Method of manufacturing seal 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 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] An object of the present invention is to provide a method for producing a sealing material that suppresses the occurrence of wrinkles on the surface of a thin coating layer. [Means for solving the problem]

[0005] The present invention is a method for manufacturing a sealing material, which comprises 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 converting the string-shaped core material into a long wire material coated with a coating layer of fluororesin having a thickness of 0.20 mm or less, cutting a predetermined length from the wire material, and joining both ends to form a ring, and before coating the string-shaped core material, applying plasma treatment to the surface of the molten fluororesin that is scheduled to come into contact with the string-shaped core material. [Effects of the Invention]

[0006] According to the present invention, by performing plasma treatment on the surface of the molten fluororesin that is 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 drawings]

[0007] [Figure 1] FIG. 2 is a cross-sectional view of an O-ring according to an embodiment. [Figure 2] 5A to 5C are explanatory views showing a method for manufacturing an O-ring according to an embodiment. [Figure 3] 1 is a cross-sectional view of a head used in a method for manufacturing an O-ring according to an embodiment. [Figure 4] 10A and 10B are explanatory views showing a first modified example of the method for manufacturing an O-ring according to the embodiment. [Figure 5] 10A and 10B are explanatory views showing a second modified example of the method for manufacturing an O-ring according to the embodiment. [Figure 6] 10A and 10B are explanatory views showing a third modified example of the method for manufacturing an O-ring according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0009] 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, and is, for example, an inner diameter of 30 mm to 500 mm and a thickness of 2 mm to 10 mm.

[0010] The O-ring 10 according to the embodiment includes an annular core 11 and a coating layer 12 that coats the core 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.

[0011] 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.

[0012] 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, since 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, and 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.

[0013] 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.

[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 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.

[0015] 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.

[0016] From the viewpoint of not requiring a large tightening force during installation, the hardness of the O-ring 10 according to the embodiment is preferably A60 to A80, more preferably A65 to A77. 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, and more preferably 2.0 N / mm or less, from the viewpoint 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 circumferential length, that is, the sum of the inner diameter and thickness multiplied by pi.

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

[0019] First, prepare the string-shaped core material 11. The string-shaped core material 11 made of rubber can be prepared by extrusion molding, for example.

[0020] Next, as shown in Figure 2, the string-like core material 11 is passed through a head 20 attached to an extrusion molding machine (not shown), and a long wire 10' is produced by using a so-called coating extrusion molding method to coat the surface of the string-like core material 11 with a coating layer 12 of fluorine-based resin along its length.

[0021] FIG. 3 shows the head 20. The head 20 has a head body front portion 21 on the front side (downstream side) and a head body rear portion 22 on the rear side (upstream side). The head body front portion 21 and the head body rear portion 22 are arranged so as to overlap in the front-to-rear direction. A molten resin inlet passage 23 communicating with the extruder is formed between the head body front portion 21 and the head body rear portion 22. A large-diameter cylindrical hole 211 is formed in the head body front portion 21 and penetrates therethrough in the front-to-rear direction, and a small-diameter cylindrical hole 221 is formed coaxially in the head body rear portion 22 and penetrates therethrough in the front-to-rear direction. An annular die 24 having a through-hole 241 formed in its center is coaxially fitted into the large-diameter cylindrical hole 211 of the head body front portion 21. The die 24 is arranged so as to protrude slightly forward from the head body front portion 21. The through-hole 241 of the die 24 is composed of a front cylindrical hole 241a followed by a rear truncated conical hole 241b whose inner diameter gradually increases toward the rear. A metallic cylindrical nipple 25 is coaxially fitted into the small-diameter cylindrical hole 221 of the head body rear portion 22. The nipple 25 extends forward from the rear end of the head body rear portion 22 and is inserted into the through-hole 241 of the die 24 fitted into the head body front portion 21 so as to leave a uniform gap around the entire circumference between the nipple 25 and its inner peripheral surface, and the nipple 25 protrudes forward from the die 24. The area defined by the front surface of the head body rear portion 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 constitutes a molten resin flow zone 26. The molten resin flow zone 26 is connected to the molten resin inlet channel 23. An annular plasma electrode 27 is provided so as to surround the portion of the nipple 25 that protrudes from the die 24. The nipple 25 and the plasma electrode 27 are each connected to a plasma generator .

[0022] When the string-shaped core material 11 is coated with the fluororesin coating layer 12, the string-shaped core material 11 is inserted through a nipple 25 and moved forward (downstream) along its length at a constant speed. Molten fluororesin R is supplied from the extruder to a die 24. Specifically, the molten fluororesin R is supplied to a molten resin flow section 26 through a molten resin inlet channel 23 of the die 24, allowed to flow forward, and then discharged in a cylindrical form from an annular opening between the die 24 and the nipple 25 at the front side so as to coat the outer circumferential surface of the nipple 25. The molten fluororesin R discharged from the die 24 is then moved forward on the outer circumferential surface of the nipple 25, and at its front end, is transferred onto the outer circumferential surface of the string-shaped core material 11 being fed out of the nipple 25, continuously coating the outer circumferential surface of the string-shaped core material 11. The molten fluororesin R is then stretched and sent forward in this state, where it is cooled in a cooling section 30 provided downstream to form the coating layer 12. As a result, the string-like core material 11 is made into a long wire material 10' covered with the covering layer 12 along its length, and the wire material 10' is wound around a bobbin or the like and collected.

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

[0024] Then, a predetermined length is cut out from the recovered wire rod 10', and both ends are joined to form a ring to manufacture the O-ring 10. Examples of means for joining both ends of the wire rod 10' include a method of butting both end faces together, or forming fitting structures at both ends and heating and melting them to join them by thermal fusion, and a method of joining them using an adhesive.

[0025] In the method for manufacturing the O-ring 10 according to the embodiment, a plasma treatment is additionally performed on the surface of the molten fluorine-based resin R that is to come into contact with the string-shaped core material 11 before the string-shaped core material 11 is covered.

[0026] Specifically, nipple 25 is used as one of the plasma electrodes, and plasma generator 28 applies high frequency and high voltage between nipple 25 and plasma electrode 27 to generate plasma therebetween. During this process, cylindrical molten fluororesin R moves through the annular space between nipple 25 and plasma electrode 27, covering and in contact with the outer circumferential surface of nipple 25, and plasma treatment is continuously performed along the length direction on the inner circumferential surface of cylindrical molten fluororesin R, which is the surface intended to come into contact with string-like core material 11, by plasma generated in the minute space between molten fluororesin R and nipple 25. This plasma treatment introduces functional groups that enhance adhesion to string-like core material 11 into the surface of molten fluororesin R intended to come into contact with string-like core material 11.

[0027] According to the manufacturing method of the O-ring 10 of the embodiment, by performing plasma treatment on 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, 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 having a thickness of 0.20 mm or less can be suppressed.

[0028] 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 enhance adhesion with the fluororesin coating layer 12. Examples of surface treatments include primer treatment, Itro treatment, and plasma treatment. This surface treatment enhances adhesion between the core material 11 and the fluororesin coating layer 12, thereby suppressing the occurrence of wrinkles on the surface of the thin coating layer 12 having a thickness of 0.20 mm or less. By performing this surface treatment on the string-shaped core material 11 in addition to the plasma treatment on the molten fluororesin R, it is possible to more effectively improve 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 by so-called batch processing, but is preferably carried out continuously along the length direction of the string-shaped core material 11. In particular, from the viewpoint of increasing productivity, when the string-shaped core material 11 is coated with the coating layer 12 continuously along the length direction, it is more preferable to carry out the surface treatment continuously along the length direction of the core material 11 on the upstream side of the processing.

[0030] Specifically, in the case of primer treatment, as shown in Fig. 4, after spraying primer onto the surface of the string-like core material 11 from a spray nozzle 31 provided upstream of the head 20, hot air is blown onto the primer adhering to the surface of the string-like core material 11 from a heater 32 provided between the spray nozzle 31 and the head 20 to dry it. Note that the primer can also be applied to the surface of the string-like core material 11 by brush coating or roll coating.

[0031] In the case of the Itro treatment, as shown in FIG. 5, a flame containing silane compound gas is applied to the surface of the string-like core material 11 from a burner 33 provided on the upstream side of the head 20 .

[0032] In the case of plasma treatment, as shown in Fig. 6, plasma is irradiated onto the surface of the string-shaped core material 11 from a plasma electrode 34 provided upstream of the head 20. This plasma irradiation introduces functional groups into the surface of the string-shaped core material 11 that improve adhesion with the fluororesin coating layer 12. In this case, either a remote type in which plasma generated by the plasma electrode 34 is sprayed onto the surface of the string-shaped core material 11 by a gas flow, or a direct type in which the string-shaped core material 11 is placed in a plasma space generated by the plasma electrode 34 and directly irradiated with plasma may be used.

[0033] In the above embodiment, the O-ring 10 is shown as an example of the sealing material, but the present invention is not particularly limited to this, and any other annular sealing material may be used. [Industrial Applicability]

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

[0035] 10 O-ring (sealing material) 10' wire rod 11 Core material 12 Covering layer 20 heads 21 Front of head body 211 Large diameter cylindrical hole 22 Rear of head body 221 Small diameter cylindrical hole 23 Molten resin inlet 24 Die 241 Through hole 241a Cylindrical hole 241b truncated cone foramen 25 Nipple (cylindrical member) 26 Molten resin flow section 27 Plasma electrode 28 Plasma Generator 30 Cooling section 31 spray nozzle 32 Heater 33 Burner 34 Plasma electrode R Molten fluororesin

Claims

1. A method for manufacturing a sealing material, comprising the steps of: moving a string-shaped core material along a lengthwise direction; continuously coating an outer circumferential surface of the string-shaped core material with molten fluororesin; and cooling the core material to form a long wire material coated with a coating layer of the fluororesin having a thickness of 0.20 mm or less; cutting a predetermined length from the wire material; and joining both ends of the cut wire material to form a ring shape; A method for manufacturing a sealing material, comprising: subjecting a surface of the molten fluorine-based resin to be in contact with the string-shaped core material to plasma treatment before covering the string-shaped core material.

2. 2. The method for producing a sealing material according to claim 1, A method for manufacturing a sealing material, comprising inserting the string-shaped core material into a tubular member and moving it along the lengthwise direction, causing the molten fluororesin to flow out of a die in a tubular shape so as to cover the outer surface of the tubular member, moving it over the outer surface of the tubular member, and at its end, transferring it onto the outer surface of the string-shaped core material being fed out of the tubular member.

3. 3. The method for producing a sealing material according to claim 2, A method for manufacturing a sealing material using the cylindrical member as a plasma electrode.

4. 2. The method for producing a sealing material according to claim 1, The method for manufacturing a sealing material, wherein the sealing material is an O-ring.

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