Repair method for building rubber product and building rubber product

Abstract

To provide a repair method for building rubber products capable of suppressing crack progress and extending the service life of building rubber products, and to provide building rubber products with high repair effectiveness and excellent durability.SOLUTION: A repair method for building rubber products comprises: a cutting step of cutting an area including a crack 17 generated on a surface of a building rubber product 1 to form a recess 20; a filling step of filling the recess 20 with a filling material 21; and a coating step of applying a coating material to cover an opening of the recess 20 to form a protective film 22. A vertical length of the opening of the recess 20 is equal to or greater than a depth of the recess 20. The building rubber product 1 has a repair portion 2. The repair portion 2 comprises: the recess 20 formed by cutting the surface of the building rubber product 1 prior to repair; the filler material 21 filled into the recess 20; and the protective film 22 covering the opening of the recess 20. The vertical length of the opening of the recess 20 is equal to or greater than the depth of the recess 20.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a repair method for rubber products placed on structures such as buildings, bridges, and elevated roads. [Background technology]

[0002] Rubber products are used in structures such as buildings, bridges, and elevated highways for purposes such as seismic isolation. Examples of such rubber products include rubber bearings, which are placed between the superstructure and substructure. Rubber bearings support the superstructure and have the function of dispersing and attenuating horizontal forces by responding to shear deformation. One example of a rubber bearing is a laminate in which rubber layers and rigid hard plates, such as metal plates, are alternately stacked and integrated. A covering rubber layer may be placed around the laminate to prevent the rubber layer from being exposed to the outside. When exposed to the outside, rubber layers (hereinafter, including covering rubber layers unless otherwise specified) deteriorate over time due to exposure to water, oxygen, ozone, light, and other factors. In particular, cracking due to ozone and other factors is a major problem because it affects the product life of the rubber bearing.

[0003] When a crack occurs in the rubber layer, replacing the entire rubber bearing is not practical in terms of construction time and cost. Therefore, a means of repairing the crack and extending the life of the rubber bearing is desired. For example, Patent Document 1 describes a repair method in which the deteriorated portion of the rubber bearing is cut away, a weather-resistant rubber protective material is applied to that portion, and the rubber protective material is heated and vulcanized using an electromagnetic induction heating device. Patent Document 2 describes a repair method in which a repair material is applied to the surface of a deteriorated rubber bearing and dried to form a protective coating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-101616 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-244606 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional repair methods are insufficient in their repair effectiveness, and even after repair, it is difficult to stop the progression of cracks caused by ozone and other factors. Two possible causes are considered: First, insufficient adhesion between the rubber bearing and the repair material. Second, insufficient resistance of the repair material to degradation factors such as temperature changes, water, oxygen, ozone, and light. Regarding the first cause, the rubber bearing is repeatedly subjected to shear deformation in addition to compressive forces from the superstructure. Therefore, the repair material must also be able to adapt to shear deformation and be durable. For example, simply applying a repair material to the surface of a deteriorated rubber bearing, as in the repair method described in Patent Document 2, may result in the repair material peeling off as the shear deformation repeats. Furthermore, the inventor's research has revealed that even if the repair material is filled into the crack during repair, the crack repeatedly opens and closes due to shear deformation, which may result in the repair material being pushed out and peeling off. In this regard, the repair method described in Patent Document 1 involves cutting the deteriorated portion of the rubber bearing and then applying a rubber-based protective material, but Patent Document 1 does not consider the behavior of the cut portion during shear deformation, nor does it provide any knowledge about the size, shape, etc. of the cut portion. Furthermore, this repair method requires that the rubber-based protective material be heated using an electromagnetic induction heating device, making the construction work complicated.

[0006] The present disclosure has been made in view of the above circumstances, and aims to provide a repair method for rubber products for construction that can inhibit the progression of cracks and extend the product life of the rubber products for construction, and also to provide rubber products for construction that have high repair effectiveness and excellent durability. [Means for solving the problem]

[0007] (1) In order to solve the above-mentioned problems, the disclosed repair method for rubber products for construction includes a cutting step of cutting an area containing a crack that has occurred on the surface of the rubber product for construction to form a recess, a filling step of filling the recess with a filler, and a coating step of applying a coating material to cover the opening of the recess to form a protective film, wherein the vertical length of the opening of the recess is equal to or greater than the depth of the recess.

[0008] In the repair method for rubber products for construction disclosed herein (hereinafter sometimes simply referred to as the "repair method of the present disclosure"), a recess is first formed by cutting the area containing the crack, a filler is then filled into the formed recess, and a coating material is then applied to cover the opening of the recess filled with the filler to form a protective film. By removing the deteriorated portion, such as a crack, and using at least two types of repair materials, a filler and a coating material, the repair effect can be improved and its durability can be increased. For example, selecting a filler material that has excellent adhesion to the rubber layer or that is flexible and has excellent adaptability to deformation improves the adhesion and adaptability of the filler to the rubber layer, making it less likely to peel off even when subjected to repeated shear deformation. Furthermore, selecting a coating material that is highly resistant to degradation factors, such as excellent ozone resistance, increases the durability of the protective film and suppresses the occurrence of cracks. As a result, the life of rubber products for construction can be extended.

[0009] Furthermore, the repair method of the present disclosure specifies the size of the recess formed by cutting the area containing the crack. As a result of studies using FEM analysis and other methods described below, the inventors discovered that when removing a crack by cutting, if the vertical length of the opening of the recess formed (hereinafter sometimes referred to as the "recess width") is equal to or greater than the cutting depth (recess depth), distortion in the recess during shear deformation is reduced, allowing the recess to open less when a tensile force is applied and to close less when a compressive force is applied. The repair method of the present disclosure, based on this finding, can prevent the filler from being extruded from the recess even when shear deformation is repeated, thereby maintaining the repair effect of the filler for a long period of time.

[0010] (2) In the cutting step of the above configuration, the recess may be formed so that the vertical length of the internal space decreases from the opening toward the depth direction. With this configuration, it is easy to fill the entire recess with the filler.

[0011] (3) In any of the above configurations, the recess may be configured to have a curved surface. With this configuration, the filler can easily spread throughout the recess, and stress during deformation of the rubber product for construction is less likely to concentrate in the recess, thereby further suppressing peeling of the filler.

[0012] (4) In any of the above configurations, the crack depth may be less than 10 mm. For example, if the rubber product for construction is a rubber bearing with a coating rubber layer, it is desirable to repair the crack so that it does not become too deep and remains within the coating rubber layer. The repair method disclosed herein can be applied to cracks of various depths, but is particularly effective when repairing relatively deep cracks of 1 mm or more but less than 10 mm that occur in a coating rubber layer, etc.

[0013] (5) In any of the above configurations, the filler may be one or more selected from room-temperature curing polyurethane resins and room-temperature curing polyurea resins. Polyurethane resins and polyurea resins are relatively flexible, and therefore have excellent adhesion to the rubber layer and excellent adaptability to deformation of the rubber layer. They also have excellent weather resistance, such as ozone resistance. Furthermore, because they are room-temperature curing resins, they do not require heating equipment, and are easy to work with on-site.

[0014] (6) In any of the above configurations, the coating material may contain a polyurethane resin. This resin is relatively flexible, so it has excellent adhesion to the rubber layer and is able to follow the deformation of the rubber layer. It also has excellent ozone resistance, heat resistance, and cold resistance. Furthermore, a paint containing a polyurethane resin can be applied relatively thickly, so it can form a thick protective film and improve barrier properties and durability.

[0015] (7) In any of the above configurations, the coating material may comprise a first coating material and a second coating material of different types, and the protective film may be configured to have a first layer formed from the first coating material and a second layer formed from the second coating material, laminated in the thickness direction. With this configuration, the protective film can be formed from two layers with different properties, and the two layers can be functionally separated to easily achieve adhesion to the rubber layer, ability to follow deformation of the rubber layer, resistance to degradation factors, etc.

[0016] (8) In the configuration of (7) above, the first layer may be disposed on the recessed portion side, the first coating material may comprise a polyurethane resin, and the second layer may be disposed on the outer side of the first layer, the second coating material may comprise a silicone resin. With this configuration, the first layer mainly provides adhesion to the rubber layer, ability to follow deformation of the rubber layer, and ozone resistance, while the second layer mainly provides ultraviolet resistance, heat resistance, and water resistance.

[0017] (9) In any of the above configurations, the protective film may be formed on the entire surface where the recess is formed. With this configuration, the protective film is also disposed on the surface other than the recess that is the repaired portion, thereby improving the resistance of the entire surface to deterioration factors and suppressing the occurrence of future cracks, etc.

[0018] (10) In any of the above configurations, the rubber product for construction may be a rubber bearing. With this configuration, it is possible to extend the life of the rubber bearing, which is not easily replaced.

[0019] (11) The rubber product for construction disclosed herein is a rubber product for construction having a repaired portion, the repaired portion having a recess formed by cutting the surface of the rubber product for construction before repair, a filler material filled in the recess, and a protective film covering the opening of the recess, wherein the vertical length of the opening of the recess is equal to or greater than the depth of the recess.

[0020] The rubber product for construction disclosed herein is a rubber product for construction in which deteriorated portions such as cracks have been removed and repaired with a filler and a protective film. In the rubber product for construction disclosed herein, the width of the recess formed by cutting out the deteriorated portions such as cracks is equal to or greater than the depth of the recess, so that the degree of opening and closing of the recess is small even when tensile or compressive forces are applied due to shear deformation or the like. Therefore, even when shear deformation is repeated, the filler is less likely to be extruded from the recess, and the repair effect of the filler is maintained for a long period of time. Furthermore, because the rubber product for construction disclosed herein has both a filler and a protective film, it has a high repair effect and excellent durability. [Effects of the Invention]

[0021] In the repair method for rubber products for construction disclosed herein, deteriorated portions such as cracks are cut and removed to a predetermined size, and then repaired using at least two types of materials: a filler and a coating material. This prevents the cracks from progressing and extends the product life of the rubber product for construction. Rubber products for construction having the repaired portions disclosed herein have high repair effectiveness and excellent durability. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a perspective view of a rubber bearing for bridges according to an embodiment of the present disclosure. FIG. [Figure 2] FIG. 2 is a cross-sectional view taken along the line II-II in FIG. [Figure 3] FIG. 3 is an enlarged view of the area within the frame III in FIG. 2. [Figure 4] FIG. 1 is a partial cross-sectional view of a rubber bearing in which a crack has occurred on the surface. [Figure 5] FIG. 10 is a partial cross-sectional view of the rubber bearing during a cutting process. [Figure 6] FIG. 10 is a partial cross-sectional view of a rubber bearing in a modification treatment process. [Figure 7] FIG. 10 is a partial cross-sectional view of the rubber bearing during the filling process. [Figure 8] FIG. 10 is a partial cross-sectional view of the rubber bearing during a primer application process. [Figure 9] FIG. 4 is a partial cross-sectional view of the rubber bearing in a first coating step. [Figure 10A] FIG. 4 is a cross-sectional view showing an example of a recess formed in a cutting step. [Figure 10B] FIG. 4 is a cross-sectional view showing an example of a recess formed in a cutting step. [Figure 10C] FIG. 4 is a cross-sectional view showing an example of a recess formed in a cutting step. DETAILED DESCRIPTION OF THE INVENTION

[0023] First, one embodiment of the disclosed method for repairing rubber products for construction and a rubber product for construction having a repaired portion is shown. FIG. 1 shows a perspective view of a rubber bearing for bridges with a repaired crack (hereinafter, in this embodiment, simply referred to as a "rubber bearing"). FIG. 2 shows a cross-sectional view along the II-II direction in FIG. 1. FIG. 3 shows an enlarged view of the area within box III in FIG. 2. In FIG. 1, for ease of explanation, the crack before repair is shown with a dotted line, and the repaired portion is shown surrounded by a thin line. Regarding the orientations in FIGS. 1 and 2, of the two horizontal directions, the bridge axis direction is defined as the front-to-back direction, the direction perpendicular to that is defined as the left-to-right direction, and the vertical direction is defined as the up-down direction (the lamination direction in the rubber bearing). The rubber bearing of this embodiment is included in the concept of a "rubber product for construction" in this disclosure.

[0024] [composition] First, the configuration of the rubber bearing of this embodiment will be described. As shown in Figures 1 and 2, the rubber bearing 1 has a rectangular parallelepiped shape and includes a laminate 10, a coating rubber layer 11, and a repair portion 2.

[0025] The laminate 10 includes a rubber layer 12, multiple intermediate hard plates 13, an upper hard plate 14, and a lower hard plate 15. The rubber layer 12 is made of a rubber composition containing natural rubber. The multiple intermediate hard plates 13 are all made of metal and are arranged inside the rubber layer 12 at predetermined intervals in the vertical direction. This results in the laminate 10 having a structure in which the rubber layers 12 and the intermediate hard plates 13 are alternately stacked. The upper hard plate 14 is made of a different metal from the intermediate hard plates 13 and is arranged at the top of the laminate 10. The upper hard plate 14 is fixed to the underside of an upper mounting plate 80 using bolts (not shown). The upper mounting plate 80 is attached to a superstructure such as a bridge girder. The lower hard plate 15 is made of the same metal as the upper hard plate 14 and is arranged at the bottom of the laminate 10. The lower hard plate 15 is fixed to the top surface of a lower mounting plate 81 using bolts (not shown). The lower mounting plate 81 is attached to a substructure such as a bridge pier.

[0026] The covering rubber layer 11 is disposed so as to surround the side surface of the laminate 10. The covering rubber layer 11 is made of a rubber composition containing the same natural rubber as the rubber layer 12. The covering rubber layer 11 is continuous with the rubber layer 12 and is made integral with the rubber layer 12 and each of the hard plates 13, 14, and 15.

[0027] The repaired portion 2 is disposed on the front surface 16 of the rubber bearing 1. The repaired portion 2 is a portion where a crack 17 that occurred on the front surface of the coating rubber layer 11 has been repaired, and has a rectangular shape extending in the left-right direction. The repaired portion 2 has a recess 20, a filler 21, and a protective film 22.

[0028] As shown enlarged in FIG. 3, the recess 20 is formed by cutting the front surface of the coating rubber layer 11. The opening of the recess 20 has a rectangular shape that extends linearly in the left-right direction. The vertical cross section of the recess 20 has a C-shaped curved surface. The vertical length of the internal space of the recess 20 decreases from the opening toward the depth (rearward). The vertical length of the opening of the recess 20 (the width w of the recess 20) is greater than the depth d. A modified layer 23 is disposed on the surface of the recess 20. The modified layer 23 is formed by applying a chlorine-based surface modifier to the surface of the recess 20.

[0029] The filler 21 contains a room temperature curing polyurethane resin and fills the entire recess 20. The surface of the filler 21 and the opening of the recess 20 are flush with each other. A primer layer 24 is disposed on the opening of the recess 20 so as to cover the filler 21. The primer layer 24 is disposed over the entire front surface of the coating rubber layer 11. The primer layer 24 contains a chlorinated olefin resin.

[0030] The protective film 22 is disposed so as to cover the opening of the recess 20 via the primer layer 24. The protective film 22 is disposed over the entire front surface of the coating rubber layer 11. The protective film 22 has a first layer 220 and a second layer 221. The first layer 220 is disposed on the front surface of the coating rubber layer 11, and is formed from a room-temperature curing polyurethane resin-based water-based paint. The second layer 221 is laminated on the first layer 220, and is formed from a room-temperature curing silicone resin-based water-based paint. The second layer 221 is exposed on the front surface 16 of the rubber bearing 1.

[0031] [Rubber bearing repair method] Next, a rubber bearing repair method according to this embodiment will be described. The rubber bearing repair method according to this embodiment includes a cutting process, a modification process, a filling process, a primer application process, a first coating process, and a second coating process. Each process will be described in order below.

[0032] (1) Cutting process In this step, a region containing a crack that has occurred on the front surface of the coating rubber layer is cut to form a recess. FIG. 4 shows a partial cross-sectional view of a rubber bearing in which a crack has occurred on the surface. FIG. 5 shows a partial cross-sectional view of the rubber bearing in the cutting step. FIGS. 4 and 5 are partial cross-sectional views of the rubber bearing in the front-rear direction, and correspond to the previously mentioned FIG. 3 (an enlarged view of box III in FIG. 2) (the same applies to FIGS. 6 to 9 described later). As shown in FIG. 4, a crack 17 has occurred on the front surface of the coating rubber layer 11. In this step, as shown in FIG. 5, the region containing the crack 17 is cut to form a recess 20 with a C-shaped cross section. In this step, the depth d of the recess 20 is set to be equal to or greater than the depth of the crack 17, so that the crack 17 is removed, and the width w of the recess 20 is set to be greater than the depth d.

[0033] (2) Modification process In this step, the surface of the recessed portion is modified. Figure 6 shows a partial cross-sectional view of the rubber bearing during the modification step. As shown in Figure 6, a chlorine-based surface modifier is applied to the surface of the recessed portion 20 to form a modified layer 23.

[0034] (3) Filling process In this step, the recess is filled with a filler. Figure 7 shows a partial cross-sectional view of the rubber bearing during the filling step. As shown in Figure 7, the entire recess 20 on which the modified layer 23 is formed is filled with a filler 21 containing a room-temperature curing polyurethane resin.

[0035] (4) Primer application process In this step, a primer is applied onto the filler to form a primer layer. Figure 8 shows a partial cross-sectional view of the rubber bearing during the primer application step. As shown in Figure 8, a primer containing a chlorinated olefin resin is applied to the entire front surface of the coating rubber layer 11 so as to cover the opening of the recess 20 filled with the filler 21, thereby forming a primer layer 24.

[0036] (5) First coating process In this step, a first coating material is applied to form a first layer, covering the opening of the recess with the primer layer interposed therebetween. FIG. 9 shows a partial cross-sectional view of the rubber bearing in the first coating step. As shown in FIG. 9, a room-temperature curing polyurethane resin-based water-based paint is applied as the first coating material to the entire surface of the primer layer 24 to form a first layer 220, which is one of the protective films 22. The filler 21 in the recess 20 is covered by the first layer 220 with the primer layer 24 interposed therebetween.

[0037] (6) Second coating process In this step, a second coating material is applied to the outside of the first layer to form the second layer. Specifically, a room temperature curing silicone resin-based water-based paint is applied as the second coating material to the entire surface of the first layer 220 to form the second layer 221, which is one of the protective films 22 (see FIG. 3 above).

[0038] [Action and effect] Next, the effects of the rubber bearing and the rubber bearing repair method of this embodiment will be described. In the repair method of this embodiment, cracks 17 are removed, and a filler 21, a first coating material, and a second coating material are used as repair materials, resulting in a high repair effect and excellent durability. Of these, a room-temperature curing polyurethane resin is used for the filler 21. This improves adhesion to the coating rubber layer 11 and its ability to follow deformation, making the filler 21 less likely to peel. Furthermore, the use of a room-temperature curing resin eliminates the need for heating equipment, improving on-site workability. Furthermore, a modified layer 23 is formed in the recess 20. Functional groups such as hydroxyl groups (-OH) and chloro groups (-Cl) in the modified layer 23 react with the isocyanate in the filler 21, improving adhesion.

[0039] The first coating material forming the first layer 220 is a room-temperature curing polyurethane resin-based water-based paint, and the second coating material forming the second layer 221 is a room-temperature curing silicone resin-based water-based paint. This allows the first layer 220 to primarily exhibit adhesion to the coating rubber layer 11, deformation compliance, and ozone resistance, while the second layer 221 primarily exhibits UV resistance, heat resistance, and water resistance. Both the first and second coating materials are water-based, making them environmentally friendly. Furthermore, a primer layer 24 is disposed between the filler 21 and the first layer 220, improving adhesion between the filler 21 and the first layer 220. Furthermore, a protective film 22 is disposed over the entire front surface of the coating rubber layer 11. This improves resistance to degradation factors such as water, oxygen, ozone, and light not only in the repair area 2 but also across the entire front surface, thereby suppressing future cracking. As a result, the rubber bearing 1's lifespan can be extended.

[0040] According to the repair method of this embodiment, the width w of the recess 20 formed by removing the crack 17 is made larger than the depth d. As a result, even if the rubber bearing 1 undergoes repeated shear deformation, the distortion generated in the recess 20 is small, and the degree of opening and closing of the recess 20 is small, so it is possible to prevent the filler 21 from being extruded from the recess 20. In addition, the recess 20 has a C-shaped curved surface in its cross section in the vertical direction. This makes it easy to fill the entire recess 20 with the filler 21, and stress during deformation is less likely to concentrate in the recess 20, which effectively prevents the filler 21 from peeling off. A rubber bearing 1 of the present disclosure that has been repaired as shown in this embodiment is prevented from causing cracks to progress and has excellent durability.

[0041] The above describes one embodiment of the repair method for a rubber product for construction and the rubber product for construction having a repaired portion according to the present disclosure. However, the present disclosure is not limited to the above embodiment. Various modifications and improvements can be made by those skilled in the art.

[0042] <Repair method for rubber products for construction> The repair method of the present disclosure includes a cutting step, a filling step, and a coating step.

[0043] [Cutting process] This process involves cutting an area containing a crack that has occurred on the surface of a rubber product for construction (hereinafter sometimes simply referred to as a "rubber product") to form a recess in the surface of the rubber product. Here, "the surface of the rubber product for construction" means the surface of the rubber layer that is exposed to the outside. For example, in the case of a rubber bearing, this includes the surface of the rubber layer that constitutes a laminate with a hard plate or the like, and the surface of the covering rubber layer that is arranged around the laminate. The size of the crack to be repaired is not limited. For example, the depth of the crack may be 0.2 mm or less, or may be greater than 0.2 mm and less than 1 mm. Furthermore, a relatively deep crack of 1 mm or greater but less than 10 mm is also acceptable.

[0044] The cutting process may be performed so as to remove part or all of the crack. The depth of the recess may be smaller, the same as, or larger than the depth of the crack. The vertical length of the recess opening is preferably equal to or greater than the depth of the recess. Here, the "vertical length of the recess opening" refers to the "minimum vertical length of the recess opening." The shape of the recess is not limited. As an alternative to the above-described embodiment, FIGS. 10A to 10C show examples of vertical cross-sectional shapes of recesses. FIGS. 10A to 10C are partial cross-sectional views of a rubber bearing during the cutting process, corresponding to FIG. 5. The cross-section of recess 30 shown in FIG. 10A is rectangular. Recess 30 is a rectangular groove whose internal space has a constant vertical length from the opening toward the depth. The cross-section of recess 31 shown in FIG. 10B is tapered. The cross-section of recess 32 shown in FIG. 10C is V-shaped. From the viewpoint of making it easier to fill the entire recess with the filler, it is desirable that the recess be formed so that the vertical cross-sectional shape is semicircular, elliptical, C-shaped, tapered, V-shaped, etc., and the vertical length of the internal space decreases from the opening toward the depth. Furthermore, from the viewpoint of making it easier to spread the filler throughout the entire recess, avoiding stress concentration when the rubber product is deformed, and suppressing peeling of the filler, it is desirable to form the recess into a curved surface.

[0045] [Filling process] This step is a step of filling the recesses formed in the previous step with a filler. It is desirable to use a material as the filler that has excellent adhesion to the rubber layer, flexibility, and excellent followability to deformation. Examples include polyurethane resin and polyurea resin. One or more resins may be used. Furthermore, considering workability on site, it is desirable to use a resin that can be cured at room temperature. Furthermore, it is desirable to use a resin that has excellent weather resistance, such as ozone resistance. For example, it is desirable to use one or more resins selected from room-temperature-curing polyurethane resins and room-temperature-curing polyurea resins.

[0046] Furthermore, as in the above embodiment, a modification treatment step may be performed after the cutting step and before this step. The modification treatment may be any treatment that can improve adhesion depending on the type of filler. For example, when a material containing isocyanate is used as the filler, it is preferable to apply a chlorine-based surface modifier such as a trichloroisocyanuric acid-containing liquid, which can impart functional groups that react with isocyanate to the rubber layer.

[0047] [Coating process] This process involves applying a coating material to cover the opening of the recess filled with filler to form a protective film. The size and thickness of the protective film are not limited as long as it covers the opening of the recess, i.e., the filler material filled in the recess. The protective film can be formed not only on the area corresponding to the recess but also on a wider area. For example, the protective film may be formed on the entire surface where the recess is formed (the repaired surface). In addition, the protective film may be formed on surfaces other than the repaired surface. Placing a protective film on the entire repaired surface, or even the entire surface exposed to the outside, can improve the resistance of the entire surface to degradation factors, thereby effectively extending the lifespan of rubber products for construction. It is desirable to use a material with excellent ozone resistance, UV resistance, water resistance, heat resistance, and cold resistance. Materials that have excellent adhesion to the rubber layer and are flexible and highly adaptable to deformation are also suitable. Furthermore, considering on-site workability, materials that can be cured at room temperature are desirable. Water-based materials are also environmentally friendly. For example, paints containing polyurethane resin, silicone resin, etc. are suitable.

[0048] The protective film may be one layer or two or more layers. Regardless of whether the components are the same or different, thickening the protective film by using two or more layers improves its resistance to deterioration factors. Furthermore, using two or more layers allows for different functions to be performed by each layer, enhancing the repair effect. For example, the protective film may be a laminated film consisting of a first layer formed from a first coating material and a second layer formed from a second coating material. In this case, it is desirable to use a polyurethane resin-based paint as the first coating material, with the first layer positioned on the recessed portion side, and a silicone resin-based paint as the second coating material, with the second layer positioned outside the first layer. In this configuration, the first layer primarily provides adhesion to the rubber layer, ability to follow deformation of the rubber layer, and ozone resistance, while the second layer primarily provides UV resistance, heat resistance, and water resistance.

[0049] The thickness of the protective film may be any thickness that allows it to exhibit desired properties such as weather resistance. For example, the overall thickness of the protective film is preferably 50 μm or more. On the other hand, if the protective film is too thick, it will be prone to peeling during deformation. Therefore, the overall thickness of the protective film is preferably 230 μm or less, and even more preferably 200 μm or less. Furthermore, if the protective film is composed of two layers, it is preferable that the first layer located on the recess side be 25 μm to 150 μm in thickness from the viewpoint of adhesion with the rubber layer, and the second layer located on the outer side be 25 μm to 80 μm in thickness from the viewpoint of weather resistance, etc.

[0050] Furthermore, as in the above embodiment, a primer application step may be performed after the filling step and before this step. The primer may be any primer that can enhance the adhesion of the coating material (protective film) depending on the type of rubber layer, filler, coating material, etc. For example, when using a material containing isocyanate as the filler and a material containing polyurethane resin as the coating material, it is preferable to use a urethane-based or chlorinated olefin-based material as the primer, as this improves the adhesion between the two. The primer layer may be formed so as to cover the opening of the recess filled with the filler, or may be formed over the entire surface on which the recess is formed (the surface on which the repair has been performed).

[0051] <Rubber products for buildings> The types, configurations, etc. of rubber products for buildings to which the repair method of the present disclosure is applied are not particularly limited. For example, rubber bearings, anti-vibration rubber products, etc. may be mentioned. Among these, in the case of a rubber bearing having a laminate in which rubber layers and rigid plates are alternately laminated as in the above form, the rubber layer is manufactured from a rubber composition suitable for the rubber bearing. As the rubber component, in addition to natural rubber, diene synthetic rubbers such as isoprene rubber, styrene-butadiene rubber, butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, and halogenated butyl rubber may be mentioned. Additives blended in addition to the rubber component include vulcanizing agents, vulcanization accelerators, vulcanization accelerator aids, reinforcing materials such as carbon black, softening agents such as oil, plasticizers, anti-aging agents, stabilizers, flame retardants, etc. As the rigid plate, metal plates such as rolled steel plates and iron plates, rigid plastic plates, etc. may be used. When a plurality of rigid plates are arranged, their materials may all be the same, or those of different materials may be combined. For example, the rigid plate arranged between rubber layers and the rigid plate arranged for attaching the laminate to another member can be composed of those of different materials. When the rubber bearing has a coating rubber layer, the components of the coating rubber layer may be the same as or different from those of the rubber layer constituting the laminate. As long as the coating rubber layer is integrated with the laminate, it may be continuous with the rubber layer or separate. The shape of the rubber bearing is appropriately selected according to the application, such as prismatic, cylindrical, elliptical cylindrical, etc.

Examples

[0052] Next, the present disclosure will be described more specifically with reference to examples.

[0053] <FEM analysis> As an example of a rubber product for a building, the crack and opening behavior of a recess during shear deformation of a rubber bearing was analyzed using FEM (finite element method).

[0054] [Rubber bearing model] The rubber bearing used as the analysis model was the one shown in Figures 1 and 2. The rubber bearing model was a rectangular parallelepiped with dimensions of 1200 mm in length, 1200 mm in width, and 430 mm in thickness. The rubber bearing model consisted of a laminate and a covering rubber layer, and had no repaired sections. The laminate consisted of six 50 mm thick rubber layers, alternately layered with metal plates. The total thickness of the rubber layers was 300 mm. The covering rubber layers were continuous with the rubber layers and were arranged to surround the sides of the laminate. The covering rubber layers were 10 mm thick. Both the rubber layers and the covering rubber layers were made of a rubber composition containing natural rubber.

[0055] (1) Model 1 Model 1 was created by inserting a crack that ran linearly in the left-right direction into the covering rubber layer on the front of the rubber bearing model (see Figure 1 above for orientation). The crack width (vertical length) was 1 mm, the depth was 10 mm, and the left-right length was 1200 mm. The crack was located 12 mm from the top end, at the point where the strain was greatest in a preliminary analysis of a model without a crack.

[0056] (2) Model 2 Model 2 was created by cutting out the area containing the crack on the front surface of Model 1 to form a recess. The width of the recess (vertical length, w in Figure 3 above) was 10 mm, with 5 mm above and below the crack as the center, and the depth of the recess (d in Figure 3 above) was 10 mm. The length of the recess in the horizontal direction was 1200 mm. The shape of the recess was an arc with a curvature radius of 5 mm.

[0057] (3) Model 3 Similar to Model 2, Model 3 was created by cutting out the area containing the crack on the front surface of Model 1 to form a recess. The width of the recess was 20 mm, with 10 mm above and 10 mm below the crack, for a total depth of 10 mm. The length of the recess in the left-right direction was 1200 mm. The shape of the recess was an arc with a curvature radius of 10 mm.

[0058] [FEM analysis results] FEM analysis was used to determine the crack or recess opening relative to the horizontal deformation (strain) when each model was subjected to longitudinal shear deformation. In Model 1, the crack opening closed completely under compression and narrowed to 11 mm (1000% change) under tension. This indicates that if the crack remains, even if filler is added, it will be pushed out during compression and will be unable to accommodate deformation during tension. In contrast, in Model 1, the recess opening reached a maximum of 7 mm (-30% change) under compression and 34 mm (240% change) under tension. In Model 2, the recess opening reached a maximum of 16 mm (-20% change) under compression and 51 mm (155% change) under tension. These results confirm that cutting out the crack area to form a recess of a specified size facilitates filling with filler, prevents the filler from being pushed out during compression, and allows the filler to easily accommodate deformation due to the lack of excessive opening during tension.

[0059] <Evaluation of filler materials> [Deformation tracking ability] First, hourglass-shaped rubber samples (cylindrical with a constricted portion in the vertical direction) were prepared using the same rubber composition containing natural rubber as the previous model. The top and bottom diameters of the rubber samples were 35 mm, and the height was 45 mm. Next, the smallest vertical diameter of the rubber sample was cut using a hand grinder to form a linear recess with a width (vertical length) of 5 mm and a depth of 5 mm. The recess had an arc shape with a curvature radius of 2.5 mm. One recess was unfilled and the other was filled, and each was subjected to a vibration test. The rubber sample without filler is referred to as Sample 1, and the rubber sample with filler is referred to as Sample 2. The filler used in Sample 2 was a room-temperature curing polyurethane resin. In the vibration test, each sample was subjected to vertical compression and tension deformation by vibrating at a predetermined displacement of 1 Hz 500 times. The amount of vertical displacement was set within a range that included the amount of shear deformation equivalent to a "Level 1 earthquake motion" as described in the Road Bridge Bearing Handbook. After the vibration test, each sample was visually inspected for cracks, and in the case of Sample 2, for the presence or absence of lifting or peeling of the filler material. The results are shown in Table 1.

[0060] [Table 1]

[0061] As shown in Table 1, in Sample 1 without filler, no cracks occurred regardless of the amount of displacement. Similarly, in Sample 2 with filler, no cracks occurred regardless of the amount of displacement, and the filler did not lift or peel off. From the above, it was confirmed that filler containing polyurethane resin has high adhesion to rubber materials and is excellent in following compressive and tensile deformation. It was also confirmed that a structure in which a filler containing polyurethane resin is filled into recesses of a specified size has excellent durability against deformation.

[0062] [Shear deformability] First, a rectangular parallelepiped rubber sample measuring 130 mm in length, 130 mm in width, and 75 mm in thickness was prepared using the same rubber composition as the previous rubber bearing model. Next, two of the side surfaces of the rubber sample (the front and left side) were ground using a hand grinder, and linear recesses measuring 10 mm in width (vertical length), 10 mm in depth, and 50 mm in horizontal length were formed on each surface. The recesses were arc-shaped with a 5 mm radius of curvature. The recesses were then filled with a filler containing a room-temperature-curing polyurethane resin and subjected to a shear deformation test. The rubber sample prepared in this manner is referred to as Sample 3. The shear deformation test was conducted under the following two conditions: In Test 1, Sample 3 was subjected to horizontal reciprocating motion 5,000 times at a shear deformation of ±70%; and in Test 2, Sample 3 was subjected to horizontal reciprocating motion 500 times at a shear deformation of ±150%. In both tests, the front of Sample 3 was perpendicular to the direction of reciprocating motion, and the left side was parallel to the direction of reciprocating motion. The shear deformation was set to reproduce the deformation of the recess in the model used for FEM analysis. For example, Sample 3 was moved horizontally by 33 mm to achieve 70% of the shear deformation of a 430 mm-thick rubber bearing model (total rubber layer thickness: 300 mm). After the shear deformation test, Sample 3 was visually inspected for cracks and for any loose or peeling filler material. The results are shown in Table 2.

[0063] [Table 2]

[0064] As shown in Table 2, Sample 3 did not develop cracks, and the filler did not lift or peel, even after repeated shear deformation. From the above, it was confirmed that the filler containing polyurethane resin has high adhesion to the rubber material and excellent compliance with shear deformation. Furthermore, it was confirmed that the structure in which a recess of a specified size is filled with a filler containing polyurethane resin has excellent durability against deformation.

[0065] <Evaluation of coating materials> First, a rectangular rubber sample measuring 240 mm in length, 240 mm in width, and 153 mm in thickness was prepared using the same rubber composition as the previous rubber bearing model. Next, a one-component, room-temperature-curing polyurethane resin-based water-based paint was applied to the entire surface of the rubber sample to form a 60 μm-thick polyurethane layer. Subsequently, a two-component, room-temperature-curing silicone resin-based water-based paint was applied to the formed polyurethane layer to form a 35 μm-thick silicone layer. In this way, a coated sample was prepared in which the entire rubber sample was covered with a protective film consisting of a polyurethane layer and a silicone layer, in that order from the inside out.

[0066] [Shear deformability] A shear deformation test was conducted on the prepared coated sample by reciprocating it horizontally 5,000 times at a shear deformation of 70%. Visual inspection of the protective film for cracks, lifting, or peeling was conducted, including during the shear deformation test. No cracks, lifting, or peeling were observed in the protective film, even after 5,000 shear deformations. These findings confirm that the protective film, consisting of two layers (a polyurethane layer and a silicone layer), has high adhesion to rubber materials and excellent compliance with shear deformation.

[0067] [Ozone resistance] The prepared coated samples were placed in an ozone bath at 40°C and an ozone concentration of 200 pphm, and visually inspected for lifting and peeling of the protective film at predetermined intervals. The prepared coated samples were also thermally aged at 70°C for 1,000 hours, and then placed in an ozone bath at 40°C and an ozone concentration of 200 pphm. The protective film was visually inspected for lifting and peeling at predetermined intervals. For comparison, a rubber sample without a protective film was also placed in the ozone bath and visually inspected for cracks. The results are shown in Table 3.

[0068] [Table 3]

[0069] As shown in Table 3, the protective film of the coated samples did not peel or peel off even after 168 hours of exposure to an ozone atmosphere, regardless of whether or not they had been heat-aged. In contrast, the rubber sample without a protective film developed cracks 24 hours after ozone exposure and broke 48 hours after, even without heat aging. After heat aging, the sample broke 24 hours after ozone exposure. From the above, it was confirmed that the protective film consisting of two layers, a polyurethane layer and a silicone layer, has excellent ozone resistance. [Industrial Applicability]

[0070] The repair method for rubber products for construction and the rubber products for construction disclosed herein are applicable to rubber products placed in structures such as buildings, bridges, and elevated roads. In particular, they are suitable for rubber bearings placed between superstructures and substructures for purposes such as seismic isolation. They are also suitable for vibration-damping rubber products that are difficult to replace due to workability, cost, and other factors. [Explanation of symbols]

[0071] 1: rubber bearing (rubber product for construction), 2: repair part, 10: laminate, 11: coated rubber layer, 12: rubber layer, 13: middle hard plate, 14: upper hard plate, 15: lower hard plate, 16: front surface of rubber bearing, 17: crack, 20: recess, 21: filler, 22: protective film, 23: modified layer, 24: primer layer, 30, 31, 32: recess, 80: upper mounting plate, 81: lower mounting plate, 220: first layer, 221: second layer.

Claims

1. a cutting step of cutting a region including a crack generated on the surface of the rubber product for construction to form a recess; a filling step of filling the recess with a filler; a coating step of applying a coating material to cover the opening of the recess to form a protective film; and A repair method for rubber products for construction, characterized in that the vertical length of the opening of the recess is equal to or greater than the depth of the recess.

2. 2. The repair method for a rubber product for construction according to claim 1, wherein in the cutting step, the recess is formed so that the vertical length of the internal space decreases from the opening toward the depth direction.

3. 2. The repair method for a rubber product for construction according to claim 1, wherein the recessed portion has a curved surface.

4. 2. The repair method for a rubber product for construction according to claim 1, wherein the depth of the crack is less than 10 mm.

5. 2. The repair method for a rubber product for construction according to claim 1, wherein the filler comprises at least one material selected from the group consisting of room-temperature curing polyurethane resin and room-temperature curing polyurea resin.

6. 2. The repair method for a rubber product for construction according to claim 1, wherein the coating material comprises a polyurethane resin.

7. 2. The repair method for rubber products for construction according to claim 1, wherein the coating material comprises a first coating material and a second coating material of different types, and the protective film is laminated in the thickness direction and comprises a first layer formed from the first coating material and a second layer formed from the second coating material.

8. 8. A repair method for rubber products for construction according to claim 7, wherein the first layer is disposed on the recessed side, the first coating material comprises a polyurethane resin, and the second layer is disposed on the outside of the first layer, and the second coating material comprises a silicone resin.

9. 2. The repair method for a rubber product for construction according to claim 1, wherein the protective film is formed on the entire surface on which the recess is formed.

10. 2. The repair method for a rubber product for construction according to claim 1, wherein the rubber product for construction is a rubber bearing.

11. A rubber product for construction having a repaired portion, The repaired portion is a recess formed by cutting the surface of the rubber product for construction before repair; a filler filled in the recess; a protective film covering the opening of the recess; and A rubber product for construction, characterized in that the vertical length of the opening of the recess is equal to or greater than the depth of the recess.

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