Method for manufacturing seal material

Abstract

To provide a method for manufacturing seal material in which a product having a stable finished dimension can be obtained by making both ends of a string-like rubber easier to be bonded.SOLUTION: A string-like rubber 10' of a predetermined length, covered with a fluorine-based resin having a thickness of 0.20 mm or less, is prepared. The connection surfaces of the string-like rubber 10' are bonded, and at least the outer periphery of the bonded surfaces is covered with a fluororesin film 15 made of the same material as the fluorine-based resin coating. The connection part 14 covered with the fluororesin film 15, and only the periphery of the connection part 14, is arranged in a metal mold groove of a metal mold 21, which is then closed to sandwich the connection part 14, placed inside a high-frequency coil 22, and subjected to high-frequency induction heating to fuse the fluororesin film 15 and form a fluororesin coating. After cooling the metal mold 21, the ring-shaped seal material 10 is taken out.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Sealing materials in which an annular core material is coated with a fluororesin are known. For example, Patent Document 1 discloses an O-ring in which an annular core material made of heat-resistant rubber is coated with a fluororesin coating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5339620 Summary of the Invention [Problem to be solved by the invention]

[0004] To coat a ring-shaped core material with a fluororesin, there is a method in which a string-shaped core material is coated with the fluororesin and both ends are joined together.

[0005] Heating equipment is generally used to join connections, but the connection part of an annular sealing material (e.g., an O-ring) is relatively small, so there is a problem that it cannot be heated efficiently using a high-temperature press with a wide heating area, for example.

[0006] The present invention has been made in view of the above points, and its object is to make it possible to efficiently heat and bond both ends of a rubber string. [Means for solving the problem]

[0007] In order to achieve the above object, in this invention, only the connecting portion and its surrounding area are heated to join the rubber strings into an annular shape.

[0008] Specifically, in the first invention, A rubber string of a predetermined length covered with a fluorine-based resin having a thickness of 0.20 mm or less is prepared. Joining the connecting surfaces of the rubber strings, At least the outer periphery of the connecting surface of the rubber string is covered with a fluororesin film made of the same material as the fluororesin, placing only the connection portion covered with the fluororesin film and the periphery of the connection portion in a mold groove of a mold; The mold is closed to sandwich the connection portion; The mold is placed inside a high-frequency coil; high-frequency induction heating is performed to melt the fluororesin film to form a fluororesin coating; The mold is cooled and the annular sealing material is removed.

[0009] According to the above configuration, the mold can be made small because it only needs to sandwich at least the portion covered with the fluororesin film and its surroundings, and the mold can be easily placed inside the high-frequency coil. Furthermore, since the portion to be heated by high-frequency induction is limited, the range of the heating effect is limited compared to when the entire body is heated. This results in a high-quality sealing material. Furthermore, since the thickness of the coating layer made of fluororesin that covers the rubber string is 0.20 mm or less, the sealing material is more easily deformed than those with coating layers thicker than 0.20 mm, and a sealing material that can be installed without requiring a large tightening force is obtained.

[0010] In the second invention, in the first invention, When high frequency induction heating is performed, the mold groove is arranged outside the high frequency coil.

[0011] According to the above configuration, the annular sealing material can be easily removed after high-frequency induction heating.

[0012] In a third aspect of the present invention, in the first or second aspect of the present invention, The mold is made of a magnetic material.

[0013] According to the above-mentioned configuration, the mold made of a magnetic material can be efficiently heated by the high frequency coil, so that a high quality sealing material that is less affected by heating can be obtained.

[0014] In a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, The rubber strings are made of silicone rubber.

[0015] According to the above-mentioned configuration, a sealing material having a suitable softness can be obtained, and therefore, sealing performance can be easily ensured without applying a large tightening force.

[0016] In a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, The fluorine-based resin may include a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin.

[0017] According to the above-mentioned configuration, a sealing material can be obtained that can be suitably used as a sealing means in applications requiring plasma resistance or chemical resistance. [Effects of the Invention]

[0018] As described above, according to the present invention, both ends of a rubber string can be efficiently joined while suppressing the influence of heat during joining, thereby obtaining a high-quality sealing material. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing an O-ring to be manufactured according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged perspective view showing a connecting portion of the rubber strings before joining. [Figure 3] FIG. 2 is an enlarged perspective view showing one end of a rubber string. [Figure 4] FIG. [Figure 5] 3 is a flowchart showing a method for manufacturing a sealing material according to an embodiment of the present invention. [Figure 6] FIG. 10 is an enlarged front view showing a connection portion before joining according to a modified example of the embodiment of the present invention. [Figure 7] 6. (a) is a cross-sectional view taken along line VIIa-VIIa in FIG. 6, (b) is a cross-sectional view taken along line VIIb-VIIb in FIG. 6, (c) is a cross-sectional view taken along line VIIc-VIIc in FIG. 6, and (d) is a cross-sectional view taken along line VIId-VIId in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] The embodiments will be described in detail below.

[0021] 1 shows an O-ring 10 as a sealing material according to an embodiment. The shape of the O-ring 10 is specified in JIS B2401-1:2012, and is, for example, an inner diameter of 30 mm to 500 mm and a thickness of 2 mm to 10 mm.

[0022] The O-ring 10 according to the embodiment includes a ring-shaped core material 11 (a rubber string) and a coating layer 12 that coats the core material 11. The coating layer 12 is made of a fluororesin. This makes the O-ring 10 suitable for use 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 O-ring 10 of this embodiment, the thickness of the coating layer 12 formed of a fluororesin that coats the core material 11 is 0.20 mm or less, so that it can be attached without requiring a large tightening force. The inventors studied the reason why a large tightening force is required when attaching the O-ring 10, whose core material 11 is coated with the fluororesin coating layer 12, and as a result, they focused on the fact that a large repulsive force is generated in the O-ring 10 when compressed, and arrived at the idea of ​​controlling this repulsive force by the thickness of the coating layer 12.

[0024] The core 11 is preferably made of cross-linked rubber. Examples of rubbers that can be used to form the core 11 include silicone rubber, nitrile rubber, hydrogenated nitrile rubber, fluororubber, ethylene propylene copolymer rubber, ethylene propylene diene terpolymer rubber, and acrylic rubber. Of these, silicone rubber is preferred as the rubber used to form the core 11, as it does not require a large tightening force during installation. From the same perspective, the hardness of the rubber that forms the core 11 is preferably A40 or more and A50 or less, more preferably A43 or more and A47 or less. This hardness is measured using a Type A durometer based on JIS K6253-3:2023 on the core 11 before it is coated with the coating layer 12.

[0025] Examples of fluorine-based resins 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 fluorine-based resin that forms the coating layer 12 preferably contains one or more of these, and preferably contains PFA resin from the viewpoints of 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 of coating 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 coating layer 12 to the diameter of 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 coating layer 12 to the diameter of O-ring 10 is preferably 0.5% or more, more preferably 1% or more, from the viewpoint of processability of coating core material 11 with fluororesin coating layer 12.

[0028] The hardness of the O-ring 10 according to the embodiment is preferably A60 to A80, more preferably A65 to A77, from the viewpoint of not requiring a large tightening force during installation. This hardness is also measured by 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 line load at 25% compression of the O-ring 10 according to the embodiment is preferably 3.0 N / mm or less, and more preferably 2.0 N / mm or less, from the viewpoint that a large tightening force is not required during installation. This line load at 25% compression is calculated by dividing the load required to compress the O-ring 10 by 25% in the thickness direction by the average circumferential length, that is, the sum of the inner diameter and thickness multiplied by pi.

[0030] Next, a method for manufacturing the O-ring 10 according to the embodiment will be described.

[0031] First, in a preparation step, a string-like core material 11 is produced. The string-like core material 11 made of rubber can be produced by extrusion molding, for example.

[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 coating layer 12 of fluorine-based resin along its length by a so-called coating extrusion molding method, thereby producing a long string-shaped rubber 10'.

[0033] When the string-shaped core material 11 is coated with the fluororesin coating layer 12, the string-shaped core material 11 is inserted into a nipple and moved forward (downstream) along its length at a constant speed. Also, molten fluororesin is supplied to the die from the extrusion molding machine.

[0034] A predetermined length is then cut from the collected rubber string 10', and both ends are joined to form a ring, thereby producing the O-ring 10. The joining method will be described in detail below.

[0035] As described above, a rubber string 10' having a predetermined length and covered with a fluorine-based resin coating layer 12 having a thickness of 0.20 mm or less is prepared.

[0036] Next, in the uneven surface forming step, as shown in Figures 2 and 3, an uneven surface 13 is formed on the connecting surface of the rubber string 10' to generate a catch at least in the circumferential direction when the rubber strings 10' are fitted together to form a ring.

[0037] Next, in the fitting process, the uneven surfaces 13 on both ends of the rubber string 10' are fitted while being moved relatively, for example, in a direction perpendicular to the circumferential direction of the O-ring 10. This makes it easy 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. Before fitting, it is desirable to apply, for example, a two-component curing liquid silicone rubber as an adhesive to the rubber string 10'.

[0038] Next, in the fluororesin film winding step shown in step S02 of Fig. 5, with the concave-convex surfaces 13 engaged, the connection portion 14, including at least the outer periphery of the concave-convex 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 may be the same as that of the coating layer 12, for example. Even if the fluororesin film 15 becomes too thick, it can be ground off after molding, so the thickness can be set to be thicker.

[0039] Next, a connecting portion heating step is performed. In step S03, the connecting portion 14 is placed in a mold groove (not shown) provided in a mold 21.

[0040] Next, in step S04, mold 21 is closed to sandwich the connection portion. While Fig. 4 shows an example in which mold grooves are formed in two places on the upper side, the number of mold grooves may be one or three or more. A mold groove may also be formed on the lower side of 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 at which the mold 21 is closed may be devised.

[0042] Next, in step S06, the connection portions 14 are coated with a fluororesin by high-frequency induction heating. For example, only the connection portions 14 and the periphery of the connection portions 14 covered with the fluororesin film 15 are heated by the heating device 20 for two minutes using high-frequency heating to raise the temperature from room temperature to 300°C, and then held at that temperature for one minute. Here, it is not necessary to heat the entire rubber string 10', so there is no need to heat the already coated coating layer 12 over a wide area, and quality is less likely to deteriorate.

[0043] Next, in the cooling step of step S07, the mold 21 is cooled. In this embodiment, the mold 21 is cooled by natural cooling. In addition to natural cooling, the cooling step can also be performed by air cooling using a fan or cooling with a liquid such as distilled water.

[0044] Next, after demolding in the demolding process of step S08, annular O-ring 10 is obtained. At this time, as shown in Fig. 4, annular O-ring 10 is located outside high-frequency coil 22, so that O-ring 10 and high-frequency coil 22 do not interfere with each other during demolding, making it easy to remove O-ring 10.

[0045] In some cases, if the fluororesin film 15 portion protrudes from the other outer surfaces, a finishing process such as polishing is carried out to smooth out the surface irregularities.

[0046] As described above, in this embodiment, the mold 21 only needs to sandwich at least the portion covered with the fluororesin film 15 and its surrounding area, so the mold 21 can be made smaller and the mold 21 can be easily placed inside the high-frequency coil 22. Furthermore, because the portion that is heated by high-frequency induction is limited, the range of the effect of heating is more limited than when the entire ring is heated. This results in a high-quality O-ring 10. Furthermore, because the thickness of the coating layer 12 formed of a fluororesin that coats the rubber string 10' is 0.20 mm or less, the O-ring 10 is more easily deformed than a coating layer with a 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 a magnetic material can be efficiently heated by the high frequency coil 22, a high quality O-ring 10 that is less affected by heating can be obtained.

[0048] In this embodiment, the rubber strings 10' are made of silicone rubber, which provides a moderate degree of softness, and therefore the O-ring 10 can easily ensure sealing performance without applying a large tightening force.

[0049] In this embodiment, the fluororesin contains tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin, so the O-ring 10 can be suitably used as a sealing means in applications requiring plasma resistance or chemical resistance.

[0050] The O-ring 10 of this embodiment has a line 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 rubber string 10', and it is easy to obtain a product with stable finished dimensions.

[0052] -Variations- 6 and 7 show a modified example of the rubber string 110' according to the embodiment of the present invention, which differs from the above embodiment in that the shape of the connecting portion is different. In the following modified examples, the same parts as those in Figs. 1 to 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0053] That is, in this modification, the shape of the uneven surface 113 at both ends of the rubber string 110' is different from that of the above embodiment.

[0054] As shown in the figure, semicircular notches are provided at both ends of the rubber string 110' so that the cut surfaces intersect perpendicularly when viewed in the longitudinal direction. By shifting the phases of the two ends by 90°, when the notches at both ends are fitted together while moving relatively in a direction perpendicular to the circumferential direction of the O-ring 110, the uneven surface 113 does not shift even when pulled in the circumferential direction.

[0055] In particular, in this modification, even the smallest cross-sectional area of ​​the notches in the uneven surface 113 remains at more than half the size of the portion without the notches. Therefore, compared to the uneven surface 13 of the above embodiment, the strength against tension is higher and the surface is less likely to slip.

[0056] (Other embodiments) The present invention may be configured as follows in relation to the above embodiment.

[0057] That is, in the above embodiment, the O-ring 10 is shown as an example of the sealing material, but it is not particularly limited to this, and any other annular sealing material may be used.

[0058] In the above embodiment, an example was shown in which the string-like core material 11 was joined by fitting, but it may also be a mode in which end faces cut perpendicular or at an angle to the axial direction are butted together.

[0059] In the above embodiment, the surface of the string-shaped core material 11 is covered with a fluororesin covering layer 12 by a covering extrusion molding method, but this is not particularly limited to this, and for example, the covering 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 being coated with the coating layer 12 may be subjected to a surface treatment to improve adhesion to the fluororesin coating layer 12. By performing such a surface treatment on the surface of the string-shaped core material 11 before being 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 having a thickness of 0.20 mm or less can be suppressed. Examples of such surface treatments include a primer treatment, an Itro treatment, and a plasma treatment.

[0061] In the manufacturing method of the O-ring 10 according to the embodiment, before coating the string-shaped core material 11, the surface of the molten fluororesin R that is to come into contact with the string-shaped core material 11 may be subjected to plasma treatment in order to improve adhesion to the string-shaped core material 11. As a result of this, the surface of the coating layer 12 that comes into contact with the core material 11 is subjected to plasma treatment, which not only improves the adhesion of the fluororesin coating layer 12 to the core material 11 but also suppresses the occurrence of wrinkles on the surface of the coating layer 12.

[0062] It should be noted that the above-described embodiments 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' Rubber string 10 O-ring (sealing material) 11 Core material 12 Covering layer 13,113 Uneven surface 14 Connection 15 Fluorine resin film 20 Heating device 21 Mold 22 High frequency coil

Claims

1. A string-shaped rubber of a predetermined length covered with a fluorine-based resin having a thickness of 0.20 mm or less is prepared, Joining the connecting surfaces of the rubber strings, At least the outer periphery of the connecting surface of the rubber string is covered with a fluororesin film made of the same material as the fluororesin, placing only the connection portion covered with the fluororesin film and the periphery of the connection portion in a mold groove of a mold; The mold is closed to sandwich the connection portion; The mold is placed inside a high-frequency coil; high-frequency induction heating is performed to melt the fluororesin film to form a fluororesin coating; The mold is cooled and the annular seal is removed. A method for producing a sealing material comprising the steps of:

2. When high-frequency induction heating is performed, the mold groove is disposed outside the high-frequency coil. The method for manufacturing a sealing material according to claim 1 .

3. The mold is made of a magnetic material.

3. The method for manufacturing a sealing material according to claim 1 or 2.

4. The rubber string is made of silicone rubber.

3. The method for manufacturing a sealing material according to claim 1 or 2.

5. The fluorine-based resin contains a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin.

3. The method for manufacturing a sealing material according to claim 1 or 2.

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