JPH05194879A - Photocurable coating composition for concrete formwork plywood - Google Patents

Abstract

(57) [Summary] [Purpose] It has excellent light resistance that can withstand the ultraviolet rays in the sun's rays. [Structure] An acrylic oligomer which is a reaction product of a triisocyanate of an isocyanuric acid derivative and an acrylic acid derivative having a functional group capable of reacting with acrylic acid or an isocyanate group is contained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for the surface treatment of wooden plywood for concrete formwork (plywood for formwork) used when constructing structures by concrete casting in the fields of civil engineering and construction. The present invention relates to a photocurable coating composition having good light resistance.

[0002]

2. Description of the Related Art As is well known, if plywood for formwork is used as a formwork without being surface-treated, fresh concrete will penetrate from the surface of the plywood into the interior, resulting in significant damage to the plywood. It cannot be used after only using it. Also, when the concrete hardens and the mold is removed, the concrete adheres firmly to the plywood surface, resulting in poor releasability and the plywood surface being partially peeled off the concrete. Reuse becomes difficult. In addition, various forms of plywood for formwork are made of various South Sea materials such as capole, merante, durian, etc.If a material containing a large amount of tar and lignin is used, the concrete surface will be contaminated and the concrete surface will be contaminated. -Inhibits the curing reaction.

Therefore, the plywood for molds has conventionally been subjected to a surface treatment, which is most commonly applied by coating with a solvent type acrylic or urethane type synthetic resin paint.

However, when a solvent-type synthetic resin coating material is mass-produced on a plywood for molds, it takes a long time to dry in a natural state such as moving or transporting by natural drying. Further, since these paints contain solvents such as ketones, esters, aromatic hydrocarbons, etc., there are problems of deterioration of the coating work environment due to solvent odor and air pollution around the factory.

Therefore, in recent years, as a surface treatment of plywood for molds, it has been put to practical use to apply a photocurable composition which cures in an extremely short time, for example, in seconds.

As a conventional structure of such a photocurable coating composition, there are urethane acrylate and epoxy acrylate.
30-80% of acrylic oligomer such as G., 20-70% of reactive diluent for adjusting viscosity suitable for coating, 1-10% of photosensitizer, trace amount of defoaming agent and coating surface modifier. What is prepared by uniformly mixing is used. Such compositions are widely used for surface treatment of PVC flooring materials, furniture, plywood for building materials and the like.

[0007]

However, when a concrete is placed at an outdoor construction site using the plywood for a formwork coated with the above-mentioned conventional photocurable coating composition, it is included in the sunlight. The coating film is deteriorated by the generated ultraviolet rays. Therefore, cracks occur in the coating film on the surface of the plywood, or low molecular weight organic acid compounds are generated from the coating film to hinder the curing reaction of the concrete, and the concrete surface exhibits a powder blown state.

[0008] Therefore, an object of the present invention is to provide a photocurable coating composition for a concrete mold having excellent light resistance capable of withstanding ultraviolet rays in sunlight. Then, in forming a coating film, a sealing paint is applied to the plywood for formwork to make it smooth, and then this photocurable coating composition is applied, and then a cured coating film is formed by irradiating actinic rays. It is a thing.

[0009]

The first basic feature of the photocurable coating composition for a concrete mold according to the present invention is the triisocyanate of an isocyanuric acid derivative and an acrylic acid or an isocyanate group. It contains an acrylic oligomer which is a reaction product with an acrylic acid derivative having a functional group capable of reacting with.

A second feature is that the triisocyanate of the above isocyanuric acid derivative is a trimer of tolylene diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate. is there.

These isocyanuric acid derivatives are represented by the following chemical formula.

[0012]

[Chemical 1]

[0013]

[Chemical 2] The polyisocyanate having at least one of these isocyanuric acids can be obtained by heating the diisocyanate compound in the presence of a catalyst or in the absence of a catalyst for isocyanuric conversion.

In this case, at first, a polyisocyanate having one isocyanuric acid is formed, but subsequently, a polyisocyanate having two isocyanuric acid is formed.
It is very difficult to synthesize only a polyisocyanate having one isocyanuric ring, and it contains a small amount of a polyisocyanate having two isocyanuric rings.

A third characteristic is the above-mentioned isocyanate.
Wherein the derivative of acrylic acid having a functional group capable of reacting with a hydroxy group is selected from 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and 2-hydroxybutyl acrylate. It is in.

These acrylic acid derivatives are represented by the following general formula.

[0017]

[Chemical 3] The acrylic oligomer can be synthesized by a usual method using the production raw materials described in the second and third characteristics as starting materials. For example, one kind of the acrylic acid derivative described in the third feature, an inert solvent such as toluene, xylene, or methyl ethyl ketone, a trace amount of a reaction initiator, and a polymerization inhibitor are uniformly mixed, and then heated to 60 to 80 ° C. And second
One of the isocyanuric acid derivative triisocyanates described as the characteristics of 1. is gradually added, and then 60 to 80
React at 3 ° C. for 3 to 10 hours. After completion of the reaction, the desired acrylic oligomer is obtained by heating under reduced pressure to remove the inactive solvent.

The photocurable composition can be prepared by mixing 20 to 80% of the acrylic oligomer thus obtained, 10 to 80% of the reactive diluent and 1 to 10% of the photosensitizer. it can. If the acrylic oligomer is less than 20%, the effect is small, and if it exceeds 80%, the viscosity of the composition is too high and it is difficult to coat with an ordinary coating machine. Therefore, the desirable content of the acrylic oligomer is 30 to 60%.

This acrylic oligomer may be used in combination with other acrylic oligomers such as urethane acrylate, epoxy acrylate and ester acrylate, as long as the light resistance does not deteriorate.

Examples of the reactive diluent for decreasing viscosity that can be used in the photocurable coating composition are 2-ethylhexyl acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, ethoxyethoxyethyl acrylate. -, Mono-functional monomers such as butoxyethyl acrylate, methyl triglycol acrylate, isobonyl acrylate, isodecyl acrylate, 1,4 butanediol diacrylate, 1,6 Hexanediol diacrylate, neopentyl glycol diacrylate,
Bifunctional monomers such as diethylene glycol diacrylate, polyethylene glycol diacrylate, trimethylol propane triacrylate, pentaerythritol
A polyfunctional monomer such as lutriacrylate and dipentaerythritol hexaacrylate can be used. These acrylic monomers may be used alone or in combination of several kinds.

As the photosensitizer, benzoin, benzoin ethyl ether, benzoin isopropyl ether,
Bunzophenone, benzyl dimethyl ketal, etc. can be used alone or in combination of several kinds.

If necessary, a defoaming agent, a coating additive such as a leveling agent, an organic solvent for adjusting the viscosity, or an isocyanate resin for improving the adhesion of the cured coating film may be added.

Then, the coating film forming step using the coating composition of the present invention will be explained. First, the sealing paint is applied to the formwork plywood to make it smooth, and then the film is photocured. A water-based coating composition. As the coating means, air spray, airless spray, spraying methods such as electrostatic coating, and automatic coating methods such as roll coater and cart coater can be used.

The actinic ray for curing the coating film of the photocurable coating composition may be an actinic ray having a wavelength in the range of 185 to 500 mμ. Examples of the actinic ray source include sunlight, a mercury lamp, Examples of the actinic radiation source used for curing ordinary photocurable coating compositions include carbon arc lamps, xenon lamps, and mercury lamps. Desirably, an artificial light source such as a medium-pressure mercury lamp or a high-pressure mercury lamp, which emits a large amount of actinic light of 200 to 365 mμ, is desirable because of the short-time curing and the toughness of the cured coating film.

[0025]

INDUSTRIAL APPLICABILITY The present invention is suitable for surface treatment of plywood for formwork, and when the plywood for formwork is used outdoors for concrete casting, it is sufficiently effective against ultraviolet rays contained in sunlight. The durability is satisfied, so that the cast concrete surface can be finished smoothly and beautifully.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 170 g of u-hydroxyethyl acrylate, 65 g of toluene, and 0.5 g of dibutyltin dilaurate were placed in a reaction vessel having a capacity of 1 liter equipped with a stirrer, a dropping funnel, a condenser, and a thermometer. 04 g, hydroquinone methyl ether 0.0
2 g was added and the temperature was raised to 70 ° C. with stirring. Thereafter, while maintaining the liquid temperature at 70 ° C., a mixed liquid of 276 g of hexamethylene diisocyanate trimer (Coronate HX, trade name of Nippon Polyurethane Industry Co., Ltd.) and 65 g of toluene was added.
After dropwise addition for 4 hours, the reaction was carried out for 4 hours until the infrared absorption spectrum of the isocyanate disappeared.

After completion of the reaction, the solvent was removed while heating under reduced pressure to obtain a reaction product having a solid content of 100%. The acrylic oligomer thus obtained has a viscosity of 520 at 65 ° C.
It was a pale yellow liquid of 0 centipoise.

A photocurable composition was prepared by uniformly mixing 150 g of this acrylic oligomer, 60 g of phenoxyethyl acrylate, 60 g of trimethylolpropane triacrylate, and 12 g of benzyl dimethyl ketal.

Example 2 In the same manner as in Example 1, 2-hydroxypropyl acrylate was prepared.
And a hexamethylene diisocyanate trimer was used to obtain a 100% solids reaction product. The acrylic oligomer thus obtained was a pale yellow liquid having a viscosity at 65 ° C. of 3300 centipoise.

150 g of this acrylic oligomer, 60 g of 2-ethylhexyl acrylate, pentaerythritol
A photocurable composition was prepared by uniformly mixing 60 g of lutriacrylate and 12 g of benzyl dimethyl ketal.

Example 3 2-hydroxyethyl acrylate was prepared in the same manner as in Example 1.
And tolylene diisocyanate trimer (Coronet 2
031 (trade name of Nippon Polyurethane Industry Co., Ltd.)
A 0% solids reaction product was obtained. The acrylic oligomer thus obtained was a pale yellow liquid having a viscosity at 65 ° C. of 3200 centipoise.

This acrylic oligomer-150 g, 1,4
-Butanediole diacrylate 60 g, trimethylo-
A photo-curable composition was prepared by uniformly mixing 60 g of propane triacrylate and 15 g of benzoin isopropyl ether.

Example 4 2-hydroxybutyl acrylate was prepared in the same manner as in Example 1.
A reaction product of 100% solids was obtained by using a trimer of bisphenol and isophorone diisocyanate (Desmodur Z-4370, trade name of Sumitomo Bayer Urethane). The acrylic oligomer thus obtained has a viscosity of 1100 at 60 ° C.
It was a pale yellow liquid of 0 centipoise.

A photocurable composition was prepared by uniformly mixing 150 g of this acrylic oligomer, 60 g of ethoxyethoxyethyl acrylate, 60 g of pentaerythritol triacrylate, and 15 g of benzoin isopropyl ether.

Comparative Example 1 In the same reaction vessel as in Example 1, 116 g of 2-hydroxyethyl acrylate and 0.14 of dibutyltin dilaurate were added.
g and 0.02 g of hydroquinone monomethyl ether were added, and the temperature was raised to 60 ° C. with stirring. Then, while maintaining the liquid temperature at 60 ° C, 2,4 tolylene diisocyanate-
(90 g) was added dropwise over 2 hours, and the temperature was raised to 70 ° C. after the addition was completed, and the reaction was allowed to proceed for 6 hours until the infrared absorption spectrum of the isocyanate disappeared. The 100% solids acrylic oligomer thus obtained had a viscosity of 810 at 25 ° C.
It was a pale yellow liquid of 0 centipoise.

150 g of this acrylic oligomer, 2-
A photocurable composition was prepared by uniformly mixing 60 g of hydroxyethyl acrylate, 60 g of trimethylolpropane triacrylate, and 12 g of benzyl dimethyl ketal.

Comparative Example 2 In the same reaction vessel as in Example 1, 250 g of isophorone diisocyanate and polyethylene glycol (molecular weight 40
0) 260 g was added, the temperature was raised to 80 ° C. with stirring, and the reaction was carried out for 3 hours. To the obtained reaction product, 0.02 g of hydroquinone monoethyl ether and 116 g of 2-hydroxyethyl acrylate were added, and the reaction temperature was 80 ° C.
Reacted for hours. The 100% solids acrylic oligomer thus obtained was a pale yellow liquid with a viscosity at 60 ° C. of 2100 centipoise.

150 g of this acrylic oligomer, 60 g of phenoxyethyl acrylate, 60 g of pentaerythritol triacrylate, benzoin isopropyl ether
A photocurable composition was prepared by uniformly mixing 15 g of tellurium.

Experimental Example A photocurable composition prepared in Examples 1 to 4 and Comparative Examples 1 and 2 was rolled on a concrete form plywood which was smoothed by coating a solvent type acrylic urethane type sealing agent. After coating with a coater to a film thickness of 30 to 40 μm, it was irradiated with an 80 w / cm mercury lamp for 6 seconds to be cured. 24 at room temperature
After being left for a period of time, a 30 × 30 cm size test plate was cut out and exposed to sunlight for 2 months outdoors.

After 2 months, a box having a length, width and height of 30 cm is made so that the treated surface coated with the photocurable composition is the inside, and 100 volume parts of Portland cement and 300 volume of fine aggregate are placed therein. Parts, and 90 parts by volume of water were charged into the kneaded raw concrete.

After the test plate was left for 4 days, the test plate was removed and the surface of the molding concrete was examined. The results are shown in the following table.

[0043]

[Table 1] As is clear from the table, even if the formwork plywood coated with the composition of the present invention is exposed to sunlight for 2 months, cracks due to coating deterioration and formation of a low molecular weight organic acid compound on the concrete surface are caused. There was no inhibition of the curing reaction and the light resistance was good.

Claims (3)

[Claims] 1. A concrete product containing an acrylic oligomer which is a reaction product of a triisocyanate of an isocyanuric acid derivative and an acrylic acid derivative having a functional group capable of reacting with acrylic acid or an isocyanato group. -G Photocurable coating composition for formwork plywood. 2. The isocyanuric acid derivative triisocyanate according to claim 1, wherein the triisocyanate is tolylene diisocyanate.
A photocurable coating composition for concrete form plywood, which is a trimer of hexamethylene diisocyanate and isophorone diisocyanate. 3. The derivative of acrylic acid having a functional group capable of reacting with an isocyanate group according to claim 1,
Photocurable coating composition for concrete form plywood, which is hydroxyethyl acrylate, 2-hydroxypropyl acrylate, or 2-hydroxybutyl acrylate