JP7540653B2 - Water absorption prevention material for civil engineering and construction materials - Google Patents

Description

The present invention relates to a water absorption prevention material for civil engineering and construction materials.

Water-absorption prevention materials are sometimes used in civil engineering and construction applications. For example, water-absorption prevention materials are sometimes used for reinforced concrete. For example, Japanese Patent Application Laid-Open No. 2003-155582 (Patent Document 1) proposes that the water-absorption prevention material described in the publication prevents corrosion of reinforcing bars in reinforced concrete.

JP 2003-155582 A

Alkylalkoxysilanes and/or condensates thereof are useful as water absorption prevention materials for civil engineering and building materials (more specifically, reinforced concrete). For example, by applying the water absorption prevention material to civil engineering and building materials, the civil engineering and building materials after application can be prevented from infiltrating deterioration factors such as water and salt from the outside.

However, after extensive research, the present inventors have found that while alkylalkoxysilanes and/or condensates thereof are useful as water absorption inhibitors, there is still room for improvement. For example, if deterioration factors have already infiltrated into civil engineering and building materials, the reinforcing steel in reinforced concrete is corroded by the deterioration factors. In such cases, applying a water absorption inhibitor to civil engineering and building materials cannot adequately suppress corrosion (more specifically, rust, etc.) of metals such as reinforcing steel. For example, such problems are likely to become evident in civil engineering and building materials, particularly in existing civil engineering and building materials installed outdoors. Existing civil engineering and building materials are exposed to deterioration factors, and may be exposed to wind and rain in rainy weather and to salt-containing moisture at the seaside.

The present invention was made in consideration of these problems. That is, the main objective of the present invention is to provide a water absorption prevention material for civil engineering and building materials that can suppress further penetration of external deterioration factors into civil engineering and building materials, while more sufficiently suppressing corrosion of metals such as reinforcing bars, even in civil engineering and building materials that already contain deterioration factors.

As a result of intensively studying the above problem, the inventors have found that in civil engineering and building materials in which deterioration factors are already present, even if a water absorption prevention material is applied, the deterioration factors cannot be prevented from penetrating into the surroundings of metals such as reinforcing bars, causing the metals to corrode. Based on this technical knowledge, the inventors have focused on the characteristics of (B) the volatile rust inhibitor, and have come up with the idea that by allowing the rust inhibitor to penetrate into the surroundings of metals such as reinforcing bars, which are to be prevented from deterioration, through a microstructure such as voids in the civil engineering and building material, and creating an anti-corrosive atmosphere around the metals such as reinforcing bars, corrosion of the metals such as reinforcing bars can be more sufficiently suppressed. In this specification, the voids in the civil engineering and building material refer to, for example, when the civil engineering and building material is reinforced concrete, fine voids that are generated by the evaporation of moisture contained in the concrete.

In order to solve the above problems, the present invention includes a water absorption prevention material for civil engineering and construction materials according to the following item 1.
Item 1.
A water absorption prevention material for civil engineering and building materials, comprising (A) an alkylalkoxysilane and/or a condensate thereof, and (B) a thixotropic agent,
The water absorption prevention material for civil engineering and building materials contains, in addition to the (A) alkylalkoxysilane and/or its condensate and the (B) thixotropic agent, (C) a slow-drying volatile rust inhibitor.

The water absorption prevention material for civil engineering and building materials of the present invention can suppress further penetration of external deterioration factors into civil engineering and building materials, while more fully suppressing corrosion of metals such as reinforcing bars, even in civil engineering and building materials that already contain deterioration factors.

Numerical ranges mentioned in this specification are intended to include the lower and upper limits themselves, unless otherwise specified by terms such as "less than" and "more than/greater than." In other words, taking a numerical range such as 3% by mass to 10% by mass as an example, the numerical range is interpreted as including the lower limit of "3% by mass" and the upper limit of "10% by mass." In addition, terms such as "about" and "to the extent of" mean that the numerical value in question may vary by a few percent (e.g., ±10%).

The following provides a detailed explanation of the water absorption prevention material for civil engineering and building materials (hereinafter simply referred to as "water absorption prevention material") according to an embodiment of the present invention. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters or duplicated constructions of substantially the same configuration may be omitted. This is to avoid unnecessarily lengthy explanations and to facilitate understanding by those skilled in the art. Note that the forms and the like described below are intended to explain the embodiments according to the present invention and do not particularly limit the present invention.

The water absorption prevention material according to this embodiment is
A water absorption preventing material comprising (A) an alkylalkoxysilane and/or a condensate thereof, and (B) a thixotropic agent,
The water absorption prevention material contains, in addition to the (A) alkylalkoxysilane and/or its condensate and the (B) thixotropic agent, (C) a slow-drying volatile rust inhibitor.
The water absorption prevention material according to this embodiment may further comprise (D) a polar solvent and/or (E) a hydrophobic silica powder. These components (A) to (E) will be described below.

[(A) Alkylalkoxysilane and/or its condensate]
When the water absorption prevention material according to the present embodiment contains (A) an alkylalkoxysilane and/or its condensate, it can suppress further penetration of external deterioration factors into the civil engineering and building materials, while more fully suppressing corrosion of metals such as reinforcing bars, even in civil engineering and building materials that already have deterioration factors inside. The alkylalkoxysilane and its condensate modify the surface of the civil engineering and building materials, forming a water absorption prevention layer on the surface (more specifically, the inner and outer surfaces) in which hydrophobic alkyl groups and the like are oriented, and can exhibit water repellency. This water absorption prevention layer, for example, imparts a rust prevention effect to the reinforced concrete by suppressing contact of the reinforcing bars in the reinforced concrete with water.

In alkylalkoxysilanes, the alkoxy groups undergo a silane coupling reaction with the surfaces (inner and outer surfaces) of civil engineering and building materials, arranging alkyl groups and the like on the surface of the civil engineering and building materials. Because the arranged alkyl groups are hydrophobic groups, the modified civil engineering and building material surface has water absorption prevention properties (water repellency). In this way, alkylalkoxysilanes can impart water repellency to civil engineering and building materials.

The alkylalkoxysilane is not particularly limited, but may be, for example, a compound represented by the following general formula (1):
R ¹ _n Si(OR ² ) _4-n (1)
[In the general formula (1), R ¹ represents an alkyl group having 1 to 20 carbon atoms, R ² represents an alkyl group having 1 to 4 carbon atoms, n represents 1 or 2, and when n represents 2, multiple R ^1s may be the same or different from each other, and multiple R ^2s may be the same or different from each other]
Examples of the compound include compounds represented by the following formula:

In the general formula (1), the alkyl group having 1 to 20 carbon atoms represented by R ¹ may be linear or branched. The alkyl group having 1 to 20 carbon atoms represented by R ¹ is, for example, at least one selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl. If the number of carbon atoms is 20 or less, it is preferable because the alkylalkoxysilane can easily penetrate into the interior of the civil engineering and building material. Among these, the alkyl group having 1 to 20 carbon atoms represented by ^R1 is preferably an alkyl group having 4 to 20 carbon atoms, more preferably an alkyl group having 4 to 12 carbon atoms (more specifically, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and/or a dodecyl group, etc.), still more preferably an alkyl group having 4 to 8 carbon atoms, and particularly preferably an alkyl group having 5 to 7 carbon atoms, for example, a hexyl group.

The alkyl group having 1 to 20 carbon atoms represented by ^R1 may further have a substituent. Such a substituent is, for example, at least one selected from the group consisting of a vinyl group, an epoxy group, a methacryloxy group, an acryloxy group, an amino group, a chloropropyl group, and an isocyanate group. When such a substituent is present, the number of the substituent is usually one.

In the general formula (1), the alkyl group having 1 to 4 carbon atoms represented by R ² may be linear or branched. Examples of the alkyl group having 1 to 4 carbon atoms represented by R ² include a methyl group, an ethyl group, a propyl group, and a butyl group. Among these, the alkyl group having 1 to 4 carbon atoms represented by R ² is preferably an alkyl group having 1 to 3 carbon atoms (more specifically, a methyl group, an ethyl group, and a propyl group) if it is more important to increase the reactivity of the alkylalkoxysilane, to easily condense, and to improve the water absorption prevention property of the water absorption prevention material. Furthermore, among the alkyl groups having 1 to 3 carbon atoms, for example, an ethyl group is more preferable if it is more important to work with ease. The alkylalkoxysilane may have one or more substituents. When it has multiple substituents, the multiple substituents may be the same or different from each other. The substituent is, for example, selected from the group consisting of an epoxy group (glycid group), an amino group, an isocyanate group, a vinyl group, a (meth)acryloyloxy group, and a halogen group.

Examples of such alkylalkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, pentyltrimethoxysilane, pentyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, nonyltrimethoxysilane, nonyltriethoxysilane, ethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, undecyltrimethoxysilane, undecyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, tridecyltrimethoxysilane, tridecyltriethoxysilane, tetradecyltrimethoxysilane, tetradecyltriethoxysilane, pentadecyltrimethoxysilane, pentadecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, heptadecyltrimethoxysilane, heptadecyltriethoxysilane, octadecyltrimethoxysilane, Trimethoxysilane, octadecyltriethoxysilane, dimethyldimethoxysilane, octylmethyldimethoxysilane, octadecylmethyldimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyl At least one selected from the group consisting of 3-methyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethoxysilane, N-2-(aminoethyl)-3-aminopropylethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane.

Among these, alkoxysilanes are preferred because they are easily available, and if emphasis is placed on improving the water repellency imparting function of the water absorption prevention material, alkoxysilanes in which the alkyl group represented by R ¹ in general formula (1) has 4 or more carbon atoms and the alkyl group represented by R ² has 1 to 3 carbon atoms (more specifically, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, etc.) are preferred, with hexyltriethoxysilane being more preferred. These alkylalkoxysilanes may be used alone or in combination of two or more (i.e., may be used as a mixture of alkoxysilanes).

The alkylalkoxysilane may be volatile. If the alkylalkoxysilane is volatile, it can easily penetrate into the microstructure of the civil engineering and building material, like the slow-drying volatile rust inhibitor (C) described below, and therefore can more fully modify not only the outer surface of the civil engineering and building material but also the inner surface to impart water repellency. In this specification, the volatile nature of the alkoxysilane is synonymous with the "volatile nature" of the slow-drying volatile rust inhibitor (C) described below.

An alkylalkoxysilane condensate is a molecule in which two or more molecules of at least one of the above alkylalkoxysilanes are condensed.

The content of the alkoxysilane is 80 to 99 parts by mass per 100 parts by mass of the water absorption prevention material. The content of (A) alkoxysilane and/or its condensate is, for example, 87 to 94 parts by mass (87 to 94% by mass) per 100 parts by mass (100% by mass) of the total mass of (A), (B) and (C). From the viewpoint of further improving the rust prevention property and the rust inhibitor penetration and retention property (described in detail below), the content of (A) is preferably 87 to 93 parts by mass (87 to 93% by mass) per 100 parts by mass (100% by mass) of the total mass of (A), (B) and (C). From the viewpoint of further improving the water repellency, the content of (A) is preferably 90 to 94 parts by mass (90 to 94% by mass) per 100 parts by mass (100% by mass) of the total mass of (A), (B) and (C). From the viewpoint of further improving rust prevention, water repellency, and rust inhibitor penetration and retention, the content of (A) is preferably 90 to 93 parts by mass (90 to 93% by mass) per 100 parts by mass (100% by mass) of the total mass of (A), (B), and (C).

[(B) Thixotropic Agent]
When the water absorption prevention material according to the present embodiment contains the thixotropic agent (B), even if the civil engineering and building materials already have deterioration factors inherent therein, corrosion of metals such as reinforcing bars can be more sufficiently suppressed. The reason is presumed to be as follows, without being bound by a specific theory. When the water absorption prevention material contains the thixotropic agent (B), when the water absorption prevention material is applied to the outer surface of the civil engineering and building materials to form a coating layer, the thixotropic agent with a relatively large molecular weight is difficult to penetrate into the civil engineering and building materials, and tends to remain on the surface of the coating layer. For this reason, the thixotropic agent acts like a "lid" in the coating layer, suppressing the volatilization of the (A) and (C) components into the atmosphere. It is considered that this promotes the penetration of the (A) and (C) components into the civil engineering and building materials, and makes it easier to form a water absorption prevention layer derived from the (A) and (C) components on the inner surface of the civil engineering and building materials.

Furthermore, since component (A) forms a bond on the inner surface of the civil engineering building material, for example, by a coupling reaction, the water absorption prevention layer derived from component (A) tends to maintain its function (water repellency) relatively stably. In contrast, component (C) forms a relatively weak bond, such as physical adsorption, on the inner surface of the civil engineering building material, so that the water absorption prevention layer derived from component (C) usually has difficulty maintaining its function (rust prevention) due to the volatilization and detachment of component (C) from the inner surface of the civil engineering building material. However, in this embodiment, since the thixotropic agent continues to remain in the water absorption prevention layer (the layer where the coating layer of the water absorption prevention material has dried), it is thought that component (C) in particular remains inside the civil engineering building material for a long period of time and maintains its rust prevention properties.

Examples of thixotropic agents include organic thixotropic agents and/or inorganic thixotropic agents. Among these, organic thixotropic agents are preferred if greater importance is placed on improving peeling and whitening.

The organic thixotropic agent is preferably at least one selected from the group consisting of hydrogenated castor oil-based thixotropic agents, amide wax-based thixotropic agents, polyethylene oxide-based thixotropic agents, polyolefin-based thixotropic agents, sulfate ester-based thixotropic agents, dimer acid ester-based thixotropic agents, polycarboxylic acid-based thixotropic agents, and vegetable oil-based thixotropic agents. Of these, the organic thixotropic agent is more preferably an amide wax-based thixotropic agent, which has good compatibility with component (A) and is easily swellable.

Examples of commercially available thixotropic agents include, for example, Talen 5400-25 (manufactured by Kyoeisha Chemical Co., Ltd.; amide wax-based thixotropic agent), Talen 5500-25 (manufactured by Kyoeisha Chemical Co., Ltd.; amide wax-based thixotropic agent), Flownon SA-300 (manufactured by Kyoeisha Chemical Co., Ltd.; polyethylene oxide-based thixotropic agent), Disparlon (registered trademark) 4300 (manufactured by Kusumoto Chemical Co., Ltd.; hydrogenated castor oil-based thixotropic agent), Disparlon (registered trademark) 6820-20M (manufactured by Kusumoto Chemical Co., Ltd.; amide wax-based thixotropic agent), Disparlon (registered trademark) 4200-20 (manufactured by Kusumoto Chemical Co., Ltd.; polyethylene oxide-based thixotropic agent), A-S-A T-20 (manufactured by Ito Oil Co., Ltd.; hydrogenated castor oil-based thixotropic agent), A-S-A Examples of thixotropic agents include T-1700 (manufactured by Ito Oil Mills; amide wax-based thixotropic agent), and A-S-A D-10A (manufactured by Ito Oil Mills; polyethylene oxide-based). Among these, particularly good commercially available thixotropic agents are Tallen 5400-25 and Disparlon (registered trademark) 6820-20M.

An example of an inorganic thixotropic agent is bentonite.

If it is important to adjust the viscosity of the water absorption prevention material to an appropriate level to improve workability, promote penetration into the interior of the civil engineering and construction material, and maintain water absorption prevention performance for a longer period of time, the content of the thixotropic agent is preferably 0.1 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of component (A).

The content of the thixotropic agent (B) is, for example, 5.6 to 6.0 parts by mass (5.6 to 6.0% by mass) relative to the total mass of (A), (B) and (C) of 100 parts by mass (100% by mass). From the viewpoint of further improving the rust prevention property and the rust inhibitor penetration and retention, the content of (B) is preferably 5.6 to 5.9 parts by mass (5.6 to 5.9% by mass) relative to the total mass of (A), (B) and (C) of 100 parts by mass (100% by mass). From the viewpoint of further improving the water repellency, the content of (B) is preferably 5.7 to 6.0 parts by mass (5.7 to 6.0% by mass) relative to the total mass of (A), (B) and (C) of 100 parts by mass (100% by mass). From the viewpoint of further improving rust prevention, water repellency, and rust inhibitor penetration and retention, the content of (B) is preferably 5.7 to 5.9 parts by mass (5.7 to 5.9% by mass) per 100 parts by mass (100% by mass) of the total mass of (A), (B), and (C).

[(C) Slow-drying volatile rust inhibitor]
When the water absorption prevention material according to the present embodiment contains (C) a slow-drying volatile rust inhibitor, it is possible to suppress further infiltration of deterioration factors from the outside, while more fully suppressing corrosion of metals such as reinforcing bars, even in civil engineering and building materials in which deterioration factors are already present. The reason is presumed to be as follows, without being bound by a specific theory. A slow-drying volatile rust inhibitor is a volatile rust inhibitor that evaporates relatively slowly. When a water absorption prevention material is applied to the outer surface of a civil engineering and building material to form a coating layer, the slow-drying volatile rust inhibitor in the coating layer penetrates more effectively into the civil engineering and building material through a microstructure such as a void in the civil engineering and building material. And it is easy to maintain the state in which it penetrates into the civil engineering and building material. This makes the surroundings of metals such as reinforcing bars in the civil engineering and building material a rust-preventive atmosphere, and this state is stably maintained, so that corrosion of the metal can be suppressed.

In order to create a rust-preventive atmosphere around the metals constituting the civil engineering building materials, the inventors focused on the "slow-drying" of the slow-drying volatile rust inhibitor, which is advantageous for effective penetration into the civil engineering building materials. More specifically, as described above, the slow-drying volatile rust inhibitor penetrates into the civil engineering building materials in gas form, so it is easier to penetrate into the microstructure and coat the inner surface of the civil engineering building materials. Without being bound by a particular theory, this is thought to be because the slow-drying volatile rust inhibitor can sufficiently penetrate into the civil engineering building materials in a gas form in an isolated state at the monomolecular level. In contrast, for example, a non-volatile rust inhibitor in liquid form (especially a non-volatile rust inhibitor that maintains its liquid form for a relatively long period of time) penetrates into the microstructure in liquid form, which is an aggregate of multiple molecules, and is therefore at an overwhelming disadvantage in terms of size compared to a gas form, and it is thought that this difference in size contributes to the ease of penetration.

Furthermore, the inventors focused on the "slow drying" of slow-drying volatile rust inhibitors in order to maintain a rust-preventive atmosphere around metals. Slow-drying volatile rust inhibitors evaporate relatively slowly and have an appropriate vapor pressure, making it easy to maintain a continuous rust-preventive atmosphere around metals. In contrast, while fast-drying volatile rust inhibitors are thought to penetrate the microstructure, they tend to leave the microstructure due to their fast drying properties, making it difficult to maintain a stable rust-preventive atmosphere inside civil engineering and construction materials for a long period of time.

As such, the present invention was completed by the inventors by focusing on the "slow-drying" nature of slow-drying volatile rust inhibitors, which have a well-balanced combination of the ability to penetrate (penetrate) into microstructures and the ability to be continuously retained in the microstructure. In this specification, the property of such slow-drying volatile rust inhibitors is also referred to as "rust inhibitor penetration and retention."

In this specification, "vaporizable" refers broadly to the property of vaporization (particularly to those generally recognized by those skilled in the art as having "vaporizable"), and in the narrow sense refers to the case where the mass loss rate measured using a differential thermal/thermogravimeter is in a specific numerical range described below. In addition, "non-vaporizable" refers broadly to the property of not vaporizing or being difficult to vaporize (particularly to those generally recognized by those skilled in the art as not having "vaporizable"), and in the narrow sense refers to the case where the mass loss rate measured using a differential thermal/thermogravimeter is in a specific numerical range described below.

On the other hand, the inventors have found that simply incorporating a slow-drying volatile rust inhibitor into a water absorption prevention material does not allow a rust-preventive atmosphere to be formed sufficiently due to the "volatility" of the slow-drying volatile rust inhibitor. More specifically, the inventors have found that the "volatility" of the slow-drying volatile rust inhibitor causes most of it to volatilize from the coating layer when the coating layer is formed, preventing it from penetrating sufficiently into the civil engineering and building materials, and that even the small amount of slow-drying volatile rust inhibitor that does penetrate into the civil engineering and building materials is gradually volatilized and desorbed from the inner surface of the civil engineering and building materials due to its "volatility", decreasing the amount, making it impossible to maintain a rust-preventive atmosphere for a long period of time.

After extensive research, the inventors came up with the idea of combining the slow-drying volatile rust inhibitor with a thixotropic agent (B) in order to maintain the advantageous function of the "volatility" of the slow-drying volatile rust inhibitor, "ease of penetration into the interior of civil engineering and building materials," while suppressing the disadvantageous function of "evaporation into the atmosphere during the formation of the coating film and after the formation of the water-absorption prevention layer." More specifically, focusing on the fact that the thixotropic agent has a relatively large molecular weight, the inventors came up with the idea of making the thixotropic agent act like a "lid" in the coating layer and in the water-absorption prevention layer (the layer formed after the coating layer has dried), thereby suppressing the evaporation of the slow-drying volatile rust inhibitor into the atmosphere. In this way, the inventors came up with the idea of combining the (B) component with the (C) component in the water-absorption prevention material according to this embodiment. In other words, the feature of this embodiment is that when the coating layer of the water-absorption prevention material is formed, the thixotropic agent restricts the intrusion direction of the slow-drying volatile rust inhibitor into the civil engineering building material, and after the water-absorption prevention layer is formed, the thixotropic agent keeps the volatile rust inhibitor inside the civil engineering building material. Note that since component (A) can also be volatile, in such a case, from the same viewpoint, component (A) can impart water-repellent properties to the civil engineering building material by combining it with component (B).

The slow-drying volatile rust inhibitor may be a rust inhibitor that evaporates in a relatively short time from the coating layer formed by applying the water absorption prevention material, and more specifically, may be a rust inhibitor that can have a solidified state at the beginning. Examples of such volatile rust inhibitors include salts (more specifically, inorganic acid salts and/or organic acid salts), and if steel applications are particularly important, examples of such volatile rust inhibitors include nitric acid salts as inorganic acid salts and/or carboxylates as organic acid salts. Examples of nitric acid salts include nitrite salts (more specifically, amine nitrite salts, etc.). Examples of carboxylate salts include amine carboxylate salts and/or carboxylate esters. These slow-drying volatile rust inhibitors may be used alone or in combination of two or more types. Of these, slow-drying volatile rust inhibitors that are compatible with component (A) are preferred.

In this specification, "slow-drying" broadly means that evaporation is relatively slow (relatively low vaporizability). In the narrow sense, "slow-drying" means that the mass loss rate measured using a differential thermal/thermogravimeter is in a specific numerical range described below. In addition, in this specification, "quick-drying" broadly means that evaporation is relatively fast (relatively high vaporizability). In the narrow sense, "quick-drying" means that the mass loss rate measured using a differential thermal/thermogravimeter is in a specific numerical range described below.

The vaporizability of a volatile rust inhibitor can be measured at room temperature and pressure (at 25°C and 1 atm) using a differential thermal/thermogravimetric analyzer (TG-DTA, Thermo Plus EVO, manufactured by Rigaku Corporation). A specified amount (15 mg) of volatile rust inhibitor is placed in the measuring device, and the mass change of the sample is measured when the sample is heated according to a specific temperature profile (start temperature 25°C → temperature increase (heating rate 10°C/min) → hold (after reaching 60°C, hold at 60°C for 120 minutes)), and the mass loss rate (%) at the specific temperature relative to the mass at the starting temperature is calculated. In this specification, this vaporizability is determined by measuring the components of the volatile rust inhibitor in question at 100%. In this specification, "vaporizable" refers to the case where the mass loss rate (%) calculated by the above method is in a numerical range exceeding 0% (narrow definition), and "non-vaporizable" refers to the case where the mass loss rate (%) determined by the above measurement method is in a numerical range of 0% or less (i.e., 0%) (narrow definition). Furthermore, in this specification, "vaporizable" being "quick-drying" refers to the case where the mass loss rate (%) determined by the above measurement method is in a numerical range exceeding 25% (narrow definition), and "vaporizable" being "slow-drying" refers to the case where the mass loss rate (%) determined by the above measurement method is in a numerical range exceeding 0% and not exceeding 25% (narrow definition).

As such a slow-drying volatile rust inhibitor, commercially available products may be used. Examples of such commercially available volatile rust inhibitors include VERZONE Crystal #150 (manufactured by Yamato Kasei Kenkyusho Co., Ltd.; amine nitrite salts), VERZONE Crystal #260 (manufactured by Yamato Kasei Kenkyusho Co., Ltd.; amine nitrite salts), and/or VERZONE CR Coat 50 (manufactured by Yamato Kasei Kenkyusho Co., Ltd.; amine carboxylate salts).

The content of the slow-drying volatile rust inhibitor is determined depending on the compatibility with the (A) component, but if the importance is placed on forming a rust-preventive atmosphere inside the civil engineering building material (more specifically, in the pores in the reinforced concrete, etc.), the content is preferably 0.03 to 6 parts by mass (0.1 to 20 parts by mass) per 100 parts by mass of the (A) component, and more preferably 0.3 to 6 parts by mass (1 to 20 parts by mass). The pore volume in the reinforced concrete is generally 0.1 mL/g relative to the total volume of the reinforced concrete. When the mass of the volatile rust inhibitor relative to the total volume of the pores, etc. inside the civil engineering building material is about 5 mg/L, the rust-preventive effect is exhibited, and when it is 20 mg/L, no significant rust is observed. Considering these, in a civil engineering building material with a thickness of concrete covering the reinforcing steel (so-called reinforcing steel cover) of 40 mm, the content of the volatile rust inhibitor is more preferably 0.3 to 3 parts by mass (1 to 10 parts by mass). The numerical range in parentheses for the (C) component above indicates the numerical range of the content of the mixture containing the (C) component (for example, a (C) component-containing mixture such as a (C) component solution) used when preparing the water absorption prevention material according to this embodiment. This is the numerical range of the content of the (C) component-containing mixture when the content of the (C) component in the mixture is 30 mass%. The same applies to the numerical range in parentheses in the next paragraph.

If emphasis is placed on maintaining the water repellency derived from component (A) while also forming a rust-preventing atmosphere, the content of the volatile rust inhibitor is preferably 1.5 to 4.5 parts by mass (5 to 15 parts by mass).

The content of the slow-drying volatile rust inhibitor (C) is, for example, 0.03 to 7.0 parts by mass (0.03 to 7.0% by mass) relative to 100 parts by mass (100% by mass) of the total mass of (A), (B), and (C). From the viewpoint of further improving rust prevention and rust inhibitor penetration and retention, the content of (C) is preferably 1.5 to 7.0 parts by mass (1.5 to 7.0% by mass) relative to 100 parts by mass (100% by mass) of the total mass of (A), (B), and (C). From the viewpoint of further improving water repellency, the content of (C) is preferably 0.03 to 4.3 parts by mass (0.03 to 4.3% by mass) relative to 100 parts by mass (100% by mass) of the total mass of (A), (B), and (C). From the viewpoint of further improving rust prevention, water repellency, and rust inhibitor penetration and retention, the content of (C) is preferably 1.5 to 4.3 parts by mass (1.5 to 4.3% by mass) per 100 parts by mass (100% by mass) of the total mass of (A), (B), and (C).

[(D) Polar Solvent]
In the water absorption prevention material of this embodiment, a polar solvent is not necessarily required, but it is preferable that the material further contains a polar solvent (D) because this can improve workability by appropriately adjusting the viscosity of the water absorption prevention material and increasing the amount applied in one application.

The polar solvent is not particularly limited, but examples thereof include alcohols such as methanol, ethanol, and/or isopropyl alcohol; ketones such as acetone, methyl ethyl ketone, and/or methyl isobutyl ketone; and/or nitriles such as acetonitrile. Among these, the polar solvent is preferably an alcohol, and more preferably ethanol and/or isopropyl alcohol, if it is easy to obtain industrially and economical. These polar solvents may be used alone or in combination of two or more.

If it is important to appropriately adjust the viscosity of the water absorption prevention material to improve workability, the content of the polar solvent is preferably 1 to 5 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the total mass of components (A) and (B).

[(E) Hydrophobic Silica Powder]
In the water absorption prevention material according to the present embodiment, the hydrophobic silica powder is not necessarily essential, but it is preferable for the material to further contain hydrophobic silica powder in order to improve the dispersibility of the thixotropic agent in the water absorption prevention material, and also to improve the water absorption prevention properties of the covered civil engineering and construction material after the water absorption prevention material is applied to the outer surface of the civil engineering and construction material and a water absorption prevention layer is formed (after construction).

The hydrophobic silica powder is not particularly limited, and examples thereof include those produced by producing hydrophilic silica (SiO ₂ ) from raw material silicon tetrachloride by a dry flame method at 1000°C or higher, and then surface-treating the silica with silanes; for example, siloxanes such as dimethyldichlorosilane, dimethylpolysiloxane, methacryloxysilane, and/or hexamethyldisilazane.

Such hydrophobic silica powder (E) may be a commercially available product. Examples of such commercially available hydrophobic silica powder (E) include Aerosil (registered trademark) R805, Aerosil (registered trademark) R972, Aerosil (registered trademark) R711, Aerosil (registered trademark) R202, Aerosil (registered trademark) RY50, Aerosil (registered trademark) RY300, and/or Aerosil (registered trademark) RX300 (all products of Nippon Aerosil Co., Ltd.). These hydrophobic silica powders (E) may be used alone or in combination of two or more types.

Furthermore, if it is important that the hydrophobic silica powder (E) sufficiently forms unevenness on the surface of the civil engineering and building material coated with the water absorption inhibitor, sufficiently performs the role of protecting against ultraviolet rays, and does not impair the design or workability, it is particularly preferable that the average secondary particle size is 7 to 40 μm and the specific surface area is 50 to 300 m ² /g. The particle size and the specific surface area tend to be inversely proportional, and a smaller particle size means a larger specific surface area. The particle size of the hydrophobic silica powder (E) can be measured, for example, by an electrical resistance method using a particle size distribution measuring device ("Coulter Counter" manufactured by Beckman Coulter, Inc.) or a laser diffraction particle size distribution measuring method using a laser diffraction particle size distribution measuring device ("Mastersizer 3000" manufactured by Malvern Panalytical). The specific surface area can be measured, for example, by the BET method using a specific surface area measuring device ("BELSORP MR6" manufactured by Microtrack Bell Co., Ltd.) Examples of the hydrophobic silica powder (E) having a particle size of 7 to 40 μm and a specific surface area of 50 to 300 m ² /g include, among the above-mentioned generally commercially available products, Aerosil (registered trademark) R805, Aerosil (registered trademark) R972, Aerosil (registered trademark) R711, and Aerosil (registered trademark) R202 (all products of Nippon Aerosil Co., Ltd.).

The content of the hydrophobic silica powder is preferably 0 to 2 parts by mass (0 to 2 mass%), particularly 0.1 to 2 parts by mass (0.1 to 2 mass%), relative to 100 parts by mass of component (A) if greater importance is placed on improving the dispersibility of the thixotropic agent, suppressing dusting to facilitate the preparation of the water absorption prevention material, and improving water absorption prevention properties after application. If greater importance is placed on dispersibility when preparing the water absorption prevention material and on surface protection of civil engineering and building materials to which the resulting water absorption prevention material is applied, 0.2 to 1.5 parts by mass (0.2 to 1.5 mass%) is more preferable, and if greater importance is placed on economical aspects, 0.3 to 1.5 parts by mass (0.3 to 1.5 mass%) is even more preferable.

The contents of (A), (B) and (C) are, for example, 87 to 94 parts by mass (87 to 94% by mass), 5.6 to 6.0 parts by mass (5.6 to 6.0% by mass), and 0.03 to 7.0 parts by mass (0.03 to 7.0% by mass), respectively, relative to 100 parts by mass (100% by mass) of the total mass of (A), (B) and (C).
From the viewpoint of further improving the rust prevention properties and the rust inhibitor penetration and retention, the contents of (A), (B) and (C) are preferably 87 to 93 parts by mass (87 to 93 mass%), 5.6 to 5.9 parts by mass (5.6 to 5.9 mass%) and 1.5 to 7.0 parts by mass (1.5 to 7.0 mass%), respectively, relative to 100 parts by mass (100 mass%) of the total mass of (A), (B) and (C).
From the viewpoint of further improving water repellency, the contents of (A), (B) and (C) are preferably 90 to 94 parts by mass (90 to 94% by mass), 5.7 to 6.0 parts by mass (5.7 to 6.0% by mass), and 0.03 to 4.3 parts by mass (0.03 to 4.3% by mass), respectively, relative to 100 parts by mass (100% by mass) of the total mass of (A), (B) and (C).
From the viewpoint of further improving rust prevention, water repellency, and rust inhibitor penetration and retention, the contents of (A), (B), and (C) are preferably 90 to 93 parts by mass (90 to 93% by mass), 5.7 to 5.9 parts by mass (5.7 to 5.9% by mass), and 1.5 to 4.3 parts by mass (1.5 to 4.3% by mass), respectively, relative to 100 parts by mass (100% by mass) of the total mass of (A), (B), and (C).

The water absorption prevention material according to this embodiment may further contain additives such as preservatives, antifungal agents, algae inhibitors, termite inhibitors, and ultraviolet absorbing agents.

[Method of manufacturing water absorption prevention material for civil engineering and building materials]
An example of the method for producing the water absorption prevention material according to this embodiment will be described. The water absorption prevention material according to this embodiment can be produced by, for example, mixing and dispersing (A) alkylalkoxysilane and/or its condensate, (B) thixotropic agent, and (C) slow-drying volatile rust inhibitor, and further (D) polar solvent and (E) hydrophobic silica powder as required, at room temperature using a stirrer with strong shear force such as a homomixer, an ultra dissolver, and a high-pressure homogenizer.

[Method of application to civil engineering and construction materials]
An example of a method for applying the water absorption prevention material according to the present embodiment to a civil engineering and building material will be described below. The water absorption prevention material according to the present embodiment is applied to the outer surface of the civil engineering and building material, and the formed coating layer is dried, so that a water absorption prevention layer derived from the water absorption prevention material can be formed on the outer surface of the civil engineering and building material.

As a means for applying the agent to civil engineering and construction materials, for example, a roller (more specifically, a mastic roller, etc.), a brush, or a spray can be used, but it is preferable to use a mastic roller.

The water absorption prevention material according to this embodiment can usually be applied at 200 to 500 g per ¹ m2 of the outer surface of a civil engineering and building material in one application. In addition, even if the material is reapplied to a surface that has already been applied once, it does not cause a cissing phenomenon because the water absorption prevention material does not contain water, and it is possible to apply it twice or more times. The penetration depth at this time increases with the number of times it is applied. Here, the penetration depth refers to the length that the water absorption prevention material has penetrated into the building material, and is the maximum length from the outer surface of the civil engineering and building material to the inside of the civil engineering and building material where the water absorption prevention material has penetrated perpendicular to the outer surface. Due to this feature, the water absorption prevention material according to this embodiment can be applied not only to newly constructed civil engineering and building materials, but also to civil engineering and building materials to which the water absorption prevention material according to this embodiment has been applied at the time of new construction, and can be reapplied several years later.

Civil engineering and building materials to which the water absorption prevention material according to this embodiment is applied include inorganic and organic materials. Examples of inorganic materials include exposed concrete, lightweight concrete, precast concrete, lightweight foamed concrete (ALC), mortar, joint mortar, asbestos cement board, pulp cement board, wood wool cement board, cement-based extrusion molding board, glass fiber cement board (GRC), carbon fiber cement board, calcium silicate board, gypsum board, hardboard, plaster, gypsum plaster, dolomite plaster, block, brick, tile, roof tile, natural stone, artificial stone, glass wool, rock wool, and ceramic fiber. Examples of organic materials include wood, plywood, and particle board. Civil engineering and building materials may also be materials in which organic and inorganic materials are mixed.

The water-absorption prevention material according to this embodiment is not easily affected by the temperature (more specifically, air temperature) during application, and can be applied when the air temperature is in the range of 0 to 40°C.

The viscosity of the water absorption prevention material according to this embodiment is preferably 1,000 to 10,000 mPa·s at 20°C, and more preferably 1,100 to 7,000 mPa·s. If the viscosity of the water absorption prevention material is 1,000 mPa·s or more at 20°C, it is easy to ensure that the viscosity of the water absorption prevention material is 500 mPa·s or more even if the air temperature during the application of the water absorption prevention material is 30°C or higher. This makes it easy to apply 200 g or more of the water absorption prevention material per ¹ m2 in one application, improving workability. In addition, if the viscosity of the water absorption prevention material is 10,000 mPa·s or less at 20°C, the fluidity of the water absorption prevention material is less likely to decrease, improving workability. The viscosity of the water absorption prevention material in this specification is a viscosity measured using a B-type viscometer (manufactured by Tokyo Keiki) under the conditions of a measurement temperature of 20°C, rotor No. 4, and 30 rpm.

Methods for drying the coating layer include drying by leaving it at room temperature (more specifically, 25°C), drying in the sun, and drying by heating.

Although an embodiment of the present invention has been described above, this embodiment merely shows a typical example of the scope of application of the present invention. Therefore, it will be easily understood by those skilled in the art that the present invention is not limited to the above embodiment, and various modifications can be made. The embodiment of the present invention includes, for example, the following aspects.

[1]
A water absorption prevention material for civil engineering and building materials, comprising (A) an alkylalkoxysilane and/or a condensate thereof, and (B) a thixotropic agent,
The water absorption prevention material for civil engineering and building materials contains, in addition to the (A) alkylalkoxysilane and/or its condensate and the (B) thixotropic agent, (C) a volatile rust inhibitor.
[2]
The water absorption prevention material for civil engineering and building materials according to [1], wherein the (C) volatile rust inhibitor is a slow-drying volatile rust inhibitor that evaporates slowly.
[3]
The content of the volatile rust inhibitor (C) is 0.03 to 6% by mass (0.1% by mass to 20% by mass) relative to 100% by mass of the total mass of the alkylalkoxysilane and/or condensate thereof (A) and the thixotropic agent (B). The water absorption prevention material for civil engineering and building materials according to [1] or [2].
[4]
The water absorption prevention material for civil engineering and building materials according to any one of [1] to [3], wherein the (B) thixotropic agent is an organic thixotropic agent.
[5]
The water absorption prevention material for civil engineering and building materials according to any one of [1] to [4], wherein the (B) thixotropic agent is at least one organic thixotropic agent selected from the group consisting of hydrogenated castor oil-based, amide wax-based, oxidized polyethylene-based, polyolefin-based, sulfate-based, dimer acid ester-based, polycarboxylic acid-based, and vegetable oil-based thixotropic agents.
[6]
The water absorption prevention material for civil engineering and building materials according to any one of [1] to [5], further comprising (D) a polar solvent.
[7]
The water absorption prevention material for civil engineering and building materials according to any one of [1] to [6], further comprising (E) hydrophobic silica powder.
The range of values in parentheses in [3] indicates the content of the mixture containing (C) described above. In this case, it is the ratio (unit: mass%) to the total mass of (A), (B), and (C) being 100% by mass.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

Example 1
92 parts by mass of alkylalkoxysilane (hexyltriethoxysilane), 6 parts by mass of organic thixotropic agent (Kyoeisha Chemical Co., Ltd. "Tallen 5400-25"; amide wax system), 1 part by mass of polar solvent (isopropyl alcohol), 1 part by mass of hydrophobic silica powder (Nippon Aerosil Co., Ltd. "Aerosil (registered trademark) R805") and 15 parts by mass of volatile rust inhibitor (Yamato Kasei Kenkyusho Co., Ltd. "VEZONE CR Coat 50", carboxylic acid amine salts, content of volatile rust inhibitor 30% by mass, notation "CR50" in Table 1 described later) (i.e., substantial content of volatile rust inhibitor 4.5 parts by mass) were stirred at high speed using a homomixer to obtain a water absorption prevention material. The solution viscosity of the obtained water absorption prevention material at 25 ° C. was 600 mPa · s.

(Comparative Example 1)
A water absorption prevention material was obtained in the same manner as in Example 1, except that the mass of the volatile rust inhibitor was changed from 15 parts by mass to 0 parts by mass (i.e., no volatile rust inhibitor was used). The solution viscosity of the obtained water absorption prevention material at 25° C. was 800 mPa·s.

(Comparative Example 2)
A water absorption prevention material was prepared in the same manner as in Example 1, except that the masses of the alkylalkoxysilane, organic thixotropic agent, and hydrophobic silica powder were set to 0 parts by mass, and the mass of the polar solvent was changed to 100 parts by mass.
The compositions of the water absorption inhibitors obtained in Example 1 and Comparative Examples 1 and 2 are summarized in Table 1.

<Method for determining the vaporizability of rust inhibitors>
The measurements were performed using a differential thermal/thermogravimetric analyzer (TG-DTA, "Thermo Plus EVO" manufactured by Rigaku Corporation) under normal temperature and pressure (temperature 25°C and 1 atm). A predetermined amount (15 mg) of the rust inhibitor was placed in the measuring device, and the sample was heated in an open system under 1 atm along a specific temperature profile (start temperature 25°C → temperature increase (heating rate 10°C/min) → hold (after reaching 60°C, hold at 60°C for 120 minutes)). The mass change of the sample was measured. Using the obtained measured value and the mass at the starting temperature, the mass reduction rate (%) at a specific temperature relative to the mass at the starting temperature was calculated. The vaporization property of the rust inhibitor was judged from the calculated mass reduction rate (%) based on the following vaporization property judgment criteria.
(Criteria for determining volatility)
Vaporizable (quick-drying): Mass loss rate (%) exceeds 25% Vaporizable (slow-drying): Mass loss rate (%) is greater than 0% and not more than 25% Non-vaporizable: Mass loss rate (%) is not more than 0% The volatile rust inhibitor of Example 1 had a mass loss rate (%) of 4.4%, and was therefore volatile (slow-drying).

<Evaluation method>
The rust prevention, water repellency, and rust inhibitor penetration and retention of the water absorption prevention material were evaluated by the evaluation methods described below. Unless otherwise specified, these evaluations were performed at room temperature (more specifically, 20° C.), in the atmosphere (more specifically, 1 atm), and in an open system.
[Test Example 1: Rust prevention]
(1) Preparation of specimen A mortar was prepared by mixing a predetermined amount of cement (Portland cement), sand (from Ashigarakami-gun, Kanagawa Prefecture) and water (tap water). The obtained mortar had a cement to sand ratio of 1:3 (mass ratio) and a water/cement ratio of 50 mass%. A deformed reinforcing bar ("D16", manufactured by Kyoei Steel Co., Ltd., diameter 16 mm) was placed in a roughly rectangular specimen molding form, and mortar was further filled and the deformed reinforcing bar was buried so that the cover thickness was 40 mm. After leaving it to stand for one day, the specimen molding was removed (removed from the form). After removing the form, the standard curing was performed for 28 days at room temperature of 20°C and humidity of 100%, and further curing in air for 14 days at room temperature of 20°C and humidity of 60%. The obtained specimen was designated as a "salt-free specimen". The salt-free specimen was assumed to be a civil engineering and building material that does not have any inherent deterioration factors.

A specimen was prepared in the same manner as the specimen without salt, except that salt (Kishida Chemical Co., Ltd.'s "Sodium Chloride Special Grade") was further added to the mortar so that the salt concentration of the specimen was 3.5 kg/ ^m3 . The obtained specimen was designated the "salt-containing specimen." The salt-containing specimen was mixed with salt in advance to resemble existing civil engineering and building materials, and was intended to represent civil engineering and building materials that inherently contain salt as a deterioration factor.
For each of Example 1 and Comparative Examples 1 and 2, two test specimens (one with salt and one without salt) were prepared.

(2) Test method The water absorption prevention materials prepared in Example 1 and Comparative Examples 1 and 2 were applied to the upper surface of the test specimen at a coating amount of 230 g/ ^m2 , and then dried to form a coating surface for evaluation. The surface of the test specimen on which the coating surface for evaluation was formed was the surface on which the rebar was present 40 mm inside the test specimen from the surface.
Thirty cycles of corrosion tests were performed on the coating surface for evaluation. In one cycle, the coating surface for evaluation of the specimen was immersed in 3 mass% salt water, left at 40°C for three days, and then dried at 20°C for four days. The specimen was immersed in salt water so that only the coating surface for evaluation of the specimen was in contact with the salt water. Thirty cycles of corrosion tests were performed on each of the specimens with and without salt.

(3) Evaluation method The corrosion of rebar was estimated using the natural potential measurement method, and the rust prevention properties of the water absorption prevention material were evaluated. The natural potential measurement method measures the natural potential of the rebar against a reference electrode (saturated silver chloride electrode) to check whether there is a decrease in the rebar potential (change in the less potent direction) due to an anodic reaction, and estimates the progress of rebar corrosion. This method utilizes the mechanism of rust formation. Specifically, in the corrosion of rebar, metallic iron is ionized and dissolved from the surface, and an anodic reaction in which electrons are generated, and a cathodic reaction in which the generated electrons react with water and oxygen proceeds, and the dissolved iron ions react with hydroxide ions to become iron hydroxide, iron hydroxide, etc., and rust is generated.
The natural potential of the rebar of the specimen on which the corrosion test was carried out was measured using a corrosion diagnostic device "CM-V" manufactured by Shikoku Research Institute Co., Ltd., and a saturated silver chloride electrode as a reference electrode. From the obtained natural potential, the rust prevention properties of the water absorption prevention material were evaluated based on the following evaluation criteria. The threshold values of the evaluation criteria correspond to the threshold values for determining the corrosiveness of steel materials in ASTM C876. The evaluation results are shown in Table 2.
(Evaluation criteria for rust prevention)
○ (Very good): The natural potential (E) is greater than -80 mV, and there is a 90% or greater probability that there is no possibility of rebar corrosion. △ (Good): The natural potential is greater than -230 mV and less than -80 mV, and there is a less than 10% probability that there is a possibility of rebar corrosion. × (Poor): The natural potential is less than -230 mV, and there is a 90% or greater probability that there is a possibility of rebar corrosion.

(Test Example 2: Water repellency)
A salt-containing specimen having a coating surface for evaluation was prepared in the same manner as the specimen in Test Example 1. The specimen was placed so that the coating surface was horizontal. A water drop with a diameter of 2 mm was placed on the coating surface for evaluation of the specimen, and the contact angle was measured using a contact angle measuring device (Kyowa Interface Science Co., Ltd., Contact Angle Meter S-150). The water repellency of the water absorption prevention material was evaluated from the obtained contact angle based on the following evaluation criteria. The evaluation results are shown in Table 2.
(Evaluation Criteria for Water Repellency)
◯ (very good): The contact angle of the water droplet is 120° or more. △ (good): The contact angle of the water droplet is 80° or more and less than 120°. × (bad): No water droplets are formed and the water is immediately absorbed into the test piece having the coating surface for evaluation.

(Test Example 3: Rust inhibitor penetration and retention)
Mortar near the rebar of the salt-containing specimen for which rust prevention was evaluated in Test Example 1 was pulverized to obtain mortar powder. A solvent (methanol) with good affinity for the rust inhibitor was added to the mortar powder and thoroughly stirred. The rust inhibitor was eluted from the mortar powder. The obtained eluate was measured using a gas chromatograph mass spectrometer (Shimadzu Corporation's "GCMS-QP5000") to confirm the presence of the rust inhibitor. From the measurement results, the rust inhibitor penetration and retention of the water absorption prevention material was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 2.
(Evaluation criteria for anti-rust agent penetration and retention)
○ (Very good): The rust inhibitor is clearly detected (the S/N ratio of the peak derived from the rust inhibitor is 2 or more)
△ (Good): Rust inhibitor is slightly detected (S/N ratio of peak derived from rust inhibitor is 1 or more and less than 2)
× (bad): No rust inhibitor was detected (the S/N ratio of the peak derived from the rust inhibitor is less than 1)

(comprehensive evaluation)
The rust prevention (two-point judgment based on the presence or absence of salt), water repellency, and rust inhibitor penetration and retention (four-point evaluation results) were evaluated comprehensively based on the following evaluation criteria. The comprehensive evaluation results are shown in Table 2.
(Evaluation criteria for overall evaluation)
◎ (Very good): The evaluation results of rust prevention, water repellency and rust inhibitor penetration and retention are all ○ ○ (Good): None of the evaluation results of rust prevention, water repellency and rust inhibitor penetration and retention are ×, and one or two of them are △ × (Bad): At least one of the evaluation results of rust prevention, water repellency and rust inhibitor penetration and retention is ×, or at least three are △

(Examples 2 to 14 and Comparative Examples 3 to 6)
Furthermore, the following compounds were prepared as components (B) to (C).
Component (A) Aminoalkoxysilane ("KBE-903" manufactured by Shin-Etsu Chemical Co., Ltd.)
(B) Thixotropic agent: Organic thixotropic agent: Hydrogenated castor oil type (as shown in Table 1), "ASA T-20" manufactured by Ito Oil Mills, Ltd.
Organic thixotropic agent: polyethylene oxide type (as shown in Table 1), "Disparlon 4200-20" manufactured by Kusumoto Chemicals Co., Ltd.
(C) Rust inhibitor - "VERZONE Crystal #130" manufactured by Yamato Chemical Laboratory Co., Ltd. (listed as #130 in Table 1); other acid amine salts, rust inhibitor content 100% by mass, mass loss rate 98%, volatility (quick drying)
"VERZONE Crystal #150" manufactured by Yamato Chemical Laboratory Co., Ltd. (listed as #150 in Table 1); amine nitrite salts, rust inhibitor content 100% by mass, mass loss rate 24%, evaporation (slow drying)
"VERZONE Crystal #260" manufactured by Yamato Chemical Laboratory Co., Ltd. (listed as #260 in Table 1); amine nitrite salts, rust inhibitor content 100% by mass, mass loss rate 2.4%, evaporation (slow drying)

Next, the water-absorption prevention materials of Examples 2 to 14 and Comparative Examples 3 to 8 were prepared in the same manner as in Example 1, except that the composition was changed to that shown in Table 1. In addition, among the compositions shown in Table 1, (C) indicates the amount of the active ingredient (i.e., slow-drying volatile rust inhibitor) contained in the commercially available product. Please note that some commercially available products are distributed in the form of a mixture (the content (unit: mass %) of the rust inhibitor, which is the active ingredient, is listed separately). The mass of the target component is the target. For example, when a certain component is commercially available in the form of a mixture, the composition in Table 1 indicates the mass of the target component, not the mass of the mixture. Note that volatile rust inhibitors #130, #150 and #260 are distributed on the market in solid form with 100 mass % of the active ingredient, but from the viewpoint of improving the solubility in the water-absorption prevention material to be prepared, the volatile rust inhibitor was added to a solvent (specifically, an alcohol-based solvent) to make it 30 mass % to prepare a solution in advance. It was then mixed with the other components (A) and (B) to prepare the water absorption prevention material.

In the same manner as in Example 1, the rust prevention properties, water repellency, rust inhibitor penetration and retention, and overall evaluation were performed for Examples 2 to 14 and Comparative Examples 3 to 8. The evaluation results are shown in Table 2.

The water absorption prevention materials of Examples 1 to 14 contained (A) an alkylalkoxysilane, (B) a thixotropic agent, and (C) a slow-drying volatile rust inhibitor, as shown in Table 1. In other words, the water absorption prevention materials of Examples 1 to 14 were water absorption prevention materials that fell within the scope of the invention according to claim 1.
As shown in Table 2, the water absorption prevention materials of Examples 1 to 14 were judged to have a comprehensive evaluation of either ⊚ (very good) or ◯ (good).

As shown in Table 1, the water absorption prevention materials of Comparative Examples 1 to 8 lacked any one of (A) alkylalkoxysilane, (B) thixotropic agent, and (C) slow-drying volatile rust inhibitor. In other words, the water absorption prevention materials of Comparative Examples 1 to 8 were water absorption prevention materials outside the scope of the invention according to claim 1. In detail, the water absorption prevention materials of Comparative Examples 1 and 3 did not contain (C). The water absorption prevention material of Comparative Example 2 did not contain (A) and (B). The water absorption prevention material of Comparative Example 4 did not contain (A). The water absorption prevention materials of Comparative Examples 5 to 6 did not contain (C). The water absorption prevention materials of Comparative Examples 7 to 8 contained a fast-drying volatile rust inhibitor and did not contain (C).
As shown in Table 2, the water absorption prevention materials of Comparative Examples 1 to 8 were all judged to be × (bad) in the overall evaluation.

Therefore, it is clear that the water absorption prevention material included in the scope of the invention according to claim 1 has superior rust prevention properties, water repellency, and rust inhibitor penetration and retention properties compared to water absorption prevention materials not included in the scope of the invention according to claim 1. This is believed to enable more sufficient inhibition of corrosion of metals such as reinforcing bars.

From the above, it has been found that the water-absorption prevention material according to the present invention, compared to water-absorption prevention materials not corresponding to the present invention, is able to suppress further penetration of external deterioration factors into civil engineering and construction materials, and is also able to more fully suppress corrosion of metals such as reinforcing bars, even in civil engineering and construction materials that already contain inherent deterioration factors.

(Content of (A), (B) and (C))
The contents of (A), (B) and (C) are shown in Table 3. These contents (unit: mass%) indicate the ratio to the total mass of (A), (B) and (C).

As shown in Tables 2 and 3, when the contents of (A), (B) and (C) were 87-93 mass%, 5.6-5.9 mass% and 1.5-7.0 mass%, respectively (Examples 4-7), the evaluation results for rust prevention and rust inhibitor penetration and retention were all ○ (very good). When the contents of (A), (B) and (C) were 90-94 mass%, 5.7-6.0 mass% and 0.03-4.3 mass%, respectively (Examples 2-5), the evaluation results for water repellency were all ○ (very good). When the contents of (A), (B) and (C) were 90-93 mass%, 5.7-5.9 mass% and 1.5-4.3 mass%, respectively (Examples 4-5), the evaluation results for overall evaluation were all ◎ (very good).

The present invention relates to a water absorption prevention material for civil engineering and building materials used to cover the outer surface of civil engineering and building materials, and in particular to an effective technology that makes it possible to more fully suppress corrosion of metals such as reinforcing bars while suppressing further penetration into existing civil engineering and building materials.

Claims (6)

A water absorption prevention material for civil engineering and building materials, comprising (A) an alkylalkoxysilane and/or a condensate thereof, and (B) a thixotropic agent,
The water absorption prevention material contains, in addition to the (A) alkylalkoxysilane and/or its condensate and the (B) thixotropic agent, (C) a slow-drying volatile rust inhibitor ,
The slow-drying volatile rust inhibitor has a mass loss rate of more than 0% and not more than 25%, and the mass loss rate is calculated from the amount of mass change of the slow-drying volatile rust inhibitor when the slow-drying volatile rust inhibitor is heated at 25°C and 1 atmospheric pressure using a differential heat/thermogravimetry device along a temperature profile (starting temperature 25°C → heating (heating rate 10°C/min) → holding (after reaching 60°C, holding at 60°C for 120 minutes)). Water absorption prevention material for civil engineering and building materials. The water absorption prevention material for civil engineering and construction materials according to claim 1, wherein the content of the (C) slow-drying volatile rust inhibitor is 0.03% to 6% by mass relative to 100% by mass of the total mass of the (A) alkylalkoxysilane and/or its condensate, and the (B) thixotropic agent. The water absorption prevention material for civil engineering and construction materials according to claim 1 or 2, wherein the (B) thixotropic agent is an organic thixotropic agent. The water absorption prevention material for civil engineering and building materials according to claim 1 or 2, wherein the (B) thixotropic agent is at least one organic thixotropic agent selected from the group consisting of hydrogenated castor oil-based, amide wax-based, oxidized polyethylene-based, polyolefin-based, sulfate-based, dimer acid ester-based, polycarboxylic acid-based, and vegetable oil-based thixotropic agents. The water absorption prevention material for civil engineering and construction materials according to claim 1 or 2, further comprising (D) a polar solvent. (E) The water absorption prevention material for civil engineering and construction materials according to claim 1 or 2, further comprising hydrophobic silica powder.