JP2015110715A - Coating agent for concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating agent for concrete imparting water repellency, stain resistance and durability to the surface of a concrete structure.SOLUTION: The main component of a coating agent for concrete is composed by adding a water dispersion type colloidal silica as a vehicle and titanium dioxide having a photocatalytic function to a liquid silicone rubber as a base. The silica particulates of a film formed by applying the coating agent to the surface of concrete penetrate into the fine pores on the concrete surface to polymerize while having a strong adsorption power and thereby, a film-applied concrete has a characteristic such that crack hardly generates. Further, since the silicone rubber includes the polymerized silica, the film has high water repellency and as a result, an antifouling property is improved by the water repellency of the film and also by the self-cleaning operation based on the photocatalyst function of titanium dioxide. Besides, the intrusion of acidic materials into concrete or breakdown of concrete is prevented by the water repellency of the film, and durability is improved. Thereby, the cut-down of social capital input aiming at infrastructure regeneration which will generate in future is expected by the extended service life of concrete accompanying improvement of weatherability or the like.

Description

  The present invention relates to a concrete coating agent that imparts water repellency, stain resistance and durability to the surface of a concrete structure.

A concrete structure has a standard life span of about 50 years, and in recent years, measures for aging of structures built around the post-war reconstruction period have been studied.
Infrastructure consisting of concrete structures such as public facilities, roads, bridges, water and sewage systems, and airports is called “social capital” in the sense that it is necessary to establish society and anyone can use it. The total amount of investment for renewal of social capital due to aging has reached 330 trillion yen, and it is estimated that 8.1 trillion yen per year will be required over the next 50 years. (Reference material “Degraded Infrastructure” written by Yuji Nemoto, published by Nikkei Inc., May 24, 2011, first edition)
Cement, which is the main material of concrete structures, is alkaline and neutralizes by reacting with acidic substances such as carbon dioxide, acid rain, acid fog, and acid exhaust gas in the air. This causes pulverization and cracking of the concrete surface, and when an acidic substance penetrates into the interior from the cracked site, Ca (OH) ₂ which is the main component of cement gradually changes into CaCO ₃ and gradually changes. It will be decomposed and will eventually lead to the destruction of the concrete structure itself. In addition, the problem of so-called “concrete icicles” occurs when calcareous icicles are generated when a solution containing Ca (OH) ₂ flows into the atmosphere. (Reference Material “Acid Rain and Acid Fog” written by Kentaro Murano, published on April 20, 1993, the first edition of Hankabo Co., Ltd.)
Furthermore, coupled with the high water absorption of concrete, it causes freezing and expansion of water attached to the reinforcing bars inside the concrete and rust and corrosion of the reinforcing bars, eventually leading to destruction of the concrete and the structure itself. .

In recent years, corrosion of concrete surfaces caused by viable fungi derived from yellow sand and aeolian dust in the atmosphere and streak pollution caused by dripping containing yellow sand and aeolian dust, so-called rain pollution, has been reported.
In order to solve the above problems, various concrete coating agents have been developed that can reduce the adverse effects of acidic substances by imparting water repellency to the concrete surface (see Patent Document 1).

JP-A-9-12380

  However, the technique disclosed in Patent Document 1 imparts water repellency by fluorine. Since the coating agent containing fluorine has a relatively soft film (low wear resistance), sand in the atmosphere, earth and sand, There is a problem that hard dust such as dust is easily scratched, and it is difficult to remove dirt due to dirt entering the wound, and that the adverse effects of the acidic substances and live bacteria spread from the scratched area. is there.

  In consideration of such problems, an object of the present invention is to provide a coating agent for concrete that imparts water repellency, stain resistance and durability to the surface of a concrete structure.

The concrete coating agent of the present invention contains liquid silicone rubber, water-dispersed colloidal silica, titanium dioxide, and a thickener.
The liquid silicone rubber contains 5 to 25% by weight, the water-dispersed colloidal silica is 10 to 30% by weight, the titanium is 5 to 15% by weight, the thickener is 5 to 15% by weight, and the rest Is characterized by moisture.

The concrete coating agent of the present invention is generally constituted by adding water-dispersed colloidal silica as a vehicle and titanium dioxide having a photocatalytic function to a liquid silicone rubber as a base.
The film formed by applying this coating agent to the concrete surface has the characteristic that cracks are unlikely to occur because fine silica particles penetrate into the fine gaps on the concrete surface and polymerize with a strong adsorption force.
In addition, since the silicone rubber is included in the polymerized silica, the film can have high water repellency, the antifouling property is improved by the water repellency of the film, and the antifouling property by the self-cleaning action based on the photocatalytic function of titanium dioxide. Can be improved.
In addition, the water repellency of the film can prevent the penetration of acidic substances into the concrete and the destruction of the concrete. That is, the durability of the concrete surface can be improved.
Such water repellency, stain resistance and durability can be imparted to, for example, concrete paved roads and concrete bridge surfaces in addition to concrete buildings.
The liquid silicone rubber contains 5 to 25% by weight, the water-dispersed colloidal silica is 10 to 30% by weight, the titanium dioxide is 5 to 15% by weight, the thickener is 5 to 15% by weight, and the rest is moisture. The composition ratio is most preferable from the viewpoint of workability of the coating agent for concrete of the present invention.
In addition, the formation of the film on the concrete surface by the concrete coating agent of the present invention can be performed by using a well-known means such as application using a brush or a roller or spraying with a spray gun.

The figure which compared the concrete pillar (right) which applied the coating agent for concrete of the present invention and the thing which applied general acid weather-resistant paint (left)

Embodiments of the present invention will be described below.
The concrete coating agent of the present invention (hereinafter simply referred to as “coating agent”) comprises at least liquid silicone rubber, water-dispersed colloidal silica, titanium dioxide, and a thickener.

Silicone rubber is contained for imparting water repellency and durability to a film, and refers to a rubber-like one of silicone resins (synthetic resins mainly composed of silicone). Silicone is a general term for an artificial polymer compound having a main skeleton formed by a siloxane bond, and siloxane is a processed product having a silicon and oxygen skeleton and a Si-O-Si bond (siloxane bond). In a weather resistance test (ultraviolet irradiation test) of wood with a silicone rubber film formed on the surface, it was proved that it maintains high water repellency and durability despite the actual exposure amount equivalent to 50 years in Tokyo. Yes.
The liquid silicone rubber refers to a silicone resin that is in the form of a paste or a fluid, ie, a liquid before the curing reaction, and becomes a rubber after curing.
Liquid silicone rubber includes room temperature vulcanization type (RTV) silicone rubber, low temperature vulcanization type (LTV) silicone rubber, and silicone rubber for liquid injection molding (LIM). On the other hand, millable silicone rubber, which is a semi-solid plastic before curing and requires a special device for curing, is not included in the liquid silicone rubber.

Liquid silicone rubber is classified into an ultraviolet curable type, an addition reaction type, and a condensation reaction type according to its curing reaction mechanism.
The UV curable type reacts with radicals by UV irradiation, and the addition reaction type reacts polysiloxanes with unsaturated bonds such as vinyl groups and allyl groups with polysiloxanes with Si-H bonds under a platinum catalyst. In the condensation reaction type, silanol having a Si-OH bond is reacted with a hydrolyzable group-containing silicon compound such as alkoxysilane, acetoxysilane, or oximesilane under a catalyst such as water and a tin compound. .
As the liquid silicone rubber used in the present invention, an ultraviolet curable type is preferably used in consideration of workability at the time of coating work, but an addition reaction type or a condensation reaction type may be used.
As the liquid silicone rubber, for example, WOOD-AID (trade name) manufactured by Shin-Etsu Chemical Co., Ltd., Shirasukon RTV-4086 (trade name) manufactured by Toray Dow Co., Ltd. can be used.
The liquid silicone rubber is preferably contained within a range of 5 to 25% by weight, but is not particularly limited to this range.

Water-dispersed colloidal silica is contained for imparting durability to the coating, and refers to a silica fine particle dispersed in water in a colloidal form.
Examples of the water-dispersed colloidal silica used in the present invention include Snowtex (trade name) series manufactured by Nissan Chemical Industries, Ltd., Adelite (trade name) series manufactured by ADEKA Co., Ltd., and Cataloid (trade name) manufactured by Catalyst Chemical Industries, Ltd. ) Series, Nippon Chemical Industry Co., Ltd. Silica Doll (trade name) series, Clariant Japan Co., Ltd. clebosol (trade name) series, DuPont Ludox (trade name) series, etc. It is not a thing, and you may use 2 or more types together among these.
Silica can increase the hardness of the film when the content is appropriate, and can have smoothness and crack resistance, but if the content is too high, the film becomes too hard and cracks are generated. It can be a cause. Therefore, in the present invention, the silica is preferably 20 to 30% by weight of the entire water-dispersed colloidal silica, and the water-dispersed colloidal silica is preferably contained within the range of 10 to 30% by weight of the entire coating agent. It is not particularly limited to this range.
The silica particle size is preferably in the range of 10 to 20 μm. This allows silica to penetrate into the fine gaps on the concrete surface and polymerizes with strong adhesion, thus preventing cracking of the coating surface and durability of the concrete surface. Can be improved.

Titanium dioxide is contained in order to make the coating agent resistant to contamination using its photocatalytic function.
When a film containing titanium dioxide is irradiated with ultraviolet rays, the titanium dioxide is converted into hydroxyl radicals by the photocatalytic action of moisture in the air or moisture attached to the film surface. A self-cleaning action (contamination resistance) of decomposing and removing dirt such as viable fungi derived from yellow sand and wind dust is obtained. Moreover, since this film also has an antistatic effect due to the photocatalytic function, it can be imparted with contamination resistance also by this function.
Titanium dioxide is preferably contained within a range of 5 to 15% by weight, but is not particularly limited to this range.

The thickener is mainly contained to prevent titanium dioxide from settling or solidifying in the coating agent.
Examples of thickeners include gum arabic, carrageenan, dextrin, gelatin, sodium alginate, methylcellulose, hydroxypropylcellulose, PVA, sodium polyacrylate, guar gum, tamarind gum, xanthan gum, aluminum magnesium silicate, bentonite, laponite and the like. However, the present invention is not limited to these.
The thickener is preferably contained in an amount of 5 to 15% by weight, but is not particularly limited to this range.
Moreover, what is necessary is just to add a water | moisture content suitably other than said each component and to adjust the viscosity of a coating agent.
The coating agent of the present invention combines the water repellency and durability of silicone rubber, the durability of water-dispersed colloidal silica, and the contamination resistance due to the photocatalytic function of titanium dioxide. As a result, infrastructure investment, which is social capital, can be significantly reduced.

なお、水として磁化水（磁気処理水）を使用している。通常の水分子は水素イオン側が正電荷（＋）、酸素イオン側が負電荷（−）の分布をとり棒磁石と同様にふるまっており、ひとつの水分子中の水素原子と他の水分子中の酸素原子とが水素結合で結ばれたクラスターを形成している。通常の水は隙間が多い籠状の構造になっており、これが物質の溶かし易さに繋がり、種々の劣化の原因になっていると考えられている。
磁化水は水分子のクラスターを小さくすることで浸透性が高いと言われているため、磁化水を使用することで本発明のコーティング剤の浸透性も通常の水道水を使用する場合と比較して高く、これがコンクリート表面の劣化防止に寄与する可能性がある。当然のことながら、磁化水ではなく水道水等、容易に入手できる水をコーティング剤に使用してもよい。 Examples of the concrete coating agent of the present invention will be described.
Figure 1 shows a concrete concrete coating applied to the surface of a cylindrical concrete block (right side in the figure) and a typical acidic weather-resistant paint applied as a comparative example (left side in the figure) for 5 months. It shows the state after being exposed to wind and rain outdoors.
As a result of the photocatalytic function of titanium dioxide being applied, the surface to which the coating agent of the present invention is applied has not changed from milky white at the start of the experiment, but the surface to which the general weather-resistant paint is applied is discolored. You can see that
The component ratio of the coating agent in the present example is as follows.

In addition, magnetized water (magnetically treated water) is used as water. Normal water molecules have a distribution of positive charge (+) on the hydrogen ion side and negative charge (-) on the oxygen ion side, and behave in the same way as a bar magnet. The hydrogen atom in one water molecule and the other water molecule A cluster in which oxygen atoms are connected by hydrogen bonds is formed. Ordinary water has a bowl-like structure with many gaps, which leads to ease of dissolution of the substance, and is considered to cause various deterioration.
Since magnetized water is said to have high permeability by reducing the size of water molecule clusters, the permeability of the coating agent of the present invention is higher than that of normal tap water by using magnetized water. This may contribute to prevention of deterioration of the concrete surface. As a matter of course, easily available water such as tap water instead of magnetized water may be used for the coating agent.

実施例１との対比で最も大きく異なるのは水分散型コロイダルシリカとして実施例１ではpH8.5〜9.0の弱アルカリ性のスノーテックスＣを２０％用いていたが、本実施例ではpH9.5〜10.5のよりアルカリ性が強いスノーテックス３０を２５％用いる点である。
このようにアルカリ性を強めることで酸性雨等に起因するコンクリートの中性化を更に抑制し、耐酸性雨対策としてより好適なコンクリート用コーティング剤を得ることができる。 Another embodiment of the concrete coating agent of the present invention will be described.
The component ratio of the coating agent in the present example is as follows.

The largest difference in comparison with Example 1 was that 20% weakly alkaline Snowtex C having a pH of 8.5 to 9.0 was used in Example 1 as water-dispersed colloidal silica. The point is that 25% of Snowtex 30 having a stronger alkalinity of 10.5 is used.
Thus, by strengthening alkalinity, the neutralization of the concrete resulting from acid rain etc. can further be suppressed, and the more suitable coating agent for concrete can be obtained as a measure against acid rain.

The present invention relates to a concrete coating agent capable of imparting water repellency, stain resistance and durability to the surface of a concrete structure, and has industrial applicability.

Claims (2)

  A concrete coating agent comprising liquid silicone rubber, water-dispersed colloidal silica, titanium dioxide, and a thickener. The liquid silicone rubber is 5 to 25 wt%, the water-dispersed colloidal silica is 10 to 30 wt%, the titanium dioxide is 5 to 15 wt%, the thickener is 5 to 15 wt%, and the rest The concrete coating agent according to claim 1, which is moisture.

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