JPH0349312B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the field of civil engineering and construction, and in particular to a primer for maintenance painting of concrete buildings, and it relates to a primer for maintenance painting of concrete buildings, and is applicable to wet concrete, for which no adhesion could be expected until now. Adheres extremely strongly to surfaces,
The present invention relates to a primer suitable for concrete paint that has practically sufficient adhesion.

Therefore, the purpose of the present invention is to provide a primer that has excellent adhesion to wet concrete or aged concrete, prevent deterioration of concrete structures, establish a reliable coating system, and improve the aesthetic appearance of concrete structures. The aim is to bring about improvements in

[Conventional technology]

At present, emulsion-type coatings are mainly used for concrete coatings due to their ease of formulation and application, but they have sufficient adhesion and hardness for practical use, stain resistance, and protection against salt damage. , especially if the concrete contains moisture.
It is no exaggeration to say that there are currently virtually no paints that can maintain these properties even when wet.

[Problem that the invention seeks to solve]

Concrete, unlike metal, is a type of porous material and actually has countless cracks. Therefore, paints for this purpose are required to have the ability to follow pores and cracks, and if they also need to serve the purpose of preventing salt damage, they must have the ability to prevent the intrusion of chlorine ions, moisture, oxygen, etc. Must be.

Another problem is that the properties of the materials are different between the surface of newly poured concrete and the surface of aged concrete, making it difficult to achieve good paint adhesion, especially when repairing old concrete. There are many things like that.

In this way, the present invention can coat even concrete with pores and cracks with good followability and prevent the intrusion of moisture, oxygen, and other substances, and it also adheres well to old concrete with deteriorated surface that is the target of repair. The aim is to provide a primer with good properties.

[Means and actions for solving problems]

Adheres well to concrete surfaces, especially wet surfaces,
As a result of various studies in order to form a coating film with sufficient durability, the present inventors discovered that the decisive factor is the quality of the primer that impregnates the concrete surface and firmly adheres to the concrete. , which is a defect, and the selection will decisively influence the success or failure of the concrete paint.

Therefore, the present inventors investigated various primer compositions to obtain reliable adhesion, and found that
A primer mainly consisting of an unsaturated isocyanate having a (meth)acryloyl group and an isocyanate group via a urethane bond, and if necessary, a polymerizable monomer and a polymer dissolved in the polymerizable monomer. Primers formulated with coalescing and hardening agents have been found to be suitable for these purposes.

Apply these primers to the concrete surface,
The present inventors have discovered that by impregnating concrete, bonding isocyanate groups and concrete components, and polymerizing unsaturated groups at the same time, it is possible to obtain a coating film that adheres extremely strongly to concrete, and has completed the present invention. .

The unsaturated isocyanate compound used in the present invention has a (meth)acryloyl group and an isocyanate group in the molecule via a urethane bond, and typically consists of acrylic acid or methacrylic acid and a monoepoxy compound. Examples include unsaturated isocyanates which have a (meth)acryloyl group and an isocyanate group in one molecule via urethane by reacting an unsaturated alcohol obtained by the reaction with a polyvalent isocyanate.

An example is shown by the following reaction.

In the production of this type of unsaturated isocyanate compound, the reaction molar ratio of unsaturated alcohol and diisocyanate does not necessarily have to be equal in amount to hydroxyl groups and isocyanate groups, and the presence of free diisocyanate is allowed.

Although it is convenient to carry out the reaction in a solvent or monomer and use it as such,
It is not impossible to synthesize without solvent.

Suitable examples of unsaturated alcohols used in the synthesis of unsaturated isocyanates include 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

In addition, examples of polyvalent isocyanates include 2,4 tolylene diisocyanate, a mixture of 2,4 tolylene diisocyanate and 2,6 tolylene diisocyanate, tolydine diisocyanate, diphenylmethane diisocyanate, and paraphenyl diisocyanate. diisocyanate, 1,5-naphthylene diisocyanate, 1,6 hexamethylene diisocyanate,
Isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate are used.

The primer of the present invention can be impregnated into concrete or cement-based building materials with unsaturated isocyanate alone, but preferably,
By applying a radical-curing resin on top of it and curing it, the unsaturated groups of the primer and the topcoat resin copolymerize, and finally the impregnated resin hardens to achieve the desired purpose. be.

Furthermore, in order to expand the effects of the present invention and to fully achieve the purpose no matter what kind of paint is used as the top coat, a radical generating catalyst may be used in combination as necessary, and (meth)acryloyl groups may be added in the molecule. It is possible to take measures such as using a mixture of a polymerizable monomer copolymerizable with an unsaturated isocyanate having an isocyanate group, or dissolving the polymer in the polymerizable monomer.

The unsaturated isocyanates of this invention can be cured by various means. For example, the radical generator may be an azo compound, but the adhesion tends to vary. Photo-reaction initiators show a similar tendency, and are practical when exposed to sunlight, but adhesion becomes insufficient on cloudy days or in areas not exposed to light.

As the curing agent of the present invention, a redox system using an organic peroxide is suitable. Examples of these include (a) acyl peroxide - aromatic tertiary amines, (b) hydroperoxide - organic acid salts of vanadium, cobalt, copper, manganese, or chelate compounds, (c) ketone peroxide - Examples include organic acid salts or chelate compounds of cobalt and vanadium, and (c) is particularly useful when used in combination with a small amount of styrene.

Examples of organic peroxides include the following types.

() Ketone peroxides Methyl ethyl ketone peroxide, cyclohexanone peroxide, methyl acetoacetate peroxide, () Hydroperoxides Cumene hydroperoxide, paramenthane hydroperoxide, () Diacyl peroxides Lauroyl peroxide, Benzoyl peroxide , methalyl peroxide, () Peroxy esters t-butyl peroxy pivalate, t-butyl peroxy 2-ethyl hexanate, t-butyl peroxy benzoate, these can be used alone, but if necessary Mixed use is also possible. However, ketone peroxides and hydroperoxides react with isocyanate groups, rapidly gelling, and sometimes foaming, making it difficult to use them in combination with unsaturated isocyanates and relying on spray painting from separate nozzles. It turns out.

Since diacyl peroxide does not exhibit this phenomenon, any coating system can be employed.

The amount of organic peroxide used is 0.2 to 5 parts by weight based on 100 parts by weight of the unsaturated isocyanate and the polymerizable monomer, and a suitable amount is 0.5 to 3 parts by weight.

The polymerizable monomer used in the present invention has the effect of improving adhesion and expanding the stress surface, and is a type that can be copolymerized with the unsaturated bond of unsaturated isocyanate, specifically the (meth)acryloyl group. If so, it is available. Examples of these include the following types:

Styrene, vinyltoluene, chlorostyrene,
Methacrylic acid esters (methyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate,
cyclohexyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, etc.), acrylic acid esters (methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, phenoxyethyl acrylate, cyclohexyl acrylate, trimethylolpropane triacrylate, etc.), Acrylonitrile, vinylpyrrolidone.

The proportion of these polymerizable monomers to be used is not particularly limited, but is preferably from 5 parts to 200 parts per 100 parts by weight of the unsaturated isocyanate.

This does not mean that using more than 200 parts cannot be used, but there is a tendency for the viscosity to decrease and the effectiveness to decrease somewhat. Moreover, if it is less than 5 parts, there is little point in adding it.

Furthermore, it may be useful to dissolve and use a polymer soluble in the polymerizable monomer in combination with the polymerizable monomer to improve adhesion. For example, an appropriate amount of unsaturated isocyanate is mixed with so-called acrylic syrup, which is made by dissolving polymethyl methacrylate in methyl methacrylate.
Paint films cured with radical-generating hardeners adhere extremely well to painted concrete surfaces.

The polymer used here is not particularly limited as long as it is of a type that can be dissolved in the monomer. Examples of these include polymethyl methacrylate, polystyrene, polyvinyl acetate, copolymer rubber of butyl acrylate and acrylonitrile, chlorosulfonated polyethylene, thermoplastic amorphous polyester, and ethylene-vinyl acetate copolymer. can give.

After applying the primer according to the present invention to concrete, it can be further coated with a desired paint, and has good adhesion with the top paint.

It goes without saying that the primer according to the present invention can also be used in combination with fillers, colorants, reinforcing materials, etc., if necessary.

〔Example〕

Next, examples will be shown below to help understand the present invention.

Example 1 Synthesis of unsaturated isocyanate (A) 82 g of methyl methacrylate, 174 g of 2,4-tolylene diisocyanate, and methyl paraben were placed in a separable flask equipped with a stirrer, a reflux condenser, a thermometer with a gas inlet tube, and a dropping funnel. 0.05 g of zoquinone was charged, and 144 g of 2-hydroxypropyl methacrylate was added dropwise in dry air over a period of 30 minutes at a temperature of 60°C.

After the dropwise addition was completed, the reaction was carried out at the same temperature for 1 hour, then 1.2 g of dibutyltin dilaurate was added, and the reaction was continued for another 1 hour.As a result of infrared analysis, it was found that the isocyanate groups were approximately
60 (%) were judged to have responded. Unsaturated isocyanate (A) (methyl methacrylate solution)
was obtained as a pale yellow liquid.

Adhesion test 30cm x 30 pieces immersed in water at room temperature for 3 days
A concrete plate measuring cm x 5 cm was lifted out of the water.
After leaving it at room temperature for 30 minutes, wipe the surface with a cotton cloth. Immediately onto this surface, a mixture of 100 parts by weight of unsaturated isocyanate (A) (methyl methacrylate solution), 4 parts by weight of benzoyl peroxide (50% powder), and 0.2 parts by weight of dimethylaniline was applied with a brush at a rate of 50 g/m ² . , I left it like that for a day and night.

Next, a paste-like paint that is viscous at room temperature, made by adding 0.3 parts of dimethylaniline to 100 parts of T-Coat (product name: thermosetting resin for acrylic intermediate coating) manufactured by Showa Kobunshi Co., Ltd., was applied to a thickness of 2 mm. Add a spatula to the
Cover the surface with polyethylene terephthalate film and allow to cure overnight.

A tensile adhesion test using an elcometer showed 30 to 40 kg (5 measured values), and all of them broke after digging into the concrete surface by 1 to 2 mm.

Example 2 Synthesis of unsaturated isocyanate (B) 134 g of phenoxyethyl methacrylate, 222 g of isophorone diisocyanate, para 0.05 g of benzoquinone and 0.5 g of dibutyltin dilaurate were charged, and 144 g of 2-hydroxypropyl methacrylate was added dropwise at a temperature of 70°C in a stream of dry air. After the dropwise addition was completed, the reaction was carried out at 70 to 75°C for 3 hours, and as a result of infrared analysis, it was estimated that the free isocyanate groups were approximately 46 (%).

Unsaturated isocyanate (B) (phenoxyethyl methacrylate solution) was obtained as a pale yellowish brown liquid.

Adhesion test Lambda sizing (cement-asbestos building material) manufactured by Showa Denko Kenzai Co., Ltd. was cut into 30 cm pieces and
Soaked in water for a day.

Immediately after pulling up the surface, the surface was wiped with a dry cloth, and the following formulation was immediately applied at a concentration of 100 g/m ² and left overnight to cure.

Unsaturated isocyanate (B) (phenoxyethyl methacrylate solution) 100 parts by weight Acrylic syrup containing approximately 32% polymethyl methacrylate (polymethyl methacrylate 32% methyl methacrylate monomer 68%) 65 parts by weight Benzoyl peroxide 5 parts by weight Dimethyl In a tensile adhesion test using an Elcometer using 0.3 parts by weight of aniline epoxy resin as an adhesive, the measured values at five locations all showed 25 kg or more, indicating material breakage.

Example 3 Synthesis of unsaturated isocyanate (C) Into a separable flask equipped with a stirrer, a reflux condenser, a thermometer with a gas introduction tube, and a dropping funnel, 174 g of 2,4-tolylene diisocyanate
Prepared 0.05g of methyl parabenzoquinone, 144g of 2-hydroxyethyl methacrylate in dry air
is added dropwise at a temperature of 60°C over a period of 30 minutes.

After the completion of the dropwise addition, the reaction was continued at the same temperature for 1 hour, and then 1.2 g of dibutyltin dilaurate was added, and the reaction was continued for another 1 hour to obtain unsaturated isocyanate (C) in the form of a pale yellow liquid. As a result of infrared analysis, it was determined that approximately 60 (%) of the isocyanate groups had reacted.

Adhesion Test An adhesion test was conducted in the same manner as in Example 1 using the following mixture. However, the thickness of the brush coating should be 70
g/ ^m2 .

Unsaturated isocyanate compound (C) 100 parts by weight Benzoyl peroxide (50% powder) 3 parts by weight Dimethylaniline 0.2 parts by weight A tensile adhesion test using an elcometer showed 25 to 30 kg (5 measurement ranges). ,
All of the specimens showed a hardened fracture that had penetrated to a depth of 1 to 2 mm from the concrete surface.

Example 4 An adhesion test was conducted in the same manner as in Example 1 using the following mixture. However, the thickness of the brush coating should be 70
g/ ^m2 .

Unsaturated isocyanate compound (C) 100 parts by weight Dimethylaniline 0.2 parts by weight In a tensile adhesion test using an Elcometer, it showed 20 to 25 kg (5 measurement value ranges),
All of the specimens showed a hardened fracture that had penetrated to a depth of 1 to 2 mm from the concrete surface.

〔Effect of the invention〕

The primer according to the present invention is mainly composed of an unsaturated isocyanate compound, and also contains a polymerizable monomer if necessary, so it can be used on concrete with pores and cracks, or concrete whose surface has deteriorated over time. It penetrates well and hardens, and it also adheres well to wet concrete surfaces, forming a coating that prevents moisture and gas from entering. Furthermore, since this primer has good adhesion with the top coat, a desired top coat can be applied thereon, which is useful for preventing deterioration of concrete structures and maintaining the aesthetic appearance.

Claims (1)

[Scope of Claims] 1. An unsaturated isocyanate having a (meth)acryloyl group and an isocyanate group via a urethane bond in the molecule, and optionally a polymerizable monomer, and the polymerizable monomer. A concrete primer containing a polymer and hardening agent that dissolves in water. 2. The concrete primer according to claim 1, which contains an organic peroxide as a hardening agent.