JPH02204572A - Wooden plywood for concrete form and method for treating surface thereof - Google Patents

Abstract

PURPOSE:To enable stacking in a short time after coating, reduce the cost of equipment and improve production efficiency by coating the surface of a material with a photo-setting coating composition of a specific composition and radiating an ultraviolet ray of a specific wave length thereon to carry out hardening in a short time. CONSTITUTION:After being coated with a filling coating composition, the surface of a wooden plywood material is coated with a photo-setting coating composition and an ultraviolet ray is radiated thereon to form a hardened film. The composition of this photo-setting coating composition has a specific ratio of 10-80wt% photo-setting resin having two or more ethylene unsaturated double bond in a molecule, 10-70wt% acrylic monomer, and 1-10wt% photo-sensitizer. As for the ultraviolet ray to be radiated, one having a specific wave length of 185-600 nanometer is used. As for the coating method for the filling and photo-setting coating compositions, a knife coater, a roller coater, and a curtain flow coater are used singly or with a combination of two or more of them.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to wooden plywood for concrete formwork (hereinafter referred to as "plywood for formwork") used when constructing structures by pouring concrete, and This invention relates to a surface treatment method.

(Prior art) As is well known, if plywood for formwork is used without surface treatment, the concrete placement surface will be contaminated by resin, lignin, etc. contained in the wood, and the curing reaction of concrete will be inhibited. It turns out.

Therefore, conventional methods for surface treatment of plywood for formwork have been, for example, applying solvent-based acrylic or urethane-based synthetic resin paints, pasting polyolefin sheets or phenol-impregnated paper, etc. A known method is to form a film by spraying polyolefin resin over a pond and then heating and melting it. Among these, synthetic resin paint is commonly used because it is easy to apply and inexpensive.

(Problem to be solved by the invention) However, when applying synthetic resin paint to the above-mentioned formwork plywood in mass production, it takes a long time to reach a dry state that can be moved and transported by natural drying. , a building with large capacity drying space is required.

Also, drying time can be considerably shortened by forced drying using a hot air drying oven or infrared drying oven, but with acrylic paints
20 minutes, whereas urethane paints require 20 to 60 minutes, which poses problems such as insufficient processing capacity of forced drying equipment and limited production efficiency.

Furthermore, the above-mentioned method of pasting a sheet and method of forming a film by heating and melting have poor workability and are expensive.

Therefore, an object of the present invention is to provide a surface-treated plywood for formwork that can be obtained by coating a photocurable composition that hardens in an extremely short period of time (on the order of seconds), and a surface treatment method for the same. .

(Means for Solving the Problems) The feature of the plywood for formwork of the present invention is that a sealing coating composition is coated on the surface of the wooden plywood material to make it smooth, and a photocurable coating is applied on the coating film. The coating composition is applied and irradiated with actinic light to form a cured coating. This photocurable coating composition contains 10 to 80% by weight of a photocurable resin having two or more ethylenically unsaturated double bonds in one molecule, 10 to 70% by weight of an acrylic monomer, and 1 to 10% by weight of a photosensitizer. % by weight, and is cured by actinic light having a wavelength of 185 to 600 mμ.

The method for surface treatment of plywood for formwork according to the present invention is characterized by a first step of coating the surface of the wooden plywood material with a sealing paint composition to make it smooth, and a step of applying a coating composition to the surface of the wooden plywood material to make it smooth. After applying the curable coating composition, the second step is irradiation with actinic light to form a cured coating film. Another feature is that the coating method for the filler coating composition and the photocurable coating composition is a knife coater, a 90-leaf coater, a curtain flow coater, etc., either alone or in combination of two or more.

Therefore, the features of the present invention will be explained in detail below.

(1) The present invention first applies a filler paint to the surface of the plywood material for formwork, and then dries it at room temperature or by heating to make the surface smooth.9 If the surface smoothness is insufficient, use a wide belt sander or It may be polished with a puff sander or the like.

As the filler paint, solvent-based or water-based filler paints that are normally used to smooth wood surfaces can be used, but it is desirable that the filler has excellent filling properties and chemical resistance.

Particularly suitable sealing paints for the present invention include those having the following compositions.

(a) 5 to 50% non-volatile content of solvent for solvent-soluble acrylic resin having hydroxyl residues, 15 to 70% extender pigments such as calcium carbonate, talc, and clay, titanium white, carbon black, yellow iron oxide, etc. Colored pigment 0.2-30
Toluene diisocyanate is added to the main agent whose main component is %, and toluene diisocyanate is added so that the hydroxyl value: isocyanate equivalent = 1 = 1 before coating.

Diphenylmethane diisocyanate or the like is added as a curing agent. If necessary, an antifoaming agent, a leveling agent, an anti-settling agent, etc. may be used in combination with the main agent.

(b) An aqueous solution of a water-dispersible or water-soluble acrylic resin containing 5 to 40% calcium carbonate in terms of non-volatile content.

15-70% extender pigments such as talc and clay, 0.2% coloring pigments such as titanium white, carbon black, yellow iron oxide, etc.
The main component is ~30%.

Surfactant, moisturizing agent, antifoaming agent as necessary.

Punishment may also be used as a defense.

(2) Next, in the present invention, after completing one culm in the above (1), a photocurable coating composition is applied thereon, and the coating film is cured by irradiation with actinic light.

The photocurable coating composition contains 10 to 80% by weight of a photocurable resin having two or more ethylenically unsaturated double bonds in one molecule.
, 10-60% by weight of acrylic monomer for viscosity adjustment
, and 1 to 10% by weight of a photosensitizer.

As the photocurable resin, conventionally known urethane acrylate, epoxy acrylate, polyester acrylate, etc. can be used. However, the acid value of the resin is 20KOH■
/g or more, it will be hydrolyzed by the alkaline content contained in the concrete, causing deterioration of the coating, so it is desirable to keep it below this.

In addition, as the acrylic monomer used to reduce the viscosity, 2-
Ethylphexyl acrylate Phenoxyethyl acrylate, ethoxyethoxyethyl acrylate, butoxyethyl acrylate.

Monofunctional monomers such as 2-droxypropyl acrylate, methyl triglycol acrylate, isodecyl acrylate, 1.4 butanediol diacrylate, 1
．． Trifunctional monomers such as 6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, and tetraethylene glycol diacrylate, trimethylolpropane triacrylate.

Polyfunctional monomers such as pentaerythritol triacrylate and dipentaerythritol hexaacrylate may be used alone or in combination.

Photosensitizers include benzoin, benzoin ethyl ether, and benzoin isopropyl ether.

Benzophenone, benzyl dimethyl ketal, etc. may be used alone or in combination.

If necessary, additives such as antifoaming agents and leveling agents, incyanate resins for improving chemical resistance, or organic solvents for adjusting viscosity may be used in combination.

(3) Methods for applying compositions such as filler paints or photocurable paints include balding, spraying, and roll coaters.
Ordinary coating machines such as , knife coater, curtain flow coater, etc. can be used.

Filling paint fills the conduit part on the surface of the formwork plywood material,
Since the purpose is to make it smooth, it is desirable to use a coating machine with a high sealing effect, such as a natural reverse roll coater, bottom roll coater, or knife coater.
If the smoothness is insufficient even after one coat with these coating machines, you can apply the sealing paint 2 to 3 times in a row.The amount of sealing paint applied is 50 to 150 r. /M is appropriate.

Below this lower limit, the effect of sealing the conduit portion is insufficient and a smooth surface cannot be obtained, while above the upper limit, it is not only uneconomical but also takes a long time to dry and causes problems such as cracks.

It is preferable to apply the photocurable paint using a roll coater or a curtain flow coater. In particular, in order to obtain a smooth surface finish, natural reverse roll coater 1 or curtain 70-coater is suitable. If the paint viscosity is high and curtain flow coating is not possible at room temperature, heat the paint in advance to 50-60°C.
It is also possible to perform curtain 70-coater painting by raising the temperature to . The amount of photocurable paint applied is 20 to 200g/-
is appropriate. Below this lower limit, the surface smoothness and coating performance will not be sufficient, and above the upper limit, it will not only be uneconomical, but also cause problems such as slow curing of the coating and poor curing in the deep parts of the coating. This is not desirable because it occurs.

(4) As a source of actinic light for curing the coating film of the photocurable coating composition, a mercury lamp or a metal halide lamp filled with iron, gallium, or the like can be used. The wavelength of these lamps ranges from 185 to 600 mμ.

Since the coating film is not sufficiently cured at wavelengths other than these, the wavelength is preferably in the range of 250 to 400 mμ.

The irradiation time is preferably in the range of 1 to 10 seconds; below this lower limit, the coating film will be poorly cured, and above the upper limit, over-irradiation will result in discoloration and brittleness of the coating film, which is unsuitable.

(Effects of the Invention) Since the present invention has the above-described configuration, the top coat is cured in a short time, so plywood for formwork can be deposited in a short time after painting, and therefore the area occupied by the painting equipment can be reduced. It is possible to reduce the size of the structure, reduce installation costs, improve production efficiency, and save labor.

(Example) It should be noted that all composition values described in the Examples are shown in parts by weight.

Example 1 300 parts of a water-based polymer prepared by emulsifying and dispersing methyl methacrylate-styrene copolymer in water (150 parts as non-volatile content)
), 200 parts of calcium carbonate.

After uniformly kneading 100 parts of talc using a high-viscosity disper, it was coated on the surface of a plywood material for a 12-inch thick formwork using a natural reverse roll coater.

After drying at 60° C. for 10 minutes, it was polished using a wide belt sander until it became smooth.

Epoxy acrylate resin (Lipoxy 5p-i509,
A photocurable coating composition in which 400 parts of Showa Kobunshi Co., Ltd. (trade name), 150 parts of n-vinylpyrrolidone, 150 parts of 2-ethylhexyl acrylate, 150 parts of neopentyl glycol diacrylate, and 50 parts of benzoin isopropyl ether are uniformly mixed. was applied to the formwork plywood using a roll coater, and then cured by irradiation with an 80 w/cm mercury lamp for 4 seconds.

Example 2 200 parts of a solution of ethyl acrylate-butyl acrylate-vinyl acetate copolymer dissolved in butyl acetate (100 parts as nonvolatile content), 200 parts of calcium carbonate, and 100 parts of clay were uniformly kneaded using a high-viscosity disper. Thereafter, 40 g of toluene diisocyanate was added and coated on the surface of the formwork plywood material using a knife coater. After drying at 60° C. for 10 minutes, it was polished using a wide belt sander until it became smooth.

Urethane acrylate resin (Ebecryl 284゜UCB
Co., Ltd. (trade name)), 150 parts of tetrahydrofurfuryl acrylate, 150 parts of n-vinylpyrrolidone, 100 parts of tetraethylene glycol diacrylate, and 40 parts of jetoxyacetophenone. After painting plywood with a curtain flow coater, it was coated with a 80 w/all mercury lamp for
It was cured by irradiation for seconds.

Experimental example

Claims (4)

[Claims] (1) A sealing paint composition was applied to the surface of the wooden plywood material to make it smooth, a photocurable paint composition was applied on top of the paint film, and a cured paint film was formed by irradiating it with chemical light. Wooden plywood for concrete formwork featuring: (2) In claim 1, the photocurable coating composition comprises 10 to 80% by weight of a photocurable resin having two or more ethylenically unsaturated double bonds in one molecule, 10 to 70% by weight of an acrylic monomer, and Consists of 1 to 10% by weight of a sensitizer, and has a wavelength of 1
A wooden plywood for concrete formwork, characterized in that it is hardened by actinic light of 85 to 600 nanometers. (3) The first step is to apply a filler coating composition to the surface of the wooden plywood material to make it smooth, and after coating the coating film with a photocurable coating composition, it is cured by irradiating it with chemical light. A method for surface treatment of wooden plywood for concrete formwork, comprising a second step of forming a coating film. (4) Claim 3 is characterized in that the coating method for the filler coating composition and the photocurable coating composition is a knife coater, a roll coater, a curtain flow coater, etc. alone or in combination of two or more types. Surface treatment method for wooden plywood for concrete formwork.