JP2012144772A - Rust-diverting agent-containing urethane foam and method for preventing rust for hollow steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing rust, in which a rust prevention operation to the inside face of a hollow steel can be easily performed, and which can obtain a rust prevention effect for a long period.SOLUTION: A hole 13 is formed at the side face of a hollow steel 11 in which red rust 15 has been generated, an urethane raw material 21 containing a rust-diverting agent is injected into the hollow steel 11 from the hole 13, the urethane raw material 21 is foamed at the inside of the hollow steel 11, thus the air in the hollow steel 11 is driven out to fill rust-diverting agent-containing urethane foam 25 into the hollow steel 11, further, the rust-diverting agent-containing urethane foam 25 is stuck and adhere to the inside face of the hollow steel 11, and thereafter, the hole 13 at the side face of the hollow steel 11 is closed with a closing member 31.

Description

  The present invention relates to a rust conversion agent-containing urethane foam and a rust prevention method for a hollow steel material using the same.

  As shown in (3A) of FIG. 3, when red rust 55 is generated on the inner surface of the hollow steel material 51 used for the main structure of the bridge, as shown in (3B) and (3C), Using the holes 53 formed on the side surface, the red rust 55 on the inner surface of the steel material is dropped with shot blasting, keren, metal brush, etc. A film 57 is formed, and then the hole 53 is welded and closed with an iron plate 59 as in (3E).

  However, since the working holes 53 formed in the hollow steel material 51 are preferably small in terms of strength and the like of the hollow steel material 51 and the number thereof is small, the holes 53 formed in the hollow steel material 51 are used to form the inside of the hollow steel material 51. When working to remove red rust, there are places where red rust cannot be removed due to the rust removal equipment not being delivered. Furthermore, it is difficult to evenly and uniformly coat the inner surface of the hollow steel material 51 using the holes 53 formed in the hollow steel material 51, and a sufficient rust prevention effect may not be obtained.

  In addition, as a method of rehabilitating pipes that have been buried in the ground and have deteriorated, the tubes are inserted inside the pipes while being inverted, and the tubes are fixed to the pipe inner faces by interposing a resin between the pipe inner faces and the tubes. There is an in-pipe lining method (Patent Document 1).

  However, when the pipe lining method is applied to a hollow steel material other than a cylindrical shape, for example, a rectangular hollow steel material, a gap is easily generated between the inner surface of the steel material and the tube at the corner portion, and the rust prevention effect is reduced. There is a fear.

Also, a repair method has been proposed in which after the red rust on the inner surface of the hollow steel material is removed, urethane foam is foamed in the hollow steel material and the hollow foam is filled with the urethane foam (Patent Document 2).
The rust prevention method of filling urethane foam can prevent rust effect because it can block the air and water from the outside of the hollow steel material with urethane foam, but the hollow steel material is the same as when applying rust prevention coating or plating etc. There is a place where the red rust cannot be removed due to the rust removal equipment not reaching because the work to remove the red rust in the hollow steel material is made using the holes formed in the.

Further, a method has been proposed in which a metal resin composition containing a metal rust inhibitor in a thermoplastic resin is diluted with a solvent or the like and applied to a metal product by spraying or the like (see paragraph 0042 of Patent Document 3).
However, when the application of the metal resin composition is applied to rust prevention of the inner surface of the hollow steel material, the metal resin composition is applied to the inner surface of the hollow steel material by spraying or the like using the holes formed in the hollow steel material. Therefore, due to the same problem as when applying rust-proof coating or plating, that is, due to restrictions on the size and number of work holes formed in the hollow steel, There are places where it cannot be dropped, and it is difficult to uniformly and uniformly apply the metal resin composition to the inner surface of the hollow steel material, and there is a problem that a sufficient rust prevention effect cannot be obtained.

In addition, as a method for repairing steel materials, methods have been proposed in which a rust-preventive paint containing a rust-converting rust inhibitor is applied to steel materials (Patent Documents 4 and 5). The rust conversion type rust inhibitor has the effect of converting red rust (iron sesquioxide, hematite) into dense, rust-proof stable black rust (iron trioxide, magnetite). Effective in suppressing progress.
However, when applying anti-rust paint containing a rust conversion type rust preventive agent to rust prevention on the inner surface of a hollow steel material, a rust preventive paint containing a rust conversion type rust preventive agent using holes formed in the hollow steel material Will be painted on the inner surface of the hollow steel material by spraying, etc., so from the same problem as when applying the antirust coating or plating, that is, from the restrictions on the size and number of holes for work to be formed in the hollow steel material, There is a problem that a coating tool cannot reach, there are places where coating cannot be performed, or uniform coating cannot be performed, and a sufficient rust prevention effect cannot be obtained.

JP 2001-4090 A JP 2010-48000 A JP 2009-102692 A JP 2000-140746 A JP 2009-40929 A

  The present invention has been made in view of the above points, and can easily and uniformly perform a rust-converting agent-containing urethane foam having a rust-preventing effect on the steel material surface and the inner surface of the hollow steel material. It aims at providing the rust prevention method of the hollow steel material from which the rust prevention effect is acquired.

  The invention according to claim 1 is a urethane foam obtained by mixing and foaming a resin raw material containing polyols, a catalyst, a foam stabilizer, and a foaming agent and an isocyanate raw material containing polyisocyanate, and at least the resin raw material is provided with a rust conversion agent. The present invention relates to a rust conversion agent-containing urethane foam characterized by being mixed.

  The invention of claim 2 includes a rust conversion agent containing a polyol, a catalyst, a foam stabilizer, a foaming agent, a rust conversion agent and an isocyanate raw material in the method for rust-proofing the inner surface of the hollow steel material. A urethane raw material is injected into the hollow steel material from the hole, and the rust conversion agent-containing urethane foam is filled into the hollow steel material by foaming the rust conversion agent-containing urethane raw material, and then the hole is closed. The present invention relates to a rust prevention method for a hollow steel material.

  According to the first aspect of the present invention, if the urethane foam containing rust conversion agent is filled in a place where the steel material exists in the back of the gap such as concrete, rock, gravel, etc., the urethane foam containing the rust conversion agent adheres to the steel material. Even if it is not, the gap can be sealed with urethane foam, and the rust conversion agent contained in the urethane foam containing rust conversion agent vaporizes, converting the red rust generated on the steel surface to black rust. The progress of rust (occurrence and erosion of red rust) can be suppressed, and an antirust effect can be obtained without removing red rust on the surface of the steel material.

  According to the invention of claim 2, when the rust conversion agent-containing urethane raw material injected into the hollow steel material is foamed in the hollow steel material to become a rust conversion agent-containing urethane foam and filled into the hollow steel material, The air in the steel material is driven out of the hollow steel material by the urethane foam containing rust conversion agent, and the urethane foam containing the rust conversion agent adheres and adheres to the inner surface of the hollow steel material, so that air and water are insulated from the inner surface of the steel material. And an antirust effect can be obtained. Furthermore, the rust conversion agent contained in the rust conversion agent-containing urethane foam filled in the hollow steel material converts the red rust generated on the inner surface of the hollow steel material to black rust, and the progress of rust (occurrence and erosion of red rust). Can be suppressed. Moreover, the rust conversion agent-containing urethane raw material is injected into the hollow steel material without removing the red rust on the inner surface of the hollow steel material, and the rust conversion agent-containing urethane foam is foamed, so that the rust prevention treatment in the hollow steel material can be performed. Therefore, it is possible to easily perform the rust prevention work of the hollow steel material.

  Further, according to the invention of claim 2, in order to fill the hollow steel material with the rust converting agent-containing urethane foam by injecting the urethane raw material containing the rust converting agent into the hollow steel material and causing the foamed foam in the hollow steel material, However, regardless of the shape of the hollow steel material, the rust conversion agent-containing urethane foam can be filled into the hollow steel material, and a good rust prevention effect can be obtained. Furthermore, the coating unevenness and the unpainted portion that are likely to occur when the rust preventive paint is applied are not generated in the rust preventive method of the present invention, and a good rust preventive effect is obtained. Moreover, since the operation | work for red rust removal is unnecessary, the work hole formed in a hollow steel material is a small thing which can inject | pour a rust conversion agent containing urethane raw material, and can shorten a construction period.

  Moreover, since the rust conversion agent is vaporizable and vaporization is promoted by the reaction heat at the time of urethane foaming, when filling the rust conversion agent-containing urethane foam, the inner surface of the hollow steel material and the rust conversion agent-containing urethane foam Even if voids are generated between the two, the vaporized rust conversion agent adheres to the inner surface of the steel material in the voids and converts red rust to black rust, thereby suppressing the progress of rust. In addition, even after foaming of the rust converting agent-containing urethane foam, the rust converting agent in the rust converting agent-containing urethane foam is vaporized, so that the red rust of the steel material can be converted to black rust and the progress of rust can be suppressed.

Furthermore, because the urethane foam containing rust conversion agent is filled in the closed space in the hollow steel material where the working holes are blocked, the vaporizable rust conversion agent in the urethane foam containing rust conversion agent is semi-permanently rusted. Preventive effect lasts.
In addition, even when a hole is created in the hollow steel material after filling the rust conversion agent-containing urethane foam, the rust conversion factor enters the hollow steel material from the outside due to the rust conversion agent-containing urethane foam filled in the hollow steel material. Can be prevented.
By these, according to the rust prevention method of this invention, generation | occurrence | production and progress of red rust can be suppressed in the long term compared with the conventional method.

It is a schematic process drawing of one Embodiment in the rust prevention method of the hollow steel material of this invention. It is a figure which shows the confirmation experiment method of a rust prevention effect. It is a schematic process diagram in the conventional rust prevention method.

Hereinafter, an embodiment of the rust conversion agent-containing urethane foam of the present invention and a rust prevention method for a hollow steel material using the same will be described.
Rust conversion agent-containing urethane foam is a urethane foam obtained by mixing and foaming a resin raw material containing polyols, a catalyst, a foam stabilizer, and a foaming agent and an isocyanate raw material containing polyisocyanate, and at least the resin raw material has a rust conversion agent. It is made of mixed.

  For example, when the rust conversion agent-containing urethane foam in the present invention has a hole in the hollow steel material after completion of the rust prevention work of the hollow steel material described below, the rust conversion agent does not volatilize in a short period of time through the hole in the hollow steel material. In order to obtain a good rust-preventing effect over the entire range, in the air permeability measurement of JIS K 6400-7, a material having almost no air permeability that is equal to or lower than the measurement lower limit is preferable. In addition, since it is preferable that the vaporizable rust conversion agent can move slowly in the rust conversion agent-containing urethane foam filled in the hollow steel material etc., the proper range of closed cell ratio in the rust conversion agent-containing urethane foam is rust conversion agent 30% to 90% (JIS K 7138) is preferable on the average in the containing urethane foam.

  As the polyols, known polyols for urethane foam are used, which may be either ether type or ester type. More preferably, a polyol for rigid urethane foam is preferred. The polyol is not limited to one type, and a plurality of types may be used in combination. In particular, as described above, urethane foam having almost no air permeability and having a closed cell ratio of 30% to 90% is preferable.

As the catalyst, an amine catalyst for urethane foam and a metal catalyst (organometallic compound catalyst) are used alone or in combination. Examples of the amine-based catalyst include a monoamine compound, a diamine compound, a triamine compound, a polyamine compound, a cyclic amine compound, an alcohol amine compound, an ether amine compound, and the like. One kind of these may be used, or two or more kinds may be used in combination. Examples of the metal catalyst include an organic tin compound, an organic bismuth compound, an organic lead compound, an organic zinc compound, and the like. One kind of these may be used, or two or more kinds may be used. The amount of the catalyst is generally 0.05 to 10 parts by mass per 100 parts by mass of the polyol.
As the foam stabilizer, a silicone compound, a cation system, an anion system, a nonionic surfactant or the like can be used.

  Examples of the foaming agent include water, hydrocarbons, halogen compounds, and the like. One of these may be used, or two or more may be used. The amount of the blowing agent is generally 1 to 70 parts by mass per 100 parts by mass of the polyol.

  Examples of the rust converting agent include phosphates, phosphites, chelating agents, fluorine compounds, polyphenol derivatives, metal sulfides and the like. As phosphate, orthophosphoric acid, sodium phosphate, calcium phosphate, zinc phosphate, nickel phosphate, polymerized phosphoric acid, etc., as phosphite, calcium phosphite, magnesium phosphite, etc., as chelating agent, Citric acid, tartaric acid, ethylenediaminetetraacetic acid, tannic acid, phytic acid, etc., as fluorine compounds, hydrofluoric acid, sodium fluoride, silicic acid, potassium silicofluoride, etc., polyphenol derivatives as tannic acid, gallic acid, protocatechu An acid, pyrogallol, etc. can be mentioned. The rust conversion agent is preferably volatile as a single substance or diluted with a volatile solvent or the like. One or more types are selected from the rust conversion agent. The rust conversion agent is preferably added to the resin raw material side including polyols, a catalyst, a foam stabilizer, and a foaming agent, but may be added separately to both the resin raw material side and the isocyanate raw material side. The amount of the rust conversion agent is preferably in a range that does not affect the physical properties and mechanical properties of the urethane foam. As an example, 1-100 mass parts with respect to 100 mass parts of polyol of the said rust conversion agent containing urethane raw material, More preferably, 20-80 mass parts is mentioned. If the content is small, the rust prevention performance (rust conversion effect and red rust generation prevention effect) is lowered, and if the content is increased, the rust prevention effect is obtained but the economy is inferior. In this way, general-purpose rust conversion agents can be used. However, if there is an influence on the urethane resination reaction or foaming reaction, and the physical or mechanical properties after foaming, polyols, isocyanate raw materials, foaming agents, regulating agents Each reaction and each characteristic after foaming can be adjusted by increasing / decreasing the amount of each raw material such as a foaming agent and a catalyst.

  As the isocyanate raw material, a known polyisocyanate for urethane foam is used. The polyisocyanate is not particularly limited as long as it is a compound having two or more isocyanate groups, and those used for urethane foam can be used. One type can be used alone or two or more types can be used in combination. Good. Examples of the polyisocyanate include aromatic, aliphatic, and alicyclic isocyanate compounds, and modified products thereof. The polyisocyanate content is preferably adjusted so that the isocyanate index is 90 to 130. Isocyanate index is an index used in the field of polyurethane, and is a polyisocyanate for active hydrogen groups in raw materials (for example, active hydrogen groups contained in hydroxyl groups of polyols and water as a blowing agent). It is the numerical value which represented the equivalent ratio of the isocyanate group of a kind with a percentage.

  Rust conversion agent-containing urethane raw materials including polyols, catalysts, foam stabilizers, foaming agents, rust conversion agents and isocyanate raw materials are mixed with a known raw material supply device (also referred to as an injection device), and steel materials are present. By being injected into the space or the hollow steel material, it reacts and foams to form a rust conversion agent-containing urethane foam, and is filled into the space or the hollow steel material. In addition, the rust conversion agent containing urethane raw material in a raw material supply apparatus accommodates a resin raw material and an isocyanate raw material separately, and is mixed at the time of discharge.

The rust prevention method of the hollow steel material of the present invention is a rust prevention method when rust (red rust) is generated on the inner surface of a hollow steel material used for a main structure of a bridge, and includes a hole forming step, a urethane filling step, a hole It consists of a closing process.
In the hole forming step, work holes 13 are formed in the side surface 12 of the hollow steel material 11 as shown in FIGS. 1A and 1B. Since the work of removing the red rust 15 on the inner surface of the hollow steel material 11 is unnecessary, the size of the hole 13 may be a size that can insert an injection gun nozzle of a rust conversion agent-containing urethane raw material, and has a diameter of about 2 to 5 cm. That's fine. The position of the hole 13 is preferably a high position. For example, the position 50 cm or more from the lower end of the hollow steel material 11 is mentioned. The number of holes 13 may be plural. The hole 13 can be formed by a known method such as a drill.

  In the urethane filling step, as shown in (1C) of FIG. 1, a rust conversion agent-containing urethane raw material 21 is injected into the hollow steel material 11 from the working hole 13 and foamed and hardened to (1D) of FIG. As shown, the hollow steel material 11 is filled with a rust conversion agent-containing urethane foam 25. Injection of the rust conversion agent-containing urethane raw material 21 into the hollow steel material 11 is performed by inserting an injection gun nozzle 41 of a known urethane raw material supply device into the hollow steel material 11 from the hole 13 on the side surface of the hollow steel material 11. At the time of foaming of the rust conversion agent-containing urethane raw material 21, the rust conversion agent-containing urethane foam 25 formed by the foaming is filled in the hollow steel material 11 while expelling air in the hollow steel material 11, and rust conversion is performed on the inner surface of the hollow steel material 11. The agent-containing urethane foam 25 adheres and adheres. In addition, the injection amount of the rust conversion agent-containing urethane raw material 21 into the hollow steel material 11 is such that the rust conversion agent-containing urethane foam 25 formed by foaming from the rust conversion agent-containing urethane raw material 21 is formed in the hollow steel material 11 without a gap. This is the amount. The rust conversion agent-containing urethane raw material 21 includes the polyols, the catalyst, the foam stabilizer, the foaming agent, the rust conversion agent, the isocyanate raw material, and other additives that are appropriately blended.

  In the hole closing step, as shown in FIG. 1 (1E), the hole 13 formed on the side surface of the hollow steel material 11 is closed with a closing member 31 such as a bolt or a metal plate. In the case of a bolt, it is fixed by screwing into the hole 13, and in the case of a metal plate, it is fixed by welding or the like. By completing this hole closing step, the rust prevention work of the hollow steel material 11 is completed.

  The hollow steel material 11 after the rust prevention work is bonded to the inner surface of the hollow steel material 11 by the air inside the hollow steel material 11 being driven out of the hollow steel material 25 by the urethane foam 25 containing the rust conversion agent. Therefore, air and water can be insulated from the inner surface of the hollow steel material 11, and the generation and progression of rust can be prevented. Further, even when a hole is formed in the hollow steel material 11, the rust conversion agent-containing urethane foam 25 filled in the hollow steel material 11 can prevent the rusting factor from entering the hollow steel material 11 from the outside. it can. Further, the rust conversion agent contained in the rust conversion agent-containing urethane foam 25 filled in the hollow steel material 11 converts the red rust 15 on the inner surface of the hollow steel material 11 into rust-proof black rust and suppresses the progress of rust. be able to.

The antirust effect by the rust conversion agent containing urethane foam formed by the antirust method of the hollow steel material of the present invention was confirmed by the following method.
As shown in (2-1) of FIG. 2, two 1 × 4 cm iron plates with red rust generated on the surface, one sheet (A) is 15 cm from the bottom of the container whose bottom is 10 cm in diameter and 20 cm in height. The other sheet (B) was hung so that the lower end of the iron plate was at a position 2 cm from the bottom of the container. Five sets of the containers in which the iron plates (A) and (B) were suspended were easily used for Experimental Examples 1 to 5.

  Next, from the following raw materials, the urethane raw material prepared by the blending of Experimental Examples 1 to 5 shown in Table 1 was filled in 80 ml of the container to form a urethane foam, which is shown in (2-2) of FIG. Thus, the lower iron plate (B) was buried in the urethane foam, and the upper iron plate (A) was positioned in the air above the urethane foam.

Polyether polyol # 5000: polyether polyol obtained by addition reaction of propylene oxide and ethylene oxide to glycerin, functional group number 3, hydroxyl value 33 (mgKOH / g), molecular weight 5000
-Polyether polyol: polyether polyol obtained by addition reaction of propylene oxide and ethylene oxide with glycerin, functional group number 3, hydroxyl value 250 (mgKOH / g), molecular weight 670
・ Phthalic acid glycol ester: Polyester polyol obtained by adding diethylene glycol to phthalic anhydride, functional group number 2, hydroxyl value 260 (mgKOH / g), molecular weight 430
EDP300: polyol obtained by adding propylene oxide to ethylenediamine, number of functional groups 4, hydroxyl value 740 (mgKOH / g), molecular weight 300, manufactured by Asahi Denka Kogyo Co., Ltd. Polymeric MDI: polyphenylpolymethylene polyisocyanate 70% by mass, diphenylmethane Compound of 30% by weight of diisocyanate ・ KAO-25 (catalyst): N, N-dimethylaminohexanol, manufactured by Kao Corporation ・ Foam stabilizer: polyoxyalkylene, dimethylpolysiloxane, solid urethane foam Foaming agent, manufactured by Toray Dow Corning (product number: SZ1949)
・ Rust conversion agent: Vaporizable rust conversion agent consisting mainly of barium sulfide mixture (metal sulfide: reducing agent) and aromatic oxime (rust inhibitor)

After leaving the container covered for one week, the urethane foam with the iron plate (B) buried in it and the iron plate in the air (A) are taken out of the container, and the urethane foam is further broken into the iron plate (B). Was taken out.
・ Visual test The surface color of the iron plates (A) and (B) taken out is visually observed. If the color is clearly changed to black (black rust), ◎, if the color is slightly changed to black (black rust). ○, when there was no change from brown (red rust), it was marked as x. The results are shown in Table 2.

  In Experimental Example 1 (comparative example) that does not contain a rust conversion agent, neither the iron plate (A) in the air nor the iron plate (B) in the urethane remained red rust (x) without being black rusted. On the other hand, in Experimental Example 2 (Example) containing 20 parts by mass of a rust conversion agent, the iron plate (A) in the air did not become black rust and remained red rust (x), but the iron plate (B) in urethane. About, it became black rust slightly ((circle)). In Experimental Example 3 (Example) containing 40 parts by mass of a rust conversion agent, the steel plate (A) in the air was slightly black rusted (◯), and the iron plate (B) in the urethane was clearly black rusted. (◎). In Experimental Example 4 (Example) containing 60 parts by mass of the rust converting agent and Experimental Example 5 (Example) containing 80 parts by mass, both the air iron plate (A) and the iron plate (B) in urethane are clearly black. Rusted (◎).

-Magnetic test Next, the deposits on the surfaces of the iron plates (A) and (B) after visual observation were scraped with a cutter knife and collected. A magnet was brought close to the collected deposits to examine the degree of magnetism of the deposits. It is known that black rust has magnetism enough to be attracted to the magnet, and red rust has no magnetism enough to attract the magnet. ◎ when there was apparent magnetism, ◯ when there was some magnetism, and x when there was no magnetism. The results are shown in Table 3.

  In Experimental Example 1 (Comparative Example) that does not contain a rust conversion agent, neither the iron plate (A) in the air nor the iron plate (B) in the urethane had no magnetism (x) and remained red rust. On the other hand, in Experimental Example 2 (Example) containing 20 parts by mass of a rust conversion agent, the iron plate (A) in the air had no magnetism (x) and remained red rust, but the iron plate (B) in the urethane remained. Slightly magnetic (O) slightly black rusted. Further, in Experimental Example 3 (Example) containing 40 parts by mass of the rust converting agent, both the iron plate (A) in the air and the iron plate (B) in the urethane are slightly magnetic (O) and slightly black rusted. . In Experimental Example 4 (Example) containing 60 parts by mass of the rust conversion agent and Experimental Example 5 (Example) containing 80 parts by mass, both the iron plate (A) in the air and the iron plate (B) in the urethane are clearly magnetic. (◎) and black rusted.

・ Immersion test The iron plates (A) and (B) after the magnetic test were completely immersed in water and allowed to stand at 30 ° C. for 24 hours, and then it was visually confirmed whether red rust was generated on the surface of the iron plate. ◎ when there was no new red rust, ○ when new red rust was slightly generated, and x when new red rust was clearly generated. Table 4 shows the test results.

  In Experimental Example 1 (comparative example) not containing a rust conversion agent, new red rust was clearly generated (×) in both the air iron plate (A) and the iron plate (B) in urethane. In Experimental Example 2 (Example) containing 20 parts by mass of a rust conversion agent, new red rust was clearly generated (×) in both the air iron plate (A) and the iron plate (B) in urethane. On the other hand, in Experimental Example 3 (Example) containing 40 parts by mass of a rust conversion agent, new red rust was clearly generated for the iron plate (A) in the air (×), and new for the iron plate (B) in urethane. A slight amount of red rust occurred (◯). In Experimental Example 4 (Example) containing 60 parts by mass of a rust conversion agent, a slight amount of new red rust was generated for the iron plate (A) in the air (O), and a new red rust was generated for the iron plate (B) in the urethane. It did not occur (◎). In Experimental Example 5 (Example) containing 80 parts by mass of the rust conversion agent, no new red rust was generated on the iron plate (A) in the air and the iron plate (B) in the urethane (◎).

  From these experimental examples, in the case of urethane foam that does not contain a rust conversion agent, the effect of converting red rust on the iron plate surface to black rust cannot be obtained, but in the case of urethane foam that contains a rust conversion agent, red rust on the iron plate surface. It turns out that the progress of rust can be suppressed by converting to black rust. Especially when foaming urethane foam containing a rust conversion agent, when the iron plate is buried in the urethane foam, the red rust on the surface of the iron plate should be converted to black rust even if the content of the rust conversion agent is 20 parts by mass. Can do. Furthermore, when the content of the rust conversion agent is 40 parts by mass or more, not only the iron plate embedded in the urethane foam when foaming the urethane foam containing the rust conversion agent, but also the urethane foam outside without being embedded in the urethane foam. The steel plate located in the air can also convert the red rust on the surface to black rust. From this, it can be seen that the rust conversion agent vaporized at the time of foaming of the urethane foam can convert the red rust on the surface of the iron plate not in contact with the urethane foam to black rust and suppress the occurrence of red rust. Moreover, when the content of the rust conversion agent is 60 parts by mass or more, not only the iron plate embedded in the urethane foam at the time of foaming of the urethane foam containing the rust conversion agent, but also the urethane foam outside without being embedded in the urethane foam. It can be seen that the occurrence of red rust can be suppressed even if the steel plate located in the air is immersed in water afterwards.

  Therefore, the inner surface of the hollow steel material is injected by injecting a rust conversion agent-containing urethane raw material containing a rust conversion agent into the hollow steel material having red rust on the inner surface, and foaming the rust conversion agent-containing urethane foam in the hollow steel material. The red rust can be converted to black rust and the occurrence of red rust can be suppressed. Furthermore, even when voids are formed in the hollow steel material when filling the urethane foam containing the rust conversion agent, the vaporized rust conversion agent converts the red rust on the inner surface of the hollow steel material in the voids to black rust and suppresses the occurrence of red rust. be able to. Also, even if a hole is made in the hollow steel material filled with the rust conversion agent-containing urethane foam and water enters the hollow steel material and contacts the inner surface of the hollow steel material, The rust conversion agent vaporized and adhered to the inner surface of the hollow steel material can suppress the occurrence of red rust and can suppress the progression of red rust in the long term.

As described above, the urethane foam containing the rust conversion agent of the present invention is rust-proof without removing red rust on the surface of the steel material by filling the place where the steel material exists in the back of the gap such as concrete, rock, gravel, etc. An effect can be obtained.
Moreover, the rust prevention method of the hollow steel material of the present invention can perform a rust prevention treatment by injecting and foaming a rust conversion agent-containing urethane raw material into the hollow steel material without removing red rust on the inner surface of the hollow steel material. Can be easily performed. In addition, the occurrence and progression of red rust can be suppressed over the long term.

DESCRIPTION OF SYMBOLS 11 Hollow steel material 13 Hole 15 Rust 21 Rust conversion agent containing urethane raw material 25 Rust conversion agent containing urethane foam 31 Closure member

Claims (2)

In urethane foam that is made by mixing and foaming resin raw materials containing polyols, catalysts, foam stabilizers, and foaming agents, and isocyanate raw materials containing polyisocyanates,
A rust conversion agent-containing urethane foam, wherein at least the resin raw material is mixed with a rust conversion agent.   In the method of rust-proofing the inner surface of a hollow steel material, a hole is formed in the hollow steel material, and a rust conversion agent-containing urethane raw material containing polyols, a catalyst, a foam stabilizer, a foaming agent, a rust conversion agent and an isocyanate raw material is removed from the hole. Filling the hollow steel with the rust conversion agent-containing urethane foam by injecting into the hollow steel material and foaming the rust conversion agent-containing urethane raw material, and then closing the hole Rust prevention method.

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