JP2009006292A - Method for forming multilayer coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a multilayer coating film, in which skinning and coagulation humps can be restrained and/or prevented and to provide a water-based metallic base coating material composition applicable to the method for forming the multilayer coating film. <P>SOLUTION: The method for forming the multilayer coating film comprises the steps of forming an intermediate coating film, a metallic base coating film and a clear coating film successively on the object to be coated. The water-based metallic base coating material composition for forming the metallic base coating film contains an acrylic emulsion resin, a melamine resin curing agent, a glorious pigment, and a surfactant which contains a reaction product of a nonreducing disaccharide or trisaccharide (a1) with 2-4C alkylene oxide (a2) and further contains an alcohol-based organic solvent, which has 0.01-5.0 mass% solubility in water and 160-200°C boiling point, and/or a glycol ether-based organic solvent, which has 0.01-5.0 mass% solubility in water and 205-240°C boiling point, respectively by 5-45 mass% of the mass of the resin solid content in the water-based metallic base coating material composition. The water-based metallic base coating material composition is used in the method for forming the multilayer coating film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for forming a multilayer coating film and a water-based metallic coating composition applicable to the method.

  In order to prevent sedimentation of pigments and solids contained in the aqueous metallic coating composition, the coating composition 1 is stirred by the stirring means 3 in the circulation tank 2 as shown in FIG. The circulation pump 4 circulates between the circulation tank 2 and the painting means 6. However, since the circulation tank 2 is not hermetically sealed, a phenomenon called “skinning” occurs in the paint, and the film produced by the skinning is mixed into the paint composition, causing defects in the coating film obtained after painting. Are known. Skinning occurs in the part where the coating composition in the circulation tank 2 comes into contact with air, in the same way that warmed milk has a thin skin on its surface as the temperature decreases. It may be resolved when mixed, but it remains without being resolved. The coating film formed by skinning can usually be removed by physical means such as filtration, but the filtration device 8 or 9 may become clogged or may be difficult to remove completely, which is complicated and uneconomical. .

  In addition, a phenomenon called agglomeration may occur while the coating composition circulates between the circulation tank 2 and the coating means 6. Like the skinning, this phenomenon is caused by the coating composition being externally moved up and down by the coating composition surface during application of the coating composition while the coating composition is circulating in the circulation system, particularly in the circulation tank 2. This is because the components contained in the coating composition are aggregated to form a solid lump by contacting with the air or with bubbles in the coating. Although the aggregates can be removed by physical means such as filtration as described above, the filtration device 8 or 9 may be clogged or may be difficult to remove completely, which is complicated and uneconomical.

In this field, a container endothelium-preventing method [Japanese Patent Laid-Open No. 11-228874 (Patent Document 1)] and generation of a large amount of foam when a water-based paint for forming a lightweight thick film containing resin foam particles is stored in a container. Water-based paints that can solve the problem of skin, skinning, armpits, build-up, etc., and have good cleaning properties, particularly paints suitable for can coating [Japanese Patent Laid-Open No. 11-349894 (Patent Document 2)] are known However, it is not related to water-based metallic paint compositions, and therefore, there is a need in the art to develop a method and a water-based metallic paint composition that can more easily and economically eliminate skinning and cohesiveness of water-based metallic paint compositions. It is rare.
JP 11-228874 A JP 11-349894 A

  An object of the present invention is to provide a method for forming a multilayer coating film capable of suppressing and / or preventing skinning and cohesion and a water-based metallic coating composition applicable to the method.

  As a result of earnest research, the present inventors contain a reaction product of a non-reducing disaccharide or trisaccharide (a1) and a C2-C4 alkylene oxide (a2) in the aqueous metallic coating composition. It has been found that the addition and addition of a surface active agent can suppress and / or prevent skinning and aggregation of coating compositions. Accordingly, the present invention provides the following.

A method for forming a multi-layer coating film in which an intermediate coating film, a metallic base coating film, and a clear coating film are sequentially formed on an object to be coated,
A water-based metallic base coating composition for forming the metallic base coating film,
Acrylic emulsion resin,
Melamine resin curing agent,
Luster pigment,
A surfactant containing a reaction product of a non-reducing disaccharide or trisaccharide (a1) and an alkylene oxide (a2) having 2 to 4 carbon atoms, and a solubility in water of 0.01 to 5.0% by mass An alcohol organic solvent having a boiling point of 160 to 200 ° C. and / or a glycol ether organic solvent having a solubility in water of 0.01 to 5.0% by mass and a boiling point of 205 to 240 ° C. 5 to 45% by mass based on the mass of resin solids in the paint, respectively
A method for forming a multilayer coating film, comprising:

  The acrylic emulsion resin emulsion-polymerizes an α, β-ethylenically unsaturated monomer mixture having an acid value of 3 to 50 mgKOH / g containing 65% by mass or more of (meth) acrylic acid ester having 1 or 2 carbon atoms in the ester part. A method for forming the multilayer coating film as described above.

  The surfactant is produced by a reaction between 1 mol part of a non-reducing disaccharide or trisaccharide (a1) and 47 to 100 mol parts of an alkylene oxide (a2) having 2 to 4 carbon atoms, The method for forming the multilayer coating film.

  The method for forming a multilayer coating film according to claim 1, wherein a mass ratio of the alcohol organic solvent / the glycol ether organic solvent is 1/1 to 3/1.

  An aqueous metallic base coating composition for use in the method for forming a multilayer coating film.

  According to the present invention, it is possible to suppress and / or prevent skinning and aggregation in the aqueous metallic coating composition, and it is possible to form a multilayer coating film having an excellent appearance.

  The present invention relates to a method for forming a multilayer coating film in which an intermediate coating film, a metallic base coating film, and a clear coating film are sequentially formed on an object to be coated. The multi-layer coating film forming method of the present invention is characterized by components contained in an aqueous metallic base coating composition capable of forming a metallic base coating film, in particular, a surfactant. Can be suppressed and / or prevented. First, the coating material, the intermediate coating composition capable of forming an intermediate coating film, the aqueous metallic base coating composition capable of forming a metallic base coating film, and the clear coating composition capable of forming a clear coating film will be described in detail. To do.

Coating material The coating material used in the present invention is not particularly limited, and examples thereof include metal products, plastic products, and foams thereof.

  Examples of the material for the metal product include metals such as iron, steel, copper, aluminum, tin, and zinc, and alloys containing these metals. Specific examples of metal products include automobile bodies such as passenger cars, trucks, motorcycles, and buses, and parts for automobile bodies. These metal products are particularly preferably those that have been previously subjected to chemical conversion treatment with phosphate, chromate or the like.

  In addition, as the article to be coated, metal products (particularly metal products having a metal surface and castings) are particularly preferable because electrodeposition coating is possible as the undercoat. There is no particular limitation on the electrodeposition coating of the electrodeposition coating that may be formed as an undercoat coating, and examples thereof include cationic and anionic electrodeposition coatings. From the viewpoint, a cationic electrodeposition paint is preferred.

  Examples of the material for the plastic product include polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, and polyamide resin. Specific examples of plastic products include automobile parts such as spoilers, bumpers, mirror covers, grills, and door knobs. Further, these plastic products are preferably washed with pure water and / or a neutral detergent. Moreover, the primer coating for enabling electrostatic coating may be given.

Intermediate coating composition An intermediate coating film can be formed on the coating object. An intermediate coating composition is used for forming the intermediate coating film. This intermediate coating composition contains pigments such as a film-forming resin, a curing agent, various organic and inorganic color pigments and extender pigments.

  The film-forming resin contained in the intermediate coating composition is not particularly limited, and film-forming resins such as acrylic resin, polyester resin, alkyd resin, epoxy resin, and urethane resin can be used. Is used in combination with the curing agent mentioned in the water-based metallic base coating composition described later. From the viewpoints of various performances and costs of the obtained coating film, amino resins and / or (block) isocyanate resins are generally used as curing agents.

  As the pigment contained in the intermediate coating composition, the pigments mentioned in the description of the aqueous metallic base coating composition described later can be used in the same manner. Standardly, a gray-based intermediate coating composition containing carbon black and titanium dioxide as the main pigments, a so-called color intermediate coating composition that combines a set gray that matches the lightness of the top coat and various colored pigments. Can be used. The intermediate coating composition may further contain flat pigments such as aluminum powder and mica powder.

  In these intermediate coating compositions, in addition to the above-mentioned components, additives usually added to the coating, for example, surface conditioners, thickeners, antioxidants, UV inhibitors, antifoaming agents and the like are blended. It may be.

  The method for preparing the intermediate coating composition is not particularly limited, and the intermediate coating composition can be prepared according to a method known to those skilled in the art. A commercially available intermediate coating composition may also be used.

Aqueous metallic base coating composition Aqueous metallic base coating composition used in the method for forming a multilayer coating film of the present invention and capable of forming a metallic base coating film is an acrylic emulsion resin, a melamine resin curing agent, a pigment, and details below. Contains specific surfactants and specific alcohol-based organic solvents and / or glycol ether-based organic solvents, and significantly suppresses skinning and cohesion of water-based metallic paint compositions by specific surfactants And / or can be prevented. Hereinafter, each component contained in the water-based metallic base coating composition of the present invention will be described in detail.

Surfactant The aqueous metallic base coating composition of the present invention contains a reaction product of a non-reducing disaccharide or trisaccharide (a1) and an alkylene oxide (a2) having 2 to 4 carbon atoms as a surfactant. Contains a surfactant.

Reaction product of non-reducing disaccharide or trisaccharide [hereinafter sometimes abbreviated as compound (a1)] and alkylene oxide having 2 to 4 carbon atoms [hereinafter sometimes abbreviated as compound (a2)] As a thing, for example, the formula: {H- (OA) _n- } _m Q (1)
[Where:
Q is a reaction residue obtained by removing a hydrogen atom from m primary hydroxyl groups of a non-reducing disaccharide or trisaccharide (a1);
OA is an oxyalkylene group having 2 to 4 carbon atoms (a2),
n is an integer from 1 to 100;
m is an integer of 2 to 4,
m {H- (OA) _n- } may be the same or different,
The total number of OA (n × m) is 47-100]
The polyoxyalkylene compound (A) represented by these is mentioned.

  The reaction residue (Q) is a reaction residue obtained by removing a hydrogen atom from m primary hydroxyl groups of a non-reducing disaccharide or trisaccharide (a1). The secondary hydroxyl group seems to be included in the reaction residue as it is without participating in the reaction. As the non-reducing disaccharide, any non-reducing disaccharide can be used without limitation, and examples thereof include sucrose (saccharose), isosaccharose, trehalose, and isotrehalose. Moreover, as a non-reducing trisaccharide, if it is a non-reducing trisaccharide, it can be used without a restriction | limiting, A gentianose, raffinose, a meletitose, a planteose, etc. are mentioned. Of these, sucrose, trehalose, gentianose, raffinose and planteose are preferable from the viewpoint of surface active ability (particularly surface tension reducing ability), more preferably sucrose and trehalose, from the viewpoint of supply ability and cost. Particularly preferred is sucrose.

  Examples of the oxyalkylene group (OA) having 2 to 4 carbon atoms include oxyethylene (eo), oxypropylene (po), oxybutylene (bo), and a mixture thereof. Of these, oxypropylene and oxybutylene are preferred, and oxypropylene is more preferred from the viewpoint of surface activity (particularly surface tension reducing ability).

The n (OA) may be the same or different. There is no restriction | limiting in the order (block shape, random shape, and these combination) of oxyalkylene group in {H- (OA) _n- }, and the number of kinds. Further, m {H- (OA) _n- } may be the same or different {for example, among m {H- (OA) _n- }, n is 0 for at least one of them. In addition, the type of oxyalkylene group and the number of n may be different. }.

Moreover, when (OA) of {H— (OA) _n —} contains an oxyethylene group and an oxypropylene group or / and an oxybutylene group, an end {hydrogen atom ( It is preferable that an oxypropylene and / or oxybutylene group is located in a portion close to H). That is, when an oxyethylene group is contained in this way, it is preferable that the oxyethylene group can be directly bonded to the reaction residue (Q).

Moreover, when (OA) of {H— (OA) _n —} includes a plurality of types of oxyalkylene groups, it is preferable to include a block-like one. Moreover, when oxyethylene is included, this content is preferably 20 to 1% by weight, more preferably 15 to 1% by weight, particularly preferably 10 to 1% based on the weight of {H— (OA) _n —} m. % By weight.

  47-100 are preferable, as for the total number (nxm) of OA in 1 molecule, More preferably, it is 50-95, Especially preferably, it is 55-90, Most preferably, it is 60-85. Within this range, the surface activity (particularly surface tension lowering ability) and water dispersibility tend to be further improved.

  n is preferably an integer of 1 to 100, more preferably an integer of 10 to 80, particularly preferably an integer of 15 to 60, most preferably from the viewpoints of surface activity (particularly surface tension reducing ability) and water dispersibility. Is an integer of 20-40.

  m is preferably an integer of 2 to 4, more preferably 2 or 3. Within this range, the surface activity (particularly surface tension lowering ability) and water dispersibility tend to be further improved.

In addition, the terminal hydroxyl group of the polyoxyalkylene compound (A) (that is, the terminal OH of the {H— (OA) _n —} moiety) is appropriately protected with an appropriate protecting group according to a method known to those skilled in the art. It may be protected.

  The hydroxyl-protecting group is not particularly limited as long as it is a hydroxyl-protecting group that can be usually used in the art. For example, an alkyl group having 1 to 3 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, and an isopropyl group). ), An alkenyl group having 3 carbon atoms (for example, allyl group, isoallyl group) and the like are preferable.

  When the compound (A) has a plurality of hydroxyl protecting groups, the protecting groups may be the same or different.

Preferable polyoxyalkylene compounds (A) represented by the general formula (1) include compounds represented by the following formulas (2) to (20). In addition, po represents an oxypropylene group, eo represents an oxyethylene group, bo represents an oxybutylene group, Q ¹ represents a sucrose reaction residue, Q ² represents a raffinose reaction residue, and Q ³ represents meletitol. Represents a reactive residue.

_{{H- (po) 19 -}} 3 Q 1 (2)
_{{H- (po) 20 -}} 3 Q 1 (3)
_{{H- (po) 25 -}} 3 Q 1 (4)
_{{H- (po) 28 -}} 3 Q 1 (5)
{H- (po) _30- } ₃ Q ¹ (6)
_{{H- (po) 25 - (} eo) 3 -} 3 Q 1 (7)
_{{H- (po) 27 - (} eo) 1 -} 3 Q 1 (8)
_{{H- (bo) 2 - (} po) 23 - (eo) 2 -} 3 Q 1 (9)
_{{H- (po) 17 -}} 2 Q 1 {- (po) 30 -H} (10)
{H- (po) _10- } ₂ Q ¹ {-(po) ₆₀ -H} (11)
{H- (eo) _2- } Q ¹ {-(eo) _3- (po) ₃₄ -H} ₂ (12)
_{{H- (po) 38 -}} 2 Q 1 H (13)
_{{H- (po) 20 - (} po 2 / eo 2) -} 3 Q 1 (14)
_{{H- (bo) 2 - (} po) 20 - (po 2 / eo 2) -} 3 Q 1 (15)
_{{H- (bo) 3 - (} po) 22 -} 3 Q 2 (16)
_{{H- (bo) 2 - (} po) 37 -} 2 Q 2 H (17)
_{{H- (po) 20 -}} 4 Q 3 (18)
_{{H- (po) 19 - (} eo) 2 -} 4 Q 3 (19)
{H- (bo) _2- (po) _24- } ₃ Q ³ H (20)

However, (po ₂ / eo ₂ ) represents that each of 2 moles of po and eo is randomly included.

  The terminal hydroxyl group of the compounds represented by the above formulas (2) to (20) may be appropriately protected with the hydroxyl-protecting group.

  Of these, the compound represented by the formula (3), (4), (5), (6), (9) or (18) is preferable, and the compound represented by the formula (4) is more preferable.

  When the reaction residue (Q) is a reaction residue of a non-reducing disaccharide {when the non-reducing disaccharide or trisaccharide (a1) is a non-reducing disaccharide}, the polyoxyalkylene compound (A) The cloud point (° C.) is preferably 25 to 40, more preferably 28 to 38, and particularly preferably 32 to 36. That is, in this case, the cloud point (° C.) of the compound (A) is preferably 25 or more, more preferably 28 or more, particularly preferably 32 or more, and preferably 40 or less, more preferably 38 or less, particularly preferably. Is 36 or less.

  Further, when the reaction residue (Q) is a reaction residue of a non-reducing trisaccharide {when the non-reducing disaccharide or trisaccharide (a1) is a non-reducing trisaccharide}, a polyoxyalkylene compound (A The cloud point (° C.) is preferably 25 to 55, more preferably 28 to 50, particularly preferably 30 to 47, and most preferably 33 to 45. That is, in this case, the cloud point (° C.) of the compound (A) is preferably 25 or more, more preferably 28 or more, particularly preferably 30 or more, most preferably 33 or more, and 55 or less is more preferable. Is 50 or less, particularly preferably 47 or less, and most preferably 45 or less.

  The cloud point is a physical property value that is a measure of the hydrophilicity / hydrophobicity of the surfactant. The higher the cloud point, the higher the hydrophilicity. ISO 1065-1975 (E), “ethylene oxide nonionic It is measured according to “Measurement method B” in “Surfactant-clouding point measurement method” (sample concentration 10% by weight method using 25% by weight aqueous solution of butyl diglycol). That is, a sample is put into a 25% by weight aqueous solution of butyl diglycol (3,6-oxadecyl alcohol: butanol EO2 molar adduct) so as to have a concentration of 10% by weight and dissolved uniformly (usually at 25 ° C. Dissolve, but if not, cool until clear liquid). Next, about 5 cc of this sample solution is taken into a test tube having an outer diameter of 18 mm, a total length of 165 mm, and a wall thickness of about 1 mm, and a thermometer with a diameter of about 6 mm, a length of about 250 mm, and a half degree scale is placed in the sample solution. While stirring, the sample solution is made cloudy by raising the temperature at 1.0 ± 0.2 ° C./min. Thereafter, while stirring, the sample solution is cooled at 1.0 ± 0.5 ° C./min to read the temperature at which the sample solution becomes transparent, and this is taken as the cloud point.

  The dynamic surface tension (25 ± 0.2 ° C., mN / m) of the 0.1 wt% aqueous solution of the polyoxyalkylene compound (A) is preferably 50 to 40 at 20 Hz, more preferably 48 to 40, particularly preferably. Is 45-40. Further, the difference in dynamic surface tension between 20 Hz and 0.05 Hz is preferably 12 mN / m or less, more preferably 10 mN / m or less, and particularly preferably 8 mN / m or less.

  The dynamic surface tension is determined by a dynamic surface tension automatic measuring machine based on the maximum bubble pressure method (for example, “Automatic / Dynamic Surface Tension Meter BP-D3” manufactured by Kyowa Interface Science Co., Ltd., “Cruth BP-2” manufactured by KRUSS Co., Ltd.). ), Aqueous solution temperature 25 ± 0.2 ° C., sample concentration: 0.1% by weight (dilution medium: deionized water), bubble generating gas: dry air (relative humidity 40 ± 5%), measurement time interval : Measured under conditions of 500 milliseconds. Further, the blank is adjusted (confirmed) so that the dynamic surface tension of deionized water is 73.0 to 72.0 mN / m at 20 to 0.05 Hz. The dynamic surface tension of 20 Hz means the surface tension after 1/20 (50 millisecond) after a new interface is formed, and the dynamic surface tension of 0.05 Hz means that a new interface is formed. Means the surface tension after 20 seconds.

  Further, when a new interface is formed with an aqueous solution containing a surfactant or the like, a certain amount of time is required for the surface tension to reach equilibrium. As a method for measuring the surface tension, the ring method and the plate method are well known, and these measuring methods measure the surface tension (static surface tension) that has reached equilibrium. On the other hand, dynamic surface tension is the surface tension at the moving gas-liquid interface, and is measured by a method called the Maximum Bubble Pressure Method or the Different Pressure Maximum Pressure Method (Differential eMaximum Bubble Pressure Method). When a simple interface (surface) is formed, the surface tension (mN / m) at that interface is measured in milliseconds {Journal of Chemical Society, pages 121, 858 1922; Journal of Colloid and Interface Science, 166, 6, 1944; and ASTM D3825-90 etc.}.

  The polyoxyalkylene compound (A) can be obtained by reacting a non-reducing disaccharide or trisaccharide (a1) with an alkylene oxide (a2) having 2 to 4 carbon atoms.

  In addition, the polyoxyalkylene compound (A) includes a polyoxyalkylene compound that can be produced by a reaction of a non-reducing disaccharide or trisaccharide (a1) and an alkylene oxide (a2) with an alkyl having 2 to 4 carbon atoms. By reacting a range halide {ethylene dichloride, propylene dichloride, butylene dibromide, etc.} with polyoxyalkylene glycol (2 to 4 carbon atoms of alkylene) (Williamson synthesis method), a part of the polyoxyalkylene compound is reacted. It can also be obtained by further bonding a polyoxyalkylene group only to a hydroxyl group (including the terminal hydroxyl group of the polyoxyalkylene group) {for example, the above formulas (10), (11), (12), (13), (13 17) or a compound represented by (20)}.

  The polyoxyalkylene compound (A) is a non-reducing disaccharide or trisaccharide (a1) partially esterified product (acyl group having 2 to 4 carbon atoms; acetyl, propanoyl, butanoyl, etc.) and alkylene oxide (a2). ) And then hydrolyzing to remove the acyl group and restore the primary hydroxyl group {for example, a compound represented by the above formula (13), (17) or (20) }.

  The reaction between the non-reducing disaccharide or trisaccharide (a1) and the alkylene oxide (a2) may be carried out in any form such as anionic polymerization, cationic polymerization or coordination anionic polymerization. These polymerization forms may be used alone or in combination according to the degree of polymerization. In any polymerization mode, alkylene oxide (a2) selectively reacts with primary hydroxyl group among all hydroxyl groups (primary hydroxyl group and secondary hydroxyl group) of non-reducing disaccharide or trisaccharide (a1). To do.

  A reaction catalyst can be used for the reaction between the non-reducing disaccharide or trisaccharide (a1) and the alkylene oxide (a2). As the reaction catalyst, a commonly used alkylene oxide addition reaction catalyst or the like can be used. Alkali metal or alkaline earth metal hydroxide (potassium hydroxide, rubidium hydroxide, cesium hydroxide, magnesium hydroxide, hydroxide) Calcium and barium hydroxide, etc.), alkali metal alcoholates (potassium methylate and cesium ethylate, etc.), alkali metal or alkaline earth metal carbonates (potassium carbonate, cesium carbonate, barium carbonate, etc.), C 3-24 And tertiary amines (trimethylamine, trioctylamine, triethylenediamine, tetramethylethylenediamine, etc.) and Lewis acids (stannic chloride, boron trifluoride, etc.) are used. Of these, alkali metal hydroxides and tertiary amine compounds are preferable, and potassium hydroxide, cesium hydroxide, and trimethylamine are more preferable.

  When a reaction catalyst is used, the amount used (% by weight) is preferably 0.05 to 2, more preferably 0.1 to 1, particularly preferably based on the total weight of the compounds (a1) and (a2). Is 0.2 to 0.6. That is, in this case, the use amount (% by weight) of the reaction catalyst is preferably 0.05 or more, more preferably 0.1 or more, particularly preferably 0.2 or more, based on the weight of the reaction product at the end of the reaction. It is preferably 2 or less, more preferably 1 or less, particularly preferably 0.6 or less. In addition, when using the amide demonstrated below as a reaction solvent, it is not necessary to use a reaction catalyst.

  Further, the reaction catalyst is preferably removed from the reaction product. As the method, an alkali adsorbent such as a synthetic aluminosilicate {for example, trade name: Kyoward 700, manufactured by Kyowa Chemical Industry Co., Ltd.} JP-A-53-123499), a method of dissolving in a solvent such as xylene or toluene and washing with water (JP-B-49-14359, etc.), a method using an ion exchange resin (JP-A-51-23211, etc.) And a method of filtering a carbonate formed by neutralizing an alkaline catalyst with carbon dioxide (Japanese Patent Publication No. 52-33000) and the like.

  As an indicator of the end point of the removal of the reaction catalyst, there is a CPR (Controlled Polymerization Rate) value described in JIS K1557-1970, and this value is preferably 20 or less, more preferably 10 or less, particularly preferably 5 or less, Most preferably, it is 2 or less.

  As the reaction vessel, it is preferable to use a pressure-resistant reaction vessel capable of heating, cooling and stirring. As the reaction atmosphere, it is preferable that the inside of the reaction apparatus is evacuated before introducing the alkylene oxide (a2) into the reaction system, or an atmosphere of a dry inert gas (such as argon, nitrogen and carbon dioxide). Moreover, as reaction temperature (degreeC), 80-150 are preferable, More preferably, it is 90-130. The reaction pressure (gauge pressure: MPa) is preferably 0.8 or less, more preferably 0.5 or less.

  The end point of the reaction can be confirmed by the following method. That is, when the reaction temperature is kept constant for 15 minutes, the reaction end point is set when the decrease in the reaction pressure (gauge pressure) is 0.001 MPa or less. The required reaction time is usually 4 to 12 hours.

  A reaction solvent can be used for the reaction between the non-reducing disaccharide or trisaccharide (a1) and the alkylene oxide (a2). As a reaction solvent, (1) no active hydrogen, (2) non-reducing disaccharide or trisaccharide (a1), alkylene oxide (a2), and polyoxyalkylene compound (A) are dissolved at the reaction temperature. However, it is preferable to satisfy the condition of (3) having a catalytic effect that does not require the addition of a reaction catalyst. Examples of such a reaction solvent include amides, and alkyl amides having 3 to 8 carbon atoms and heterocyclic amides having 5 to 7 carbon atoms can be used.

  Examples of the alkylamide include N, N-dimethylformamide (DMF), N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-N-propylacetamide, and 2- (dimethylamino) acetaldehyde dimethylacetal. It is done. Examples of the heterocyclic amide include N-methylpyrrolidone, N-methyl-ε-caprolactam, and N, N-dimethylpyrrolecarboxylic acid amide.

  Of these, alkylamides and N-methylpyrrolidone are preferred, more preferably DMF, N, N-dimethylacetamide, 2- (dimethylamino) acetaldehyde dimethylacetal and N-methylpyrrolidone, particularly preferably DMF and N-methylpyrrolidone. Most preferred is DMF.

  When a reaction solvent is used, the amount used (% by weight) is preferably from 50 to 200, more preferably from 60 to 180, particularly preferably from 70 to 150, based on the total weight of the compounds (a1) and (a2). is there. That is, in this case, the use amount (% by weight) of the reaction solvent is preferably 50 or more, more preferably 60 or more, particularly preferably 70 or more, and preferably 200 or less, based on the weight of the reaction product. More preferably, it is 180 or less, Especially preferably, it is 150 or less.

  When a reaction solvent is used, it is preferable to remove the reaction solvent after the reaction, more preferably to remove the reaction solvent under reduced pressure and, if necessary, an adsorbent. When distilling under reduced pressure, a method of distilling at 100 to 150 ° C. under a reduced pressure of 200 to 5 mmHg can be applied. Further, when removing using an adsorbent, a method of treating with an alkali adsorbent such as synthetic aluminosilicate {for example, trade name: Kyoward 700, manufactured by Kyowa Chemical Industry Co., Ltd.} can be applied. The addition amount of the alkali adsorbent is usually 0.1 to 10% by weight based on the weight of the polyoxyalkylene compound (A), the treatment temperature is 60 to 120 ° C., and the treatment time is 0.5 to 5 hours. is there. Subsequently, the alkali adsorbent can be removed by filtration using filter paper. The residual amount (% by weight) of the reaction solvent is preferably 0.1 or less, more preferably 0.05 or less, particularly preferably 0.01 or less, based on the weight of the polyoxyalkylene compound (A). is there. The residual amount of the reaction solvent can be determined by gas chromatography using an internal standard substance.

  The surfactant containing the reaction product of the non-reducing disaccharide or trisaccharide (a1) and the alkylene oxide (a2) having 2 to 4 carbon atoms used in the present invention is synthesized by the above synthesis method. However, a commercially available product may be used.

  Examples of the commercially available surfactants include SN-001S, SN-005S, SN Clean Act 82, SN Clean Act 830 (a sucrose polyether surfactant manufactured by San Nopco).

  As the surfactant used in the present invention, a reaction product of a non-reducing disaccharide or trisaccharide (a1) and an alkylene oxide (a2) having 2 to 4 carbon atoms, preferably a polyoxyalkylene compound (A) is essential. It may be contained as a component, may be a mixture of the compound (A), and may further contain other surfactants and / or solvents.

  Other surfactants include known surfactants, and nonionic surfactants, cationic surfactants, anionic surfactants and amphoteric surfactants can be used.

  Nonionic surfactants include alkylene oxide adducts of alkyl (carbon number 8-18) phenol (addition number 2-60), alkanols (carbon number 8-22) alkylene oxide adduct (addition number 3-50). , Polyhydric alcohol fatty acid ester having 5 to 8 carbon atoms, alkylene oxide adduct of alkylamine (4 to 18 carbon atoms) (addition number 1 to 45), alkylene oxide adduct of fatty acid amide (4 to 18 carbon atoms) ( Addition number 1 to 45), acetylene glycol (carbon number 14 to 16) and alkylene oxide adduct of acetylene glycol (addition number 1.3 to 30), polyoxyalkylene (oxyalkylene number 20 to 80) modified silicone (25 Kinematic viscosities at 300 ° C. to 100,000 centistokes) are preferably used.

  As the cationic surfactant, amine salts, quaternary ammonium salts, polyoxyalkylene addition type ammonium salts and the like are preferably used.

  Examples of the anionic surfactant include fatty acid salts having 8 to 18 carbon atoms, α-olefin sulfonates having 12 to 18 carbon atoms, alkyl (4 to 36 carbon atoms) benzenesulfonic acid and salts thereof, and 4 to 18 carbon atoms. Alkyl sulfate salts of 4 to 18 carbon atoms, alkyl ether sulfate salts of 4 to 18 carbon atoms, N-acylalkyl (6 to 18 carbon atoms) taurine salts, and alkyl sulfosuccinate salts of 10 to 22 carbon atoms.

  As the amphoteric surfactant, imidazolinium betaine, amide betaine, and betaine acetate are preferably used.

  As other surfactants, preferred product names available from the market are SN wet 123 and 970 (San Nopco), Lionol TDL-30, 50 and 70 (Lion), Ionette T- 80C, S-80, DO-600, etc. (manufactured by Sanyo Chemical Industries, Ltd.), Softanol 30, 30S, MES-5, etc. (manufactured by Nippon Shokubai Co., Ltd.), Surfynol 104, 440, Emblem Gem AD01, etc. (Air Products) Etc.).

  When other surfactant is contained, the content (% by weight) is preferably 40 to 1 based on the weight of the active ingredient of the above-mentioned surfactant, for example, the polyoxyalkylene compound (A). Preferably it is 30-5, Most preferably, it is 25-10. That is, in this case, the content (% by weight) of the other surfactant is preferably 1 or more, more preferably 5 or more, particularly preferably 10 or more, based on the weight of the active ingredient of the surfactant. It is preferably 40 or less, more preferably 30 or less, and particularly preferably 25 or less.

  As other solvents, water and various water-soluble organic solvents can be used. Examples of water include deionized water and distilled water. As a water-soluble organic solvent, a C1-C4 alcohol, a C3-C7 ketone, a C4-C6 ether, a C6-C8 ether ester, etc. are used. Examples of the alcohol include methanol, ethanol, and isopropanol, examples of the ketone include acetone, methyl ethyl ketone, and methyl isobutyl ketone, examples of the ether include ethyl cellosolve and butyl cellosolve, and examples of the ether ester include butyl cellosolve acetate. Etc.

  When the solvent is contained, the content (% by weight) is preferably 20 to 1, more preferably 17 to 3, particularly preferably 15 to 5, based on the weight of the active ingredient of the surfactant. That is, in this case, the content (% by weight) of the solvent is preferably 1 or more, more preferably 3 or more, particularly preferably 5 or more, and preferably 20 or less, based on the weight of the active ingredient of the surfactant. More preferably, it is 17 or less, and particularly preferably 15 or less.

  The content (% by mass) of the surfactant in the aqueous metallic base coating composition of the present invention is 1 to 20% by mass, preferably 2 to 12% by mass, based on the mass of the solid content of the aqueous metallic base coating composition. More preferably, it is 4-10 mass%.

  If the surfactant content (% by mass) is less than 1% by mass, there is a risk of problems such as deterioration of coating workability such as crackiness, and if it exceeds 20% by mass, the viscosity of the paint decreases. There is a risk of problems such as a decrease in painting workability.

  Since the surfactant has an action of maintaining the stability of the acrylic emulsion and the aqueous dispersion of the hydrophobic melamine resin, when the surfactant is added to a metallic paint composition, particularly an aqueous metallic base paint composition, the metallic paint Composition skinning and clumping can be suppressed and / or prevented.

Acrylic Emulsion Resin An acrylic emulsion resin can be obtained by emulsion polymerization of an α, β-ethylenically unsaturated monomer mixture.

  The α, β-ethylenically unsaturated monomer mixture contains 65% by weight or more of (meth) acrylic acid ester having 1 or 2 carbon atoms in the ester portion. When it is less than 65% by weight, the appearance of the resulting coating film is deteriorated. Examples of the (meth) acrylic acid ester having 1 or 2 carbon atoms in the ester part include methyl (meth) acrylate and ethyl (meth) acrylate. In addition, in this specification, (meth) acrylic acid ester shall mean both acrylic acid ester and methacrylic acid ester.

  The α, β-ethylenically unsaturated monomer mixture and the resulting acrylic emulsion resin have an acid value of 3 to 50 mgKOH / g, preferably 7 to 40 mgKOH / g. When the acid value is less than 3 mgKOH / g, the coating workability is lowered, and when it exceeds 50 mgKOH / g, the water resistance of the coating film is lowered. Further, the α, β-ethylenically unsaturated monomer mixture and the resulting acrylic emulsion resin have a hydroxyl value of 10 to 150 mgKOH / g, preferably 20 to 100 mgKOH / g. When the hydroxyl value is less than 10 mgKOH / g, sufficient curability cannot be obtained, and when the hydroxyl value exceeds 150 mgKOH / g, the water resistance of the coating film is lowered. In addition, the glass transition temperature of the polymer obtained by copolymerizing the α, β-ethylenically unsaturated monomer mixture is between -20 and 80 ° C. from the viewpoint of the mechanical properties of the resulting coating film. preferable.

  The α, β-ethylenically unsaturated monomer mixture and the resulting acrylic emulsion resin have the acid value and the hydroxyl value by including an α, β-ethylenically unsaturated monomer having an acid group or a hydroxyl group therein. be able to.

  Examples of the α, β-ethylenically unsaturated monomer having an acid group include acrylic acid, methacrylic acid, crotonic acid, 2-acryloyloxyethylphthalic acid, 2-acryloyloxyethyl succinic acid, and ω-carboxy-polycaprolactone mono (meta). ) Acrylate, isocrotonic acid, α-hydro-ω-((1-oxo-2-propenyl) oxy) poly (oxy (1-oxo-1,6-hexanediyl)), maleic acid, fumaric acid, itaconic acid, Examples thereof include 3-vinylsalicylic acid, 3-vinylacetylsalicylic acid, 2-acryloyloxyethyl acid phosphate, and 2-acrylamido-2-methylpropanesulfonic acid. Among these, acrylic acid and methacrylic acid are preferable.

  Examples of the α, β-ethylenically unsaturated monomer having a hydroxyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, allyl alcohol, (meth) acrylic alcohol, (meth ) An adduct of hydroxyethyl acrylate and ε-caprolactone can be mentioned. Among these, preferred are hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, and an adduct of hydroxyethyl (meth) acrylate and ε-caprolactone.

  Furthermore, the α, β-ethylenically unsaturated monomer mixture may further contain other α, β-ethylenically unsaturated monomers. Examples of the other α, β-ethylenically unsaturated monomers include (meth) acrylic acid esters having 3 or more carbon atoms in the ester moiety (for example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth ) T-butyl acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, phenyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid t -Butylcyclohexyl, (meth) acrylic acid dicyclopentadienyl, (meth) acrylic acid dihydrodicyclopentadienyl, etc.), polymerizable amide compounds (for example, (meth) acrylamide, N-methylol (meth) acrylamide, N -Butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acryl Luamide, N, N-dibutyl (meth) acrylamide, N, N-dioctyl (meth) acrylamide, N-monobutyl (meth) acrylamide, N-monooctyl (meth) acrylamide 2,4-dihydroxy-4′-vinylbenzophenone, N- (2-hydroxyethyl) acrylamide, N- (2-hydroxyethyl) methacrylamide, etc.), polymerizable aromatic compounds (for example, styrene, α-methylstyrene, t-butylstyrene, parachlorostyrene, vinylnaphthalene, etc.) ), Polymerizable nitrile (eg, acrylonitrile, methacrylonitrile, etc.), α-olefin (eg, ethylene, propylene, etc.), vinyl ester (eg, vinyl acetate, vinyl propionate, etc.), diene (eg, butadiene, isoprene, etc.) ) Kill. These can be selected depending on the purpose, but (meth) acrylamide is preferably used when hydrophilicity is easily imparted.

  The α, β-ethylenically unsaturated monomer other than the (meth) acrylic acid ester having 1 or 2 carbon atoms in the ester portion has a content in the α, β-ethylenically unsaturated monomer mixture. Must be set to less than 35% by weight.

  The acrylic emulsion resin contained in the aqueous metallic base coating composition of the present invention is obtained by emulsion polymerization of the α, β-ethylenically unsaturated monomer mixture. The emulsion polymerization carried out here can be carried out using a generally well-known method and is not particularly limited. Specifically, for example, an emulsifier is dissolved in water or an aqueous medium containing an organic solvent such as alcohol, ether (for example, dipropylene glycol methyl ether, propylene glycol methyl ether) as necessary, and heated. It can carry out by dripping the said (alpha), (beta) -ethylenically unsaturated monomer mixture and a polymerization initiator under stirring. An α, β-ethylenically unsaturated monomer mixture emulsified in advance using an emulsifier and water may be similarly added dropwise.

  Suitable polymerization initiators include, for example, azo oily compounds (for example, azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), and 2,2′-azobis (2 , 4-dimethylvaleronitrile)) and aqueous compounds (for example, anionic 4,4′-azobis (4-cyanovaleric acid), 2,2-azobis (N- (2-carboxyethyl) -2- Methylpropionamidine), and cationic 2,2′-azobis (2-methylpropionamidine)); and redox oily peroxides (eg, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide and t) -Butyl perbenzoate, t-butyl peroxy 2-ethylhexanoate, etc.), and aqueous peroxide Product (e.g., such as potassium persulfate and ammonium persulfate), and the like.

  As the emulsifier, those usually used by those skilled in the art can be used. However, reactive emulsifiers such as Antox MS-60 (manufactured by Nippon Emulsifier Co., Ltd.), Eleminol JS-2 (manufactured by Sanyo Chemical Industries Co., Ltd.) , Adekaria soap NE-20 (Asahi Denka Co., Ltd., α- [1-[(allyloxy) methyl] -2- (nonylphenoxy) ethyl] -ω-hydroxyoxyethylene) and Aqualon HS-10 (Daiichi Kogyo Seiyaku) A polyoxyethylene alkylpropenyl phenyl ether sulfate ester, etc., manufactured by KK is particularly preferred.

  In order to adjust the molecular weight, a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer may be used as necessary.

  The reaction temperature is determined by the initiator, and is usually 40 to 150 ° C. For example, it is preferably 60 to 90 ° C for an azo initiator and 30 to 70 ° C for a redox system. In general, the reaction time is 1 to 8 hours. The amount of initiator relative to the total amount of α, β-ethylenically unsaturated monomer mixture is generally 0.1 to 5% by weight, preferably 0.2 to 2% by weight.

  The emulsion polymerization can be performed in multiple stages, for example, in two stages. That is, first, a part of the α, β-ethylenically unsaturated monomer mixture (α, β-ethylenically unsaturated monomer mixture 1) is emulsion-polymerized, and the α, β-ethylenically unsaturated monomer mixture is added thereto. The remainder (α, β-ethylenically unsaturated monomer mixture 2) is further added to carry out emulsion polymerization.

  Here, from the viewpoint of preventing compatibility with the clear coat, the α, β-ethylenically unsaturated monomer mixture 1 preferably contains an α, β-ethylenically unsaturated monomer having an amide group. At this time, it is more preferable that the α, β-ethylenically unsaturated monomer mixture 2 does not contain an α, β-ethylenically unsaturated monomer having an amide group. Since the α, β-ethylenically unsaturated monomer mixture 1 and 2 together is the α, β-ethylenically unsaturated monomer mixture, the α, β-ethylenically unsaturated compound described above is used. The requirements for the monomer mixture will be met by the combined α, β-ethylenically unsaturated monomer mixture 1 and 2.

  The average particle size of the acrylic emulsion resin thus obtained is preferably in the range of 0.01 to 1.0 μm. If the average particle size is less than 0.01 μm, the effect of improving workability is small, and if it exceeds 1.0 μm, the appearance of the resulting coating film may be deteriorated. More preferably, it is 0.05-0.5 micrometer. This average particle size can be adjusted, for example, by adjusting the monomer composition and emulsion polymerization conditions. In addition, the said average particle diameter is displayed with the volume average particle diameter measured by the laser light scattering method.

  The acrylic emulsion resin can be used at a pH of 5 to 10 by neutralizing with a base as necessary. This is because the stability in this pH region is high. This neutralization is preferably performed by adding a tertiary amine such as dimethylethanolamine (dimethylaminoethanol) or triethylamine to the system before or after emulsion polymerization.

  Content (mass%) of acrylic emulsion resin in the aqueous | water-based metallic base coating composition of this invention is 20-60 mass% based on the mass of the resin solid content in an aqueous | water-based metallic base coating composition, Preferably it is 30-50. It is 35 mass%, More preferably, it is 35-45 mass%.

  If the content of the acrylic emulsion resin is less than 20% by mass, the coating workability may be deteriorated. If it exceeds 60% by mass, the coating performance may be deteriorated. .

Melamine resin curing agents Examples of melamine resin curing agents include butylated melamine resins, methylated melamine resins and methyl / butyl mixed alkylated melamine resins. Among these, from the viewpoint of coating film properties or water resistance when a coating film is formed, it is preferable to use a hydrophobic melamine resin, and it is preferable to use a butylated melamine resin having butyl ether as the alkyl group. Is also preferable. In addition, as a blending form of the melamine resin curing agent to the aqueous metallic base coating composition, from the viewpoint of curing stability of the melamine resin and storage stability of the coating, a hydrophobic melamine resin is used as an aqueous medium by using a specific dispersion resin. A hydrophobic melamine resin aqueous dispersion dispersed therein is preferred.

  The hydrophobic melamine resin aqueous dispersion is preferably a hydrophobic melamine resin aqueous dispersion having an average particle size of 20 to 300 nm obtained by reacting a hydrophobic melamine resin with a specific acrylic resin and dispersing it in water. In the aqueous metallic base coating composition of the present invention, when such a hydrophobic melamine resin aqueous dispersion is used, a coating film having excellent color developability can be obtained. When the average particle size is less than 20 nm, the solid content of the paint is remarkably lowered. When the average particle size is more than 300 nm, the water dispersibility is lowered, and the adhesion and surface smoothness of the formed coating film are lowered. There is a fear. The average particle size is preferably 30 to 250 nm, and more preferably 100 to 200 nm. In addition, the said average particle diameter is the value measured by the method similar to the particle diameter of acrylic emulsion resin mentioned above.

  Hydrophobic melamine resin aqueous dispersion has an acrylic resin / hydrophobic melamine resin mass ratio in the presence of an acrylic resin having an acid value of 105 to 200 mgKOH / g, a hydroxyl value of 50 to 200 mgKOH / g and a number average molecular weight of 1000 to 5000 ( Solid content) is 5/95 to 25/75, and can be prepared by reacting at a temperature of 70 to 100 ° C. for 1 to 10 hours. Specifically, the acid value is 105 to 200 mgKOH / g, A step (1) of mixing and reacting an acrylic resin having a hydroxyl value of 50 to 200 mgKOH / g and a number average molecular weight of 1000 to 5000 with a hydrophobic melamine resin, and the reaction product obtained in the above step (1) are treated with water. A hydrophobic melamine resin aqueous dispersion obtained by a production method including the step (2) of dispersing is preferred. Thereby, color development property, recoat adhesion, chipping resistance, and water adhesion resistance can be improved.

  When the acid value of the acrylic resin is less than 105 mgKOH / g, the average particle size becomes large, and the storage stability when blended in the paint may be lowered. When the acid value exceeds 200 mgKOH / g, the reaction control may be extremely difficult. The acid value is preferably 105 to 180 mgKOH / g. When the hydroxyl value of the acrylic resin is less than 50 mgKOH / g, the average particle size becomes large, and the storage stability may be reduced when the paint is used. If the hydroxyl value exceeds 200 mgKOH / g, the reaction control may be extremely difficult. The hydroxyl value is preferably 60 to 180 mgKOH / g. If the number average molecular weight of the acrylic resin is less than 1000, the particle size becomes large and the storage stability may be reduced when the paint is used. If the number average molecular weight exceeds 5000, the reaction control may be extremely difficult. The number average molecular weight is preferably 1500 to 4000. The number average molecular weight of the acrylic resin is a value measured with a polystyrene standard by the GPC method.

  The acrylic resin is, for example, a monomer composition containing a carboxylic acid group-containing unsaturated monomer, a hydroxyl group-containing unsaturated monomer, and, if necessary, other ethylenically unsaturated monomers in a water-soluble organic solvent. It can be obtained by using a known polymerization method such as emulsion polymerization in the presence of a polymerization disclosure agent (for example, t-butylperoxy 2-ethylhexanoate) and an emulsifier (for example, methylpropylene diglycol).

  The carboxylic acid group-containing unsaturated monomer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, crotonic acid, 2-acryloyloxyethylphthalic acid, 2-acryloyloxyethyl succinic acid, and 2-acryloyloxyethyl acid phosphate. , 2-acrylamido-2-methylpropanesulfonic acid, ω-carboxy-polycaprolactone mono (meth) acrylate, isocrotonic acid, α-hydro-ω-[(1-oxo-2-propenyl) oxy] poly [oxy (1 -Oxo-1,6-hexanediyl)], maleic acid, fumaric acid, itaconic acid, 3-vinylsalicylic acid, 3-vinylacetylsalicylic acid and the like.

  Examples of the hydroxyl group-containing unsaturated monomer include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, allyl alcohol, (meth) acrylic alcohol, hydroxy (meth) acrylate. Ε-caprolactone adduct of ethyl can be mentioned. Among these, preferred are hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, and ε-caprolactone adduct of hydroxyethyl (meth) acrylate.

  Examples of the other ethylenically unsaturated monomers include, for example, (meth) acrylic acid ester having 1 or 2 carbon atoms in the ester portion [methyl (meth) acrylate or ethyl (meth) acrylate]; carbon number in the ester portion. 3 or more (meth) acrylic acid esters [for example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic Lauryl acid, phenyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentadienyl (meth) acrylate, (meth) acrylic acid Dihydrodicyclopentadienyl etc.], polymerizable amide compounds [eg (meth) acrylic Amide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N, N-dioctyl (meth) acrylamide, N -Monobutyl (meth) acrylamide, N-monooctyl (meth) acrylamide, 2,4-dihydroxy-4'-vinylbenzophenone, N- (2-hydroxyethyl) acrylamide, N- (2-hydroxyethyl) methacrylamide, etc.] Polymerizable aromatic compounds (eg, styrene, α-methylstyrene, t-butylstyrene, parachlorostyrene, vinylnaphthalene, etc.); polymerizable nitriles (eg, acrylonitrile, methacrylonitrile, etc.); α-olefins (eg, Ethylene, propylene ]; Vinyl esters [for example, vinyl acetate, vinyl propionate]; diene (e.g., butadiene, isoprene), and the like.

  Conventionally known hydrophobic melamine resins can be used, but the solubility parameter δ (Sp) is in the range of 9.0 ≦ Sp ≦ 11.5, preferably 9.5 ≦ Sp ≦ 11.0. It is preferable that. If the Sp is less than 9.0, the average particle size may exceed 300 nm. If it exceeds 11.5, the average particle size exceeds 300 nm. May decrease.

  The solubility parameter δ (Sp) is a scale indicating the degree of hydrophilicity or hydrophobicity of the resin, and is also an important scale for judging the compatibility between the resins. In general, the solubility parameter δ (Sp) of the resin is such that the resin is dissolved in a good solvent having a known Sp of the solubility parameter δ, and the turbidity is low in a poor solvent having a low Sp and a good solvent having a high Sp. It is known that the Sp value of the resin can be determined by titration (Reference 1: CM Hansen J. Paint. Tech., 39 [505], 104 (1967), and Reference 2: Toshikatsu Kobayashi Coloring Material, 77 [4], 188-192 (2004)).

  For example, the solubility parameter δ (Sp) can be determined by turbidity titration (measurement temperature: 20 ° C.) described in detail below using the sample, the good solvent, and the poor solvent described below.

Sample: A measurement resin sample obtained by weighing 0.5 g of resin in a 100 ml beaker, adding 10 ml of a good solvent using a whole pipette, and dissolving with a magnetic stirrer.
Good solvent: acetone (Sp: δg = 9.77 as measured by Hansen (Reference 1))
Poor solvent: Hexane (Sp: δpl = 7.24 measured by Hansen (Reference 1)) and deionized water (Sp: δph = 23.50 measured by Hansen (Reference 1))

Using a turbidity titration 50 ml burette, hexane as a poor solvent is dropped onto the sample, the amount of hexane dropped at the point of turbidity is recorded, and the volume fraction φpl of the hexane used is determined from the following equation.
φpl = (Drop amount of hexane at the point where turbidity occurs) /
((Drop amount of hexane at the point where turbidity occurs) + (Volume of good solvent))
Next, deionized water, which is a poor solvent, was dropped onto the sample using a 50 ml burette, the amount of deionized water dropped at the point where turbidity was recorded, and the volume fraction φph used was Calculate from the formula.
φph = (Drip amount of deionized water at the point where turbidity occurs) /
((Drip amount of deionized water at the point where turbidity occurs) + (Volume of good solvent))

  The Sp value δml of the resin (mixed state) at the turbid point generated by dropping hexane and the Sp value δmh of the resin (mixed state) at the turbid point generated by dropping deionized water are respectively represented by the following formula (1): And the average value of δml and δmh is the Sp value (δpoly) of the resin, and can be determined from the following equation (3).

  δml = φplδpl + (1−φpl) δg Formula (1)

  δmh = φphδph + (1−φph) δg Formula (2)

  δpoly = (δml + δmh) / 2 Formula (3)

  The step (1) includes a step of mixing in the presence of the acrylic resin so that a mass ratio (solid content) of the acrylic resin / the hydrophobic melamine resin is 5/95 to 25/75. preferable. By performing the step (1), a reaction product of the acrylic resin and the hydrophobic melamine resin can be obtained. When the mixing ratio is less than 5/95, the average particle size may exceed 300 nm. When the mixing ratio is greater than 25/75, the NV (solid content concentration) of the paint may be significantly reduced or the reaction control may be extremely difficult. More preferably, it is 10 / 90-20 / 80.

  In addition, although the mixing method of an acrylic resin and hydrophobic melamine resin can be performed by a conventionally well-known method, for example, the acrylic resin is an organic solvent (for example, the hydrophobic melamine resin and the acrylic resin in advance). Mixing in the state of a solvent-type acrylic resin using dipropylene glycol methyl ether or the like) as a solvent, and stirring the mixture until it becomes uniform can be included. Then, you may disperse | distribute in water using basic substances, surfactant, etc., such as amine (for example, dimethylethanolamine etc.). In this case, since the acrylic resin functions as a protective resin for the hydrophobic melamine resin, the dispersed melamine resin particles have good stability and are preferable.

  In the present invention, in the above step (1), since the blending amount of the acrylic resin with respect to the hydrophobic melamine resin is small, when the obtained hydrophobic melamine resin aqueous dispersion is used as a curing agent, the function as a curing agent is achieved. Less likely to decline. And although there are few compounding quantities of an acrylic resin, the average particle diameter after water dispersion is 20-300 nm. For this reason, the hydrophobic melamine resin aqueous dispersion obtained by this invention can be used suitably as a hardening | curing agent of an aqueous | water-based metallic base coating composition. In the step (1), in addition to the acrylic resin and the hydrophobic melamine resin, other resins such as a polyester resin may be included within the range not excluding the effect of the present invention.

  In the step (1), the reaction condition between the acrylic resin and the hydrophobic melamine resin is that the reaction temperature is 70 to 100 ° C, preferably 75 to 90 ° C. Moreover, it is preferable that reaction time is 1 to 10 hours, and it is more preferable that it is 1 to 5 hours. If the reaction temperature and reaction time are both lower than the lower limit, the average particle size may exceed 300 nm. If the upper limit is exceeded, reaction control may become extremely difficult.

  By performing the heating and mixing step (hot blending step), a reaction product obtained by partially or partially crosslinking the acrylic resin and the hydrophobic melamine resin can be obtained. By cross-linking to some extent, the average particle size of the obtained melamine resin dispersion hardly changes, and the storage stability after forming a paint is excellent.

  For mixing / dispersing the hydrophobic melamine resin, a disper, a homomixer, a mill, or the like can be used. If necessary, a basic substance such as the amine or a surfactant can be used in combination. . The dispersion time can be shortened and the resulting dispersion can be stabilized.

  In the said process (2), the reaction product obtained by performing the said process (1) is water-dispersed, and the process of obtaining the hydrophobic melamine resin water dispersion with an average particle diameter of 20-300 nm is performed. is there. By performing the step (2), an aqueous dispersion (aqueous dispersion) in which resin particles having an average particle diameter of 20 to 300 nm are dispersed in water can be obtained.

  In the step (2), the method for water-dispersing the reaction product obtained in the step (1) is not particularly limited, and an ordinary resin water-dispersing method can be used. After cooling to a temperature of 50 ° C. or lower, it is preferable to disperse in water by diluting with water. Thereby, the hydrophobic melamine resin aqueous dispersion with an average particle diameter of 20 to 300 nm can be suitably obtained. If it is not cooled to 50 ° C. or lower, it may not be possible to obtain one having an average particle size of 20 to 300 nm. It is more preferable to disperse in water by cooling to 30 to 40 ° C. and then diluting with water.

  In the said process (2), it can be used by pH = 5-10 by using together basic substances, such as amine (for example, dimethylethanolamine etc.) as needed. This is because the hydrophobic melamine resin aqueous dispersion in this pH region has high stability. This neutralization is preferably performed by adding a tertiary amine such as dimethylethanolamine or triethylamine to the system before or after the reaction between the acrylic resin and the hydrophobic melamine resin. In particular, after the reaction between the acrylic resin and the hydrophobic melamine resin, a tertiary amine is added, and then the reaction product is cooled to a temperature of 50 ° C. or lower and then diluted with water to disperse the water. It is particularly preferable to do this. Thereby, the hydrophobic melamine resin aqueous dispersion with an average particle diameter of 20 to 300 nm can be suitably obtained.

  In addition to the above curing agents, other curing agents generally used for paints can be used. Examples of such compounds include blocked isocyanate resins, epoxy compounds, aziridine compounds, carbodiimide compounds, oxazoline compounds, and metal ions.

  The blending amount of the other curing agent is preferably 0 to 40% by weight, and more preferably 1 to 35% by weight, based on the resin solid content in the aqueous metallic base coating composition. When it exceeds 40% by weight, a hard and brittle coating film is formed.

  The amount of the aqueous dispersion of the hydrophobic melamine resin dispersed in the aqueous metallic base coating composition is determined by the mass mixing ratio of all the resin components in the coating and the hydrophobic melamine resin in the dispersion (hydrophobic melamine resin / total resin). Component) is preferably 10/90 to 50/50, and more preferably 25/75 to 45/55. When it is less than 10/90, the curability of the coating film is lowered, and when it exceeds 50/50, the coating film is hard and brittle.

  The aqueous metallic base coating composition may contain other film-forming resin as necessary. Other film-forming resins are not particularly limited, and film-forming resins such as water-soluble acrylic resins, polyester resins, alkyd resins, epoxy resins, and urethane resins can be used.

  The other film-forming resin has a number average molecular weight of 3,000 to 50,000, preferably 6,000 to 30,000. If it is less than 3000, workability and curability are not sufficient, and if it exceeds 50000, the non-volatile content at the time of coating becomes too low, and workability is rather deteriorated.

  The other coating film-forming resins preferably have an acid value of 10 to 100 mgKOH / g, more preferably 20 to 80 mgKOH / g. When the acid value exceeds 100 mgKOH / g, the water resistance of the coating film decreases and 10 mgKOH / g Below g, the water dispersibility of the resin decreases. In addition, the other film-forming resin preferably has a hydroxyl value of 20 to 180 mgKOH / g, more preferably 30 to 160 mgKOH / g, and if the hydroxyl value exceeds 180 mgKOH / g, the water resistance of the coating film decreases. When it is less than 20 mgKOH / g, the curability of the coating film is lowered.

Examples of pigment pigments include glitter pigments and colored pigments. The shape of the glitter pigment is not particularly limited, and may be colored. For example, the pigment having an average particle diameter (D ₅₀ ) of 2 to ₅₀ μm and a thickness of 0.1 to 5 μm Is preferred. Those having an average particle diameter in the range of 10 to 35 μm are excellent in glitter and are more preferably used. Specific examples include non-colored or colored metallic brightening agents such as aluminum, copper, zinc, iron, nickel, tin, and aluminum oxide, and alloys, and mixtures thereof. In addition, interference mica pigments, white mica pigments, graphite pigments, and the like are included in this. The average particle diameter of the glitter pigment can be measured by a laser light diffraction method.

  On the other hand, examples of the colored pigment include organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, perinone pigments, Examples include perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments, and inorganic pigments such as yellow lead, yellow iron oxide, bengara, carbon black, titanium dioxide, etc. Examples thereof include calcium carbonate, barium sulfate, clay, and talc.

  The total pigment concentration (PWC) in the aqueous metallic base coating composition is preferably 0.1 to 50%. More preferably, it is 0.5 to 40%, and particularly preferably 1.0 to 30%. If it exceeds 50%, the appearance of the coating film deteriorates. When a bright pigment is included, the pigment concentration (PWC) is generally preferably 18.0% or less. In this case, when the PWC exceeds 18.0%, the appearance of the coating film is deteriorated. More preferably, it is 0.01 to 15.0%, and particularly preferably 0.01 to 13.0%.

  The aqueous metallic base coating composition of the present invention further has a solubility in water of 0.01 to 5.0% by mass and an alcoholic organic solvent having a boiling point of 160 to 200 ° C. and / or a solubility in water of 0.00. A glycol ether organic solvent having a boiling point of 205 to 240 ° C. may be contained. In addition, the said solubility shows the mass of the organic solvent melt | dissolved in 100 mass parts of water in 20 degreeC in percentage.

  If the solubility of the alcohol-based organic solvent in water is less than 0.01% by mass, the viscosity of the paint may increase significantly. If the solubility exceeds 5.0% by mass, the viscosity of the paint will decrease significantly. There is a risk of problems such as a decrease in painting workability. The solubility of the alcohol-based organic solvent in water is preferably 0.05 to 3.0% by mass.

  If the boiling point of the alcohol-based organic solvent is less than 160 ° C, there is a risk of problems such as poor coating workability, especially cracking properties. If the boiling point exceeds 200 ° C, the coating workability, especially sagging properties, may occur. There is a risk of problems such as lowering. The boiling point of the alcoholic organic solvent is preferably 170 to 190 ° C.

  The alcohol-based organic solvent (solubility, boiling point) is heptanol (0.5% by mass, 168 ° C.), 2-ethylhexyl alcohol (0.1% by mass, 184 ° C.) and cyclohexanol (4.0% by mass, 161 ° C.). 2-ethylhexyl alcohol is preferable from the viewpoint of the stability (particle size) of the acrylic emulsion resin or the hydrophobic melamine resin aqueous dispersion.

  The content of the alcohol-based organic solvent in the aqueous metallic base coating composition is 5 to 45% by mass based on the mass of resin solids in the aqueous metallic base coating composition, and the content is less than 5% by mass. If the content exceeds 45% by mass, the coating workability such as the cracking property may be deteriorated.

  When the alcohol-based organic solvent is added to the aqueous metallic base coating composition, atomization at the time of coating is improved, so that it is possible to significantly prevent skinning and aggregation.

  Furthermore, you may add the glycol ether organic solvent whose solubility with respect to water is 0.01-5.0 mass% and whose boiling point is 205-240 degreeC to the water-based metallic base coating composition of this invention.

  If the solubility of the glycol ether organic solvent in water is less than 0.01% by mass, the viscosity of the paint may increase significantly. If the solubility exceeds 5.0% by mass, the viscosity of the paint will decrease significantly. However, there is a risk of problems such as a decrease in painting workability. The solubility of the glycol ether organic solvent in water is preferably 0.05 to 3.0% by mass.

  If the boiling point of the glycol ether organic solvent is less than 205 ° C, there is a risk of problems such as deterioration in coating workability, particularly cracking properties. If the boiling point exceeds 240 ° C, painting workability, There is a risk of problems such as loss of performance. The boiling point of the glycol ether organic solvent is preferably 210 to 230 ° C.

  The glycol ether organic solvent (solubility, boiling point) is ethylene glycol monohexyl ether (hexyl glycol, 1.0% by mass, 208 ° C.), ethylene glycol mono 2-ethylhexyl ether (2-ethylhexyl glycol, 0.2% by mass). 225 ° C.) and dipropylene glycol monobutyl ether (5.0% by mass, 215 ° C.), and from the viewpoint of the stability (particle size) of the acrylic emulsion resin or hydrophobic melamine resin aqueous dispersion, ethylene Glycol mono 2-ethylhexyl ether is preferred.

  The content of the glycol ether organic solvent in the aqueous metallic base coating composition is 5 to 45% by mass based on the mass of the resin solids in the aqueous metallic base coating composition, and the content is less than 5% by mass. If there is, the skinning and cohesiveness cannot be improved, and if the content exceeds 45% by mass, there is a risk of problems such as deterioration of coating workability such as cracking properties.

  When the glycol ether organic solvent is added to the aqueous metallic base coating composition in addition to the alcohol organic solvent, the stability (particle size) of the acrylic emulsion resin or hydrophobic melamine resin aqueous dispersion is excellent.

  When the aqueous metallic base coating composition of the present invention contains an alcohol organic solvent and a glycol ether organic solvent, the mass ratio of alcohol organic solvent / glycol ether organic solvent is 1/1 to 3/1, and the mass ratio If the ratio is less than 1/1, the viscosity of the paint may be reduced, causing problems such as poor coating workability. If the mass ratio exceeds 3/1, the acrylic emulsion resin or hydrophobicity over time There is a risk that the stability of the melamine resin aqueous dispersion may decrease.

  In the aqueous metallic base coating composition of the present invention, it is preferable to use a combination of an alcohol-based organic solvent and a glycol ether-based organic solvent.

  In the aqueous metallic base coating composition of the present invention, in addition to the above-mentioned components, additives usually added to the coating, for example, surface conditioners, dispersants, viscosity modifiers, thickeners, antioxidants, UV inhibitors Further, an antifoaming agent, a pH adjusting agent and the like may be blended.

  The method for producing the aqueous metallic base coating composition is not particularly limited as long as the above components can be uniformly dispersed, and examples include methods known to those skilled in the art, such as a kneader or roll mill.

  As described above, the aqueous metallic base coating composition of the present invention comprises a surfactant containing a reaction product of a non-reducing disaccharide or trisaccharide (a1) and a C2-C4 alkylene oxide (a2). By containing, it is possible to suppress and / or prevent skinning and aggregation of the metallic coating composition. Furthermore, the water-based metallic base coating composition further has a solubility in water of 0.01 to 5.0% by mass, a boiling point of 160 to 200 ° C. and / or a solubility in water of 0.01. By including a glycol ether organic solvent having a boiling point of 205 to 240 ° C., it is possible to prevent skinning and flaking.

Clear coating composition The clear coating composition can be applied onto a metallic base coating film to form a clear coating film, and the unevenness and flickering of the metallic base coating film can be smoothed. Can be protected and the appearance can be improved.

  The clear coating composition is not particularly limited, and examples thereof include a coating composition containing a film-forming resin and, if necessary, a curing agent and other additives.

  It does not specifically limit as a film-forming resin, For example, an acrylic resin, a polyester resin, an epoxy resin, a urethane resin etc. are mentioned.

  From the viewpoint of transparency or acid etching resistance, a combination of an acrylic resin and / or a polyester resin as the coating film-forming resin and an amino resin and / or a polyisocyanate resin as a curing agent, or a carboxylic acid / epoxy curing system It is preferable to use an acrylic resin and / or a polyester resin.

  It is preferable to contain a viscosity control agent as an additive in order to prevent familiarity, inversion, sagging, etc. between the coating layers. The addition amount of the viscosity control agent is 0.01 to 10 parts by mass, preferably 0.02 to 8 parts by mass, with respect to 100 parts by mass of the resin solid content of the clear coating composition. Preferably, it is 0.03 mass part-6 mass parts. When the addition amount exceeds 10 parts by mass, the appearance of the obtained coating film is deteriorated, and when it is less than 0.01 part by mass, the viscosity control effect cannot be obtained, causing a problem such as sagging when forming the coating film It becomes.

  The clear coating composition may be any of organic solvent type, aqueous type (water-soluble, water-dispersible, emulsion), non-water-dispersed type, and powder type, and if necessary, a curing catalyst, surface conditioning. An additive such as an agent can be used.

  Examples of the water-based clear coating composition include those containing a resin obtained by neutralizing a film-forming resin contained in the above-mentioned examples of the clear coating composition with a base to make it water-based. Can be mentioned. This neutralization can be carried out by adding tertiary amines such as dimethylethanolamine and triethylamine before or after polymerization.

  The method for preparing the clear coating composition is not particularly limited, and the clear coating composition can be prepared according to a method known to those skilled in the art. A commercially available clear coating composition may also be used.

Method of forming a multilayered film multilayer coating film forming method The present invention includes the following steps:
An intermediate coating composition is applied to an object that may have an undercoat film such as an electrodeposition film (for example, a steel sheet that may be subjected to chemical conversion treatment such as phosphate treatment). The process of forming an intermediate coating film (may be applied multiple times in multiple stages),
The process of applying a water-based metallic base coating composition to an intermediate coating film to form a metallic base coating film (may be applied multiple times in multiple stages),
A step of applying a clear coating composition to a metallic base coating to form a clear coating (may be applied multiple times in multiple stages).

  Moreover, the multilayer coating film used in the present invention may further appropriately include a plurality of coating films such as a primer in the lower layer and an overcoat clear in the upper layer.

  The coating composition is generally applied by electrostatic coating by air spray. For example, an air atomizing type coating machine (auto REA), a rotary centrifugal atomizing type coating machine (bell, microbell, micromicrobell, cartridge). Bell) or other coating means can be used.

  Further, at the time of painting, each paint composition may utilize the paint circulation system shown in FIG. Specifically, the coating composition (1) is poured into the circulation tank (2), and mechanically stirred by the stirring means (3) (for example, an impeller), the coating composition (1) is circulated by a circulation pump ( 4) A filter (8) (for example, CP FILTER 150 manufactured by Chisso Filter Co., Ltd.) and a pipe (5) are conveyed to a coating means (6) by a (for example, a circulation pump manufactured by Graco). After coating, the surplus coating composition or the unused coating composition is obtained from pipe (7) and filtration device (9) (for example, filter back R-150-NMO-01-ER manufactured by Kajika Corporation). Return to the circulation tank (2) again. The tubes (5) and (7) are preferably made of stainless steel from the viewpoint of rust prevention. It is also possible to add a coating composition during painting, and the liquid level of the coating composition (1) in the circulation tank (2) can go up and down between S1 and S3.

  The formation method of the multilayer coating film of this invention may include the preheating process after each process as needed. In addition, preheating means heating-drying to such an extent that the formed coating film is not hardened, and the formed coating film is normally heated at 40-80 degreeC for 5 to 10 minutes.

  Moreover, after each process, you may harden a coating film by the baking drying process (for example, for 10 to 40 minutes at 120-160 degreeC), respectively.

  The film thickness after curing is, for example, preferably 15 to 25 μm for the undercoat electrodeposition coating film, 10 to 50 μm for the intermediate coating film, preferably 10 to 35 μm for the metallic base coating film, and preferably 20 to 80 μm for the clear coating film. .

  The aqueous metallic base coating composition of the present invention used in the method for forming a multilayer coating film is a reaction product of a non-reducing disaccharide or trisaccharide (a1) and an alkylene oxide (a2) having 2 to 4 carbon atoms. Since the surfactant and the specific alcohol-based organic solvent and / or glycol ether-based organic solvent are contained, it is possible to significantly suppress and / or prevent skinning and aggregation of the coating composition.

  Hereinafter, the present invention will be described in detail with specific examples, but the present invention is not limited to the following examples. In the examples, “parts” means “parts by mass” unless otherwise specified.

Production Example 1: Production of acrylic emulsion resin A 126.5 parts of deionized water was added to a reaction vessel, and the temperature was raised to 80 ° C. while stirring in a nitrogen stream. Next, as the first stage α, β-ethylenically unsaturated monomer mixture, methyl methacrylate 24.42 parts, ethyl acrylate 25.78 parts, styrene 10.00 parts, acrylamide 4.00 parts, acrylic acid 2 -Hydroxyethyl 5.80 parts, Aqualon HS-10 (polyoxyethylene alkylpropenyl phenyl ether sulfate ester, Daiichi Kogyo Seiyaku Co., Ltd.) 0.5 parts, Adekaria soap NE-20 (α- [1-[(allyloxy) ) Methyl] -2- (nonylphenoxy) ethyl] -ω-hydroxyoxyethylene, manufactured by Asahi Denka Co., Ltd., 80% aqueous solution), a monomer emulsion comprising 0.5 part and deionized water 80 parts, and ammonium persulfate 0.24. And an initiator solution consisting of 10 parts of deionized water were added dropwise to the reaction vessel in parallel over 2 hours. After completion of the dropping, aging was performed at the same temperature for 1 hour.

  Furthermore, as the α, β-ethylenically unsaturated monomer mixture at the second stage at 80 ° C., 24.45 parts of ethyl acrylate, 2.48 parts of 2-hydroxyethyl acrylate, 3.07 parts of methacrylic acid, Aqualon HS A monomer emulsion consisting of 0.2 parts of -10 and 10 parts of deionized water and an initiator solution consisting of 0.06 parts of ammonium persulfate and 10 parts of deionized water were placed in a reaction vessel in parallel over 0.5 hour. It was dripped. After completion of the dropping, aging was performed at the same temperature for 2 hours.

  Next, after cooling to 40 ° C. and filtration through a 400 mesh filter, 0.32 part of dimethylaminoethanol was added to adjust the pH to 6.5, the average particle size was 150 nm, the non-volatile content was 30%, the solid content acid value was 20 mg KOH / g. An acrylic emulsion resin A having a hydroxyl value of 40 mgKOH / g was obtained.

Production Example 2: Production of water-soluble acrylic resin B (film-forming resin) 23.89 parts of dipropylene glycol methyl ether and 16.11 parts of propylene glycol methyl ether are added to a reaction vessel, and mixed and stirred in a nitrogen stream. The temperature was raised to 105 ° C. Next, 13.1 parts of methyl methacrylate, 68.4 parts of ethyl acrylate, 11.6 parts of 2-hydroxyethyl methacrylate and 6.9 parts of methacrylic acid, 10.0 parts of dipropylene glycol methyl ether and t-butyl An initiator solution consisting of 1 part of peroxy 2-ethylhexanoate was dropped into the reaction vessel in parallel over 3 hours. After completion of the dropping, aging was performed at the same temperature for 0.5 hours.

  Further, an initiator solution consisting of 5.0 parts of dipropylene glycol methyl ether and 0.3 part of t-butylperoxy 2-ethylhexanoate was added dropwise to the reaction vessel over 0.5 hours. After completion of the dropping, aging was performed at the same temperature for 2 hours.

  After removing 11.11 parts of the solvent at 110 ° C. under reduced pressure (70 Torr) using a solvent removal apparatus, 204 parts of deionized water and 7.14 parts of dimethylaminoethanol were added to obtain a water-soluble acrylic resin B. The obtained water-soluble acrylic resin B had a nonvolatile content of 30.0%, a solid content acid value of 40 mgKOH / g, and a hydroxyl value of 50 mgKOH / g.

Production Example 3: Production of acrylic resin for melamine dispersion 50 parts of MFDG (methylpropylene diglycol, manufactured by Nippon Emulsifier Co., Ltd.) was added to a reaction vessel, and the temperature was raised to 130 ° C. while stirring in a nitrogen stream. Next, 16.9 parts of methacrylic acid, 5.4 parts of methyl acrylate, 14.5 parts of 2-hydroxyethyl acrylate and 54.7 parts of ethyl acrylate, 10.0 parts of dipropylene glycol methyl ether and t-butyl An initiator solution consisting of 13 parts of peroxy 2-ethylhexanoate was dropped into the reaction vessel in parallel over 3 hours. After completion of the dropping, aging was performed at the same temperature for 0.5 hours.

  Further, an initiator solution consisting of 0.5 part of t-butylperoxy 2-ethylhexanoate and 5 parts of dipropylene glycol methyl ether was added dropwise over 0.5 hours. After completion of the dropwise addition, aging was performed at the same temperature for 1 hour. Subsequently, it was cooled to 50 ° C. to obtain an acrylic resin having a nonvolatile content of 60%, a solid content acid value of 110 mgKOH / g, a hydroxyl value of 70 mgKOH / g, and a number average molecular weight of 3000.

Production Example 4: Production of Hydrophobic Melamine Resin Aqueous Dispersion 8.1 parts of acrylic resin of Production Example 3 (5 parts solids) and Yuban 20SB (fully butylated melamine resin, 60% solids by Nippon Cytec Co., Ltd., Sp value) 9.7) 50 parts (solid content 30 parts) were mixed and stirred at 80 ° C. for 4 hours. Thereafter, 0.8 part of dimethylethanolamine was added and sufficiently stirred until uniform, cooled to 40 ° C., and then 41 parts of ion-exchanged water was added dropwise over 1 hour, whereby the hydrophobicity having an average particle diameter of 150 nm. A melamine resin aqueous dispersion (solid content 35%) was obtained.

  The Sp value of the melamine resin “Uban 20SB” was measured by turbidity titration using the following good and poor solvents (measurement temperature: 20 ° C.).

Good solvent: Acetone (Sp: δg = 9.77)
Antisolvent: hexane (Sp: δpl = 7.24) and
Deionized water (Sp: δph = 23.50)

Sample preparation 0.5 g of melamine resin “Uban 20SB” was weighed into a 100 ml beaker, 10 ml of a good solvent (acetone) was added using a whole pipette, and dissolved with a magnetic stirrer to prepare a measurement resin sample.

Hexane was dropped onto the measurement resin sample using a turbidity titration 50 ml burette, and the amount of hexane dropped at the point where turbidity occurred was recorded (58.21 ml). The volume fraction φpl of hexane used was 0.8534.
φpl = (58.21) / (58.21 + 10) ≈0.8534

Subsequently, deionized water was dropped onto the measurement resin sample in the same manner as in the case of hexane using a 50 ml burette, and the dropping amount of deionized water at the point where turbidity occurred was recorded (1.74 ml). The volume fraction φph of deionized water used was 0.1482.
φph = (1.74) / (1.74 + 10) ≈0.1482

  The Sp value (δpoly) of the melamine resin “Yuban 20SB” obtained from the above formulas (1), (2) and (3) was 9.7.

δml = φpl × δpl + (1−φpl) × δg = (0.8534) (7.24) + (1-0.8534) (9.77) ≈7.6109
δmh = φph × δph + (1−φph) × δg = (0.1482) (23.50) + (1-0.1482) (9.77) ≈11.08048
δpoly = (δml + δmh) / 2 = (7.6109 + 11.8048) /2≈9.7

Production Example 5: Production of phosphoric acid group-containing acrylic resin (dispersant) 40 parts of ethoxypropanol was charged in a 1 liter reaction vessel equipped with a stirrer, temperature controller, and cooling tube, and 4 parts of styrene and n-butyl acrylate were added to this. 35.96 parts, 18.45 parts of ethylhexyl methacrylate, 13.92 parts of 2-hydroxyethyl methacrylate, 7.67 parts of methacrylic acid, 20 parts of ethoxypropanol, phosmer PP (acid phosphooxyhexa (oxypropylene produced by Unichemical) ) Monomethacrylate) 40 parts of a solution in which 20 parts were dissolved and 121.7 parts of a monomer solution consisting of 1.7 parts of azobisisobutyronitrile were added dropwise at 120 ° C. for 3 hours, and stirring was further continued for 1 hour. The obtained resin was an acrylic acid varnish having an acid value of 105 mgKOH / g, of which an acid value of 55 mgKOH / g based on a phosphoric acid group, a hydroxyl value of 60 mgKOH / g and a number average molecular weight of 6000, and a nonvolatile content of 63%.

Example 1: Production of aqueous metallic base coating composition 133.3 parts of acrylic emulsion resin A of Production Example 1 and 50.0 parts of water-soluble acrylic resin B of Production Example 2, sucrose polyether interface manufactured by San Nopco 8.0 parts of the activator “SN Clean Act 82”, 101.1 parts of the aqueous dispersion of the hydrophobic melamine resin of Production Example 4, Alpaste MH-8801 (Aluminum luster pigment manufactured by Asahi Kasei Kogyo Co., Ltd., active ingredient 75) %) 16.7 parts, Degussa Carbon FW-200P (Degussa Japan Co., Ltd. carbon black pigment) 0.5 parts, Production Example 5 phosphoric acid group-containing acrylic resin 5.4 parts, Mitsubishi Chemical Corporation 2 -Ethylhexyl alcohol (2EHOH) 20 parts (20% by mass based on resin solids), ethylene glycol mono 2-ethylhexyl ether (E HG) 20 parts (20% by mass with respect to the resin solid content), Sannopco viscosity modifier “SN thickener N-1 (solid content 25%)” 1.0 part, Nihon Paint Co., Ltd. cross-linked resin particles ( An aqueous metallic base coating composition was obtained by adding 25 parts of a viscosity modifier (solid content 30%) and 2 parts of a 10% by mass aqueous dimethylethanolamine (DMEA) solution and uniformly dispersing the mixture.

Example 2: Preparation of aqueous metallic base coating composition According to Example 1, an aqueous metallic base coating composition was prepared using 40 parts of 2EHOH alone instead of 20 parts of 2EHOH and 20 parts of EHG in Example 1 ( Table 1).

Example 3: Preparation of aqueous metallic base paint composition An aqueous metallic base paint composition was prepared according to Example 1 using 3.0 parts SN Cleanact 82 (surfactant) (Table 1).

Comparative Examples 1-3: Production of Comparative Aqueous Metallic Base Coating Composition According to Example 1, except that 40 parts of 2EHOH (Comparative Example 1), 40 as an organic solvent in the absence of surfactant (SN Cleanact 82) Comparative aqueous metallic base coating compositions were prepared using parts of EHG (Comparative Example 2), 20 parts of 2EHOH and 20 parts of EHG (Comparative Example 3), respectively (Table 2).

Formation of multi-layer coating film Cathodic electrodeposition paint "Power Top U-50" (manufactured by Nippon Paint Co., Ltd.) on a dull steel plate with a thickness of 0.8mm, length 30cm, width 40cm treated with zinc phosphate, dry film thickness 20μm Electrodeposition coating was carried out so as to be and heated at 160 ° C. for 30 minutes. Furthermore, a gray intermediate coating paint “Olga P-30” (polyester / melamine paint manufactured by Nippon Paint Co., Ltd.) diluted in advance for 25 seconds (using a No. 4 Ford cup, measured at 20 ° C.) on the coated plate. Two-stage coating was performed with air spray so that the dry film thickness was 35 μm, and the film was heated at 140 ° C. for 30 minutes.

  After cooling, the aqueous metallic base coating composition of the example was diluted with deionized water for 30 seconds (measured at 20 ° C. using a No. 4 Ford cup) at room temperature of 25 ° C. and humidity. Under the condition of 85%, two-stage coating was performed with “μμ Bell COPES-IV type” (manufactured by ABB Industry) for water-based paint coating so that the dry film thickness was 20 μm. An interval of 1 minute was taken between the two applications. After the second application, setting was performed for 5 minutes. Thereafter, preheating was performed at 80 ° C. for 5 minutes.

  After preheating, the coated plate is allowed to cool to room temperature, and then “Mac Flow O-1820 Clear” (acid / epoxy curable clear coating manufactured by Nippon Paint Co., Ltd.) is applied as a clear coating to a dry film thickness of 40 μm. And set for 7 minutes. Next, the coated plate was heated at 140 ° C. for 30 minutes with a dryer to obtain a coated plate having a multilayer coating film composed of an electrodeposition coating film, an intermediate coating film, a metallic base coating film, and a clear coating film.

Skinning The skininess of the aqueous metallic base coating compositions of Examples and Comparative Examples was evaluated by the following methods and criteria. The results are shown in Tables 1 and 2 below.

Test method 1. The coating composition (150 cc) of Example or Comparative Example was added with 200 ml of P.I. Sampling in a P cup (manufactured by MYSEC) and immediately applying the coating composition to P.C. Drain from P cup.
2. The P.P. The P cup is left in a constant temperature room at 20 ° C. for 18 hours. Or, P.P. The P cup is left in a constant temperature room at 40 ° C. for 30 minutes.
3. P. Put the coating composition (150 cc) in the P cup again.
4). P. Stir the P cup at 1500 rpm for 3 minutes.
5). After the coating composition was filtered through a nylon 200 mesh filter (manufactured by Taiyo Wire Mesh Co., Ltd.), Rinse the P-cup with water and filter the wash water through a mesh filter to check for residue.

Evaluation criteria ○: No filtration residue is present ○ △: Filtration residue is almost absent △: A small amount of filtration residue adheres thinly △: Clearly filtration residue is present ×: Filtration residue remains as a lump

Agglomerated glossiness The agglomeration glossiness of the aqueous metallic base coating compositions of Examples and Comparative Examples was evaluated by the following methods and criteria. The results are shown in Tables 1 and 2 below.
Test method 1. 200 ml of P.I. A coating composition (100 cc) is added to a P cup (manufactured by MYSEC), and the mixture is stirred on a stirrer at room temperature (about 20 ° C.) for 3 days.
2. After the coating composition is filtered through a 200 mesh filter, The P cup is rinsed with water and the wash water is also filtered through a mesh filter.
3. P. The adhesion state of the coating composition in the P cup and the stirrer and the residue are visually observed.

Evaluation criteria ○: No adhesion to filtration residue and stirrer ○ △: Almost no adhesion to filtration residue and stirrer △: A small amount of filtration residue is attached to the stirrer △ ×: Clearly There is a filtration residue, and there is adhesion to the stirrer. X: The filtration residue remains as a lump and there is considerable adhesion to the stirrer.

Uban 20SB: Completely butylated melamine resin (solid content 60%) manufactured by Nippon Cytec Co., Ltd., Sp = 9.7
Alpaste MH-8801: Aluminum bright pigment made by Asahi Kasei Kogyo Co., Ltd. (active ingredient 75%)
Degussa Carbon FW-200P: Carbon black pigment manufactured by Degussa Japan Co., Ltd. SN Clean Act 82: Sucrose polyether surfactant manufactured by San Nopco 2EHOH: 2-ethylhexyl alcohol manufactured by Mitsubishi Chemical Co., Ltd. EHG: Ethylene glycol manufactured by Nippon Emulsifier Co., Ltd. Mono 2-ethylhexyl ether SN thickener N-1: viscosity modifier made by San Nopco (solid content 25%)
Crosslinked resin particles: Viscosity modifier made by Nippon Paint Co., Ltd. (solid content 30%)
DMEA: 10 mass% dimethylethanolamine aqueous solution manufactured by Nippon Emulsifier Co., Ltd.

The present invention can provide an aqueous metallic base coating composition containing a surfactant containing a reaction product of a non-reducing disaccharide or trisaccharide and an alkylene oxide having 2 to 4 carbon atoms. By adding a surfactant to the aqueous metallic base coating composition, it is possible to suppress and / or prevent skinning and aggregation in the coating composition, and to form a multilayer coating film having an excellent appearance. .
The present invention also provides a method for forming a multi-layer coating film for sequentially forming an intermediate coating film, a metallic base coating film of the aqueous metallic base coating composition of the present invention, and a clear coating film on an object to be coated. Even in the course of the forming method, it is possible to suppress and / or prevent skinning and aggregation in the coating composition, and the formed multilayer coating film has an excellent appearance.

FIG. 1 is a schematic diagram of a circulation tank and a circulation system for a coating composition.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coating composition 2 Circulation tank 3 Stirring means 4 Circulation pump 5 Pipe 6 Coating means 7 Pipe 8 Filtration apparatus 9 Filtration apparatus S1 Coating composition upper surface S2 Coating composition surface S3 Coating composition lower surface

Claims (5)

A method for forming a multi-layer coating film in which an intermediate coating film, a metallic base coating film, and a clear coating film are sequentially formed on an object to be coated,
A water-based metallic base coating composition for forming the metallic base coating film,
Acrylic emulsion resin,
Melamine resin curing agent,
Luster pigment,
A surfactant containing a reaction product of a non-reducing disaccharide or trisaccharide (a1) and an alkylene oxide (a2) having 2 to 4 carbon atoms, and a solubility in water of 0.01 to 5.0% by mass An alcohol organic solvent having a boiling point of 160 to 200 ° C. and / or a glycol ether organic solvent having a solubility in water of 0.01 to 5.0% by mass and a boiling point of 205 to 240 ° C. 5 to 45% by mass based on the mass of resin solids in the paint, respectively
A method for forming a multilayer coating film, comprising:   The acrylic emulsion resin emulsion-polymerizes an α, β-ethylenically unsaturated monomer mixture having an acid value of 3 to 50 mgKOH / g containing 65% by mass or more of (meth) acrylic acid ester having 1 or 2 carbon atoms in the ester part. The method for forming a multilayer coating film according to claim 1, wherein the multilayer coating film is obtained.   The surfactant is produced by a reaction between 1 mol part of a non-reducing disaccharide or trisaccharide (a1) and 47 to 100 mol parts of an alkylene oxide (a2) having 2 to 4 carbon atoms, The method for forming a multilayer coating film according to claim 1 or 2.   The formation of the multilayer coating film according to any one of claims 1 to 3, wherein a mass ratio of the alcohol organic solvent / the glycol ether organic solvent is 1/1 to 3/1. Method.   The water-based metallic base coating composition used for the formation method of the multilayer coating film of any one of Claims 1-4.

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