outlet is at least provided with one welding spot fixedly connected, so that materials can enter the first shell and the second shell.
According to the working principle of the embodiment, after materials (polytetrafluoroethylene green bodies) enter the first shell, the first cavity and the second cavity are fixedly connected through welding spots at the material inlet, the materials are scattered at the material inlet and then enter the first shell, the materials can be fibrillated due to the fact that different roughness is arranged on the surfaces of the cavities in the first shell, which are in contact with the materials, and meanwhile the scattered materials are integrated again.
Example 2
This example provides an extrusion die for preparing polytetrafluoroethylene film, as shown in fig. 3-5, comprising,
The first shell is provided with a first cavity 1-1, a second cavity 1-2 and a third cavity 1-3, the first cavity, the second cavity and the third cavity are all of a round platform structure, and the axis of the round platform structure is parallel to the horizontal plane; the inner surface a of the first cavity 1-1 is provided with a first area and a second area, the roughness of the first area is 50, the roughness of the second area is 0.025, the first area is formed by encircling a first arc line, a second arc line, a first bus and a second bus, the second area is formed by encircling a third arc line, a fourth arc line, the first bus and the second bus, the arc length of the first area is 1/2 of the circumference of a circle, namely, the circular truncated cone structure is divided into an upper part and a lower part along the horizontal direction and through the axis of the circular truncated cone structure, the first area is an upper half part, the second area is a lower half part, the inner surface b of the second cavity 1-2 is provided with 0.025 and 50 different roughness, the roughness of the upper part is 50, the lower part is 0.025, the outer surface c of the second cavity 1-2 is provided with 0.025 and 50 different roughness, the roughness of the upper part is 0.025, the lower part is the upper part of the circular truncated cone structure, the roughness of the second cavity is 0.025, and the roughness of the lower part is 0.50, and the roughness of the upper part is 0.025 and the lower part is 0.50, and the roughness of the lower part is 0.025.
The ratio of the maximum inner diameter Db to the minimum inner diameter D in the circular truncated cone structures of the first cavity, the second cavity and the third cavity is 10, the materials are brass, the first cavity, the second cavity and the third cavity are provided with a material inlet and a material outlet, adjacent cavities are fixedly connected through welding spots at the material inlet and the material outlet, and the materials entering the extrusion die can be scattered in a welding spot fixed connection mode. The spacing between two adjacent cavities in the vertical direction is 5mm.
The second shell is connected with the material outlet of the first cavity, the second shell is a cylinder, the axis of the cylinder is parallel to the horizontal plane, the ratio of the length L of the second shell to the inner diameter D of the second shell is 8, and the second shell is made of brass.
Example 3
This example provides an extrusion die for preparing polytetrafluoroethylene film, as in fig. 3, comprising,
The first shell is provided with a first cavity 1-1, a second cavity 1-2 and a third cavity 1-3, the first cavity, the second cavity and the third cavity are all of a round platform structure, and the axis of the round platform structure is parallel to the horizontal plane; the inner surface a of the first cavity 1-1 is provided with a first area and a second area, the roughness of the first area is 50, the roughness of the second area is 0.1, the first area is formed by encircling a first arc line, a second arc line, a first bus and a second bus, the second area is formed by encircling a third arc line, a fourth arc line, the first bus and the second bus, the arc length of the first area is 1/2 of the circumference of a circle, namely, the circular truncated cone structure is divided into an upper part and a lower part along the horizontal direction and passing through the axis of the circular truncated cone structure, the first area is an upper half part, the second area is a lower half part, the inner surface b of the second cavity 1-2 is provided with 12.5 and 10 different roughness, the roughness of the upper part is 12.5, the lower part is 10, the outer surface c of the second cavity 1-2 is provided with 50 and 0.1 different roughness, the roughness of the upper part is 1.5, the upper part is 10, the lower part is the upper part of the circular truncated cone structure is the lower part, the roughness of the second cavity is 10.1-10, and the roughness of the upper part is 10.1-10, and the roughness of the lower part is the surface of the circular truncated cone is 10.1-10, and the roughness of the lower part is the upper part is the surface of the circular truncated cone is the lower part and the lower part is the same with the roughness of the surface 1-10.1.
The ratio of the maximum inner diameter to the minimum inner diameter in the circular truncated cone structures of the first cavity, the second cavity and the third cavity is 6, the materials are brass, the first cavity, the second cavity and the third cavity are provided with a material inlet and a material outlet, adjacent cavities are fixedly connected through welding spots at the material inlet and the material outlet, and the materials entering the extrusion die can be scattered in a welding spot fixed connection mode. The spacing between two adjacent cavities in the vertical direction is 5mm.
The second shell is connected with the material outlet of the first cavity, the second shell is a cylinder, the axis of the cylinder is parallel to the horizontal plane, the ratio of the length of the second shell to the inner diameter of the second shell is 9, and the second shell is made of brass.
Example 4
The embodiment provides an extrusion die for preparing a polytetrafluoroethylene film, comprising,
The first shell is provided with a first cavity, a second cavity and a third cavity, the inner surface a of the first cavity 1-1 is provided with a first area and a second area, the roughness of the first area is 50, the roughness of the second area is 0.025, the first area is formed by encircling a first arc line, a second arc line, a first bus and a second bus, the second area is formed by encircling a third arc line, a fourth arc line, the first bus and the second bus, the arc length of the first area is 1/5 of the circumference of a circle where the first area is located, the roughness of the inner surface of the second cavity is 40, the roughness of the outer surface of the second cavity is 0.025, and the roughness of the outer surface and the inner surface of the third cavity are the same and are 25.
The first cavity, the second cavity and the third cavity are of round table structures, the ratio of the maximum inner diameter to the minimum inner diameter is 4, the materials are stainless steel, the first cavity, the second cavity and the third cavity are provided with a material inlet and a material outlet, adjacent cavities are fixedly connected through welding spots at the material inlet and the material outlet, and the materials entering the extrusion die can be scattered in a welding spot fixed connection mode.
The second shell is connected with the material outlet of the first cavity, the second shell is a cylinder, the axis of the cylinder is parallel to the horizontal plane, the ratio of the length of the second shell to the inner diameter of the second shell is 12, and the second shell is made of brass.
Example 5
This example provides a method for preparing a polytetrafluoroethylene film using the extrusion die of example 2, the method comprising,
The polyethylene resin is selected from Dajin F104, aviation kerosene is used as an oiling agent, the mass ratio of the Dajin F104 to the aviation kerosene is 100:15, and the mixture is aged and shaped into a blank;
The sheet having a thickness of 300 μm was obtained by extrusion through an extrusion die of example 2, and after deoiling, it was stretched at 350℃and stretched to 9 times the original length in the sheet flow direction and 15 times the original length in the direction orthogonal to the sheet flow direction, to obtain a polytetrafluoroethylene film having a film pore diameter of 0.78 μm, an elongation at break of 168%, an air permeability of 80L/dm2. Min, and a filtration efficiency of 99.9996% (test condition @2.5cm/s,0.19 μm) after compounding with a nonwoven fabric, wherein the elongation at break was measured in accordance with GB/T7689.5, the air permeability was in accordance with GB/T5453, the effective area of the sample was 50cm2, the fixed pressure difference was 127Pa, and the number of samples per sample was 10. The test standard of the filtration efficiency is CRAA431.3, specifically, after the PTFE film and the non-woven fabric are compounded, TSI3140 is utilized, the solvent is paraffin oil, the particle size is 0.19 mu m, and the test wind speed is 2.5cm/s.
Example 6
This example provides a method for preparing a polytetrafluoroethylene film, using the extrusion die of example 3, comprising,
The Eastern Mountain DF-201 is selected as the polyethylene resin, aviation kerosene is used as the oiling agent, the mass ratio of Dajin F104 to aviation kerosene is 100:20, and the mixture is aged and shaped into a blank;
the sheet having a thickness of 300 μm was obtained by extrusion through an extrusion die of example 2, and after deoiling, it was stretched at 350℃and stretched to 6 times the original length in the sheet flow direction and 12 times the original length in the direction orthogonal to the sheet flow direction, to obtain a polytetrafluoroethylene film having a film pore diameter of 0.92 μm, an elongation at break of 180% and a ventilation of 100L/dm2. Min, and a filtration efficiency of 99.999% (test condition @2.5cm/s,0.19 μm) after compounding with a nonwoven fabric, wherein the test method was the same as in example 5.
Comparative example 1
The comparative example provides a method for producing a polytetrafluoroethylene film using an extrusion die differing from that of example 2 in that the surface roughness of the first cavity, the second cavity and the third cavity in the extrusion die used in the comparative example are all 50, and the other extrusion dies are the same as those of example 2, the method comprising the steps of,
The polyethylene resin is selected from Dajin F104, aviation kerosene is used as an oiling agent, the mass ratio of the Dajin F104 to the aviation kerosene is 100:15, and the mixture is aged and shaped into a blank;
The sheet having a thickness of 300 μm was obtained by extrusion using the extrusion die of the comparative example, and after deoiling, it was stretched at 350℃and stretched to 9 times the original length in the sheet flow direction and 15 times the original length in the direction orthogonal to the sheet flow direction, to obtain a polytetrafluoroethylene film having a film pore diameter of 0.96 μm, an elongation at break of 150% and a ventilation of 70L/dm2. Min, and a filtration efficiency of 99.997% (test condition @2.5cm/s,0.19 μm) after compounding with a nonwoven fabric, and the test method was the same as in example 5.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.