Manufacturing method of sealing material
By using high-frequency induction heating and a magnetic mold to join the ends of a fluororesin-coated string-shaped rubber, the method addresses inefficiencies in existing methods, achieving high-quality sealing materials with reduced clamping forces and enhanced resistance properties.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- MITSUBISHI CABLE INDUSTRIES LTD
- Filing Date
- 2024-03-19
- Publication Date
- 2026-05-29
Smart Images
Figure 0007867514000001 
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing a sealing material.
Background Art
[0002] There is known a sealing material in which an annular core material is coated with a fluororesin. For example, Patent Document 1 discloses an O-ring in which an annular core material of heat-resistant rubber is coated with a coating of a fluororesin.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] To coat an annular core material with a fluororesin, there is a method of coating a string-shaped core material with a fluororesin and joining both ends.
[0005] To join the connection part, generally a heating device is used. However, since the connection part of the annular sealing material (for example, an O-ring) is relatively small, there is a problem that it cannot be efficiently heated, for example, by a high-temperature press with a wide heating area.
[0006] The present invention has been made in view of such points, and an object thereof is to enable efficient heating and joining of both ends of a string-shaped rubber.
Means for Solving the Problems
[0007] To achieve the above object, in this invention, only the connection part and its periphery are heated to join the string-shaped rubber into an annular shape.
[0008] Specifically, in the first invention, Prepare a string-like rubber of a predetermined length, covered with a fluororesin with a thickness of 0.20 mm or less. The connecting surfaces of the string-like rubber are joined together. At least the outer circumference of the connecting surface of the string-like rubber is covered with a fluororesin film made of the same material as the fluororesin, The connection portion covered with the aforementioned fluororesin film and only the area surrounding the connection portion are placed in the mold groove of the mold. Close the mold and sandwich the connecting part, The mold is placed inside the high-frequency coil. High-frequency induction heating is performed to melt the fluororesin film and form a fluororesin coating. The system is configured to cool the mold and then remove the annular sealing material.
[0009] According to the above configuration, the mold only needs to be able to sandwich at least the portion covered with the fluororesin film and its surroundings, allowing for miniaturization and easy placement inside the high-frequency coil. Furthermore, since the portion heated by high-frequency induction is limited, the range of effects due to heating is limited compared to heating the entire structure. As a result, a high-quality sealing material can be obtained. In addition, because the thickness of the coating layer formed of fluororesin covering the string-like rubber is 0.20 mm or less, it is more easily deformed compared to those with a coating layer thickness greater than 0.20 mm, resulting in a sealing material that can be installed without requiring a large clamping force.
[0010] In the second invention, in the first invention, When performing high-frequency induction heating, the mold groove is configured to be positioned on the outside of the coil.
[0011] According to the above configuration, the annular sealing material can be easily removed after high-frequency induction heating.
[0012] In the third invention, in the first or second invention, The mold is formed from a magnetic material.
[0013] According to the above configuration, since the mold made of a magnetic material can be efficiently heated by the high-frequency coil, a sealing material with good quality and less influence by heating can be obtained.
[0014] In the fourth invention, in any one of the first to third inventions, The string-shaped rubber is formed of silicone rubber.
[0015] According to the above configuration, since it has appropriate softness, a sealing material that can easily ensure sealing performance without applying a large tightening force can be obtained.
[0016] In the fifth invention, in any one of the first to fourth inventions, The fluororesin includes a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin.
[0017] According to the above configuration, a sealing material that can be suitably used as a sealing means for applications requiring plasma resistance or chemical resistance can be obtained.
Effect of the Invention
[0018] As described above, according to the present invention, while suppressing the influence of heating during joining, both ends of the string-shaped rubber can be efficiently joined to obtain a sealing material with good quality.
Brief Description of the Drawings
[0019] [Figure 1] It is a cross-sectional view showing an O-ring which is a manufacturing target according to an embodiment of the present invention. [Figure 2] It is a perspective view showing an enlarged connection part of the string-shaped rubber before joining. [Figure 3] It is an enlarged perspective view showing one end of the string-shaped rubber. [Figure 4] It is a perspective view showing a connection part heating process. [Figure 5] It is a flowchart showing a method for manufacturing a sealing material according to an embodiment of the present invention. [Figure 6] This is an enlarged front view showing a modified embodiment of the present invention, specifically the connection portion before joining. [Figure 7] (a) is a cross-sectional view of Figure 6 along the line VIIa-VIIa, (b) is a cross-sectional view of Figure 6 along the line VIIb-VIIb, (c) is a cross-sectional view of Figure 6 along the line VIIc-VIIc, and (d) is a cross-sectional view of Figure 6 along the line VIId-VIId. [Modes for carrying out the invention]
[0020] The embodiments will be described in detail below.
[0021] Figure 1 shows an O-ring 10 as a sealing material according to the embodiment. The shape of the O-ring 10 is specified in JIS B2401-1:2012, for example, its inner diameter is 30 mm or more and 500 mm or less, and its thickness is 2 mm or more and 10 mm or less.
[0022] The O-ring 10 according to this embodiment comprises an annular core material 11 (string-shaped rubber) and a coating layer 12 covering the core material 11. The coating layer 12 is made of a fluororesin. For this reason, the O-ring 10 can be suitably used as a sealing means in applications requiring plasma resistance or chemical resistance, such as semiconductor manufacturing equipment. The thickness of the coating layer 12 is 0.20 mm or less.
[0023] According to the embodiment of the O-ring 10, the thickness of the coating layer 12 made of fluororesin that covers the core material 11 is 0.20 mm or less, so it can be installed without requiring a large tightening force. The inventors investigated the reason why a large tightening force is required when installing the O-ring 10 in which the core material 11 is covered with a coating layer 12 of fluororesin, and as a result they focused on the fact that a large repulsive force is generated in the O-ring 10 when compressed, and came up with the idea of controlling this repulsive force by the thickness of the coating layer 12.
[0024] The core material 11 is preferably formed of crosslinked rubber. Examples of rubber used to form the core material 11 include silicone rubber, nitrile rubber, hydrogenated nitrile rubber, fluororubber, ethylene propylene copolymer rubber, ethylene propylene diene terpolymer rubber, and acrylic rubber. From the viewpoint of not requiring a large tightening force during installation, silicone rubber is preferred among these. From the same viewpoint, the hardness of the rubber forming the core material 11 is preferably A40 to A50, and more preferably A43 to A47. This hardness is measured using a Type A durometer based on JIS K6253-3:2023 for the core material 11 before coating with the coating layer 12.
[0025] Examples of fluororesins that form the coating layer 12 include thermoplastic resins such as tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA) resin, polytetrafluoroethylene (PTFE) resin, tetrafluoroethylene hexafluoropropylene copolymer (FEP) resin, and ethylene tetrafluoroethylene copolymer (ETFE) resin. The fluororesin that forms the coating layer 12 preferably contains one or more of these, and it is preferable to include PFA resin from the viewpoint of having excellent plasma resistance and not requiring a large tightening force during installation.
[0026] The thickness of the coating layer 12 is 0.20 mm or less, but from the viewpoint of not requiring a large tightening force during installation, it is preferably 0.15 mm or less, more preferably 0.10 mm or less, and even more preferably 0.06 mm or less. On the other hand, from the viewpoint of processability for covering the core material 11 with the fluororesin coating layer 12, the thickness of the coating layer 12 is preferably 0.02 mm or more, and more preferably 0.03 mm or more.
[0027] The ratio of the thickness of the coating layer 12 to the diameter of the O-ring 10 is preferably 7% or less, more preferably 6% or less, even more preferably 4% or less, and even more preferably 2% or less, from the viewpoint of not requiring a large tightening force during installation. The ratio of the thickness of the coating layer 12 to the diameter of the O-ring 10 is preferably 0.5% or more, more preferably 1% or more, from the viewpoint of processability for coating the core material 11 with the fluororesin coating layer 12.
[0028] The hardness of the O-ring 10 according to this embodiment is preferably A60 to A80, and more preferably A65 to A77, from the viewpoint of not requiring a large tightening force during installation. This hardness is also measured using a Type A durometer in accordance with JIS K6253-3:2023 for the O-ring 10 after coating with the coating layer 12.
[0029] The linear load of the O-ring 10 in this embodiment when compressed by 25% is preferably 3.0 N / mm or less, and more preferably 2.0 N / mm or less, from the viewpoint of not requiring a large tightening force during installation. This linear load when compressed by 25% is calculated by dividing the load required to compress the O-ring 10 by 25% in the thickness direction by the average circumference, that is, the sum of the inner diameter and thickness multiplied by pi (π).
[0030] Next, a method for manufacturing the O-ring 10 according to the embodiment will be described.
[0031] First, in the preparation process, a string-like core material 11 is manufactured. The rubber string-like core material 11 can be manufactured, for example, by extrusion molding.
[0032] Then, as shown in step S01 of Figure 5, although not shown in detail, the string-shaped core material 11 (rubber string) is passed through a head attached to an extrusion molding machine, and the surface of the core material 11 is coated with a fluororesin coating layer 12 along its length by a so-called coated extrusion molding method, thereby producing a long string-shaped rubber 10'.
[0033] When coating the string-shaped core material 11 with a fluororesin coating layer 12, the string-shaped core material 11 is inserted through a nipple and moved forward (downstream) along its length at a constant speed. Molten fluororesin is also supplied from the extrusion molding machine to the die.
[0034] Then, an O-ring 10 is manufactured by cutting a predetermined length from the recovered string-like rubber 10' and joining its ends to form a ring. The joining method will be described in detail below.
[0035] As described above, prepare a string-shaped rubber 10' of a predetermined length covered with a fluororesin coating layer 12 having a thickness of 0.20 mm or less.
[0036] Next, in the uneven surface formation process, as shown in Figures 2 and 3, an uneven surface 13 is formed on the connecting surface of the string-shaped rubber 10', which is fitted together to form a ring and generates a catch at least in the circumferential direction.
[0037] Next, in the fitting process, the uneven surfaces 13 at both ends of the string-shaped rubber 10' are fitted together while moving them relative to each other, for example, in a direction perpendicular to the circumferential direction of the O-ring 10. This makes it easier to position the uneven surfaces 13, and after fitting, the uneven surfaces 13 will not shift even if a small force is applied in the circumferential direction. It is preferable to apply, for example, a two-part liquid silicone rubber as an adhesive to the string-shaped rubber 10' before fitting.
[0038] Next, in the fluororesin film winding process shown in step S02 of Figure 5, with the uneven surfaces 13 fitted together, the connecting portion 14, including at least the outer circumference of the uneven surfaces 13, is covered with a fluororesin film 15 made of the same material as the resin coating. The thickness of the fluororesin film 15 is not particularly limited, but for example, it can be the same thickness as the coating layer 12. The thickness of the fluororesin film 15 can be set to be thicker because it can be ground down after molding even if the portion of the fluororesin film 15 is too thick.
[0039] Next, a heating process for the connection part is performed. In step S03, the connection part 14 is placed in a mold groove (not shown) provided in the mold 21.
[0040] Next, in step S04, the mold 21 is closed to sandwich the connection. Figure 4 shows an example in which mold grooves are formed in two places on the upper side, but the number of mold grooves can be one or three or more. Mold grooves may also be formed on the lower side of the high-frequency coil 22.
[0041] Next, in step S05, the closed mold 21 is set inside the high-frequency coil 22. If mold grooves are formed above and below the high-frequency coil 22, the timing of closing the mold 21 can be adjusted accordingly.
[0042] Next, in step S06, the connection portion 14 is coated with fluororesin by high-frequency induction heating. For example, only the connection portion 14 and the area around the connection portion 14 covered with the fluororesin film 15 are heated by high-frequency heating using a heating device 20 for 2 minutes, raising the temperature from room temperature to 300°C, and then held for 1 minute. Here, it is not necessary to heat the entire string-shaped rubber 10', so it is not necessary to heat the already coated coating layer 12 over a wide area, and the quality is less likely to deteriorate.
[0043] Next, in the cooling process of step S07, the mold 21 is cooled. In this embodiment, cooling is performed by natural cooling. In addition to natural cooling, the cooling process can also be performed by air cooling with a fan or cooling with a liquid such as distilled water.
[0044] Next, in the demolding process of step S08, an annular O-ring 10 is obtained after demolding. At this time, as shown in Figure 4, since the annular O-ring 10 is on the outside of the high-frequency coil 22, the O-ring 10 and the high-frequency coil 22 do not interfere with each other during demolding, making it easy to remove the O-ring 10.
[0045] In some cases, if the fluororesin film 15 portion protrudes more than other outer surfaces, a finishing process such as polishing is performed to ensure that the surface is free of irregularities.
[0046] Thus, in this embodiment, the mold only needs to be able to sandwich at least the portion covered by the fluororesin film 15 and its surrounding area, so the mold 21 can be made smaller and is easy to place inside the high-frequency coil 22. Also, since the portion that is heated by high-frequency induction is limited, the range of the effect of heating is limited compared to when the entire surface is heated. As a result, a high-quality O-ring 10 can be obtained. Furthermore, because the thickness of the coating layer 12 made of fluororesin that covers the string-shaped rubber 10' is 0.20 mm or less, it is more easily deformed compared to those with a coating layer thickness greater than 0.20 mm, and the O-ring 10 can be attached without requiring a large tightening force.
[0047] Furthermore, since the mold 21 made of magnetic material can be efficiently heated by the high-frequency coil 22, a high-quality O-ring 10 with minimal effects from heating can be obtained.
[0048] In this embodiment, by forming the string-shaped rubber 10' from silicone rubber, an O-ring 10 is obtained that has appropriate softness, making it easy to ensure sealing performance without applying a large tightening force.
[0049] In this embodiment, since the fluororesin includes a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin, the O-ring 10 can be suitably used as a sealing means for applications requiring plasma resistance or chemical resistance.
[0050] In this embodiment, the O-ring 10 has a linear load of 3.0 N / mm or less when compressed by 25%, so it can exhibit sealing performance without requiring a large tightening force.
[0051] As described above, according to the present invention, it is easy to join both ends of the string-shaped rubber 10' and to obtain a product with stable finished dimensions.
[0052] -Variations- Figures 6 and 7 show modified examples of the string-like rubber 110' of the embodiment of the present invention, which differ from the above embodiment in that the shape of the connecting part is different. In the following modifications, the same reference numerals are used for parts that are the same as in Figures 1 to 5, and their detailed descriptions are omitted.
[0053] In other words, in this modified example, the shape of the uneven surfaces 113 differs from that of the ends of the string-shaped rubber 110' in the above embodiment.
[0054] As shown in the figure, semicircular notches are provided at both ends of the string-like rubber 110', with the cut surfaces intersecting perpendicularly when viewed from the longitudinal direction. By offsetting the phase of the notches at both ends by 90°, the notches at both ends are fitted together while relatively moving in a direction perpendicular to the circumferential direction of the O-ring 110, so that the uneven surface 113 does not shift even when pulled in the circumferential direction.
[0055] In particular, in this modified example, even the smallest cross-sectional area of the notch in the uneven surface 113 maintains a cross-sectional area that is more than half the size of the area without a notch. Therefore, it has higher tensile strength and is less prone to displacement compared to the uneven surface 13 of the above embodiment.
[0056] (Other embodiments) The present invention may also have the following configuration in the above embodiment.
[0057] In other words, although the O-ring 10 was shown as an example of a sealing material in the above embodiment, it is not limited to this, and any annular sealing material may be used.
[0058] In the above embodiment, an example was shown in which the string-like core material 11 is joined by fitting, but other methods such as butting together end faces that have been cut perpendicular or at an angle to the axial direction are also possible.
[0059] In the above embodiment, the surface of the string-shaped core material 11 is covered with a fluororesin coating layer 12 by a coating extrusion molding method. However, the invention is not limited to this, and for example, the coating layer 12 may be formed by applying a fluororesin coating to the surface of the string-shaped core material 11.
[0060] In the manufacturing method of the O-ring 10 according to the embodiment, the surface of the string-shaped core material 11 before it is coated with the coating layer 12 may be subjected to a surface treatment to improve adhesion with the fluororesin coating layer 12. By performing such a surface treatment on the surface of the string-shaped core material 11 before it is coated with the coating layer 12, the adhesion of the core material 11 to the fluororesin coating layer 12 is improved, and as a result, the occurrence of wrinkles on the surface of the thin coating layer 12 with a thickness of 0.20 mm or less can be suppressed. Examples of such surface treatments include primer treatment, Itro treatment, plasma treatment, etc.
[0061] In the manufacturing method of the O-ring 10 according to the embodiment, plasma treatment may be applied to the surface of the molten fluororesin R that is intended to come into contact with the string-shaped core material 11 before coating the string-shaped core material 11, in order to improve adhesion with the string-shaped core material 11. As a result of applying plasma treatment to the contact surface of the coating layer 12 with the core material 11, the adhesion of the fluororesin coating layer 12 to the core material 11 can be improved, and the occurrence of wrinkles on the surface of the coating layer 12 can be suppressed.
[0062] The embodiments described above are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or uses. [Explanation of symbols]
[0063] 10', 110' String-shaped rubber 10 O-rings (sealants) 11 Core material 12 Covering layer 13,113 Uneven surface 14 Connection part 15 Fluororesin film 20 Heating device 21 molds 22 High-frequency coil
Claims
1. A core material formed of crosslinked rubber is prepared, and a string-shaped rubber of a predetermined length is prepared, covered with a fluororesin with a thickness of 0.20 mm or less. The aforementioned core material joins the connecting surfaces of the cross-linked string-like rubber, At least the outer circumference of the connecting surface of the string-like rubber is covered with a fluororesin film made of the same material as the fluororesin, The connection portion covered with the aforementioned fluororesin film and only the area surrounding the connection portion are placed in the mold groove of the mold. Close the mold and sandwich the connecting part, The mold is placed inside the high-frequency coil. High-frequency induction heating is performed to melt the fluororesin film and form a fluororesin coating. The mold is cooled and the annular sealing material is removed. A method for manufacturing a sealing material characterized by the following:
2. When performing high-frequency induction heating, the mold groove is positioned on the outside of the high-frequency coil. A method for manufacturing a sealing material according to claim 1.
3. The mold is formed from a magnetic material. A method for manufacturing a sealing material according to claim 1 or 2, characterized by the above.
4. The string-like rubber is formed of silicone rubber. A method for manufacturing a sealing material according to claim 1 or 2, characterized by the above.
5. The fluorine-based resin includes a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin. A method for manufacturing a sealing material according to claim 1 or 2, characterized by the above.