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 with a coating layer of fluorine-based resin having a thickness of 0.20 mm or less. The wire rod is cut to a predetermined length, and its opposite ends are joined to form a ring shape. Before covering the string-shaped core material 11, the surface of the molten fluorine-based resin R that will contact the string-like core material 11 is subjected to plasma treatment.SELECTED DRAWING: Figure 3

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 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] 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 and cools the outer peripheral surface of the string-shaped core material with a molten fluororesin, thereby obtaining a long wire material in which the string-shaped core material is coated with a coating layer having a fluororesin thickness of 0.20 mm or less, cutting out a predetermined length from the wire material, and joining both ends thereof to form an annular shape. The method for manufacturing a sealing material is characterized in that a plasma treatment is performed on a surface of the molten fluororesin that is a planned contact surface with the string-shaped core material before coating the string-shaped core material.

Effects of the Invention

[0006] According to the present invention, by applying plasma treatment to the surface of the molten fluororesin intended to come into contact with the string-shaped core material before coating the string-shaped core material, the adhesion of the fluororesin coating layer to the core material 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 method for manufacturing an O-ring according to the embodiment. [Figure 4] This is an explanatory diagram showing a first modified example of the method for manufacturing an O-ring according to the embodiment. [Figure 5] This is an explanatory diagram showing a second modified example of the method for manufacturing an O-ring according to the embodiment. [Figure 6] This is an explanatory diagram showing a third modified example of 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, and from the perspective 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 still more preferably 0.06 mm or less. On the other hand, the thickness of the coating layer 12 is preferably 0.02 mm or more, more preferably 0.03 mm or more, from the perspective of the workability of coating the core material 11 with the fluororesin coating layer 12.

[0015] The ratio of the thickness of the coating layer 12 to the thickness of the O-ring 10 is preferably 7% or less, more preferably 6% or less, still more preferably 4% or less, and even more preferably 2% or less, from the perspective of not requiring a large tightening force during installation. The ratio of the thickness of the coating layer 12 to the thickness of the O-ring is preferably 0.5% or more, more preferably 1% or more, from the perspective of the workability of coating the core material 11 with the fluororesin coating layer 12.

[0016] The hardness of the O-ring 10 according to the embodiment is preferably A60 or more and A80 or less, more preferably A65 or more and A77 or less, from the perspective 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.

[0017] The line load at 25% compression of the O-ring 10 according to the embodiment is preferably 3.0 N / mm or less, more preferably 2.0 N / mm or less, from the perspective of not requiring a large tightening force 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 circumference, that is, the sum of the inner diameter and the thickness multiplied by the circumference ratio π.

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

[0019] First, a string-shaped core material 11 is produced. The rubber string-shaped core material 11 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] Fig. 3 shows the head 20. The head 20 has a front (downstream side) head body front part 21 and a rear (upstream side) head body rear part 22. These head body front part 21 and head body rear part 22 are provided so as to overlap in the front-rear direction. A molten resin inflow path 23 communicating with the extrusion molding machine is formed between the head body front part 21 and the head body rear part 22. A large-diameter cylindrical hole 211 is provided penetrating in the front-rear direction in the head body front part 21, and coaxially with it, a small-diameter cylindrical hole 221 is provided penetrating in the front-rear direction in the head body rear part 22. An annular die 24 having a through-hole 241 provided at the center is coaxially fitted inside the large-diameter cylindrical hole 211 of the head body front part 21. The die 24 is provided so as to slightly protrude forward from the head body front part 21. The through-hole 241 of the die 24 is composed of a front cylindrical hole 241a and a rear frustum-shaped hole 241b whose inner diameter gradually expands as it goes backward. A metal nipple 25 of a cylindrical member is coaxially fitted inside the small-diameter cylindrical hole 221 of the head body rear part 22. The nipple 25 extends forward from the rear end of the head body rear part 22 and is inserted into the through-hole 241 of the die 24 fitted inside the head body front part 21 so as to have a uniform circumferential gap over the entire circumference between its inner peripheral surface, and is provided so as to protrude forward from the die 24. The region defined by the front surface of the head body rear part 22, the rear surface of the die 24, the inner peripheral surface of the through-hole 241, and the outer peripheral surface of the nipple 25 is formed as a molten resin flow part 26. The molten resin flow part 26 communicates with the molten resin inflow path 23. An annular plasma electrode 27 is provided so as to surround the portion of the nipple 25 protruding from the die 24. Each of the nipple 25 and the plasma electrode 27 is connected to a plasma generator 28.

[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 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, and at its front end, it is transferred onto the outer surface of the string-shaped core material 11 being fed out of the nipple 25 to continuously coat the outer surface of the string-shaped core material 11. While stretching it in this state, it is sent forward and cooled in the cooling section 30 provided on the downstream side to form the coating layer 12. This creates a long wire 10' by covering the string-like core material 11 with a coating layer 12 along its length, and then winding the wire 10' 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, plasma treatment is performed on the surface of the molten fluororesin R that is intended to come into contact with the string-shaped core material 11 before covering the string-shaped core material 11.

[0026] Specifically, the nipple 25 is used as one of the plasma electrodes, and a plasma generator 28 applies high frequency and high voltage between the nipple 25 and the plasma electrode 27 to generate plasma between them. During this time, the cylindrical molten fluororesin R moves through 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 intended to contact with the string-shaped core material 11.

[0027] According to the manufacturing method of the O-ring 10 according to the embodiment, by applying plasma treatment to the surface of the molten fluororesin R that is to come into contact with the string-shaped core material 11 before covering the string-shaped core material 11, the adhesion of the fluororesin coating layer 12 to the core material 11 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.

[0028] In the manufacturing method of the O-ring 10 according to this embodiment, the surface of the string-shaped core material 11 before coating with the coating layer 12 may be subjected to a surface treatment to improve adhesion with the fluororesin coating layer 12. Examples of surface treatments include primer treatment, Itro treatment, and plasma treatment. This surface treatment improves the adhesion of the core material 11 to the fluororesin coating layer 12, 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. By performing a surface treatment on the string-shaped core material 11 in addition to plasma treatment on the molten fluororesin R in this way, 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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]

[0034] This invention is useful in the technical field of methods for manufacturing sealing materials. [Explanation of symbols]

[0035] 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 plasma treatment to the surface of the molten fluororesin that is intended to come into contact with the string-shaped core material before covering the string-shaped core material.

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 2, A method for manufacturing a sealing material using the aforementioned cylindrical member as a plasma electrode.

4. 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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