Corrosion-preventive composition, corrosion-preventive sheet, and method for preventing corrosion of steel structures

Abstract

To provide an anticorrosive composition that is excellent in anticorrosive effect, an anticorrosive sheet and an anticorrosion method for structural steelwork.SOLUTION: An anticorrosive composition comprises: an asphalt substrate containing asphalt and a styrenic resin; and one or more kinds of modifiers selected from a styrene / butadiene / styrene block copolymer and a styrene / ethylene / butylene / styrene block copolymer, with a penetration at a product temperature of 25±0.1°C being 60 to 500. An anticorrosive sheet is used by being arranged on a surface of a target object that is to be protected against corrosion, and has an anticorrosive layer to make contact with the surface of the target object, the anticorrosive layer being formed of the anticorrosive composition according to the present invention. An anticorrosion method for structural steelwork has a step of sticking the anticorrosive sheet to the surface of the structural steelwork. The invention is particularly useful for anticorrosion of a water-area structure.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a corrosion prevention composition and a corrosion prevention sheet using the same.

Background Art

[0002] Steel structures including steel pipe piles, steel sheet piles, steel pipe sheet piles, etc. installed on the shore walls, piers, bridge piers, etc. of the sea or rivers are likely to corrode because they are exposed to a severe deterioration environment for a long time, and thus are usually subjected to corrosion prevention treatment. Conventionally, as the corrosion prevention treatment, application of a corrosion prevention composition, attachment of a corrosion prevention sheet, etc. have been performed. For example, Patent Documents 1 and 2 describe a corrosion prevention sheet in which a corrosion prevention material made of a mixture of rubber and asphalt is disposed on the surface of a sheet-like exterior material (base material sheet) made of synthetic rubber or the like. Patent Documents 1 and 2 do not describe the specific composition of the corrosion prevention material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, petrolatum-based corrosion prevention materials mainly composed of petrolatum have been widely used as corrosion prevention materials. However, petrolatum-based corrosion prevention materials have the following problems: 1) a phenomenon (oil leakage) in which oil leaks out over time occurs; 2) in a corrosion prevention sheet formed by applying a petrolatum-based corrosion prevention material to the surface of a base material sheet, defective portions where the corrosion prevention performance is reduced due to uneven application occur; 3) after construction, a part of the corrosion prevention material deforms, such as sagging downward due to its own weight. There is a demand for a corrosion prevention material that can exhibit a corrosion prevention effect equal to or better than that of petrolatum-based corrosion prevention materials without causing such problems.

[0005] The object of the present invention is to provide a corrosion prevention technology that can overcome the drawbacks of the conventional technology described above, and more specifically, to provide a corrosion prevention composition, a corrosion prevention sheet, and a method for corrosion prevention of steel structures that have excellent corrosion prevention effects. [Means for solving the problem]

[0006] The inventors of this invention have investigated various new corrosion inhibitors to replace petrolatum-based corrosion inhibitors and have found that a waterproof sheet using asphalt-based material in the waterproof layer is useful. This waterproof sheet has been conventionally used for purposes such as covering the substrate of buildings or structures. Further investigation based on this waterproof sheet has revealed that a composition containing an asphalt base material including asphalt and styrene-based resin, a specific modifier, and a specific penetration degree exhibits corrosion protection effects equivalent to or better than petrolatum-based corrosion inhibitors, and also has excellent workability on the object to be protected.

[0007] The present invention is based on the above findings and is a corrosion-preventive composition comprising an asphalt base material containing asphalt and a styrene-based resin, and one or more modifiers selected from styrene-butadiene-styrene block copolymer and styrene-ethylene-butylene-styrene block copolymer, wherein the penetration degree at a product temperature of 25±0.1℃ is 60 to 500. The present invention also relates to a method for producing the corrosion-preventive composition described above, comprising the steps of mixing the asphalt base material and the modifier, and stirring the mixture while heating it.

[0008] Furthermore, the present invention is based on the above findings and is a corrosion-resistant sheet having a corrosion-resistant layer that is placed on the surface of a material to be protected from corrosion and comes into contact with the surface of the material to be protected from corrosion when in use, wherein the corrosion-resistant layer is made of the corrosion-resistant composition of the present invention described above.

[0009] Furthermore, the present invention is based on the above findings and is a method for preventing corrosion of steel structures, comprising the step of attaching the corrosion-preventive sheet of the present invention to the surface of the steel structure. [Effects of the Invention]

[0010] According to the present invention, a corrosion-preventive composition with excellent corrosion-preventive effect, a corrosion-preventive sheet, and a method for preventing corrosion of steel structures are provided. [Modes for carrying out the invention]

[0011] The corrosion-preventive composition of the present invention comprises at least an asphalt base material and a modifier. The modifier is one or more selected from styrene-butadiene-styrene block copolymer (SBS) and styrene-ethylene-butylene-styrene block copolymer (SEBS).

[0012] The asphalt substrate comprises at least asphalt and a styrene-based resin. In the asphalt substrate, the asphalt and the styrene-based resin are inseparable. The asphalt substrate is typically manufactured by heating and mixing the asphalt and the styrene-based resin.

[0013] The aforementioned asphalt can be any asphalt conventionally used for road paving, waterproofing sheets, etc., without any particular restrictions. Examples include petroleum asphalt such as straight asphalt and blown asphalt; and natural asphalt such as lake asphalt, rock asphalt, oil sand, and asphaltite. One of these types can be used alone or in combination of two or more types. Among these asphalts, straight asphalt is particularly preferred.

[0014] Examples of the styrene-based resin include homopolymers formed by polymerizing styrene-based monomers, and copolymers formed by copolymerizing styrene-based monomers with other monomers copolymerizable thereto. One of these can be used alone or in combination of two or more. When the styrene-based resin is a copolymer, there are no restrictions on the polymerization mode, but it is typically a block copolymer. A preferred specific example of the styrene-based resin is SBS.

[0015] The asphalt content in the asphalt base material is preferably 10 to 90% by mass, more preferably 40 to 90% by mass, based on the total mass of the asphalt base material. The styrene-based resin content in the asphalt substrate is preferably 3.5 to 30% by mass, more preferably 5 to 25% by mass, based on the total mass of the asphalt substrate.

[0016] The content of the asphalt base material in the corrosion-preventive composition of the present invention is preferably 0.1 to 99.9% by mass, more preferably 60 to 99.9% by mass, and even more preferably 90.0 to 99.9% by mass, based on the total mass of the corrosion-preventive composition.

[0017] The content of the modifier (SBS and / or SEBS) in the corrosion-preventive composition of the present invention is preferably 3.5 to 30% by mass, more preferably 5 to 15% by mass, based on the total mass of the corrosion-preventive composition.

[0018] The corrosion-preventive composition of the present invention may contain a tackifier. This can further improve the tackiness of the corrosion-preventive composition, thereby improving its adhesion to the object to be protected from corrosion, and consequently improving its corrosion-preventive effect. Examples of the tackifier include petroleum resins such as aromatic petroleum resins, alicyclic petroleum resins, and aliphatic petroleum resins, and one of these can be used alone or in combination of two or more. Among these tackifiers, aliphatic hydrocarbon resins are particularly preferred.

[0019] The content of the tackifier in the corrosion-preventive composition of the present invention is preferably 0.1 to 20 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the asphalt base material in the corrosion-preventive composition.

[0020] The anticorrosive composition of the present invention may contain a rigidity-imparting agent. As a result, the rigidity of the anticorrosive composition is improved, and the workability can be improved. Examples of the rigidity-imparting agent include metal particles such as iron, copper, tin, zinc, nickel, and stainless steel; metal oxide particles such as iron oxide, iron sesquioxide, iron tetroxide, ferrite, tin oxide, zinc oxide, zinc white, copper oxide, and aluminum oxide; metal salt particles such as calcium carbonate, calcium bicarbonate, barium carbonate, calcium sulfate, barium sulfate, aluminum sulfate, calcium sulfite, and magnesium hydroxide; mineral particles such as steelmaking slag, mica, clay, talc, wollastonite, diatomaceous earth, silica sand, and pumice powder; and inorganic fibers such as glass fiber and carbon fiber. One of these can be used alone or in combination of two or more. Among these rigidity-imparting agents, calcium carbonate is particularly preferable.

[0021] The content of the rigidity-imparting agent in the anticorrosive composition of the present invention is preferably 10 to 60 parts by mass, more preferably 20 to 50 parts by mass, based on 100 parts by mass of the asphalt base material in the anticorrosive composition.

[0022] The anticorrosive composition of the present invention is characterized in that the penetration at a product temperature of 25 ± 0.1 °C is 60 to 500. The penetration can be measured in accordance with JIS K 2207-1996 "Petroleum Asphalt". The penetration is a physical property value indicating the hardness of the anticorrosive composition. The smaller the value of the penetration, the harder the anticorrosive composition, and the larger the value of the penetration, the softer the anticorrosive composition. If the penetration is less than 60, the adhesiveness of the anticorrosive composition may decrease. If the penetration exceeds 500, the rigidity of the anticorrosive composition decreases, and in any case, the workability of the anticorrosive composition may decrease. The penetration is preferably 30 to 500, more preferably 30 to 80. The penetration can be adjusted by adjusting the content of asphalt and / or styrene resin, which are the main components of the asphalt base material.

[0023] The anticorrosive composition of the present invention is produced through a process of mixing the asphalt base material and the modifier and stirring the mixture while heating it. The mixture may contain optional components such as the tackifier and the rigidity imparting agent described above. The heating temperature of the mixture may be any temperature at which the asphalt and the styrene resin contained in the mixture can melt, and may be appropriately set according to the type of the asphalt and the styrene resin, etc. Typically, it is preferably 40 to 300 °C, more preferably 80 to 200 °C. The above process can be carried out using a mixer used when producing a conventionally known composition mainly composed of asphalt.

[0024] The asphalt base material used in the above process is produced using asphalt and a styrene resin prior to the process. In the above process, if asphalt and a styrene resin are used separately instead of the asphalt base material, the anticorrosive composition of the present invention cannot be obtained. The manufacturing method of the anticorrosive composition of the present invention may include a first step of manufacturing an asphalt base material, and a second step of mixing the asphalt base material manufactured in the first step and the modifier and stirring the mixture while heating it.

[0025] The anticorrosive composition of the present invention can also be used as an amorphous paste-like anticorrosive paint having fluidity. However, when it is formed into a sheet and used as an anticorrosive sheet, the characteristics of the anticorrosive composition are utilized, which is advantageous not only in terms of the anticorrosive effect but also in terms of workability. Therefore, it is preferable. Hereinafter, the anticorrosive sheet of the present invention will be described.

[0026] The anticorrosive sheet of the present invention is used by being disposed on the surface of the object to be protected. It has an anticorrosive layer that contacts the surface of the object to be protected during use, and the anticorrosive layer is composed of the anticorrosive composition of the present invention described above. Typically, the anticorrosive layer has adhesiveness and can be attached to the surface of the object to be protected.

[0027] The thickness of the anticorrosive layer is not particularly limited. From the viewpoint of the balance between the anticorrosive effect and workability, it is preferably 1 to 10 mm, more preferably 2 to 3 mm.

[0028] The corrosion-resistant sheet of the present invention may be in a form that includes only a corrosion-resistant layer (hereinafter also referred to as the "first embodiment"), or it may include other layers in addition to the corrosion-resistant layer. A specific example of the latter is a form that includes a non-adhesive base sheet, and the corrosion-resistant layer is provided on the surface of the base sheet (hereinafter also referred to as the "second embodiment"). The second embodiment is typically a two-layer structure in which the corrosion-resistant layer is arranged on only one side of the base sheet.

[0029] In the second embodiment, the base sheet can be a non-adhesive sheet material to which the corrosion-resistant layer can be fixed, such as a film, woven fabric, nonwoven fabric, paper, or aluminum foil. A particularly preferred base sheet is a film made of synthetic resin. Examples of synthetic resins used as the forming material for the film base sheet include polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), and one of these can be used alone or in combination of two or more. Among these synthetic resins, PE is particularly preferred.

[0030] The thickness of the base sheet is not particularly limited, but from the viewpoint of balancing strength and workability, it is preferably 0.001 to 0.1 mm, and more preferably 0.005 to 0.015 mm.

[0031] The corrosion-resistant sheet of the first embodiment can be manufactured by forming a molten corrosion-resistant composition into a sheet. The corrosion-resistant sheet of the second embodiment can be manufactured by applying a molten corrosion-resistant composition to a base sheet, and then cooling and solidifying the corrosion-resistant composition. Known application methods, such as bar coating, can be used for applying the molten corrosion-resistant composition to the base sheet.

[0032] The corrosion-preventive sheet of the present invention is suitable for corrosion prevention of various steel structures such as steel pipe piles, steel sheet piles, and steel sheet piles. A method for corrosion prevention of steel structures using the corrosion-preventive sheet of the present invention includes at least the step of attaching the corrosion-preventive sheet to the surface (surface to be protected from corrosion) of the steel structure. Typically, such a corrosion prevention method is completed by first performing surface treatment such as removing dirt from the surface to be protected, and then attaching the corrosion-preventive sheet so that its corrosion-preventive layer is in contact with the surface to be protected from corrosion.

[0033] If necessary, the outer surface of the corrosion-resistant sheet attached to the surface to be protected (the side opposite to the surface to be protected) may be covered with a protective cover. The protective cover is for protecting the corrosion-resistant sheet from external impacts, and examples include synthetic resin protective covers; and metallic protective covers made of seawater-resistant stainless steel, titanium, etc. A preferred example of a protective cover is one made of fiber-reinforced plastic. Fiber-reinforced plastic contains resins such as thermosetting resins and thermoplastic resins, and fibers such as glass fibers, carbon fibers, and organic fibers.

[0034] The corrosion-preventive sheet of the present invention can be installed simply by attaching it to the surface to be protected via a corrosion-preventive layer, and moreover, it is less prone to the problems seen with petrolatum-based corrosion inhibitors and can exhibit corrosion protection effects equivalent to or better than those of petrolatum-based corrosion inhibitors. The corrosion-preventive sheet of the present invention has an elastic corrosion-preventive layer that conforms well to the surface to be protected, so the corrosion-preventive layer adheres well to the surface to be protected, and this is one of the reasons why the corrosion-preventive sheet exhibits excellent corrosion protection effects. In particular, a corrosion-resistant sheet (a type of the second embodiment) in which a corrosion-resistant layer is arranged on only one side of the base sheet can be stored in the form of a sheet roll, which is formed by winding a long, strip-shaped corrosion-resistant sheet into a roll before use, making it easy to secure storage space. Furthermore, when in use, the side of the corrosion-resistant sheet facing the user (the side opposite to the surface to be protected from corrosion) is made of the base sheet and is not adhesive, so problems such as the corrosion-resistant sheets sticking together during application to the surface to be protected from corrosion are less likely to occur, resulting in excellent workability.

[0035] The corrosion-preventive composition and corrosion-preventive sheet of the present invention can be used for corrosion prevention of various structures, but are particularly useful for corrosion prevention of structures in aquatic environments. Here, "structures in aquatic environments" refers to structures containing steel members installed in or near the ocean or rivers. Specific examples include steel structures such as steel pipe piles, steel sheet piles, and steel pipe sheet piles installed on seawalls, piers, bridge piers, etc., in the ocean or rivers. [Examples]

[0036] [Example 1] The corrosion-preventive composition of Example 1 was produced by adding asphalt base material, SBS (modifier), aliphatic hydrocarbon resin (tackifier), and calcium carbonate (rigidity modifier) ​​to a mixer and stirring while heating the contents of the mixer until the temperature of the contents reached 180°C. The corrosion-preventive composition of Example 1 had a softening point of 138°C, a Frars brittle point of -38°C, and a viscosity of 400 Pa·S at a temperature of 200°C. In the production of the corrosion-preventive composition of Example 1, 7.9 parts by mass of SBS were used per 100 parts by mass of asphalt substrate, 2.6 parts by mass of aliphatic hydrocarbon resin were used per 100 parts by mass of asphalt substrate, and 47.9 parts by mass of calcium carbonate were used per 100 parts by mass of asphalt substrate. The aforementioned asphalt base material was manufactured using straight asphalt with a penetration degree of 150-200 at a product temperature of 25±0.1℃ and SBS as raw materials. These raw materials were placed in a mixer and stirred and mixed while heating the contents of the mixer until the product temperature reached 180℃. In the asphalt base material, the straight asphalt content was 82% by mass of the total mass of the asphalt base material, and the SBS content was 18% by mass of the total mass of the asphalt base material.

[0037] [Comparative Example 1] Comparative Example 1's corrosion-preventive composition was produced by adding straight asphalt with a penetration degree of 150-200 at a product temperature of 25±0.1℃, SBS (modifier), and aliphatic hydrocarbon resin (tackifier) ​​to a mixer, and stirring and mixing the contents while heating them to a product temperature of 180℃. The corrosion-preventive composition of Comparative Example 1 had a softening point of 145℃, a Frars brittle point of -32℃, and a viscosity of 1650 Pa·S at a product temperature of 200℃.

[0038] [Comparative Example 2] A commercially available blown asphalt (manufactured by Showa Seki Chemical Co., Ltd., product name "Fujiclean") was used as the corrosion protection composition for Comparative Example 2. The corrosion protection composition of Comparative Example 2 had a softening point of 106°C, a Frass embrittlement point of -16°C, and a viscosity of 360 Pa·s at a product temperature of 200°C.

[0039] [Manufacturing of corrosion-resistant sheets] A corrosion-resistant sheet was manufactured in which a corrosion-resistant layer 2 to 2.5 mm thick was arranged on only one side of a PE film (thickness 0.010 mm) used as a base sheet, by applying a molten corrosion-resistant composition to one side and drying it (as in the second embodiment). One of the corrosion-resistant compositions of Example 1 and Comparative Examples 1 and 2 was used as the corrosion-resistant composition. Release paper was laminated to the surface of the corrosion-resistant layer on the manufactured corrosion-resistant sheet (the surface opposite to the base sheet). When using the corrosion-resistant sheet, this release paper is peeled off to expose the corrosion-resistant layer.

[0040] [Evaluation Test] The tensile strength and adhesive strength of the corrosion-resistant sheets of Example 1 and Comparative Example 1 were measured using the methods described below. Furthermore, the corrosion-resistant performance (corrosion rate) of the corrosion-resistant sheets of each example and comparative example was evaluated using the methods described below. The results are shown in Table 1 below.

[0041] <Method for evaluating tensile strength> A dumbbell-shaped sample (No. 2) is punched out from a corrosion-resistant sheet with laminated release paper using a punching blade. The punched-out corrosion-resistant sheet is then pressed in the thickness direction to adjust its thickness to 1.0 ± 0.1 mm, and this is used as the measurement sample. The distance between the chucks of the tensile testing machine is set to 60 mm, and the measurement sample is fixed between the chucks. The measurement sample is then stretched by increasing the distance between the chucks at a speed of 500 mm / min, and the tensile load at the point when the measurement sample breaks is recorded. Based on this, the tensile strength of the measurement sample (unit: N / mm²) is determined. 2 The tensile strength is calculated. A higher tensile strength value indicates that the corrosion-resistant sheet has strong resistance to tension and possesses sufficient strength for practical use.

[0042] <Method for evaluating adhesive strength> A corrosion-resistant sheet with laminated release paper is pressed in the thickness direction to adjust its thickness to 1.0 ± 0.1 mm, and this is used as the measurement sample. The release paper of the measurement sample is peeled off to expose the corrosion-resistant layer, and with the corrosion-resistant layer in contact with the iron plate, the measurement sample is pressed from the base sheet side with a hand roller to adhere the measurement sample to the iron plate. An attachment with a plan view square shape of 4 cm vertically and 4 cm horizontally is fixed to the surface of the base sheet of the measurement sample using epoxy resin adhesive, and the measurement sample is cut along the contour of the attachment. The attachment is set in a tensile testing machine, and the attachment is pulled in the thickness direction of the measurement sample at a speed of 100 mm / min. The tensile load at the point when the measurement sample peels off the iron plate is recorded, and the adhesive strength of the measurement sample (unit: N / cm) is determined based on this. 2 The adhesive strength is calculated. A higher value indicates that the corrosion-resistant sheet has superior adhesion to the surface to be protected from corrosion.

[0043] <Method for evaluating corrosion protection performance> Four steel test pieces, each 2 cm long and 5 cm wide in plan view, are placed on the outer surface of a 20A polyvinyl chloride pipe (outer diameter 27.2 mm). A corrosion-resistant sheet is then wrapped around the entire outer surface of these four test pieces to form the test specimen. The corrosion-resistant sheet is wrapped so that the exposed corrosion-resistant layer, after removing the release paper, is in contact with the outer surface of the test pieces. The test specimen is placed in the chamber of a combined cycle testing machine, and a wet-dry cycle test is performed. This test conforms to JIS K 5600_7_9 :2006 The test will be conducted in accordance with (General Test Methods for Paints - Part 7 - Section 9 Cycle Corrosion Test Method - Salt Spray / Drying / Wetting), with three test durations: 2808 hours, 7000 hours, and 10000 hours. After the test duration, the corrosion-preventive sheet will be removed from the test specimen, and four test pieces will be collected. The thickness of each test piece will be measured, and the corrosion rate (unit: mm / y) will be calculated from the measured thickness and the test duration. The arithmetic mean of the corrosion rates of the four pieces will be taken as the corrosion rate of the corrosion-preventive sheet. A smaller corrosion rate indicates a higher evaluation of the corrosion-preventive sheet's performance.

[0044] [Table 1]

[0045] As shown in Table 1, the corrosion protection composition of Comparative Example 1 is a so-called modified asphalt containing SBS in addition to asphalt. Although it has superior corrosion protection performance compared to the corrosion protection composition of Comparative Example 2, which is ordinary asphalt without styrene-based resins such as SBS, it does not match the corrosion protection performance of the corrosion protection composition of Example 1, and the corrosion protection composition of Example 1 also had superior tensile strength and adhesive strength. The corrosion protection composition of Example 1 differs from the corrosion protection composition of Comparative Example 1, which does not contain an asphalt base material in which asphalt and SBS are integrated. Therefore, it can be seen that the asphalt base material is effective in improving the tensile strength, adhesive strength, and corrosion protection performance of the corrosion protection composition.

Claims

1. An asphalt base material containing asphalt and styrene resin, It comprises one or more modifiers selected from styrene-butadiene-styrene block copolymer and styrene-ethylene-butylene-styrene block copolymer, A corrosion-preventive composition having a penetration degree of 60 to 500 at a product temperature of 25 ± 0.1°C.

2. Furthermore, the corrosion-preventive composition according to claim 1 further comprises one or more tackifiers selected from aliphatic hydrocarbon resins.

3. Furthermore, the corrosion-preventive composition according to claim 1 or 2, further comprising calcium carbonate.

4. A corrosion-preventive composition according to claim 1 or 2, for use in preventing corrosion of structures in aquatic environments.

5. A method for producing the corrosion-preventive composition according to claim 1 or 2, A method for producing a corrosion-preventive composition, comprising the steps of mixing the asphalt base material and the modifier, and heating and stirring the mixture.

6. A corrosion-resistant sheet that is placed on the surface of an object to be protected from corrosion and has a corrosion-resistant layer that comes into contact with the surface of the object to be protected from corrosion during use, A corrosion-resistant sheet wherein the corrosion-resistant layer is made of the corrosion-resistant composition described in claim 1 or 2.

7. The corrosion-resistant sheet according to claim 6, comprising a non-adhesive base sheet, wherein the corrosion-resistant layer is provided on the surface of the base sheet.

8. A method for preventing corrosion of a steel structure, comprising the step of attaching the corrosion-preventive sheet described in claim 6 to the surface of the steel structure.

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