Method for manufacturing a sealing material and sealing material

Abstract

To provide a method for manufacturing seal material in which a product having a stable finished dimension is obtained by making both ends of a string-like rubber easier to be bonded.SOLUTION: A string-like rubber 10' of a predetermined length which is covered by fluorine-based resin having the thickness of 0.20 mm or less is prepared, uneven surfaces 13 that interlock with each other on connection surfaces of the string-like rubber 10' at least in a circumferential direction in the state where the surfaces are fitted with each other into a ring-shape, are formed, the outer periphery of at least the uneven surfaces 13 is covered by a fluororesin film 15 of the same material as fluorine-based resin coating in the state where the uneven surfaces 13 are fitted with each other, a connection part 14 covered by the film 15 and only the periphery of the connection part 14 are heated by a heating device 20, and then cooled to fabricate a ring-shaped seal material.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a sealing material and a sealing material.

Background Art

[0002] A sealing material in which an annular core material is coated with a fluororesin is known. 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 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] In such a method, when connecting and joining both ends of the string-shaped core material, if the connection surface is displaced, it becomes difficult to manufacture within the range of manufacturing error of the annular sealing material (for example, an O-ring).

[0006] The present invention has been made in view of such a point, and an object thereof is to facilitate joining both ends of a string-shaped rubber and obtain a product with stable finished dimensions.

Means for Solving the Problems

[0007] In order to achieve the above object, in this invention, the shapes of both ends of the string-shaped rubber are devised.

[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 formed with uneven surfaces that create a catch at least in the circumferential direction when they are fitted together to form an annular shape. With the aforementioned uneven surfaces fitted together, at least the outer circumference of the uneven surfaces is covered with a film made of the same material as the fluororesin. The connection portion covered with the aforementioned film and the area surrounding the connection portion are heated with a heating device. The device is then cooled to create an annular sealing material.

[0009] According to the above configuration, since the connection surface of the string-shaped rubber is formed with irregularities, the connection part will not shift even in a mold where the inside is not visible during heating, for example, and a sealing material with good dimensional accuracy can be obtained. The irregularities can be fitted together by relatively shifting them in directions other than the circumferential direction, for example. In addition, because the thickness of the coating layer formed of fluororesin that covers the string-shaped rubber is thin, at 0.20 mm or less, it is more easily deformed compared to those with a coating layer thickness greater than 0.20 mm, and a sealing material that can be installed without requiring a large tightening force can be obtained.

[0010] In the second invention, in the first invention, The string-like rubber is made of silicone rubber.

[0011] With the above configuration, a sealing material can be obtained that has moderate flexibility, making it easy to ensure sealing performance without applying a large tightening force.

[0012] In the third invention, The connecting parts of the string-like rubber are joined in a ring shape by joining uneven surfaces that create friction at least in the circumferential direction. The outer circumference of the string-like rubber is covered with a fluororesin with a thickness of 0.20 mm or less.

[0013] According to the above configuration, since the connecting surface of the string-shaped rubber forms a concavo-convex surface, for example, even in a mold where the inside cannot be seen during heating, the connecting part does not shift, and a sealing material with high dimensional accuracy can be obtained. Further, since the thickness of the coating layer formed of the fluororesin covering the string-shaped rubber is as thin as 0.20 mm or less, it is easier to deform than those with a coating layer thickness greater than 0.20 mm, and the sealing material can be attached without requiring a large tightening force.

[0014] In the fourth invention, in the third invention, The string-shaped rubber is formed of silicone rubber.

[0015] According to the above configuration, since the sealing material has appropriate softness, it is easy to ensure the sealing performance without applying a large tightening force.

[0016] In the fifth invention, in the third or fourth invention, The fluororesin contains a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin.

[0017] According to the above configuration, the sealing material can be suitably used as a sealing means for applications where plasma resistance is required or applications where chemical resistance is required.

Effect of the Invention

[0018] As described above, according to the present invention, both ends of the string-shaped rubber are easily joined, and a product with stable finished dimensions can be obtained.

Brief Description of the Drawings

[0019] [Figure 1] It is a cross-sectional view showing an O-ring which is an object to be manufactured 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] It is a front view showing an enlarged connection part before joining according to a modified example of an embodiment of the present invention. [Figure 7] (a) is a cross-sectional view taken along line VIIa-VIIa of FIG. 6, (b) is a cross-sectional view taken along line VIIb-VIIb of FIG. 6, (c) is a cross-sectional view taken along line VIIc-VIIc of FIG. 6, and (d) is a cross-sectional view taken along line VIId-VIId of FIG. 6.

Embodiments for Carrying out the Invention

[0020] Hereinafter, embodiments will be described in detail.

[0021] FIG. 1 shows an O-ring 10 as a sealing material according to an embodiment. The O-ring 10 has a shape defined in JIS B2401-1:2012. For example, the inner diameter is 30 mm or more and 500 mm or less, and the thickness is 2 mm or more and 10 mm or less.

[0022] The O-ring 10 according to the embodiment includes an annular core material 11 (string-shaped rubber) and a coating layer 12 that covers the core material 11. The coating layer 12 is formed of a fluororesin. Therefore, this O-ring 10 can be suitably used as a sealing means for applications that require plasma resistance or chemical resistance, such as semiconductor manufacturing equipment. And the thickness of the coating layer 12 is 0.20 mm or less.

[0023] According to the O-ring 10 according to the embodiment, since the thickness of the coating layer 12 formed of a fluororesin covering the core material 11 is 0.20 mm or less, it can be attached without requiring a large tightening force. The inventors examined the cause of the need for a large tightening force when attaching the O-ring 10 in which the core material 11 is covered with the coating layer 12 of the fluororesin. As a result, they focused on the point that a large repulsive force is generated in the O-ring 10 against compression, and came up with the idea of controlling that 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, the string-shaped core material 11 (rubber string) is passed through a head attached to an extrusion molding machine (not shown), and the surface of the core material 11 is coated with a fluororesin coating layer 12 along its length by a so-called coating extrusion molding method, thereby producing a long string-shaped rubber 10'.

[0033] Although not shown in the diagram, when coating the string-shaped core material 11 with a fluororesin coating layer 12, for example, 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 both ends to form a ring. The joining method will be described in detail below.

[0035] As described above, first, a string-shaped rubber 10' of a predetermined length is prepared, covered with a fluororesin coating layer 12 with 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' by cutting, shaping, etc., which creates a catch at least in the circumferential direction when the rubbers are fitted together to form an annular shape.

[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 desirable to apply an adhesive, such as a two-part liquid silicone rubber, to the uneven surfaces 13 of the string-shaped rubber 10' before fitting.

[0038] Next, in the fluororesin film coating 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 fluororesin coating. The thickness of the fluororesin film 15 is changed depending on the heating temperature, heating time, the material of the resin film, the thickness of the string-like rubber 10', etc., but for example, it is set to the same thickness as the coating layer 12. Even if the fluororesin film 15 becomes too thick, it can be ground down after molding, so its thickness can be set to be thicker.

[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 connecting portion 14. Figure 4 shows an example in which mold grooves are formed in two locations at the top, but the number of mold grooves can be one or three or more. Mold grooves may also be formed on the underside 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 from room temperature to 300°C for 2 minutes using the heating device 20, 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 layer 12 over a wide area, and the area affected by heating is narrowed, making it less likely for quality 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, the annular O-ring 10 is on the outside of the high-frequency coil 22, so the O-ring 10 and the high-frequency coil 22 do not interfere with each other during demolding.

[0045] If the fluororesin film 15 portion protrudes more than the other outer surfaces, a finishing process such as polishing is performed to ensure that the surface is smooth. The thickness of the fluororesin film may also be adjusted empirically based on the degree of protrusion.

[0046] As described above, in this embodiment, since the connection surface 13 is formed on the connecting surface of the string-shaped rubber 10', the connecting part 14 does not shift inside the mold 21, for example when heating, and an O-ring 10 with good dimensional accuracy can be obtained. Since the thickness of the coating layer 12 made of fluororesin that covers the string-shaped rubber 10' is 0.20 mm or less, an O-ring 10 can be obtained that is more easily deformed than one with a coating layer thickness greater than 0.20 mm, and can be installed without requiring a large tightening force.

[0047] 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.

[0048] In this embodiment, since the fluororesin includes a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin, the resulting O-ring 10 can be suitably used as a sealing means in applications requiring plasma resistance or chemical resistance.

[0049] 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.

[0050] As described above, according to the present invention, it is possible to easily join both ends of the string-shaped rubber 10' and obtain a product with stable finished dimensions.

[0051] -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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] (Other embodiments) The present invention may also have the following configuration in the above embodiment.

[0056] 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.

[0057] 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.

[0058] In the above embodiment, the connection portion 14 was heated using an induction heating device with a high-frequency coil 22, but heating may also be performed using other heating devices capable of localized heating.

[0059] 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.

[0060] 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.

[0061] 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]

[0062] 10', 110' String-shaped rubber 10 O-rings 11 Core material 12 Covering layer 13,113 Uneven surface 14 Connection part 15 Fluororesin film 20 Heating device 21 molds

Claims

1. A string-shaped rubber of a predetermined length is prepared, in which the outer circumference of the crosslinked rubber is covered with a fluororesin with a thickness of 0.20 mm or less. The connecting surfaces of the string-like rubber are formed with uneven surfaces that create a catch at least in the circumferential direction when they are fitted together to form an annular shape. With the aforementioned uneven surfaces fitted together, at least the outer circumference of the uneven surfaces is covered with a film made of the same material as the fluororesin. The connection portion covered with the aforementioned film and the area surrounding the connection portion are heated with a heating device. It is then cooled to create an annular sealant. A method for manufacturing a sealing material characterized by the following:

2. The string-like rubber is formed of silicone rubber. A method for manufacturing a sealing material according to claim 1.

3. The connecting portion of the cross-linked string-like rubber is joined in an annular shape by joining uneven surfaces that create a catch in at least the circumferential direction, The outer circumference of the cross-linked string-shaped rubber is covered with a fluororesin with a thickness of 0.20 mm or less. A sealing material characterized by the following features.

4. The string-like rubber is formed of silicone rubber. The sealing material according to feature 3.

5. The fluorine-based resin includes a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin. The sealing material according to feature 3 or 4.

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