Manufacturing method of sealing material

Abstract

To suppress the occurrence of wrinkles on the surface of a thin coating layer.SOLUTION: In a method of manufacturing a seal material, a string-like core material 11 is moved lengthwise. By continuously coating and cooling the outer peripheral surface of a string-like core material 11 with a molten fluorine-based resin, the string-like core material 11 is formed into a long wire rod 10' with a coating layer of fluorine-based resin having a thickness of 0.20 mm or less. The wire rod 10' is cut to a predetermined length, and its opposite ends are joined to form a ring shape. The surface of the string-like core material 11 prior to coating with the coating layer is subjected to surface treatment to enhance adhesiveness with the coating layer.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for manufacturing 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 a 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] An object of the present invention is to provide a method for manufacturing a sealing material that suppresses the generation of wrinkles on the surface of a thin coating layer.

Means for Solving the Problems

[0005] The present invention moves a string-shaped core material along the length direction, continuously coats the outer peripheral surface of the string-shaped core material with a molten fluororesin and cools it, thereby obtaining a long wire material in which the string-shaped core material is coated with a coating layer having a thickness of 0.20 mm or less of the fluororesin, cutting out a predetermined length from the wire material, and joining both ends thereof to form an annular shape. In the method for manufacturing a sealing material, a surface treatment for enhancing the adhesion to the coating layer is performed on the surface of the string-shaped core material before being coated with the coating layer.

Effects of the Invention

[0006] According to the present invention, by applying a surface treatment to the surface of the string-shaped core material before coating it with the coating layer, the adhesion between the core material and the fluororesin coating layer is improved, and as a result, the occurrence of wrinkles on the surface of a thin coating layer with a thickness of 0.20 mm or less can be suppressed. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view of an O-ring according to an embodiment. [Figure 2] This is an explanatory diagram showing a method for manufacturing an O-ring according to an embodiment. [Figure 3] This is a cross-sectional view of a head used in the O-ring manufacturing method according to the embodiment. [Figure 4] This is an explanatory diagram showing an example of primer treatment in the manufacturing method of an O-ring according to the embodiment. [Figure 5] This is an explanatory diagram showing an example of the Itro treatment in the O-ring manufacturing method according to the embodiment. [Figure 6] This is an explanatory diagram showing an example of plasma treatment in the O-ring manufacturing method according to the embodiment. [Figure 7] This is a cross-sectional view of a modified head used in the method for manufacturing an O-ring according to the embodiment. [Modes for carrying out the invention]

[0008] The embodiments will be described in detail below.

[0009] Figure 1 shows an O-ring 10 (sealing material) according to an 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.

[0010] The O-ring 10 according to this embodiment comprises an annular core material 11 and a coating layer 12 that covers 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.

[0011] 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.

[0012] 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 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 for the core material 11 before coating with the coating layer 12.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] From the perspective that the linear load at 25% compression of the O-ring 10 according to the embodiment does not require a large tightening force during installation, it is preferably 3.0 N / mm or less, more preferably 2.0 N / mm or less. This linear 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 circumference, that is, the sum of the inner diameter and the thickness multiplied by the pi (π).

[0018] Next, a manufacturing method of the O-ring 10 according to the embodiment will be described.

[0019] First, a string-shaped core material 11 is produced. The string-shaped core material 11 made of rubber can be produced, for example, by extrusion molding.

[0020] Subsequently, as shown in FIG. 2, while passing the string-shaped core material 11 through a head 20 attached to an extrusion molding machine (not shown), a long wire 10' is produced by coating the surface of the string-shaped core material 11 with a fluororesin coating layer 12 along its length direction by a so-called coating extrusion molding method.

[0021] Figure 3 shows the head 20. The head 20 has a front (downstream) head body front portion 21 and a rear (upstream) head body rear portion 22. These front 21 and rear 22 head bodies are arranged to overlap in the front-rear direction. A molten resin inlet passage 23, which communicates with the extrusion molding machine, is formed between the front 21 and rear 22 head bodies. A large-diameter cylindrical hole 211 is provided through the front 21 head body, and a small-diameter cylindrical hole 221 is provided through the rear 22 head body, coaxially with the front 21. An annular die 24 with a through hole 241 in the center is coaxially fitted into the large-diameter cylindrical hole 211 of the front 21 head body. The die 24 is provided so as to protrude slightly forward from the front 21 head body. The through-hole 241 of the die 24 is composed of a front cylindrical hole 241a and a rear frustoconical hole 241b whose inner diameter gradually increases towards the rear. A cylindrical nipple 25 is coaxially fitted into a small-diameter cylindrical hole 221 in the rear part 22 of the head body. The nipple 25 extends forward from the rear end of the rear part 22 of the head body and is inserted into the through-hole 241 of the die 24 fitted into the front part 21 of the head body, such that there is a uniform circumferential gap around its entire circumference between it and its inner circumferential surface, and is positioned flush with the front surface of the die 24. The area partitioned by the front surface of the rear part 22 of the head body, the rear surface of the die 24, the inner circumferential surface of the through-hole 241, and the outer circumferential surface of the nipple 25 constitutes a molten resin flow section 26. The molten resin flow section 26 is in communication with a molten resin inflow passage 23.

[0022] When coating the string-shaped core material 11 with a fluororesin coating layer 12, the string-shaped core material 11 is inserted through the nipple 25 and moved forward (downstream) along its length at a constant speed. Molten fluororesin R is supplied from the extrusion molding machine to the die 24. Specifically, the molten fluororesin R is supplied to the molten resin flow section 26 via the molten resin inlet passage 23 of the die 24 and allowed to flow forward, then flows out in a cylindrical shape from the annular opening between the front of the die 24 and the nipple 25. Next, the molten fluororesin R flowing out of the die 24 continuously coats the outer surface of the string-shaped core material 11 being fed out from the nipple 25, and is then stretched and fed forward while in this state, and cooled in the cooling section 30 provided on the downstream side to form the coating layer 12. As a result, the string-shaped core material 11 is made into a long wire 10' with the coating layer 12 covering its length, and this wire 10' is wound onto a bobbin or the like for recovery.

[0023] At this time, the moving speed of the string-shaped core material 11 is preferably 10 m / min or more, more preferably 15 m / min or more, and even more preferably 20 m / min or more, from the viewpoint of forming a thin coating layer 12. From the viewpoint of processability, the moving speed of the string-shaped core material 11 is preferably 50 m / min or less. From the viewpoint of forming a thin coating layer 12, the preheating temperature of the string-shaped core material 11 is preferably 50°C to 150°C, more preferably 80°C to 120°C. From the same viewpoint, the temperature of the molten fluororesin R is preferably 280°C to 400°C, more preferably 300°C to 380°C. From the same viewpoint, the dimension of the gap in the annular opening between the front surface of the die 24 and the nipple 25 is preferably 0.5 mm to 5 mm, more preferably 1 mm to 3 mm.

[0024] Then, an O-ring 10 is manufactured by cutting a predetermined length from the recovered wire 10' and joining both ends to form a ring. Examples of joining methods for both ends of the wire 10' include butting the end faces together or forming a fitting structure at both ends and joining them by heat fusion through heating and melting, or joining them via an adhesive.

[0025] In the manufacturing method of the O-ring 10 according to the embodiment, in addition, the surface of the string-shaped core material 11 before it is covered with the coating layer 12 is subjected to a surface treatment to improve adhesion with the fluororesin coating layer 12.

[0026] According to the manufacturing method of the O-ring 10 according to this embodiment, by applying the surface treatment to the surface of the string-shaped core material 11 before it is covered 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, which has a thickness of 0.20 mm or less, can be suppressed. Examples of such surface treatments include primer treatment, Itro treatment, plasma treatment, etc.

[0027] This surface treatment may be carried out in a so-called batch process, but it is preferable to carry it out continuously along the length of the string-shaped core material 11. In particular, from the viewpoint of increasing productivity, when the string-shaped core material 11 is continuously coated with a coating layer 12 along its length, it is even more preferable to carry out the surface treatment continuously along the length of the core material 11 upstream of the processing.

[0028] Specifically, in the case of priming, as shown in Figure 4, the primer is sprayed onto the surface of the string-shaped core material 11 from a spray nozzle 31 located upstream of the head 20, and then hot air is blown onto the primer adhering to the surface of the string-shaped core material 11 from a heater 32 located between the spray nozzle 31 and the head 20 to dry it. The primer can also be applied to the surface of the string-shaped core material 11 by brushing or rolling.

[0029] In the case of the Itro treatment, as shown in Figure 5, a flame containing a silane compound gas is applied to the surface of the string-shaped core material 11 from a burner 33 located upstream of the head 20.

[0030] In the case of plasma processing, as shown in Figure 6, plasma is irradiated onto the surface of the string-shaped core material 11 from a plasma electrode 34 located upstream of the head 20. This plasma irradiation introduces functional groups onto the surface of the string-shaped core material 11 that enhance adhesion with the fluororesin coating layer 12. In this case, it is possible to use either a remote type, where the plasma generated by the plasma electrode 34 is blown onto the surface of the string-shaped core material 11 by a gas flow, or a direct type, where the string-shaped core material 11 is placed in the plasma space generated by the plasma electrode 34 and the plasma is irradiated directly onto it.

[0031] In the manufacturing method of the O-ring 10 according to this embodiment, in addition to surface treatment of the string-shaped core material 11, plasma treatment may be applied to the surface of the molten fluororesin R 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. This plasma treatment improves the adhesion of the fluororesin coating layer 12 to the core material 11, and as a result, it is possible to suppress the occurrence of wrinkles on the surface of the thin coating layer 12, which has a thickness of 0.20 mm or less. In this way, by performing plasma treatment on the molten fluororesin R in addition to surface treatment of the string-shaped core material 11, it is possible to more effectively improve the adhesion between the string-shaped core material 11 and the fluororesin coating layer 12 and suppress the occurrence of wrinkles on the surface of the coating layer 12.

[0032] When applying plasma treatment to the contact surface of a string-shaped core material 11 made of molten fluororesin R, a head 20 as shown in Figure 7 can be used. In this head 20, a metal nipple 25 is provided so as to protrude forward from a die 24, and an annular plasma electrode 27 is provided so as to surround the portion of the nipple 25 that protrudes from the die 24. Both the nipple 25 and the plasma electrode 27 are connected to a plasma generator 28. Using the nipple 25 as one of the plasma electrodes, the plasma generator 28 applies high frequency and high voltage between the nipple 25 and the plasma electrode 27 to generate plasma between them.

[0033] When coating the string-shaped core material 11 with a fluororesin coating layer 12, the molten fluororesin R is supplied to the molten resin flow section 26 via the molten resin inlet passage 23 of the die 24 and allowed to flow forward. Then, it is allowed to flow out in a cylindrical shape from the annular opening between the die 24 and the nipple 25 on the front surface of the die 24, so as to cover the outer surface of the nipple 25. Next, the molten fluororesin R that has flowed out of the die 24 is moved forward along the outer surface of the nipple 25. At this time, the cylindrical molten fluororesin R moves in the annular space between the nipple 25 and the plasma electrode 27, covering and contacting the outer surface of the nipple 25. The plasma generated in the minute space between the molten fluororesin R and the nipple 25 continuously performs plasma treatment along the length direction on the inner surface of the cylindrical molten fluororesin R, which is the surface intended to contact with the string-shaped core material 11. This plasma treatment introduces functional groups that enhance adhesion with the string-shaped core material 11 to the surface of the molten fluororesin R that is intended to come into contact with the string-shaped core material 11. Next, the molten fluororesin R in a cylindrical shape, whose inner surface has been plasma-treated, is transferred at the front end of the nipple 25 onto the outer surface of the string-shaped core material 11 being fed out of the nipple 25, thereby continuously coating the outer surface of the string-shaped core material 11. While being stretched in this state, it is fed forward and cooled in the cooling section 30 located downstream to form a coating layer 12.

[0034] In the above embodiment, the O-ring 10 is shown as an example of a sealing material, but it is not limited to this, and any annular sealing material may be used. [Industrial applicability]

[0035] This invention is useful in the technical field of methods for manufacturing sealing materials. [Explanation of Symbols]

[0036] 10 O-rings (sealants) 10' wire rod 11 Core material 12 Covering layer 20 heads 21 Front of the head body 211 Large diameter cylindrical bore 22 Rear of the head body 221 Small diameter cylindrical bore 23 Molten resin inflow passage 24 Dies 241 Through hole 241a Cylindrical bore 241b frustoconical hole 25 Nipple (cylindrical member) 26 Molten resin flow section 27 Plasma electrodes 28 Plasma Generator 30 Cooling section 31 Spray nozzle 32 Heater 33 burners 34 Plasma electrodes R Molten fluororesin

Claims

1. A method for manufacturing a sealing material, comprising moving a string-shaped core material along its length, continuously coating the outer surface of the string-shaped core material with molten fluororesin and cooling it, thereby creating a long wire material in which the string-shaped core material is coated with a coating layer of fluororesin with a thickness of 0.20 mm or less, cutting a predetermined length from the wire material, and joining both ends to form a ring, A method for manufacturing a sealing material, comprising applying a surface treatment to the surface of the string-shaped core material before covering it with the coating layer in order to improve its adhesion to the coating layer.

2. In the method for manufacturing a sealing material described in claim 1, A method for manufacturing a sealing material, comprising inserting the string-like core material into a cylindrical member and moving it along its length, flowing the molten fluororesin out of a die in a cylindrical shape so as to cover the outer surface of the cylindrical member and moving it along the outer surface of the cylindrical member, and at its end transferring it onto the outer surface of the string-like core material being fed out of the cylindrical member.

3. In the method for manufacturing a sealing material described in claim 1, A method for manufacturing a sealing material, comprising performing the aforementioned surface treatment continuously along the length direction of the string-shaped core material.

4. In the method for manufacturing a sealing material described in claim 3, A method for manufacturing a sealing material, wherein the surface treatment is performed upstream of the process of continuously covering the string-shaped core material with a coating layer along its length.

5. In the method for manufacturing a sealing material described in claim 1, A method for manufacturing a sealing material, wherein the surface treatment is a primer treatment, an Itro treatment, or a plasma treatment.

6. In the method for manufacturing a sealing material described in claim 1, A method for manufacturing a sealing material in which the sealing material is an O-ring.

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