Method for manufacturing a diaphragm, diaphragm for a valve, and diaphragm valve equipped therewith

Abstract

To provide a diaphragm for a valve, which has high resistance against repeated bending and can suppress occurrence of particles.SOLUTION: A diaphragm 15 for a valve comprises a valve body part 15a having a sealing surface 15c for contacting and sealing a valve seat, and a membrane part 15b extending outward from the valve body part 15a and supporting the valve body part 15a. A method for manufacturing the diaphragm 15 for a valve comprises molding a semi-finished product using perfluoroalkoxyalkane as a raw material, and cutting the semi-finished product, wherein the raw material is selected so that the specific gravity is less than 2.135 and the opening / closing durability test result of the diaphragm 15 is 55000 times or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a diaphragm suitable for valves used in various industries such as chemical plants, semiconductor manufacturing fields, liquid crystal manufacturing fields, food fields, etc. More specifically, it relates to a diaphragm that suppresses the generation of particles, a method for manufacturing the same, and a diaphragm valve provided with such a diaphragm.

Background Art

[0002] In a diaphragm valve, an inflow-side flow path and an outflow-side flow path communicate with a valve chamber provided in the central portion of a valve body. A diaphragm that isolates the valve chamber and the internal space of a drive unit housing is sandwiched between the valve body and a drive unit housing attached to the upper portion of the valve body. By connecting the diaphragm to the lower end of a stem driven by a drive mechanism disposed within the internal space of the drive unit housing, a valve body supported by the diaphragm is pressed against and separated from a valve seat provided within the valve chamber, thereby generally opening and closing the space between the inflow-side flow path and the outflow-side flow path. Further, in chemical plants, semiconductor manufacturing fields, liquid crystal manufacturing fields, food fields, etc., since fluids with strong corrosiveness or fluids requiring contamination prevention are handled, fluororesin materials having excellent chemical resistance and contamination resistance are widely used for components that come into contact with fluids in diaphragm valves.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In fields requiring high levels of cleanliness, particles generated within diaphragm valves can pose a problem. For example, in the semiconductor wafer manufacturing process, contaminants such as particles, various metals, and polymer compounds are generated, and if these remain on or adhere to the semiconductor wafer, they significantly affect its quality. Therefore, in the semiconductor wafer manufacturing process, semiconductor wafers are cleaned using cleaning solutions. However, if particles are generated within the diaphragm valve used in the piping that supplies the cleaning solution, and cleaning solution containing these particles is discharged from the diaphragm valve and used to clean the semiconductor wafer, sufficient cleaning cannot be performed, resulting in a decrease in the cleanliness of the semiconductor wafer. Therefore, it is desirable to suppress the generation of particles in diaphragm valves, and in particular, to suppress the generation of particles from the diaphragm, which is in contact with the liquid and is also a moving part.

[0005] Typical fluororesins used in diaphragms include polytetrafluoroethylene (PTFE) and perfluoroalkoxyalkanes (PFA), which are copolymers of tetrafluoroethylene (TFE) and perfluoroalkyl vinyl ether (PAVE). However, PFA is known to suppress the generation of particles as described above more easily than PTFE, and therefore, it is preferable to form the diaphragm, especially the valve seat contact portion where particles are likely to be generated, from PFA.

[0006] Incidentally, the fluidity and mechanical properties of PFA (polycrystalline fiber) change depending on its molecular structure. Furthermore, as mentioned above, the diaphragm used in diaphragm valves includes a valve body that moves toward and away from the valve seat, and a membrane that extends outward from the valve body and supports it. To withstand the repeated bending that occurs when the valve body repeatedly moves toward and away from the valve seat, the membrane needs to be flexible.

[0007] However, PFA, which has a molecular structure that is highly fluid and easy to use in molding processes, has low flexibility and poor resistance to repeated bending. For this reason, for example, Patent Document 1 discloses a fluid control valve having a valve mechanism comprising a valve part having a sealing part that seals the valve seat so that it can move back and forth, and a diaphragm part formed on the opposite side of the sealing part and installed in the valve chamber, in which fluororesin is used for the valve seat and valve body, and a member made of PFA is heat-fused to the valve seat and the sealing part of the valve, so that parts that are prone to particle generation due to contact and separation are formed from PFA, and the diaphragm part, i.e., the membrane part, in which flexibility and resistance to repeated bending are required is formed from fluororesin. However, when PTFE is used as the fluororesin mentioned above, the fusion efficiency between PTFE and PFA used in the valve seat and the sealing part of the valve is not good, so there are concerns about durability. Furthermore, since the diaphragm part is made of PTFE, there are concerns about particle generation due to repeated bending. Furthermore, Patent Document 2 discloses a diaphragm in which a thin film portion, which is difficult to form by injection molding, is formed by rolling from a first type of PFA material that has low fluidity but high flexibility, and then a columnar portion is formed on the film portion by injection molding from a second type of PFA material that has high fluidity, and the columnar portion and the film portion are directly joined together. However, in order to manufacture such a diaphragm, both rolling equipment and injection molding equipment are required, which leads to the problem of increased costs.

[0008] Therefore, the object of the present invention is to solve the problems of the prior art and provide a valve diaphragm that has high resistance to repeated bending and can suppress the generation of particles. [Means for solving the problem]

[0009] In view of the above objectives, the present invention, in a first aspect, is a method for manufacturing a valve diaphragm comprising a valve body having a sealing surface for contacting and sealing a valve seat, and a membrane extending outward from the valve body and supporting the valve body, comprising the steps of: using a perfluoroalkoxyalkane as a raw material, injecting the raw material into a mold to form a semi-finished product by injection molding, and machining the semi-finished product to form at least the membrane, In the cutting process described above, the semi-finished product is cut such that at least the mold transfer surface remains on the sealing surface. The aforementioned raw materials provide a method for manufacturing a diaphragm selected such that the melt flow rate measured at a load of 5 kg and a measurement temperature of 372 ± 0.1 °C is 3 g / 10 min or less.

[0012] Furthermore, the aforementioned raw materials are Furthermore, the opening and closing durability test results for the diaphragm are set to be 55,000 times or more. Preferably selected 。

[0013] In the above-described method for manufacturing a diaphragm, the raw materials may be further selected so that their specific gravity is less than 2.135.

[0014] Furthermore, in a second aspect of the present invention, a valve diaphragm comprising a valve body having a sealing surface for contacting and sealing a valve seat, and a membrane extending outward from the valve body and supporting the valve body, wherein the valve body and the membrane are formed by injection molding using a perfluoroalkoxyalkane selected as a raw material such that the melt flow rate measured at a load of 5 kg and a measurement temperature of 372 ± 0.1 °C is 3 g / 10 min or less. Furthermore, the sealing surface is a mold transfer surface formed by injecting the raw material into the mold and performing injection molding. We provide a valve diaphragm designed to do so.

[0017] Furthermore, the valve diaphragm is For the valve The diaphragm may be formed from the aforementioned raw materials, such that the diaphragm's opening and closing durability test result is 55,000 cycles or more.

[0019] In one embodiment, the valve body includes a main body having the sealing surface and a smaller diameter portion that is narrower than the main body, with the smaller diameter portion being supported by the membrane portion.

[0020] Further, the film portion may include an annular skirt portion that extends in a direction away from the main body portion from the outer peripheral portion of the tip end portion of the small-diameter portion, a bent portion that is convexly curved in a direction away from the main body portion radially outward from the skirt portion, and a support portion that extends planar radially outward from the outer peripheral edge portion of the bent portion.

[0021] In this case ,before It is preferable that the outer peripheral edge portion of the bent portion extends inclined at an angle in the range of 20° to 40° in a direction away from the seal surface with respect to the support portion toward the valve body portion. Furthermore, it is even more preferable that the diaphragm extends toward the valve body at an angle of 25° to 35° relative to the support portion, away from the sealing surface. The valve diaphragm may be formed from the raw material having a specific gravity of less than 2.135.

[0022] Furthermore, as a third aspect, the present invention A valve body having a first flow path, a second flow path, a valve chamber through which the first flow path and the second flow path communicate, and a valve seat formed around the opening from the first flow path to the valve chamber, provides a diaphragm valve provided with the above-described diaphragm for a valve. In the diaphragm valve described above, it is preferable that the valve body is made of polytetrafluoroethylene. Furthermore, it is preferable that the valve seat is formed by rising from the bottom of the valve chamber around the opening from the first flow path to the valve chamber.

Advantages of the Invention

[0023] According to the present invention, since the diaphragm for a valve is formed of PFA, generation of particles can be suppressed as compared with the case of forming a diaphragm from generally used PTFE. Further, since the diaphragm for a valve is manufactured using PFA having a specific gravity of less than 2.135 and an opening / closing durability test result of 55000 or more, it is possible to secure high repeated bend resistance that can withstand use in a diaphragm valve while suppressing generation of particles by using PFA.

Brief Description of the Drawings

[0024] [Figure 1] It is a broken perspective view showing a diaphragm according to a first embodiment of the present invention. [Figure 2] It is a cross-sectional view of the diaphragm shown in FIG. 1. [Figure 3] It is a longitudinal cross-sectional view showing a diaphragm valve provided with the diaphragm shown in FIG. 1. [Figure 4]This is a longitudinal cross-sectional view showing a diaphragm valve equipped with a diaphragm according to a second embodiment of the present invention. [Figure 5] Figure 4 is a cross-sectional view of the diaphragm according to the second embodiment. [Figure 6] Figure 4 is a cross-sectional view showing the deformation of the diaphragm. [Figure 7] Figure 4 is an enlarged cross-sectional view showing a magnified view of the membrane portion of the second diaphragm. [Modes for carrying out the invention]

[0025] The embodiments of the valve diaphragm according to the present invention will be described below with reference to the drawings, but it goes without saying that the present invention is not limited to the embodiments shown in the drawings. Furthermore, in the following description, "diaphragm" means a valve member having a membrane portion that supports the valve body, and "diaphragm valve" means all valves in general that support the valve body with a membrane portion.

[0026] Figures 1 and 2 show a valve diaphragm 15 according to a first embodiment of the present invention, and Figure 3 shows a diaphragm valve 11 equipped with the valve diaphragm 15.

[0027] First, the overall configuration of the diaphragm valve 11 will be described with reference to Figure 3. The diaphragm valve 11 comprises a valve body 13, a diaphragm 15, and a drive unit 17 that drives the diaphragm 15, with the drive unit 17 mounted on the upper part of the valve body 13.

[0028] The valve body 13 has a valve chamber 19 formed in the upper center, and a first flow path and a second flow path that communicate with the valve chamber 19. In the valve chamber 19, an annular valve seat 21 is formed around the opening from the first flow path to the valve chamber 19, to which the diaphragm 15 moves toward and toward. In the illustrated embodiment, the first flow path is an inlet passage 25 that extends from an inlet 23 formed on one of the opposing sides of the valve body 13 and opens in the center of the bottom of the valve chamber 19, and the second flow path is an outlet passage 29 that extends from an outlet 27 formed on the other of the opposing sides of the valve body 13 and opens on the side of the valve chamber 21, and a raised annular valve seat 21 is formed around the opening from the inlet passage 25 to the valve chamber 19.

[0029] A base plate 53 can be further attached to the lower part of the valve body 13 to facilitate installation.

[0030] As shown in detail in Figures 1 and 2, the diaphragm 15 comprises a valve body portion 15a and a membrane portion 15b extending outward from the valve body portion 15a. In the illustrated embodiment, the valve body portion 15a has a generally cylindrical shape, but it may have other shapes. Also, in the illustrated embodiment, the membrane portion 15b is provided to extend radially outward from the outer circumference of the lower end of the valve body portion 15a, but it may be provided to extend radially outward from the upper end or middle portion of the valve body portion 15a, as long as it is connected to the outer circumference of the valve body portion 15a and can support the valve body portion 15a. Furthermore, a sealing surface 15c is formed at the bottom of the valve body portion 15a, and the diaphragm 15 is supported by the valve body 13 by sandwiching the outer peripheral edge of the membrane portion 15b between the valve body 13 and the drive unit 17, so that the sealing surface 15c is positioned facing the valve seat 21.

[0031] The drive unit 17 comprises a drive unit housing 31 attached to the upper part of the valve body 13 and having an internal space, a stem 35 connected to the diaphragm 15, and a drive mechanism housed in the internal space and driving the stem 35. In this embodiment, a cylinder portion opening toward the valve body 13 is formed as an internal space within the drive unit housing 31, and the drive mechanism consists of a piston 37 slidably housed within the cylinder portion and a coil spring 39 as a biasing member. Furthermore, a diaphragm retainer 41 is fitted into the valve body 13 side opening of the cylinder portion of the drive unit housing 31, so that when the drive unit 17 is attached to the upper part of the valve body 13, the outer peripheral edge of the membrane portion 15b is sandwiched between the upper surface of the area surrounding the upper opening of the valve chamber 19 of the valve body 13 and the bottom surface of the diaphragm retainer 41, thereby supporting the diaphragm 15 on the valve body 13.

[0032] The piston 37 has an outer circumferential surface that is in vertically slidable contact with the inner circumferential surface of the cylinder, dividing the internal space of the cylinder into an upper space 43 enclosed by the upper surface of the piston 37, the inner circumferential wall of the cylinder, and the ceiling surface of the cylinder, and a lower space 45 enclosed by the lower surface of the piston 37, the inner circumferential wall of the cylinder, and the bottom surface of the cylinder (i.e., the upper surface of the diaphragm retainer 41). A stem 35 is connected to the piston 37 so as to extend downward from the piston 37. The stem 35 is slidably inserted into a through hole provided through the diaphragm retainer 41 and extends to the valve chamber 19, with a connecting end 35a at its tip connected to the diaphragm 15 (specifically, the valve body 15a).

[0033] In the diaphragm 15 of the first embodiment shown in Figures 1 to 3, a male thread is formed on the outer circumferential surface of the connecting end 35a of the stem 35, and a female thread is formed on the inner circumferential surface of the connecting hole 51 provided in the upper center of the valve body 15a, and the valve body 15a is connected to the connecting end 35a of the stem 35 by screwing the connecting end 35a into the connecting hole 53. However, the connection between the connecting end 35a of the stem 35 and the valve body 15a is not limited to screwing. For example, an enlarged locking portion may be provided on the connecting end 35a of the stem 35, and the connecting end 35a may be press-fitted into the connecting hole provided in the upper center of the valve body 15a to connect the connecting end 35a and the valve body 15a.

[0034] A first communication port 47 is formed in the upper part of the drive unit housing 31, which communicates with the ceiling surface of the cylinder section that partitions the upper space 43, allowing for the supply and discharge of working fluid (e.g., compressed air) to and from the upper space 43 through the first communication port 47. A second communication port 49 is formed in the side of the drive unit housing 31, which communicates with the bottom of the cylinder section that partitions the lower space 45, allowing for the supply and discharge of working fluid to and from the lower space 45 through the second communication port 49. Furthermore, a coil spring 39 is positioned in a compressed state between the upper part of the drive unit housing 31 (ceiling surface of the cylinder section) and the upper surface of the piston 37.

[0035] With this configuration, under normal conditions when working fluid is not supplied to the first communication port 47 and the second communication port 49, the piston 37 is biased downward toward the valve body 13 by the coil spring 39 and pushed down. Consequently, the valve body portion 15a of the diaphragm 15, which is connected to the piston 37 via the stem 35, is moved downward and pressed against the valve seat 21. By supplying working fluid (e.g., compressed air) to the upper space 43 of the cylinder through the first communication port 47 and applying downward fluid pressure to the upper surface of the piston 37 in a direction that brings it closer to the valve body 13, the force acting from the piston 37 to the valve body portion 15a via the stem 35 can be changed, and the force pressing the valve body portion 15a against the valve seat 21 can be adjusted. As a result of the valve body portion 15a being pressed against the valve seat 21, as shown in Figure 3, the opening from the inlet passage 25 to the valve chamber 19 is closed, and the diaphragm valve 11 is closed. When working fluid is supplied to the second communication port 49 from this state, the working fluid (e.g., compressed air) flows into the lower space 45 of the cylinder section, and an upward fluid pressure acts on the lower surface of the piston 37 in a direction away from the valve body 13. The piston 37 is pushed upward in a direction away from the valve body 13 against the biasing force of the coil spring 39 (and, in some cases, in addition to this, the downward fluid pressure exerted on the piston 37 by the working fluid in the upper space 43). At this time, the working fluid in the upper space 43 of the cylinder section is discharged to the outside through the first communication port 47. As the piston 37 moves upward in a direction away from the valve body 13, the valve body portion 15a of the diaphragm 15, which is connected to the piston 37 via the stem 35, moves upward and separates from the valve seat 21. As a result, the opening from the inflow passage 25 to the valve chamber 19 is opened, and the diaphragm valve 11 becomes open. When the valve is open, the fluid that flows into the inlet passage 25 from the inlet 23 of the diaphragm valve 11 flows out to the outside from the outlet 27 after passing through the valve chamber 19 and the outlet passage 29.

[0036] As described above, the opening and closing of the diaphragm valve 11 causes the valve body 15a of the diaphragm 15 to move toward and away from the valve seat 21, resulting in repeated bending of the membrane portion 15b that supports the valve body 15a. For this reason, the membrane portion 15b of the diaphragm 15 is required to withstand repeated bending.

[0037] The diaphragm 15 according to the first embodiment of the present invention is entirely formed from perfluoroalkoxyalkane (PFA). Compared to polytetrafluoroethylene (PTFE), which is commonly used as a diaphragm material, PFA has a molecular structure that is less likely to generate particles when used as a diaphragm material. Therefore, forming the diaphragm 15 from PFA can suppress the generation of particles. On the other hand, PFA generally has the characteristic of low flexibility. As described above, the diaphragm 15, in particular the membrane portion 15b, is subjected to repeated bending. For this reason, if the diaphragm 15 is formed from a type of PFA with low flexibility, it becomes prone to breakage and its durability decreases. However, in recent years, as described in Japanese Patent Application Publication No. 2017-119750, for example, PFA with a highly flexible molecular structure has been developed and is now available on the market. The lower the crystallinity and the higher the molecular weight of PFA, the higher its resistance to repeated bending, and the higher the molecular weight, the lower its specific gravity. From this, the inventors have found that when the specific gravity is less than 2.135, the opening and closing durability test results improve sharply, and when the specific gravity is less than 2.135 and the opening and closing durability test results are 55,000 cycles or more, it can withstand use as a diaphragm for a diaphragm valve. Therefore, as the PFA used for the diaphragm 15, a PFA with a specific gravity of less than 2.135 and an opening and closing durability test result of 55,000 or more is selected. Alternatively, as the PFA used for the diaphragm 15, a PFA with a specific gravity of less than 2.135 and a flex life value of 180,000 cycles or more may be selected. Preferably, the diaphragm 15 is formed from PFA with a specific gravity of 2.12 or less and an opening and closing durability test result of 1,000,000 cycles or more, or from PFA with a specific gravity of 2.12 or less and a flex life value of 19,000,000 cycles or more.

[0038] Here, the opening and closing durability test was performed by attaching a diaphragm to a diaphragm valve with an opening diameter (i.e., orifice diameter) of 1 / 8 inch from the inlet passage 25 to the valve chamber 19, with the fluid temperature at room temperature, a constant fluid pressure of 0.5 MPa, an opening and closing operating pressure of 0.5 MPa, and an opening and closing stroke (distance traveled by the valve body 15a relative to the valve seat 19 during opening and closing) of 1.1 mm. The test was conducted by repeatedly switching between an ambient temperature of 5°C for 6 hours and 100°C for 6 hours, opening the valve for 1.2 seconds and closing it for 0.8 seconds, and measuring the number of cycles until the diaphragm broke. The flex life value was measured in accordance with JIS P 8115.

[0039] Furthermore, in order to enable the diaphragm 15 to be manufactured by injection molding, it is preferable that the PFA has a melt flow rate (MFR) of 3 g / 10 min or less, measured at a load of 5 kg and a measurement temperature of 372 ± 0.1 °C in accordance with ASTM D1238. When forming the diaphragm 15 from PFA by injection molding, for example, a semi-finished product can be produced by injection molding of the type of PFA described above, and then the diaphragm 15 can be produced by machining parts that are difficult to form by injection molding due to factors such as thinness, such as the film portion 35b. By producing the diaphragm 15 by injection molding, the contact surface with the mold surface of the molded product becomes the mold transfer surface, so the surface roughness is smaller and the smoothness is higher than that of a surface machined by machining. Therefore, by machining a semi-finished product produced by injection molding so that a metal transfer surface remains on the wetted surface, it is possible to improve the smoothness of the wetted surface and suppress the generation of particles. In particular, by manufacturing a diaphragm 15 by machining a semi-finished product made by injection molding so as to leave a metal transfer surface on the sealing surface 15c of the valve body 15a that repeatedly comes into contact with and separates from the valve seat 21, it is possible to prevent a decrease in the surface roughness of the sealing surface 15c due to machining and to increase the smoothness of the sealing surface 15c, thereby reducing friction with the valve seat 21 and suppressing the generation of particles.

[0040] Furthermore, it is preferable that the valve body 13, the drive unit housing 31 of the drive unit 17, the stem 35, and the piston 37 are formed from a fluororesin material to prevent corrosion by the fluid. Examples of fluororesin materials that can be used include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polychlorotrifluoroethylene (PCTFE).

[0041] Next, the operation of the diaphragm valve 11 shown in Figure 3 will be explained.

[0042] Under normal circumstances, when no working fluid (e.g., compressed air) is supplied to the drive unit 17 from the first communication port 47 and the second communication port 49, the piston 37 of the drive unit 17 is biased downward by the coil spring 39 in a direction approaching the valve body 13, i.e., it is pushed down. Along with the piston 37, the valve body 15b is also moved downward via the stem 35. As a result, the sealing surface 15c of the valve body 15a is pressed against the valve seat 21, and the diaphragm valve 11 closes as shown in Figure 3. If you want to increase the sealing thrust, you can supply working fluid to the upper space 43 of the cylinder through the first communication port 47, and in addition to the biasing force by the coil spring 39, apply the fluid pressure of the working fluid flowing into the upper space 43 downward to the upper surface of the piston 37. This changes the force that presses the sealing surface 15c of the valve body 15a against the valve seat 21 via the stem 35, thereby adjusting the force that presses the valve body 15 against the valve seat 21.

[0043] From this state, when the supply of working fluid from the first communication port 47 is stopped and working fluid (for example, compressed air) is supplied to the second communication port 49 of the drive unit 17, the fluid pressure of the working fluid that has flowed into the lower space 45 of the cylinder through the second communication port 49 acts upward on the piston 37 (i.e., away from the valve body 13), and the piston 37 is moved upward, away from the valve body 13, against the biasing force of the coil spring 39 and the fluid pressure of the working fluid in the upper space 43, i.e., pushed up. At this time, the working fluid in the upper space 43 is discharged to the outside through the first communication port 47. As the piston 37 is pushed up, the valve body 15a is also moved upward via the stem 35, and the sealing surface 15c of the valve body 15a separates from the valve seat 21, causing the diaphragm valve 11 to open.

[0044] When the supply of working fluid to the second communication port 49 is stopped, the biasing force of the coil spring 39 again biases and pushes the piston 37 downward, causing the sealing surface 15c of the valve body 15a to press against the valve seat 21, and the valve returns to the closed state.

[0045] Thus, the membrane portion 15 supporting the valve body portion 15a of the diaphragm 15 undergoes repeated bending due to the vertical movement of the valve body portion 15a of the diaphragm 15 accompanying the opening and closing of the diaphragm valve 11 (i.e., the approach and separation of the valve body portion 15a from the valve seat 21). Furthermore, the lower the crystallinity and the higher the molecular weight of PFA, the higher its resistance to repeated bending, and as the molecular weight increases, the specific gravity decreases. The diaphragm 15 is formed from PFA with a low specific gravity of less than 2.135 and an opening and closing durability test result of 55,000 or more, or from PFA with a low specific gravity of less than 2.135 and a flex life value of 180,000 or more, preferably from PFA with a specific gravity of 2.12 or less and an opening and closing durability test result of 1,000,000 or more, or from PFA with a specific gravity of 2.12 or less and a flex life value of 19,000,000 or more. Therefore, the diaphragm 15 has sufficient resistance to repeated bending and sufficient durability can be ensured. Furthermore, when the diaphragm valve 11 is opened and closed, the diaphragm 15's membrane portion 15b moves or bends, causing the valve body portion 15a to be pressed against or separated from the valve seat 21. Therefore, the impact and friction when the valve body portion 15a contacts the valve seat 21, and the repeated bending of the membrane portion 15b, make it easy for particles to be generated from the diaphragm 15. However, the diaphragm 15 is made of PFA, which has a molecular structure that makes it difficult for particles to be generated. Therefore, the diaphragm 15 has the effect of suppressing particle generation compared to when other fluororesin materials such as PTFE are used. In other words, the diaphragm 15 can suppress particles by using PFA while ensuring high resistance to repeated bending that can withstand use in a diaphragm valve.

[0046] The present invention is not limited to the configuration of the diaphragm 15 of the first embodiment. Figure 4 shows a diaphragm 111 equipped with a valve diaphragm 115 according to a second embodiment of the present invention.

[0047] First, the overall configuration of the diaphragm valve 111 will be described with reference to Figure 4. Similar to the diaphragm valve 11, the diaphragm valve 111 comprises a valve body 113, a diaphragm 115, and a drive unit 117 that drives the diaphragm 115, with the drive unit 117 mounted on the upper part of the valve body 113.

[0048] Similar to the case of the diaphragm valve 11, the valve body 113 has a valve chamber 119 formed in the upper center, and a first flow path and a second flow path that communicate with the valve chamber 119. In the valve chamber 119, a raised valve seat 121 is formed around the opening from the first flow path to the valve chamber 119, to which the diaphragm 115 moves toward and away from. In the embodiment shown in Figure 4, the first flow path is an inlet passage 125 that extends from an inlet 123 formed on one of the opposing sides of the valve body 113 and opens in the center of the bottom of the valve chamber 119, and the second flow path is an outlet passage 129 that extends from an outlet 127 formed on the other opposing side of the valve body 113 and opens on the side of the valve chamber 121, and a raised annular valve seat 121 is formed around the opening from the inlet passage 125 to the valve chamber 119.

[0049] As shown in detail in Figure 5, the diaphragm 115 comprises a valve body portion 115a and a membrane portion 115b extending outward from the valve body portion 115a. The valve body portion 115a has a so-called poppet shape, including a main body portion 155 and a smaller diameter portion 157 that is thinner than the main body portion 155. Preferably, the smaller diameter portion 157 has a tapered shape that becomes thinner towards the end (tip) on the drive unit 117 side. The membrane portion 115b is formed to extend outward from the outer circumference of the tip (end on the drive unit 117 side) of the smaller diameter portion 157 of the valve body portion 115a. More specifically, the membrane portion 115b includes an annular skirt portion 159 extending upward toward the drive unit 117 from the outer circumference of the tip (the end on the drive unit 117 side) of the narrow diameter portion 157 of the valve body portion 115a, a bent portion 161 extending radially outward from the upper end of the skirt portion 159 in a convex shape away from the valve body portion 115a, and a support portion 163 extending radially outward from the outer peripheral edge of the bent portion 161.

[0050] The bent portion 161 is the part that supports the valve body 115a to allow vertical movement of the valve body 115a for contacting and separating from the valve seat 112 when the diaphragm valve 111 is opened and closed. The longer the bent portion 161, the gentler the degree of bending relative to the stroke (travel distance) of the valve body 115a when the diaphragm valve 111 is opened and closed, so the stress generated when the valve body 115a moves up and down becomes smaller, and particle generation becomes less likely. On the other hand, the longer the bent portion 161, the more easily the membrane portion 115b of the diaphragm 115 is subjected to a force from the fluid in the direction of pulling the valve body 115a away from the valve seat 121 as fluid pressure. As a result, in order to counteract the fluid pressure received by the membrane portion 115b, it becomes necessary to increase the sealing thrust force, which is the force that presses the valve body 115a against the valve seat 121 by the drive unit 117, and particle generation becomes more likely. Furthermore, as the length of the bent portion 161 increases, the valve chamber 119 also needs to be enlarged, resulting in the disadvantage of an increased overall size of the diaphragm valve 111. Therefore, in order to suppress particle generation while suppressing an increase in the size of the diaphragm valve 111, it is preferable that the length of the bent portion 161 is 1.8 to 2.8 times the travel distance of the valve body portion 115a when the diaphragm valve 111 is opened and closed, i.e., the stroke, and 2.1 to 2.4 times the stroke. If the length of the bent portion 161 is 2.1 times or more the stroke of the valve body portion 115a when the diaphragm valve 111 is opened and closed, the stress generated in the membrane portion 115b of the diaphragm 115 will be reduced. If the length of the bent portion 161 is 2.4 times or less the stroke of the valve body portion 115a when the diaphragm valve 111 is opened and closed, the force exerted on the membrane portion 115b of the diaphragm valve 115 by fluid pressure in the direction that pulls the valve body portion 115a away from the valve seat 121 will be reduced, thereby reducing the sealing thrust. Therefore, if the length of the bent portion 161 is in the range of 2.1 to 2.4 times the stroke of the valve body portion 115a when the diaphragm valve 111 is opened and closed, the effect of suppressing particle generation while suppressing an increase in the size of the diaphragm valve 111 will be particularly enhanced.

[0051] Furthermore, because the valve body 115a has a poppet shape, even if the valve body 115a is placed in a valve chamber 119 of the same size, the gap between the inner surface of the valve chamber 119 and the outer surface of the upper part of the narrow diameter portion 157 of the valve body 115a becomes wider, making it easier to secure the length of the bent portion 161.

[0052] As shown in detail in Figures 5 and 7, the support portion 163 of the diaphragm 115 is composed of an annular first horizontal support portion 163a extending horizontally radially outward (parallel to the sealing surface 115c) from the outer peripheral edge of the bent portion 161, a cylindrical vertical support portion 163b located outside the first horizontal support portion and extending vertically, and an annular second horizontal support portion 163c located outside the vertical support portion and extending horizontally. As shown in Figure 7, the outer peripheral edge of the bent portion 161 on the side of the first horizontal support portion 163a extends inclined from the first horizontal support portion 163a toward the valve body portion 115a at an angle θ away from the sealing surface 115c relative to the first horizontal support portion 163a. ​​The angle θ is in the range of 20° to 40°, and preferably in the range of 25° to 35°. By setting the angle θ to 25° or more, the stress generated in the membrane portion 115b of the diaphragm 115 can be reduced, further enhancing the effect of suppressing particle generation from the diaphragm 115. Also, by setting the angle θ to 35° or less, the angle between both sides of the recess 165 (described later) becomes obtuse, making processing easier and reducing the defect rate. Furthermore, a stepped portion is provided at the upper opening of the valve chamber 119 of the valve body 113. When the protruding portion 131a, which extends from the bottom center of the drive unit housing 131 of the drive unit 117 (described later), is inserted into the upper opening of the valve chamber 119 of the valve body 113, the first horizontal support portion 163a is sandwiched between the tip surface (bottom surface) of the protruding portion 131a of the drive unit housing 131 and the horizontal plane of the stepped portion at the upper opening of the valve chamber 119 of the valve body 113, and the protruding portion 131a of the drive unit housing 131 is outside A vertical support portion 163b is sandwiched between the circumferential surface and the vertical surface of the stepped portion of the upper opening of the valve chamber 119 of the valve body 113. Furthermore, a second horizontal support portion 163c is sandwiched between the bottom surface of the drive unit housing 131, which is located outward from the protrusion 131a, and the upper surface of the area surrounding the upper opening of the valve chamber 119 of the valve body 113. This allows the diaphragm 115 to be fixed and supported to the valve body 113 so that the sealing surface 115c is positioned opposite the valve seat 121.

[0053] Furthermore, as shown in Figure 5, at the connection between the bent portion 161 and the first horizontal support portion 163a, a recess 165 is formed on the side farther from the sealing surface 115c, recessed toward the valve body portion 115a.

[0054] The drive unit 117 comprises a drive unit housing 131 attached to the upper part of the valve body 113 and having an internal space formed inside, a cover member 133 attached to the upper part of the drive unit housing 131, a stem 135 connected to the diaphragm 115, and a drive mechanism housed in the internal space and driving the stem 135. The internal space of the drive unit housing 131 is formed as a cylinder portion that opens upward, and the drive mechanism consists of a piston 137 slidably housed in the cylinder portion and a coil spring 139 as a biasing member. Furthermore, a protrusion 131a is formed protruding from the center of the bottom of the drive unit housing 131, so that when the drive unit 117 is attached to the upper part of the valve body 113, the protrusion 131a of the drive unit housing 131 is inserted into the upper opening of the valve chamber 119 of the valve body 113. As a result, the outer peripheral edge of the membrane portion 115b of the diaphragm 115 is sandwiched between the tip surface (bottom surface) of the protrusion 131a of the drive unit housing 131 and the horizontal surface of the stepped portion of the upper opening of the valve chamber 119 of the valve body 113, between the outer peripheral surface of the protrusion 131a of the drive unit housing 131 and the vertical surface of the stepped portion of the upper opening of the valve chamber 119 of the valve body 113, and between the bottom surface of the drive unit housing 131 and the surrounding area of ​​the upper opening of the valve chamber 119 of the valve body 113, and the diaphragm 115 is fixed and supported to the valve body 113 such that the sealing surface 115c is positioned facing the valve seat 121.

[0055] A guide shaft 167 is connected to the piston 137 so as to extend upward, and a stem 137 is connected so as to extend downward (i.e., toward the valve body 113). The stem 135 is slidably inserted into a through hole provided through the bottom of the drive unit housing 131, and its connecting end 135a is connected to the diaphragm 115 (specifically, its valve body 115a). The outer surface of the piston 137 is in vertically slidable contact with the inner surface of the cylinder, dividing the internal space of the cylinder into an upper space 143 enclosed by the top surface of the piston 137, the inner wall of the cylinder, and the ceiling surface of the cylinder (i.e., the bottom surface of the cover member 133), and a lower space 145 enclosed by the bottom surface of the piston 137, the inner wall of the cylinder, and the bottom surface of the cylinder (i.e., the bottom of the drive unit housing 131). The guide shaft 167 is slidably inserted into a through hole provided through the cover member 133, and is designed to guide the vertical movement of the piston 137 (i.e., the movement of the piston 137 in the direction that brings the sealing surface 115c of the valve body portion 115a, which is connected to the stem 135 extending from the piston 137, toward and away from the valve seat 121).

[0056] The lid member 133 has a first communication port 147 that communicates with the ceiling surface of the cylinder section that partitions the upper space 143, allowing for the supply and discharge of working fluid (e.g., compressed air) to and from the upper space 143 through the first communication port 147. In addition, the side of the drive unit housing 131 has a second communication port 149 that communicates with the bottom of the cylinder section that partitions the lower space 145, allowing for the supply and discharge of working fluid to and from the lower space 145 through the second communication port 149. Furthermore, a coil spring 139 is positioned in a compressed state between the lower surface of the lid member 133 (the ceiling surface of the cylinder section) and the upper surface of the piston 137.

[0057] In the diaphragm 115 of the second embodiment, as shown in detail in Figure 5, an enlarged locking portion is provided at the connecting end 135a of the stem 135, and the connecting end 135a of the stem 135 and the valve body 115a are connected by press-fitting the connecting end (locking portion) 135a of the stem 135 into a connecting hole 151 provided in the upper center of the valve body 115a (specifically its narrow diameter portion 157). However, the connection between the connecting end 135a of the stem 135 and the valve body 115a is not limited to press-fitting. For example, as shown in Figure 6, a female threaded portion may be formed on the inner surface of the connecting hole 151' provided in the connecting end 135a' of the stem 135, and a male threaded portion may be formed on the outer surface of the projection 169 that protrudes from the upper center of the valve body 115a (more specifically, the small diameter portion 157), thereby connecting the connecting end 135a' of the stem 135 and the valve body 115a by screwing the connecting hole 151' of the connecting end 135a' and the projection 169 of the valve body 115a.

[0058] While making the narrow diameter portion 157 thinner would make it easier to secure the length of the bent portion 161, as shown in Figure 5, when the connecting end 135a of the stem 135a is press-fitted into the connecting hole 151 provided in the valve body portion 115a, it is necessary to form the connecting hole 151 in the narrow diameter portion 157 of the valve body portion 115a. Therefore, the diameter of the thinnest part of the narrow diameter portion 157 (hereinafter referred to as the poppet diameter) is 1.8 to 2.5 times the diameter of the opening from the inlet passage 125 to the valve chamber 119 (hereinafter referred to as the orifice diameter), and it is preferable that it be 2.0 to 2.3 times. If the poppet diameter is 2.0 times or more the orifice diameter, the connecting end 135a can be made thicker and its strength increased, making the connecting end 135a less susceptible to deformation, and enabling stable sealing even when the sealing thrust is reduced. Furthermore, by setting the poppet diameter to 2.3 times or less the orifice diameter, as will be described later, the force exerted by the fluid pressure acting on the surface or stepped surface of the main body 155 and the narrow-diameter portion 157, which presses the valve body portion 115a of the diaphragm 115 against the valve seat 121, and the force exerted by the fluid pressure acting on the membrane portion 115b (specifically the bent portion 161) extending from the upper end of the narrow-diameter portion 157, which pulls the membrane portion 115b of the diaphragm 115 away from the valve seat 121, cancel each other out, thereby enhancing the effect of reducing the sealing thrust. Furthermore, as shown in Figure 6, when the connecting hole 151' provided in the connecting end 135a' of the stem 135 and the projection 169 protruding from the valve body 115a are screwed together, the poppet diameter can be made smaller than in the case shown in Figure 5. However, due to the constraints of the screw size, the poppet diameter is 0.8 to 1.5 times the orifice diameter, and it is preferable to make it 1.0 to 1.3 times. If the poppet diameter is 1.0 times or more the orifice diameter, the connecting end 135a' or projection 169 can be made thicker to increase its strength, making it less likely for the connecting end 135a' or projection 169 to deform, and enabling stable sealing even when the sealing thrust is reduced.Furthermore, by setting the poppet diameter to 1.3 times or less the orifice diameter, as will be described later, the force exerted by the fluid pressure acting on the surface or stepped surface of the main body 155 and the narrow-diameter portion 157, which presses the valve body portion 115a of the diaphragm 115 against the valve seat 121, and the force exerted by the fluid pressure acting on the membrane portion 115b (specifically the bent portion 161) extending from the upper end of the narrow-diameter portion 157, which pulls the membrane portion 115b of the diaphragm 115 away from the valve seat 121, can be offset, thereby enhancing the effect of reducing the sealing thrust.

[0059] With the above-described configuration, similar to the diaphragm valve 11 shown in Figure 1, in the diaphragm valve 111 shown in Figure 4, when working fluid is not supplied to the first communication port 147 and the second communication port 149, the piston 137 is biased downward toward the valve body 113 by the coil spring 139 and pushed down. Consequently, the valve body portion 115a of the diaphragm 115, which is connected to the piston 137 via the stem 135, is moved downward and pressed against the valve seat 121. Furthermore, by supplying working fluid (e.g., compressed air) to the upper space 143 of the cylinder through the first communication port 147 and applying downward fluid pressure to the upper surface of the piston 137 in a direction that brings it closer to the valve body 113, the force acting from the piston 137 to the valve body portion 115a via the stem 135 can be changed, and the force pressing the valve body portion 115a against the valve seat 121 can be adjusted. As a result of the valve body 115a being pressed against the valve seat 121, the opening from the inlet passage 125 to the valve chamber 119 is closed, as shown in Figure 4, and the diaphragm valve 111 is closed. When working fluid is supplied to the second communication port 149 from this state, the working fluid flows into the lower space 145 of the cylinder section, and an upward fluid pressure acts on the lower surface of the piston 137 in a direction away from the valve body 113. The piston 137 is pushed up in a direction away from the valve body 113 against the biasing force of the coil spring 139 (and, in some cases, in addition to this, the downward fluid pressure exerted on the piston 137 by the working fluid in the upper space 143). At this time, the working fluid in the upper space 143 of the cylinder section is discharged to the outside through the first communication port 147. As the piston 137 moves upward away from the valve body 113, the valve body portion 115a of the diaphragm 115, which is connected to the piston 137 via the stem 135, moves upward and separates from the valve seat 121. As a result, the opening from the inlet passage 125 to the valve chamber 119 is opened, and the diaphragm valve 111 becomes open. In the open state, the fluid that flows into the inlet passage 125 from the inlet 123 of the diaphragm valve 111 flows out to the outside from the outlet 127 after passing through the valve chamber 119 and the outlet passage 129.

[0060] The diaphragm 115 according to the second embodiment is formed from PFA having a specific gravity of less than 2.135 and an opening / closing durability test result of 55,000 or more, or from PFA having a specific gravity of less than 2.135 and a flex life value of 180,000 or more, similar to the diaphragm 15 according to the first embodiment. Preferably, the diaphragm 115 is formed from PFA having a specific gravity of 2.12 or less and an opening / closing durability test result of 1,000,000 or more, or from PFA having a specific gravity of 2.12 or less and a flex life value of 19,000,000 or more.

[0061] The opening and closing durability test results shall be those measured in accordance with the opening and closing durability test described above. Furthermore, the flex life value shall be measured in accordance with JIS P 8115.

[0062] Furthermore, in order to enable the diaphragm 115 to be manufactured by injection molding, it is preferable that the PFA has a melt flow rate (MFR) of 3 g / 10 min or less, measured at a load of 5 kg and a measurement temperature of 372 ± 0.1 °C in accordance with ASTM D1238. When forming the diaphragm 115 from PFA by injection molding, for example, a semi-finished product can be produced by injection molding of the type of PFA described above, and then the diaphragm 115 can be produced by machining parts that are difficult to form by injection molding, such as the membrane portion 135b. By producing the diaphragm 115 by injection molding, the contact surface with the mold surface becomes the mold transfer surface, resulting in a lower surface roughness and higher smoothness than a surface produced by machining. Therefore, by machining a semi-finished product produced by injection molding so as to leave a metal transfer surface on the wetted surface, it is possible to improve the smoothness of the wetted surface and suppress the generation of particles. In particular, by machining a semi-finished product manufactured by injection molding so as to leave a metal transfer surface on the sealing surface 115c of the valve body 115a that repeatedly comes into contact with and separates from the valve seat 121, the diaphragm is manufactured. This prevents a decrease in the surface roughness of the sealing surface 115c due to machining, and improves the smoothness of the sealing surface 115c. As a result, friction with the valve seat 121 is reduced, and the generation of particles can be suppressed.

[0063] Furthermore, it is preferable that the valve body 113, the drive unit housing 131 of the drive unit 117, the cover member 133, the stem 135, and the piston 137 are formed from a fluororesin material to prevent corrosion by the fluid. Examples of fluororesin materials that can be used include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polychlorotrifluoroethylene (PCTFE).

[0064] The operation and manufacturing method of the diaphragm valve 111 using the diaphragm 115 with this configuration are the same as those of the diaphragm valve 11, so the explanation will be omitted.

[0065] In the diaphragm valve 111, similar to the diaphragm valve 11, the diaphragm 115's oscillating movement (i.e., the approach and separation of the valve body 115a from the valve seat 121) causes repeated bending of the membrane 115 supporting the valve body 115a. Furthermore, the lower the crystallinity and the higher the molecular weight of PFA, the higher its resistance to repeated bending, and as the molecular weight increases, the specific gravity decreases. The diaphragm 115 is formed from PFA with a specific gravity of less than 2.135 and an opening / closing durability test result of 55,000 or more, or from PFA with a specific gravity of less than 2.135 and a flex life value of 180,000 or more, preferably from PFA with a specific gravity of 2.12 or less and an opening / closing durability test result of 1,000,000 or more, or from PFA with a specific gravity of 2.12 or less and a flex life value of 19,000,000 or more. Therefore, the diaphragm 115 has sufficient resistance to repeated bending and can ensure sufficient durability. Furthermore, when the diaphragm valve 111 is opened and closed, the membrane portion 115b of the diaphragm 115 moves or bends, causing the valve body portion 115a to be pressed against or separated from the valve seat 121. Therefore, due to the impact and friction when the valve body portion 115a contacts the valve seat 121, and the repeated bending of the membrane portion 115b, particles are likely to be generated from the diaphragm 115. However, the diaphragm 115 is formed from PFA, which has a molecular structure that is less prone to particle generation. Therefore, the diaphragm 115 has the effect of suppressing particle generation compared to when other fluororesin materials such as PTFE are used. In other words, the diaphragm 115 can suppress particles by using PFA while ensuring high resistance to repeated bending that can withstand use in a diaphragm valve.

[0066] Furthermore, the valve body portion 115a of the diaphragm 115 has a poppet shape in which a narrow-diameter portion 157 is formed between the membrane portion 115b and the main body portion 155 of the valve body portion 115a, which is narrower than the main body portion 155. As a result, the force exerted by the fluid pressure acting on the surface or stepped surface of the main body portion 155 and the narrow-diameter portion 157, which presses the valve body portion 115a of the diaphragm 115 against the valve seat 121, and the force exerted by the fluid pressure acting on the membrane portion 115b (specifically the bent portion 161) extending from the upper end of the narrow-diameter portion 157, which pulls the membrane portion 115b of the diaphragm 115 away from the valve seat 121, cancel each other out. Therefore, the force exerted by the fluid pressure acting on the diaphragm 115 that pulls the diaphragm 115 away from the valve seat 121 can be reduced. As a result, the sealing thrust required to press the valve body portion 115a of the diaphragm against the valve seat 121 can be reduced, thereby lowering the stress generated when the valve body portion 115a is pressed against the valve seat 121 during valve closing, and thus suppressing the generation of particles. In particular, as mentioned above, if the poppet diameter is set to 2.3 times or less the orifice diameter when the connecting hole 151 of the valve body portion 115a and the connecting end 135a are connected by press-fitting, or if the poppet diameter is set to 1.3 times or less the orifice diameter when the projection 169 of the valve body portion 115a and the connecting hole 151' of the connecting end 135a' are connected by screw-fitting, the effect of reducing the sealing thrust by canceling out the force in the direction of pressing the valve body portion 115a of the diaphragm 115 against the valve seat 121 and the force in the direction of pulling the membrane portion 115b of the diaphragm 115 away from the valve seat 121 can be strengthened, thereby improving the effect of suppressing the generation of particles.

[0067] Furthermore, the fact that a recess 165 is provided on the side farther from the sealing surface 115c at the connection between the bent portion 161 and the support portion 163 (specifically the first horizontal support portion 163a), and that the outer peripheral edge of the bent portion 161 on the side of the first horizontal support portion 163a extends inclined from the first horizontal support portion 163a so as to form a 30° angle toward the first horizontal support portion 163a toward the valve body portion 115a, makes it easier for the bent portion 161 to bend relative to the first horizontal support portion 163a, which is sandwiched between the tip surface (bottom surface) of the protruding portion 131a of the drive unit housing 131 and the horizontal plane of the stepped portion of the upper opening of the valve chamber 119 of the valve body 113, thereby making it easier for the valve body portion 115a to move up and down. As a result, the sealing thrust is reduced, which lowers the stress generated when the sealing surface 115c of the valve body 115a is pressed against the valve seat 121 during valve closing, further enhancing the effect of suppressing particle generation.

[0068] The present invention has been described above with reference to the illustrated embodiments, but the present invention is not limited to the illustrated embodiments. For example, in the diaphragm 115 according to the second embodiment, a male threaded portion may be formed on the outer circumference of the connecting end 135a of the stem 135, and a female threaded portion may be formed on the inner surface of the connecting hole 151 provided in the valve body portion 115a, thereby connecting the connecting end 135a of the stem 135 and the valve end portion 115a by screwing. Furthermore, the present invention can be applied to any valve in which the valve body portion is supported by a membrane portion, regardless of its application or function, including suck-back valves with a suck-back function to prevent dripping, needle valves with a flow rate adjustment function, constant flow valves, constant pressure valves and back pressure valves for adjusting pressure, etc. [Explanation of Symbols]

[0069] 11 Diaphragm valve 15 diaphragm 15a Valve body 15b Membrane part 15c sealing surface 111 Diaphragm valve 115 Diaphragm 115a Valve body 115b Membrane part 115c sealing surface 155 Main body 157 Reduced diameter part 159 Skirt section 161 Bending section 163 Support part 163a First horizontal support 163b Vertical support 163c Second horizontal support section 165 recess

Claims

1. A method for manufacturing a valve diaphragm comprising a valve body having a sealing surface for contacting and sealing a valve seat, and a membrane portion extending outward from the valve body and supporting the valve body, A process in which a semi-finished product is formed by injection molding using perfluoroalkoxyalkane as a raw material, by injecting the raw material into a mold, A step of machining the semi-finished product to form at least the film portion, A method for manufacturing a diaphragm, comprising the step of performing the cutting process, wherein the semi-finished product is cut such that at least a mold transfer surface remains on the sealing surface, and the raw materials are selected such that the melt flow rate measured at a load of 5 kg and a measurement temperature of 372 ± 0.1 °C is 3 g / 10 min or less.

2. The method for manufacturing a diaphragm according to claim 1, wherein the raw materials are further selected such that the opening and closing durability test result of the diaphragm is 55,000 times or more.

3. The method for manufacturing a diaphragm according to claim 1, wherein the raw materials are further selected so that their specific gravity is less than 2.

135.

4. A valve diaphragm comprising a valve body having a sealing surface for contacting and sealing a valve seat, and a membrane extending outward from the valve body and supporting the valve body, The valve body and the membrane are formed by injection molding using a perfluoroalkoxyalkane selected as the raw material such that the melt flow rate measured at a load of 5 kg and a measurement temperature of 372 ± 0.1 °C is 3 g / 10 min or less, and the sealing surface is a mold transfer surface formed by injecting the raw material into a mold and performing injection molding.

5. The valve diaphragm according to claim 4, wherein the valve diaphragm is formed from the raw material that has an opening and closing durability test result of 55,000 times or more.

6. The valve diaphragm according to claim 4, wherein the valve body portion includes a main body portion having the sealing surface and a smaller diameter portion that is narrower than the main body portion, and the smaller diameter portion is supported by the membrane portion.

7. The valve diaphragm according to claim 6, wherein the membrane portion includes an annular skirt portion extending away from the main body portion from the outer circumference of the tip of the narrow diameter portion, a bent portion that curves convexly outward radially from the skirt portion away from the main body portion, and a support portion that extends radially outward in a planar manner from the outer edge of the bent portion.

8. The valve diaphragm according to claim 7, wherein the outer peripheral edge of the bent portion extends toward the valve body portion at an angle of 20° to 40° away from the sealing surface with respect to the support portion.

9. The valve diaphragm according to claim 7, wherein the outer peripheral edge of the bent portion extends toward the valve body portion at an angle of 25° to 35° away from the sealing surface with respect to the support portion.

10. The valve diaphragm is formed from the raw material having a specific gravity of less than 2.135, as described in claim 4 and any one of claims 6 to 9.

11. A diaphragm valve comprising a valve body having a first flow path, a second flow path, a valve chamber through which the first flow path and the second flow path communicate, and a valve seat formed around an opening from the first flow path to the valve chamber, and a valve diaphragm according to any one of claims 4 to 10.

12. The diaphragm valve according to claim 11, wherein the valve body is formed of polytetrafluoroethylene.

13. The diaphragm valve according to claim 11, wherein the valve seat is formed by rising from the bottom of the valve chamber around the opening from the first flow path to the valve chamber.

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