Fluororesin film, rubber molded article, and method for manufacturing a rubber molded article

Abstract

The present invention provides a fluororesin film that can be used as a coating film to cover the surface of a rubber-containing substrate in a rubber molded article, and is suitable for manufacturing rubber molded articles having a surface covered by the film. [Solution] The fluororesin film contains a fluororesin, and the average value of the tensile elongation at break in a first in-plane direction and the tensile elongation at break in a second direction perpendicular to the first in-plane direction, under an atmosphere of 180°C, is 1200% or more. This fluororesin film can be used as a coating film to cover the surface of a rubber-containing substrate in a rubber molded article, and is suitable for manufacturing rubber molded articles having a surface covered by this film.

Description

Technical Field

[0001] The present invention relates to a fluororesin film, a rubber molded body, and a method for producing the rubber molded body.

Background Art

[0002] Since the fluororesin film is chemically stable, it is used as a film for coating the surface of a rubber-containing substrate. A rubber molded body including a rubber-containing substrate and a fluororesin film coating its surface is used as a diaphragm, a roller, a sealing material, or the like. Patent Document 1 discloses a diaphragm whose surface is coated with a fluororesin film. The diaphragm of Patent Document 1 has high durability against ozone and fuel in the atmosphere.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] If rubber is shaped in a state where a fluororesin film is placed in a mold, formation of a rubber-containing substrate and coating with the fluororesin film can be carried out simultaneously, and a rubber molded body can be efficiently produced. However, in the above shaping process, the fluororesin film coating the rubber-containing substrate may be torn. Further, according to the study by the present inventors, tearing is particularly likely to occur when coating the surface of a convex portion protruding from the base of the rubber-containing substrate.

[0005] An object of the present invention is to provide a fluororesin film that can be used as a coating film for coating the surface of a rubber-containing substrate included in a rubber molded body and is suitable for producing a rubber molded body having a surface coated with the film. [Means for solving the problem]

[0006] The present invention Contains fluororesin, A fluoropolymer film in which the average value of the tensile elongation at break in a first in-plane direction and the tensile elongation at break in a second direction perpendicular to the first direction in the in-plane, under an atmosphere of 180°C, is 1200% or more. To provide.

[0007] In another aspect, the present invention is It comprises a rubber-containing substrate and a resin film, The rubber-containing substrate has a surface covered by the resin film, The resin film is a fluororesin film of the present invention, a rubber molded body, To provide.

[0008] In another aspect, the present invention is A method for manufacturing a rubber molded article comprising a resin film and a rubber-containing substrate, wherein the rubber-containing substrate has a surface covered by the resin film, This includes shaping the rubber while the resin film is placed inside the mold to obtain the rubber molded body, The resin film is the fluororesin film of the present invention described above. Method for manufacturing a rubber molded body, To provide.

[0009] In another aspect, the present invention is A method for manufacturing a rubber molded article comprising a resin film and a rubber-containing substrate, wherein the rubber-containing substrate has a surface covered by the resin film, In the aforementioned rubber molded body, The aforementioned resin film is a fluororesin film and is free from tears. The aforementioned surface includes the surface of the protrusions that extend from the base of the rubber-containing substrate. The aforementioned protrusion has a height of 10 mm or more. The resin film covers the convex portion in the height direction of the convex portion from the top of the convex portion. The manufacturing method includes obtaining the rubber molded body by shaping rubber in a state where the fluororesin film of the present invention is disposed in a mold. A method for manufacturing a rubber molded body is provided.

[0010] In another aspect, the present invention is a method for manufacturing a rubber molded body including a resin film and a rubber-containing base material, wherein the rubber-containing base material has a surface covered by the resin film. In the rubber molded body, the resin film is a fluororesin film without cracks. The surface includes the surface of a convex portion protruding from the base of the rubber-containing base material. The convex portion has a height of 10 mm or more. The resin film covers the convex portion in the height direction of the convex portion from the top of the convex portion. The manufacturing method includes obtaining the rubber molded body by shaping rubber in a state where the resin film is disposed in a mold. As the resin film, a resin film having an elongation at break without cracking when changed from a film state to a shape along the concave portion corresponding to the convex portion in the depth direction of the concave portion of the mold is used. A method for manufacturing a rubber molded body is provided.

Advantages of the Invention

[0011] The fluororesin film of the present invention having the above elongation at break is suitable for manufacturing a rubber molded body having a surface covered by the film.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of the fluororesin film of the present invention. [Figure 2] Figure 2 is a schematic diagram showing an example of an apparatus capable of manufacturing the fluororesin film of the present invention. [Figure 3A] Figure 3A is a plan view schematically showing an example of the rubber molded body of the present invention. [Figure 3B] Figure 3B is a cross-sectional view showing the cross-section IIIB-IIIB of the rubber molded body of Figure 3A. [Figure 4A] Figure 4A is a plan view schematically showing an example of the rubber molded body of the present invention. [Figure 4B] Figure 4B is a cross-sectional view showing the cross-section IVB-IVB of the rubber molded body of Figure 4A. [Figure 5A] Figure 5A is a plan view schematically showing an example of the rubber molded body of the present invention. [Figure 5B] Figure 5B is a cross-sectional view showing the cross-section VB-VB of the rubber molded body of Figure 5A. [Figure 6] Figure 6 is an observation image showing the state of the fluororesin film of Example 1 after the shaping test. [Figure 7] Figure 7 is an observation image showing the state of the fluororesin film of Comparative Example 1 after the shaping test.

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

[0014] [Fluororesin Film] The fluororesin film of this embodiment is shown in FIG. 1. The fluororesin film 1 of FIG. 1 contains a fluororesin. For the fluororesin film 1, the average value (hereinafter referred to as the average elongation) of the tensile break elongation in the first in-plane direction and the tensile break elongation in the second direction orthogonal to the first direction in the plane under an atmosphere of 180°C is 1200% or more. According to the fluororesin film 1, it is possible to suppress the occurrence of tearing in the film 1 during the shaping process of the above rubber. Note that 180°C corresponds to a typical processing temperature in the shaping process of rubber.

[0015] The average growth rate may be 1250% or more, 1300% or more, 1350% or more, 1400% or more, 1450% or more, 1500% or more, 1550% or more, 1600% or more, 1650% or more, or even 1700% or more. The upper limit of the average growth rate is, for example, 1800% or less.

[0016] The first direction is, for example, the MD direction. The second direction is, for example, the TD direction. The MD direction is typically the winding direction when the fluororesin film 1 is formed. The TD direction is typically the direction perpendicular to the winding direction in the plane of the fluororesin film 1. For a strip-shaped fluororesin film 1, the first and second directions may be the longitudinal direction and the width direction, respectively.

[0017] For the fluororesin film 1, the tensile strength in the first and / or second directions under an atmosphere of 180°C may be 7.0 MPa or higher, and may be 7.5 MPa or higher, 8.0 MPa or higher, 8.5 MPa or higher, 9.0 MPa or higher, and even 9.5 MPa or higher. Appropriate control of the tensile strength can contribute to more reliable suppression of the occurrence of the above-mentioned cracks. However, it is often difficult to achieve both high tensile strength and high tensile elongation at break. The upper limit of the tensile strength is, for example, 20.0 MPa or lower, and may be 17.0 MPa or lower, 16.0 MPa or lower, 15.0 MPa or lower, 14.0 MPa or lower, 13.0 MPa or lower, and even 12.0 MPa or lower.

[0018] The tensile elongation at break and tensile strength can be evaluated by a tensile test on the fluororesin film 1.

[0019] The fluororesin film 1 in Figure 1 has a modified surface (hereinafter referred to as the modified surface) 11. By using the fluororesin film 1 so that the modified surface 11 is in contact with the rubber-containing substrate, the adhesion of the fluororesin film 1 to the rubber-containing substrate can be improved.

[0020] The adhesion of the modified surface 11 is expressed as the peel adhesion strength, which is evaluated by a 180° peel test in which the adhesive tape (Nitto Denko No. 31B, 80 μm thick) is peeled off the fluororesin film 1 after the adhesive surface of the adhesive tape is attached to the modified surface 11 so that the adhesive surface of the adhesive tape is in contact with the modified surface 11. The peel adhesion strength may be 4.0 N / 19 mm or more, 4.5 N / 19 mm or more, 5.0 N / 19 mm or more, 5.5 N / 19 mm or more, 6.0 N / 19 mm or more, 6.5 N / 19 mm or more, 7.0 N / 19 mm or more, and even 7.5 N / 19 mm or more. The upper limit of the adhesion of the modified surface 11 is expressed as the above peel adhesion strength, for example, 15.0 N / 19 mm or less. Note that No. 31B has sufficient adhesion strength to evaluate the above peel adhesion strength.

[0021] The fluororesin film 1 in Figure 1 has a modified surface 11 on one of its main surfaces. The fluororesin film 1 may have modified surfaces 11 on both of its main surfaces. If the fluororesin film 1 has two or more modified surfaces 11, the adhesion of the modified surfaces 11 may be the same or different between each modified surface 11.

[0022] The fluororesin film 1 in Figure 1 has a modified surface 11 over the entire surface of one of its main surfaces. The fluororesin film 1 may have the modified surface 11 over only a portion of its main surface. Alternatively, the fluororesin film 1 may have two or more modified surfaces 11 on a single main surface.

[0023] The thickness of the fluororesin film 1 is, for example, 10 to 300 μm, and may also be 30 to 250 μm, or even 50 to 200 μm.

[0024] The fluororesin film 1 in Figure 1 is a single layer. The fluororesin film 1 may be a laminate of two or more layers, as long as it has the above-mentioned tensile elongation at break.

[0025] Examples of fluororesins include at least one selected from ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polychlorotrifluoroethylene (PCTFE), and polytetrafluoroethylene (PTFE). The fluororesin may be at least one selected from ETFE, FEP, and PFA, or it may be ETFE.

[0026] The melt flow rate (MFR) of fluororesins (excluding PTFE, which has a very high melt viscosity and makes evaluation of the melt flow rate difficult) is, for example, 30 g / 10 min or less, and may also be 28 g / 10 min or less, 25 g / 10 min or less, or even 22 g / 10 min or less. The lower limit of the MFR is, for example, 0.5 g / 10 min or more, and may also be 1 g / 10 min or more, 1.5 g / 10 min or more, 2 g / 10 min or more, 2.5 g / 10 min or more, 3 g / 10 min or more, 3.5 g / 10 min or more, 4 g / 10 min or more, 4.5 g / 10 min or more, 5 g / 10 min or more, or even 7 g / 10 min or more. Appropriate control of the MFR can contribute to more reliable suppression of the occurrence of the above-mentioned cracks. The melt temperature and load when evaluating the MFR can be determined according to the type of fluororesin, as shown in Table 1 below. The high and low melting temperatures correspond to the typical temperatures (thermoforming temperatures) at which each resin is thermoformed.

[0027] [Table 1]

[0028] The melting point of fluororesins, as evaluated by differential scanning calorimetry (hereinafter referred to as DSC), is, for example, 250°C or lower, but may also be 245°C or lower, 240°C or lower, 235°C or lower, or even 230°C or lower. The lower limit of the melting point is, for example, 200°C or higher, but may also be 205°C or higher. Appropriate control of the melting point can contribute to more reliable suppression of the occurrence of the cracks mentioned above. In this specification, the melting point of fluororesins is defined as the temperature of the maximum endothermic peak (melting peak temperature) caused by the melting of the fluororesin, measured when the fluororesin is heated at a constant heating rate (10°C / min) using DSC. However, in order to cancel out the thermal history during film molding and clarify the resin's inherent properties, the melting point is evaluated by the second run of DSC. The melting point of fluororesins varies depending on, for example, molecular weight, molecular weight distribution, polymerization method, polymerization history, etc.

[0029] The fluororesin film 1 may contain fluororesin as its main component. In this specification, "main component" means the component with the highest content. The fluororesin content in the fluororesin film 1 may be, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or even 99% by weight or more. The fluororesin film 1 may be composed of fluororesin. The fluororesin film 1 may contain two or more types of fluororesin.

[0030] The fluororesin film 1 may contain materials other than fluororesin. Examples of other materials in the fluororesin film 1 are resins other than fluororesin. Examples of such resins are polyolefins such as polyethylene and polypropylene, and polyvinylidene chloride. The content of other materials in the fluororesin film 1 may be, for example, 20% by weight or less, and may be 10% by weight or less, 5% by weight or less, 3% by weight or less, or even 1% by weight or less.

[0031] The shape of the fluororesin film 1 may be, for example, a polygon including squares and rectangles, a circle, an ellipse, or a strip. The corners of the polygon may be rounded. However, the shape of the fluororesin film 1 is not limited to the above examples. Polygonal, circular, and elliptical fluororesin films 1 can be distributed as individual sheets, while strip-shaped fluororesin films 1 can be distributed as rolls wound around a core. The width of the strip-shaped fluororesin film 1 and the width of the roll in which the strip-shaped fluororesin film 1 is wound can be freely set.

[0032] The fluororesin film 1 is typically non-porous. The fluororesin film 1 may also be a non-porous film that does not have pores connecting both main surfaces, at least in the area of ​​use.

[0033] The fluororesin film 1 may be an impermeable film that does not allow fluids such as water, aqueous solutions, oils, and organic liquids to permeate in the thickness direction, based on the high liquid-repellent (water-repellent and oil-repellent) properties of the fluororesin. Alternatively, the fluororesin film 1 may be an insulating film (non-conductive film) based on the high insulating properties of the fluororesin. For example, the insulating properties may be 1 × 10⁻⁶. 14 It is expressed as a surface resistivity of Ω / □ or greater.

[0034] The method for producing the fluororesin film 1 is not limited. The fluororesin film 1 can be produced by various film molding methods such as melt extrusion, cutting, and casting. Mechanical properties such as tensile elongation can be adjusted by the composition of the fluororesin film 1 and by mechanical treatments such as stretching and rolling applied to the film. The fluororesin film 1 having a modified surface 11 can be produced, for example, by performing a modification treatment on a base film containing fluororesin. An example of the above method is shown below. However, the method for producing the fluororesin film 1 having a modified surface 11 is not limited to the example below.

[0035] The original film is typically a film having the same structure as the fluororesin film 1, except that it does not have a modified surface 11.

[0036] Examples of modification treatments for the original film include sputter etching, ion beam treatment, laser etching, sandblasting, and sandpaper treatment. However, the modification treatment is not limited to the above examples as long as a modified surface 11 is formed. The modification treatment may be sputter etching or ion beam treatment, or sputter etching, as these methods can efficiently form the modified surface 11.

[0037] Sputter etching can typically be performed by applying a high-frequency voltage to the original film while the chamber containing the original film is under reduced pressure and an atmospheric gas is introduced into the chamber. The high-frequency voltage can be applied, for example, using a cathode in contact with the original film and an anode spaced apart from the original film. In this case, a modified surface 11 is formed on the main surface on the anode side, which is the exposed surface of the original film. Known apparatus can be used for sputter etching.

[0038] Examples of atmospheric gases include noble gases such as helium, neon, and argon; inert gases such as nitrogen; and reactive gases such as oxygen and hydrogen. The atmospheric gas may be at least one selected from argon and oxygen, or it may be oxygen, as it can efficiently form the reforming surface 11. Only one type of atmospheric gas may be used.

[0039] The frequency of the high-frequency voltage is, for example, 1 to 100 MHz, or it may be 5 to 50 MHz. The pressure inside the chamber during processing is, for example, 0.05 to 200 Pa, or it may be 0.5 to 100 Pa.

[0040] The energy required for sputter etching (the product of power per unit area applied to the original film and the processing time) is, for example, 0.1 to 100 J / cm². 2 The radiation level is 0.1 to 50 J / cm². 2 , 0.1~40 J / cm 2 Furthermore, 0.1~30 J / cm 2 That's fine.

[0041] Sputter etching can be performed as a batch process or a continuous process. An example of a continuous process will be explained with reference to Figure 2.

[0042] An example of a continuous processing apparatus is shown in Figure 2. The processing apparatus 100 in Figure 2 comprises a chamber 101 and a roll electrode 102 and a curved plate electrode 103 arranged inside the chamber 101. The chamber 101 is connected to a pressure reducing device 104 for reducing the pressure inside the chamber 101 and a gas supply device 105 for supplying atmospheric gas to the chamber 101. The roll electrode 102 is connected to a high-frequency power supply 106, and the curved plate electrode 103 is grounded. The original film 107 is in the shape of a strip and is wound around a feed roll 108. Continuous processing can be performed by continuously feeding the original film 107 from the feed roll 108, passing it between the roll electrode 102 and the curved plate electrode 103 while following the roll electrode 102, and applying a high-frequency voltage at that time. In the example in Figure 2, a modified processing surface 11 is formed on the main surface of the original film 107 on the curved plate electrode 103 side. The processed original film 107 is wound onto a winding roll 109.

[0043] The fluororesin film 1 can be used, for example, as a coating film to cover the surface of a rubber-containing substrate in a rubber molded body. The coating film is usually used to conform to the shape of the surface of the rubber-containing substrate. In this case, depending on the shape, the coating film may be required to be strongly stretched. Furthermore, in shaping processes performed with the fluororesin film 1 placed in a mold, the degree to which the fluororesin film 1 is stretched during the shaping of the rubber is high.

[0044] Examples of rubber molded products include diaphragms, rollers, sealing materials (gaskets, O-rings, valve components, etc.), and tubular bodies (tubes, hoses, etc.). Specific examples of rubber molded products are shown below. However, rubber molded products are not limited to the examples above and the specific examples below.

[0045] The applications of fluororesin film 1 are not limited to the examples given above.

[0046] [Rubber molded product] An example of a rubber molded body according to this embodiment is shown in Figures 3A and 3B. Figure 3B shows a cross section IIIB-IIIB of the rubber molded body 21 in Figure 3A. The rubber molded body 21 in Figures 3A and 3B is a corrugated diaphragm. The rubber molded body 21 comprises a rubber-containing substrate 22 and a fluororesin film 1. The rubber-containing substrate 22 has a surface 23 covered by the fluororesin film 1. Since the surface 23 is corrugated, the fluororesin film 1 is partially (for example, at the peaks 24 of the corrugation) strongly stretched during the manufacturing of the rubber molded body 21.

[0047] All surfaces of the rubber molded body 21 may be surfaces 23, or only some surfaces may be surfaces 23.

[0048] The rubber-containing substrate 22 typically contains rubber as its main component. Examples of rubber include butyl rubber, natural rubber, ethylene propylene rubber (EPDM), silicone rubber, and fluororubber. The rubber-containing substrate 22 may also contain materials other than rubber, such as inorganic fillers, organic fillers, reinforcing fibers, antioxidants, and plasticizers.

[0049] The rubber molded articles of the present invention are not limited to the above examples, as long as they have a surface 23. Examples of rubber molded articles other than diaphragms include rollers, sealing materials (gaskets, O-rings, valve members, etc.), and tubular bodies (tubes, hoses, etc.).

[0050] Another example of the rubber molded body of this embodiment is shown in Figures 4A and 4B. Figure 4B shows a partially enlarged view of the cross section IVB-IVB and the vicinity of the protrusion 34 in the rubber molded body 31 of Figure 4A. The rubber molded body 31 in Figures 4A and 4B is a gasket. The rubber molded body 31 has a surface 23 covered with a fluororesin film 1. The rubber-containing substrate 32 of the rubber molded body 31 comprises a base portion 33 and a protrusion 34 protruding from the base portion 33. The surface 23 includes the surface of the protrusion 34. The fluororesin film 1 is strongly stretched in parts during the manufacture of the rubber molded body 31, for example, on the surface of the protrusion 34 (particularly the top portion 35 of the protrusion 34 and the connection portion 40 between the top portion 35 and the side wall portion 37), or at the connection portion 36 between the surface 38 on the base portion 33 from which the protrusion 34 protrudes and the side wall portion 37 of the protrusion 34. However, in a rubber molded body 31 equipped with a fluororesin film 1, the fluororesin film 1 is less likely to tear even in parts that are strongly stretched during manufacturing.

[0051] The protrusions 34 may have a height H of 8 mm or more, 10 mm or more, 12 mm or more, 13 mm or more, or even 14 mm or more. In these embodiments, in particular, in the embodiment in which the protrusions 34 have a height H of 10 mm or more, the degree to which the fluororesin film 1 is partially stretched during the manufacture of the rubber molded body 31 is further increased.

[0052] The fluororesin film 1 may cover the protrusion 34 from the top 35 of the protrusion 34 in the direction of the height H of the protrusion 34. The covering may reach the connecting portion 36, or it may extend beyond the connecting portion 36 to the surface 38 of the base portion 33. The fluororesin film 1 may cover all of the surface of the protrusion 34, or only a part of it. In other words, the surface 23 may include all of the surface of the protrusion 34, or only a part of it.

[0053] The width W1 of the protrusion 34 may be 50 mm or less, 20 mm or less, or even 10 mm or less. The lower limit of the width W1 is, for example, 3 mm or more. The smaller the width W1, the greater the degree to which the fluororesin film 1 is partially stretched during the manufacture of the rubber molded body 31. The width W1 is the minimum width at the cross section 30 of the protrusion 34, which is cut parallel to the surface 38 of the base portion 33, and is located at a distance of 0.1 times the height H of the protrusion 34 (0.1H) from the tip 39 of the protrusion 34.

[0054] The width W2 of the protrusion 34 may be 50 mm or less, 20 mm or less, or even 10 mm or less. The lower limit of the width W2 is, for example, 4 mm or more. The smaller the width W2, the greater the degree to which the fluororesin film 1 is partially stretched during the manufacture of the rubber molded body 31. The width W2 is determined as the minimum distance between two parallel tangents that sandwich the cross section 29, which is located at a distance of 0.8 times the height H of the protrusion 34 (0.8H) from the tip 39 of the protrusion 34, in a cross section of the protrusion 34 cut parallel to the surface 38 of the base 33.

[0055] The ratio of width W1 to width W2, W1 / W2, may be 0.5 to 2.0, 0.75 to 1.33, or even 0.85 to 1.18.

[0056] The maximum inclination angle θ formed by the side wall portion 37 of the protrusion 34 with respect to the surface 38 of the base portion 33 may be 60 degrees or more, 70 degrees or more, 80 degrees or more, or even 90 degrees or more. The upper limit of the above maximum value is, for example, 110 degrees or less. The larger the above maximum value, the greater the degree to which the fluororesin film 1 is partially stretched during the manufacturing of the rubber molded body 31.

[0057] The rubber molded body 31 may have two or more protrusions 34. The surface 23 may include the surfaces of the two or more protrusions 34. The fluororesin film 1 may cover the two or more protrusions 34 continuously or individually. The spacing between the two or more protrusions 34 (distance between the tips 39) may be 50 mm or less, 20 mm or less, or even 15 mm or less.

[0058] Another example of the rubber molded body of this embodiment is shown in Figures 5A and 5B. Figure 5B shows the cross section VB-VB of the rubber molded body 41 in Figure 5A. The rubber molded body 41 in Figures 5A and 5B is a gasket. The rubber molded body 41 has the same configuration as the rubber molded body 31 except that the shape of the protrusion 34 is different. The protrusion 34 of the rubber molded body 41 has a recess 42 at its apex 35. The fluororesin film 1 covers the protrusion 34, including the recess 42, from the apex 35 of the protrusion 34 in the direction of the height H of the protrusion 34. In this embodiment, the degree to which the fluororesin film 1 is partially stretched during the manufacture of the rubber molded body 31 is further increased. The fluororesin film 1 may cover all or part of the surface of the recess 42.

[0059] In the rubber molded articles 21, 31, and 41, the fluororesin film 1 may be free from tears.

[0060] The rubber molded bodies 21, 31, and 41 can be manufactured, for example, by shaping rubber while a fluororesin film 1 is placed inside a mold. From this perspective, the present invention is A method for manufacturing a rubber molded article comprising a resin film and a rubber-containing substrate, wherein the rubber-containing substrate has a surface covered by the resin film, This includes shaping the rubber while the resin film is placed inside the mold to obtain the rubber molded body, A method for manufacturing a rubber molded article in which the resin film is a fluororesin film 1, To provide.

[0061] Examples of shaping processes include in-mold molding and film insert molding. However, shaping processes are not limited to the above examples.

[0062] By using the fluororesin film 1 in the manufacture of the rubber molded articles 21, 31, and 41, the surface 23 may include the surface of the protrusion 34 protruding from the base 33 of the rubber-containing substrate 32, the protrusion 34 having a height of 10 mm or more, and the fluororesin film 1 may cover the protrusion 34 from the top 35 of the protrusion 34 in the direction of the height H of the protrusion 34, and a rubber molded article may be obtained without any cracks in the fluororesin film 1. From this aspect, the present invention is A method for manufacturing a rubber molded article comprising a resin film and a rubber-containing substrate, wherein the rubber-containing substrate has a surface covered by the resin film, In the aforementioned rubber molded body, The aforementioned resin film is a fluororesin film and is free from tears. The aforementioned surface includes the surface of the protrusions that extend from the base of the rubber-containing substrate. The aforementioned protrusion has a height of 10 mm or more. The resin film covers the protrusion from the top of the protrusion in the height direction of the protrusion, The aforementioned manufacturing method is This includes shaping rubber while a fluororesin film 1 is placed inside a mold to obtain the rubber molded body. Method for manufacturing a rubber molded body, To provide.

[0063] The rubber molded article according to this embodiment comprises a fluororesin film 1 and a rubber-containing substrate 32, wherein the rubber-containing substrate 32 has a surface 23 covered by the fluororesin film 1, and the surface 23 includes the surface of a protrusion 34 that protrudes from the base 33 of the rubber-containing substrate 32, the protrusion 34 having a height of 10 mm or more, and the fluororesin film 1 covers the surface of the protrusion 34 without tearing from the top 35 of the protrusion 34 in the direction of the height H of the protrusion 34. According to this embodiment, it is possible to provide a rubber molded article in which the surface of a protrusion of this height is covered with a fluororesin film without tearing by a molding method using a mold. From this aspect, the present invention is A method for manufacturing a rubber molded article comprising a resin film and a rubber-containing substrate, wherein the rubber-containing substrate has a surface covered by the resin film, In the aforementioned rubber molded body, The aforementioned resin film is a fluororesin film and is free from tears. The aforementioned surface includes the surface of the protrusions that extend from the base of the rubber-containing substrate. The aforementioned protrusion has a height of 10 mm or more. The resin film covers the protrusion from the top of the protrusion in the height direction of the protrusion, The aforementioned manufacturing method is This includes shaping rubber while a resin film is placed inside a mold to obtain the rubber molded body, As the resin film, a resin film is used that has a tensile elongation at break that does not tear when it is changed from a film state to a shape that follows the recess of the mold corresponding to the protrusion in the depth direction of the recess. Method for manufacturing a rubber molded body, To provide.

[0064] The tensile elongation at which tearing does not occur can be determined based on the shape of the mold's recess (e.g., the depth D of the recess, the opening dimensions, the ratio of depth D to the opening dimensions, etc.), the temperature and pressure applied during the shaping process, etc. As shown in the following examples, for fluororesin films, it is important to prioritize ensuring sufficient tensile elongation at break rather than trying to achieve both tensile strength and tensile elongation at break. [Examples]

[0065] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples.

[0066] First, we will describe the evaluation method for fluoropolymer films.

[0067] [thickness] The thickness was determined using a micrometer (manufactured by Mitutoyo) and was calculated as the average value of measurements taken at at least four points.

[0068] [Tensile elongation at fracture, tensile strength] The mechanical properties (tensile elongation at break and tensile strength) based on tensile testing were evaluated as follows. A fluororesin film was punched out into a dumbbell-shaped No. 3 form as defined in JIS K6251:2017 to prepare a test specimen. Next, to suppress elongation in parts of the test specimen other than the parallel section (the section between the gauge marks) during testing, a 35 mm range from both ends in the longitudinal direction of the test specimen was reinforced with reinforcing tape (Nitto Denko, No. 360UL). Reinforcement was carried out by attaching the reinforcing tape to one side of the test specimen. Next, a tensile test was performed on the test specimen using a tensile testing machine (Orientec, Tensilon universal tester). The test temperature was set to 180°C (starting after 5 minutes of preheating of the test specimen), and the tensile speed was set to 200 mm / min. The tensile test was performed in both the MD direction (winding direction during film formation; longitudinal direction) and the TD direction (width direction) of the fluororesin film. The length of the specimen at the fracture point was defined as L1, and the ratio L1 / L0 to the length of the specimen before testing (L0) was calculated and defined as the tensile elongation at fracture (unit: %). In addition, for tensile tests in the MD direction, the tensile strength (unit: MPa) was determined by dividing the maximum stress (tensile force) recorded before the specimen fracture by the cross-sectional area of ​​the parallel portion of the specimen before testing.

[0069] [Peel-off adhesive strength] The peel-off adhesive strength was evaluated as follows. First, the fluororesin film was cut into strips 19 mm wide and 150 mm long to make test pieces. Next, the test pieces were attached to the surface of a stainless steel plate using double-sided adhesive tape (Nitto Denko, No. 500). The attachment was carried out so that the entire test piece was in contact with the stainless steel plate and the modified surface of the fluororesin film was exposed. The double-sided adhesive tape was selected to have sufficient adhesive strength so that the test piece would not peel off the stainless steel plate during evaluation. Next, a single-sided adhesive tape (Nitto Denko, No. 31B, 80 μm thick, acrylic adhesive) 19 mm wide and 200 mm long was attached to the exposed surface of the test piece. The bonding was performed such that the long sides of the test specimen and the single-sided adhesive tape coincided, and one end of the single-sided adhesive tape in the direction of its long side remained a free end for a length of 120 mm without contacting the test specimen, while the entire adhesive layer of the single-sided adhesive tape, excluding the free end, was in contact with the test specimen. Furthermore, to ensure a more secure bond between the single-sided adhesive tape and the test specimen, a 2 kg pressure roller as specified in JIS Z0237:2009 was passed back and forth once at a temperature of 25°C. Next, to stabilize the bond between the single-sided adhesive tape and the test specimen, the test sample was left to stand for 30 minutes after the pressure roller's return and then set in a tensile testing machine. The setting was performed such that the direction of the long side of the test specimen coincided with the direction between the chucks of the testing machine, and one chuck of the testing machine gripped the free end of the single-sided adhesive tape while the other chuck gripped the test specimen and the stainless steel plate. Next, a 180° peel test was performed in which the single-sided adhesive tape was peeled off the test specimen at a peel angle of 180° and a test speed of 300 mm / min. After the start of the test, the measurement of the first 20 mm peeled off was ignored, and the average of the measurements of the subsequent 60 mm peeled off was taken as the peel adhesive strength of the test specimen. The test was conducted in an environment with a temperature of 25±1℃ and a relative humidity of 50±5%.

[0070] [MFR] The MFR of ETFE contained in the fluororesin films of Examples and Comparative Examples 1 and 2 was measured in accordance with ASTM D3159-20 (melting temperature 297°C, load 5kg), which is the industrial standard for ETFE. The MFR of PFA contained in the fluororesin film of Comparative Example 3 was calculated by measuring the weight (g) of PFA flowing out per unit time (10 minutes) from a nozzle with a diameter of 2 mm and a length of 8 mm under measurement conditions of a melting temperature of 372°C and a load of 2 kg. The MFR of FEP contained in the fluororesin film of Comparative Example 4 was determined in accordance with ASTM D2216 (melting temperature 372°C, load 5kg), which is the industrial standard for FEP.

[0071] [Melting point] The melting point of the fluororesin contained in the fluororesin film was evaluated by DSC as follows: 10±5 mg of fluororesin film was placed in the lower tray of an aluminum pan, covered with the upper tray, and pressed vertically to seal under pressure. Next, it was held at 0°C for 1 minute, then heated to 260°C at a heating rate of 10°C / min, held at 260°C for 1 minute, and then cooled down to 0°C at a cooling rate of 10°C / min (first run). Next, it was held at 0°C for 1 minute, and then heated again to 260°C at a heating rate of 10°C / min (second run), and the melting peak temperature at this time was taken as the melting point of the fluororesin. The DSC instrument and analysis software used were a NETZCH Japan DSC200F3 and Proteus software.

[0072] [Excipient testing] A rubber molding process simulating in-mold molding was performed using a fluororesin film, and the fluororesin film covering the surface of the resulting rubber molded body was visually inspected for any cracks. The molding process was carried out according to the following procedure.

[0073] A fluororesin film and an unvulcanized butyl rubber sheet (durometer hardness 28, evaluated by a Type A durometer) were layered and placed on the molding surface of a mold having two or more recesses representing the convex portion 34 of the gasket. Each recess had the same shape, and each had a rectangular opening and a cross-sectional shape (cross-sectional area 10 mm²). 2The fluororesin film had a depth of 15 mm. The fluororesin film was placed so that the modified surface of the fluororesin film was in contact with the butyl rubber sheet, and the fluororesin film was on the mold side. Next, a high-temperature, high-pressure press (Mikado Technos, high-temperature heating and pressing device MKP-1500D-WH-ST) was used to shape the product at a temperature of 170°C and a pressing force of 20 kN × 5 seconds (pressure molding) followed by 4.5 kN × 10 minutes (vulcanization) to obtain a rubber molded body having two or more protrusions (height H=15 mm) protruding from the base and corresponding to the recesses of the mold, and the entire surface of the protrusions being covered with fluororesin film. The protrusions of the obtained rubber molded body were visually inspected, and if no cracks were observed in the fluororesin film, it was considered good; if cracks were observed, it was considered unacceptable.

[0074] (Example 1) A 50 μm thick ETFE film was produced by melt extrusion molding of ETFE resin (AGC, LM-720AP). Next, one side of the ETFE film was subjected to surface modification treatment by sputter etching to obtain the fluororesin film of Example 1. The sputter etching conditions were the same for all fluororesin films in the examples and comparative examples.

[0075] (Example 2) A fluororesin film of Example 2 was obtained in the same manner as in Example 1, except that an ETFE film with a thickness of 100 μm was fabricated.

[0076] (Example 3) The fluororesin film of Example 3 was obtained in the same manner as in Example 2, except that the lot of the ETFE resin (manufactured by AGC, LM-720AP) was changed.

[0077] (Example 4) A fluororesin film of Example 4 was obtained in the same manner as in Example 1, except that an ETFE film with a thickness of 200 μm was fabricated.

[0078] (Example 5) A fluororesin film of Example 5 was obtained in the same manner as in Example 1, except that AGC's LM-730AP was used as the ETFE resin.

[0079] (Example 6) The fluororesin film of Example 6 was obtained in the same manner as in Example 5, except that the lot of the ETFE resin (manufactured by AGC, LM-730AP) ​​was changed and an ETFE film with a thickness of 100 μm was fabricated.

[0080] (Comparative Example 1) A fluororesin film of Comparative Example 1 was obtained in the same manner as in Example 1, except that EP-546 manufactured by Daikin Industries was used as the ETFE resin.

[0081] (Comparative Example 2) A fluororesin film of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that an ETFE film with a thickness of 100 μm was fabricated.

[0082] (Comparative Example 3) A PFA film with a thickness of 45 μm was fabricated by melt extrusion molding of PFA resin (DuPont, 920 HP Plus). Next, one side of the PFA film was subjected to surface modification treatment by sputter etching to obtain the fluororesin film of Comparative Example 3.

[0083] (Comparative Example 4) A fluororesin film of Comparative Example 4 was obtained by performing a surface modification treatment by sputter etching on one side of a 50 μm thick FEP film (manufactured by Daikin Industries, NF-0050).

[0084] The evaluation results for each fluororesin and fluororesin film are shown in Tables 2 and 3 below. Furthermore, magnified images of the convex portions in the rubber molded articles obtained from the shaping tests for Example 1 and Comparative Example 1 are shown in Figures 6 and 7, respectively.

[0085] [Table 2]

[0086] [Table 3]

[0087] As shown in Table 3, the fluororesin film of the example did not tear during the shaping test (see Figure 6 for Example 1). On the other hand, the fluororesin film of the comparative example did tear during the shaping test (see Figure 7 for Comparative Example 1). As shown in Figure 7, multiple tears 71 occurred on the convex portion. [Industrial applicability]

[0088] The fluororesin film of the present invention can be used, for example, as a coating film to cover the surface of a rubber-containing substrate in a rubber molded article.

Claims

1. Contains fluororesin, A fluoropolymer film in which the average value of the tensile elongation at break in a first in-plane direction and the tensile elongation at break in a second direction perpendicular to the first direction in the in-plane, under an atmosphere of 180°C, is 1200% or more.

2. The fluororesin film according to claim 1, wherein the tensile strength in the first and / or second direction in an atmosphere of 180°C is 7.0 MPa or more.

3. The fluororesin film according to claim 1 or 2, wherein the tensile strength in the first direction and / or the second direction in an atmosphere of 180°C is 20.0 MPa or less.

4. A fluororesin film according to any one of claims 1 to 3, wherein the melting point of the fluororesin, as evaluated by differential scanning calorimetry (DSC), is 250°C or lower.

5. A fluororesin film according to any one of claims 1 to 4, having a modified surface.

6. The adhesion of the aforementioned surface is The fluororesin film and the adhesive tape (Nitto Denko No. 31B, 80 μm thick) are bonded together so that the adhesive surface of the adhesive tape is in contact with the surface of the fluororesin film. The adhesive strength of the peel-off test, which is evaluated by peeling the adhesive tape from the fluororesin film at 180°, is indicated by the result. A fluororesin film according to claim 5, wherein the N / 19 mm or greater.

7. The fluororesin film according to any one of claims 1 to 6, wherein the fluororesin is an ethylene-tetrafluoroethylene copolymer.

8. A fluororesin film according to any one of claims 1 to 7, having a thickness of 10 to 300 μm.

9. A fluororesin film according to any one of claims 1 to 8, which is a coating film for covering the surface of a rubber-containing substrate provided on a rubber molded body.

10. It comprises a rubber-containing substrate and a resin film, The rubber-containing substrate has a surface covered by the resin film, The resin film is a fluororesin film according to any one of claims 1 to 9, in a rubber molded body.

11. The aforementioned surface includes the surface of the protrusions that extend from the base of the rubber-containing substrate. The rubber molded body according to claim 10, wherein the protrusion has a height of 10 mm or more.

12. The rubber molded body according to claim 11, wherein the resin film covers the protrusion from the top of the protrusion to the height direction of the protrusion.

13. A method for manufacturing a rubber molded article comprising a resin film and a rubber-containing substrate, wherein the rubber-containing substrate has a surface covered by the resin film, This includes shaping the rubber while the resin film is placed inside the mold to obtain the rubber molded body, The resin film is a fluororesin film according to any one of claims 1 to 9. A method for manufacturing a rubber molded product.

14. A method for manufacturing a rubber molded article comprising a resin film and a rubber-containing substrate, wherein the rubber-containing substrate has a surface covered by the resin film, In the aforementioned rubber molded body, The aforementioned resin film is a fluororesin film and is free from tears. The aforementioned surface includes the surface of the protrusions that extend from the base of the rubber-containing substrate. The aforementioned protrusion has a height of 10 mm or more. The resin film covers the protrusion from the top of the protrusion in the height direction of the protrusion, The aforementioned manufacturing method is The method includes shaping rubber while a fluororesin film according to any one of claims 1 to 9 is placed in a mold to obtain the rubber molded product, A method for manufacturing a rubber molded product.

15. A method for manufacturing a rubber molded article comprising a resin film and a rubber-containing substrate, wherein the rubber-containing substrate has a surface covered by the resin film, In the aforementioned rubber molded body, The aforementioned resin film is a fluororesin film and is free from tears. The aforementioned surface includes the surface of the protrusions that extend from the base of the rubber-containing substrate. The aforementioned protrusion has a height of 10 mm or more. The resin film covers the protrusion from the top of the protrusion in the height direction of the protrusion, The aforementioned manufacturing method is This includes shaping rubber while a resin film is placed inside a mold to obtain the rubber molded body, As the resin film, a resin film is used that has a tensile elongation at break that does not tear when it is changed from a film state to a shape that follows the recess of the mold corresponding to the protrusion in the depth direction of the recess. A method for manufacturing a rubber molded product.

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