JP2006307050A - One-component primer composition and coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a one-component primer composition which excels in storage stability, in which even if it is applied to a brittle inorganic material with much intake, there is little intake, and an underlying material can be reinforced, in which even if it is recoated on various deteriorated old coating films, the lifting of the old coating films is not caused, and which can form a coating film excellent in solvent resistance, and to provide the coating method. <P>SOLUTION: The one-component primer composition comprises: an epoxy resin having at least one epoxy group in one molecule; a ketimines compound obtained by the dehydrating condensation reaction of a carbonyl compound and a primary amino group; and an organic solvent, wherein the epoxy resin and the ketimines compound are included by the combining percentage so that the ratio (the numbers of active hydrogens/the numbers of epoxy groups) of the total active hydrogen numbers of the ketimines compound to the total epoxy group numbers of the epoxy resin is set to 0.5-5.0, wherein at least 95 mass% of the organic solvent is an organic solvent with the boiling point of at least 150°C, and wherein the epoxy resin and the ketimines compound are dissolved in the organic solvent and do not contain pigments. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a one-component undercoating composition and a coating method. More specifically, the present invention has excellent storage stability, and even if it is applied to an inorganic material that is fragile and has a lot of suction, the suction can be reduced and the base can be reinforced. Even when applied over various deteriorated old paint films, it does not cause lifting of the old paint film, can improve the adhesion between the base and the top coat, and has excellent solvent resistance. The present invention relates to a one-component undercoating composition that can be formed and a coating method using the coating composition.

  Epoxy resins are excellent in various properties, particularly adhesive strength, and thus have been conventionally applied to various fields such as paints, sealing agents, adhesives and the like. However, most of the epoxy resins that are usually used are two-component types consisting of a main agent and a curing agent, and the curing reaction proceeds immediately after mixing. It was very short and there was a problem in workability.

  For this reason, as a method for extending the pot life, for example, a method using a latent curing agent such as a blocked isocyanate-modified epoxy resin is known. However, the curing agent is originally a heat-curing type and is dried at room temperature. It is not satisfactory for practical use.

  Further, a one-pack type epoxy resin coating containing an epoxy ester resin having a room temperature drying property without a curing agent has been studied. However, since such a one-pack type epoxy resin paint is an air oxidation type, if it is a thick film coating, the coating surface dries before the inside of the coating is dried, and a solvent remains in the coating, So-called medium sag, in which the inside is not sufficiently cured, is likely to occur. Furthermore, in general, the solvent resistance is inferior compared to a coating film formed with a two-pack type epoxy resin paint, and depending on the type of top coating applied on this coating film, it can be used because it causes blemishes. There was a problem that the top coating material was greatly limited.

  One-pack type epoxy resin coating composition containing epoxy resin, ketimine compound, dehydrating agent and additive resin (modified epoxy resin, xylene resin, petroleum resin, etc.) as a coating that can solve these problems. In order to improve the quality, a coating composition containing a large amount of a strong solvent such as a ketone solvent as a solvent has been proposed (see, for example, Patent Document 1). However, when a coating composition containing a large amount of this strong solvent is applied on the old coating film, the old coating film is affected by the solvent in the coating composition, and lifting of the old coating film occurs. was there.

  Furthermore, as a coating composition that can solve the problem of lifting the old paint film, an organic hydrocarbon solvent selected from an aliphatic hydrocarbon solvent and a high boiling aromatic hydrocarbon solvent having a boiling point of 148 ° C. or higher is used. A one-pack type epoxy resin coating composition using an organic solvent containing 95% by weight or more in the solvent has been proposed (for example, see Patent Document 2). However, since the coating composition contains solvent-insoluble substances such as coloring pigments and extender pigments, it is often sucked, and impregnating reinforcement is poor when applied to fragile materials and deteriorated old paint films. There were problems such as insufficient reinforcement of the foundation and easy peeling of the coating film over time.

JP-A-8-217859 Japanese Patent Laid-Open No. 2001-40281

  The object of the present invention is excellent in storage stability, workability, and drying property, and even if it is applied to an inorganic material that is fragile and often sucked in, the suction can be reduced, the base can be reinforced, and various deteriorated old paint films Even if it is overcoated, it does not cause lifting of the old paint film, can improve the adhesion between the undercoat and the top coating, and has excellent top coatability, solvent resistance, water resistance, alkali resistance, etc. An object of the present invention is to provide a one-component undercoat coating composition capable of forming a coating film and a coating method using the coating composition.

  As a result of diligent research to achieve the above object, the present inventors have used an epoxy-ketimine moisture curing mechanism, used an organic solvent having a boiling point of 150 ° C. or higher, and used coloring pigments, extender pigments, etc. The inventors have found that the above object can be achieved by using a composition that does not contain a solvent-insoluble substance, thereby completing the present invention.

  That is, the coating composition of the present invention comprises an epoxy resin (A) having at least one epoxy group in one molecule, a ketimine compound (B) obtained by a dehydration condensation reaction between a carbonyl compound and a primary amino group. And the epoxy resin (A) and the ketimine compound (B), the ratio of the total active hydrogen number of the ketimine compound to the total number of epoxy groups of the epoxy resin (active hydrogen number / epoxy Group) is contained in a blending ratio of 0.5 to 5.0, 95% by mass or more of the organic solvent (C) is an organic solvent having a boiling point of 150 ° C. or more, and the epoxy resin (A) and the ketimines The compound (B) is a one-component undercoating composition which is dissolved in the organic solvent (C) and does not contain a pigment.

  In addition, the coating method of the present invention can be applied to the surface of concrete, mortar, flexible board, slate, gypsum board, calcium silicate board, ALC board, or extrusion-molded board, or on various deteriorated old paint films. A one-component undercoat paint composition is applied.

  The one-component undercoat paint composition of the present invention is excellent in storage stability, workability, impregnation reinforcing property, and drying property, and even if it is applied to an inorganic material that is fragile and often sucks, it absorbs less and reinforces the base. It can be applied to various deteriorated old paint films without lifting the old paint film, improving adhesion between the base and top coat, and suitable for top coating and solvent resistance. A coating film excellent in water resistance, alkali resistance and the like can be formed.

  In addition, when the one-component undercoating composition of the present invention is applied to various inorganic materials, the ketimine compound (B), which is a curing agent, is first-class due to moisture contained in the inorganic material or in the air. It hydrolyzes to an amino compound and cures by reacting the primary amino compound and the epoxy group in the epoxy resin (A), and exhibits excellent substrate reinforcement.

  Further, since the one-component undercoat paint composition of the present invention is a solvent in which the organic solvent in the composition does not cause the lifting of the old coating film, The effect of improving the impregnation reinforcing effect and the adhesion to the top coat is exhibited.

The present invention is described in detail below.
The one-component undercoat coating composition of the present invention comprises an epoxy resin (A) having at least one epoxy group in one molecule, a ketimine compound obtained by a dehydration condensation reaction between a carbonyl compound and a primary amino group ( B) and an organic solvent (C), and the ratio of the total number of active hydrogens of the ketimine compound to the total number of epoxy groups of the epoxy resin (the number of active hydrogens) of the epoxy resin (A) and the ketimine compound (B) / Epoxy group number) is contained at a blending ratio of 0.5 to 5.0, 95% by mass or more of the organic solvent (C) is an organic solvent having a boiling point of 150 ° C. or more, the epoxy resin (A) and the epoxy resin (A) The ketimine compound (B) is dissolved in the organic solvent (C) and does not contain a pigment.

<Epoxy resin (A)>
The epoxy resin (A) having at least one epoxy group in one molecule used in the present invention is an epoxy resin that can be dissolved in the organic solvent (C) described later, and preferably contains two or more epoxy groups, It is an epoxy resin having a number average molecular weight of about 350 to 3,000 and an epoxy equivalent of about 80 to 1,000.

  Examples of the epoxy resin include glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, other glycidyl type epoxy resins, alicyclic epoxy resins, and modified epoxy resins obtained by modifying these epoxy resins with alkylphenols or fatty acids. An epoxy group-introduced alkylphenol or an alkylphenol novolac resin obtained by a reaction between an alkylphenol or an alkylphenol novolac resin and epichlorohydrin can be used.

  The glycidyl ether type epoxy resin can be obtained, for example, by reacting a polyhydric alcohol, polyhydric phenol or the like with an excess amount of epihalohydrin or alkylene oxide. Examples of the above polyhydric alcohol include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, neopentyl glycol, butylene glycol, hexanediol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, diglycerin, sorbitol, etc. Can be mentioned. Examples of the polyhydric phenol include 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 2,2-bis (2-hydroxyphenyl) propane, 2- (2-hydroxyphenyl)- 2- (4-hydroxyphenyl) propane, halogenated bisphenol A, bis (4-hydroxyphenyl) methane [bisphenol F], tris (4-hydroxyphenyl) propane, resorcin, tetrahydroxyphenylethane, 1,2,3- Examples include tris (2,3-epoxypropoxy) propane, novolac type polyhydric phenol, cresol type polyhydric phenol, and the like.

  Examples of the glycidyl ester type epoxy resin include phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, and dimer acid diglycidyl ester.

  Examples of the other glycidyl type epoxy resins include tetraglycidylaminodiphenylmethane and triglycidyl isocyanurate.

  Examples of the alicyclic epoxy resin include (3,4-epoxy-6-methylcyclohexyl) methyl-3,4-epoxy-6-methylcyclohexanecarboxylate, (3,4-epoxycyclohexyl) methyl-3, 4-epoxycyclohexanecarboxylate, bis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, Epolide GT300 (manufactured by Daicel Chemical Industries, Ltd., trade name 3 Functional Alicyclic Epoxy Resin), Epolide GT400 (Daicel Chemical Industries, Ltd., trade name, tetrafunctional alicyclic epoxy resin), EHPE (Daicel Chemical Industries, Ltd., trade name, polyfunctional alicyclic epoxy) Resin) and the like.

  The above-mentioned modified epoxy resin is at least one selected from alkylphenol and fatty acid as the above-mentioned glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, other glycidyl type epoxy resin or epoxy resin before modification which is an alicyclic epoxy resin. It is an epoxy resin modified with a modifier. The epoxy resin before modification preferably has an average epoxy equivalent of about 250 or less.

  The alkylphenol that can be used as the modifier is preferably an alkylphenol having an alkyl group having about 2 to 18 carbon atoms, and specific examples thereof include para t-butylphenol, paraoctylphenol, and nonylphenol. Further, as the fatty acid that can be used as the above modifier, drying oil fatty acid, semi-drying oil fatty acid are suitable, and specific examples thereof include linseed oil fatty acid, safflower oil fatty acid, soybean oil fatty acid, sesame oil fatty acid, eno oil fatty acid, Hemp oil fatty acid, grape kernel oil fatty acid, tung oil fatty acid, corn oil fatty acid, sunflower oil fatty acid, cottonseed oil fatty acid, walnut oil fatty acid, rubber seed oil fatty acid, fish oil fatty acid, fish oil fatty acid, high diene fatty acid, tall oil fatty acid, dehydrated castor oil A fatty acid etc. can be mentioned. Each of the above-mentioned modifiers, alkylphenol and fatty acid, may be used alone or in combination of two or more.

  The modified epoxy resin as described above can be obtained by heating a mixture of the above-mentioned epoxy resin before modification and the above modifier to 100 to 200 ° C. in the presence of a catalyst as necessary. The reaction between the epoxy resin before the modification and the modifier is 1: 0.2 in a ratio of (total number of epoxy groups in the epoxy resin) :( total number of hydroxyl groups in the alkylphenol and total number of carboxyl groups in the fatty acid). It is preferable to mix and react so as to be in the range of ~ 0.6.

<Ketimines (B)>
The ketimine compound (B) obtained by dehydration condensation reaction between a carbonyl compound and a primary amino group used in the present invention is a polyamine having at least one primary amino group blocked in the carbonyl compound in one molecule. And includes aldimine compounds. The ketimine compound (B) can be dissolved in the organic solvent (C) described later, and is a curing agent for the epoxy resin (A). The “primary amino group blocked with a carbonyl compound” is a protected amino group that can be easily hydrolyzed to a free primary amino group, for example, in the presence of moisture, Formula -N = CR ¹ R ²
(Wherein R ¹ represents a hydrogen atom or a monovalent hydrocarbon group such as an alkyl group or a cycloalkyl group, and R ² represents a monovalent hydrocarbon group such as an alkyl group or a cycloalkyl group). Can show. Here, when R ¹ is a hydrogen atom, it is an aldimine compound.

  The polyamine compound before being blocked with the carbonyl compound may be any of aliphatic, alicyclic and aromatic. Moreover, as long as it has a primary amino group, polyamides may be used. The polyamine compound is required to have a primary amino group that undergoes a curing reaction with the epoxy resin, but is generally about 2,000 or less, preferably about 30 to about 1,000. It is advantageous to have a primary amino group equivalent. The polyamine compound generally has a number average molecular weight in the range of about 5,000 or less, preferably about 3,000 or less.

  As polyamine compounds as described above, aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylenehexamine; aromatic polyamines such as metaxylenedimine, diaminodiphenylmethane, and phenylenediamine And alicyclic polyamines such as isophoronediamine, cyclohexylpropylamine, 1,3-bisaminomethylcyclohexane and norbornenediamine; and polyamines having a primary amino group at the molecular terminal.

  Among the polyamine compounds described above, a compound that does not contain a secondary amino group in the molecule, that is, a compound obtained by ketiminizing a polyamine compound having only a primary amino group has storage stability after being mixed with the epoxy resin (A). It is particularly suitable because it is good. Therefore, when a ketimine compound having a secondary amino group in the molecule is used, it is desirable to use it as an adduct compound obtained by reacting the secondary amino group with the above-described epoxy resin.

  As carbonyl compounds that can be used to ketiminate the above polyamine compounds, any commonly used ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl isopropyl ketone, diisobutyl ketone, methyl-t-butyl ketone, cyclohexanone Etc. Moreover, aldehydes, such as acetaldehyde and a benzaldehyde, can be mentioned as a carbonyl compound which can be used in order to aldiminate a polyamine compound.

  The reaction between the polyamine compound and the carbonyl compound can be carried out by a method known per se, with quantitative proportions and reaction conditions such that substantially all of the primary amino groups present react with the carbonyl compound. It is desirable to use The reaction is a dehydration reaction, and in order to proceed easily, it is generally advantageous to use a ketone having poor water solubility and low steric hindrance such as methyl isobutyl ketone and methyl ethyl ketone as the carbonyl compound. is there.

  In the one-component undercoating composition of the present invention, the above-mentioned epoxy resin (A) and the above-mentioned ketimine compound (B) are combined in a ratio of the total number of active hydrogens of the ketimine compound to the total number of epoxy groups of the epoxy resin ( (The number of active hydrogens / the number of epoxy groups) is 0.5 to 5.0, preferably 0.85 to 3.0. If the blending ratio is out of this range, the performance of the coating film such as solvent resistance, non-adhesiveness, water resistance and the like is not preferable.

  In the one-component undercoat paint composition of the present invention, a urethane-modified epoxy resin and / or a xylene resin, a toluene resin, a ketone resin, a coumarone resin, and a petroleum resin are used as necessary in order to improve the drying property of the coating film. Resins that are solid at room temperature selected from the group consisting of:

<Organic solvent (C)>
In the one-component undercoat coating composition of the present invention, an organic solvent (C) is used to uniformly dissolve the solid content in the coating composition and adjust the viscosity. Considering that the organic solvent (C) does not cause lifting of the old paint film when the coating composition is applied over the old paint film and has a low odor, the organic solvent (C) 95% by mass or more of an organic solvent having a boiling point of 150 ° C. or more, preferably 70 to 90% by mass of an aliphatic hydrocarbon solvent having a boiling point of 150 ° C. or more and 30 to 10% by mass of an aromatic hydrocarbon solvent having a boiling point of 150 ° C. or more. A mixed organic solvent consisting of

  Specific examples of the aliphatic hydrocarbon solvent having a boiling point of 150 ° C. or higher include, for example, mineral spirit, mineral turpentine, white spirit, isoparaffin, IP solvent 1620, IP solvent 2028, IP solvent 2835 (“IP solvent” is Idemitsu Petrochemical Co., Ltd.) (Trade name manufactured by the company), n-nonane, isononane, n-decane, n-dodecane, and the like can be listed as aliphatic hydrocarbon solvents with low solubility and low odor. These aliphatic hydrocarbon solvents can be used alone or in combination of two or more.

  Specific examples of the aromatic hydrocarbon solvent having a boiling point of 150 ° C. or higher include, for example, Solvent Naphtha, Solvesso 100, Solvesso 150, Solvesso 200 (“Sorbessa” is a trade name of ExxonMobil Co., Ltd.), Swazol 1000, Swazol 1500, Swazol 1800 (“Swazole” is a trade name manufactured by Cosmo Oil Co., Ltd.) and the like can be mentioned. These aromatic hydrocarbon solvents can be used alone or in combination of two or more.

  The one-component undercoat coating composition of the present invention may contain other organic solvents that do not fall under the above aliphatic hydrocarbon solvents or aromatic hydrocarbon solvents as part of the organic solvent. . However, the content of the other organic solvent is 5% by mass or less, preferably 3% by mass or less in the organic solvent. When the content of the other organic solvent is increased, lifting of the old paint film is likely to occur when it is applied to the old paint film, and the odor becomes strong.

  In the one-component undercoat paint composition of the present invention, in consideration of the suitability of the old coating film, most preferably 70 to 90% by mass of an aliphatic hydrocarbon solvent having a boiling point of 150 ° C. or higher and an aroma having a boiling point of 150 ° C. or higher. A mixed organic solvent composed of 30 to 10% by mass of a group hydrocarbon solvent is used.

  The content of the organic solvent (C) in the one-component undercoat coating composition of the present invention is not particularly limited as long as it can maintain the coating viscosity and coating state within an appropriate range. Usually, it mix | blends in the quantity used as 20-90 mass% in a coating composition.

  The one-component undercoat coating composition of the present invention contains the above-described epoxy resin (A), ketimine compound (B) and organic solvent (C) as essential components, and further increases the viscosity as necessary. In order to prevent the inhalation of the substrate, and to enhance the impregnation reinforcement when applied to fragile materials and deteriorated old paint film, it can contain agents, plasticizers, dispersants, antifoaming agents, etc. It is necessary to contain no pigment.

  The one-component undercoat paint composition of the present invention is composed of an inorganic material surface such as concrete, mortar, flexible board, slate, gypsum board, calcium silicate board, ALC plate, and extrusion-molded plate, or an old coating surface of these materials. Can be painted on the surface of the substrate. As a coating method, general methods such as brush coating, roller brush coating, spray coating, and various coater coatings can be used.

  In particular, when the one-component undercoat paint composition of the present invention is applied to a fragile substrate with a lot of suction, the suction is stopped and the effect of reinforcing the base is exhibited. In such a case, the effect of not lifting the old paint film surface can be exhibited.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In Examples and Comparative Examples, “part” means “part by mass” unless otherwise specified.

Example 1
In a container, "Epicoat 168V70" (trade name, manufactured by Japan Epoxy Resin Co., Ltd., mineral spirit solution of modified bisphenol A type epoxy resin, solid content 70% by mass), 100 parts, "New Solvent A" (manufactured by Nippon Oil Corporation) Trade name, mineral spirit) 100 parts, "Swazol 1000" (trade name, manufactured by Cosmo Oil Co., Ltd., organic solvent having a boiling point of 160-170 ° C mainly composed of C9 aromatic hydrocarbon solvent), and "ADEKA 27 parts of "Hardener EH235SK-5" (trade name, manufactured by Asahi Denka Co., Ltd., ketimine in polyethylenamines, HAWS solution of solid content 70% by mass) were mixed and stirred to obtain a coating composition.

Examples 2-6 and Comparative Examples 1-4
Each coating composition was obtained in the same manner as in Example 1 except that the composition of the coating composition was as shown in Table 1. However, in Examples 4 to 6, instead of “Epicoat 168V70”, “Epicron 5900-60” (trade name, manufactured by Dainippon Ink Co., Ltd., mineral spirit solution of modified bisphenol A type epoxy resin, solid content 60 mass% In Comparative Example 3, “Dytokraal D-6868” (trade name, modified polyamidoamine manufactured by Daito Sangyo Co., Ltd.) was used instead of “Adeka Hardener EH235SK-5”.

Comparative Example 5
In a container, 100 parts of “Epicoat 168V70”, 20 parts of vinyltrimethoxysilane, 70 parts of magnesium silicate, 50 parts of titanium dioxide, 250 parts of “New Solvent A”, and 80 parts of “Swazole 1000” were sequentially charged and mixed. Pigment dispersion was performed with a sand mill until the nub was 60 μm or less (according to JIS K5600-2-5). To 500 parts of this pigment dispersion, 24 parts of “ADEKA HARDNER EH235SK-5” was charged and mixed by stirring to obtain a coating composition.

Comparative Example 6
A coating composition was obtained in the same manner as in Comparative Example 5 except that the composition of the coating composition was as shown in Table 1.

Test Examples Various tests were performed on the coating compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 6 based on the following test methods. The test results were as shown in Table 1.

<Storage stability>
800 g of each coating composition obtained in Examples 1 to 6 and Comparative Examples 1 to 6 was collected in a 1-liter round can, sealed, and visually observed for the state of the coating after being left at 50 ° C. for 1 month. did. Evaluation was according to the following criteria.
○: no abnormality, Δ: thickening, x: gelation.

<Solvent resistance>
Each coating composition obtained in Examples 1 to 6 and Comparative Examples 1 to 6 is applied to a 3 mm × 70 mm × 150 mm slate plate so that the coating amount is 1.0 g per one surface area (70 mm × 150 mm) of the slate plate. It was applied with a brush and dried for 16 hours in an atmosphere of a temperature of 23 ° C. and a humidity of 50% RH. On this coated surface, a weak solvent type urethane resin paint “DNT urethane mild clean” (manufactured by Dainippon Paint Co., Ltd.) was applied twice with a brush in an atmosphere of a temperature of 23 ° C. and a humidity of 50% RH. The coating amount per coating was 1.0 g per one surface area (70 mm × 150 mm) of the slate plate, and the coating interval was 16 hours. The coated plate was left in an atmosphere of a temperature of 23 ° C. and a humidity of 50% RH for 7 days, and then xylene was dropped on the coated surface, and the coated surface state was visually observed. Evaluation was according to the following criteria.
○: No abnormality, x: Itching occurred.

<Impregnation reinforcement>
The coating amount of each coating composition obtained in Examples 1-6 and Comparative Examples 1-6 on a low density calcium silicate plate (specific gravity 0.8) of 6 mm × 70 mm × 150 mm is one surface area of the calcium silicate plate (70 mm × 150 g) with a brush, and dried in an atmosphere of a temperature of 23 ° C. and a humidity of 50% RH for 16 hours. On this coated surface, a weak solvent type urethane resin paint “DNT urethane mild clean” was applied twice with a brush in an atmosphere at a temperature of 23 ° C. and a humidity of 50% RH. The coating amount per coating was 1.0 g per one surface area (70 mm × 150 mm) of the calcium silicate plate, and the coating interval was 16 hours. This coated plate was left in an atmosphere of a temperature of 23 ° C. and a humidity of 50% RH for 7 days, and then an adhesion test according to JIS K5600-5-6 was performed with a lattice spacing of 2 mm. Evaluation was according to the following criteria.
○: Classification 0 or 1, Δ: Classification 2 or 3, X: Classification 4 or 5.

<Formality of old paint film>
A non-water-dispersible acrylic resin paint “Bildeck” (manufactured by Dainippon Paint Co., Ltd.) is applied to a slate plate of 3 mm × 70 mm × 150 mm at a rate of 1.0 g per one surface area (70 mm × 150 mm) of the slate plate. Then, it was applied twice with a brush and dried in an atmosphere at a temperature of 50 ° C. for 7 days to prepare an old paint film coated plate. Each coating composition obtained in Examples 1 to 6 and Comparative Examples 1 to 6 was applied to this old paint film coated plate with a brush so that the coating amount was 1.0 g per one surface area (70 mm × 150 mm) of the slate plate. After coating, the degree of dissolution of the old paint film was observed. Evaluation was according to the following criteria.
○: No dissolution of the old paint film, ×: Dissolution of the old paint film

The one-component undercoat paint compositions of the present invention obtained in Examples 1 to 6 had good results in any of storage stability, solvent resistance, impregnation reinforcing property, and old coating film suitability. In contrast, in the coating composition obtained in Comparative Example 1 using an organic solvent having a boiling point of less than 150 ° C. and Comparative Example 2 using an organic solvent in which the organic solvent having a boiling point of less than 150 ° C. accounts for 50% by mass. In the obtained coating composition, the suitability of the old coating film was poor. The coating composition obtained in Comparative Example 3 using a modified polyamidoamine without using a ketimine compound had poor storage stability. Contains the epoxy resin (A) and the ketimine compound (B) at a blending ratio such that the ratio of the total active hydrogen number of the ketimine compound to the total number of epoxy groups of the epoxy resin (active hydrogen number / epoxy group number) is 0.3. In the coating composition obtained in Comparative Example 4, the solvent resistance was poor. The coating compositions obtained in Comparative Examples 5 and 6 containing pigments were poor in storage stability and impregnation reinforcement.

Claims (5)

  An epoxy resin (A) having at least one epoxy group in one molecule, a ketimine compound (B) obtained by a dehydration condensation reaction between a carbonyl compound and a primary amino group, and an organic solvent (C), The ratio of the total active hydrogen number of the ketimine compound to the total epoxy group number of the epoxy resin (active hydrogen number / epoxy group number) of the epoxy resin (A) and the ketimine compound (B) is 0.5 to 5.0. 95 mass% or more of the organic solvent (C) is an organic solvent having a boiling point of 150 ° C. or more, and the epoxy resin (A) and the ketimine compound (B) are the organic solvent (C A one-component undercoat paint composition which is dissolved in the composition and does not contain a pigment.   The ratio of the total active hydrogen number of the ketimine compound to the total number of epoxy groups of the epoxy resin (A) and the ketimine compound (B) (active hydrogen number / epoxy group number) is 0.85 to 3.0. The one-component undercoat paint composition according to claim 1, which is contained in a blending ratio.   The organic solvent (C) is composed of 70 to 90% by mass of an aliphatic hydrocarbon solvent having a boiling point of 150 ° C. or higher and 30 to 10% by mass of an aromatic hydrocarbon solvent having a boiling point of 150 ° C. or higher. The one-component undercoat paint composition according to claim 1 or 2.   The one-component undercoat paint composition according to any one of claims 1 to 3 is applied to the surface of concrete, mortar, flexible board, slate, gypsum board, calcium silicate board, ALC board, or extruded board. The painting method. A coating method comprising applying the one-component undercoat paint composition according to any one of claims 1 to 3 onto various deteriorated old paint films.