Antirust composition and antirust method

Abstract

To provide an antirust composition having a long-term antirust effect.SOLUTION: An antirust composition includes a microcapsule encapsulating a nitrite ion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rust-preventive composition. [Background technology]

[0002] In order to improve the durability of steel materials in a concrete structure (reinforced concrete structure, hereinafter also referred to as RC structure) when the steel materials are exposed to the atmosphere during construction and against deterioration or deformation after construction, it is preferable to apply anti-rust treatment to the steel materials embedded in the structure.

[0003] Patent Document 1 describes a rust inhibitor obtained by mixing a silicate liquid with zinc powder.

[0004] However, conventional rust inhibitors used for such steel materials cannot be expected to provide long-term rust prevention effects after construction, and therefore, there is a demand for rust inhibitors that can be expected to provide long-term rust prevention effects. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7284452 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above circumstances, an object of the present invention is to provide a rust-preventive composition having a long-term rust-preventive effect. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have found that by utilizing microcapsules impregnated with nitrite ions, it is possible to obtain a rust-preventive composition that exhibits long-term rust-preventive effects. Based on this finding, the present inventors have conducted further research and have completed the present invention.

[0008] That is, the present invention provides the following rust-preventive composition. Section 1. A rust-preventive composition comprising microcapsules encapsulating nitrite ions. Section 2. Item 1. The composition according to item 1, further comprising a binder component. Section 3. Item 3. The composition according to item 1 or 2, wherein silicon dioxide is contained in 100% by mass of the microcapsules. Section 4. Item 3. The composition according to Item 1 or 2, wherein the microcapsules are porous powders obtained by crushing pyroclastic flow deposits. Section 5. Item 1 or 2, the composition used for steel in concrete construction. Section 6. Item 7. A method for preventing rust on a steel material, comprising a step of coating the steel material with the rust-preventive composition according to Item 1 or 2. Item 7. The rust prevention method according to Item 6, wherein the steel material is a steel material for concrete structures. [Effects of the Invention]

[0009] The rust-preventive composition of the present invention thus obtained has a long-term rust-preventive effect. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a steel plate used for evaluation in each of Examples and Comparative Examples. FIG. [Figure 2] Photograph showing outdoor exposure test. [Figure 3] A photograph showing outdoor exposure testing of the steel bars used in the pull-out test. [Figure 4] FIG. 1 is a schematic diagram showing an embodiment of a pull-out test. [Figure 5] Rust inhibitor adhesion performance evaluation test results. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, the term "containing" is a concept that encompasses all of "comprise," "consist essentially of," and "consist only of." Furthermore, in this specification, when a numerical range is expressed as "A to B," it means A or more and B or less.

[0012] The rust-preventive composition of the present invention contains microcapsules encapsulating nitrite ions.

[0013] As the nitrite salt from which the nitrite ion is derived, a wide variety of known nitrite salts can be used, and there are no particular limitations. Specific examples include lithium nitrite, calcium nitrite, sodium nitrite, and potassium nitrite. Among these, it is preferable to use lithium nitrite or calcium nitrite, and it is particularly preferable to use lithium nitrite because it can provide a longer-lasting rust-preventing effect.

[0014] As the microcapsules, a wide variety of known microcapsules can be used without any particular limitation. Among them, microcapsules containing 50% by mass or more of silicon dioxide are preferred, and microcapsules containing 65% by mass or more of silicon dioxide are more preferred.

[0015] Specific examples of the microcapsules described above include porous powders obtained by crushing pyroclastic flow deposits composed of pumice, volcanic ash, and the like. Pyroclastic flow deposits have a porous shape and are primarily composed of silicon dioxide, but also contain aluminum oxide and the like, and are suitable for use as the microcapsules used in the present invention. The composition of the constituent components of pyroclastic flow deposits varies depending on the place of origin, but regardless of the place of origin, they contain 65% by mass or more of silicon dioxide as the primary component.

[0016] The particle size of the microcapsules is not particularly limited. Specifically, the average particle size is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. The average particle size is preferably 1000 μm or less, more preferably 300 μm or less, and even more preferably 150 μm or less.

[0017] It is preferable to use microcapsules having a porous shape, such as those made of porous powder obtained by crushing pyroclastic flow deposits.

[0018] The particle density of the microcapsules is 2.0 to 2.8 g / cm 3 It is preferable to set the following.

[0019] The larger the porosity of the microcapsules, the more nitrite ions they can contain, improving their performance as capsules. There are no particular limitations on the porosity. For example, It is preferably up to 60%, and more preferably 30 to 60%.

[0020] The amount of nitrite ions to be encapsulated in the microcapsules is preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of microcapsules. The amount of nitrite ions to be encapsulated in the microcapsules is preferably 16 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of microcapsules. By encapsulating the amount of nitrite ions in an amount of 2 parts by mass or more per 100 parts by mass of microcapsules, excellent rust-preventing effects can be expected. On the other hand, by encapsulating the amount of nitrite ions in an amount of 16 parts by mass or less per 100 parts by mass of microcapsules, the microcapsules are less likely to solidify, improving the stability of the rust-preventive composition.

[0021] Furthermore, even when porous powder obtained by crushing pyroclastic flow deposits is used as the microcapsules, it is preferable that the amount of the porous powder used be as described above.

[0022] The method for encapsulating nitrite ions in microcapsules can be a wide variety of known methods and is not particularly limited. For example, a method can be used in which microcapsules are impregnated with the above-described aqueous nitrite solution and then dried. An example of an embodiment is where the resulting microcapsules encapsulating nitrite are added to a composition containing a binder component, etc., as described below, whereby the nitrite becomes ionic, thereby forming microcapsules encapsulating nitrite ions. Here, in order to encapsulate an aqueous lithium nitrite solution with as high a concentration as possible, it is desirable for the microcapsules to be as dry as possible (air-dried).

[0023] The rust-preventive composition of the present invention preferably further contains a binder component. Both water-soluble binder resins and oil-soluble binder resins can be used as the binder component. However, taking into consideration the effects on the human body and the environment in the working environment, it is preferable to use a water-soluble binder resin.

[0024] As such a water-soluble binder resin or an oil-soluble binder resin, a wide variety of known binder resins can be used without any particular limitation.

[0025] Specific examples of the water-soluble binder resin include alkyd resin, vinyl resin, acrylic resin, melamine resin, epoxy resin, epoxy ester resin, polyester resin, and urethane resin.

[0026] Examples of oil-soluble binder resins include alkyd resins, phthalic acid resins, amino resins, vinyl resins, acrylic resins, melamine resins, epoxy resins, polyamide resins, polyester resins, polyurethane resins, phenolic resins, silicone resins, silicon resins, and fluororesins.

[0027] Among the above, it is preferable to use epoxy resin or epoxy ester resin as the binder component because they have excellent water resistance and weather resistance and have high adhesion to steel materials.

[0028] The amount of binder component used, where M is the dry mass of the microcapsules and B is the mass of the binder component, is preferably M / B 0.01 or more, more preferably 0.05 or more, even more preferably 0.10 or more, and particularly preferably 0.11 or more. Furthermore, M / B is preferably 1.00 or less, more preferably 0.50 or less, even more preferably 0.30 or less, and particularly preferably 0.25. By having M / B 0.11 or more, a rust-preventive coating of 100 μm or more can be obtained, and long-term rust-preventive effects can be obtained. On the other hand, by having M / B 0.25 or less, excellent workability can be achieved, allowing for uniform application to steel materials without unevenness.

[0029] In addition, the rust-preventive composition of the present invention may contain pigments such as color pigments, rust-preventive pigments, and extender pigments; thixotropic agents such as anti-settling agents, anti-sagging agents, and thickeners; dispersants such as wetting / dispersing agents and anti-color separation agents; and surface conditioners such as leveling agents and anti-foaming agents, within the scope of not impairing the effects and objects of the present invention.

[0030] The present invention includes an invention relating to a method for rust prevention of steel materials. There are no particular limitations on the steel materials to be rust-prevented, and a wide range of steel materials used in various architectural structures can be exemplified. Specifically, steel materials used in concrete structures can be exemplified.

[0031] The method for coating the rust-preventive composition of the present invention on a steel material can be a wide variety of known methods, and is not particularly limited. Specific examples include coating and spraying.

[0032] Although the embodiments of the present invention have been described above, the present invention is not limited to these examples, and it goes without saying that the present invention can be embodied in various forms without departing from the spirit of the present invention. [Example]

[0033] Hereinafter, the embodiments of the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0034] Rust-preventive compositions were prepared using a one-component epoxy resin with the formulations shown in Tables 1 and 2 below, a 40% by mass aqueous solution of lithium nitrite, and porous powder obtained by crushing pyroclastic flow deposits. The particle size of the porous powder obtained by crushing pyroclastic flow deposits was 300 μm. The crushed porous powder was impregnated with a 40% by mass aqueous solution of lithium nitrite and dried, and then added to the epoxy resin and mixed to obtain a uniform mixture, thereby obtaining rust-preventive compositions for each of the Examples and Comparative Examples.

[0035] Each composition of the examples and comparative examples was applied with a brush to a degreased steel plate measuring 200 mm x 300 mm x 3 mm. The application was carried out in an environment of 22±0.5°C and a humidity of 70±5%, and the plate was allowed to dry for 7 days. After drying, a cutter scratch (hereinafter also referred to as "the scratch") 100 mm long and 1 mm wide was made on the steel plate at a position 75 mm from the bottom, as shown in Figure 1.

[0036] (Outdoor exposure test) An exposure test to a salt damage environment was carried out by placing the steel sheets coated with the compositions of the examples and comparative examples obtained above in the marine atmosphere at an ocean exposure site (Taniyama Port, Kagoshima City), which is a salt damage environment, tilted at 45 degrees facing the sea (eastward), as shown in Figure 2. Evaluation of rust prevention performance was carried out 1 month, 8 months, and 24 months after the start of exposure.

[0037] <Evaluation item: Workability (mixability)> When the rust-preventive composition was prepared, it was examined whether the microcapsules aggregated. After the composition was prepared, if no aggregation was observed, it was judged as passing (indicated as ◯ in the table).

[0038] <Evaluation item: Workability (applicability)> When the rust-preventive composition was applied to the steel plate and the steel bar for reinforced concrete, those that could be uniformly applied were judged to be acceptable (marked as "good" in the table).

[0039] <Evaluation item: Rust prevention (appearance)> Steel plates with no visible rust (indicated as "no rust spots" in the table) or with only slight visible rust (indicated as "small rust", "small rust spots", or "medium rust spots" in the table) were rated as passing. Steel plates with visible rust around the periphery or over the entire surface (indicated as "large rust" or "large rust spots" in the table) were rated as failing.

[0040] <Evaluation item: Rust prevention (corrosion rate)> A laser microscope was used to analyze the depth of corrosion in the rust at the scratches, and a corrosion rate of less than 0.1 mm / y was considered to be acceptable.

[0041] <Evaluation item: Adhesion (steel)> The pull-off method of JIS K 5600-5-7 was carried out to evaluate the adhesive strength of the rust-preventive composition to the steel plate. A test cylinder was attached to the surface of the rust-preventive composition, and a tensile test was carried out using a tensile tester. The value obtained was 1 N / mm 2 In the above cases, sufficient adhesive strength was recognized and the composition was deemed to have passed. Furthermore, if the test results based on the pull-off method showed that the coating formed by the rust-preventive composition underwent cohesive failure (indicated as "cohesive" in the table), the composition was deemed to have passed because it had sufficient adhesive strength to the steel plate.

[0042] [Table 1]

[0043] [Table 2]

[0044] As shown in Tables 1 and 2, it was confirmed that the rust-preventive compositions of the Examples had superior rust-preventive performance compared to the rust-preventive compositions of the Comparative Examples.

[0045] (Anti-rust agent adhesion performance evaluation test and pull-out test) Using the rust inhibitors of Examples 6, 8, and 9 and Comparative Example 3, an adhesion performance evaluation test for steel bars for reinforced concrete (hereinafter also simply referred to as "steel bars") was conducted in accordance with JSCE-G-503, and the adhesive strength with concrete was evaluated. The rust inhibitor was applied to the ends of six steel bars with a brush, and they were dried for seven days in an environment of room temperature 20±1°C and humidity 50±5%. Next, the steel bars coated with the rust inhibitor were placed horizontally in a formwork, and concrete was poured into them to prepare three specimens for each. The tensile and compressive strength of the concrete was 30 N / mm 2 After confirming that the bar had reached this level, a pull-out test was conducted on the steel bars from the concrete, and the bond stress-slip curve, calculated as the average value for the three specimens, is shown in Figure 5. The remaining three specimens, with rust inhibitors applied to the ends, were left in the marine air at a marine exposure site (Taniyama Port, Kagoshima City), which is a salt damage environment, and an exposure test to the salt damage environment was conducted for six months. Next, the steel bars coated with rust inhibitor were placed horizontally within a formwork, and a concrete pull-out test was conducted in the same way. The exposure test to the salt damage environment is shown in Figure 3, and the specimens for the concrete pull-out test are shown in Figure 4.

[0046] <Evaluation item: Adhesion to concrete> When the bond stress-slip curve of each specimen was drawn based on JSCE-G-503, the bond stress when the slip amount reached 0.002Dmm (D is the nominal diameter of the steel) was 1.7N / mm 2 In addition, the bond stress when the slippage reached 0.5 mm was 7 N / mm 2 Based on the above, it was determined that the material had sufficient adhesion to concrete.

Claims

1. A rust-preventive composition comprising microcapsules encapsulating nitrite ions.

2. The composition of claim 1 further comprising a binder component.

3. The composition according to claim 1 or 2, wherein silicon dioxide is contained in an amount of 50% by mass or more in 100% by mass of the microcapsules.

4. 3. The composition according to claim 1, wherein the microcapsules are porous powders obtained by crushing pyroclastic flow deposits.

5. 3. The composition of claim 1 or 2 used for steel in concrete construction.

6. A method for preventing rust on a steel material, comprising the step of coating the steel material with the rust-preventive composition according to claim 1 or 2.

7. The method for preventing rust according to claim 6, wherein the steel material is a steel material for concrete construction.

Images