JPS62296062A - Painted wooden panel for concrete mold frame - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention provides a novel coated wooden board for concrete formwork, particularly a coating layer with excellent durability and impact resistance. This relates to painted wooden boards for concrete formwork 11.

(Prior art and its problems) Conventionally, in concrete pouring work in civil engineering and construction work, etc., smoothing of the finished surface of concrete,
Formwork made of painted base plates is used to facilitate demolding work. The required characteristics of this coated plywood for concrete formwork include that the surface of the coating film is excellent in water resistance, alkali resistance, slipperiness, and easy peelability between the concrete and the coating film.

In general, it is necessary that the concrete does not adversely affect the hardening of the concrete or stain the surface, that is, there are no eluted or migrated substances from the first coating.

Hard crosslinked polymers are effective. In addition to this, durability (the number of times it can be used repeatedly) is also extremely important. In terms of durability, the higher the surface hardness, the more effective it is in preventing surface scratches when assembling formwork at construction sites and pouring concrete, and the more effective it is in preventing burns from nearby iron welding sparks when assembling formwork. From this point of view, cross-linked hard polymers are preferable for the paint film, but at the same time, the paint film must not crack or peel off from the plywood wood even when subjected to impact during rough handling on site. Also, if the plywood is not flexible enough to follow the expansion and contraction of the wood due to changes in temperature and moisture, the coating will peel off. Therefore, although the surface of durable coatings is hard, the interior is flexible.
It must have rM impact resistance and adhere well to wood.

(Means for Solving the Problems) The present invention has been achieved based on the above-mentioned requirements, and provides a painted wooden board for concrete formwork that has excellent durability and impact resistance and can be used repeatedly. to do [
The purpose of this painting is to use this painted wooden board.

(1) Urea-formaldehyde resin initial condensate or urea melamine-formaldehyde resin initial condensate
5 to 90% by weight, and (2)
One or more types of acrylic esters of alcohols having 2 or more carbon atoms or methacrylic esters of alcohols having 6 or more carbon atoms, and if necessary, one or more types of monomers that can be copolymerized with them. and 95 to 10 wt. .

(a) 1 to 15% by weight of one or more ethylenically unsaturated carboxylic acids, and (b) an ethylenically unsaturated -14X group amide or its alkylol or alkoxymethyl compound, an oxirane group-containing ethylenically unsaturated monomer; monomer, ethylenically unsaturated monomer containing a hydroxy group, ethylenically unsaturated monomer containing a dialkylaminoalkyl group, complete ester of polyhydric alcohol and acrylic acid or methacrylic acid, diallyl ester of dibasic acid, dihinylbenzene One or more crosslinkable polyfunctional irlk bodies selected from
1 to 15% by weight, and (c) one or more monoethylenically unsaturated rIY forms other than the above (a) and (b) 7
A top coat with a dry coating film hardness of H or higher in pencil hardness, which is formed from a synthetic resin emulsion composite obtained by copolymerizing 0 to 98 parts by weight. ,! consisting of layer (II);
The gist of this is that it has a composite coating layer.

To explain this, the inventors of the present invention have conducted extensive research on painted wood boards that have characteristics that satisfy all of the above-mentioned requirements. The present invention was developed based on the realization that this problem could be solved by constructing the following. In other words, the undercoat film layer according to the present invention, which is composed of two types of compositions, acts as a filler to the wooden board, adhesion by penetrating hardening, cracking, shock absorption, and absorbs the expansion and contraction of the wood, thereby making it easier for the topcoat applied thereon. It makes the film smooth, has adhesion properties, and is impact resistant, preferably with a soft coating film hardness, and a pencil hardness of HB or less is required. On the other hand, the top coat layer must have good water resistance, alkali resistance, hardness, weather resistance, smoothness, and peelability from the concrete surface, and must not affect the hardening reaction of the concrete and do not stain the concrete surface. This requires that the paint film hardness be H or higher in pencil hardness.The present invention uses a combination of seven coats with these characteristics and an undercoat film layer to achieve all of the properties required for concrete formwork. The objective is to provide a painted wood board that satisfies the requirements of

The contents of the present invention will be specifically explained below.

First, as described above, the composition forming the undercoat film layer (1) of the present invention contains 5 to 90% by weight of (+) urea-formaldehyde resin initial condensate or urea melamine-formaldehyde initial condensate and (2) One or more types of acrylic esters of alcohols having 2 or more carbon atoms or methacrylic esters of alcohols having 6 or more carbon atoms,
If necessary, one or more monomers copolymerizable with these are added, and the synthetic resin emulsion compound obtained by copolymerization is composed of a mixture of 95 to 10%. The coating layer has a pencil hardness of HBB or less, preferably B or less.

The urea-formaldehyde resin or urea-melamine-formaldehyde resin as component (1) may be one commonly used as an adhesive, and both have a urea diformaldehyde ratio or a urea melamine:formaldehyde ratio of 1:1.3 to 2. .0 is used. The content of this component is preferably 5% by weight or more based on 100% of the composition from the viewpoint of penetration, adhesion, and rigidity of the coating film to the wood board, and 90% by weight or less from the viewpoint of the adhesion of the top coat film. The content is good, preferably 30 to 70% by weight of the total.

In addition, the curing catalyst used for this is ammonium chloride,
Ammonium salts such as ammonium sulfate, carboxylic acid esters such as dimethyl oxalate, acid anhydrides such as maleic anhydride and phthalic anhydride, sodium salts of monochloroacetic acid and α,α°-dichlorohydrin. These include organic halogenated compounds, such as amine hydrochlorides, and amine hydrochlorides such as ethylamine hydrochloride and triethanolamine hydrochloride.

(2) As the acrylic ester of alcohol having 2 or more carbon atoms, there are acrylic esters such as ethyl acrylate, propyl acrylate, butyl acrylate pentyl acrylate, hexyl acrylate, and octyl 7-acrylate, and acrylic esters having 6 or more carbon atoms. Examples of methacrylic esters of alcohol include methacrylic esters such as hexyl methacrylate and dodecyl metal rylate. Furthermore, monomers that can be copolymerized with these and which can be added as necessary include methacrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, styrene, αe-methylstyrene, vinyltoluene, acrylonitrile, acid Ethylenically unsaturated monomers such as m-vinyl, vinyl 112ide, and ethylene, propylene,
Examples include combinatorial hydrocarbons such as butadiene, imprene, and chlorobrene. In addition, monomers having a guanoic acid group or a crosslinking group, such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, etc.
- Monoethylenically unsaturated carboxylic acids; ethylenically unsaturated -111 group amides or their alkylol or alkoxymethyl compounds 1 such as N-methylolacrylamide, N-methylolmethacrylamide, N-butoxymethylacrylamide, N-butoxymethylmethacrylamide Ethylenically unsaturated containing nioxirane group +
, such as glycidyl acrylate, glycidyl methacrylate, etc.; hydroxy group-containing ethylenically unsaturated monomers, such as 2-hydroxyethyl methacrylate,
2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, etc.; ethylenically unsaturated polymers containing dialkylaminoalkyl groups, such as diethylaminoethyl methacrylate; complete esters of polyhydric alcohols with acrylic acid or methacrylic acid, such as ethylene glycol di Examples include methacrylate, trimethylolpropane triacrylate, diethylene glycol diacrylate, etc.; diallyl esters of dibasic acids, such as diallyl orthophthalate, diallyl isophthalate, etc.; and crosslinking monomers such as divinylbenzene. The above FFI products may be used at least one type of F or a combination of several or more of these monomers, and in particular, those with functional groups can be used to create a stronger coating film due to the reaction with the urea-formaldehyde resin. It is effective because it forms

This emulsion polymer improves the adhesion between the undercoat film and the topcoat film, and the lower the film hardness, the better, and the glass transition temperature (Tg) of the polymer is O to -90°C, preferably -30 to - 60℃ is good.

This is because the coating film is too soft at -90°C or lower, causing adhesion and blocking during stacking before topcoating, and at temperatures above 0°C, the purpose of the undercoat film in the present invention is to improve shock absorption, temperature/humidity. This is because the expansion/contraction absorbency of the wood and the adhesion with the top coat film decrease due to the change. The above glass transition temperature (
Tg) is shown by the following calculation formula.

Tg: Glass transition temperature of copolymer (°K) TH4: Glass transition temperature of homopolymer consisting of monomer i (°K) Wi: Weight fraction of a-mer i in copolymer Blend of undercoat paint In this case, a finely powdered filler may be added to fill large hollows in the wood [1]. Preferred fillers include finely powdered clay, silica sand powder, and silica sand powder that do not inhibit the curing catalyst of the urea-formaldehyde initial condensate. Baryta etc. The amount of these is preferably 150 parts by weight or less per 100 parts by weight of the total amount of emulsion polymer and urea-formaldehyde resin, and if the amount is too much, the adhesion of the undercoat film to wood and wood will be reduced.

On the other hand, the composition forming the top coat layer (II) of the present invention contains (a) 1 to 15% by weight of one or more ethylenically unsaturated carboxylic acids, and (b) an ethylenically unsaturated basic amide. or its alkylol or alkoxymethyl compound, oxirane group-containing unsaturated monomer, hydroxy group-containing ethylenically unsaturated monomer, dialkylaminoalkyl group-containing ethylenically unsaturated monomer, polyhydric alcohol and acrylic acid, or 1 to 15% by weight of one or more crosslinkable polyfunctional monomers selected from complete esters with methacrylic acid, diallyl esters of dibasic acids, and divinylbenzene, and (c) the above (i); Consisting of a synthetic resin emulsion polymer obtained by copolymerizing 98 to 70% by weight of a monoethylenically unsaturated monomer other than (b),
The dry coating film hardness obtained from this is H or higher in terms of pencil hardness.

The ethylenically unsaturated carboxylic acids of component (A) include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, 2-acryloxyethyl phthalate, 2-methacryloxyethyl phthalate, 2-acryloxypropyl phthalate, 2-methacryloxypropyl phthalate, 2-acryloxyethyl succinate, 2-methacryloxyethyl succinate, 2-acryloxypropyl succinate, 2- Examples include methacryloxypropyl succinate. These are 1-15q in terms of emulsion stability and crosslinking properties.
(Q,% is necessary, preferably 3 to 10%).

Next, regarding component (b), as the ethylenically unsaturated basic amide or its alkylol or alkoxymethyl compound, N-methylolacrylamide, N-methylolmethacrylamide, N-butoxymethylacrylamide, N-butoxymethylmethacrylamide, N-
Methoxymethylacrylamide, N-methoxymethylmethacrylamide, etc.; As an oxirane group-containing ethylenically unsaturated monomer, glycidyl acrylate, glycidyl methacrylate glycidyl allyl ether, etc.; As a hydroxy group-containing ethylenically unsaturated monomer, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate,
2-hydroxypropyl acrylate, etc.; as an ethylenically unsaturated monomer containing a dialkylaminoalkyl group,
Dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc.; as a complete ester of polyhydric alcohol and acrylic acid or methacrylic acid, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate Examples of diallyl esters of dibasic acids include diallyl orthophthalate, diallyl isophthalate, and divinylbenzene. The amount of these polyfunctional monomers used is 1 to 15 parts by weight, preferably 3 to 1 per 100 parts by weight of the emulsion polymer.
If it is less than 1 part by weight, it will not be able to exhibit the water resistance, alkali resistance, and blistering resistance caused by iron welding sparks required for concrete formwork, and if it is more than 15 parts by weight, it will not adhere well to the undercoat layer. Sexuality decreases.

The monoethylenically unsaturated monomers other than (a) and (b), which are components (c), have the general formula % (in the formula, R1 is H or CH3, s is 0-C-X, is an organic group containing 1 to 10 carbon atoms, R3 is H or an alkyl group) and H2C=C-Z (wherein Y is H or a C0 atom, Z is a C1 atom), such as methyl acrylate, Ethyl acrylate, propyl acrylate, butyl acrylate,
Acrylic acid esters such as pentyl acrylate, hexyl acrylate, octyl acrylate; methyl methacrylate, ethyl methacrylate, pentyl methacrylate.

Methacrylic acid esters such as hexyl methacrylate;
Examples include acrylonitrile, styrene, α-methylstyrene, vinyltoluene, vinyl acetate, vinyl propionate, vinyl pasathyl heptaphosphate, vinyl chloride, and vinylidene chloride.

The emulsion polymer of the present invention may be produced by a general emulsion polymerization method in an aqueous medium using an emulsifier. Examples of the emulsifier include alkyl or alkylaryl sulfur salts or sulfonates, alkylaryl succinates, etc. Nonionic surfactants such as polyoxyethylene nonylphenol ether, polyoxyethylene alkyl ether, and polyoxyethylene carboxylic acid ester can be used. These are used as anionic surfactants, nonionic surfactants, or a combination of these, but since they have an unfavorable effect on the physical properties of the polymer coating, they should be used in small amounts. is desirable.

As the combined catalyst, ordinary water-soluble radical initiators such as potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, etc. can be used, and if necessary, reducing agents such as sodium hydrogen sulfite and L-7 Scorbine can be used. A redox initiator may also be used in combination with.

In addition, commonly used polymerization degree jA regulators, pH 31 regulators, etc. can also be used as needed.

The undercoat film composition and topcoat film composition of the present invention may each contain only the above-mentioned resin components.

Depending on the processing conditions, film forming aids, thickeners, antifoaming agents, etc.
(2) The addition of plasticizers, organic or inorganic pigments, etc. is also acceptable, and the amount added can be arbitrarily selected as required. Film-forming aids are effective for forming a uniform skin, and these include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate, and diethylene glycol heptanoethyl. Examples include high boiling point solvents such as ether acetate, diethylene glycol monobutyl ether acetate, benzyl alcohol, diethylene glycol dimethyl ether, and diethylene glycol monophenyl ether.

The painting method for the wooden board can be any known painting method, such as brush painting 1.
Haspray, roll coater, knife coater, curtain coater, etc. are used. For drying, normal heat drying is sufficient, hot air, far infrared rays, etc. can be used, and the drying temperature is 6.
The temperature is preferably 0°C or higher, preferably 80°C or higher, but 120°C or higher is not preferred in order to prevent deformation and warping of the wood board due to drying.

The amount of resin applied in the painted wood board for concrete formwork of the present invention is calculated in terms of resin content, and the undercoat film layer is a filler.

From the viewpoint of smoothness, etc., 20 to 150 g/rn', and 20 to 100 g/rn' for the top coat layer are preferable.

As mentioned above, the key point of the present invention lies in the combination of a composite coating film that combines an undercoat coating film and a topcoat coating film, that is, by clearly distinguishing the movement of the polymer between the wood contact area and the concrete contact area. . Therefore, it is possible to extend the idea of the present invention and provide an intermediate coat layer between the undercoat layer and the topcoat layer as necessary. For example, by changing the ratio of the undercoat emulsion polymer and the urea-formaldehyde initial condensate. It is also possible to use an emulsion that is slightly harder than the undercoating emulsion polymer.

Next, examples of Endkan II are shown, in which the middle part of each example represents parts by weight, and 1% represents weight %.

Example 1 100 parts of a 30% formaldehyde aqueous solution was adjusted to pH 7 with aqueous ammonia, then 37 parts of urea was added, the reaction was allowed to proceed at 90°C for 1 hour, and then 4 parts of urea was further added and the reaction was allowed to proceed for 5 minutes. After completion, neutralize to pH 7 with soda ash,
After cooling, a urea-formaldehyde resin initial condensate aqueous solution A was obtained. The evaporation residue of this aqueous solution was 50%. In another reaction vessel, 100 parts of ion-exchanged water, 1 part of sodium lauryl sulfate, 2 parts of polyoxyethylene nonylphenol ether (HL B 17.8), and 0.18 parts of sodium hydrogen sulfite were charged, and the space of the reaction vessel was replaced with nitrogen and then heated. At a reaction temperature of 70°C, 90 parts of butyl acrylate, N
- 100 parts of a monomer mixture consisting of 1 part of methylol acrylamide, 4 parts of 2-hydroxyethyl methacrylate and 5 parts of acrylic acid and 2% aqueous ammonium persulfate solution
At the same time, 0 parts were continuously added and reacted for 4 hours, and after the addition was completed, an aging reaction was further performed for 2 hours.
S. The evaporation residue of this emulsion was 46%, and the viscosity was 4.
The Tg of this polymer was -44°C.
Met.

Next, 50 parts of the urea-formaldehyde initial condensate aqueous solution A obtained above, 10 parts of emulsion Bl, 0.1 part of ammonium chloride, 70 parts of clay, 10 parts of titanium oxide, and 1 part of thickener Nobuco 5NEX3115K (trade name) were added. The mixture was thoroughly mixed using a disperser to obtain an undercoat paint-1. The viscosity was 6500 c,p.

Next, 84 parts of ion exchange water, 0.6 parts of sodium lauryl sulfate, 6 parts of polyoxyethylene nonylphenol ether (HL B 18.8) L, and 0.15 parts of sodium hydrogen sulfite were added to a reaction vessel to form a 1-cube space. After purging with nitrogen, the temperature was raised to 60°C, and a monomer mixture of 40 parts of styrene, 24 parts of methyl methacrylate, 16 parts of butyl acrylate, 12 parts of acrylonitrile, 5 parts of 2-hydroxyethyl methacrylate, and 3i'% of acrylic acid was prepared.
00 parts and 16 parts of 2% ammonium persulfate were simultaneously added and reacted continuously for 6 hours, and after the addition was completed, 2% ammonium persulfate was added.
After one reaction of time aging reaction, p with aqueous ammonia,
The temperature was adjusted to H7, and emulsion C was obtained. The evaporation residue of this emulsion C was 49%, and the viscosity was 7500c, p.

Met.

To 100 parts of this emulsion C, 5 parts of ethylene glycol monobutyl ether acetate and 6 parts of dibutyl phthalate.
and thickener Nobuco 5NEX3115K (product name) 1
These parts were mixed to obtain top coat paint-2. The minimum film forming temperature (M, F) of this paint.

T,) was 30°C.

Next, apply 120 coats of undercoat paint -1 to the plywood with a thickness of 12 m/+i.
g/m' using a knife coater and dried at 80°C. Next, top coat paint 2 was applied with a roll coater at log/m', and dried and cured at 100°C to obtain a coated plywood for concrete formwork.

Example 2 A monomer mixture of 7 parts of methyl methacrylate, 85 parts of 2-ethylhexyl acrylate, 5 parts of methacrylic acid, and 3 parts of 2-hydroxyethyl methacrylate was emulsion polymerized in the same manner as in Example 1, and the evaporation residue was 45%. , viscosity 2000c,
Emulsion D for undercoat paint of p.

Next, 50 parts of this emulsion D, 50 parts of the aqueous solution of the urea-formaldehyde resin initial condensate of Example 1, 0.1 part of ammonium chloride, and 45 parts of clay Oyobi Nopko 5NEX
Mix 2 parts of 3115K (product name) and apply primer paint-3
I got it.

Next, 30 parts of styrene, 22 parts of methyl methacrylate, 30 parts of ethyl acrylate, 10 parts of acrylonitrile, N
- 3 parts of methylol acrylamide and 5 parts of methacrylic acid
This monomer mixture was subjected to emulsion polymerization in the same manner as in Example 1 to obtain emulsion E for top coating. This emulsion'
The M 9 iX content was 48% and the Tg of the polymer was 53°C.

To 100 parts of this emulsion, 4 parts of diethylene glycol monobutyl ether acetate, 5 parts of cyphthylphthalate and Nobuco 5NEX3115K (trade name) 2i-
ifI was mixed to obtain top coat-4.

Apply 130g/r of primer paint-3 to plywood with a thickness of 12cm/m.
n'-r and topcoat paint-4 were applied at 100 g/ln'ffi in the same manner as in Example 1 and dried to obtain coated plywood for concrete formwork.

Example 3 21 parts of styrene, 70 parts of 2-ethylhexyl acrylate
A monomer mixture consisting of 1 part, 5 parts of acrylonitrile, and 4 parts of methacrylic acid was emulsion polymerized in the same manner as in Example 1 to obtain emulsion F for an undercoat having a viscosity of 47% and a viscosity of 1500 c.p.

50 parts of this emulsion F, 70 parts of the aqueous solution of the urea-formaldehyde resin initial condensate of Example 1, 0.15 parts of ammonium IL, 40 parts of clay, and 1 SNE knob.
Mix 3 parts of X3115K (trade name) and use it as an undercoat paint.
Got 5. The viscosity of this paint was 7000 c,p.

Next, 55 parts of α-methylstyrene, 20 parts of 2-ethylhexyl acrylate, 14 parts of acrylonitrile, 8 parts of 2-hydroxyethyl methacrylate, and 3 parts of methacrylic acid were added.
Emulsion polymerization was carried out in the same manner as in Example 1 to obtain emulsion G for top coatings with an evaporation residue of 48.8% and a viscosity of 7500 c.p.

0.100 parts of this emulsion was mixed with 4 parts of diethylene glycol monobutyl ether acetate, the viscosity was adjusted with water, and 1-coating paint-6 was prepared.

The evaporation residue of this paint is 45%, the viscosity is 5500C, p,
Met.

Next, apply 13 coats of undercoat paint -5 to the plywood with a thickness of low/m.
0 g/m'TeJ2"JuriPaint-6908/rn"
'Ic' IHj was coated and dried in the same manner as Ic side 1 to obtain a coated plywood for concrete formwork.

Example 4 100 parts of a 37% formaldehyde aqueous solution was adjusted to pH 8 with sodium hydroxide, then 37 parts of urea was added, and the temperature was heated at 85°C.
After reacting for 400 minutes, formic acid was added to adjust the pH to 4.8, and after reacting for 200 minutes, urea 8
1 part of melamine and 1 part of melamine were added and reacted for 5 minutes. After completion of the reaction, the mixture was neutralized to pH 7 with soda ash and cooled to obtain an aqueous solution H of urea melamine-formaldehyde resin initial condensate. The evaporation residue of this aqueous solution was 48.5%.

An undercoat paint-7 was obtained in the same manner as in Example 1, except that the aqueous solution of the urea-formaldehyde resin initial condensate MA in Example 1 was replaced with the aqueous solution H of the urea-melamine-formaldehyde resin initial condensate described in "1."

Next, 19 parts of α-methylstyrene, 62 parts of styrene, 2-
A monomer mixture consisting of 10 parts of ethylhexyl acrylate, 4 parts of glycidyl methacrylate, and 5 parts of methacrylic acid was emulsion polymerized in the same manner as in Example 1, and the evaporation residue was 50 parts.
%, viscosity 12,000 c, p, 11) Emulsion for coating paints ■, 6 parts of ethylene glycol monobutyl ether acetate and 3 parts of dibutyl phthalate were mixed with this emulsion I, and the viscosity was adjusted to 8,000 c, p with water. A top coat-8 with an evaporation residue of 43% was obtained.

Next, apply 120 coats of primer paint -7 to the 12 m/m thick plywood.
A coated plywood for concrete formwork was obtained by applying and drying the top coat paint 8 at 90 g/g/g in the same manner as in Example 1.

Comparative Example 1 8 coats of top coat paint 1 of Example 1 on 12 m thick plywood
The coating was applied twice at 0 g/rn' and dried under the same conditions as in Example 1 to obtain a coated plywood for concrete formwork with a coating layer of a single composition.

Comparative Example 2 A commercially available solvent-based concrete formwork paint was applied to plywood with a thickness of 12m/+* in three separate doses at a total of 220g/go - dried, and a single composition coating layer was applied for concrete formwork. I got plywood.

The characteristics of the coating layer of the painted plywood obtained in each of the above Examples and Comparative Examples were investigated using the test method below.
The results shown in the table were obtained.

Test method 1゜Impact resistance specified in JIS B1501 (steel balls for ball bearings) 2
A grade 1 kg copper ball was dropped from a height of 1 m perpendicularly to the coated surface of the coated plywood for concrete formwork, and the condition of the coated film layer was observed.

(Judgment criteria) O... No cracks in the coating layer Δ... ``Some cracks...Conflicts'' Many occurred 2. Painted plywood for water-resistant concrete formwork was soaked in boiling water for 4 hours. Observe the condition of the subsequent coating layer.

(Judgment base 2?-) O... No abnormality Δ... Some blistering, lifting, and whitening of the paint layer ×...
” HM n Many (effects of the invention) The painted wood board for concrete formwork according to the present invention.

In addition to having excellent properties required for formwork, such as impact resistance, water resistance, smoothness, and easy peelability between concrete and paint, it is also durable, so it can be used repeatedly. It has the effect of being usable.

Claims (2)

[Claims] (1) Urea-formaldehyde resin initial condensate or urea melamine-formaldehyde resin initial condensate 5-90
weight% and (2) One or more monomers copolymerizable with one or more acrylic esters of alcohols having 2 or more carbon atoms or methacrylic esters of alcohols having 6 or more carbon atoms, if necessary. Synthetic resin emulsion polymer obtained by adding two or more types and copolymerizing 95% ~
10% by weight of an undercoat film layer (I) formed from a mixture with a dry coating hardness of HB or less in terms of pencil hardness; (A) 1 to 15% by weight of one or more ethylenically unsaturated carboxylic acids; (b) Ethylenically unsaturated monobasic amide or its alkylol or alkoxymethyl compound, oxirane group-containing ethylenically unsaturated monomer, hydroxy group-containing ethylenically unsaturated monomer, dialkylaminoalkyl group-containing ethylene one or more crosslinkable polyfunctional monomers selected from polyunsaturated monomers, complete esters of polyhydric alcohols and acrylic acid or methacrylic acid, diallyl esters of dibasic acids, and divinylbenzene; Synthetic resin emulsion polymer obtained by copolymerizing 15% by weight and (c) 98 to 70% by weight of one or more monoethylenically unsaturated monomers other than (a) and (b) above. A coated wooden board for concrete formwork having a composite coating layer (II) formed from a topcoat coating layer (II) having a dry coating hardness of H or higher in pencil hardness.