JP4674815B2 - Repair method of old paint film - Google Patents

Description

  The present invention relates to a method for repairing an old coating film, which is excellent in contamination resistance, weather resistance, warm water resistance (appearance, adhesion), anti-frost damage resistance, and has a self-cleaning ability. The present invention relates to a method for repairing an old coating film to form a repairable coating film.

  Existing exterior building materials and the like are damaged and peeled due to various causes, and are forced to be repaired. The main ones include peeling due to poor adhesion to the underlayer, cracking due to aging of the topcoat layer, blistering due to water, blistering due to solar heat, cracking due to stress, and the like. In addition, water-based and oil-based contaminants in the environment adhere and change color with the deterioration of the coating film applied to the surface of exterior building materials and the like. In recent years, rain streak contamination in which pollutants adhere in a streak pattern along the flow of rain has been regarded as a problem for reasons such as deterioration of the landscape.

  These contaminants are removed by high-pressure water cleaning, alkali cleaning using caustic soda or the like, acidic cleaning using an inorganic or organic acid, or repair cleaning using kelen or the like. Moreover, although the coating film discolored by the repair coating is almost close to the initial state, it has been impossible to prevent contamination for a long period of time due to the adhering contaminants again.

  In addition, after removing the contaminants on the old coating film, by applying a repair paint containing a partial hydrolysis condensate of silicate and / or organosilane, the silicate and / or organosilane part in the coating film formation process. Since the hydrolysis condensate migrates to the surface of the coating film and forms a phase-separated coating film, it is known to form a repair coating film that is resistant to contamination. However, in this technique, the surface transfer of the silicate and / or the partial hydrolysis condensate of organosilane to the coating film surface is not sufficient, and it has led to the formation of a coating film with excellent stain resistance required by the market. Not in.

Applying a repair agent containing a polyisocyanate compound on the old paint film, re-dissolving the old paint film, and curing it to form an undercoat layer and forming a topcoat layer thereon (For example, refer to Patent Document 1). However, the effect of preventing contamination cannot be expected so much for the coated film after repair. In addition, as a method for repairing a fluororesin-based coating film, there is a repair coating method in which a silane coupling agent-containing acrylic paint is applied on an old coating film and then a fluororesin-based paint is applied (see, for example, Patent Document 2). However, although the adhesion to the fluororesin-based old coating film and the weather resistance of the fluororesin-based coating film after repair can be expected, there is a concern that the effect on preventing pollution is low.
JP 2001-207652 A JP-A-10-298486

  The object of the present invention relates to a method for repairing an old coating film, and is to form an antifouling layer having excellent antifouling properties, weather resistance, hot water resistance (appearance and adhesion), frost damage resistance, and self-cleaning ability. An object of the present invention is to provide a method for repairing an old coating film for forming a repair coating film.

In accordance with the present invention, after removing all or part of one or both of the contaminants on the old paint film, the old paint film, applying at least one paint, and forming a paint film,
(A) As a top coat paint on the coating film,
(I) 100 parts by mass of a tetraalkoxysilane represented by the general formula (1) or a partial hydrolysis-condensation product thereof,
Si (OR ¹ ) _x (OR ² ) _(4-x) (1)
Wherein, ^{R 1} and ^{R 2} is an organic group having 1 to 8 carbon atoms, x is an integer of 0-4. ]
(Ii) 10 to 500 parts by mass of colloidal silica (in terms of solid content);
To a silica-containing condensation product obtained by hydrolytic condensation of
(Iii) As a diluent, a water- based paint using as a binder a polysiloxane solution obtained by adding 250 to 500000 parts by mass per 100 parts by mass of the component (i) is applied, and a top coat film Forming a step;
A method for repairing an old coating film characterized by comprising:

  By the repair method of the present invention, a repair coating film capable of forming an antifouling layer having excellent contamination resistance, weather resistance, warm water resistance (appearance and adhesion), frost damage resistance and self-cleaning ability. Can be formed.

  Hereinafter, embodiments of the present invention will be described in detail.

  If the repair method of the present invention is an old coating film containing a synthetic resin, a multilayer hard coating, a multilayer elastic coating, a waterproof multilayer coating, a thickening coating, a mastic coating, a moisture-permeable coating It can be used for any type of old paint film.

  The at least one kind of paint / coating applied after removing all or part of one or both of the contaminants on the old coating and the old coating is, for example, configured as follows. That is, it is formed from (B) undercoat film, (C) intermediate coat film, or (D) topcoat film (elastic or inelastic).

  (B) The undercoating film fills holes and steps in the outer wall surface, prevents inhalation of the intermediate coating material, prevents alkali leaching from the outer wall surface, and further prevents neutralization of the outer wall. Examples of resins used in undercoat paints include various conventionally known paints such as solvent-based or water-based resin paints such as acrylic resins, epoxy resins, urethane resins, vinyl resins, acrylic styrene resins, and epoxy / polyamine resins. Is mentioned.

  Further, (C) the intermediate coating film is formed of an intermediate coating material, and requires a certain degree of elasticity, moisture permeability, and the like. Examples of the resin used for the intermediate coating include various conventionally known coatings such as solvent-based or water-based coatings such as acrylic resin, acrylic urethane resin, urethane resin, and organic-inorganic composite resin. In some cases, the formation of the intermediate coating film (C) can be omitted.

  On the other hand, (D) the top coat film is a layer that requires crack followability, weather resistance, light resistance, water resistance, stain resistance, and the like. As an example of the resin used in the top coat, acrylic resin Various conventionally known paints such as solvent-type and water-based paints such as acrylic urethane resin, urethane resin, fluororesin, organic-inorganic composite resin, and silicone resin can be used.

  Various additives are contained in the paint for forming the (B) undercoat film, (C) intermediate coat film, and (D) topcoat film. Examples of additives include organic and inorganic color pigments, extender pigments and rust preventive pigments, aggregates such as silica sand and shirasu balloons, other antifoaming agents, plasticizers, rust preventives, preservatives, plasticizers, dispersions In the case of an aqueous emulsion, an antifreezing agent and a pH adjuster may be mentioned, for example, various additives such as an agent, an ultraviolet absorber, a light stabilizer, an anti-settling agent, and a thickener.

  The (B) undercoat film, (C) intermediate coat film, (D) the top coat film, depending on the case, (B) undercoat film, (C) intermediate coat film, or (D ) The formation of one or two types of coatings selected from top coatings can be omitted.

  (A) As a component of the coating material forming the lower layer of the topcoat coating film, a compound having a Si-OR group (R is a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms) is preferably a coating film forming component. It is desirable to use a paint containing 0.1 to 50% by mass in terms of (A) the adhesion of the topcoat paint to the coating film is better.

  Examples of the paint containing a compound having a Si-OR group (R is a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms) include hydrolyzable silyl group-containing vinyl paints, organopolysiloxane paints, And silane coupling agent-containing paints.

(A) The top coat paint contains silica obtained by hydrolyzing and condensing (i) the tetraalkoxysilane represented by the general formula (1) or a partially hydrolyzed condensate thereof and (ii) colloidal silica. (Iii) A polysiloxane solution obtained by adding only water as a diluent to the condensation product is used as a binder.

  Below, each structural component of (A) topcoat paint in this invention is demonstrated.

(I) Component (i) The component is a tetraalkoxysilane represented by the general formula (1) or a partially hydrolyzed condensate thereof.

Si (OR ¹ ) _x (OR ² ) _(4-x) (1)
Wherein, ^{R 1} and ^{R 2} is an organic group having 1 to 8 carbon atoms, x is an integer of 0-4. ]

In the above formula, preferred examples of the organic group as R ¹ and R ² include an alkyl group, a cycloalkyl group, and an aryl group. R ¹ and R ² may be the same or different.

  Here, the alkyl group may be linear or branched. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, Examples thereof include alkyl groups such as heptyl group and octyl group. Preferred alkyl groups are alkyl groups having 1 to 4 carbon atoms.

  Preferred examples of the cycloalkyl group include a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and the like.

  Examples of the aryl group include a phenyl group.

  Specific examples of the tetraalkoxysilane represented by the above formula (1) include, for example, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, triethoxybutoxysilane and the like. These tetraalkoxysilanes can be used alone or as a mixture of two or more.

The component (i) may be the partially hydrolyzed condensate of tetraalkoxysilane described above. The polystyrene-converted weight average molecular weight of the condensate is preferably 300 to 5,000, particularly 500 to 3,000. By using such a molecular weight condensate, a coating film having good adhesion can be obtained without deteriorating storage stability. Moreover, the partial hydrolysis-condensation product of tetraalkoxysilane is suitable to have one or more, preferably 3 to 30, —OH groups, —OR ¹ groups, or —OR ² groups bonded to silicon atoms. .

  Specific examples of such condensates include commercially available products such as ethyl silicate 40 and ethyl silicate 56 (both manufactured by Colcoat).

Component (ii) As the component (ii) colloidal silica, silica particles dispersed in water or an organic solvent are preferably used. Colloidal silica is usually a type in which approximately spherical silica particles having an average particle diameter of 5 to 100 nm, preferably 10 to 30 nm are dispersed, and the silica particles are chained to have a thickness of about 5 to 50 nm and a length of about 40 to 400 nm. There are a type in which the particles are aggregated and dispersed in a solution, a type in which silica particles having an average particle diameter of 5 to 50 nm are aggregated in a ring and dispersed in the solution, and the like. Also, different types can be mixed and used.

  Silica particles in which approximately spherical silica particles are dispersed in water can be easily obtained as a commercial product. Such colloidal silica is, for example, SNOWTEX-20, SNOWTEX manufactured by Nissan Chemical Industries, Ltd. Preferred examples include -O, Snowtex-C, Snowtex-S, and Adelite AT-20, AT-20N, AT-20A, AT-300 manufactured by Asahi Denka Kogyo Co., Ltd.

  Colloidal silica in which almost spherical silica particles are dispersed in an organic solvent is, for example, lower alcohols such as methanol, ethanol, isopropanol, n-butanol, isobutanol; ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monoacetate. Ethylene glycol derivatives such as ethyl ether; diethylene glycol derivatives such as diethylene glycol and diethylene glycol monobutyl ether; ketones such as acetone and methyl ethyl ketone; and silica particles dispersed in organic solvents such as toluene, xylene, ethyl acetate, and butyl acetate This organic solvent-dispersed colloidal silica can also be easily obtained as a commercial product. For example, Snowtex MA-ST-M, I manufactured by Nissan Chemical Industries, Ltd. A-ST, EG-ST, EG-ST-ZL can be preferably used.

  The chain colloidal silica is dispersed in water or the above-mentioned organic solvent, and can be easily obtained as a commercial product. Specific examples thereof include, for example, Snowtex-UP manufactured by Nissan Chemical Industries, Ltd. SNOWTEX-OUP (above, water dispersion), SNOWTEX MA-ST-UP, IPA-ST-UP (above, organic solvent dispersion) and the like are preferable.

  Examples of the commercially available cyclic colloidal silica include SNOWTEX-PS-SO, SNOWTEX-PS-M, SNOWTEX-PS-L and the like manufactured by Nissan Chemical Industries, Ltd.

  The component (ii) is used to improve the curability and stain resistance of the coating film, and the blending amount is 10 to 500 parts by mass in terms of solid content with respect to 100 parts by mass of the component (i). 20 to 300 parts by mass is preferable. (Ii) If the blending amount of the component is less than the above range, the effect of improving the curability and stain resistance of the coating film is small, and conversely if too large, the mixing stability, the crack resistance of the coating film, etc. Tend to decrease.

  The pH of the dispersion of colloidal silica (component (ii)) is preferably 6 or less, and more preferably 3 to 5. If the pH of the colloidal silica dispersion is greater than 6, the storage stability of the resulting polysiloxane solution tends to be insufficient.

  In the reaction between the component (i) and the component (ii), if the component (ii) is dispersed in water, the hydrolysis condensation reaction can be performed using the water in the component (ii). . On the other hand, when the component (ii) is dispersed in an organic solvent, the hydrolysis condensation reaction can be performed by adding water in which the component (i) can be hydrolyzed by 50% or more. Moreover, it is preferable to add acetic acid, acids, such as hydrochloric acid, nitric acid, formic acid, or basic compounds, such as ammonia and an amine compound, as a catalyst for promoting reaction.

  The hydrolysis or partial condensation reaction is usually performed at 40 to 80 ° C., preferably 45 to 65 ° C., for example, for 2 to 15 hours. In the presence of a catalyst, the reaction is performed at room temperature. Is also possible.

About (iii) component (iii) Only a water is added as a diluent to the silica containing condensation product of (i) component and (ii) component obtained as mentioned above, and a polysiloxane solution is obtained. .

  (Iii) As water used as a diluent, pure water, distilled water, ion exchange water, tap water, or the like can be used.

  (Iii) The compounding quantity of a component is 250-500000 mass parts per 100 mass parts of (i) component, Preferably, 500-100,000 mass parts is suitable. When the blending amount of the component (iii) is less than the above range, a uniform coating film is difficult to obtain, and conversely when it is too much, the stability of the obtained polysiloxane solution tends to be inferior.

About (iv) Component As needed, as (iv) component, the surfactant from which the surface tension of 0.01 mass% aqueous solution becomes 40 dyn / cm (25 degreeC) or less can be used. For the purpose of improving the appearance of the coating film of the polysiloxane solution obtained as described above, the component (iv) is added in an amount of 0.001 to 3% by mass in terms of solid content in the (A) top coat paint. Is preferred. In addition, when the amount exceeding 3% by mass is used, the appearance of the coating film and the water resistance of the coating film tend to be inferior. If the surface tension of the aqueous solution having a concentration of component (iv) of 0.01% by mass is larger than 40 dyn / cm, a uniform coating film cannot be obtained, and an uneven coating film appearance tends to be obtained.

  (Iv) As the surfactant, for example, an anionic or nonionic surfactant can be used. Specific examples thereof include, for example, Neugen ET-143, ET-135 (Daiichi Kogyo Seiyaku Co., Ltd.), Perex NB-L (Kao Co., Ltd.), Florard FC4430 (Sumitomo 3M Co., Ltd.) Polyflow KL-600 (manufactured by Kyoei Chemical Co., Ltd.), Surflon S-111, S-141 (manufactured by Seimi Chemical Co., Ltd.) and the like are preferred, and a fluorine-based surfactant is particularly preferred.

  In the thus obtained (A) topcoat paint, the heating residue after drying at 150 ° C. for 30 minutes is usually 0.01 to 40% by mass. In order to obtain a uniform coating film, From the reason that the stability of the A) top coat paint is sufficient, it is preferable that the heating residue of the (A) top coat paint is 0.1 to 10% by mass.

  The surface tension of the (A) topcoat paint used in the present invention is preferably 50 dyn / cm (25 ° C.) or less, more preferably 45 to 15 dyn / cm (25 ° C.). If it is higher than 50 dyn / cm (25 ° C.), it is difficult to form a uniform coating film, and sufficient coating film performance cannot be exhibited.

  The (A) topcoat paint used in the present invention contains a polysiloxane solution comprising the hydrolysis condensation reaction product of (i) component and (ii) component described above and (iii) a diluent. However, if necessary, in order to improve the coating film properties, coloring, etc., fillers, dyes, curing agents, and further various additives such as curing accelerators, thickeners, pigment dispersants, etc. May be blended.

  As the filler, for example, various pigment extender pigments such as talc, barium carbonate, calcium carbonate, barium sulfate, bentonite, titanium oxide, carbon black, Bengala, and lithopone, and colored pigments can be used. The blending amount of the filler is 0 to 70% by mass, preferably 0 to 50% by mass in the solid content of the coating composition.

  Examples of the curing agent include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl)- γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ-aminopropylmethyldiethoxysilane, N-cyclohexyl-γ-aminopropyltrimethoxysilane, N-cyclohexyl-γ-aminopropyltriethoxy Having an amino group in the molecule such as silane, γ- (2-aminoethyl) -aminopropyltrimethoxysilane, γ- (2-aminoethyl) -aminopropylmethyldimethoxysilane, γ-anilinopropyltrimethoxysilane, Alkoxysilane capable of hydrolytic condensation reaction and γ-glycidoxypropyl Trimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriisopropenyloxysilane, γ- Hydrolysis condensation reaction having an epoxy group such as an adduct of glycidoxypropyltriiminooxysilane, β- (3,4-epoxycyclohexyl) ethylmethyldimethoxysilane, γ-isocyanatopropyltriisopropenyloxysilane and glycidol Possible alkoxysilanes and the like are mentioned.

  Typical examples of the curing accelerator include organic tin compounds such as tin octylate, dibutyltin dilaurate, dibutyltin dimaleate, and tributyltin laurate, and amine compounds such as ethylenediamine, diethylenetriamine, piperidine, phenylenediamine, and triethylamine. In particular, organotin compounds are effective.

  As the base material with the old paint film, for example, for inorganic ceramics base materials, concrete, iron, aluminum and other metal base materials such as buildings, civil engineering structures, etc. Applicable.

  The methods for removing contaminants on the old paint film include high-pressure water cleaning, alkali cleaning such as caustic soda, acidic cleaning using inorganic acid or organic acid, cleaning using bleach such as perchloric acid, repair cleaning using kelen, etc. Etc.

  Examples of methods for removing the old paint film include various conventionally known substrate preparation methods such as blasting and keren.

<Repair method of old paint film>
At least one kind of paint to be applied after removing all or part of one or both of the contaminants on the old paint film and the old paint film is (B) undercoat paint, (C) intermediate paint, or (D) It is a top coating, and the coating means is a dry film by a single coating by a conventional method such as air spray, airless spray, shower coating, dip coating, brush coating or roll coating. A coating film having a thickness of 1 to 100 μm and a coating of 2 to 4 μm can be formed by 2 to 4 coatings, and the coating film can be formed by drying at room temperature.

  (A) The coating means of the top coat paint is a dry film thickness of 1 to 1 by a conventional method such as air spray, airless spray, shower coat, dip paint, brush paint, roll paint, etc. A coating film of 2 to 150 μm can be formed by coating 50 μm and 2-3 times, and the coating film can be formed by drying at room temperature.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, “parts” and “%” are expressed on a mass basis unless otherwise specified.

"Production Example 1"
A reactor equipped with a reflux condenser and a stirrer is charged with 200 parts of methanol, then (i) 100 parts of tetraethoxysilane, and (ii) isopropanol-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Ltd., IPA- ST: Solid content 30%, pH 3.2) 230 parts were added and mixed, then, with stirring, a mixed solution of 250 parts of ion-exchanged water and 6 parts of 0.1 N hydrochloric acid aqueous solution was added, After reacting for a period of time, (iii) 1200 parts of ion exchange water was added and cooled to room temperature to obtain a polysiloxane solution A (solid content 5%) having a surface tension of 25 dyn / cm.

"Production Example 2"
A reactor equipped with a reflux condenser and a stirrer is charged with 200 parts of methanol, then (i) 100 parts of tetramethoxysilane, and (ii) isopropanol-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Ltd., IPA- ST: Solid content 30%, pH 3.2) 100 parts were added and mixed, then, with stirring, a mixed solution of 250 parts of ion-exchanged water and 6 parts of 0.1N hydrochloric acid aqueous solution was added, and at 60 ° C. for 3 hours. After the reaction, (iii) 750 parts of ion exchange water was added and cooled to room temperature to obtain a polysiloxane solution B (solid content 5%) having a surface tension of 26 dyn / cm.

"Production Example 3"
In a reactor equipped with a reflux condenser and a stirrer, (i) 100 parts of tetraethoxysilane was added, and then (ii) water-dispersed colloidal silica (Nissan Chemical Industries, Snowtex-O; solid) After adding and mixing 150 parts (min 20%, pH 3.8), with stirring, a mixture of 250 parts of ion-exchanged water and 6 parts of 0.1N aqueous hydrochloric acid was added and reacted at 60 ° C. for 3 hours. Thereafter, (iii) 70 parts of propylene glycol monomethyl ether and 600 parts of ion exchange water were added and cooled to room temperature to obtain a polysiloxane solution C having a surface tension of 45 dyn / cm (solid content 5%).

"Production Example 4"
A reactor equipped with a reflux condenser and a stirrer is charged with 200 parts of methanol, and then (i) 100 parts of tetraethoxysilane and (ii) water-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Snowtex) -O; 500 parts of solid content 20%, pH 3.8) was added and mixed, and then with stirring, a mixture of 250 parts of ion-exchanged water and 6 parts of 0.1N aqueous hydrochloric acid was added, After reacting for a period of time, (iii) 100 parts of dipropylene glycol monomethyl ether and 1700 parts of ion-exchanged water were added and cooled to room temperature to obtain a polysiloxane solution D (solid content 5%) having a surface tension of 40 dyn / cm.

"Production Example 5"
A reactor equipped with a reflux condenser and a stirrer is charged with 200 parts of methanol, then (i) 100 parts of tetraethoxysilane, and (ii) isopropanol-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Ltd., IPA). -ST; solid content 30%, pH 3.2) After adding 1000 parts and mixing, with stirring, a mixture of 250 parts of ion-exchanged water and 6 parts of 0.1N hydrochloric acid aqueous solution was added, After reacting for a period of time, (iii) 65,000 parts of ion exchange water was added and cooled to room temperature to obtain a polysiloxane solution E (solid content 0.5%) having a surface tension of 32 dyn / cm.

"Production Example 6"
In a reactor equipped with a reflux condenser and a stirrer, 100 parts of methanol was added, and then (i) 100 parts of tetraethoxysilane was added and mixed. After adding 2.5 parts of a normal hydrochloric acid aqueous solution and reacting at 60 ° C. for 3 hours, (iii) adding 450 parts of ion-exchanged water, cooling to room temperature, and a polysiloxane solution F having a surface tension of 30 dyn / cm (Solid content 5.2%) was obtained.

"Production Example 7"
A reactor equipped with a reflux condenser and a stirrer is charged with 50 parts of methanol, and then (ii) water-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Snowtex-O; solid content 20%, pH 3. 8) Add 50 parts and mix, then, (iii) Add 100 parts of ion exchanged water with stirring and stir at room temperature for 3 hours to obtain a silica dispersion solution G (solid content 5%) with a surface tension of 70 dyn / cm. Obtained.

"Production Example 8"
A reactor equipped with a reflux condenser and a stirrer was charged with 78 parts of ion-exchanged water, and then (ii) water-dispersed colloidal silica (manufactured by Nissan Chemical Industries, Snowtex-O; solid content 20%, pH 3.8) 20 parts were added and mixed, and then, while stirring, (i) 2 parts of tetraethoxysilane was added and stirred at room temperature for 3 hours to obtain a silica mixed solution H having a surface tension of 37 dyn / cm (solid content: 4). 7%).

[Film performance evaluation test]
Preparation of coating film performance test plate: Building exterior wall base material (old coating film), which was coated with acrylic silicon paint as a top coat and left outdoors for 8 years and was contaminated with rain streaks, was treated with an acid treatment with a citric acid solution and washed with water. After removing the pollutant, a coating amount of water-based Mighty Sealer Multi (manufactured by Dainippon Paint Co., Ltd., a cation-type specially modified acrylic resin sealer) as an undercoat on the surface is 100 to 130 g / m ² (wet mass). It was painted by spraying and dried in an atmosphere at 20 ° C. for 24 hours. Next, as an intermediate coating material, DNT view silicon intermediate coating (manufactured by Dainippon Paint Co., Ltd., intermediate coating for one-component reaction-curable water-based silicone resin coating) is applied so that the coating amount becomes 100 to 140 g / m ² (wet mass). It was painted by spraying and dried in an atmosphere at 20 ° C. for 24 hours. Next, DNT view silicon (manufactured by Dainippon Paint Co., Ltd., one-component reaction-curable water-based silicone resin paint) is applied by spray so that the coating amount is 100 to 140 g / m ² (wet mass), It was dried in an atmosphere at 20 ° C. for 24 hours.

Next, a top coat paint was prepared with the formulation shown in Table 1, and spray-coated with a spray so that the coating amount was 20 to 30 g / m ² (wet mass) and the film thickness was 5 μm. After drying at room temperature for 7 days, each test of the appearance, warm water resistance, stain resistance, weather resistance, and frost damage resistance of the obtained coating film was conducted, and the results are shown in Table 1.

  The surface tension of the topcoat paint and the measurement of the heating residue were performed as follows.

<Method for measuring surface tension>
The surface tension was measured at 25 ° C. using a surface tension meter (CBUP-A5 type) manufactured by Kyowa Interface Science Co., Ltd.

<Measurement method of heating residue>
For the heating residue, weigh accurately about 3 grams of the topcoat paint in an aluminum cup, weigh the weight after drying for 30 minutes using an oven at 150 ° C, and calculate from the weight of the residue relative to the original weight. Minutes (%) were determined.

  In addition, the test method and evaluation criteria were performed based on the following.

<Appearance of coating film>
The appearance of the coating film before the test was visually evaluated as follows.
○… Good (transparent film)
×… Bad (cloudy film)

<Hot water resistance: Appearance>
The appearance of the coating film after the coated plate produced as described above was immersed in warm water at 80 ° C. for 3 hours was visually judged as follows during the immersion and after the coating film was dried.
◎ ... No change during soaking and after drying coating ○: Slight whitening during soaking, but no change after drying coating △ ... Whitening during soaking, loss of gloss after drying coating, whitening, etc. X ... Slightly whitening during soaking, and significant changes such as loss of gloss and whitening after drying the film

<Hot water resistance: adhesion>
After dipping the coated plate in warm water of 80 ° C. for 3 hours, using a cutter knife on the coating film of the removed coated plate, make 25 gobangs at intervals of 2 mm, apply cellophane adhesive tape, peel off, The number of eyes without film peeling was counted.

<Contamination resistance>
24 hours after drawing with red and black magic inks on the coated plate, it was wiped off with a cloth moistened with n-butanol, and its decontamination property was visually judged as follows.
◎… Complete removal ○… Slightly slight contamination △… Slight contamination ×… Severe contamination

<Weather resistance>
The weather resistance was determined as follows using a sunshine weather-ometer for 3000 hours.
○: No change in coating film appearance, gloss retention of 95% or more Δ: Minor change in coating film appearance, gloss retention of 80-94%
X: Significant change in coating film appearance, gloss retention less than 80%

<Frost resistance>
The frost damage resistance of 40 cycles was measured by ASTM-C666A method, and visually judged as follows.
◎… No occurrence of cracks ○… Generation of very slight cracks △… Occurrence of cracks or partial peeling of coating film ×… Significant cracking or peeling of coating film

１）アニオン系界面活性剤「ペレックスＮＢ−Ｌ」（花王（株）製）、有効成分３５質量％、表面張力３８ｄｙｎ／ｃｍ（２５℃、０．０１質量％水溶液）
表１より明らかな通り、ポリシロキサン溶液Ａ〜Ｅを含有する塗料組成物を使用した実施例１〜７は、優れた塗膜性能を有していた。

1) Anionic surfactant “Perex NB-L” (manufactured by Kao Corporation), active ingredient 35 mass%, surface tension 38 dyn / cm (25 ° C., 0.01 mass% aqueous solution)
As is clear from Table 1, Examples 1 to 7 using the coating composition containing the polysiloxane solutions A to E had excellent coating performance.

  On the other hand, in the paint using the polysiloxane solution F not subjected to the condensation reaction with the component (ii) of Comparative Example 1, the stain resistance, weather resistance and frost damage resistance were poor. In the paint using the silica dispersion solution G not subjected to the condensation reaction with the component (i) of Comparative Example 2, the coating film appearance, warm water resistance (appearance, adhesion), weather resistance and frost damage resistance were very poor. In addition, in the paint using the silica mixed solution H obtained by simply mixing the components (i) and (ii) of Comparative Example 3, the coating film appearance, warm water resistance (appearance, adhesion), and contamination resistance are very poor. It was.

  The method for repairing an old coating film of the present invention is useful as a means for forming a coating film having excellent resistance to contamination, weather resistance, warm water resistance (appearance and adhesion), and frost damage resistance on the surface of the old coating film. is there.

Claims (4)

After removing all or part of one or both of the contaminants on the old paint film and the old paint film, applying at least one paint to form a paint film,
(A) As a top coat paint on the coating film,
(I) 100 parts by mass of a tetraalkoxysilane represented by the general formula (1) or a partial hydrolysis-condensation product thereof,
Si (OR ¹ ) _x (OR ² ) _(4-x) (1)
Wherein, ^{R 1} and ^{R 2} is an organic group having 1 to 8 carbon atoms, x is an integer of 0-4. ]
(Ii) 10 to 500 parts by mass of colloidal silica (in terms of solid content);
To a silica-containing condensation product obtained by hydrolytic condensation of
(Iii) As a diluent, a water- based paint using as a binder a polysiloxane solution obtained by adding 250 to 500000 parts by mass per 100 parts by mass of the component (i) is applied, and a top coat film Forming a step;
A method for repairing an old paint film characterized by comprising:   The surface tension of the (A) top coat paint is 50 dyn / cm (25 ° C.) or less. The method for repairing an old coating film according to claim 1 or 2 , wherein the (A) top coat paint has a heating residue at 150 ° C for 30 minutes of 0.1 to 10% by mass. Further, as the component (iv), a surfactant having a surface tension of an aqueous solution having a concentration of 0.01% by mass of 40 dyn / cm (25 ° C.) or less is added in an amount of 0.001 to 3% by mass in the (A) topcoat paint ( The repair method of the old coating film in any one of Claims 1-3 contained (in solid content conversion).