JPH0324434B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a corrosion protection method for increasing the durability of cementitious material structures against chemical agents. Conventionally, the surface of a concrete structure is left as it is, subjected to a surface treatment such as applying mortar, or further coated with tiles, decorative boards, etc. depending on the purpose. Because it is costly to apply covering materials such as tiles and decorative boards to the surface of concrete structures, in most facilities such as sewage treatment facilities and chemical factories, the surface of concrete structures is left as is or mortar is applied. It is. However, in such cases, it is known that chemical agents can cause damage, resulting in significant deterioration and reduced durability; however, no inexpensive anti-corrosion method has been developed so far. In addition, the surface of concrete structures is sometimes painted with epoxy resin or urethane resin, but the durability of the paint is lower than that of concrete, so repainting is necessary every few years. It was hot. It is an object of the present invention to provide an economical and easy method for increasing the corrosion resistance of cementitious material structures against chemical agents. The corrosion prevention method for cementitious structures in water of the present invention involves coating the surface of a cementitious structure with a paint that allows carbon dioxide gas and/or carbonate ions to pass through, but does not allow calcium ions to pass through, thereby preventing elution of calcium ions. The method is characterized in that the surface of the structure is converted into calcite by 5% (by weight) for one year or more using carbon dioxide gas and/or carbonate ions that have passed through the coating film of the paint. The present invention will be explained in more detail below. It is generally known that the hardening of Portland cement is carried out by the following formula. 3C ₃ S＋6H ₂ O→C ₃ S ₂ H ₃ ＋3Ca(OH) ₂ 2C ₂ S＋4H ₂ O→C ₃ S ₂ H ₃ ＋Ca(OH) _{2The Ca(OH) 2 generated} at this time is about 0.03% in the air.
Calcium carbonate is produced by the carbon dioxide gas contained or carbonic acid dissolved in water as shown in the following formula.
This calcium carbonate generally has a calcite crystal system. Ca(OH) ₂ +CO ₂ →CaCO ₃ +H ₂ O Normally, the rate of calcification of carbonate (calcitization) is extremely slow, and it takes about 5 years for it to progress to a depth of 1 cm from the surface of a cementitious material structure. It is said. Therefore, during this period, there have been many cases where cementitious material structures are eroded before they are sufficiently converted into calcite. For example, in sewage treatment plants, facilities built in ancient times are still being used without any damage to this day, while sedimentation basins in newly constructed sewage treatment plants are severely damaged. . This is because phosphorus compounds and sulfur compounds caused by detergents and other chemical agents have been increasing in sewage in recent years, and these compounds are causing Ca in cementitious materials.
It is thought to react with (OH) ₂ to damage and deteriorate cementitious materials. However, in sewage facilities built in ancient times, hardening of the cementitious material was completed before phosphorus and sulfur compounds increased, and calcium carbonate in the cementitious material gradually converted to calcite over a long period of time. This is thought to be due to the fact that it has a dense structure and is not damaged even if phosphorus compounds and sulfur compounds increase later. In the present invention, by forming a coating film on the surface of a cementitious material structure that allows carbonic acid and/or carbonate ions to pass through but does not allow calcium ions to pass through, the initial elution of calcium ions is prevented.
The cementitious material is sufficiently converted into calcite. By completing this calcite formation during the durability period of the coating film, corrosion protection can be provided by the calcite layer even after the coating film has peeled off. Therefore, by applying the coating once, the anticorrosion properties of the cementitious material structure can be significantly improved. Conventionally, the direction of paint research and development has been to form a complete coating film and suppress permeability as much as possible. The focus of the present invention is to reverse this idea and utilize a coating film that allows permeation of carbon dioxide gas and/or carbonate ions. The base resin of the paint that can be used in the present invention has a water absorption rate of 0.05 to 3.0%, particularly 0.1 to 2.0%.
It is desirable to select from a range of %. If the water absorption rate is too low, permeation of carbon dioxide gas and/or carbonate ions will be poor, and if it is too high, calcium ions will permeate, and calcite formation may not be performed sufficiently. Specific examples of base resin include acrylic resin,
For example, neutral monomers include acrylic esters and methacrylic esters (hereinafter simply referred to as (meth)).
Monomers containing acid groups and acid anhydride groups, such as (meth)acrylic acid, itaconic acid, maleic acid, and maleic anhydride, such as (meth)acrylic acid, styrene, styrene, etc., and monomers containing hydroxyl groups, such as (meth) Hydroxyethyl acrylate, hydroxypropyl (meth)acrylate, etc. Epoxy group-containing monomers such as glycidyl methacrylate, nitrogen-containing monomers such as (meth)acrylamide; Urethane resins, such as oil-modified urethane resins, 1-liquid moisture Cured polyurethane resin, 2-part catalyst-cured polyurethane resin, 2-part polyol-cured urethane resin, thermosetting 1
Liquid polyurethane resins, etc.; epoxy resins, such as epichlorohydrin bisphenol A type, novolak type, β-methyl epichloro type, brominated type, cycloaliphatic type (cyclic oxirane type, glycidyl ether type, glycidyl ester type), acyclic aliphatic type (polyglycol ether type, glycol ether type), epoxidized type of aliphatic unsaturated compound (epoxidized polybutadiene), epoxidized fatty acid ester (epoxidized natural oil), polyhydric carboxylic acid ester type, aminoglycidyl type, chlorinated Epoxy resins of type, resorcin type, epoxy tar modified type, etc.; curing agents for epoxy resins of aliphatic diamines, amide polyamines, polyamides, etc.; polyester resins, such as unsaturated polyester resins, alkyd resins, oil-free alkyd resins, Linear polyester resins, etc.; amino resins, such as butylated melamine resins; vinyl resins, such as vinyl acetate resins, vinyl butyral resins, vinyl chloride resins, vinyl chloride copolymer resins, such as vinyl acetate, in combination with (meth)acrylic acid; Polymers, etc.; nylon resin, nylon copolymer resin, such as 6,6 nylon, 6 nylon,
Copolymer resins such as 6,10 nylon; fluorine resins,
For example, resins such as 1-fluorocarbon resin and 2-fluorocarbon resin can be mentioned. Among these, preferred are methacrylic acid resin, unsaturated polyester resin, vinyl chloride copolymer resin, bisphenol type epoxy resin, and polyurethane resin. Pigments that have as little hiding power as possible are used as pigments that can be used in the preparation of the paint used in the present invention. Such pigments include carbonate lime powder, precipitated calcium carbonate, clay, silica, white carbon, diatomaceous earth, talc, magnesium carbonate, alumina white, zinc white, lead white, etc. Especially, carbonate lime powder, precipitated calcium carbonate are suitable for the purposes of the present invention. gypsum, barium sulfate,
Sulfates and barium salts such as barium carbonate and lead sulfate are not preferred because they react with cementitious material structures. In preparing the paint, the following ingredients are used: a base resin, a pigment, a solvent such as xylol, toluol, methyl isobutyl ketone, a plasticizer such as dimethyl phthalate, dioctyl phthalate, tricresyl phosphate, and a dispersant such as the product name "Anti-Tera U". ”, “Lactimon” or “BYK-P-104”
(all manufactured by BYK-Maelinckrodt), emulsifier,
For example, sodium dodecylbenzenesulfonate, polyoxyethylene nonyl phenyl ether, alkylpyridinium salt, curing agent, such as polyisocyanate resin, trade name "Burnok D"
-800'', ``Burnock D-750'', ``Burnock
DN950” (all manufactured by BYK-Maelinckroodt)
etc. are appropriately blended as necessary and dispersed and kneaded using a roll mill, flat stone mill, ball mill, etc. Although the blending ratio is not particularly critical, it is approximately 10 to 300 parts by weight of pigment and 0.1 to 300 parts by weight of other additive components to 100 parts by weight of base resin. Furthermore, when carrying out the present invention, it is also possible to apply two or more types of paint over each other. In this case, it is preferable to use an undercoat based on a resin with a higher water absorption rate. When applying the anti-corrosion method of the present invention, a specimen having the same composition as the actually used cementitious material structure is prepared and left in the same environment as that in which it will actually be used. The degree of calcite formation, that is, the degree of selective permeability of the coating film, can be determined by sampling up to 1 cm of the surface of the specimen after leaving it for an appropriate period of time, for example, one year, and performing thermogravimetric analysis.
That is, calcium hydroxide undergoes a dehydration reaction at 400 to 500°C, and calcium carbonate undergoes a decarboxylation reaction at 650 to 900°C to reduce weight. The amount of calcium hydroxide and calcium carbonate can be determined from this weight loss. Measured by this method, if 5% (weight) or more of calcium is converted to calcite in one year and the amount of calcium hardly changes, calcite with sufficient corrosion resistance will be produced in several years. The present invention will be explained below with reference to examples. Note that parts and percentages are based on weight. Example 1 A white acrylic resin paint was prepared with the following composition. Acrylic resin varnish (product name: “Acrydek A”)
-180'') ¹⁾ 60 parts calcium carbonate (product name ``Escalon #200'') ^2
) 25 parts Additive (product name "Anti-Taylor U") ³⁾ 1.0 part (product name "BYK-P104") ⁴⁾ 1.0 part toluene 13 parts 100 parts 1) Manufactured by Dainippon Ink & Chemicals Co., Ltd. 2) Sankyo Seifun Co., Ltd. 3) 4) BYK-Maelinckrodt A part of the acrylic resin varnish, a pigment, an additive, and a part of the solvent are premixed and applied to a dispersion machine.
After dispersion, a paint was prepared using the remaining acrylic resin varnish and solvent. Note that the water absorption rate of the acrylic resin was 0.15%. The acrylic resin paint thus prepared was applied to a mortar specimen (10 cmφ x 20 cm L, 50 parts of Portland cement, 100 parts of fine aggregate) to an average thickness of 3.0 mm, and the sample was immersed in water at 200 ± 10°C. . The concentration of phosphorus compounds in water is 10-40ppm, the concentration of sulfur compounds is 20-100ppm, and the concentration of nitrogen compounds is 0.2-40ppm.
It was 20ppm. After 12 months, it was taken out of the water, a 1 cm thickness of the surface was scraped off, and thermal polymerization analysis revealed that it had become 48% calcite. Note that the amount of calcium did not change. The results of differential thermogravimetric analysis are shown in the attached drawings. The measurement conditions were as follows.

[Table] Example 2 A white epoxy resin paint was prepared from the following composition. Main ingredient: Epoxy resin varnish (product name “Epicote”)
1001−75X”) ¹⁾ 40 parts calcium carbonate 20 parts Additive (Product name “BYK-SL”) ²⁾
0.3 parts (Product name "BYK-052") ³⁾ 0.2 parts (Product name "BYK-P104") ⁴⁾ 0.5 parts Xylene 5 parts Cellosolve 2 parts Curing agent: Polyamide curing agent (Product name "Versamide")
415'') ⁵⁾ 23 parts xylene 6 parts n-butanol 3 parts 100 parts 1) Manufactured by Yuka Ciel Epoxy Co., Ltd. 2) - 4) Manufactured by BYK-Maelinckrodt 5) Manufactured by Fuji Kasei Co., Ltd. Part of epoxy resin varnish and calcium carbonate,
Additives and a portion of the solvent were used to disperse in a disperser. A paint was prepared with the remaining resin varnish and solvent. A curing agent was prepared by mixing a polyamide curing agent and a solvent. At the time of use, the main agent and curing agent were mixed together. Note that the water absorption rate of the epoxy resin was 0.23%. When the same test as in Example 1 was conducted, the calcite formation was 24%. The amount of calcium remained unchanged. Example 3 A white urethane resin paint was prepared from the following composition. Urethane resin varnish (product name: “Barnotsu DM”)
−652”) ¹⁾ 60 parts calcium carbonate (product name “Softon 1200”) ²⁾
30 parts toluene 10 parts 100 parts 1) Manufactured by Dainippon Ink & Chemicals Co., Ltd. 2) Manufactured by Bihoku Funka Co., Ltd. A paint was prepared using a part of urethane resin varnish and a pigment using a dispersion machine and the solvent after dispersion. Urethane resin paint has a limited pot life, so after manufacturing
Used for painting within 24 hours. Note that the water absorption rate of the urethane resin was 1.8%. When the same test as in Example 1 was conducted, the calcite formation was 54%. The amount of calcium remained unchanged. Example 4 A white vinyl resin paint was prepared from the following composition. Vinyl resin varnish (product name “Vinyroll 92T”) ¹⁾
25 parts calcium carbonate (product name "Softon 1500") ²⁾
23 parts Additive (product name "Lactimon") ³⁾ 1.0 part (product name "Anti-Tera P") ⁴⁾
1.0 parts Plasticizer (dimethyl phthalate) 3 parts Acetate ester 13 parts MIBK (methyl isobutyl ketone) 8 parts Toluene 18 parts Xylene 8 parts 100 parts 1) Manufactured by Showa Kobunshi Kagaku Co., Ltd. 2) Manufactured by Bihoku Funka Co., Ltd. 3) 4) BYK-Maelinckrodt A part of the vinyl resin varnish, an additive, a plasticizer, and a part of the solvent were used in a dispersion machine, and after dispersion, a paint was prepared with the remaining resin varnish and solvent. Note that the water absorption rate of the vinyl resin was 1.8%. When the same test as in Example 1 was conducted, the calcite formation was 63%. Moreover, the amount of calcium remained unchanged. Example 5 A white polyester resin paint was prepared from the following composition. Polyester resin varnish (product name: Polyset
¹⁾ 71.6 parts accelerator (product name ``PT-42'') <sup>2)</sup> 0.7 parts (product name ``PT-28'') ³⁾ 0.3 parts hardening agent (product name ``CT-3'') ⁴⁾ 0.4 parts Calcium carbonate 15 parts Talc 10 parts Additive (Product name "BYK-P104") ⁵⁾ 1.0 part (Product name "Lactimon") ⁶⁾ 1.0 parts 100 parts 1) - 4) Hitachi Chemical Co., Ltd. 5) 6) BYK-Maelinckrodt Polyester resin, pigment, and additives were dispersed in a dispersion machine to obtain a main ingredient. The paint was prepared using the remaining curing agent and accelerator at the time of paint use. The water absorption rate of the polyester resin was 0.3%. When the same test as in Example 1 was conducted, the amount of calcite formation was 19%, and the amount of calcium remained unchanged.

[Brief explanation of drawings]

The attached drawing is a graph showing the analysis results of a specimen to which the anticorrosion method of the present invention was applied.

Claims (1)

[Claims] 1. A paint that permeates carbon dioxide gas and/or carbonate ions but not calcium ions is applied to the surface of a cementitious material structure, and the coating film of the paint is applied to the surface of the structure without eluting calcium ions. A method for preventing corrosion of cementitious materials in water, which is characterized by converting 5% (by weight) per year of calcite into permeated carbon dioxide gas and/or carbonate ions.