WO2021112198A1 - ポリテトラフルオロエチレン延伸多孔質膜とこれを用いた通気濾材及びフィルター部材 - Google Patents
ポリテトラフルオロエチレン延伸多孔質膜とこれを用いた通気濾材及びフィルター部材 Download PDFInfo
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- WO2021112198A1 WO2021112198A1 PCT/JP2020/045119 JP2020045119W WO2021112198A1 WO 2021112198 A1 WO2021112198 A1 WO 2021112198A1 JP 2020045119 W JP2020045119 W JP 2020045119W WO 2021112198 A1 WO2021112198 A1 WO 2021112198A1
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- Prior art keywords
- stretched porous
- porous membrane
- ptfe
- filter medium
- stretching
- Prior art date
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- C08J2327/18—Homopolymers or copolymers of tetrafluoroethylene
Definitions
- the present invention relates to a polytetrafluoroethylene (hereinafter referred to as "PTFE”) stretched porous membrane, and a ventilation filter medium and a filter member using the same.
- PTFE polytetrafluoroethylene
- a filter member provided with a ventilation filter medium may be attached to the housing of various electric products such as vehicle electrical components and mobile information terminals so as to cover the opening provided in the housing.
- the ventilation filter medium has air permeability in the thickness direction, while preventing the permeation of foreign substances such as dust and water. By attaching the filter member, it is possible to secure ventilation through the opening while preventing the passage of foreign matter through the opening. It is conceivable to use a PTFE stretched porous membrane as the aeration filter medium.
- Patent Document 1 discloses a highly breathable PTFE stretched porous membrane.
- Patent Document 2 discloses a highly breathable PTFE-stretched porous membrane having high ball burst strength.
- the breathability of the filter member can be improved, which makes it possible to promote the miniaturization of the member.
- damage such as cracks is caused by PTFE when the member is handled or placed in a housing or the like. It tends to occur in the stretched porous membrane.
- a property that is less likely to be damaged is also desired for a PTFE-stretched porous membrane that does not have high air permeability.
- An object of the present invention is to provide a PTFE-stretched porous membrane that is less likely to be damaged.
- the present invention A PTFE-stretched porous membrane having a node / fibril structure comprising a plurality of nodes and a fibril connecting the plurality of nodes.
- the present invention A ventilation filter medium that has air permeability in the thickness direction and prevents foreign matter from permeating in that direction.
- the aeration filter medium provided with the above-mentioned PTFE-stretched porous membrane of the present invention. I will provide a.
- the present invention It has ventilation in the thickness direction and is equipped with a ventilation filter medium that prevents foreign matter from penetrating in that direction.
- the filter member, wherein the ventilation filter medium is the ventilation filter material of the present invention. I will provide a.
- a PTFE-stretched porous membrane that is less likely to be damaged is achieved.
- FIG. 1 It is sectional drawing which shows typically an example of the PTFE stretched porous membrane of this invention. It is an enlarged view of the cross section of the PTFE stretched porous membrane of FIG. It is a figure for demonstrating the method of evaluating the structure of a PTFE stretched porous membrane by X-ray CT. It is a figure for demonstrating the method of evaluating the structure of a PTFE stretched porous membrane by X-ray CT. It is sectional drawing which shows typically an example of the ventilation filter medium of this invention. It is sectional drawing which shows typically another example of the ventilation filter medium of this invention. It is sectional drawing which shows typically an example of the filter member of this invention. It is sectional drawing which shows typically another example of the filter member of this invention.
- the PTFE stretched porous membrane 1 of FIG. 1 has a node / fibril structure including a plurality of nodes (nodules) and a fibril connecting the plurality of nodes.
- the node is the aggregated portion of PTFE.
- the PTFE-stretched porous membrane 1 is usually formed by stretching a PTFE sheet. In this forming method, the portion that has become fine fibryl (fibrillated) by stretching corresponds to fibril. On the other hand, the portion that is not fibrillated and retains the aggregated state of PTFE corresponds to the node.
- a node is usually connected to a plurality of fibrils. As shown in FIG.
- FIG. 2 is an enlarged view of a cross section of the PTFE stretched porous membrane 1 (fibril is not shown).
- the ratio R may be 12% or more, 14% or more, 15% or more, 16% or more, and further 18% or more.
- a large ratio R means that each node 11 extends long in the thickness direction of the PTFE stretched porous membrane 1.
- the damage of the PTFE-stretched porous membrane 1 that may occur when the filter member is handled or placed in the housing is caused by a force exceeding the cohesive force of the membrane 1 on the membrane. It is caused by destruction (cohesive destruction) due to addition.
- the node 11 extending long in the thickness direction can improve the cohesive force of the PTFE-stretched porous membrane 1 and suppress the cohesive failure. Therefore, the PTFE stretched porous membrane 1 is unlikely to be damaged.
- the PTFE stretched porous membrane 1 may have a more characteristic node / fibril structure. Assuming a rectangular parallelepiped region having an upper surface and a lower surface having a size of 280 ⁇ m ⁇ 280 ⁇ m and having an upper surface and a lower surface located on one membrane surface and the other membrane surface of the PTFE stretched porous film 1, it is included in the region.
- the number N of the nodes 11 per 1 ⁇ m of the thickness is, for example, 4 or less.
- the number N may be 3 or less, 2 or less, 1.5 or less, 1.3 or less, 1.2 or less, 1.1 or less, 1.0 or less, and further 0.9 or less.
- the lower limit of the number N is, for example, 0.3 or more.
- the degree to which the nodes are divided in the thickness direction is high, and the above ranges cannot be achieved for the ratio R and the number N.
- the length of the thickness direction of the node 11 L, the number N of the average length L M and the node 11 is the average value of the length L is, for example, using an X-ray CT apparatus for PTFE stretched porous film 1 3 It can be evaluated by dimensional image structure analysis (see FIGS. 3A and 3B).
- a rectangular parallelepiped evaluation region 21 including the entire PTFE-stretched porous film 1 in the direction parallel to the film surface and 280 ⁇ m ⁇ 280 ⁇ m in the thickness direction is set in the film 1.
- the thickness of the evaluation region 21 may be larger than the thickness of the PTFE stretched porous film 1 (see FIG.
- the thickness of the PTFE stretched porous film 1 It is preferably about 5 times or less the thickness.
- the breathable support material is not included in the evaluation region 21.
- a continuous transmission image is acquired while rotating the slice position at predetermined intervals. The rotation is carried out, for example, with respect to a rotation axis extending in the Z direction through the center of the main surface of the film 1, with the MD direction of the film 1 being the X direction, the TD direction being the Y direction, and the thickness direction being the Z direction. ..
- the number of continuous transmission images to be acquired is preferably 300 or more, more preferably 500 or more, still more preferably 700 or more, and particularly preferably 800 or more.
- a three-dimensional image of the evaluation region 21 is constructed using the acquired continuous transmission image.
- the software attached to the X-ray CT apparatus can be used to construct the three-dimensional image.
- the node 11 is extracted from the constructed three-dimensional image (see FIG. 3A).
- the node 11 can be extracted by binarizing the void and the other portion in the PTFE stretched porous membrane 1, typically the node 11 and the fibril, and separating the node 11 and the fibril after the binarization.
- Node 11 and fibril can usually be separated by diameter.
- the diameter of the node 11 is, for example, 1 ⁇ m or more, and may be 1.5 ⁇ m or more, 2 ⁇ m or more, and 3 ⁇ m or more.
- the diameter of the fibril is, for example, less than 1 ⁇ m, and may be 0.8 ⁇ m or less, 0.5 ⁇ m or less, and 0.1 ⁇ m or less.
- the "diameter" can be determined by the length of the shortest line segment among the virtual line segments that exist only inside the three-dimensional object and pass through the center of gravity of the object. .. Further, the separation of the node 11 and the fibril can be performed as a simpler method, for example, based on the volume of the PTFE body displayed in the three-dimensional image constructed by the X-ray CT, for example, the X-ray CT.
- a fibril is a PTFE body having a volume of 500 voxel (21.44 ⁇ m 3 ) or less, and a PTFE body having a volume exceeding 500 voxel (21.44 ⁇ m 3 ) is a node.
- the image analysis software is, for example, ImageJ, which is free software developed by the National Institutes of Health. In ImageJ, binarization by the Li method can be performed. Further, in ImageJ, the node 11 and the fibril can be separated by adjusting the threshold value of the noise removal command.
- the number N can be obtained by dividing the number of the extracted nodes 11 by the thickness (unit: ⁇ m) of the PTFE stretched porous membrane 1.
- a rectangular parallelepiped 22 (each surface parallel to the XY plane, the XY plane, and the YY plane) circumscribing each of the extracted nodes 11 is assumed on the image analysis software.
- the length L 2 of the rectangular parallelepiped 22 in the film thickness direction can be the length L of each node 11 (see FIG. 3B).
- the length L of all of the nodes 11 included in the evaluation region 21 was evaluated, it is possible to make the average value average length L M.
- the upper limit of the average length L M of the node 11 in the PTFE stretched porous film 1 is, for example, 70 ⁇ m or less, 60 [mu] m or less, 50 [mu] m or less, 40 [mu] m or less, 30 [mu] m or less, more may be 20 ⁇ m or less.
- the lower limit of the average length L M is, for example, 5 ⁇ m or more, 7 [mu] m or more, more may be 9 ⁇ m or more.
- the volume fraction of the node 11 in the PTFE stretched porous membrane 1 is, for example, 5% or more, 7% or more, 8.5% or more, and further 10% or more.
- the upper limit of the volume fraction is, for example, 30% or less, 25% or less, and further 20% or less.
- An appropriate range of volume fraction contributes to the achievement of a PTFE-stretched porous membrane that is highly breathable but resistant to breakage.
- the volume fraction can be evaluated by the above three-dimensional image analysis.
- the average value of the node angle ⁇ in the PTFE stretched porous membrane 1 may be, for example, 60 degrees or more, 65 degrees or more, or even 70 degrees or more.
- the upper limit of the average value of the node angle ⁇ is 90 degrees or less, 85 degrees or less, and may be 80 degrees or less.
- An appropriate range of the above average values contributes to the achievement of a PTFE-stretched porous membrane that is highly breathable but resistant to breakage.
- the node angle ⁇ is a plane selected from the XZ plane and the YZ plane where the thickness of the node 11 can be observed (when the stretching A is performed in the MD direction in the method A described later, the film is usually formed.
- the long axis of the ellipse is X.
- the node angle ⁇ and its average value can be evaluated by the above three-dimensional image analysis (a plane image can be extracted from the three-dimensional image of the evaluation area).
- the average value is the average value of all the nodes 11 included in the evaluation area 21.
- the average thickness of the nodes 11 in the PTFE stretched porous membrane 1 is, for example, 0.5 to 5 ⁇ m, and may be 1 to 3 ⁇ m. An appropriate range of average thickness contributes to the achievement of a PTFE stretched porous membrane that is highly breathable but resistant to breakage.
- the thickness and average thickness of the node 11 can be evaluated by the above-mentioned three-dimensional image analysis (analysis of an image of a plane in which the thickness of the node 11 can be observed among the planes selected from the XZ plane and the YY plane).
- the thickness of the node 11 draws an inscribed circle of the node 11 centered on each pixel for all the pixels indicating the node 11 on the image of the plane, and if the inscribed circles overlap, a larger area is obtained.
- the diameter of each remaining inscribed circle can be made into a histogram and determined as the average value (number average value) in the distributed diameter that is plotted.
- the average thickness is the average value of the thicknesses of all the nodes 11 included in the evaluation region 21.
- the node 11 is less divided in the thickness direction. Therefore, the PTFE stretched porous membrane 1 can have high air permeability.
- the air permeability of the PTFE stretched porous membrane 1 in the thickness direction may be 4 cm 3 / (sec 2 ) or more, which is indicated by the Frazier air permeability.
- the air permeability is 4.5 cm 3 / (seconds / cm 2 ) or more, 5.0 cm 3 / (seconds / cm 2 ) or more, 6.0 cm 3 / (seconds / cm 2 ) or more, 7.0 cm 3 / ( It may be seconds ⁇ cm 2 ) or more, and further may be 8.0 cm 3 / (seconds ⁇ cm 2 ) or more.
- the upper limit of the air permeability is, for example, 20.0 cm 3 / (sec 2 ) or less.
- the in-plane air permeability of the PTFE stretched porous membrane 1 does not have to be high, and the membrane may have, for example, a lower in-plane air permeability than shown in the above range.
- Frazier air permeability is determined in accordance with the air permeability measurement method A (Frazil type method) specified in Japanese Industrial Standards (hereinafter referred to as "JIS") L1096. Even if the size of the PTFE stretched porous membrane 1 is less than the size of the test piece (about 200 mm ⁇ 200 mm) in the Frazier method, the Frazier ventilation can be performed by using a measuring jig that limits the area of the measurement area. The degree can be evaluated.
- An example of a measuring jig is a resin plate having a through hole formed in the center having a cross-sectional area corresponding to the area of a desired measuring area. For example, a measuring jig having a through hole having a circular cross section having a diameter of 1 mm or less and formed in the center can be used.
- the PTFE stretched porous membrane 1 may have a high cohesive force (peeling cohesive force) on average in the entire in-plane direction.
- the total cohesive force of the PTFE stretched porous membrane 1 may be 1.9 (N / 20 mm) 2 or more. In this case, the above damage can be further suppressed.
- the total cohesive force is indicated by the product of the in-plane peeling cohesive force of the PTFE stretched porous membrane 1 and the in-plane peeling cohesive force in the second direction orthogonal to each other. ..
- the first direction is, for example, the MD direction.
- the second direction is, for example, the TD direction.
- Total cohesive force is 2.0 (N / 20mm) 2 or more, 2.5 (N / 20mm) 2 or more, 2.8 (N / 20mm) 2 or more, and 3.0 (N / 20mm) 2 or more. It may be.
- the upper limit of the total cohesive force is, for example, 25.0 (N / 20 mm) 2 or less, 20.0 (N / 20 mm) 2 or less, 15.0 (N / 20 mm) 2 or less, 10.0 (N / N /). It may be 20 mm) 2 or less, 8.0 (N / 20 mm) 2 or less, and further 6.4 (N / 20 mm) 2 or less.
- the PTFE-stretched porous film is usually formed by stretching an unstretched PTFE sheet, which is a raw sheet, in two directions orthogonal to each other in the sheet surface, for example, the MD direction and the TD direction.
- the stretching conditions for each direction are usually different, and therefore, the mechanical properties of the film are usually different between the two directions orthogonal to each other.
- the present inventors for example, when incorporated into a filter member, even if it has a high peeling cohesive force in one direction, when the peeling cohesive force in a different direction is low. The film tends to be damaged when the member is handled or placed in the housing.
- the total cohesive force is the product of the peeling cohesive force in the first direction in the plane and the peeling cohesive force in the second direction orthogonal to the first direction in the plane.
- the PTFE-stretched porous membrane 1 having a total cohesive force of 1.9 (N / 20 mm) 2 or more has a high peeling cohesive force on average in the in-plane direction of the film. Then it can be judged.
- the peeling cohesive force in the first direction of the PTFE stretched porous membrane 1 is, for example, 1.70 (N / 20 mm) or more, 1.80 (N / 20 mm) or more, and 1.90 (N / 20 mm). The above, and further, it may be 2.00 (N / 20 mm) or more.
- the peeling cohesive force in the second direction of the PTFE stretched porous membrane 1 is, for example, 1.15 (N / 20 mm) or more, 1.20 (N / 20 mm) or more, and 1.40 (N / 20 mm). As mentioned above, it may be 1.50 (N / 20 mm) or more, 1.60 (N / 20 mm) or more, and further 1.70 (N / 20 mm) or more.
- the average cohesive force of the PTFE-stretched porous film 1 represented by the average (arithmetic mean) of the peeling cohesive force in the first direction and the peeling cohesive force in the second direction is, for example, 1.40 (N / 20 mm). ) Or more, 1.50 (N / 20 mm) or more, 1.60 (N / 20 mm) or more, 1.70 (N / 20 mm) or more, and even 1.80 (N / 20 mm) or more. Good.
- the PTFE stretched porous membrane 1 may satisfy the formula C T ⁇ ⁇ 0.33 ⁇ P T +3.67 by displaying the air permeability in the thickness direction as P T and the total cohesive force as C T. , Equation C T ⁇ ⁇ 0.57 ⁇ P T +6.14 may be satisfied.
- PTFE includes modified PTFE.
- the PTFE stretched porous membrane 1 includes a stretched porous membrane of modified PTFE.
- the modified PTFE is a copolymer of tetrafluoroethylene (hereinafter referred to as “TFE”) and a modified comonomer.
- TFE tetrafluoroethylene
- the content of TFE units in the copolymer is, for example, 95% by mass or more, preferably 97% by mass or more, and more preferably 99% by mass or more.
- the modified comonomer is, for example, at least one selected from ethylene, perfluoroalkyl vinyl ether, hexafluoropropylene and perfluoromethyl vinyl ether.
- the denatured PTFE may be excluded from the PTFE.
- the PTFE may be unmodified PTFE (a homopolymer of TFE).
- the standard specific gravity (SSG) of PTFE may be 2.18 or less. SSG is defined in JIS K9635-1.
- the basis weight of the PTFE stretched porous membrane 1 is, for example, 1.0 g / m 2 or more, 7.0 g / m 2 or more, 8.0 g / m 2 or more, 10.0 g / m 2 or more, 12.0 g / m. It may be m 2 or more, and further may be 13.0 g / m 2 or more.
- the upper limit of the basis weight is, for example, 87.2 g / m 2 or less.
- the basis weight can be obtained by dividing the weight of the PTFE stretched porous membrane 1 by the area of the main surface.
- the thickness of the PTFE stretched porous membrane 1 may be, for example, 10 ⁇ m or more, 30 ⁇ m or more, 35 ⁇ m or more, 40 ⁇ m or more, and further 45 ⁇ m or more.
- the upper limit of the thickness is, for example, 200 ⁇ m or less, and may be 100 ⁇ m or less.
- the porosity of the PTFE stretched porous membrane 1 is, for example, 80% or more, and may be 85% or more, 88% or more, or even 90% or more.
- the upper limit of the porosity is, for example, 99% or less.
- the porosity can be calculated by substituting the mass, thickness, area (area of the main surface) of the film and the true density of PTFE into the following formula.
- the true density of PTFE is 2.18 g / cm 3 .
- Porosity (%) ⁇ 1- (mass [g] / (thickness [cm] x area [cm 2 ] x true density [g / cm 3 ])) ⁇ x 100
- the bulk density of the PTFE stretched porous film 1 is, for example, 0.30 g / cm 3 or less, 0.25 g / cm 3 or less, 0.20 g / cm 3 or less, 0.19 g / cm 3 or less, 0.18 g. It may be / cm 3 or less, 0.16 g / cm 3 or less, and further 0.15 g / cm 3 or less.
- the lower limit of bulk density is, for example, 0.08 g / cm 3 or more.
- An appropriate range of bulk density contributes to the achievement of a PTFE-stretched porous membrane that is highly breathable but resistant to breakage.
- the bulk density can be determined from the basis weight and thickness of the PTFE stretched porous membrane 1.
- the water pressure resistance (limit water pressure resistance) of the PTFE stretched porous membrane 1 may be, for example, 30 kPa or more, 35 kPa or more, 40 kPa or more, 44 kPa or more, and further 50 kPa or more.
- the upper limit of water pressure resistance is, for example, 500 kPa or less.
- the water pressure resistance can be measured as follows using a measuring jig in accordance with the water resistance test A method (low water pressure method) or B method (high water pressure method) specified in JIS L1092.
- An example of a measuring jig is a stainless steel disk having a diameter of 47 mm, which is provided with a through hole (having a circular cross section) having a diameter of 1 mm in the center. This disk has a thickness that is not deformed by the water pressure applied when measuring the water pressure resistance.
- the water pressure resistance can be measured using this measuring jig as follows.
- the PTFE stretched porous membrane 1 to be evaluated is fixed to one surface of the jig so as to cover the opening of the through hole of the measuring jig. Fixing is performed so that water does not leak from the fixed portion of the membrane during the measurement of water pressure resistance.
- a double-sided adhesive tape having a water passage port having a shape matching the shape of the opening punched in the center can be used.
- the double-sided adhesive tape may be placed between the measuring jig and the membrane so that the circumference of the water passage and the circumference of the opening coincide with each other.
- the measuring jig on which the membrane is fixed is set in the test device so that the surface opposite to the fixed surface of the membrane is the water pressure application surface at the time of measurement, and the water resistance test method A (low water pressure) of JIS L1092 is set.
- the water pressure resistance is measured according to the method) or the B method (high water pressure method).
- the water pressure resistance is measured based on the water pressure when water comes out from one place on the membrane surface of the PTFE stretched porous membrane 1.
- the measured water pressure resistance can be used as the water pressure resistance of the PTFE stretched porous membrane 1.
- As the test apparatus an apparatus having the same configuration as the water resistance test apparatus exemplified in JIS L1092 and having a test piece mounting structure in which the above-mentioned measuring jig can be set can be used.
- the PTFE stretched porous membrane 1 may be a single-layer membrane.
- the PTFE stretched porous film 1 may be subjected to a liquid repellent treatment such as a water repellent treatment and an oil repellent treatment.
- the liquid repellent treatment can be carried out by coating with a liquid repellent substance such as a fluorine-based compound. A known method can be adopted for coating.
- the PTFE stretched porous film 1 may be colored.
- the coloring treatment can be carried out, for example, by dyeing the PTFE stretched porous film 1 or by impregnating the PTFE stretched porous film 1 with a colorant.
- the coloring treatment may be carried out so that light having a wavelength in the range of 380 to 500 nm is absorbed.
- the PTFE stretched porous film 1 can be colored blue, gray, brown, pink, green, yellow, or the like.
- the PTFE stretched porous membrane 1 can be used, for example, as a ventilation filter medium which has air permeability in the thickness direction and prevents foreign matter from permeating in the direction.
- foreign substances are particles such as dust and liquid water such as water droplets.
- the use of the PTFE stretched porous membrane 1 is not limited to the above example.
- the PTFE stretched porous membrane 1 can be produced, for example, by the following method A.
- the PTFE stretched porous membrane 1 may be a membrane obtained by the method A.
- the method for producing the PTFE stretched porous membrane 1 is not limited to the method A.
- Method A An unbaked PTFE sheet is stretched in a predetermined direction at a stretching temperature below the melting point of PTFE (stretching A); The sheet that has undergone stretching A is fired at a temperature equal to or higher than the melting point of PTFE (firing B); The sheet that has undergone firing B is further stretched in a direction different from the above-mentioned predetermined direction at a stretching temperature below the melting point of PTFE (stretching C).
- Stretching A In stretching A, the unfired PTFE sheet is stretched in a predetermined direction at a stretching temperature lower than the melting point of PTFE (the melting point of crystals, 343 ° C.). Stretching A can be carried out, for example, in a heating furnace controlled to a temperature (stretching temperature) at which stretching A is carried out. Stretching A can be performed, for example, by roll stretching. However, the method of carrying out stretching A is not limited to the above example.
- the stretching temperature of stretching A is, for example, 200 to 340 ° C, and may be 280 to 330 ° C.
- the draw ratio of the stretch A is, for example, 1.5 to 10.0 times, and may be 2.0 to 8.0 times.
- the draw ratio is preferably 4.0 to 5.0 times.
- the draw ratio is preferably 3.0 to 4.0 times.
- the direction of stretching A is, for example, the MD direction of the PTFE sheet.
- the direction of stretching A may be the longitudinal direction of the PTFE sheet.
- Stretching A is preferably carried out in a state where the degree of stretching per hour is suppressed. It is considered that the suppressed stretching A contributes to the formation of the PTFE stretched porous film 1 having the node / fibril structure. According to the study by the present inventors, the suppressed stretching A and the subsequent firing B tend to form a node 11 that extends not only in the in-plane direction but also in the thickness direction of the film.
- the suppressed stretching can be carried out, for example, by reducing the stretching ratio per hour.
- the stretching ratio per hour is, for example, 0.5 to 5.0 / min, 0.5 to 3.0 / min, 0.5 to 2.0 / min, and further, expressed in terms of strain rate. It may be 0.5 to 1.9 / min.
- the strain rate can be obtained by dividing the stretching speed (m / min) by the stretching distance (m). The strain rate is usually constant in stretching A.
- firing B the sheet that has undergone stretching A is fired at a temperature equal to or higher than the melting point of PTFE.
- the firing B can be carried out, for example, in a heating furnace controlled to a temperature at which the firing B is carried out (firing temperature).
- the firing temperature is, for example, 350 to 400 ° C, and may be 355 to 395 ° C.
- the firing time is, for example, 10 to 40 seconds and may be 12 to 38 seconds.
- Baking B is preferably carried out in a state where the sheet is not stretched. It is presumed that performing firing in this state between stretching A and stretching C contributes to the formation of the PTFE stretched porous having the node / fibril structure. According to the study by the present inventors, the node 11 formed by the stretching A is heat-fixed by the firing B, whereby the structure of the node 11 is maintained by the stretching C that expands the gap between the fibrils. ..
- the draw ratio allowed in firing B is, for example, 0.80 to 2.00 times, preferably 0.90 to 1.10 times.
- a draw ratio of less than 1 means shrinkage.
- the PTFE-stretched porous film 1 obtained through firing B is a fired film. From this aspect, the PTFE stretched porous film 1 may be a fired film.
- Stretching C In stretching C, the sheet that has undergone firing B is further stretched in a direction different from the above-mentioned predetermined direction at a stretching temperature below the melting point of PTFE. Stretching C can be carried out, for example, in a heating furnace controlled to a temperature (stretching temperature) at which stretching C is carried out. Stretching C can be carried out, for example, by tenter stretching. However, the method of carrying out stretching C is not limited to the above example.
- the stretching temperature of stretching C is, for example, 40 to 340 ° C, and may be 100 to 330 ° C.
- the draw ratio of the stretch C is, for example, 2 to 15 times, and may be 4 to 10 times.
- the direction of stretching C is typically a direction substantially perpendicular to the direction of stretching A in the sheet surface.
- the direction of stretching C is, for example, the TD direction of the PTFE sheet.
- the direction of the stretch C may be the width direction of the PTFE sheet.
- stretching other than stretching A and stretching C may be carried out, if necessary.
- the first stretching performed on the PTFE sheet is stretching A.
- only stretching A and stretching C may be carried out as stretching of the PTFE sheet. Stretching A, firing B and stretching C may be carried out continuously.
- the PTFE stretched porous membrane 1 obtained by Method A is typically a biaxially stretched membrane. From this aspect, the PTFE stretched porous membrane 1 may be a biaxially stretched membrane.
- the unfired PTFE sheet to be used in Method A can be formed by, for example, forming a mixture of PTFE fine powder (fine powder) and a liquid lubricant into a sheet by extrusion and / or rolling.
- the liquid lubricant is preferably removed from the PTFE sheet before stretching A by a method such as heating or extraction. Further, after removing the liquid lubricant, it is preferable not to apply a compressive force in the thickness direction of the unfired PTFE sheet, in other words, the PTFE sheet (non-dense) which has not been densified by applying the compressive force. It is preferable to stretch the chemical sheet).
- liquid lubricants are liquid paraffin, naphtha, white oil, hydrocarbon oils such as toluene and xylene, various alcohols, ketones, and esters.
- the liquid lubricant is not limited to the above example as long as it can wet the surface of the PTFE fine powder and can be removed after the mixture is formed into a sheet.
- the mixing ratio of the PTFE fine powder and the liquid lubricant is usually about 5 to 50 parts by weight of the liquid lubricant with respect to 100 parts by weight of the PTFE fine powder.
- the thickness of the unfired PTFE sheet can be adjusted by the thickness of the PTFE stretched porous film 1 to be obtained, and is, for example, about 0.05 to 0.5 mm.
- any process can be carried out after stretching C, if necessary.
- An example of the process is thermal fixation that holds the sheet at a temperature above the melting point of PTFE.
- the structure of the stretched sheet is maintained by heat fixation.
- Heat fixing can be carried out in the same manner as in firing B.
- Thermal fixation may be carried out continuously following stretching C.
- Ventilation filter medium An example of the ventilation filter medium of the present invention is shown in FIG.
- the aeration filter medium 2 (2A) of FIG. 4 includes a PTFE stretched porous membrane 1.
- Another example of the ventilation filter medium of the present invention is shown in FIG.
- the ventilation filter medium 2 (2B) of FIG. 5 further includes a ventilation support material 3.
- the breathable support material 3 is laminated on the PTFE stretched porous membrane.
- the breathable support material 3 can improve the strength and handleability of the breathable filter medium 2.
- the breathable support material 3 usually has higher breathability in the thickness direction than the PTFE stretched porous membrane 1.
- Examples of the breathable support material 3 are woven fabrics, non-woven fabrics, nets and meshes.
- Examples of materials constituting the breathable support material 3 are polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene (PE) and polypropylene (PP), and aramid resins.
- the shape of the breathable support member 3 may be the same as or different from the shape of the PTEF stretched porous membrane 1 when viewed perpendicular to the main surface of the breathable filter medium 2.
- the breathable support member 3 may have a shape corresponding to the peripheral edge portion of the PTFE stretched porous membrane 1 when viewed perpendicularly to the main surface of the breathable filter medium 2.
- the shape is ring-shaped when the shape of the PTFE-stretched porous membrane 1 is circular.
- the configuration and shape of the breathable support member 3 are not limited to the above examples.
- the ventilation filter medium 2B includes one breathable support material 3 arranged on one surface of the PTFE stretched porous membrane 1.
- the ventilation filter medium 2 may include two or more breathable support members 3.
- the aeration support material 3 may be arranged on both surfaces of the PTFE stretched porous membrane 1.
- the PTFE stretched porous membrane 1 and the breathable support material 3 may be joined by welding such as heat welding and ultrasonic welding, an adhesive, an adhesive or the like.
- the ventilation filter medium 2 may include any layer and / or member other than those described above.
- the thickness of the aeration filter medium 2 is, for example, 10 to 300 ⁇ m, and may be 50 to 200 ⁇ m.
- the basis weight of the ventilation filter medium 2 is, for example, 1.0 to 200.0 g / m 2 , and may be 10.0 to 100.0 g / m 2.
- the aeration filter medium 2 may have the same characteristics as the PTFE stretched porous membrane 1, for example, air permeability and / or water pressure resistance in the thickness direction.
- the aeration filter medium 2 may be subjected to a liquid repellent treatment and / or a coloring treatment.
- the shape of the ventilation filter medium 2 is, for example, a polygon including a square and a rectangle, a circle, an ellipse, and a band when viewed perpendicular to the main surface of the ventilation filter medium 2.
- the corners of the polygon may be rounded.
- the shape of the ventilation filter medium 2 is not limited to the above example.
- the strip-shaped ventilation filter medium 2 may be wound to form a wound body. Further, if necessary, it may be wound in a state of being laminated with a release sheet (separator).
- the polygon, a circle, the area of the vent filter medium 2 is a sheet form having the shape of an ellipse or the like may be 675 mm 2 or less, may be 175mm 2 or less.
- the lower limit of the area is, for example, 0.20 mm 2 or more.
- the ventilation filter medium 2 having the area is suitable for use in a miniaturized filter member. However, the area of the aeration filter medium 2 may be a larger value depending on its use.
- the ventilation filter medium 2 can be used as a filter member, for example. However, the use of the ventilation filter medium 2 is not limited to the above example.
- the filter member 4 (4A) of FIG. 6 includes the ventilation filter medium 2 described above as a ventilation filter medium which has air permeability in the thickness direction and prevents foreign matter from permeating in the direction.
- the filter member 4A is, for example, a member that is arranged on the surface of an object having a surface having an opening and secures ventilation through the opening while preventing the permeation of foreign matter in the opening.
- the filter member 4A is usually arranged so that the ventilation filter medium 2 covers the opening of the object.
- the filter member 4A includes an adhesive layer 5 arranged on one side of the ventilation filter medium 2.
- the aeration filter medium 2 and the pressure-sensitive adhesive layer 5 are directly joined.
- the filter member 4A can be arranged on the surface of the object via the pressure-sensitive adhesive layer 5.
- the aeration filter medium 2 includes a PTFE stretched porous membrane 1 having a specific node / fibril structure and capable of exhibiting a high total cohesive force. Therefore, for example, the filter member 4 can be manufactured without limiting the direction in which the ventilation filter medium 2 (or the PTFE stretched porous membrane 1) is incorporated into the filter member 4.
- Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 5 are an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, an epoxy-based pressure-sensitive adhesive, and a rubber-based pressure-sensitive adhesive.
- an acrylic pressure-sensitive adhesive or a silicone-based pressure-sensitive adhesive particularly a silicone-based pressure-sensitive adhesive, which has excellent heat resistance.
- the pressure-sensitive adhesive layer 5 may be a base-less double-sided pressure-sensitive adhesive tape.
- the pressure-sensitive adhesive may be a curable pressure-sensitive adhesive such as a phenol resin, an epoxy resin, a urea resin, a polyurethane resin, a melamine resin, or a polyester resin.
- the outer circumference of the ventilation filter medium 2 and the outer circumference of the pressure-sensitive adhesive layer 5 are aligned with each other when viewed perpendicularly to the main surface of the ventilation filter medium 2. Further, the shape of the pressure-sensitive adhesive layer 5 is a shape corresponding to the peripheral edge portion of the ventilation filter medium 2 when viewed perpendicularly to the main surface of the ventilation filter medium 2.
- the region of the ventilation filter medium 2 to which the pressure-sensitive adhesive layer 5 is not bonded can be used as the ventilation region of the filter member 4A.
- the shape of the pressure-sensitive adhesive layer 5 is not limited to the above example.
- the area of the ventilation area is, for example, 40 mm 2 or less.
- the filter member 4 having an area of the ventilation region in the range is suitable for arrangement on an object having an opening having a small diameter, for example.
- the lower limit of the area of the ventilation region is, for example, 0.008 mm 2 or more.
- the area of the ventilation region may be a larger range depending on the type of the object on which the filter member 4 is arranged.
- the filter member 4 (4B) of FIG. 7 further includes a base material layer 6 arranged on one side of the ventilation filter medium 2, and the ventilation filter material 2 and the adhesive layer 5 are interposed via the base material layer 6. It has the same configuration as the filter member 4A except that it is joined.
- the base material layer 6 can improve the strength and handleability of the filter member 4, and can suppress damage to the ventilation filter medium 2 during handling and placement on an object.
- Examples of materials constituting the base material layer 6 include polyolefins such as PE and PP, polyesters such as PET, silicone resins, polycarbonates, polyimides, polyamideimides, polyphenylene sulfides, polyetheretherketones (PEEK), polyvinyl chlorides, and fluorocarbons. Resin and metals such as aluminum and stainless steel.
- Examples of fluororesins are PTFE, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene copolymer (ETFE). .
- the material constituting the base material layer 6 is not limited to the above example.
- the outer circumference of the ventilation filter medium 2 and the outer circumference of the base material layer 6 are aligned with each other when viewed perpendicularly to the main surface of the ventilation filter medium 2.
- the shape of the base material layer 6 is a shape corresponding to the peripheral edge portion of the ventilation filter medium 2 when viewed perpendicularly to the main surface of the ventilation filter medium 2.
- the region of the ventilation filter medium 2 to which the base material layer 6 is not bonded can be used as the ventilation region of the filter member 4B.
- the shape of the base material layer 6 is not limited to the above example.
- the aeration filter medium 2 and the base material layer 6 may be bonded by an adhesive or an adhesive, or may be bonded by welding such as heat welding and ultrasonic welding.
- the aeration filter medium 2 and the base material layer 6 may be bonded by an adhesive layer.
- the pressure-sensitive adhesive layer may have the same structure as the pressure-sensitive adhesive layer 5.
- the base material layer 6 and the pressure-sensitive adhesive layer 5 may be a base material and a pressure-sensitive adhesive layer of a single-sided adhesive tape or a double-sided adhesive tape, respectively.
- the filter member 4 (4C) of FIG. 8 has the same configuration as the filter member 4B except that the base material layer 6 (6B) arranged on the other side of the ventilation filter medium 2 is further provided.
- the ventilation filter medium 2 is sandwiched by a pair of base material layers 6 (6A, 6B). With this sandwiching structure, the strength and handleability of the filter member 4 can be further improved.
- the filter member 4 (4D) of FIG. 9 is further provided with a tab film 7, and is a filter except that the base material layer 6 (6B) and the tab film 7 are bonded via the adhesive layer 5 (5B). It has the same configuration as the member 4C.
- the tab film 7 has tabs protruding outward from the outer circumference of the base material layer 6B when viewed perpendicular to the main surface of the base material layer 6B.
- the filter member 4D can be handled and placed on the surface of an object by gripping the tab.
- the tab film 7 is usually removed when the filter member 4D is used.
- the tab film 7 may be made of the same material as the material constituting the base material layer 6.
- the tab film 7 is usually removed by grasping and lifting the tab. At this time, a strong force is applied to the ventilation filter medium 2 in the lifting direction.
- the filter member 4 can be supplied by, for example, a sheet for supplying members.
- FIG. 10 shows an example of a member supply assembly which is a mode of supplying the filter member 4 by the sheet.
- the member supply assembly 10 of FIG. 10 includes a sheet 9 for supplying members and a filter member 4 (4D) arranged on the sheet 9.
- the filter member 4 is arranged on the sheet 9 via the pressure-sensitive adhesive layer 5 (5A). According to the member supply assembly 10, for example, the filter member 4 can be efficiently supplied to the step of arranging the filter member 4 on the surface of the object.
- a plurality of filter members 4 may be arranged on the sheet 9.
- the filter member 4 may be arranged on the sheet 9 via an adhesive layer provided on the arrangement surface of the filter member 4 on the sheet 9.
- the pressure-sensitive adhesive layer on the arrangement surface is preferably weakly adhesive.
- the filter member 4 can be lifted from the sheet 9 and peeled off without damaging the film 1.
- Examples of materials constituting the sheet 9 are paper, metal, resin, and composite materials thereof.
- the metal is, for example, stainless steel and aluminum.
- the resin is, for example, polyester such as PET and polyolefin such as PE and PP.
- the material constituting the sheet 9 is not limited to the above example.
- the sheet 9 may be single-wafer-shaped or strip-shaped. When the sheet 9 is strip-shaped, the member supply assembly 10 may be wound to form a wound body.
- An example of an object on which the filter member 4 is arranged is a housing of an electronic device and a housing of an electrical component for a vehicle.
- the filter member 4 can be arranged on the outer surface and / or the inner surface of the housing.
- the opening may be a vent and / or a sound passage provided in the housing.
- electronic devices are wearable devices such as smart watches and wristbands; various cameras including action cameras and security cameras; information and communication devices such as mobile phones, smartphones and tablets; virtual reality (VR) devices; augmented reality (AR) ) Equipment; and sensor equipment.
- vehicle electrical components are lamps and ECUs.
- the object is not limited to the above example.
- the foreign matter that is prevented from passing by the arrangement of the filter member 4 is, for example, particles such as dust and liquid water such as water droplets.
- the size of the evaluation region 21 was 280 ⁇ m ⁇ 280 ⁇ m in the direction parallel to the film surface and 140 ⁇ m in the thickness direction (including the entire film to be evaluated in the thickness direction). 1601 continuous transmission images for constructing a three-dimensional image of the evaluation region were acquired. The binarization on the above image analysis software was based on the Li method. Further, the separation between the node and the fibril was carried out by determining the PTFE body having a volume of 500 voxel (21.44 ⁇ m 3 ) or less as the fibril and adjusting the threshold value in the noise removal command.
- Water pressure resistance (limit water pressure resistance)
- the water pressure resistance was determined by the above-mentioned method in accordance with the provisions of the water resistance test B method (high water pressure method) specified in JIS L1092.
- the air permeability in the thickness direction was determined by the above-mentioned method in accordance with the provisions of the air permeability measurement method A specified in JIS L1096.
- Total cohesive force The total cohesive force was determined by the following method. First, the PTFE stretched porous membrane to be measured was cut out into a rectangle (length 150 mm ⁇ width 20 mm). Next, two double-sided adhesive tapes (manufactured by Nitto Denko, No. 5610) having the same shape as the PTFE stretched porous film were prepared. Next, each double-sided adhesive tape was attached to one surface and the other surface of the PTFE stretched porous film so that the outer circumferences were aligned with each other.
- a length (50 mm) was secured at the other end of the PET film in the longitudinal direction so that the chuck of the tensile tester could stably grip the PET film.
- a crimping roller with a load of 19.6 N was reciprocated once so that a crimping force was applied in the thickness direction of the laminate of PET film / double-sided adhesive tape / PTFE stretched porous film / double-sided adhesive tape / PET film.
- the test pieces were left at room temperature for 12 hours and then at 60 ° C. for 1 hour to obtain test pieces.
- a test piece S MD cut out with the long sides matching the MD direction of the film and a test piece S TD cut out with the long sides matching the TD direction of the film. Prepared.
- a tensile tester (A & D Co., Ltd., Tensilon universal tester RTF) was prepared. Hold the test piece horizontally and bend the free end of one PET film upward to the upper chuck of the tensile tester, and bend the free end of the other PET film downward to the lower chuck of the tensile tester. I installed each. Next, under the conditions of a measurement temperature of 23 ⁇ 5 ° C., a measurement humidity of 50 ⁇ 5% RH, and a tensile speed of 300 mm / min, the free end of one PET film faces upward and the free end of the other PET film faces downward.
- a tensile tensile test (T-shaped peeling test) was carried out to cause cohesive failure in the PTFE stretched porous film.
- T-shaped peeling test was carried out to cause cohesive failure in the PTFE stretched porous film.
- the average value was taken as the peeling cohesive force (unit: N / 20 mm) of the PTFE stretched porous membrane. From the test piece S MD , the peeling force in the MD direction was determined. From the test piece S TD , the peeling force in the TD direction was determined. Next, the total cohesive force was calculated as the product of both peeling cohesive forces.
- Example 1 100 parts by weight of PTFE fine powder (unmodified, standard specific density (SSG) 2.16) and 19.7 parts by weight of an aliphatic hydrocarbon as a liquid lubricant were uniformly mixed to form a PTFE paste.
- the formed PTFE paste was extruded into a sheet at a pressure of 2.5 MPa (25 kg / cm 2 ) using an FT die, and this was further rolled with a pair of metal rolls to adjust the thickness of the strip. (Unrolled, 0.2 mm thick) was obtained.
- the obtained PTFE sheet was heated to remove the liquid lubricant.
- the sheet after stretching A was fired by passing it through a heating furnace kept at 375 ° C. without stretching (firing B).
- the transit time of the heating furnace was set to 17 seconds.
- the sheet after firing B was uniaxially stretched in the width direction in a heating furnace maintained at 330 ° C. (stretching C). The draw ratio was 10 times. Stretching C was carried out by tenter stretching. The area stretch ratio of Example 1 was 35 times. Next, the sheet after stretching C was heat-fixed by passing it through a heating furnace held at 380 ° C. without stretching to obtain a PTFE-stretched porous film.
- Example 2 to 4 A PTFE-stretched porous film of Examples 2 to 4 was obtained in the same manner as in Example 1 except that the conditions of stretching A, firing B, stretching C, and heat fixing were set as the conditions shown in Table 1 below. Table 1 also shows the conditions of Example 1.
- Comparative Example 2 PTFE was obtained in the same manner as in Comparative Example 1 except that SSG 2.19 was used as the PTFE fine powder and the conditions for stretching D, stretching G, and heat fixing were set as shown in Table 2 below. A stretched porous membrane was obtained.
- FIGS. 11A to 16A The SEM observation images of the surface of each PTFE stretched porous membrane are shown in FIGS. 11A to 16A, respectively.
- the SEM observation images of the cross section (cut in the MD direction) in the thickness direction of each PTFE stretched porous film are shown in FIGS. 11B to 16B, respectively.
- the evaluation base material used for the SEM observation is shown together with the PTFE stretched porous membrane.
- FIGS. 11A to 16B in the PTFE-stretched porous membrane of the example, unlike the membrane of the comparative example, a node extending not only in the in-plane direction but also in the thickness direction of the membrane was formed.
- the average length L M of the nodes in the PTFE stretched porous film of Example was larger than the film of Comparative Example.
- the number N of nodes of the PTFE-stretched porous membrane of the example was smaller than that of the membrane of the comparative example.
- the average value of the node angle ⁇ in the PTFE stretched porous membrane of the example is larger than that of the membrane of the comparative example, in other words, the nodes of the PTFE stretched porous membrane of the example are in an upright state in the thickness direction of the membrane. Was there.
- Table 4 in the PTFE stretched porous membrane of the example both the air permeability in the thickness direction and the total cohesive force were achieved at a high level as compared with the membrane of the comparative example.
- FIG. 17 shows the relationship between the air permeability in the thickness direction and the total cohesive force in the PTFE-stretched porous membranes of Examples and Comparative Examples.
- the PTFE-stretched porous membrane of the example had higher air permeability and total cohesive force than those of the comparative example.
- the PTFE stretched porous membrane of the example represents the air permeability in the thickness direction as P T and the total cohesive force as C T, and satisfies the formula C T ⁇ ⁇ 0.33 ⁇ P T +3.67. It was.
- the PTFE-stretched porous membranes of Examples 2 and 3 satisfied the formula C T ⁇ ⁇ 0.57 ⁇ P T +6.14.
- the PTFE stretched porous membrane of the present invention can be used, for example, as an aeration filter medium.
Abstract
Description
複数のノードと、前記複数のノードを接続するフィブリルと、を備えるノード/フィブリル構造を有するPTFE延伸多孔質膜であって、
前記延伸多孔質膜の厚さに対する、前記厚さ方向の前記複数のノードの平均長さの比率が10%以上であるPTFE延伸多孔質膜、
を提供する。
厚さ方向の通気性を有すると共に、当該方向への異物の透過を防ぐ通気濾材であって、
上記本発明のPTFE延伸多孔質膜を備える通気濾材、
を提供する。
厚さ方向の通気性を有すると共に、当該方向への異物の透過を防ぐ通気濾材を備え、
前記通気濾材が、上記本発明の通気濾材であるフィルター部材、
を提供する。
気孔率(%)={1-(質量[g]/(厚さ[cm]×面積[cm2]×真密度[g/cm3]))}×100
未焼成のPTFEシートを、PTFEの融点未満の延伸温度にて所定の方向に延伸し(延伸A);
延伸Aを経たシートを、PTFEの融点以上の温度にて焼成し(焼成B);
焼成Bを経たシートを、PTFEの融点未満の延伸温度にて上記所定の方向とは異なる方向にさらに延伸する(延伸C)。
延伸Aでは、未焼成のPTFEシートをPTFEの融点(結晶の融点である343℃)未満の延伸温度にて所定の方向に延伸する。延伸Aは、例えば、延伸Aを実施する温度(延伸温度)に制御された加熱炉内で実施できる。延伸Aは、例えば、ロール延伸により実施できる。ただし、延伸Aを実施する方法は、上記例に限定されない。
焼成Bでは、延伸Aを経たシートをPTFEの融点以上の温度にて焼成する。焼成Bは、例えば、焼成Bを実施する温度(焼成温度)に制御された加熱炉内で実施できる。
延伸Cでは、焼成Bを経たシートをPTFEの融点未満の延伸温度にて上記所定の方向とは異なる方向にさらに延伸する。延伸Cは、例えば、延伸Cを実施する温度(延伸温度)に制御された加熱炉内で実施できる。延伸Cは、例えば、テンター延伸により実施できる。ただし、延伸Cを実施する方法は、上記例に限定されない。
本発明の通気濾材の一例を図4に示す。図4の通気濾材2(2A)は、PTFE延伸多孔質膜1を備える。本発明の通気濾材の別の一例を図5に示す。図5の通気濾材2(2B)は、通気性支持材3を更に備える。通気性支持材3は、PTFE延伸多孔質膜に積層されている。通気性支持材3により、通気濾材2としての強度及び取扱性を向上できる。
本発明のフィルター部材の一例を図6に示す。図6のフィルター部材4(4A)は、厚さ方向の通気性を有すると共に、当該方向への異物の透過を防ぐ通気濾材として、上記説明した通気濾材2を備える。フィルター部材4Aは、例えば、開口を有する面を持つ対象物の当該面に配置されて、当該開口における異物の透過を防ぎながら当該開口を介した通気を確保する部材である。この場合、フィルター部材4Aは、通常、対象物の開口を通気濾材2が覆うように配置される。
目付は、上述した方法により求めた。
ノードの平均長さLM、ノードの数N、ノードの体積分率、ノード角度αの平均値及びノードの平均厚さは、上述のように、X線CT装置を用いた3次元画像解析により評価した。X線CT装置には、Zeiss製、Xradia 520 Versaを使用した。画像解析ソフトには、ImageJ(Ver.1.47r)を使用した。X線CTの観察条件は、CuKα線、管電圧60kV、管電流83μA、分解能0.35μm/pixelとした。評価領域21のサイズは、膜面に平行な方向に280μm×280μm及び厚さ方向に140μm(厚さ方向に評価対象の膜の全体を含む)とした。評価領域の3次元画像を構築するための連続透過像は、1601枚取得した。上記画像解析ソフト上での2値化は、Li法に基づいた。また、ノードとフィブリルとの分離は、500voxel(21.44μm3)以下の体積を有するPTFE体をフィブリルと判断して、ノイズ除去コマンドにおける閾値調整により実施した。
上記X線CTにより構築した3次元画像からY-Z平面の像を任意の10枚抽出し、抽出した平面の像から求めた厚さの平均値をPTFE延伸多孔質膜の厚さとした。
耐水圧は、JIS L1092に定められた耐水度試験B法(高水圧法)の規定に準拠して、上述した方法により求めた。
気孔率は、上述した方法により求めた。
厚さ方向の通気度(フラジール通気度)は、JIS L1096に定められた通気性測定A法の規定に準拠して、上述した方法により求めた。
全凝集力は、以下の方法により求めた。最初に、測定対象であるPTFE延伸多孔質膜を長方形(長さ150mm×幅20mm)に切り出した。次に、PTFE延伸多孔質膜と同一の形状を有する両面粘着テープ(日東電工製、No.5610)を2枚準備した。次に、各両面粘着テープを、それぞれ、PTFE延伸多孔質膜の一方の面及び他方の面に外周を一致させて貼り合わせた。次に、長さ200mm×幅20mmの長方形のPETフィルム(東レ製、ルミラーS10#25、厚さ25μm)を2枚準備し、各PETフィルムを、それぞれ、PTFE延伸多孔質膜の一方の面及び他方の面に上記両面粘着テープにより貼り合わせた。PETフィルムの貼り合わせは、各PETフィルムの幅方向の両端部がPTFE延伸多孔質膜の幅方向の両端部と一致し、かつ各PETフィルムの長手方向の一方の端部が、PTFE延伸多孔質膜の長手方向の一方の端部と一致するように実施した。これにより、PETフィルムの長手方向の他方の端部に、引張試験機のチャックがPETフィルムを安定して掴める長さ(50mm)が確保された。次に、PETフィルム/両面粘着テープ/PTFE延伸多孔質膜/両面粘着テープ/PETフィルムの積層体の厚さ方向に圧着力が加わるように、荷重19.6Nの圧着ローラを1往復させた。その後、引張試験を開始するまでに、室温で12時間及び続いて60℃で1時間放置して、試験片を得た。なお、同一のPTFE延伸多孔質膜について、当該膜のMD方向に長辺を一致させて切り出した試験片SMDと、当該膜のTD方向に長辺を一致させて切り出した試験片STDとを準備した。
PTFEファインパウダー(未変性、標準比重(SSG)2.16)100重量部と、液状潤滑剤として脂肪族炭化水素19.7重量部とを均一に混合してPTFEペーストを形成した。次に、形成したPTFEペーストを、FTダイスを用いて2.5MPa(25kg/cm2)の圧力でシート状に押出成形し、これを一対の金属ロールによりさらに圧延して、厚みを整えた帯状のPTFEシート(未延伸、厚さ0.2mm)を得た。次に、得られたPTFEシートを加熱して、液状潤滑剤を除去した。
延伸A、焼成B、延伸C及び熱固定の条件を以下の表1に示す条件とした以外は、実施例1と同様にして、実施例2~4のPTFE延伸多孔質膜を得た。なお、表1には、実施例1の条件も併せて示す。
実施例1と同様に準備した未延伸のPTFEシートを連続的に供給しながら、375℃に保持した加熱炉内にて、長手方向に一軸延伸した(延伸D)。延伸倍率は4.5倍とした。延伸Dは、ロール延伸により実施し、ひずみ速度は1.94/分とした。
PTFEファインパウダーとしてSSG2.19のものを使用すると共に、延伸D、延伸G及び熱固定の条件を以下の表2に示す条件とした以外は、比較例1と同様にして、比較例2のPTFE延伸多孔質膜を得た。
Claims (10)
- 複数のノードと、前記複数のノードを接続するフィブリルと、を備えるノード/フィブリル構造を有するポリテトラフルオロエチレン延伸多孔質膜であって、
前記延伸多孔質膜の厚さに対する、前記厚さ方向の前記複数のノードの平均長さの比率が10%以上であるポリテトラフルオロエチレン延伸多孔質膜。 - サイズ280μm×280μmの上面及び下面を有すると共に、前記延伸多孔質膜の一方の膜面及び他方の膜面に前記上面及び前記下面がそれぞれ位置する直方体状の領域を想定したときに、当該領域に含まれる厚さ1μmあたりの前記ノードの数が4以下である請求項1に記載のポリテトラフルオロエチレン延伸多孔質膜。
- 前記延伸多孔質膜における前記ノードの平均厚さが0.5~5μmである請求項1又は2に記載のポリテトラフルオロエチレン延伸多孔質膜。
- 厚さ方向の通気度が、フラジール通気度により表示して、4cm3/(秒・cm2)以上である請求項1~3のいずれかに記載のポリテトラフルオロエチレン延伸多孔質膜。
- 面内の第1方向への引きはがし凝集力と、前記第1方向と面内において直交する第2方向への引きはがし凝集力との積により示される全凝集力が、1.9(N/20mm)2以上である請求項1~4のいずれかに記載のポリテトラフルオロエチレン延伸多孔質膜。
- 目付が7.0g/m2以上である請求項1~5のいずれかに記載のポリテトラフルオロエチレン延伸多孔質膜。
- 厚さが30μm以上である請求項1~6のいずれかに記載のポリテトラフルオロエチレン延伸多孔質膜。
- 厚さ方向の通気性を有すると共に、当該方向への異物の透過を防ぐ通気濾材であって、
請求項1~7のいずれかに記載のポリテトラフルオロエチレン延伸多孔質膜を備える通気濾材。 - 前記ポリテトラフルオロエチレン延伸多孔質膜に積層されている通気性支持材を更に備える請求項8に記載の通気濾材。
- 厚さ方向の通気性を有すると共に、当該方向への異物の透過を防ぐ通気濾材を備え、
前記通気濾材が、請求項8又は9に記載の通気濾材であるフィルター部材。
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DE112020005956.1T DE112020005956T5 (de) | 2019-12-05 | 2020-12-03 | Gestreckte poröse polytetrafluorethylen-membran, luftdurchlässiges medium, bei dem diese verwendet wird, und filterelement, bei dem diese verwendet wird |
US17/781,913 US20230019449A1 (en) | 2019-12-05 | 2020-12-03 | Stretched porous polytetrafluoroethylene membrane, air-permeable medium using the same, and filter member using the same |
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2020
- 2020-12-03 DE DE112020005956.1T patent/DE112020005956T5/de active Pending
- 2020-12-03 KR KR1020227018245A patent/KR20220104724A/ko unknown
- 2020-12-03 JP JP2021562732A patent/JPWO2021112198A1/ja active Pending
- 2020-12-03 US US17/781,913 patent/US20230019449A1/en active Pending
- 2020-12-03 WO PCT/JP2020/045119 patent/WO2021112198A1/ja active Application Filing
- 2020-12-03 CN CN202080084023.9A patent/CN114761101B/zh active Active
- 2020-12-04 TW TW109142858A patent/TW202128272A/zh unknown
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JPS59145124A (ja) * | 1982-09-10 | 1984-08-20 | ダブリユ・エル・ゴア・アンド・アソシエイツ,インコ−ポレイテイド | 多孔質材料 |
JP2007523247A (ja) * | 2004-02-19 | 2007-08-16 | ゴア エンタープライズ ホールディングス,インコーポレイティド | 低摩擦性耐磨耗性材料及びそれから製造された物品 |
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Also Published As
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KR20220104724A (ko) | 2022-07-26 |
DE112020005956T5 (de) | 2022-09-22 |
CN114761101B (zh) | 2024-03-26 |
CN114761101A (zh) | 2022-07-15 |
US20230019449A1 (en) | 2023-01-19 |
JPWO2021112198A1 (ja) | 2021-06-10 |
TW202128272A (zh) | 2021-08-01 |
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