Diaphragm valve

Abstract

To provide a diaphragm valve exhibiting excellent durability.SOLUTION: A diaphragm valve is so constituted that: a diaphragm member comprising a laminate structure having at least a first layer having one side surface with which a medical solution is brought into contact, and comprising a perfluorocarbon resin, and a second layer arranged at the other side of the first layer with which the medical solution is not brought into contact, and comprising a polyvinylidene fluoride resin is mounted in the peripheral edge part on a mounted part formed in a valve body; and Rockwell hardness (HR15y): HR-1 of the valve body, and Rockwell hardness (HR15y): HR-2 of the laminate part comprising the first layer and the second layer in the diaphragm member satisfy the following formula (1): [HR-1]-[HR-2]≥90.0 ...(1)SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a diaphragm valve, and particularly to a diaphragm valve that is advantageously used in transport piping lines for corrosive liquids such as brine, hydrochloric acid, concentrated sulfuric acid, and hypochlorous acid.

Background Art

[0002] As a type of valve that blocks or allows the flow of a liquid flowing through a flow path, a diaphragm valve that controls the flow of a liquid by pressing or separating a flexible diaphragm against a valve seat of a valve body is widely known. Among such diaphragm valves, particularly in diaphragm valves used in transport piping lines for corrosive liquids such as brine, hydrochloric acid, concentrated sulfuric acid, and hypochlorous acid, high durability is required for the diaphragm, and thus various types have been proposed and used conventionally.

[0003] For example, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2020-153519), as a diaphragm attached to the diaphragm valve disclosed therein, a first layer containing a fluororesin disposed on the flow path side and a second layer containing an elastic resin disposed on the side opposite to the flow path of the first layer are provided, and the thickness a of a predetermined portion in the first layer and the thickness b of the second layer satisfy 0.15 ≤ a / b ≤ 0.375, and such has been proposed. Further, in Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2020-153393), as a diaphragm of a diaphragm unit used in a diaphragm valve, a first layer containing a fluororesin adhered to a second layer containing an elastic resin has been proposed.

[0004] However, upon detailed examination of the diaphragms disclosed in Patent Document 1 and Patent Document 2, the inventors found that while these diaphragms exhibit a certain degree of durability, they inherently possess various problems. Specifically, when a diaphragm valve equipped with a diaphragm disclosed in Patent Document 1 or Patent Document 2 is used in a piping line for transporting corrosive liquids, in the case of the diaphragm disclosed in Patent Document 1, when leakage of corrosive liquid is observed from the diaphragm after long-term use, it is extremely difficult to determine the cause, such as whether this is due to erosion of the first layer by the corrosive liquid or deterioration of the second layer by corrosive gases generated from the corrosive liquid. Furthermore, in the case of a diaphragm valve equipped with a diaphragm disclosed in Patent Document 2, it was found that repeated pressing and separating of the diaphragm against the valve seat of the valve can cause the adhesive between the first and second layers to peel off, potentially resulting in a failure to enjoy long-term watertight performance. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-153519 [Patent Document 2] Japanese Patent Publication No. 2020-153393 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Under these circumstances, the inventors diligently conducted research to further improve the durability of diaphragms and valve bodies in which they are installed. They discovered that diaphragm valves in which the Rockwell hardness of the diaphragm and valve body satisfy a predetermined relationship exhibit excellent durability, and thus completed the present invention. In other words, the present invention was made against this background, and its objective is to provide a diaphragm valve that exhibits excellent durability by ensuring good chemical resistance to chemical solutions, effectively suppressing or preventing the permeation of corrosive gases generated from such chemical solutions, thereby avoiding corrosion caused by such corrosive gases, and also effectively suppressing or preventing wear on the diaphragm component caused by repeated operation over a long period of time. [Means for solving the problem]

[0007] Furthermore, in order to solve the aforementioned problems, the present invention can be suitably implemented in various embodiments as listed below. It should be understood that the embodiments or technical features of the present invention are not limited in any way to those described below, and can be recognized based on the inventive concept that can be grasped from the description in the specification.

[0008] (1) A diaphragm valve comprising a valve body and a diaphragm member which is pressed against or separated from the valve seat of the valve body to shut off or allow the flow of a chemical in the chemical flow path, The diaphragm member is mounted on the mounting portion formed on the valve body, The valve body is made from an injection-molded product of a resin composition mainly composed of polyvinylidene fluoride resin. The diaphragm member is composed of a laminated structure having at least a first layer made of a perfluorocarbon resin, on one side of which the chemical solution comes into contact, and a second layer made of a polyvinylidene fluoride resin, which is located on the other side of the first layer that does not come into contact with the chemical solution. The Rockwell hardness (HR15y):HR-1 of the valve body and the Rockwell hardness (HR15y):HR-2 of the laminated portion consisting of the first and second layers of the diaphragm member satisfy the following formula (1): A diaphragm valve characterized by the following features. [HR-1]-[HR-2]≧90.0 (1) (2) The mounting portion of the valve body has a non-curved portion a, while the peripheral edge of the diaphragm member has a non-curved portion b, and the diaphragm member is mounted to the valve body with these non-curved portions a and b facing each other. The Rockwell hardness (HR15y): HR-1 is measured on the non-curved portion a that constitutes the mounting portion of the valve body. The Rockwell hardness (HR15y):HR-2 is measured for the laminated portion consisting of the first and second layers in the non-curved portion b that constitutes the peripheral edge of the diaphragm member. The diaphragm valve according to embodiment (1) described above, characterized in that (3) The diaphragm valve according to embodiment (1) or embodiment (2), wherein the injection molded product constituting the valve body is an injection molded product of a resin composition mainly composed of polyvinylidene fluoride resin and containing flavantron as a crystal nucleating agent in a mass of 200 to 4000 ppm. (4) The diaphragm valve according to embodiment (3), wherein the Rockwell hardness (HR15y):HR-1 is 110.0 or higher. (5) The diaphragm valve according to embodiment (1) or embodiment (2), wherein the perfluorocarbon resin constituting the first layer in the diaphragm member is polytetrafluoroethylene. (6) The diaphragm valve according to embodiment (1) or embodiment (2), wherein the diaphragm member is configured as a laminated structure in which a third layer made of a rubber elastic material is further arranged on the side of the second layer opposite to the first layer. (7) The diaphragm valve according to embodiment (6), wherein the rubber elastic body providing the third layer is ethylene-propylene rubber. (8) The diaphragm valve according to embodiment (1) or embodiment (2), wherein the chemical solution is a liquid that generates corrosive gas. Suitable examples of such a liquid that generates corrosive gas include hydrochloric acid, concentrated sulfuric acid, hypochlorous acid, etc., which are circulated in the piping during the electrolysis process. [Effects of the Invention]

[0009] Thus, in a diaphragm valve according to the present invention, a predetermined diaphragm member (specifically, a laminated structure having at least a first layer made of a perfluorocarbon resin and a second layer made of a polyvinylidene fluoride resin arranged on the side of the first layer that does not come into contact with the chemical solution) is mounted on the mounting portion of the valve body, and the Rockwell hardness (HR15y): HR-1 of the valve body and the Rockwell hardness (HR15y): HR-2 of the laminated portion of the diaphragm member consisting of the first and second layers are configured to satisfy a predetermined relationship. With this configuration, 1) the first layer of the diaphragm member provides excellent corrosion resistance, and 2) the second layer of the same member effectively blocks the permeation of corrosive gases, thereby advantageously preventing deterioration of other components (for example, a third layer made of rubber elastic material, or metal parts surrounding the diaphragm member) caused by such corrosive gases. Furthermore, 3) because HR-1 and HR-2 satisfy a predetermined relationship, wear in the diaphragm member caused by repeated operation over a long period of time is effectively suppressed or prevented, and thus the diaphragm valve of the present invention exhibits excellent durability. [Brief explanation of the drawing]

[0010] [Figure 1] This is a longitudinal cross-sectional diagram illustrating an example of a diaphragm valve according to the present invention. [Figure 2]Figure 1 is an explanatory diagram showing the diaphragm removed from the diaphragm valve, where (a) is a cross-sectional explanatory diagram showing the undeformed state of the diaphragm in the closed state of the diaphragm valve, and (b) is a cross-sectional explanatory diagram showing the state in which the diaphragm has been deformed in the open state of the diaphragm valve. [Figure 3] This is a cross-sectional explanatory diagram showing a partially enlarged view of the diaphragm valve shown in Figure 1. [Modes for carrying out the invention]

[0011] To further clarify the present invention, embodiments of the present invention will be described in detail below with reference to the drawings.

[0012] First, Figure 1 shows an example of a diaphragm valve to which the present invention is applied. In this example, the diaphragm valve 10 has an inlet passage 14 and an outlet passage 16, and a partition wall 18 located between the passages 14 and 16 and curving the passages, and the tip surface (upper surface) of the partition wall 18 serves as a valve seat 20 and has a valve body 12. A bonnet 22 is attached to cover an opening formed above the partition wall 18 of the valve body 12, and a spindle 24 supported by this bonnet 22 is movable vertically (axially) by rotating a handle 26. In addition, a diaphragm 40, which has a circular or substantially rectangular planar shape and is attached to a compressor 28 fixed to the lower end of the spindle 24 and is movable in the vertical direction, is sandwiched at its periphery between a mounting portion 30 formed on the opening periphery of the valve body 12 and the lower end of the bonnet 22, thereby closing the opening of the valve body 12. In this configuration, the diaphragm valve 10 is pressed against or separated from the valve seat 20 by the vertical movement of the spindle 24, and consequently the vertical movement of the compressor 28, thereby blocking or allowing the flow of liquid through the passages 14 and 16 to pass.

[0013] Furthermore, in a diaphragm valve 10 with such a configuration, the diaphragm 40 that blocks or connects the inlet passage 14 and the outlet passage 16 exhibits the configuration shown in Figure 2. Specifically, the diaphragm 40 is composed of a laminated structure comprising: 1) a first layer 42 made of a perfluorocarbon resin, on one side surface (the bottom surface in the figure) that comes into contact with the chemical solution flowing through the passages (14, 16); 2) a second layer 44 made of a polyvinylidene fluoride resin, located on the other side (the top side in the figure) of the first layer 42 that does not come into contact with the chemical solution; and 3) a third layer 46 made of a predetermined rubber elastic material, located on the opposite side of the second layer 44 from the first layer 42. The first layer 42 is composed of a thick central portion and a thin portion that is thinner than the central portion (thick portion), located to cover the periphery of the central portion (thick portion). The base of a connecting fitting 48 for connecting to the compressor 28 is embedded in the thickened portion of the first layer 42, and the connecting fitting 48 protrudes upward in a manner that penetrates the central part of the third layer 46 through the central opening of the second layer 44. Furthermore, in the diaphragm 40, a peripheral ridge 50 is formed along the periphery of the lower surface which is the wetted side of the first layer 42, and a linear ridge 52 extending in the diametrical direction through the center of the first layer 42 is integrally provided. The peripheral ridges 50 are for improving the sealing performance between the diaphragm 40 and the opening peripheral edge of the valve body 12 when the diaphragm 40 is squeezed between the mounting portion 30 of the valve body 12 and the lower end of the bonnet 22, and the linear ridges 52 are for improving the fluid barrier performance between the diaphragm 40 and the valve seat 20 of the valve body 12 when the diaphragm 40 is deformed and moved downward by the downward operation of the compressor 28 and pressed against the valve seat 20.

[0014] In addition, in the present embodiment, the first layer 42, the second layer 44, and the third layer 46 are laminated in a form formed into a predetermined shape, and the laminated structure is configured as a molded body having a certain shape. In a situation where it is not lifted by the spindle 24, it is configured to exhibit a form as shown in FIG. 2(a). That is, the diaphragm 40 shown in FIG. 2(a) shows a state assembled in its molded form. Usually, in such a form, it is assembled to the diaphragm valve 10, and the central portion of the diaphragm 40 is pressed by the compressor 28, thereby being brought into pressure contact with the valve seat 20. Thus, the flow of liquid between the inlet passage 14 and the outlet passage 16 can be effectively blocked. Further, when the compressor 28 is moved upward by the axial movement of the spindle 24, the diaphragm 40 is deformed in an upwardly curved (projecting) form, being pulled upward as shown in FIG. 2(b). And in such a form, the diaphragm 40 is not brought into pressure contact with the valve seat 20 as shown in FIG. 1, but is separated at a predetermined interval. Therefore, a predetermined liquid can flow between the inlet passage 14 and the outlet passage 16.

[0015] And in the diaphragm valve 10 according to the present invention, the Rockwell hardness (HR15y): HR-1 of the valve body 12 and the Rockwell hardness (HR15y): HR-2 of the laminated portion composed of the first layer 42 and the second layer 44 in the diaphragm 40 are configured to satisfy the following formula (1), and this is where the major technical feature of the present invention lies. Thus, the diaphragm valve 10 is composed of the valve body 12 and the diaphragm 40 such that the respective Rockwell hardnesses (HR-1, HR-2) satisfy the relationship of the following formula (1). Therefore, wear of the diaphragm 40 due to repeated operation over a long period of time, more specifically, wear occurring at the peripheral edge portion of the diaphragm 40 facing the mounted portion 30 of the valve body 12, which is caused by repeated pressing and separation of the diaphragm 40 against the valve seat 20 of the valve body 12, can be more effectively suppressed or prevented. Furthermore, in combination with the characteristic configuration of the diaphragm 40, the diaphragm valve 10 of the present invention exhibits extremely excellent durability compared to conventional ones. If the following formula (1) is not satisfied, specifically, if the value obtained by subtracting HR-2 from HR-1 is less than 90, the diaphragm member (diaphragm 40) does not exhibit sufficient wear resistance, and as a result, there is a risk that the diaphragm valve may not exhibit sufficient durability either. [HR-1] - [HR-2] ≥ 90.0 ···(1)

[0016] Here, the Rockwell hardness (HR15y): HR-1 of the valve body (12) in the present invention and the Rockwell hardness (HR15y): HR-2 of the laminated portion composed of the first layer (42) and the second layer (44) in the diaphragm member (diaphragm 40) are both measured according to the method specified in JIS-K-7202-2:2001 "Plastics - Methods for Determining Hardness - Part 2: Rockwell Hardness" using HR15y as the hardness scale.

[0017] Furthermore, regarding the measurement of the two types of Rockwell hardness (HR15y) [HR-1, HR-2] mentioned above, the measurement location is not limited to any part of the valve body or diaphragm member where measurement is possible. For example, Figure 3 is an enlarged cross-sectional explanatory diagram showing a part of the diaphragm valve 10 shown in Figure 1. The mounting portion 30 of the valve body 12 is composed of a portion where the thickness in the height direction of the diaphragm valve 10 (up and down direction in Figures 1 and 3) is substantially uniform and the surface is not curved (non-curved portion). Similarly, the peripheral edge of the diaphragm 40 is also composed of a portion where the thickness in the height direction of the diaphragm valve 10 is substantially uniform and the surface is not curved (non-curved portion). In a diaphragm valve 10 equipped with such a valve body 12 and diaphragm 40, it is preferable that 1) HR-1 is measured on the non-curved portion constituting the mounting portion 30 of the valve body 12, and 2) HR-2 is measured on the laminated portion consisting of a first layer 42 and a second layer 44 in the non-curved portion constituting the peripheral edge of the diaphragm 40, with the wetted side of the first layer 42 (the lower surface in the figure) being used as the measuring surface.

[0018] Furthermore, since the measurement results for HR-1 and HR-2 may change depending on the thickness, it is preferable to measure multiple times by changing the position in which the hardness scale (indenter) is pressed, and to use the average value of the results as HR-1 and HR-2. Also, as mentioned above, peripheral ridges 50 are formed on the periphery of the diaphragm 40, but HR-2 is measured while avoiding these peripheral ridges 50. Moreover, in the case of a diaphragm 40 according to this embodiment, where the diaphragm is composed of a laminated structure consisting of a third layer 46 in addition to the first layer 42 and the second layer 44, HR-2 may be measured on the laminated portion consisting of the two layers (first layer 42 and second layer 44) before the formation of the third layer 46, or after removing the third layer 46 from the laminated structure according to a known method, the wetted surface of the first layer 42 (bottom surface in the figure) may be used as the measurement surface.

[0019] Incidentally, the valve body 12 is an injection-molded product obtained using a resin composition mainly composed of polyvinylidene fluoride resin. As for the polyvinylidene fluoride resin used in manufacturing the valve body 12, any conventionally known polyvinylidene fluoride resin can be used, as long as it is possible to manufacture a molded product that satisfies a predetermined relationship between the two Rockwell hardnesses (HR-1, HR-2) described above, according to an injection molding method in which molding conditions (molding temperature, molding pressure) are appropriately selected. In this invention, the polyvinylidene fluoride resin includes not only homopolymers of vinylidene fluoride but also copolymers that contain vinylidene fluoride units as structural units.

[0020] In the manufacture of the valve body 12 constituting the diaphragm valve 10 of the present invention, a resin composition mainly composed of the polyvinylidene fluoride resin described above is used, and it is advantageous that flavanthrone is added to such a resin composition as a crystal nucleating agent. In injection molded products obtained using a resin composition containing flavanthrone, the effects of the present invention, such as the uniform fineness of crystal particles and the suppression of blister (protrusion) formation, can be enjoyed more advantageously. Furthermore, since the addition of flavanthrone makes the crystal particles in the injection molded product uniformly fine, it is thought that the addition of flavanthrone also contributes to reducing changes in product dimensions after long-term use. Flavanthrone is a compound that has been conventionally known as a yellow vat dye, and as shown in the following formula (I), tautomers exist. [ka]

[0021] Furthermore, when using the above-mentioned Flavantron in the manufacture of the valve body 12, it is preferable that the amount of Flavantron used in the resin composition, which mainly consists of polyvinylidene fluoride resin, be such that the content ratio is 200 to 4000 ppm by mass, preferably 500 to 2000 ppm. If the content ratio of Flavantron in the resin composition is less than 200 ppm, it may not be possible to enjoy the advantageous effect of blending Flavantron. On the other hand, even if an amount of Flavantron exceeding 4000 ppm is used, no significant improvement proportional to the amount used is observed, and only the yellowness of the injection molded product increases. Therefore, from the viewpoint of cost-effectiveness, it is not advisable to use an amount of Flavantron exceeding 4000 ppm.

[0022] Furthermore, in addition to the Flavantron described above, the resin composition used in manufacturing the valve body 12 may also contain various conventionally known additives, such as fillers and reinforcing agents, as long as they do not hinder the objectives of the present invention.

[0023] When manufacturing the valve body 12 using the resin composition mainly composed of polyvinylidene fluoride resin as described above, according to the injection molding method, the resin composition (molding material) is prepared in the same manner as in the past. For example, when using flavantron together with polyvinylidene fluoride resin, the resin composition that serves as the molding material is prepared by following one of the following methods: 1) mixing the polyvinylidene fluoride resins using a mixer such as a V-type blender, ribbon blender, or Henschel mixer; 2) melt-kneading them using a kneader such as an extruder, mixing roll, Banbury mixer, or kneader; 3) mixing and kneading them in combination with the aforementioned mixer and kneader; or 4) melt-kneading the polyvinylidene fluoride resin and flavantron using the aforementioned kneader to produce a masterbatch, and then mixing this masterbatch with the polyvinylidene fluoride resin. Furthermore, when manufacturing the valve body 12 using only polyvinylidene fluoride resin, it is not necessarily required to employ the resin composition (molding material) preparation process described above.

[0024] Then, by performing injection molding using the prepared resin composition (molding material) in accordance with a conventionally known injection molding method, the valve body 12 constituting the diaphragm valve 10 according to the present invention is obtained. Various molding conditions when performing such injection molding, such as molding temperature (cylinder temperature) and molding pressure (injection pressure), are appropriately determined according to the type of polyvinylidene fluoride resin used, the shape and size of the target injection molded product (resin product), etc., so that the Rockwell hardness (HR15y):HR-1 measured on the obtained injection molded product and the Rockwell hardness (HR15y):HR-2 of the diaphragm member 40 satisfy the relationship of the present invention (the relationship of formula (1) above). For example, as the molding temperature (cylinder temperature), a temperature in the range of 170 to 230°C is preferably adopted, and a temperature in the range of 200 to 230°C is preferably adopted. Also, as the molding pressure (injection pressure), a pressure in the range of 35 to 65 MPa is preferably set. At molding pressures (injection pressures) exceeding 65 MPa, crystallization is difficult to achieve uniformly, and there is a risk of reduced strength of the molded product due to residual stress, etc. On the other hand, at molding pressures (injection pressures) below 35 MPa, there is a risk of insufficient filling of the molding material within the mold, and problems such as molding defects such as flow marks appearing on the surface of the molded product are more likely to occur.

[0025] Incidentally, the first layer 42 in the diaphragm 40 that comes into contact with the chemical solution is generally formed to have a thickness of about 0.80 to 4.50 mm in its thin-walled portion. The material constituting this first layer 32 is appropriately selected from various conventionally known perfluorocarbon resins, such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, polychlorotrifluoroethylene polymer, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin, in order to ensure corrosion resistance to the chemical solution. In the present invention, however, polytetrafluoroethylene (PTFE) is particularly advantageous.

[0026] Furthermore, the third layer 46 backing the first layer 42 is intended to effectively transmit the operation of the compressor 28 to the first layer 42, and is generally formed to a thickness of about 2 to 15 mm. The material of the third layer 46 is not particularly limited, and any known rubber-elastic material can be used as appropriate. Examples include ethylene-propylene rubber such as EPDM (ethylene-propylene-diene rubber), acrylic rubber, fluororubber, butyl rubber, chloroprene rubber, etc. Among these, ethylene-propylene rubber, especially EPDM, is preferably used.

[0027] Furthermore, the second layer 44 interposed between the first layer 42 and the third layer 46 is intended to block corrosive gases that permeate the thin portion of the first layer 42, thereby preventing deterioration of the third layer 46, and is composed of a polyvinylidene fluoride resin. In the present invention, polyvinylidene fluoride (homopolymer) is advantageously used as the polyvinylidene fluoride resin, but it is also possible to use known polyvinylidene fluoride copolymers obtained by copolymerizing polyvinylidene fluoride with halogenated comonomers such as hexafluoropropylene, tetrafluoroethylene, or chlorotrifluoroethylene. In addition, by using a polyvinylidene fluoride resin having a tensile modulus of 1000 MPa or less, it is possible to effectively prevent the induction of microcracks in the second layer 44 and maintain its low gas permeability for a long period of time. The lower limit of such a tensile modulus is generally around 650 MPa. Furthermore, the tensile modulus is determined in accordance with JIS-K-7161:2014.

[0028] Furthermore, the polyvinylidene fluoride resin constituting the second layer 44 preferably has a melting point of 130 to 170°C, more preferably 140 to 160°C, which allows the second layer 44 to exhibit advantageous characteristics as an intermediate sheet layer. If the melting point of the polyvinylidene fluoride resin is lower than 130°C, the gas permeability increases, and if it is lower than 140°C, the fluidity increases, which can easily cause problems such as variations in product dimensions during the formation of the second layer 44. If the melting point exceeds 160°C, microcracks are more likely to occur in the second layer 44, and if it exceeds 170°C, the elastic modulus increases, which can cause problems such as increased valve operating torque.

[0029] Furthermore, polyvinylidene fluoride resins having the above-mentioned physical properties are available on the market, and commercially available resins from companies such as Kureha Corporation and Solvay Japan Ltd. can be used as appropriate. In the present invention, the thickness of the second layer 44 is preferably set to 0.50 to 1.00 mm. If it is less than 0.50 mm, there is a risk that corrosive gases that permeate the thin-walled portion of the first layer 42 cannot be sufficiently blocked, and on the other hand, if the thickness exceeds 1.00 mm, the performance of blocking corrosive gases does not improve in proportion to the thickness, so it would only increase manufacturing costs unnecessarily and would not be a good idea. In addition, in the example diaphragm 30, the second layer 44 is formed in such a way that it does not exist on the thick-walled central portion of the first layer 42, with an opening provided in the center. Even if such an opening is provided in the second layer 44, the presence of the thick first layer 32 and the lower flange portion of the connecting fitting 48 in the thick portion will sufficiently suppress or prevent the permeation of corrosive gases. However, depending on the concentration of the corrosive gas, the second layer 44 may be shaped to cover up to the top of the thick portion in order to protect metal parts such as the spindle.

[0030] Although typical embodiments of the present invention have been described in detail above, these are merely illustrative examples, and it should be understood that the present invention is not to be interpreted in any way as being limited by such specific descriptions of embodiments.

[0031] For example, the first layer 42, the second layer 44, and the third layer 46 that constitute the diaphragm 40 in the diaphragm valve 10 are molded separately and then laminated to form a three-layer laminate. However, it is also possible to use a laminate structure in which the first layer 42, the second layer 44, and the third layer 46 are fixed and integrated with each other.

[0032] Furthermore, it is possible to use at least one of the first layer 42, the second layer 44, and the third layer 46 in a flat, sheet-like form without molding it into a predetermined product shape.

[0033] Furthermore, the third layer 46 can be composed solely of a rubber elastic material, or it can be constructed by mixing reinforcing fibers into the rubber elastic material or by interposing a reinforcing fiber layer.

[0034] In addition, regarding the drive system of the compressor 28 in the diaphragm valve 10 as illustrated, instead of the manual rotation operation of the handle 26 as illustrated, a pneumatic drive system using air pressure or an electric drive system using a motor or the like can also be adopted, and any known drive system will be appropriately adopted. [Examples]

[0035] The present invention will be further clarified by showing some embodiments below, but it goes without saying that the present invention is not limited in any way by the description of such embodiments. Furthermore, it should be understood that, in addition to the embodiments below and the specific descriptions above, various changes, modifications, and improvements can be made to the present invention based on the knowledge of those skilled in the art, as long as they do not depart from the spirit of the present invention.

[0036] -Preparation of resin composition- First, a predetermined amount of polyvinylidene fluoride resin (manufactured by Kureha Corporation, product name: Kureha KF Polymer #1000, melting point: 173°C) and an amount of flavantron such that the total amount of the polyvinylidene fluoride resin and flavantron combined constitutes 5000 ppm by mass were prepared. After mixing the polyvinylidene fluoride resin and flavantron, the mixture was melt-kneaded and extruded using an extruder at 230°C to produce flavantron-containing resin pellets (diameter: approximately 2 mm x length: 3 mm). On the other hand, the polyvinylidene fluoride resin alone was melted and extruded using an extruder to produce resin pellets (diameter: approximately 2 mm x length: 3 mm).

[0037] Then, resin composition a, to be used as a molding material, was prepared by adding 20 parts by mass of flavantron-containing resin pellets to 80 parts by mass of resin pellets and mixing. In this resin composition, the flavantron content is 1000 ppm by mass. On the other hand, resin composition b consisted only of the above resin pellets.

[0038] -Manufacturing of valve bodies for diaphragm valves- Using resin composition a prepared as described above, injection molding was performed under the conditions of molding temperature (cylinder temperature): 220°C and molding pressure (injection pressure): 48 MPa to produce valve bodies for diaphragm valves exhibiting the structure shown in Figure 1, with a bore diameter of 100 mm (valve body I) and a bore diameter of 65 mm (valve body II). Furthermore, using resin composition b, injection molding was performed under the conditions of molding temperature (cylinder temperature): 220°C and molding pressure (injection pressure): 48 MPa to produce a valve body for diaphragm valves exhibiting the structure shown in Figure 1, with a bore diameter of 65 mm (valve body III).

[0039] -Rockwell hardness (HR15y): HR-1 measurement- The Rockwell hardness (HR15y):HR-1 was measured using the outer surface of the non-curved portion of the diaphragm mounting area of ​​the manufactured valve body as the measurement surface (see Figure 3), according to the method specified in JIS-K-7202-2:2001 "Plastics - Methods for determining hardness - Part 2: Rockwell hardness". This measurement was performed at five arbitrary locations on the non-curved portion, and the average value obtained from each measurement was calculated. This average value was defined as the "Rockwell hardness (HR15y):HR-1 of the valve body". The obtained HR-1 values ​​are shown in Table 1 below.

[0040] -Diaphragm fabrication- Diaphragms consisting of two layers, a first layer and a third layer (Examples 1, 2, and 3), and diaphragms consisting of three layers, a first layer, a second layer, and a third layer, were fabricated, exhibiting the external shapes shown in Figures 1 and 2. In fabrication, polytetrafluoroethylene (PTFE) was used as the material for forming the first layer, polyvinylidene fluoride (PVDF, tensile modulus: 800 MPa, melting point: 150°C) was used as the material for forming the second layer, and EPDM was used as the material for forming the third layer. Furthermore, the average thickness of each layer in the fabricated diaphragms was as follows: 1) For a diaphragm used in a valve body with a bore diameter of 100 mm (Example 1), the first layer was approximately 3.5 mm, the second layer approximately 0.7 mm, and the third layer approximately 10.8 mm; and 2) For diaphragms used in a valve body with a bore diameter of 65 mm (Example 2, Comparative Examples 1 to 3), the first layer was approximately 1.2 mm, the second layer approximately 0.7 mm (however, the diaphragms related to Comparative Examples 2 and 3 did not have a second layer), and the third layer approximately 7.1 mm.

[0041] -Rockwell hardness (HR15y): HR-2 measurement- In the preparation of each of the diaphragms described above, for the diaphragms of Example 1, Example 2, and Comparative Example 3, a laminate consisting of a first layer and a second layer was formed, and for the diaphragms of Comparative Example 1 and Comparative Example 2, the first layer was formed first. The outer surface of the first layer in the non-curved portion constituting the mounting part of each diaphragm was used as the measurement surface (see Figure 3), and the Rockwell hardness (HR15y):HR-2 was measured according to the method specified in JIS-K-7202-2:2001 "Plastics - Methods for determining hardness - Part 2: Rockwell hardness". Such measurements were performed at five arbitrary locations in the non-curved portion, excluding the portion where peripheral ridges were formed. The average value of the results obtained from each measurement was calculated, and this average value was defined as the "Rockwell hardness (HR15y):HR-2 of the diaphragm". The obtained HR-2 values ​​are shown in Table 1 below.

[0042] The valve body and diaphragm obtained as described above were combined as shown in Table 1 below to manufacture the diaphragm valve shown in Figure 1, and the following tests were performed on this diaphragm valve.

[0043] -Seal performance evaluation test- First, the diaphragm was placed in 35% hydrochloric acid, with only the side of the diaphragm where the first layer was exposed, and left to stand at 50°C for 28 days (chemical resistance test). Next, each diaphragm that had undergone the chemical resistance test was mounted on the valve body shown in Table 1 below to form a diaphragm valve. This diaphragm valve was then immersed in water, and with the diaphragm in the open state (allowing fluid flow), air was introduced from the inlet side, and the presence or absence of air leakage (presence or absence of bubbles) from the diaphragm was visually checked. If no air leakage (bubbles) was observed, it was evaluated as ○ (pass), and if air leakage (bubbles) was observed, it was evaluated as × (fail). The results of each evaluation are shown in the "Seal Performance Evaluation Test" column of Table 1 below.

[0044] -Opening and closing torque test- Valve opening and closing tests were performed on each diaphragm valve. These tests were repeatedly conducted under the following conditions: opening / closing cycle pressure: 0.4 MPa, 1 minute of opening operation, and 1 minute of closing operation. After 10,000 opening and closing operations, the valve was disassembled and the condition of the second layer (a layer made of polyvinylidene fluoride) in the diaphragm (or the condition of the third layer for diaphragms without a second layer) was visually inspected. A "○" was given if no damage was observed, and a "×" was given if damage was observed. The results of each evaluation are shown in the "Opening / Closing Torque Test" column of Table 1 below.

[0045] [Table 1]

[0046] As is clear from the results in Table 1, in the diaphragm valve according to the present invention, the first layer made of PTFE provides good corrosion resistance, the second layer made of PVDF effectively blocks the permeation of corrosive gases, and furthermore, because HR-1 and HR-2 are configured to satisfy a predetermined relationship (the value obtained by subtracting HR-2 from HR-1 is 90.0 or more), the occurrence of damage due to repeated operation over a long period of time can be effectively suppressed or prevented, and thus it is recognized that the diaphragm valve exhibits extremely excellent durability. [Explanation of symbols]

[0047] 10 Diaphragm valve 12 Valve body 14 Inlet channel 16 Outlet channel 18 partition wall 20 valve seat 22 Bonnet 24 Spindle 26 Handle 28 Compressor 30 Mounted part 40 Diaphragm 42 First layer 44 Second layer 46 Third layer 48 Connecting fittings 50 Peripheral projections 52 Linear projections

Claims

1. A diaphragm valve comprising a valve body and a diaphragm member that is pressed against or separated from the valve seat of the valve body to shut off or allow the flow of a chemical in the chemical flow path, The diaphragm member is mounted on the mounting portion formed on the valve body, The valve body is made from an injection-molded product of a resin composition mainly composed of polyvinylidene fluoride resin. The diaphragm member is composed of a laminated structure having at least a first layer made of a perfluorocarbon resin, on one side of which the chemical solution comes into contact, and a second layer made of a polyvinylidene fluoride resin, which is located on the other side of the first layer that does not come into contact with the chemical solution. The Rockwell hardness (HR15y): HR-1 of the valve body and the Rockwell hardness (HR15y): HR-2 of the laminated portion consisting of the first and second layers of the diaphragm member satisfy the following formula (1): A diaphragm valve characterized by the following features. [HR-1]-[HR-2]≧90.0...(1)

2. The mounting portion of the valve body has a non-curved portion a, while the peripheral edge of the diaphragm member has a non-curved portion b, and the diaphragm member is mounted to the valve body with these non-curved portions a and b facing each other. The Rockwell hardness (HR15y): HR-1 is measured on the non-curved portion a that constitutes the mounting portion of the valve body. The Rockwell hardness (HR15y): HR-2 is measured for the laminated portion consisting of the first and second layers in the non-curved portion b that constitutes the peripheral edge of the diaphragm member. The diaphragm valve according to feature 1.

3. The diaphragm valve according to claim 1 or claim 2, wherein the injection-molded product constituting the valve body is an injection-molded product of a resin composition mainly composed of polyvinylidene fluoride resin and containing flavantron as a crystal nucleating agent in a mass of 200 to 4000 ppm.

4. The diaphragm valve according to claim 3, wherein the Rockwell hardness (HR15y):HR-1 is 110.0 or greater.

5. The diaphragm valve according to claim 1 or claim 2, wherein the perfluorocarbon resin constituting the first layer in the diaphragm member is polytetrafluoroethylene.

6. The diaphragm valve according to claim 1 or claim 2, wherein the diaphragm member is configured as a laminated structure in which a third layer made of a rubber elastic material is further arranged on the side of the second layer opposite to the first layer.

7. The diaphragm valve according to claim 6, wherein the rubber elastic material providing the third layer is ethylene-propylene rubber.

8. The diaphragm valve according to claim 1 or claim 2, wherein the chemical solution is a liquid that generates corrosive gas.

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